St. Mary's County Multi-Jurisdictional Hazard Mitigation Plan

St. Mary’s County 

Multi-Jurisdictional 

Hazard Mitigation Plan 

May 27, 2011 

Department of Public Safety 

23090 Leonard Hall Drive 

Leonardtown, MD 20650

ST. MARY’S COUNTY 

BOARD OF COUNTY COMMISSIONERS’ MEETING 

Tuesday, September, 20, 2011 

Present: Commissioner President Francis Jack Russell 

Commissioner Lawrence D. Jarboe 

Commissioner Cynthia L. Jones 

Commissioner Daniel L. Morris 

Commissioner Todd B. Morgan 

John Savich, County Administrator 

Sharon Ferris (Recorder) 

DEPT OF PUBLIC SAFETY AND INFORMATION TECHNOLOGY: 

REQUEST ADOPTION OF MULTI JURISDICTION HAZARD 

MITIGATION PLAN 

Present: Bob Kelly, Director, Dept. of Public Works and Information 

Technology 

Gerald Gardiner, Emergency Management Manager, Dept. of Public 

Works and Information Technology 

Commissioner Morgan moved, seconded by Commissioner 

Jarboe, to adopt the updated St. Mary’s County Multi- 

Jurisdictional Hazard Mitigation Plan dated May 27, 2011. Motion 

carried 4-1. Commissioner Jones voted nay.

Table of Contents 

SMC Multi-jurisdictional Hazard Mitigation Plan 


CHAPTER 1 - INTRODUCTION...................................................................................................................1 

OVERVIEW ..................................................................................................................................................1 

PURPOSE....................................................................................................................................................1 

CONSISTENCY WITH STATE AND FEDERAL MITIGATION POLICIES....................................................................1 

ORGANIZATION OF THE PLAN........................................................................................................................2 

WATERSHEDS .............................................................................................................................................3 

POPULATION ...............................................................................................................................................3 

HOUSING ....................................................................................................................................................3 

INCOME AND POVERTY.................................................................................................................................4 

ECONOMY ...................................................................................................................................................4 

CLIMATE .....................................................................................................................................................4 

TRANSPORTATION .......................................................................................................................................4 

ANALYSIS OF DEVELOPMENT TRENDS...........................................................................................................5 

PLANNING PROCESS....................................................................................................................................6 

Step 1 - Organize Resources .............................................................................................................6 

Committee.........................................................................................................................................................6 

Step 2 - Assess Risks .........................................................................................................................7 

Step 3 - Develop a Mitigation Plan ....................................................................................................8 

Step 4 - Implement the Plan and Monitor Progress.........................................................................8 

PUBLIC INVOLVEMENT..................................................................................................................................8 

INTERAGENCY AND INTERGOVERNMENTAL COORDINATION.............................................................................9 

PARTICIPATING JURISDICTIONS ....................................................................................................................9 

INTEGRATION WITH EXISTING PLANS.............................................................................................................9 

Review of Existing Plans, Ordinances and Codes..............................................................................10 

Comprehensive Plan – Quality of Life in St. Mary’s County – A Strategy for the 21st Century10 

ST. MARY'S COUNTY COMPRESHENSIVE ZONING ORDINANCE.......................................................................14 

2009 INTERNATIONAL BUILDING AND RESIDENTIAL CODE ............................................................................19 

2010 COMPREHENSIVE LAND USE PLAN – TOWN OF LEONARDTOWN...........................................................19 

CHAPTER 2 – HAZARD IDENTIFICATION...............................................................................................21 

INTRODUCTION ..........................................................................................................................................21 

Step 1 - Hazard Identification...........................................................................................................21 

Step 2 - Hazard Profiles....................................................................................................................21 

HAZARD IDENTIFICATION ............................................................................................................................22 

Atmospheric Hazards .......................................................................................................................22 

Wildfire Hazards ................................................................................................................................22 

Hydrologic Hazards ..........................................................................................................................22 

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Geologic Hazards..............................................................................................................................22 

Thunderstorms..................................................................................................................................22 

Overview.........................................................................................................................................................22 

Historic Activity................................................................................................................................................22 

Lightning............................................................................................................................................23 

Overview.........................................................................................................................................................23 


Tornadoes..........................................................................................................................................24 

Overview.........................................................................................................................................................24 


Profile..............................................................................................................................................................27 

Hurricanes..........................................................................................................................................28 

Overview.........................................................................................................................................................28 


Hailstorms..........................................................................................................................................30 

Overview.........................................................................................................................................................30 


Profile..............................................................................................................................................................31 

Severe Winter Storms.......................................................................................................................31 

Overview.........................................................................................................................................................31 


Profile..............................................................................................................................................................33 

Extreme Summer Heat......................................................................................................................33 

Overview.........................................................................................................................................................33 

Profile..............................................................................................................................................................34 

HYDROLOGIC HAZARDS .............................................................................................................................34 

Flash Floods and Flooding ..............................................................................................................34 

Overview.........................................................................................................................................................34 


Profile..............................................................................................................................................................36 

Drought ..............................................................................................................................................37 

Overview.........................................................................................................................................................37 


Profile..............................................................................................................................................................39 

Coastal/Shoreline Erosion ...............................................................................................................39 

Overview.........................................................................................................................................................39 

History Activity ................................................................................................................................................39 

Profile..............................................................................................................................................................40 

Wildfires and Urban Interface Fires ................................................................................................41 

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Overview.........................................................................................................................................................41 


Profile..............................................................................................................................................................42 

GEOLOGIC HAZARDS .................................................................................................................................43 

Earthquakes.......................................................................................................................................43 

Overview.........................................................................................................................................................43 


Profile..............................................................................................................................................................44 

Landslides..........................................................................................................................................44 

Overview.........................................................................................................................................................44 


Profile..............................................................................................................................................................45 

Land Subsidence ..............................................................................................................................46 

Overview.........................................................................................................................................................46 


Profile..............................................................................................................................................................46 

SUMMARY OF EVENTS ...............................................................................................................................47 

CONCLUSIONS...........................................................................................................................................48 

CHAPTER 3 – VULNERABILITY ANALYSIS............................................................................................49 

OVERVIEW ................................................................................................................................................49 

Development Trends...........................................................................................................................49 

Population Trends ...............................................................................................................................49 

Land Use Trends.................................................................................................................................49 

Building Inventory................................................................................................................................50 

IMPACTS OF POPULATION, BUILDINGS, AND CRITICAL FACILITIES................................................................51 

Loss Estimation...................................................................................................................................52 

Description of Vulnerability..................................................................................................................52 

Mitigation Measures ............................................................................................................................53 


SEVERE STORMS.......................................................................................................................................54 



WILDFIRES ................................................................................................................................................54 




TORNADOES .............................................................................................................................................55 


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HURRICANE WINDS ...................................................................................................................................56 




FLOODING.................................................................................................................................................58 


Repetitive Loss Areas .........................................................................................................................59 

Critical Facilities in the Floodplain.......................................................................................................60 


Coastal/Shoreline Erosion...................................................................................................................62 



CHAPTER 4 – GOALS AND OBJECTIVES ..............................................................................................63 

INTRODUCTION ..........................................................................................................................................63 

MITIGATION GOALS AND OBJECTIVES .........................................................................................................63 

Flooding...............................................................................................................................................64 

Erosion ................................................................................................................................................64 

Wildfires...............................................................................................................................................64 

Wind ....................................................................................................................................................65 

Winter Storms......................................................................................................................................65 

Drought................................................................................................................................................65 

Critical Facilities ..................................................................................................................................65 

Public Awareness................................................................................................................................65 

Existing Plans and Ordinances ...........................................................................................................66 

Sustainable Development ...................................................................................................................66 

Building Construction ..........................................................................................................................66 

Communications .................................................................................................................................66 

Shelters ...............................................................................................................................................67 

CHAPTER 5 – MITIGATION STRATEGY..................................................................................................68 

RANGE OF MITIGATION INITIATIVES AND POLICIES .......................................................................................68 

Preventive Measures ..........................................................................................................................68 

Emergency Services ...........................................................................................................................68 

Property Protection .............................................................................................................................69 

Structural Projects...............................................................................................................................69 

Natural Resource Protection...............................................................................................................69 

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Public Information ...............................................................................................................................70 

MITIGATION ACTIONS.................................................................................................................................70 

Flooding...............................................................................................................................................70 

Erosion ................................................................................................................................................72 

Wildfires...............................................................................................................................................74 

Wind ....................................................................................................................................................75 

Winter Storms......................................................................................................................................76 

Drought................................................................................................................................................76 

Critical Facilities ..................................................................................................................................76 

Public Awareness................................................................................................................................77 

Existing Plans and Ordinances ...........................................................................................................78 

Sustainable Development ...................................................................................................................80 

Building Construction ..........................................................................................................................80 

Communications .................................................................................................................................81 

Shelters ...............................................................................................................................................82 

CHAPTER 6 – ACTION PLAN ....................................................... ERROR! BOOKMARK NOT DEFINED. 

IDENTIFICATION AND ANALYSIS OF HAZARD MITIGATION MEASURES.............................................................84 

TIMEFRAME...............................................................................................................................................84 

SCORING CRITERIA FOR MITIGATION ACTIONS ............................................................................................84 

HIGH PRIORITY PROJECTS (HIGHEST SCORES)............................................................................................90 

MONITORING, EVALUATING, AND UPDATING THE PLAN.................................................................................91 

HAZARD MITIGATION PLANNING COMMITTEE...............................................................................................91 

PUBLIC INVOLVEMENT................................................................................................................................91 

UPDATING THE PLAN .................................................................................................................................92 

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List of Figures and Tables 


List of Figures 

FIGURE 2.1 – MAP SHOWING SOUTHERN MARYLAND...............................................................................3 

FIGURE 2.2 – MARYLAND WATERSHEDS..................................................................................................3 

FIGURE 4.1 – RISK ASSESSMENT STEPS ............................................................................................... 21 

FIGURE 4.2 – FEMA’S DESIGN WIND SPEED FOR COMMUNITY SHELTERS .............................................. 27 

FIGURE 4.3 – HISTORY OF MARYLAND TORNADOES ............................................................................... 27 

FIGURE 4.4 – WIND ZONES IN THE UNITED STATES................................................................................ 30 

FIGURE 4.5 – HURRICANES WITHIN 65 MILES OF ST. MARY’S COUNTY SINCE 1886 ................................ 30 

FIGURE 4.6 – FIRE THREAT POTENTIAL IN MARYLAND COUNTIES............................................................ 42 

FIGURE 4.7 – FORESTED AREAS IN MARYLAND COUNTIES ..................................................................... 42 

FIGURE 4.8 – LANDSLIDE INCIDENCE/SUSCEPTIBILITY FOR THE NORTHEASTERN UNITED STATES............. 45 

FIGURE 4.9 – LANDSLIDE SUBSIDENCE IN THE UNITED STATES ............................................................... 46 

List of Tables 

TABLE 3.1 – ST. MARY’S COUNTY HAZARD MITIGATION PLANNING COMMITTEE.......................................7 

TABLE 3.1.A - PROJECTS FROM THE 2005 ST. MARY’S COUNTY HAZARD MITIGATION PLAN…….………….7 

TABLE 3.2 – INTERAGENCY COORDINATION ......................................................................................... 10 

TABLE 4.1 – TORNADO DAMAGE SCALE............................................................................................... 24 

TABLE 4.3 – TORNADO HISTORY ......................................................................................................... 25 

TABLE 4.4 – SAFFIR-SAMPSON SCALE AND TYPICAL DAMAGES ............................................................ 28 

TABLE 4.5 – WINTER WEATHER HISTORY ............................................................................................ 32 

TABLE 4.6 – HEAT DANGER CATEGORIES ............................................................................................ 33 

TABLE 4.7 – FLOODING VS. FLASH FLOODS – CAUSES ......................................................................... 34 

TABLE 4.8 – FLOOD PROBABILITY TERMS ............................................................................................ 35 

TABLE 4.9 – DROUGHT HISTORY ......................................................................................................... 38 

TABLE 4.10 – FIRE DANGER RATING DESCRIPTIONS .............................................................................. 41 

TABLE 4.11 – HISTORY OF FIRES IN ST. MARY’S COUNTY....................................................................... 41 

TABLE 4.12 – EARTHQUAKE MAGNITUDE AND INTENSITY SCALES ........................................................... 43 

TABLE 4.13 – MODIFIED MERCALLI INTENSITY SCALE AND PEAK GROUND ACCELERATION COMPARISON.. 43 

TABLE 4.14 – SUMMARY OF HAZARD EVENTS 1950 – 2003.................................................................... 47 

TABLE 4.15 – FREQUENCY OF OCCURRENCE......................................................................................... 48 

TABLE 4.16 – HAZARD PRIORITY........................................................................................................... 48 

TABLE 5.1 – POPULATION CHANGE ..................................................................................................... 49 

TABLE 5.2 – BUILDING COUNT AND EXPOSURE BY USE ........................................................................ 51 

TABLE 5.3 – BUILDING COUNT AND EXPOSURE BY TYPE....................................................................... 

TABLE 5.4 – CRITICAL FACILITIES COUNT AND EXPOSURE.................................................................... 51 

TABLE 5.5 – AGE OF HOUSING UNITS (BUILT BEFORE 1940 .................................................................. 53 

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List of Figures and Tables 


TABLE 5.6 – AGE OF HOUSING UNITS (BUILT BEFORE 1990) ................................................................. 53 

TABLE 5.7 – CRITICAL FACILITIES IN WILDFIRE HIGH RISK AREAS ......................................................... 54 

TABLE 5.8 – MANUFACTURED HOMES ................................................................................................. 55 

TABLE 5.9 – PROPERTIES IN THE 100-YEAR FLOODPLAIN..................................................................... 58 

TABLE 5.10 – REPETITIVE LOSS STRUCTURES....................................................................................... 60 

TABLE 5.11 – RATE OF EROSION........................................................................................................... 62 

TABLE 5.12 – PROPERTIES IN THE 100-YEAR EROSION ZONE ................................................................ 53 

Table 9.1 – MITIGATION ACTION TABLE .............................................................................................. 86 

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Chapter 1: Introduction 


CHAPTER 1 - INTRODUCTION 

Overview 

The Disaster Mitigation Act of 2000 (DMA 2000) was signed by the President on 30 October 

2000. The act requires state and local governments to prepare and adopt hazard mitigation 

plans as a condition for receiving Pre-Disaster Mitigation (PDM) grant assistance and Hazard 

Mitigation Grant Program (HMGP) assistance after November 1, 2004. The St. Mary’s County 

Multi-jurisdictional Hazard Mitigation Plan was first adopted in November of 2006 as a longrange 

strategic plan prepared to fulfill the requirements of DMA 2000 as administered by the 

Maryland Emergency Management Agency (MEMA) and the Federal Emergency Management 

Agency (FEMA) Region III. FEMA is requiring that all local jurisdictions update existing plans by 

March 30, 2011. 

Section 409 of the Robert T. Stafford Disaster Relief and Emergency Assistance Act (Public 

Law 93-288, as amended), Title 44 Code of Federal Regulations (CFR), as amended by Section 

102 of DMA 2000, provided the framework for State and local governments to evaluate and 

mitigate all hazards as a condition for receiving Federal disaster assistance. A major 

requirement of the law is the development of a local hazard mitigation plan. 

Purpose 

Hazard mitigation is any action taken to permanently reduce or eliminate long-term risks to 

people and their property from the effects of hazards. Natural hazards can take many forms: 

tornadoes, floods, hurricanes, severe storms, winter weather, droughts, landslides, or 

earthquakes resulting from natural phenomena. In order to better prepared to face these 

natural hazards, communities can plan for and implement mitigation techniques for almost any 

type of hazard that may threaten its people and property. 

This plan establishes an ongoing hazard mitigation planning program by: a) identifying and 

assessing potential natural hazards that may pose a threat to life and property; b) evaluating 

which local mitigation measures that should be undertaken; and c) outlining procedures for 

monitoring the implementation of mitigation strategies. The plan update provides guidance to 

St. Mary’s County officials on local mitigation activities that should be implemented over the next 

five-year planning cycle. It encourages activities that are most cost-effective and appropriate for 

mitigating the effects of all identified natural hazards. 

Consistency with Federal and State Mitigation Policies 

The goals, objectives and policies of this plan are expected to implement the National and State 

directives for mitigation of natural hazards through local strategies intended to: 

• Substantially increase public awareness of natural hazard risks and the measures 

available to create safer, more disaster-resistant communities; and 

• Significantly reduce the risk of loss of life, injuries, economic costs, and destruction of 

natural and cultural resources that result from natural hazards. 

FEMA has developed ten fundamental principles for the Nation’s mitigation strategies that 

likewise underlie the strategies of this plan: 

1. Risk reduction measures ensure long-term economic success for the community as a 

whole, rather than short-term benefits for special interests. 

2. Risk reduction measures for one natural hazard must be compatible with risk reduction 

measures for other natural hazards. 

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3. Risk reduction measures must be evaluated to achieve the best mix for a given location. 

4. Risk reduction measures for natural hazards must be compatible with risk reduction 

measures for technological hazards and visa versa. 

5. All mitigation is local. 

6. Disaster costs and the impacts of natural hazards can be reduced by emphasizing proactive 

mitigation before emergency response; both pre-disaster (preventive) and postdisaster 

(corrective) mitigation is needed. 

7. Hazard identification and risk assessment are the cornerstones of mitigation. 

8. Building new federal-state-local partnerships and public-private partnerships is the most 

effective means of implementing measures to reduce the impacts of natural hazards. 

9. Those who knowingly choose to assume greater risk must accept responsibility for that 

choice. 

10. Risk reduction measures for natural hazards must be compatible with the protection of 

natural and cultural resources. 

Organization of the Plan 

The next several chapters comprise the Hazard Mitigation Plan. 

Chapter 1 begins with an introduction to the plan including information on the purpose, 

organization of the plan, and demographics pertaining to St. Mary’s County. In addition, the 

planning process is outlined regarding how program changes and information updates were 

made with assistance from the Hazard Mitigation Planning Committee and state and federal 

assisting agencies. 

Chapter 2 encompasses the natural hazard risk assessment and hazard identification which 

identifies and profiles each of the natural hazards that could affect St. Mary’s County. 

Chapter 3 identifies the county’s assets and provides a vulnerability analysis to assess the 

potential impacts of the identified natural hazards on the people, buildings, and infrastructure in 

St. Mary’s County. 

Chapter 4 contains the goals and objectives of the plan. 

Chapter 5 includes the mitigation strategy, which identifies each mitigation measure, the lead 

implementation agencies or departments, approximate cost, and potential funding sources for 

implementation of each strategy. 

Chapter 6 outlines the action plan with procedures and details on how St. Mary’s County and 

the Town of Leonardtown will maintain the mitigation plan to keep the data current and update 

the progress on the mitigation strategy. 

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COUNTY PROFILE 

Location 

St. Mary’s County is located 

approximately 60 miles southeast of 

Washington, D.C. in southern Maryland 

(see Figure 2.1). St. Mary’s County is a 

peninsula bordered by the Wicomico 

River on the west, the Potomac River on 

the south, the Chesapeake Bay on the 

east, and the Patuxent River on the 

northeast. The Thomas Johnson 

Bridge connects the norther shore of the 

Patuxent River at Solomon's Island in 

Calvert County with its southern shore in 

St. Mary's County, MD. The total area of 

the county is approximately 361 square 

miles with a density of 280 persons per 

square mile. The county has one 

incorporated town, Leonardtown. 

Watersheds 

Figure 2.1 - Map Showing Southern Maryland 

St. Mary’s County is encompassed by two watersheds 6-digit (see Figure 2.2), the Lower 

Potomac (shown in yellow) and the Patuxent Watershed (shown in purple). 

Population 

Figure 2.2 - Maryland Watersheds 

In 2010, Maryland's population was 5,773,552, 

according to the US Census Bureau. The 

Maryland Department of Planning 2010 

estimate for the populatin of St Mary’s County 

was 105,400. From 2000 to 2010, Maryland’s 

population grew approximately 9% percent, a gain of 477,514. Over the same period St. Mary’s 

population grew 22%, a gain of 19,189 people. St. Mary’s County is among the fastest growing 

counties in the State of Maryland. According to the Maryland Department of Planning’s 

February 2009 estimates, by the year 2030, St. Mary’s County will have an estimated 159,600 

residents. 

Housing 

As of 2010, there were 35,840 housing units in St. Mary’s County. Of these, approximately 13.5 

percent of the units are multi-unit structures. The average price of a home in 2007 was 

approximately $200,00, which increased to the average price of $337,500 in 2007. 

3



Income and Poverty 

The total labor force in 2009 was 51,343 with an unemployment rate of 5.7 by October 2010 the 

labor foce was 52,475 and an unemployment rate of 6.2 percent. St. Mary’s per capita income 

in 2008 was reported as $37,748, and St. Mary’s County was ranked 14 th of the Maryland 

counties for per capita personal income behind the there Southern Maryland counties (Calvert, 

10 th and Charles, 12 th ). 

Economy 

St. Mary’s County is home to the U.S. Naval Air Systems Command and the Naval Air Warfare 

Center Aircraft Division and over 230 high-tech defense contractors. The county has emerged 

as a world-class center for aviation and avionics research, development, and testing. Due 

primarily to the influx of technical jobs resulting from the consolidation of several Navy activities, 

the County’s increase in median household income during the past decade has been the largest 

in the State. St Mary's County’s 1,990 businesses employ 28,200 workers; an estimated 40 

percent of these businesses have 100 or more workers. Businesses include many defense 

contractors, the Lundeberg School of Seamanship, St. Mary's Hospital, College of Southern 

Maryland and St. Mary's College of Maryland.. The county is also home to a newly designated 

State Enterprise Zone. 

Climate 

St. Mary’s County’s climate is generally mild. There are four distinct seasons with spring and 

fall being particularly pleasant, with low humidity and mild temperatures. The average annual 

winter temperature is 37.4 degrees Fahrenheit and the summers can be hazy, hot, and humid 

with an average summer temperature of 74.4 degrees Fahrenheit. Afternoon thunderstorms are 

also a common occurrence in the summer months. The average annual rainfall is 47.5 inches 

and the average annual snowfall is 17.8 inches. 

Future variability in climate is predicted and over time will likely influence the frequency and 

severity of the occurrences of natural hazards for the county. The Maryland Climate Action Plan 

(released August 27, 2008) advises that for Maryland generally 

“Average yearly temperatures are expected to increase by 3-6° F (2-4° C) in the 

winter and by 4-8° F (2.2-4.4° C) in the summer…(US EPA 1998; IPCC 2007b; 

MCCC – STWG 2008). Precipitation will increase by 20 per cent in Maryland with 

more rainfall in the winter and less in the spring (US EPA 1997; Fisher et al. 

1997; IPCC 2007b)… Major coastal storms will be more intense and more 

frequent (EPA 1998, IPCC 2007b). By century’s end, 5-15 percent more latewinter 

storms may develop in the Northeast as storm systems move further north 

in response to warmer ocean surface temperatures (Frumhoff et al. 2007). 

Perhaps most significant to Maryland, sea level rise will increase by .6-1.22 m 

(24-48 inches) over the next century along the coast (MCCC 2008; MDNR 2008; 

IPCC 2007b).” 

Transportation 

St. Mary’s County is a peninsula which is itself divided into numerous peninsulas by rivers and 

creeks. Minor state and local roads generally follow ridgelines and are connected to the 

county’s four principal state roads—MD 5, MD 235, MD 4, and MD 234. Maryland Route 5 

(MD5) is a four- lane highway from Charles County to MD 235 (Three Notch Road). At its 

junction with 235, Route 5 bears right and continues as a two lane road south to Leonardtown 

(the county seat) and then runs along the length of the county through Ridge to Point Lookout. 

4



From the junction with MD5, Three Notch Road continues as a four-lane road southeast to 

California, expands to six lanes through Lexington Park (the principal growth center for the 

county) and drops to two lanes south of Lexington park and continues south east ending at 

Route 5 in Ridge. Route 4 is four-lane highway in Calvert County which drops to a 2-lane road 

at the Governor Thomas Johnson Bridge over the Patuxent River, continues across Three 

Notch Road at California and ends at MD 5 just south of Leonardtown. Route 234 runs from US 

310 in eastern Charles County ending at Route 5 just north of Leonardtown. 

The population increase in the county has resulted in increased traffic volumes and highwayrelated 

commercial activities. Increased volume on the four principal state roads makes 

entering, exiting and crossing the highways from side roads increasingly difficult. The lack of 

interconnections and alternative north-south routes increase problems such as congestion and 

delays particularly along the Three Notch Road (MD 235) corridor from Hollywood through 

Lexington Park. In response to this congestion, projects such as widening the addition of turn 

lanes to Three Notch Road through California and Lexington Park, widening of Great Mills and 

Chancellor’s Run Roads in Lexington Park, construction of sections of FDR Boulevard which 

when complete will parallel Three Notch Road in Lexington Park, requirements for road 

interconnection between parcels, and provision of additional traffic lights and median separation 

to expedite the flow of traffic and reduce traffic accidents have been completed or are in 

progress. 

Analysis of Development Trends 

St. Mary’s County has a total land area of 231,280 acres. Analysis provided in the 2010 

Comprehensive Plan finds that more than half of this land (51 percent) is forested, with 

agriculture accounting for 26 percent. In 2007 the Census of Agriculture counted 68,648 acres 

of land in farms in St. Mary’s County, which was a slight increase from 68,153 acres in 2002 but 

which was still down from 71,920 acres in 1997. Developed land accounts for nearly 21 percent 

of the total land area, which is a dramatic increase of 30.4 percent from 1997 to 2002. In 

addition, low-density residential development (less than 2 units per acre) is the most rapidly 

growing type of development, up by 40% from 1997 to 2002. 

In the county’s Comprehensive Plan, Lexington Park and Leonardtown are designated 

development districts which are to be the primary growth centers; Charlotte Hall, New Market, 

Mechanicsville, Hollywood, and Piney Point are designated as town centers (the County’s 

secondary growth centers); and Callaway, Chaptico, Clements, Loveville, Ridge, St. Inigoes, 

and Valley Lee are village centers (tertiary growth centers). 

5


PLANNING PROCESS 


In June 2004, St. Mary’s County Department of Public Safety received a grant from the Maryland 

Emergency Management Agency (MEMA) to prepare a DMA 2000 complaint hazard mitigation plan for 

the County and the Town of Leonardtown. The County’s Emergency Management Agency subsequently 

contracted with Greenhorne & O'Mara, Inc. (G&O) from Greenbelt, Maryland, to facilitate the planning 

process and prepare the Plan. The planning team members consisted of key representatives from 

various County agencies, the Town of Leonardtown, and other organizations. The St. Mary’s County 

Multi-jurisdictional Hazard Mitigation Plan was completed in November 2006 by Greenhorne & O’Mara 

and adopted by the St. Mary’s County Board of County Commissioners and approved by the Federal 

Emergency Management Agency (FEMA). In 2009, the requirement was set forth by FEMA for St. 

Mary’s County to update the existing plan by March 31st, 2011. The Department of Public Safety 

convened a new planning team in June of 2009, consisting of relevant disciplines from within St. Mary’s 

County that have vested interest in Hazard Mitigation Projects. The team decided that all changes to the 

current Multi-jurisdictional Hazard Mitigation Plan would be completed by members of the team with 

assistance from cooperating state agencies. 

The Planning Team attended a kick-off meeting on June 29, 2009 and formally established the Hazard 

Mitigation Planning Committee (HMPC). and Five committee meetings were held between June 2009 

and December 2010. Documentation of these meetings in the form of sign-in sheets, agendas, and 

minutes are included in Appendix A. 

The HMPC was actively involved in identifying hazards within the county, reviewing the county’s 

vulnerabilities to natural hazards, and recommending mitigation measures to reduce and prevent 

potential damage from these hazards. The HMPC then worked together to select the most appropriate 

and feasible mitigation measures. 

Planning Update Process 

The planning process involved four basic steps: organizing resources; assessing risks; developing a 

mitigation plan; and implementing the plan and monitoring progress. 

Step 1 - Organize Resources 

The first step of the hazard mitigation planning process was for the county to organize their resources 

and ensure that they had adequate technical assistance and expertise to form a hazard mitigation 

committee. The committee included representatives from key county agencies such as Land Use and 

Growth Management, Emergency Management, Geographic Information Systems (GIS), and Public 

Works and representatives from the Town of Leonardtown. Technical support for the planning effort was 

provided by engineers, planners, and floodplain managers from within St. Mary’s County and Maryland 

State government agencies. 

Committee 

Select members from the Town of Leonardtown and the County departments were invited to be on the 

HMPC, which was tasked with conducting a DMA 2000 compliant hazard mitigation planning process to 

update the current hazard mitigation plan. Table 3.1 includes the members of the committee and the 

agencies they represent: 

6


Table 3.1 – St. Mary’s County Hazard Mitigation Planning Committee 

Name 

Bob Kelly 

Gerald Gardiner 

Gerald Burandt 

Mark Stancliff 

Michael Sullivan 

Jenn Ballard 

Mike W yant 

Stewart Dement 

Adam Knight 

Tony W heatley 

Adam Knight 

Hans W elch 

George Erichsen 

Kathy Arnold 

Sue Veith 

Agency 

Direcctor, St. Mary's County Department of Public Safety 

Emergency Management Manager, St. Marys County 

NAS Patuxent River Emergency Management 

St. Mary's County Information Technology 

Metropolitian Commission 

St. Mary's County Land Use & Growth Management 

St. Mary's County Public Schools 

State Highway Administration 


Town of Leonardtown 


Department of Economic and Community Development 

St. Mary's County Department of Public W orks & Transportation 

St. Mary's County Risk Management 



Community, county, state, and 

federal resources were 

identified and the appropriate 

agencies were contacted to collect 

pertinent inventory information. 

Policy and regulatory information 

from each of the communities and 

the county was collected. This 

included comprehensive plans, 

zoning and subdivision ordinances, 

and building codes. In addition, 

information was collected regarding 

natural hazards, including past 

occurrences and projected 

frequencies of future occurrence, the 

anticipated risk, where available. 

Table 3.1.a – Projects from the 2005 St. Mary’s County Hazard Mitigation Plan Completed 

Information was collected from public 

works, planning, emergency 

management, and GIS departments. 

Several State agencies were 

contacted including the MEMA, 

Maryland Department of Natural Resources (DNR), the Department of Homeland Security/FEMA, 

Maryland Department of Planning, and the Maryland Department of the Environment (MDE), to inform 

them of the planning effort and to collect pertinent information. 

Step 2 - Assess Risks 

The next step in the planning process was to update the hazard identification and vulnerability 

assessment for the entire county. This involved reviewing the projects identified in the March 2005 plan. 

The following projects have been completed: 

2005 Project No. Project Description Reason for 

Removal 

2 Complete proposed mitigation project at Piney Point Complete 

3 Complete proposed mitigation project at Mansfield Complete 

12 Identify, map and assess all mobile homes in the county & determine the most 

appropriate mitigation alternatives to reduce wind & flood damage 

14 Determine appropriate areas where overhead wires may be buried underground. 

Protect utilities, including underground pipelines, so that they may not be impacted 

and interrupted from exposures to hazards 

15 Identify areas with trees and determined if they need to be cut down, trimmed, etc., 

to reduce vulnerability and risk of falling during or after a high wind event. 

Complete 

Complete 

Complete 

20 Identify isolated populations within the county and create a database. Create a Complete 

separate database that identifies concentrations of dependent population (elerdly, 

disabled and children) 

21 Identify means to ensure that local radio stations are able to continuously 

Complete 

broadcast during power outages 

26 Revise and update the existing code and bring it up to standard 2003 codes. Complete 

27 Develop a Citizens Emergency Response Team (CERT) program for the county, 

identify, designate and train coordinators in various neighborhoods on CPR and 

first aid 

30 Coordinate with the Naval Air Station to use their AM radio station to make 

broadcast before, during and after 

Complete 

Complete 

7



32 Evaluate the need to develop local ordinances to require community storm shelters 

with sizable mobile home parks and subdivisions and in all new public buildings 

(schools, libraries and communities centers) 

29 Identify critical facilities that do not currently have NOAA weather radios and 

increase the number of NOAA Weather Alert radios in public places across the 

county 

Complete 

Complete 

The 2005 projects have been incorporated into this updated plan. When the committee had discussion it 

was agreed upon to keep these and some wording has been updated. 

This involved analyzing the county’s greatest hazard threats and determining its most significant 

vulnerabilities with respect to natural hazards and hazardous materials. The hazard identification and 

vulnerability assessment performed in large part using GIS data from the county, HAZUS-MH (GIS 

based loss estimation software) and other county sources. At the first HMPC Meeting held on 29 June 

2009, an overview of the planning process was presented to the committee to review the identified 

hazards and areas vulnerable to various hazards and to discuss mitigation measures which should be 

applied. 

Step 3 - Develop a Mitigation Plan 

The next step was to assess the mitigation capabilities of the county and the Town of Leonardtown. A 

capability assessment was performed whereby the existing programs and policies addressing natural 

hazards were reviewed. A thorough analysis of the adequacy of existing measures was performed, and 

potential changes and improvements were identified. The committee reviewed the capability assessment 

at the second HMPC Meeting held on 3 September 2009. At this meeting, the Committee worked to 

identify goals and objectives for countywide mitigation efforts. These goals represent the county’s and 

communities’ vision for disaster resistance. 

At the third meeting held on 12 December 2009, issues that could affect hazard event-related damage in 

the county were considered by the HMPC and the development of new and revised mitigation measures 

began. 

These actions were further refined at the fourth committee meeting on 3 March 2010. The committee 

also helped draft an action plan that specifies recommended projects, who is responsible for 

implementing these projects, and when they are to be completed. The projects were categorized and 

prioritized. In the months following this meeting, the Department of Public Safety worked to revise the 

existing plan to incorporate all of the gathered information and to update the vulnerability analysis portion 

of the plan using data and information gathered from multiple sources. 

It should be noted that this plan recommends mitigation measures that should be pursued and 

implemented after funds are obtained by local means, including capital projects or by potential grant 

funding. Implementation of these recommendations depends on adoption of this plan by the St. Mary’s 

County Board of County Commissioners, the Town of Leonardtown and the cooperation and support of 

the offices and contacts designated as being responsible for each action item. 

Step 4 - Implement the Plan and Monitor Progress 

The County will continue to implement the plan and perform periodic reviews and revisions through ongoing 

HMPC reviews and revisions. The review and revision process will be attached to the state-wide 

planning efforts which are outlined by the Maryland Emergency Management Agency and follow that 

update process. The Committee will meet annually to review the plan and will also hold public meetings 

to solicit citizen input. 

Public Involvement 

The public involvement element of the planning process involved one public meeting where information 

was presented to the public on 8 December 2010 at the Chesapeake Building in the St. Mary’s County 

Board of County Commissioner’s Board Room. The purpose of this meeting was to educate the public 

on the planning process and the plans intent to identify steps the community could take to make the 

8



community more disaster-resistant. Attendees were encouraged to provide input as to what type of 

mitigation measures they wanted the county and communities to pursue. Following approval from FEMA 

and MEMA this plan will be brought before the St. Mary’s County Board of County Commissioners for 

formal plan adoption at the local level. 

Interagency and Intergovernmental Coordination 

In addition to the HMPC members listed above, various local, state, and federal agencies were contacted 

to provided data, input and cooperation for the St. Mary’s County Hazard Mitigation Plan. These 

agencies and their reason for contact are shown in Table 3.2. 

Table 3.2 – Interagency Coordination 

Agency 

Maryland 

Department of the 

Environment 

Maryland 

Department of 

Natural Resources 

Maryland Geological 

Survey 

Maryland 

Emergency 

Management 

Agency 

Maryland 

Department of 

Planning 

National Weather 

Service 

Method of 

Contact 

Telephone 

Interview and 

e-mail 

Telephone 

Interview and 

e-mail 

Telephone 

and e-mail 

E-mail and 

internet 

website 

E-mail and 

internet 

website 

E-mail and 

internet 

Reason for 

Contact 

Repetitive loss 

information 

Shore erosion 

data 

Shore erosion 

data and St. 

Mary's Dam 

information 

Risk assessment 

data and disaster 

history 

Demographics 

and MD Property 

View Data 

Severe Weather 

History 

MEMA will serve as the state review agency and will 

initiate the state clearinghouse process which routes the 

final plan to all pertinent Maryland State agencies for 

review and comment. The following agencies in Table 

3.2 received a draft of the plan for review and comment: 

Participating Jurisdictions 

The Town of Leonardtown participated by direct 

representation on the Planning Team. In addition, they 

participated through the following means: 

• Responding to questionnaires 

• Attending committee meetings 

• Reviewing draft plan sections 

• Offering comment on the draft plan 

• Adopting final plan through formal resolution 

Integration with Existing Plans 

website 

The St. Mary’s County Multi-jurisdictional Hazard 

Mitigation Plan will be integrated into the existing adopted County Emergency Operations Plan, last 

updated in 2010 and will be administered through the St. Mary’s County Department of Public Safety and 

the St. Mary’s County Comprehensive Plan last updated in 2010 through the Department of Land Use 

and Growth Management. The requirements of the Hazard Mitigation Plan will be incorporated into future 

amendments of zoning ordinance, building code, and comprehensive plan documents. The Town of 

Leonardtown will also incorporate the requirements of this mitigation plan into future amendments of its 

planning documents. 

St. Mary’s County has a number of resources that it can access to implement hazard mitigation 

initiatives. These resources include both private and public assets at the local, state, and federal levels. 

A detailed “Hazard Mitigation Capabilities Assessment Questionnaire” was prepared and distributed to 

the HMPC for input. The questionnaire was designed to assess the community’s ability to reduce future 

losses from hazards like floods, winter storms, etc., through its various policies and programs. The intent 

of the capability assessment was to provide an inventory of existing policies, programs, practices, and 

operational responsibilities that have or may have a major role in helping the community in its overall 

efforts to mitigate hazards. The results of the questionnaire are integral to the development of the 

mitigation strategy of this plan. 

9



The questionnaire covered several different agencies within the jurisdictions, particularly the County 

agencies. These agencies or positions included the Department of Land Use and Growth Management; 

the Department of Public Works; the Floodplain Manager and Engineering. 

Two of the most important capabilities that the county and municipality utilize are the floodplain 

management ordinances and building codes. Through administration of floodplain ordinances, 

jurisdictions can ensure that all new construction or substantial improvements to existing structures 

located in the 100-year floodplain are built with first-floor elevations above base flood elevation. Building 

codes are important in mitigation; codes regionally developed consider the hazards present within that 

region of the country. Consequently, structures that are built to applicable codes are inherently resistant 

to many hazards like strong winds, floods, and earthquakes and can help mitigate regional hazards such 

as drought. 

As part of the assessment of the St. Mary’s County’s mitigation capabilities, a review of enabling 

statutes, ordinances, planning documents, and building codes was conducted. Some portions of these 

regulations were very strong in relation to mitigation capabilities, others had areas that would enhance 

the county’s mitigation efforts if particular sections were strengthened or revised. Commentary on 

recommendation to strengthen these existing plans and ordinances is provided in italics. 

Review of Existing Plans, Ordinances and Codes 

Comprehensive Plan–Quality of Life in St. Mary’s County–A Strategy for the 21st Century 

The current Comprehensive Plan, effective in April 2010, is adopted as a guide for County actions 

regarding many aspects of community life and development—growth and land use; resource 

protection;efficient use and protection of water resources; housing; economic development; community 

facilities; transportation; and human services. The Comprehensive Plan establishes goals, objectives and 

policies that support the Community Vision for the County to “preserve and enhance the quality of 

life….foster economic growth by focusing and managing growth; by protecting the rural character and 

economy of the countryside, by nurturing the shoreline and adjacent waters; and by preserving and 

capitalizing on the natural resources and the historical quality of the county.” The 2010 Comprehensive 

Plan incorporated many related functional plans, including the Hazard Mitigation Plan. With regard to 

hazard mitigation, the 2010 Comprehensive Plan contains language relevant to or specifically intended 

to strengthen and support improved hazard mitigation planning. Relevant goals, policies, objectives are 

excerpted below and discussion is provided for sections which pertain to Hazard Mitigation. Where 

additional attention to hazard mitigation appears necessary to ensure hazard mitigation is taken into 

account in implementation or future Comprehensive Plan updates, comments have been included in 

italics. 

41.1.A. Objective: Designate growth areas sized to accommodate the needs of the projected 

2030 population of the County. Target a majority of new residential development in 

development districts, town centers and village centers. 

viii. 

Policy: Balance development goals with environmental protection and 

enhancement of the value of waterfront as a resource for recreation and water 

dependent facilities. 

Comment: The issues of flood hazards associated with water bodies should be addressed. 

4.1.1.C. Objective: Focus development in town centers. 

x. Encourage installation of underground services to minimize visual impacts of 

overhead utility lines. 

Comment: The concern regarding power and other types of service which can be disrupted by 

natural disasters that damage overhead lines must be addressed to support enforcement of 

burying of utility lines. 

4.1.2.B. Objective: Foster and enhance sense of community and remedy negative conditions in 

existing developed areas. 

10

Chapter 1: Introduction SMC Multi-jurisdictional Hazard Mitigation Plan 

i.a. Landscape provisions for redevelopment and new development. 

Comment: Ensure that consideration of water conservation and fire prevention are incorporated 

into future plans regarding landscaping. 

4.4.1. Goal: Direct growth in rural areas to existing population centers to protect resource 

areas. 

4.4.1.A. Objective: Limit growth in rural areas to preserve open space and to protect and 

promote agriculture and forestry. 

i. Conserve the land and water resource base that is necessary to maintain and 

support the preferred and uses of agriculture, forestry, fisheries activities and 

aquaculture, and to preserve natural environments (wetlands, forests, abandoned 

fields, beaches and shorelines). 

Comment: This area is directly linked to hazard mitigation because the protection of open spaces, 

particularly wetlands, floodplains and forests, can provide natural barriers, mitigate volume and 

velocity of flooding, and assure that peoples are not living in high risk areas which are particularly 

vulnerable to natural disasters prevalent in the County.. 

In section 5.1. Introduction the plan discusses the importance of sensitive areas protection and 

links those to environmental services they provide including services for eliminating and 

mitigating hazards. 

… Sensitive areas provide ecosystem and economically valuable environmental 

services which cannot be inexpensively or effectively replaced. … Streams and 

their buffers provide the primary transport system for storm water and, if managed 

poorly, they become primary conduits to transport pollution – heavy metals, oils, 

chemicals, trash from urbanized areas, nutrients, bacteria, pesticides and 

herbicides from farms and lawns – into the Bay. When managed well, streams 

and their buffers capture, reduce, and process pollutants, provide water supply 

functions, and provide spawning areas for recreational and commercial fish stock. 

…Wetlands protect water quality, infiltrate, slow and filter runoff, help control and 

reduce pollution and erosion. Floodplains and wetlands are important in the 

maintenance of groundwater supplies and water purification. … Marshes, fringe 

wetlands and submerged grass beds stabilize sediments and dampen impacts 

from storms to reduce loss of upland property, and maintain water clarity. …Forest 

conservation is important for protecting water supply, aiding recharge of aquifers, 

and infiltrating storm water runoff. Assuring the continued viability of sensitive 

areas to provide their ecosystem and environmental service functions and for their 

contributions to the beauty and diversity of the landscape is also an important goal 

of this plan. 

In Section 5.2 Measures of Success for Conservation of Sensitive Areas the Comprehensive 

Plan discusses links between specific ordinance provisions for sensitive areas protection and 

plan goals including resources and goals that are important in hazard mitigation stating “The 

county maintains Geographic Information Systems (GIS) data layers that show the extent of the 

resources required to be protected under current regulations. That data was used to estimate the 

number of acres of these resources.” Many of the resources mapped in GIS are relevant to 

hazard mitigation planning including: 

• 100-foot Buffer for all perennial and for intermittent streams in the Critical Area (50,220 

acres) These are regulated as drainage way buffers in the Floodplain ordinance and 

provide safe conveyance for storm water during storms. 

11



• Conservation of 100 year floodplains and a surrounding 50 foot buffer (21,130 acres) 

Floodplains are preserved from disturbances. The 50 buffer established assures that 

encroachment from new development is minimized and provides extra protection from 

flood events. 

• Conservation of the 100 foot Critical Area Buffer (7,250 acres) The Critical Area Buffer is 

required to be established and maintained in dense natural vegetation to provide a 

stabilized shoreline as well as provide a natural barrier to wind and wave action. 

• Highly erodible soils (49,221 acres total, of which only the areas within 300 feet of water 

features and wetlands are required by this plan to have mandatory protection for a net 

protection area of 35,262 acres). These soils are prone to erosion, often unstable, and, 

prone to undermining and collapse due to movement of surface and groundwater. 

Identifying the soils and keeping development off of them reduces the risk of damage to 

buildings, infrastructure, and downstream sediment impacts. 

Section 5.3.4. discusses the need to implement strategies, policies and programs, and to 

provided funding for resource conservation of inherently valuable sensitive areas which provide 

ecosystem functions (mitigation of flooding, filtering for improvement of water quality, economic 

value (farm, fishery, forest, mineral products, recreational use) and reduction in service costs 

(reduced storm water management, maintained water supply.) The County’s primary mechanism 

to maintain these values is via regulations that require environmentally sensitive designs and 

place the responsibility for protection, conservation and stewardship, and mitigation for losses 

predominately on the landowner in exchange for the value added from development. ‘ 

The strongest Comprehensive Plan language supporting hazard mitigation planning is found in 

Section 5.3.5 regarding the planning vision for Quality of life and sustainability. This section 

discusses the need for stewardship and for maintaining, enhancing and avoiding disruption of the 

natural functions of wetlands, forests, and floodplains, and preventing development impacts that 

overwhelm the service capacity provided by natural systems.” Sustainable communities 

“maintain a high quality of life enriched by the benefits of the environment and as free as possible 

from the disruptions associated with losses and damages which increase risks of environmental 

hazards and man-made disasters. To assure that St. Mary’s County develops in a sustainable 

manner that balances growth and resource protection, it is necessary to assure that hazard 

avoidance and mitigation is integrated into the planning and development process. Another 

component is assuring that development is located to reduce exposure to risk associated with 

identified hazards, is constructed to minimize damage and disruptions from unavoidable risks and 

that development occurs in a manner that will not result in creating or increasing community 

exposure to hazards and adverse impacts. Of the twelve hazards identified as posing significant 

risks to the County, the highest risks are associated with 1) coastal/shoreline erosion, 2) extreme 

weather due to severe winter storms, 3) flood, 4) high wind due to hurricanes, 5) high wind due to 

tornado, 6) thunderstorm and lighting, and 7) wildfire. Also of concern are moderate risks 

associated with 8) hailstorms, 9) extreme summer heat and 10) drought. Risk of 11) earthquakes 

is considered to be low but the localized risk of 12) land failure of the steeps slopes and cliffs, 

particularly in the Patuxent watershed is of increasing concern. 

Section 5.5 discusses protection and management of riparian resource areas—riverbanks, 

streams and their buffers. 

5.5. Goal: Protect riverbanks, streams and their buffers from the adverse impacts of 

development and human activity. 

5.5.1.A. Objective: Preserve, protect and restore the natural ecosystems and functions of rivers, 

streams, and their buffers and adjacent hydric and erodible soils. 

Comment: Riparian areas absorb and slow runoff and can provide safe conveyance and holding 

areas for floodwaters. Adverse impacts of human activity include removal of forest cover and 

increases in impervious cover both of which reduce infiltration of storm water and increase runoff 

12



volume and velocities. Increased volume and velocity promotes flash flooding and channel 

erosion that disconnects streams from their floodplains causing more sudden and more 

dangerous downstream flood events with deeper and faster flood waters. 

Section 5.7 discusses protection and management of tidal floodplains, non-tidal floodplains and 

the floodway protection to prevent the adverse impacts of development and human activity. 

Objective 5.7.1.A. “Preserve, protect and restore the natural environment and beneficial 

functions of floodplains” contains a number of policies directly pertaining to reduction of hazard 

including 5.7.1.A.i. “Limit and manage development activity in the 100-year floodplain to reduce 

vulnerability and flood hazards; 5.7.1.A.ii. Minimize the disturbance to vegetation in the floodplain 

Specific Actions to implement these policies include: 

• For all 100 year floodplain areas, continue to enforce existing regulations that require 

buffers at least 50 foot wide measured from the edge of the floodplain (determined by 

elevation). 

• Avoid disturbances to floodplains and their buffers to the maximum extent possible by 

requiring floodplain easements, continuing to prohibit development in the floodplain when 

alternative locations exist on a development site, continuing to prohibit creation of new 

development lots within the floodplain; prohibiting new fill in the floodplain, and keeping 

storm water ponds and structures out of the floodplain. 

• Maintain community eligibility for participation in the National Floodplain Insurance 

Program (NFIP) by assuring that development activities are conducted and structures are 

constructed or expanded in a manner that fully complies with (NFIP) criteria. 

• Seek to lower flood insurance rates through participation in the Community Rating System 

(CRS) which is a Federal Emergency Management Agency (FEMA) program that 

decreased flood insurance rates for residents in communities with effective hazard 

mitigation strategies. 

• Develop a comprehensive “No Adverse Impact” program for floodplain management. 

Objective 5.7.1.B. “Plan for and accommodate land use changes and impacts that are 

anticipated due to climate variability and projections for sea level rise.” contains a number of 

policies directly pertaining to identification and mitigation of hazard impacts including: 

• Map vulnerable lands, infrastructures and facilities. 

• Strengthen building codes and require use of appropriate construction and management 

techniques for new infrastructure and structures in vulnerable areas focusing particularly 

on elevation of buildings, foundation design, use of materials that can withstand periodic 

flooding, resistance to debris impact, resistance to wind and wave action, establish 

standards for abandonment and removal of impacted structures. 

• Include risk assessment and vulnerability when making public investments in 

infrastructure investments, to incorporate responses to threats into placement decisions 

and designs for new facilities, and for upgrade and replacement of threatened facilities. 

Also include in land conservation to reduce threats and preserve options for retreat of 

natural resources. 

St Mary’s County Comprehensive Zoning Ordinance 

The current Comprehensive Zoning Ordinance, effective effect on September 14, 2010, is the primary 

tool for regulating how development or redevelopment is accomplished in the County. It is also one of 

the tools for implementing the goals, objective, policies and actions recommended in the Comprehensive 

Plan. The Chapters listed and briefly discussed below contain provisions that are relevant to a hazard 

mitigation plan 

13



Chapter 41 Chesapeake Bay Critical Area (IDA, LDA, RCA) establishes overlay district regulations 

that apply to all water of and lands under the Chesapeake Bay and its tributaries to the head of tide, all 

State and private wetlands, and all land and water areas within 1,000 feet beyond the landward 

boundaries of State or private wetlands and the heads of tide. The regulations apply to limit density and 

impervious cover, assure adequate water quality and quantity measures are implemented to manage 

runoff, measures to assure no net loss of forest cover, and to establish criteria for resource protection. 

Particular attention is given to prohibiting development and disturbances in a “Critical Area Buffer” at 

least 100 feet landward of mean high water or the top of stream banks and expanded for sensitive 

resources (non-tidal wetlands, hydric and highly erodible soils and steep slopes). The regulations have 

the effect of reducing the overall amount of development in close proximity or tidal waters and tributary 

stream and reducing the impacts of development that does occur. In addition to significant habitat 

benefits provided the regulations also reduce risk to hazards such as storm surge and tidal flooding, and 

damage and property loss due to shoreline erosion. 

Chapter 43 Air Installations Compatible Use Zone (AICUZ) establishes land use development 

standards and requirements intended to minimize exposure to aircraft noise, minimize risks to public 

safety, and minimize hazards to aviators and those employed or residing in proximity to public aviation 

facilities. Each overlay establishes a hierarchy of sub-districts with development and use restrictions 

dependent on the location of lands in relation to airport operations. The most stringent restrictions apply 

to land located closest to the airport, and the least stringent apply to lands located farther from the airport 

but within the boundary of this Overlay district. 

Chapter 70 Adequate Public Facilities. The purpose of adequate public facilities review is to 

implement adequate public facilities policies of the Comprehensive Plan and other functional plans 

adopted pursuant to the policies of the Comprehensive Plan, including the Lexington Park Transportation 

Plan, the Comprehensive Water and Sewerage Plan, the Educational Facilities Master Plan, the Fire and 

Rescue Services Master Plan, the Land Preservation and Recreation Plan, and the Capital 

Improvements Program (CIP). The ordinance 1) requires developers to provide or make arrangements 

for new or additional public facilities, or upgrades of existing public facilities, including roads, sewerage, 

water, storm drainage, schools, and fire prevention and suppression, that are necessary to address the 

impacts of their projects; 2) controls phasing and timing of development approval by conditioning such 

approval upon a finding that public facilities sufficient to serve proposed development are present or will 

be provided concurrent with that development; 3) encourages new development to occur in areas of the 

County where public facilities are being provided and which are designated for new growth in the 

Comprehensive Plan 4) implements uniform procedures, standards, and requirements for the review of 

development applications, and 5) assures that proposed development will not adversely affect the public 

health, safety, and welfare by requiring the following area addressed: Of particular relevance to this 

hazard mitigation plan are requirements for 

• Storm Drainage. The proposed development shall be served by an adequate storm drainage system. 

A storm drainage system shall be considered adequate if 1)The on-site drainage system installed by 

the developer will be capable of conveying through and from the property the design flow of storm 

water runoff originating in the development during a 2, 10-, and 100-year flood as determined in 

accordance with criteria specified in the Storm water Management Ordinance, in addition to flows 

from undeveloped land upstream in the natural watershed of the proposed development, flows from 

existing upstream developments, and designs flows from developments for which plats and plans 

have been approved, without resulting in erosion, sedimentation or flooding of the receiving channel 

and downstream properties; and 2)The off-site downstream drainage systems are capable of 

conveying to an acceptable outfall the design flow of storm water runoff originating in the 

development, as determined in accordance with criteria specified in the Storm water Management 

Ordinance, in addition to flows from undeveloped land up-stream in the natural watershed of the 

proposed development, flows from existing upstream developments, and design flows from 

developments for which plats have been recorded, without resulting in erosion, sedimentation, or 

flooding of the receiving channel and down-stream properties. 

14



• Fire Prevention and Suppression. APF provisions are administered in conjunction with the St. Mary's 

County Metropolitan Commission and County Fire Board. A proposed development shall be 

considered to be adequately served by fire suppression facilities if 1) developments on public water 

are served at the time of issuance of the first occupancy permit by an approved public (central) water 

supply system or multi-user water supply system capable of providing fire flow in accordance with the 

relevant St. Mary's County agency standards; or 2) development on private wells have Fire flow and 

storage capabilities installed in accordance with NFPA 1142 Standard on Water Supplies for 

Suburban and Rural Fire-fighting. The water source shall be provided, unless specific exemption is 

given for the installation of a sprinkler system by the fire department in whose area the premises lie 

or the amount of water carried on fire apparatus responding on the first alarm is greater than required 

by the standard. When a static water source is approved a dry hydrant with all weather access shall 

be provided to facilitate the fire department taking draft from the source. Water for fire suppression 

shall be available within 1,000 feet of all single buildings under 12,000 sq. ft. area and on site for all 

single buildings over 12,000 sq. ft. area. 

Chapter 71 Resource Protection Standards. The purposes of Chapter 71 are to: 

1) Protect the public health, safety, and welfare by maintaining the water and land resources that 

provide natural functions to prevent loss of land and topsoil to erosion, to filter pollution, nutrient 

and sediment runoff and to mitigate effects of flooding; 

2) minimize the impacts of surface land use on water resources and conserve fish, wildlife, and 

plant habitats while accommodating continued growth; 

3) Protect the County’s most sensitive and diverse ecosystems; 

4) Respect natural constraints and limitations as a primary component of development design; 

5) Enhance and protect the quality of the County’s water resources by controlling soil erosion and 

runoff to the maximum extent practicable. Reduce sources of pollution to meet Chesapeake Bay 

water quality standards; and 

6) Protect the County's ground-water recharge areas and potential surface water impoundment 

sites. 

Applicants are required to identify and put in place measures to protect streams and their buffers, nontidal 

wetlands, the 100-year floodplain , floodway and coastal high hazard, hydric soils, highly erodible 

soils, slopes of 15 to 25% and greater, the Chesapeake Bay Critical Area, defined habitat protection 

areas, natural heritage areas and forest and woodland cover. The development standards are designed 

to implement the Comprehensive Plan criteria for resource protection discussed above. These 

standards of Chapter 71serve to protect sensitive resources from the impacts of development and allow 

the resource to retain their value for hazard mitigation and to protect people, property, structures and 

infrastructure from the hazards associated with location within or in close proximity to sensitive areas. 

Chapter 75 Forest Conservation. The purpose of Chapter 75 is to implement a program for forest 

conservation that regulates the cutting and clearing of certain forests; and to require forest stand 

delineations and forest conservation plans for many development activities. The regulations require 

identification and the protection of priority forest areas (as defined in the ordinance) on planned 

development sites. Of particular importance for hazard mitigation is the priority placed on the protection 

of trees, shrubs and herbaceous plants associated with intermittent and perennial streams and their 

buffers, with slopes over 25 percent; with slopes with highly erodible soils; and with 100-year floodplain 

and drainage way buffers. Retention of forests, mitigation for permissible cutting of forests, and 

“forestation” to plant forest on sites that have insufficient forest coverage are required by the regulations. 

Chapter 76 Floodplain Regulations. Chapter 76 establishes standards and regulations for 

development in the floodplain to manage and in some cases prevent development in areas subject to 

flooding; to require appropriate construction practices to minimize future damage; and to provide for the 

review of all activities proposed within identified floodplains and, by the issuance of permits for those 

15



activities that comply with the objectives of this Ordinance, to assure compliance with relevant federal 

and state programs, including 

1) National Flood Insurance Program (44 CFR Parts 59-79), 

2) Maryland Waterway Construction Permit Program for non-tidal floodplains, 

3) U.S Army Corps of Engineers Section 10 and 404 Permit Programs, 

4) Maryland Tidal and Nontidal Wetlands Permit Programs.; and 

5) Maryland Coastal Zone Management Program. 

The regulations apply to all lands within the unincorporated area of St. Mary's County being subject to 

inundation by floodwaters of the 100-year, regulatory flood or base flood and as delineated on the most 

recent revision of the County floodway maps and FEMA Flood Insurance Rate Maps (FIRMs) and 

described in the flood insurance study (FIS) prepared by the Federal Emergency Management Agency 

(FEMA). Emphasis is on flood height elevation rather than the actual detail of the maps, so that if map 

boundaries and elevations disagree, elevations prevail, with no approval from FEMA required to The 

regulated floodplain includes Mapped Areas which may be may be expanded beyond the designations 

on the FIRM due to elevation. Mapped areas include 1) Non-tidal floodplains (the floodway and the 

floodway fringe) 2)Tidal floodplains in areas subject to coastal or tidal flooding by the100-year flood due 

to high tides, hurricanes, tropical storms, and steady onshore winds and 3) Coastal High Hazard Areas 

subject to coastal or tidal flooding with the addition of high-velocity water and wind action. (designated as 

V-Zones on the FIRMs) 

The county floodplain ordinance closely follows Maryland’s model ordinance with some 

additional provisions to implement Comprehensive Plan policies to eliminate or reduce risk to 

people and property from flooding in the tidal floodplain and by requiring new and replacement 

development to be well outside of the floodplain (50 foot setback) when alternative sites are 

available. 

Subdivision Ordinance 

The current Subdivision Ordinance that went into effect on September 14, 2010 is the primary tool 

governing the subdivision of land in the unincorporated areas of the County. In Section 10.3, the 

ordinance identifies 10 purposes, several of which are relevant to hazard mitigation and avoidance: 

10.3.2. Land shall be suitable for the purpose for which it is subdivided and adequate and effective public 

facilities shall be available, as determined by the Planning Commission. In addition, the public 

improvements shall conform to and be compatible with all other County laws, regulations, plans, 

programs and standards. 

Comment: The review for suitable land and adequate facilities extends to identification of high hazard 

locations unsuitable for subdivision and assuring that appropriate infrastructure is provided to 

avoid, mitigate or eliminate hazard risks. 

10.3.3. To protect and provide for the public health, safety, and general welfare and to prevent 

overcrowding of land and undue congestion of population. 

Comment: This should be extended to include the avoidance of development in high hazard areas. 

10.3.9. To prevent the pollution of air, surface waters; to assure the adequacy of drainage 

facilities; to safeguard the water table; and to encourage the wise use and management of natural 

resources throughout the County in order to preserve the integrity, stability, and beauty of the 

County and the value of the land. 

Comment: Many of the measures required to prevent pollution, assure adequacy of drainage facilities, 

and manage natural resources are also measures that reduce hazard risk.. 

Article 3 Subdivision Standards and Approvals lists at 30.1. that subdivision platting is to “[p]provide 

for adequate light, air, and privacy, to secure safety from fire, flood, and other danger, and to prevent 

16



overcrowding of the land and undue congestion of population. In addition, it will “[g]guide the future 

growth and development in accordance with the Comprehensive Plan.” 

At 30.6.4 The criteria for approval of a preliminary plat includes requirements that subdivisions provide 

adequate public facilities in accordance with Chapter 70 of the Zoning Ordinance, that drainage, 

erosions control and construction complies with accepted engineering and construction practices. 

Applicants are required to specify the “Flood Hazard Zone and source” and to provide a plan that 

illustrates 

− 

− 

− 

− 

− 

storm drain culverts on or adjacent to the property 

physical features of the property, including water courses, shore lines, wetlands, 100 year 

flood plains, existing structures and steep slopes 

soil types, 

topography [that] extend[s] a minimum of 100 feet beyond the property line” and 

proposed development including information about the ‘[m]ethod of water supply and fire 

suppression, 

Applicants must also provide an Erosion and sediment control plan, drainage area map, storm drain 

layout, method and location of storm water quality and quantity treatment including and storm water 

management calculations. Provision of this information allows for review for risk from hazards and the 

requirement that developers provide adequate measures to avoid, mitigate or eliminate hazards to new 

development particularly those associated with flooding and erosion. 

Final plats are required to demonstrate that “[t]he lot and block layout provides for safe and convenient 

vehicular, service and emergency access, efficient utility service connections, and adequate buildable 

area in each lot for planned uses,” “Rights-of-way and easements of adequate size and dimension are 

provided for the purpose of constructing the street, utility, and drainage facilities needed to serve the 

development. 

Section 30.14 discusses requirements for private roads “to provide for the safety of the property owners 

by requiring adequate access for fire, emergency, medical and law enforcement vehicles. It provides for 

the continued uninterrupted use of the access for all of the owners by establishing a durable roadway 

and easement, and assigns responsibility for continued maintenance of the access. The standards 

require that “the design vehicle shall be an emergency response/service/delivery-type vehicle (30-foot 

single unit truck). For local streets, the design vehicle shall be a school bus. For higher classification and 

commercial streets, the design vehicle shall be a tractor trailer/ladder truck-type vehicle (WB-50). 

Comment: Many of the measures (wide roads, wide intersections, extended turning radii) used to 

assure the infrequent need for emergency response/service/delivery-type vehicle access actually in 

crease risk to hazards. The resulting excessive clearing and imperviousness causes increased 

stormwater runoff quantity and velocity which increases flooding and erosion. Wide roads with large 

turning radii encourage excessive speed which increases risks for vehicular and pedestrian accidents. 

The lack of an interconnected street system increases miles driven, traffic congestion, and increases 

carbon emissions which have been linked to climate variability. Lack of interconnection also limits 

alternatives for emergency access. Alternative road design options that allow emergency access without 

increasing hazards should be considered by the County in future plan and ordnance updates. 

Section 30.16. specifies the requirements for public improvement and Infrastructure including storm 

drainage and over lot grading. “Where a development is traversed by a natural drainage course or 

stream, there shall be provided a drainage easement, a minimum of 50 feet in width, conforming 

substantially with the line of such watercourse for the purpose of maintaining, improving, or protecting 

such drainage facilities. This easement area shall be designed to the 100-year flood plain level. 

Applicants must dedicate, either in fee or by drainage easement of land on both sides of existing 

watercourses, where topography or other conditions are such as to make impractical the inclusion of 

drainage facilities within road rights-of-way, perpetual unobstructed easements at least 20 feet in width 

17



for such drainage facilities shall be provided across property outside the road right-of-way….Drainage 

easements shall be carried from the road to a natural watercourse or to other drainage facilities and be 

adequate to accommodate the top width of the design flow, access and maintenance requirements. 

When a proposed drainage system will carry water across private land outside the subdivision, 

appropriate drainage rights must be secured and indicated on the plat with the respective recordation 

information. 

2009 International Building Code and Residential Code 

St. Mary’s County adopted the 2003 International Building and Residential Code for all permitted 

structures in the county in December 2006.. In December 2010 the County adopted the 2009 versions of 

this code, effective date 3 January 2011. The 2009 IBC contains a number of changes to the 2003 IBC 

which will further improve resistance of structures to natural hazards. These changes relate to increased 

standards for anchoring structural components (roofs to walls and columns and walls and columns to 

foundations) and design of roofs, beams, walls, foundations) to improve resistance to forces of wind, 

snow, and earthquake loads in addition to being designed to resist the forces of gravity. Exterior opening 

protection to resist windborne debris will be required for areas within 1 mile of a tidal coastline and wind 

speeds greater than 120 miles per hour. Roof designs will account for rain loads and provide overflow 

scuppers to relieve excess load. The International Code Series is the most comprehensive series of 

code to date. These codes address essentially all areas of building construction and the various building 

services such as electrical, plumbing/gas and mechanical and certain natural hazards. The 2009 building 

code includes requirements that increase resistance to a number of hazards: 

‣ Section 1609 Wind Loads (linear winds) – This section stipulates that Design Professionals must 

design structures that meet 100 miles per hour in their loading design. 

‣ Section 1612, Flood Loads. This section of the code would be replaced with the Maryland 

Floodplain Managers Hand Book. 

‣ Section 1613 through 1623, Seismic Loading – The code specifies that Design Professionals 

utilize a loading factor. Earthquake design has not been a major concern in this area. 

‣ Section 2308.10.1 Wind Uplift. This section discusses the roof tie down requirements to avoid 

blow offs during high wind storms. The new requirements state that the trusses/rafters must be 

tie/strapped down to the foundation of the structure. 

2010 Comprehensive Land Use Plan – Town of Leonardtown 

http://leonardtown.somd.com/government/2010ComprehensivePlan.pdf 

Page 1-5 

The Maryland Economic Growth, Resource Protection and Planning Act of 1992 also added the 

requirement that the comprehensive plan contain a Sensitive Areas Element, which describes how the 

jurisdiction will protect the following sensitive areas: 

• Streams and stream buffers 

• 100-year floodplains 

• Endangered species habitats 

• Steep slopes 

• Other sensitive areas a jurisdiction wants to protect from the adverse impacts of development. 

The 1992 Act requires that all state and local government investments in infrastructure (roads, sewer, 

water. schools. etc) are consistent with adopted local growth management plans. 

Page 11-13 

Protection of Sensitive Areas 

18



The ultimate form of the Town of Leonardtown at build-out will likely be largely defined by McIntosh Run, 

Town Run and Breton Bay as its western, eastern and southern edges respectively. Uses adjacent to 

these bodies of water should continue to be buffered to minimize the impact of land disturbances and 

activity on water quality and wildlife habitat. 

This plan element, the plan’s Sensitive Areas Element and the plans Water Resources Element all 

recognize each of these water resources as sensitive areas. The Town’s goal is to preserve and 

enhance its streams and buffers. Improving storm water management in developed areas is also critical, 

including the use of retrofit to address existing problem areas, and providing incentives for developers 

constructing new storm water management structures to address areas that currently do not have such 

structures. 

The Town will continue to prohibit new development within stream buffers and will prohibit alteration of 

streambeds or stream banks, except for Best Management Practices (BMPs) to reduce erosion or 

stabilization. 

Page 12-1 

The Leonardtown Comprehensive Plan’s “Water Resources Plan Element” (WRE) is a new plan element 

added to the Comprehensive Plan. This plan element is mandated to assure compliance with the 

requirements of Maryland House Bill 1141 (HB 1141). The purpose of the WRE is to provide additional 

layers of planning for water resources in relation to existing use and proposed land use, based on an 

analysis of growth and development trends to assure that demands for water supply, wastewater 

treatment and storm water management can be satisfied as Town growth occurs and to assure adequate 

measures are taken to minimize impacts to water quality. Page 12-19 

Water Resources Goal and Objectives 

The Water Resources Goal for Leonardtown is: 

To maintain a safe and adequate water supply and adequate capacities for wastewater treatment to 

serve projected growth at sustainable levels; to take steps to protect and restore water quality; and to 

meet water quality regulatory requirements in the Breton Bay Watershed. 

Objectives to Support this Goal are: 

• Assure that existing and planned public water systems meet projected demand in a 

sustainable fashion. 

• Assure that existing and planned public wastewater collection and treatment systems meet 

projected demand without exceeding their permitted capacity. 

• Assure that the Town’s storm water management policies reflect the most recent state 

requirements, and require Low Impact Development (LID) practices that utilize Environmental 

Site Design (ESD) principles for managing storm water in both new development and by 

existing homeowners. 

• Maintain land use patterns that limit adverse impacts on water quality. 

• Continue to focus growth to areas best suited to utilize the existing and planned water and 

wastewater infrastructure efficiently and sustainable. 

Page 13-1 

Streams and their Buffers 

Breton Bay and the major streams in Leonardtown are shown on the sensitive areas map in the 

Leonardtown Critical Areas Program. Preservation of natural land and vegetation along a stream 

provides a buffer that protects the stream from sediment, phosphorous, and other runoff pollutants. Major 

tributary streams to Breton Bay include Macintosh Run and Town Run. 

Floodplains 

19



The 100-year floodplain is the land area along a stream that is susceptible to inundation by a flood of a 

magnitude that would be expected to occur on average only once every 100 years as a result of rainfall 

and runoff from upland areas. The 100-year floodplains of streams in Leonardtown are shown on the 

Leonardtown Critical Areas Program map. 

20

Chapter 2: Hazard Identification 


CHAPTER 2 – HAZARD IDENTIFICATION 

Introduction 

This chapter discusses a portion of the risk assessment for St. Mary’s County. The four major 

steps in the risk assessment include hazard Identification, hazard profiles, vulnerability 

assessment, and loss estimation (Figure 4.1). This chapter comprises the first two steps in the 

risk assessment, wherein hazards that may affect St. Mary’s County are identified, and profiled, 

and potential effects are quantified. The nature of the specific hazard, history of previous 

occurrences, and the impact and potential severity of an occurrence have been documented. 

Steps 3 and 4 of the Risk Assessment (vulnerability assessment and loss estimation) will be 

discussed in the next chapter. 

Step 1 - Hazard Identification 

Figure 4.1 – Risk Assessment Steps 

The risk assessment for St. Mary’s County 

involved investigating various types of natural 

hazards faced by the county over the past 

several decades. Since it is assumed that 

hazards experienced by the county in the past 

may be likely to occur in the future, the hazard 

identification process included a history and 

an examination of various hazards and their 

occurrences. Information on past hazards 

was based on research from historical 

documents and newspapers; County plans 

and reports; conversations with county 

residents and public officials, and internet 

websites. Data and maps that were available 

online included sources such as the United 

States Geological Survey (USGS), Spatial 

Hazard Events and Losses Database for the 

United States (SHELDUS), and the National 

Weather Service. 

Step 2 - Hazard Profiles 

This step involves determining the frequency or probability of future events, their severity, and 

factors that may affect their severity. Each hazard type has unique characteristics that can 

impact the county. For example, no two flood events will impact a community in the same 

manner. Also, the same hazard events can affect different communities in different ways based 

on geography, development, population distribution, age of buildings, etc. Developing hazard 

event profiles enables us to answer the question “how bad could a hazard get?” 

21



Hazard Identification 

The Hazard Mitigation Planning Team reviewed a list of potential hazards and identified those 

that have been known to occur in St. Mary’s County. The list of hazards reviewed was obtained 

from the State of Maryland Core Plan for Emergency Response (2009) and the Maryland 

Hazard Identification Risk Assessment completed by MEMA. This assessment ranks wildfires 

and tornados as medium-high hazards; tidal/coastal flooding, extreme heat, hurricanes, 

thunderstorms, and winter weather as medium hazards and flash/riverine flooding, ice and 

drought as medium-low hazards for St. Mary’s County. The following natural hazards have been 

documented in St. Mary’s County as occurring over the past 50 years or a potential does exist 

to occur and have been assessed as risks for the purpose of this study and have been 

categorized into the following sections: atmospheric, wildfire, hydrologic, and geologic. They 

are not listed in any order of priority. 

Atmospheric Hazards: Thunderstorms, Lightning, Tornadoes, Hurricanes, Hailstorms, Severe 

Winter Storms, Extreme Summer Heat 

Wildfire Hazards: Wildfires, Urban Interface Fires 

Hydrologic Hazards: Floods, Erosion of coastal shorelines, Erosion of upland surfaces and 

stream channels, Drought 

Geologic Hazards: Earthquakes, Landslides/Land Subsidence 

Discussion of Hazards 

Thunderstorms 

Overview 

Thunderstorms are forms of convection produced when warm moist air is overrun by dry cool 

air. As the warm air raises, thunderhead clouds (cumulonimbus) form and cause the strong 

winds, lightning, thunder, hail, and rain associated with these storms. Instability can be caused 

by surface heating or upper-tropospheric (~50,000 feet) divergence of air (rising air parcels can 

also result from airflows over mountainous areas). Generally, the former “air mass” 

thunderstorms form on warm-season afternoons and are not severe. The latter “dynamicallydriven” 

thunderstorms generally form in association with a cold front or other regional-scaled 

atmospheric disturbance. These storms can become severe, thereby producing strong winds, 

frequent lightning, hail, downbursts, and even tornadoes. 

The National Weather Service’s definition of a severe thunderstorm is a thunderstorm event that 

produces any of the following: downbursts with winds of 58 miles (50 knots) per hour or greater 

(often with gusts of 74 mph or greater), hail 0.75 inch in diameter or greater, or a tornado. 

Typical thunderstorms can be 3 miles wide at the base, rise to 40,000-60,000 feet in the 

troposphere, and contain half a million tons of condensed water. 

Historic Activity 

According to the National Climatic Data Center, approximately 125 thunderstorm and high wind 

events were reported in St. Mary’s County, Maryland, between January 1950 and August 2010, 

resulting in a total of 9 injury cases, $1.01 million in property damage, and $5,000 in crop 

damage. The following events are worthy of mention: 

• On 24 June 1996, a major thunderstorm caused three buildings to sustain considerable 

damage as it raced toward the central Chesapeake Bay. Property damage of $85,000 was 

estimated in St. Mary’s County. 

22



• On 4 February 1998, a powerful nor'easter, carrying heavy moisture from the Gulf of Mexico 

and Caribbean region, dumped between 2 and 4 inches of rain across much of Maryland 

between the foothills and the Chesapeake Bay. The nor'easter, coming on the heels of one 

just a week earlier, caused tides of 3 to 4 feet above normal from the Calvert County/Anne 

Arundel County line south to Point Lookout in extreme southeastern St Mary's County; and 

along the lower tidal Potomac River along the Charles and St Mary's Counties shoreline, 

including Cobb Island and St George Island. A daily rainfall record was broken at 

Baltimore/Washington International Airport (BWI); the 1.65 inches that fell on the 4th broke 

the 78 year-old Baltimore area mark of 1.48 inches. Flooding was most pronounced in St 

Mary's County. During the peak of the storm, 26 roads were closed due the combination of 

wind and rain. Nine roads were closed due to flooding alone. State thoroughfares affected 

included Routes 5, 237, 238, 243, and 271. Evacuations were initiated in Great Mills and on 

St George Island due to rapid increases in tide levels. At least 200 residents were 

evacuated, including one 3 year-old boy who required a water rescue. Four fire fighters were 

treated for hypothermia at St Mary's Hospital. Some cars were nearly submerged in lowlying 

areas. In the Golden Beach neighborhood, Lake White overtopped its banks, and poor 

drainage contributed to the widespread flooding. The dam at St. Mary's Lake held; overflow 

problems were minimal. The sewage system serving Lexington Park failed due to the 

abnormally heavy flow of water, which caused manholes to flood. Four thousand citizens 

were affected in St Mary's County. Property damage of $145,000 and crop damage of 

$200,000 was reported. 

Lightning 

Overview 

Lightning is defined as a sudden and violent discharge of electricity from within a thunderstorm 

due to a difference in electrical charges and represents a flow of electrical current from cloud-tocloud 

or cloud-to-ground. Nationally, lightning causes extensive damage to buildings and 

structures, kills or injures people and livestock, starts untold numbers of forest fires and 

wildfires, and disrupts electromagnetic transmissions. Lightning is extremely dangerous during 

dry lightning storms because people remain outside due to the lack of precipitation; however, 

lightning is still present during the storm. 

At any given time, there are nearly 2,000 thunderstorms in progress over the earth's surface. 

There are at least 100,000 thunderstorms annually across the United States. To the general 

public, lightning is often perceived as a minor hazard. However, lightning-caused damage, 

injuries, and deaths establish lightning as a significant hazard associated with any thunderstorm 

in any area of Maryland. 

Damage from lightning occurs four ways: (1) electrocution/severe shock of humans and 

animals, (2) vaporization of materials along the path of the lightning strike, (3) fire caused by the 

high temperatures associated with lightning (10,000-60,000°F) and (4) the sudden power surge 

that can damage electrical/electronic equipment. Large outdoor gatherings (e.g., sporting 

events, concerts, campgrounds, etc.) are particularly vulnerable to lightning strikes that could 

result in injuries and deaths. 


There have been 16 major lightning events in St. Mary’s County between January 1950 and 

August 2010, resulting in $662,000 worth property damage. No injuries, fatalities, or crop 

damage was reported. Some of these are discussed below: 

• A structure was heavily damaged by a fire when lightning struck on 16 July 2000. 

Scattered thunderstorms that produced winds in excess of 55 MPH, heavy rainfall, large 

23



hail, and frequent lightning moved across Maryland during the morning and afternoon of 

the 16th. In St. Mary's County, a fire started by lightning heavily damaged a home in 

Hollywood. Marble sized hail fell in Leonardtown and pea sized hail fell in California and 

Tall Timbers where a total of 2.46 inches of rain fell. In Prince George's County, dime to 

quarter sized hail fell in Bowie and Mayo and pea-sized hail fell in Lanham. Trees were 

downed in Bowie. In Anne Arundel County, trees and power lines were downed. Quarter 

sized hail fell on Route 2 south of Annapolis. In Calvert County, trees and power lines 

were downed in Dunkirk and Chaneyville. A total of 3.20 inches of rain fell in 

Huntingtown where pea- to nickel-sized hail was reported. Pea-sized hail also fell in 

Owens, Dunkirk, and Chesapeake Beach. Winds estimated at 50 MPH were also 

reported in Chesapeake Beach. In Baltimore County, 1.50 inches of rain fell at Lake 

Roland. Large trees were downed between Reisterstown and Cockeysville and heavy 

downpours flooded roads in Towson and Parkville. In Frederick County, quarter-sized 

hail destroyed a cornfield in Thurmont and a car was hit by lightning, but no one was 

injured. Property damage was estimated at $160,000. No crop damage was reported. 

• On 17 June 2004, lightning caused a fire at a cabinet shop in Loveville. Thunderstorms 

accompanied by strong winds and heavy rainfall affected the Mid-Atlantic region during 

the evening of the 17th. Reports of downed trees, a weak tornado, lightning strikes, and 

torrential rainfall came from northeast and lower southern Maryland. A weak tornado 

touched down just outside of LaPlata in Charles County. Many homes and structures 

were damaged by fire and water. Firemen reported several fires caused by lightning in 

St. Mary's and Prince Georges Counties. Emergency personnel also reported the ceiling 

of a restaurant in Inverson Mall in HillCrest Heights collapsed under the weight of rain 

water, and flash flooding necessitated a water rescue on the Suitland Parkway. Property 

damage was estimated at $120,000. No crop damage was reported. 

Tornadoes 

Overview 

A tornado is a relatively short-lived storm composed of an intense rotating column of air, 

extending from a thunderstorm cloud system. Average winds in a tornado, although never 

accurately measured, are thought to range between 100 and 200 miles per hour, but some may 

have winds exceeding 300 miles per hour. The following are National Weather Service 

definitions of a tornado and associated terms: 

• Tornado - A violently rotating column of air that is touching the ground. 

• Funnel cloud - A rapidly rotating column of air that does not touch the ground. 

• Downburst - A strong downdraft, initiated by a thunderstorm, which induces an outburst of 

straight-line winds on or near the ground. They may last anywhere from a few minutes in 

small-scale microbursts to periods of up to 20 minutes in larger, longer macro-bursts. Wind 

speeds in downbursts can reach 150 mph and therefore can result in damages similar to 

tornado damages. 

Tornadoes are classified on a scale of 0 to 5 by the degree of damage they cause. This tornado 

classification is called the Fujita Scale and is shown in Table 4.1. 

Table 4.1 - Tornado Damage Scale 

24



Scale Wind Speeds Damage Frequency 

F0 40 to 72 MPH Some damage to chimneys, TV 

antennas, roof shingles, trees and 

windows 

F1 73 to 112 MPH Automobiles overturned, carports 

destroyed, trees uprooted 

F2 

F3 

113 to 157 MPH Roofs blown off homes, sheds and 

outbuildings demolished, mobile 

homes overturned 

158 to 206 MPH Exterior walls and roofs blown off 

homes. Metal buildings collapsed 

or are severely damaged. Forests 

and farmland flattened. 

29% 

40% 

24% 

6% 

Nearly 70 percent of deaths from 

tornadoes happen to people located 

in residential structures. Of these, 

over 40 percent are located in 

mobile homes, which are easily 

overturned and destroyed due to the 

low wind resistance of the structure. 

Table 4.2 breaks down the tornado 

deaths in the United States based 

on location or other circumstances. 

F4 

207 to 260 MPH Few walls, if any, standing in wellbuilt 

homes. Large steel and 

concrete missiles thrown far 

distances. 

F5 261 to 318 MPH Homes leveled with all debris 

removed. Schools, motels and 

other larger structures have 

considerable damage with exterior 

walls and roofs gone. Top stories 

demolished. 

Source: National Weather Service 

Http://www.spc.noaa.gov/climo/torn/locat 

ions.html 

Although the magnitude and location of tornadoes are unpredictable, most of those that 

occurred in the County over the last 55 years have been classified as low intensity (F0 and F1). 

There was one case of an F2 tornado event in 1983. These tornadoes have had no history of 

fatalities or crop damage. A total of four injuries have been reported in these tornadoes. The 

property damage to St. Mary’s County was approximately $4 million. 

Table 4.3 - Tornado History 1950-2010 


Location Date Type Magnitude Injuries 

Property 

Damage 

St. Mary's County 1/27/1967 Tornado F1 0 3K 



St. Mary's County 5/8/1984 Tornado F1 3 2.5M 



Naval Air Station 8/6/1995 Tornado F0 0 0 

White Point Beach 10/5/1995 Tornado F1 0 5K 

Patuxent 10/27/1995 Tornado F0 0 0 

Hollywood 11/11/1995 Tornado F0 0 75K 

Patuxent River 11/11/1995 Tornado F0 0 5K 

California 7/13/1996 Tornado F1 0 100K 

Hollywood 7/31/2000 Tornado F0 0 1K 

St Inigoes 5/22/2001 Tornado F0 0 1K 

Thompson Corner 5/7/2003 Tornado F0 0 25K 

Oakville 5/7/2003 Tornado F0 0 25K 

California 7/14/2004 Tornado F1 0 5K 

Chaptico 6/27/2006 Tornado F0 0 1.0M 

TOTALS: 44.060M 

2% 

Less than 

1% 

Based on data from the National 

Climatic Data Center, St. Mary’s 

County experienced 18 tornado 

events between January 1950 and 

August 2010. Some of these are 

elaborated below: 

• On 11 November 1995, a 

combination gustnado and 

microburst struck near 

Hollywood, downing numerous 

pine and hardwood trees. 

Fallen trees caused minor 

damage to three homes, 

including stripped siding and a 

limb through a window. The 

apparent gustnado had a very 

short and narrow track (0.3 

miles long, 25-yards wide) and 

25



was embedded within the microburst. Property damage worth $75,000 was estimated in St. 

Mary’s County. 

• On 7 May 2003, a weak tornado damaged some agricultural buildings along Lockes 

Crossing Road. Severe thunderstorms moved southeast through Charles and St. Mary's 

counties during the evening of the 7th. In St. Mary's County, the storms produced damaging 

winds, tornadoes, heavy rain, and hail. Two tornadoes were produced by these storms 

across northern St. Mary's County. The first tornado touched down near the intersection of 

Route 236 (Thompsons Corner Road) and Woodburn Hill Road in the community of 

Thompson Corner (just west of Mechanicsville). The tornado traveled straight east along 

Lockes Crossing Road for one half mile before dissipating. Along its path trees were 

downed, a roof was damaged, a machine shed lost its roof, and a 30 foot x70 foot barn was 

destroyed. The tornado had a path width of 75 yards and was classified at F0 strength. The 

second tornado touched down near the intersection of Route 235 (Three Notch Road) and 

North Sandgates Road (Route 472) near Oakville. It moved northeast along North 

Sandgates Road for 2 miles before it pushed offshore. It became a waterspout that tracked 

toward Broomes Island. Along the tornado's inland path, several trees and power lines were 

downed. One tree fell onto a trailer home, significantly damaging the structure. Two other 

homes sustained minor damage. The twister was 100 yards wide and was rated at F0 

strength. Trees and power lines were downed by high winds in the communities of 

Hollywood, Leonardtown, Charlotte Hall, Oakville, New Market, Laurel Grove, and at 

Summerseat Sanctuary. Trees had to be cleared from the following roads: Friendship 

School Road, Bishop Road, McIntosh Road, Clover Hill Road, Queentree Road, Jones 

Wharf Road, Cat Creek Road, Laurel Grove Road, Morganza Turner Road, and South 

Sandgates Road. Two cars were crushed by fallen trees in Hollywood. Nickle-sized hail was 

reported in Mechanicsville. A spotter in Hollywood reported 3.15 inches of rainfall in one 

hour and 45 MPH winds. Flooding was reported on Three Notch Road ans Chancellors Run 

Road (MD 235 and MD 246) in Lexington Park. Other roads that were inundated by water 

include Baptist Church Road, Mechanicsville Road, Dr. Johnson Road, and Foley Mattingly 

Road. Two unconfirmed reports of funnel clouds were received from residents of 

Hermanville and Scotland. The Scotland observer said the funnel was spotted over the 

Potomac River. Lightning associated with the storms started a house fire in Hollywood and a 

shed fire in Mechanicsville. Property damage in the County was estimated at $25,000. 

• On 14 July 2004, A cold front moved through the area and triggered numerous showers and 

thunderstorms over Maryland. The stronger storms were concentrated over Northeast and 

Lower Southern Maryland. These storms produced tornadoes, waterspouts, damaging 

winds and penny to quarter size hail. In St. Mary's County, an F1 tornado touched down just 

northwest of California and moved east-southeast. The tornado uprooted, snapped and 

twisted many medium and large trees. Maximum wind speeds were estimated at 80 mph. 

Strong thunderstorm winds moved a single engine plane in Hollywood. The plane was lifted 

and tossed upon another plane, totally destroying one and causing significant damage to the 

other. A waterspout also was spotted on the Potomac River adjacent to St. Mary's County. 

• On 27 June 2006, a waterspout came onshore from the Chesapeake Bay near Chaptico as 

a tornado, and caused structural damage to several properties in addition to extensive tree 

damage. The storm destroyed six barns and a carport at two farms along Hurry Road, and 

also destroyed a barn off Beavan Lane. Several homes and commercial buildings were also 

damaged. Since an official damage survey was not conducted, the path length, width and F 

scale rating were estimated based on reports from Emergency Management and 

newspapers. This storm caused approximately $1 million in damages. 

26



Profile 

Figure 4.2 - FEMA’s Design Wind Speed for Community Shelters 

A tornado path averages 4 

miles in length, but may 

reach up to 300 miles in 

length. Widths average 

300-400 yards (0.17 to 

0.23 miles), but severe 

tornadoes have cut swaths 

a mile or more in width, or 

have formed groups of two 

or three funnels traveling 

together. On the average, 

tornadoes move between 

25 and 45 miles per hour 

(mph), but speeds over 

land of up to 70 mph have 

been reported. Tornadoes 

rarely last more than a 

couple of minutes over a 

spot for more than 15-20 

minutes in a 10-mile area, but their short periods of existence do not limit their devastation of an 

area. The destructive power of a tornado results primarily from its high wind velocities and 

sudden changes in pressure. Damages from tornadoes result from extreme wind pressure and 

windborne debris. Because tornadoes are generally associated with severe storm systems, 

they are often accompanied by hail, torrential rain, and intense lightning. Depending on their 

intensity, tornadoes can uproot trees, bring 

down power lines, and destroy buildings. 

Figure 4.3 - History of Maryland Tornadoes 

Flying debris is the main cause of serious 

injury and death. 

Downbursts are characterized by straightline 

winds. Downburst damage is often 

highly localized and resembles that of 

tornadoes. There are significant 

interactions between tornadoes and 

downbursts and a tornado's path can be 

affected by downbursts. Because of this, 

the path of a tornado can be very 

unpredictable, including veering right and 

left or even a U-turn. 

FEMA’s publication, Design and Construction Guidance for Community Shelters, July 2000, 

presents a map of four wind zones in the U.S. (consistent with ASCE 7-98) and provides design 

wind speeds for shelters and other critical facilities. Zone IV shows the areas of highest wind 

activity which are situated in the Midwest and Tornado Alley, while Zone I shows the areas of 

lowest activity, which are in the western part of the United States. Figure 4.2 indicates that St. 

Mary’s County falls in Zone II (design wind speed of 160 mph) and within a hurricane 

susceptible region. 

27



Figure 4.3 indicates that approximately 209 tornadoes have occurred in Maryland between 1950 

and 1998. There were 12 incidents in St. Mary’s County during that period. 

Hurricanes 

Overview 

Hurricanes and tropical storms, as well as tropical depressions, are all tropical cyclones defined 

by the National Weather Service’s National Hurricane Center (NHC) as warm-core non-frontal 

synoptic-scale cyclones, originating over tropical or subtropical waters, with organized deep 

convection and a closed surface wind circulation around a well-defined center. Once they have 

formed, tropical cyclones maintain themselves by extracting heat energy from the ocean at high 

temperatures and releasing heat at the low temperatures of the upper troposphere. Hurricanes 

and tropical storms bring heavy rainfalls, storm surge, and high winds, all of which can cause 

significant damage. 

These storms can last for several days and, therefore, have the potential to cause sustained 

flooding, high wind, and erosion. 

Storm Surge - Storm surge can be modeled by various techniques; one such technique is the 

use of the NWS’s Sea, Lake and Overland Surges from Hurricanes (SLOSH) model. The 

SLOSH model is used to predict storm surge heights based on hurricane category. Surge 

inundation areas are classified based on the category of hurricane that would cause flooding. 

From the SLOSH maps, it may be concluded that the VE zones would be inundated during a 

Category 1 storm. As the category 

of the storm increases, more land 

area will become inundated. Storm 

surge is a major component of 

nor’easter storms along the East 

Coast of the U.S. because as the 

storm is rotates counter clockwise, 

high winds winds are moving from a 

north and/or eastward position 

across the ocean toward shore 

pushing water inland and forming 

large waves.. 

Hurricanes are classified using the 

Saffir-Simpson Hurricane Scale 

(Table 4.4), which rates the 

intensity of hurricanes based on 

wind speed and barometric 

pressure measurements. The scale 

is used by the National Weather 

Service to predict potential property 

damage and flooding levels from 

imminent storms. 


Category 

Table 4.4 - Saffir-Sampson Scale and Typical Damages 

Sustained 

Wind Speeds 

(m ph) 

Surge (ft) 

Pressure 

(m b) 

Typical Dam age 

Tropical 

980 Minimal – 

Very dangerous w inds 

w ill p ro duc e s ome 

damage 

Hurricane 2 96-110 38511 965-980 Moderate – 

Extremely dangerous 

w ind s w ill c aus e 

extensive damage 

Hurricane 3 111-130 38607 945-965 Extensive Damage – 

Devastating damage w ill 

occur 

Hurricane 4 131-155 13-18 920-945 Extreme Damage – 

Catastrophic damage w ill 

occur 

. 

Hurricane 5 > 155 > 18 < 920 Catastrophic Damage – 

Catastrophic damage w ill 

occur 

Three tropical storm events were reported in St. Mary's County, Maryland, between January 

1950 and August 2010, resulting in 1 death, 200 injuries, $531 million in property damage, and 

$190,000 in crop damage. A few events have been elaborated below. 

28



• Hurricane Floyd made landfall just east of Cape Fear, North Carolina in the early morning 

hours of 16 September 1999, and moved north-northeast across extreme southeast Virginia 

to near Ocean City, Maryland by evening on the 16th. The eye of Hurricane Floyd passed 

east of the Chesapeake Bay between 9:00 a.m. and midnight on the 16th. Between 8 and 

12 inches fell across St. Mary's, Anne Arundel, and Harford Counties. The amount of 

damage Anne Arundel, Calvert, Charles, Harford, and St. Mary's Counties received from the 

storm qualified them for FEMA disaster assistance. Tidal flooding was reported along the 

Chesapeake Bay. Strong southerly winds ahead of the hurricane pushed tides 2 to 3 feet 

above normal, flooding several low-lying areas in St. Mary's, Calvert, Harford, and Anne 

Arundel Counties. Erosion was reported on the South River and Broad Creek. In St. Mary's 

County, Piney Point Road, the only causeway to St. George Island went underwater, 

trapping a half dozen residents on the island. Tropical downpours also led to flooding. In St. 

Mary's County, high winds blew a cross bar off a church steeple and knocked out power to 

5000 customers. Winds gusted to 71 mph at Tall Timbers, 43 mph at St. Indigoes, and 45 

mph at Hollywood. A wind gust of 65 mph was recorded at Patuxent River Naval Air Station 

at 11:45 a.m. eastern daylight time (EDT). One location reported 10.6 inches of rain 

between 6 a.m. and 4 p.m. EDT on the 16th. Emergency responders rescued 28 people by 

boat from a trailer park, homes, and stranded cars after the St. Mary's River and other 

waterways flooded. Nine other people were rescued from an apartment building near Great 

Mills. Property damage to Maryland counties was estimated at $900,000. No crop damage 

was reported. 

• On September 18, 2003, Hurricane Isabel made landfall on the North Carolina Coast. Its 

huge wind field was already piling water up into the southern Chesapeake Bay. By the time 

Isabel moved into central Virginia, it had weakened and was downgraded to a tropical storm. 

Isabel's eye tracked well west of the Chesapeake Bay, but the storm's 40 to 50 mph 

sustained winds pushed a bulge of water northward up the Bay and its tributaries, producing 

a record storm surge. Maryland saw 472 homes and buildings destroyed, 3,260 with major 

damage and over 3,600 more affected. Extensive damage occurred to Maryland's shoreline, 

which rarely sees storms of this intensity. In St Mary's County, residents saw 6-foot waves 

crashing onto shore and some homes literally flattened. Estimated damage to wharfs and 

piers was 2,500 destroyed and 1,000 with moderate damage costing $10.25 million. 

Damage to Point Lookout State Park was $3 million. Damage to "shore revetments" was 

$53.4 million. Damage to residential property is estimated at $16.95 million and businesses 

$1.5 million. Most of the damage resulted from storm surge, but some was from wind. On St. 

George Island, 20 homes were destroyed and water covered much of the island at high tide 

for a week. The bridge to the island washed out as early as 3:45 p.m. on Thursday. Wind 

damage to structures was limited with the greatest damage reported in St. Mary's County, 

where, on one property, winds blew the roof off a structure and knocked down 70 trees. 

Unofficial wind gust readings of up to 110 mph have been reported, but not confirmed. 

Patuxent Naval Air Base recorded wind gusts to 69 mph at midnight and Quantico Marine 

Base recorded a wind gust of 78 mph near the same time. St Mary's County had 27,092 

customers lose power. While most people had their power restored within a week, some 

locations took up to 2 weeks. Many injuries and three fatalities occurred from carbon 

monoxide poisoning from people improperly running generators in their houses. Other 

injuries resulted chain saws during the clean-up of debris. Property damage to Maryland 

counties was estimated at $530.5 million and crop damage was estimated at $190,000. 

A review of historical tracks of tropical weather systems indicates St. Mary’s County has been 

affected by such storms over 100 times since 1886. Figure x shows the storm tracks of the 

designated hurricanes, 57 tropical storms, and 21 subtropical depressions passing over or 

within approximately 65 miles of St. Mary’s County since 1886. These only represent 

29



hurricanes or tropical storms passing within the 65-mile radius. Numerous severe storms have 

struck the Atlantic Coast both above and below St. Mary’s County, including Bertha (1996), 

Floyd (1999), and Isabel (2003) and Tropical Storm Ernesto (2006). The earliest recorded 

hurricane dates back to 1859. 

Figure 4.5 - Hurricanes Within 65 Miles of St. Mary’s County Since 1886 

Profile 

Because hurricanes can disrupt power and inundate roads, they can wreck havoc on the entire 

community. FEMA’s publication, Taking Shelter from the Storm, August 2008, presents a map 

of four wind zones in the U.S. and provides design wind speeds for shelters and other critical 

facilities (Figure 4.4). Zone IV shows the areas of highest wind activity, which are situated in the 

Midwest and Tornado Alley; Zone I shows the areas of lowest activity, which are in the western 

U.S. St. Mary’s County is mapped in Zone II (design wind speed of 160 mph 3-second gust). 

Hailstorms 

Overview 

Hailstorms are violent and spectacular phenomena of 

atmospheric convection, always associated with 

Figure 4.4 - Wind Zones in the United States 

heavy rain, gusty winds, thunderstorms, and 

lightning. Hail is a product of strong convection and Hurricanes 

occurs only in connection with a thunderstorm where 

the high velocity updrafts carry large raindrops into 

the upper atmosphere (where the temperature is well 

below the freezing point of water). 

Hailstones grow in size when the frozen droplet is 

repeatedly blown into the higher elevations. The 

hailstone ascends as long as the updraft velocity is 

30



high enough to hold the hailstone. As soon as the size and weight of the hailstone overcome the 

lifting capacity of updraft, it begins to fall freely under the influence of gravity. The falling of 

hailstones, under thunderstorm conditions, is accompanied with a cold downdraft of air. 


A total of 46 hailstorms were reported in the county between January 1950 and August 2010. 

No fatalities or injuries were reported in these cases. The county incurred $12,000 in property 

damage. No crop damage was reported. 

• Hail nearly the size of golf balls was reported near Hollywood by the county sheriff's 

department on 25 May 1994. Property damage was estimated at $5,000. 

• On 4 May 1996, 2 inch diameter hail was reported by National Weather Service Storm 

Spotters in Lexington Park, and hail up to 1 inch in diameter was reported farther southeast, 

extending to Ridge. Approximately $5,000 of property damage was reported in St. Mary’s 

County. 

• On 19 August 2009, two reports were received by separate spotters, one with 2.75 inch 

diameter and the other with 1.75 inch diameter hail in Abells Wharf with an addition report of 

1 inch diameter hail in Compton. This event produced the largest hail recorded in St. Mary’s 

County. 

Profile 

Most of the "damaging" hailstones vary between the size of a golf ball ("severe") to the size of a 

softball or larger ("oversized"). According to the National Weather Service, most of the United 

States experience "severe" and "oversized" hailstorms. The largest recorded hailstone in the 

United States fell in Vivian South Dakota, on 23 July 2010, and measured more than 8 inches in 

diameter and weighed 1.94 pounds, generating an impact force of 578 lb-ft. Hailstorms occur all 

year round at all times of the day, but are more frequent in the summer months, in the evenings, 

and after sunset. 

Severe Winter Storms 

Overview 

Winter storms can vary in size and strength and include heavy snowstorms, blizzards, freezing 

rain, sleet, ice storms, and blowing and drifting snow conditions. Extremely cold temperatures 

accompanied by strong winds can result in wind chills that cause bodily injury such as frostbite 

and death. A variety of weather phenomena and conditions can occur during winter storms. For 

clarification, the following are National Weather Service approved descriptions of winter storm 

elements: 

• Heavy snowfall - the accumulation of 6 or more inches of snow in a 12-hour period or 8 

or more inches in a 24-hour period. 

• Blizzard - the occurrence of sustained wind speeds in excess of 35 miles per hour 

accompanied by heavy snowfall or large amounts of blowing or drifting snow. 

• Ice storm - an occurrence where rain falls from warmer upper layers of the atmosphere 

to the colder ground, freezing upon contact with the ground. 

• Freezing drizzle/freezing rain - the effect of drizzle or rain freezing upon impact on 

objects that have a temperature of 32 degrees Fahrenheit or below. 

• Sleet - solid grains or pellets of ice formed by the freezing of raindrops or the refreezing 

of largely melted snowflakes. This ice does not cling to surfaces. 

31



• Wind chill - an apparent temperature that describes the combined effect of wind and low 

air temperatures on exposed skin. 

Maryland’s greatest winter storms are the nor’easters. For nor'easters to occur in Maryland, an 

arctic air mass should be in place. While high pressure builds over New England, cold arctic air 

flows south from the high-pressure area. The dense cold air is unable to move west over the 

Appalachian Mountains and so it funnels south down the valleys and along the Coastal Plain. 

Winds around a nor’easter’s center can become intense. The strong northeast winds that rack 

the coast and inland areas give the storm its name. The wind builds large waves that batter the 

coastline and sometimes pile water inland, causing major coastal flooding and severe beach 

erosion. Unlike hurricanes, which usually come and go within one tide cycle, a nor’easter can 

linger through several tides, each one piling more and more water on shore and into the bays, 

dragging more sand away from the beaches. 


Table 4.5 - Winter Weather History 

There were 

approximately 24 major 

winter storm incidents 

in St. Mary’s County 

between January 1950 

and August 2010, 

resulting in 2 deaths, 

11 injuries, and $5.6 

million in property 

damage (Table 4.5). A 

few of these are 

elaborated below: 

Location Date Type Magnitude Deaths Injuries 

Property 

Dam age 

Crop 

Dam age 

Maryland Counties 2/14/2003 Winter Storm N/A 1 10 5.2M 0 

Maryland Counties 2/26/2003 Winter N/A 0 0 0 0 

Maryland Counties 1/17/2004 Winter N/A 0 0 0 0 

Southern Maryalnd 1/25/2004 Winter / N/A 0 0 0 0 

CSt. Mary's County 2/11/2006 Heavy Snow / N/A 0 0 230K 0 

St. Mary's County 2/12/2007 Winter Storm N/A 0 0 0 0 



St. Mary's County 12/18/2009 Winter Storm N/A 0 0 750K 0 


• A complex storm 

system produced 

copious amounts of 

wintry precipitation 

across Maryland 

St. Mary's County 

Maryland Counties 

TOTAL 

2/2/2010 Winter Storm 

2/5/2010 Winter Storm 

N/A 0 2 

0 2.5M 

11 8.68M 

0 0 

0 

0 

west of the Chesapeake Bay between the evening of the 14 and midday on the 18 of 

February 2003. Hollywood (St. Mary's County) recorded 7.5 inches of accumulation (almost 

all sleet). Nicknamed the President's Weekend Snowstorm of 2003, this storm will go down 

in history as the heaviest snowstorm in the Baltimore region since records began in 1870. 

One fatality and 10 injuries were reported. Property damage to Maryland counties was 

estimated at $5.2 million. No crop damage was reported. 

• A potent area of low pressure strengthened over the central portion of the nation on 5 

February 2010. The storm system slowly moved through the Mid-Atlantic during the night of 

the 5th before redeveloping off the Mid-Atlantic coast on 6th. The storm system finally 

moved away from the area on the night of the 6th. Strong high pressure continued to pump 

in plenty of cold air across the region during the entire event. Due to the slow movement of 

the storm, there was a prolonged period of precipitation. The storm system ushered in 

copious amounts of moisture from the Gulf of Mexico and the Atlantic Ocean. The deep 

moisture combined with the forcing from the storm system to bring a period of heavy 

precipitation to the area on the night of the 5th through the daytime hours on the 6th. The 

highest level of actual accumulation in St. Mary’s County occurred in Mechanicsville at 19 

inches. A second storm followed on 9 February 2010 and brought another lower level of 

accumulation but was compacted with the first storm’s snowfall to bring over 30 inches of 

32



snow total to certain areas. Major snow accumulations were reported throughout the state of 

Maryland and many counties including St. Mary’s County received a Presidential Disaster 

Declaration. 

Profile 

All areas of St. Mary’s County are subject to the effects of winter storms. These storms may 

include snowstorms, sleet storms, ice storms, and blizzards. Major winter storms and 

occasional blizzard conditions bring bursts of heavy snow accumulating 3-6 inches in short 

periods or 1-2 feet in 12-24 hours. Blizzard conditions develop with winds over 35 mph whhc 

decrease visibility and increase the wind chill factor. Freezing rain and drizzle will create a 

coating of ice that is hazardous to walk on. Other impacts include hazardous conditions caused 

by falling trees and powerlines; requirement of additional manpower to clear debris, snow 

removal and salting; large scale use of public shelters; and traffic delays. 

Extreme Summer Heat 

Overview 

Temperatures that hover 10 degrees or more above the average high temperature for the region 

and last for several weeks are defined as extreme heat. A heat wave is primarily a public health 

concern. During extended periods of very high temperatures or high temperatures coupled with 

high humidity, individuals can suffer a variety of ailments, including heat stroke, heat 

exhaustion, heat syncope, and heat cramps. 

• Heat stroke, in particular, is a life threatening condition that requires immediate medical 

attention. It exists when the body’s core temperature rises above 105°F as a result of 

environmental temperatures. Victims may be delirious, stuporous, or comatose. The deathto-care 

ratio in reported cases in the U.S. averages about approximately 15 percent. 

• Heat exhaustion is much less severe than heat stroke. The body temperature may be 

normal or slightly elevated. A person suffering from heat exhaustion may complain of 

dizziness, weakness, or fatigue. The primary cause of heat exhaustion is fluid and 

electrolyte imbalance. The normalization of fluids will typically alleviate the situation. 

• Heat syncope is typically associated 

with exercise by people who are not 

acclimated to exercise. The symptom is 

a sudden loss of consciousness. 

Consciousness returns promptly when 

the person lies down. The cause is 

primarily associated with circulatory 

instability as a result of heat. The 

condition typically causes little or no 

harm to the individual. 

• Heat cramps are typically a problem for 

individuals who exercise outdoors, but 

are unaccustomed to heat. Similar to 

heat exhaustion, it is thought to be a 

result of a mild imbalance of fluids and 

electrolytes. 

Table 4.6 -Heat Danger Categories 

Danger 

Category 

Category 

Nam e 

He at Dis orde rs 

In 1979, R.G. Steadman, a meteorologist, 

developed the heat index, which is shown in 

Table 4.6, to illustrate the risk associated with extreme summer heat. 

IV 

Extreme 

Danger 

Heatstroke or sunstroke 

imminent. 

III Danger Sunstroke, heat cramps, 

or heat exhaustion likely; 

heat stroke possible w ith 

prolonged exposure and 

physical activity. 

II 

Extreme 

Caution 

Sunstroke, heat cramps, 

and heat exhaustion 

possible w ith prolonged 

exposure and physical 

I Caution Fatigue possible w ith 

prolonged exposure and 

physical activity. 

Appare nt 

Temperature 

>130 

105-130 

90-105 

80-90 

33




Based on data from the National Climatic Data Center, there have been 30 incidents of extreme 

heat between January 1995 and June 2010, resulting in 85 deaths, 432 injuries, $30,000 in 

property damage, and $28,000 in crop damage. Some of these events are explained below. 

• High temperatures rose into the mid 90s on 22 August 2002. With dew points in the 

lower to mid 70s, heat index values soared to near 105 degrees during the afternoon. 

Three people died as a result of the excessive heat. In Prince George's County, a 43- 

year old man was found dead in his home on the 22nd. In the city of Baltimore, a 72- 

year old man died in his home on the 22nd and a 74-year old man was found dead in his 

home on the 26th. 

• Excessive heat conditions occurred on Tuesday, Wednesday, and Thursday, 1-3 August 

2006 across much of Maryland. Afternoon heat index values ranged between 105 to as 

high as 115 degrees. Six people lost their lives in Central Maryland due to the excessive 

heat conditions during this heat wave. 

Profile 

In addition to posing a public health hazard, periods of excessive heat usually result in high 

electrical consumption for air conditioning, which can cause power outages and brownouts. The 

elderly, disabled, and debilitated residents of the county are especially susceptible to heat 

stroke. Large and highly urbanized cities can create an island of heat that can raise the area’s 

temperature by 3 to 5° F. Therefore, urban communities with substantial populations of elderly, 

disabled, and debilitated people could face a significant medical emergency during an extended 

period of excessive heat. 

Hydrologic Hazards 

Flash Floods and Flooding 

Overview 

Flash floods, as the name suggests, occur suddenly after a brief but intense downpour, rapid 

melting of ice and snow packs, or failure of natural or manmade dams. Flash floods also result 

as a secondary effect from other types of disasters, including large wildfires that remove 

vegetative cover and alter soil characteristics, increasing the quantity and velocity of storm 

water runoff. . Flash floods are the number one weather-related killer, with approximately 140 

deaths recorded in the United States each year. Flash floods move fast and terminate quickly. 

Although the duration of these events is usually brief, the damages can be quite severe. 

Riverine floods are described in terms of their 

extent (including the horizontal area affected and 

the vertical depth of floodwaters) and the related 

probability of occurrence. Flood studies use 

historical records and hydrological modeling to 

determine the probability of occurrence for 

different extents of flooding. The probability of 

flood occurrence is based on the statistical 

chance of a particular size flood (expressed as 

cubic feet per second of water flow) occurring in 

any given year. The annual flood is usually 

Table 4.7 - Flooding vs. Flash Floods – 

Causes Causes of Flooding Causes of Flash Floods 

Low lying, relatively undisturbed Hilly/mountainous areas 

topography 

High season water tables 

High velocity flows 

Poor drainage 

Short warning times 

Excess paved surfaces 

Steep slopes 

Constrictions – filling 

Narrow stream valleys 

Obstructions – bridges Parking lots & other 

impervious surfaces 

Soil characteristics 

Improper drainage 

considered the single greatest event expected to occur in any given year. On the other hand, 

flash floods cannot be predicted accurately when there are heavy storms (Table 4.7). 

34



The Special Flood Hazard Area (SFHA) is a convenient tool for assessing vulnerability and risk 

in flood-prone communities because many communities have maps available that show the 

extent of the base flood and likely depths that will be experienced. The base flood is often 

referred to as the “100-year flood” By lay persons and officially as the ” one percent annual 

chance flood.” Experiencing a 100-year flood does not 

Table 4.8 - Flood Probability Terms 

mean a similar flood cannot happen for the next 99 

years; rather, it reflects the probability that, over a long Flood 

Chance of occurrence 

period of time, a flood of that magnitude have a 1% Recurrence in any given year 

chance of occurring in any given year. Statically 

10-year 10% 

smaller floods occur more often than larger and more 

50-year 2% 

widespread ones. Table 4.8 shows a range of flood 

100-year 1% 

recurrence intervals and their probabilities of 

500-year 0.20% 

occurrence. So every year, a 10-year flood has a 

greater likelihood of occurring (10% chance) than a 100-year flood (1% chance). 


25 flood events were reported in St. Mary’s County, Maryland between January 1994 and 

December 2010. A few of the recent major flood events are discussed below. 

• On 4 February 1998, a powerful nor'easter, carrying copious moisture from the Gulf of 

Mexico and Caribbean region, dumped between 2 and 4 inches of rain across much of 

Maryland between the foothills of western Maryland and the Chesapeake Bay. Highest 

totals of rainfall, ranging from 3 to 5 inches, fell in lower southern Maryland, causing 

widespread flooding of low lying areas and small streams and creeks. The nor’easter, 

coming on the heels of one just a week earlier, caused tides of 3 to 4 feet above normal 

from the Calvert County/Anne Arundel County line south to Point Lookout in extreme 

southeastern St Mary’s County; and along the lower tidal Potomac River along the 

Charles and St Mary's Counties shoreline, including Cobb Island and St George Island. 

A daily rainfall record was broken at Baltimore/Washington International Airport (BWI); 

the 1.65 inches that fell on the 4th broke the 78 year-old Baltimore area mark of 1.48 

inches. Flooding was most pronounced in St. Mary's County. During the peak of the 

storm, 26 roads were closed due the combination of wind and rain. Nine roads were 

closed due to flooding alone. State thoroughfares affected included Point Lookout Road 

(route 5),and Routes 237, 238, 243, and 271. Evacuations were initiated in Great Mills 

and on St. George Island due to rapid increases in tide levels. At least 200 residents 

were evacuated, including one 3 year-old boy who required a water rescue. Four fire 

fighters were treated for hypothermia at St. Mary's Hospital. Some cars were nearly 

submerged in low-lying areas. In the Golden Beach neighborhood, Lake White spilled 

over its banks, and poor drainage contributed to widespread shallow flooding . The dam 

at St Mary's Lake held; overflow problems were minimal. The sewage system serving 

Lexington Park failed due to the abnormally heavy flow of water which caused manholes 

to flood. The combination of BG&E, PEPCO, and SMECO reported nearly 15,000 

customers without power at the height of the storm. Four thousand SMECO customers 

were affected in St. Mary's County. Property damage was estimated at $650,000. 

• The eye of Hurricane Floyd passed east of the Chesapeake Bay between 9:00 a.m. and 

midnight on 16 September 1999. Gusty winds of 30 to 50 miles per hour blew across the 

area between 11 AM and midnight on the 16th, with localized wind gusts over 50 mph 

near the Chesapeake Bay. Hundreds of trees and power lines were downed and over 

500,000 SMECO customers lost electricity. Between 8 and 12 inches fell across St. 

Mary's, Anne Arundel, and Harford Counties. The amount of damage Anne Arundel, 

Calvert, Charles, Harford, and St. Mary's Counties received from the storm qualified 

35



Profile 

them for FEMA disaster assistance. Tidal flooding was reported along the Chesapeake 

Bay. Strong southerly winds ahead of the hurricane pushed tides 2 to 3 feet above 

normal, flooding several low lying areas in St. Mary's, Calvert, Harford, and Anne 

Arundel Counties. In St. Mary's County, the only causeway to St. George Island went 

underwater, trapping a half dozen residents. High winds blew a cross bar off a church 

steeple and knocked out power to 5000 customers. Winds gusted to 71 mph at Tall 

Timbers, 43 mph at St. Indigoes, and 45 mph at Hollywood. A wind gust of 65 mph was 

recorded at Patuxent River Naval Air Station at 11:45 AM EDT. One location reported 

10.6 inches of rain between 6 a.m. and 4 p.m. EDT on the 16th. Emergency responders 

rescued 28 people by boat from a trailer park, homes, and stranded cars after the St. 

Mary's River and other waterways flooded. Nine other people were rescued from an 

apartment building near Great Mills. Property damage was estimated at $ 500,000. 

• On 9 August 2005, a very moist atmosphere was responsible for thunderstorms 

producing torrential rain and copious localized rainfall. There were a few instances of 

significant localized flooding problems. Water rushed and flooded several buildings at 

the College of Southern Maryland. There were reports from the college that at one time 

there was two feet of water rushing into the basements of the buildings. Many roads 

around the college were flooded. There were several car accidents due to the flooded 

roads, as well as several cars that stalled and had to be recovered with tow vehicles. In 

addition, flooded occurred at the government center in Leonardtown, mainly due to water 

leaking through the roof tiles. 

• On 9 December 2009 an upper level storm system over the Midwest United States 

allowed for abundant moisture from the Gulf of Mexico and Atlantic Ocean to override 

cold air at the surface across the mid-Atlantic. A surface of low pressure developed off 

the coast of North Carolina and moved northward ups the East Coast. With anomalously 

high water content across the region, widespread heavy rainfall with amounts of 1 to 2 

inches prompted areas of flooding St Mary's County in Maryland. 

• On September, 30 and October 10, 2010, the southern tip of Southern Maryland, 

especially St. Mary's County, was hit by heavy rainfall. The National Weather Service 

reported some areas received up to 14 inches of rain in about 20 hours. That amount of 

rain is usually recorded in a three to four month period. The rain event coincided with a 

coastal flood warning for tides 2 to 3 feet above normal. The higher tides left rivers and 

streams swollen by runoff with no outlet and caused flooding of property, homes and 

businesses in Great Mills, Leonardtown and elsewhere in the county. Inspection by 

county officials of a trailer park neighborhood affected by the flash flooding found that 

some residences were unsafe to inhabit, and that in addition to the flood-damaged 

homes, the motion of the elevated water caused a fuel tank leak resulting in a hazardous 

waste condition. Hazmat teams were called in to clean up the area while some 

residents were evacuated and forced to permanently vacate their condemned homes. 

Flash floods are more likely to occur in places with steep slopes and narrow stream valleys, and 

along small tributary streams. Low lying areas adjacent to tidally-influenced streams may also 

experience flash floods during storms when high tide and sustained onshore winds push the 

head of tide upstream and there is no place for freshwater entering the system from storm 

events to go except out onto the floodplain. In urban areas, parking lots and other impervious 

surfaces that shed water rapidly contribute to flash floods. Flash floods could also be a result of 

improper drainage. In rugged, hilly, and steep terrain, the high-velocity flows and short warning 

time make these floods hazardous and very destructive. Many small flash floods are confined 

36



to stream systems and during a majority of storm events. These events drastically alter stream 

channels, eroding and downcutting stream banks and disconnecting them from their floodplains. 

The effect of this is to lower the local groundwater water table (exacerbating localized drought 

conditions near impacted streams and increasing potential for subsidence). These downcut 

channels also deliver increased velocity and quantity of flood waters to downstream areas and 

transport large quantities of sediment. These sediments are eventually deposited in wetlands, 

the floodplain or flushed out of the nontidal system into the tidal system reducing the holding 

capacity of the floodplain, silting over wetlands and grass beds that help to buffer shorelines, 

smothering fish and oyster habitat important to the County economy and reducing the depth of 

navigable waters, Where small streams and swales converge with side channels deep gullies 

can begin to form, particularly within highly erodible soils prevalent in the Patuxent watershed. 

These gullies eventually can work up hill to points of concentration of runoff—frequently building 

downspouts and infrastructure (roads, stormwater management facilities) threatening those 

structures. 

Flood damage to residences can be devastating, both emotionally and financially. Flood 

damage to businesses can result in loss of income, wages, and tax revenues. Other effects 

include outbreaks of diseases, widespread animal illnesses, disrupted utilities, water pollution, 

fire, and washed out roads and culverts. 

Areas of urban development within floodplains are located in a number of areas with pre-FIRM 

development in the county. , These areas include the Great Mills area (within the nontidal 

floodplain of the St. Mary’s River) the St. George island and Piney Point area (within the tidal 

floodplains of the St. Mary’s River, St. George Creek and the Potomac River) and the Hayes 

Beach, Scotland beach and Rodo Beach (along the Chesapeake Bay), and in the Golden Beach 

area off the Patuxent River. There is one dam (St. Mary’s River Watershed Dam, Site 1, on the 

western branch of the St. Mary’s River) located just west of Great Mills with a high downstream 

hazard rating. 

Drought 

Overview 

Drought is a condition of climatic dryness that is severe enough to reduce soil moisture and 

water and snow levels below the minimum necessary for sustaining plant, animal, and economic 

systems. Drought is a complex physical and social process of widespread significance. It is not 

usually a statewide phenomenon, with differing conditions across the State often making 

drought a regional issue. Despite all of the problems that droughts have caused, drought has 

proven to be difficult to define and there is no universally accepted definition because drought, 

unlike floods, is not a distinct event. A drought is often the result of many complex factors such 

that it often has no well-defined start or end and the impacts vary by affected sector; thus, often 

making definitions of drought specific to particular affected groups. 

The most commonly used drought definitions are based on meteorological, agricultural, 

hydrological, and socioeconomic effects: 

• Meteorological drought is often defined by a period of substantially diminished 

precipitation duration and/or intensity. The commonly used definition of meteorological 

drought is an interval of time, generally on the order of months or years, during which the 

actual moisture supply at a given place consistently falls below the climatically 

appropriate moisture supply. 

• Agricultural drought occurs when there is inadequate soil moisture to meet the needs of 

a particular crop at a particular time. Agricultural drought usually occurs after or during 

37



meteorological drought, but before hydrological drought, and can also affect livestock 

and other dry-land agricultural operations. 

• Hydrological drought refers to deficiencies in surface and subsurface water supplies. It is 

measured as stream flow, snow pack, and as lake, reservoir, and groundwater levels. 

There is usually a delay between lack of rain or snow and less measurable water in 

streams, lakes, and reservoirs. Therefore, hydrological measurements tend to lag behind 

other drought indicators. 

• Socioeconomic drought occurs when physical water shortages start to affect the health, 

well-being, and quality of life of the people, or when the drought starts to affect the 

supply and demand of an economic product. 


Data in Table 4.9 reveal that St. Mary’s 

County experienced 10 drought periods 

between January 1950 and June 2010, 

resulting in approximately $50 million in crop 

damage. No fatalities, injuries, or property 

damage was reported. Some of these are 

explained in detail below: 

Table 4.9 - Drought History 

Location Date Type Crop 

Dam age 

St. Mary's County 8/1/1998 Drought 0 


St. Mary's County 11/1/1998 Drought 20.0M 









• Only one other year on record (1930) 

has come close to the lack of rainfall the 

Baltimore area saw from 1 July to 30 

November 1998. The 5 month rainfall 

total at BWI Airport was only 5.79 

inches, compared to the normal average 

of over 17 inches. Officials reported 173 

fires, burning a total of 490 acres during 

this time frame. Several Maryland counties were affected by this drought. From the 

beginning of August to the end of November, the Forest Service recorded 303 fires 


Total Drought 95.0M 

statewide. The fire risk in Maryland during the month averaged 700 on a scale of 0 to 800, 

compared to the normal of 450. The governor declared a statewide ban on outdoor burning 

on 26 November, hoping to significantly reduce the number of fires being accidentally set by 

campers and by field and leaf burning. No property damage was reported. Crop damage to 

Maryland counties was estimated at $20 million. 

• By the third week of August 1999, the Palmer Drought Index, which uses temperature and 

rainfall in a formula to determine drought, indicated Maryland was in an extreme drought. 

The drought warning issued by the Maryland Department of the Environment in December 

remained in effect through the month. August rainfall totals included St. Mary's County at 5.8 

inches. The lack of rainfall through the third week of August continued to affect water levels 

along the Potomac River and the Chesapeake Bay. Nearly 60 communities across the state 

instituted mandatory or voluntary water restrictions. The governor issued statewide 

mandatory water restrictions on 5 September 1999. Nineteen Maryland counties were 

declared Federal drought disaster areas on the 11th. The worst agricultural drought in 

Maryland continued to devastate farmers. St. Mary's County reported a 60 percent loss of 

corn and soybean crops. In addition to agricultural lands, forests and rural vegetation were 

also dangerously dry. The Maryland Department of Natural Resources responded to 600 

fires that burned over 2500 acres from January to July, a 100% increase from the previous 

38



year. No property damage was reported. Crop damage to Maryland counties was estimated 

at $30 million. 

Profile 

Droughts result from prolonged periods of dry weather accompanied by extreme heat and 

usually occur during the summer months (July and August). The warmest time of the year is 

July when maximum temperatures average 89 degrees. Extreme temperatures of 100 degrees 

occur occasionally. The occurrence of drought cannot be predicted. The usual length of time 

does not exceed 6 weeks in mid summer. 

When drought begins, agriculture is usually first to be affected because of its heavy dependence 

on stored soil moisture. Soil moisture can be rapidly depleted during extended dry periods. Dry 

land farming and ranching are the most at risk from drought. Water uses depending on instream 

flows, such as irrigated farms; aquatic, wetland, and riparian environmental 

communities; and recreational uses are at high risk but less exposed. Urban and agricultural 

water users who rely on reservoirs and wells that are not dependent on high rates of aquifer 

recharge are the last to feel the effects of drought. 

As the County’s Comprehensive Plan indicates, agriculture remains a leading and vital sector of 

St. Mary’s County's economy. St. Mary’s County contains approximately 231,280 acres of land 

area. The 2007 land use analysis from the MDP shows that 52.5 percent is in a forest use 

(including forest on large residential lots) and 23.7% is in an agricultural use (including 

agricultural lands on large residential lots). The 2007 Census of Agriculture counted 68,648 

acres of land in farms (includes hay, pasture, crop and forested lands) in St. Mary’s County, 

which was a slight increase from 68,153 acres in 2002 but which was still down from 71,920 

acres in 1997. The number of farms declined during the period from 1997 (658 farms) to 2002 

(577 farms), but that trend had reversed by 2007 with an increase to 621 farms. 

Though the agricultural industry has continued to adapt to market and population forces, a 

number of factors have helped to generate a perception of impermanence in St. Mary’s 

County’s agricultural industry, similar to other counties in the state. The realities of higher land 

costs to purchase additional crop or pasture land, greater difficulties in obtaining long-term 

leases, labor shortages, increased wage scales, traffic congestion, loss of nearby agricultural 

support industries, and the influx of non-agricultural neighboring uses are attributed to the 

agriculture industry’s transition. 

Coastal/Shoreline Erosion 

Overview 

Erosion and accretion are long-term, dynamic processes that occur along shorelines. Major 

erosion/accretion events are usually associated with coastal storms because floodwater forces 

have the ability to cause significant acts of erosion/accretion in a short time period. Erosion is 

considered a serious hazard in coastal areas because it can threaten coastal development by 

eroding beach areas, including the flat berm portion and protective dunes. In general, shore 

erosion poses a significant threat to property owners, the public, and natural resources, both 

terrestrial and aquatic. 

History Activity 

• On 6 September 1996, Tropical Storm Fran allowed gusty southeast winds at and just 

above the surface to channel water up the Chesapeake Bay and its main tributaries. This 

became a small-scale storm surge, containing 6-foot waves and tides that ran in some 

places nearly 6 feet above normal. Damage was fairly heavy along the immediate shore of 

the Chesapeake Bay and tidal Potomac River in Charles, St. Mary's, Calvert, and Anne 

39



Arundel Counties. Damage was notable, but substantially less in St. Mary's County. 

Property damage incurred in Maryland counties totaled $100,000. 

• As previously mentioned, the eye of Hurricane Floyd passed east of the Chesapeake Bay 

between 9:00 a.m. and midnight on 16 September 1999. Between 8 and 12 inches fell 

across St. Mary's County. The amount of damage Anne Arundel, Calvert, Charles, Harford, 

and St. Mary's Counties received from the storm qualified them for FEMA disaster 

assistance. Tidal flooding was reported along the Chesapeake Bay. Strong southerly winds 

ahead of the hurricane pushed tides 2 to 3 feet above normal, flooding several low-lying 

areas in St. Mary's, Calvert, Harford, and Anne Arundel Counties. Erosion was reported on 

the South River and Broad Creek. In St. Mary's County, the only causeway to St. George 

Island went underwater, trapping a half dozen residents. Tropical downpours also led to 

flooding. County emergency responders rescued 28 people by boat from a trailer park, 

homes, and stranded cars after the St. Mary's River and other waterways flooded. 

Profile 

The County shoreline along the Patuxent River has very steep eroding slopes and the western 

shore of the Chesapeake Bay varies from steep, eroding cliffs to stable slopes. Cliffs are 

continually eroded by wave action, landslides, groundwater seepage, freeze/thaw action, and 

weathering. All shorelines in the county are subject to the effects of erosion. The most severe 

impacts occur along those shorelines with the longest fetch or exposed distance over water in 

front of the shore. Although erosion is a natural process, it can create significant problems for 

property owners, businesses, and the public, especially when inappropriate planning and design 

activities either increase natural erosion rates or compound the impact of natural erosion 

processes. The Maryland Geological Survey (MGS) began to quantify the problem in 1914, 

documenting major reductions of various islands throughout the state. 

A large percentage of St. Mary’s County’s shorelines incur erosion accelerated by high winds 

and high tides. The greatest numbers of incidences occur during the fall and winter months. 

Additionally, damaging wind events coupled with abnormally high tides cause shoreline erosion 

to occur each year. Studies cited in the Maryland Department of Natural Resources (DNR) 

Coastal atlas estimate that 80 percent of the Maryland’s 7,660 miles of tidal shoreline currently 

experience some degree of erosion, and approximately 76 percent of St. Mary’s County’s 538 

miles of shoreline currently experience some degree of erosion. According to DNR, 

approximately 371 miles of the shoreline experience more than 0 but less than 2 feet of erosion, 

24 miles experience between 2 and 4 feet per year, and 10 miles experience greater than 4 feet 

of erosion per year. 

Category 1 hurricane surge areas are located along the entire shore of the Bay, most of the 

Potomac River, and along the Patuxent River. Point Lookout, the area around Piney Point/St. 

George Island and Colton’s Point are most at risk from Category 1 storm surge and more 

extensive flooding from a Category 4 hurricane storm surge. In addition, the area around 

Chaptico Bay and Chaptico Run are areas prome to flooding from storm surge. 

Based on historical trends, the probability of shoreline erosion continuing in St. Mary’s County is 

high. In addition, as the shoreline continues to erode, more and more built structures will 

continue to lose their existing yards, septic fields and the setback, which protects the structure 

from possible landslides or eventual collapse as the soil around the foundation is eroded away. 

40



Wildfires and Urban Interface Fires 

Overview 

A wildfire is an uncontrolled fire spreading through vegetative fuels, such as brush, marshes, 

grasslands, or field lands, exposing and possibly consuming structures. They often begin 

unnoticed and spread quickly and are usually signaled by dense smoke that fills the area for 

miles around. Wildfires may also be called forest fires. For the purpose of this analysis, the 

term wildfire will be used. The causes of these fires include lightning, human carelessness, and 

arson. 

An urban-wildland 

interface fire is a 

wildfire in a 

geographical area 

where structures and 

other human 

development meet or 

intermingle with 

wildland or vegetative 

fuels. Fires can be 

rated based on their 

degree of combustion 

as noted in Table 4.10. 

Table 4.10 - Fire Danger Rating Descriptions 

Rating 

Low 

Moderate 

High 

Description 

Fuels do not ignite readily from small firebrands although a more intense heat source, such as 

lightning, may start fires in duff or punky wood. Fires in open cured grasslands may burn freely for a 

few hours after rain, but woods fires spread slowly by creeping or smoldering, and burn in irregular 

fingers. There is little danger of spotting. 

Fires can start from most accidental causes, but with the exception of lightning, the number of fires is 

generally low. Fires in open cured grasslands will burn briskly and rapidly on windy days. Timber 

fires spread slowly to moderately fast. The average fire is of moderate intensity, although heavy 

concentrations of fuel, especially draped fuel, may burn hot. Short-distance spotting may occur, but 

is not persistent. Fires are not likely to become serious and control is relatively easy. 

All fine dead fuels ignite readily and fires start easily from most causes. Unattended brush and 

campfires are likely to escape. Fires spread rapidly and short-distance spotting is common. Highintensity 

burning may develop on slopes or in concentrations of fine fuels. Fires may become serious 

and their control difficult unless they are attacked successfully while small. 


Very High 

Data from the 

Maryland Department of Natural Resources Fire Service, 

Southern Region Fire Center indicates a total of 982 fires 

occurred in the County between 1985 and 2009, 

damaging approximately 873 acres. The largest number 

of fires occurred in 1995 (79 fires), which damaged over 

100 acres of land within St. Mary’s County. Each year 

there has been property damage including outbuildings, 

automobiles, boats, propane tanks, fences, and porch 

decks. Although houses were threatened by these 

wildfires, they were all saved. 

Fires start easily from all causes and immediately after ignition, spread rapidly and increase quickly in 

intensity. Spot fires are a constant danger. Fires burning in light fuels may quickly develop intensity 

characteristics such as long-distance spotting and fire whirlwinds when they burn into heavier fuels. 

Table 4.11 - History of Fires in St. 

Mary’s County 

Year No. of Fires Acres 

1990 11 11.3 

1991 45 59.9 

1992 64 34.2 

1993 35 19.5 

1994 45 72 

1995 79 104.1 

1996 22 10.2 

1997 35 21.8 

1998 40 30.9 

1999 61 52.8 

2000 17 10.6 

2001 59 40.4 

2002 57 32.8 

2003 9 4.5 

2004 23 23.8 

2005 25 9.9 

2006 55 12.7 

2007 71 66.7 

2008 36 12.8 

2009 35 18.5 

41



Profile 

Wildfires can occur at any time of day and during any month of the year, and the season length 

and peak months may vary appreciably from year to year. Land use, vegetation, amount of 

combustible materials present, and weather conditions such as wind, low humidity, and lack of 

precipitation are the chief factors influencing the number of fires and acreage burned. Generally, 

fires are more likely when vegetation is dry from a winter with modest snow and/or a spring and 

summer with sparse rainfall. Wildfires are capable of causing significant injury, death and 

damage to property. The potential for property damage from fire increases each year as more 

recreational properties are developed on wooded land and increased numbers of people use 

these areas. Fires can extensively impact the economy of an affected area, especially the 

logging, recreation and tourism industries. Major direct costs associated with forest fires or 

wildfires are the salvage and removal of downed timber and debris and the restoration of the 

burned area. If burned-out woodlands and grasslands are not replanted quickly to prevent 

widespread soil erosion, landslides, mudflows and floods could result, compounding the 

damage. 

Figure 4.6 - Fire Threat Potential in Maryland Counties 

The graphic in Figure 4.7 indicates that St. 

Mary’s County has approximately 47 

percent of its land delineated as forested 

lands. Although Maryland averages 5,000 

wildfires a year, which consume 8,000 to 

9,000 acres of forest, marsh, and 

grasslands, St. Mary’s County has not 

experienced any wildfire events in the past 

few years. This can be partly attributed to 

the burning regulations and public 

education on preventing forest fires. 

According to the DNR, the urbanwildland 

interface fire threat 

potential to the St. Mary’s County 

forestlands is considered very high 

(Figure 4.6), due to the pressures 

to convert large tracts of open land 

for development. The probability of 

wildfires in St. Mary’s County would 

also be tied to periods of prolonged 

drought when forests are more 

vulnerable to ignite from lightning 

strikes or human carelessness or 

arson. Other contributing factors 

would include the buildup of dead 

underbrush from fallen trees and 

limbs following severe storms, 

hurricanes, ice storms, or 

tornadoes. 

Figure 4.7 - Forested Areas in Maryland Counties 

42



Geologic Hazards 

Earthquakes 

Overview 

An earthquake is a shaking or sometimes violent trembling of the 

earth those results from the sudden shifting of rock beneath the 

earth's crust. This sudden shifting releases energy in the form of 

seismic waves or wave-like movement of the earth's surface. 

Earthquakes can strike without warning and may range in intensity 

from slight tremors to great shocks. 

Earthquakes are measured by two principal methods: seismographs 

and human judgment. The Modified Mercalli Intensity Scale is an 

intensity scale expressed in Roman numerals, which reports the 

amount of shaking and effects at a 

specific location based on expert 

judgment. The scale has twelve 

classes and ranges from I (not felt) 

to XII (total destruction). Table 4.12 

shows a comparison for scales of 

magnitude and intensity. 

The seismograph measures the 

magnitude of an earthquake and 

interprets the amount of energy 

released on the Richter scale. An 

earthquake measuring 6.0 on the 

Richter scale is ten times more 

powerful than a 5.0 and one 

hundred times more powerful than 

an earthquake measuring 4.0. This 

is a measure of the absolute size 

or strength of an earthquake and 

does not consider the effect at any 

specific location. 

Another way of measuring the 

potential damage of an earthquake 

is the peak ground acceleration 

(PGA). The PGA is measured as a 

percentage and refers to the 

maximum percentage of 

acceleration of the movement of 

the ground. A higher PGA means a 

more rapid movement of the 

ground and a higher probability of 

structural damage. Table 4.13 

Table 4.12 – Earthquake Magnitude 

and Intensity Scales 

provides a comparison between the Modified Mercalli Intensity (MMI) scale and peak ground 

acceleration. 

Source: USGS (Excerpted from FEMA Publication 386-2, “Understanding Your Risks”, August 2001. 

MMI 

Acceleration 

(%g) PGA 

Perceived 

Shaking 

Potential 

Damage 

I 124 Extreme Very Heavy 

Table 4.13 - Modified Mercalli Intensity Scale and Peak Ground 

Acceleration Comparison 

Magnitude 

(Richter) 

Inte ns ity 

(M e rcalli) 

Description 

1.0 – 3.0 I I. Not felt except by a very few under especially favorable 

c onditions . 

3.0 – 3.9 II – III II. Felt only by a few persons at rest, especially on upper floors 

of buildings. 

III. Felt quite noticeably by persons indoors, especially on upper 

floors of buildings. Many people do not recognize it is an 

earthquake. Standing motorcars may rock slightly. Vibrations 

similar to the passing of a truck. Duration estimated. 

4.0 – 4.9 IV – V IV. Felt indoors by many and felt outdoors by few during the 

day. At night, some aw akened. Dishes, w indow s, doors 

disturbed; w all make cracking sound. Sensation like heavy 

5.0 – 5.9 VI – VII 

truck striking building. Standing motorcars rocked noticeably. 

VI. Felt by all, many frightened. Some heavy furniture moved; a 

few instances of fallen plaster. Damage slight. 

VII. Damage negligible in buildings of good design and 

construction; slight in w ell-built ordinary structures; 

considerable damage in poorly built or badly designed 

structures. Some chimneys broken. 

6.0 – 6.9 VIII – IX V III. Damage s light in s pec ially des igned s truc tures ; 

considerable damage in ordinary substantial buildings w ith 

partial collapse. Damage great in poorly built structures. Fall of 

chimneys, factory stacks, columns, monuments and w alls. 

Heavy furniture 

IX. Damage c ons iderable in s pec ially des igned s truc tures ; w elldesigned 

frame structures throw n out of plumb. Damage great 

7.0 and 

higher 

X or higher 

in substantial buildings, w ith partial collapse. Buildings 

foundations shifted. 

X. Some w ell-built w ooden structures destroyed; most masonry 

and frame structures destroyed w ith foundations. Rails bent. 

XI. Few , if any (masonry) structures remain standing. Bridges 

destroyed. Rails bent greatly. 

XII. Damage total. Lines of sight and level are distorted. 

Objects throw n into the air. 

Source: United States Geographical Survey National Earthquake Information Center 

43




No earthquake incidents have been recorded in St. Mary’s County since 1960. 

Profile 

Earthquakes can last from a few seconds to over 5 minutes and they may also occur as a series 

of tremors over a period of several days. The actual movement of the ground in an earthquake 

is seldom the direct cause of injury or death. Casualties may result from falling objects and 

debris, because the shocks shake, damage, or demolish buildings and other structures. 

Disruption of communications, electrical power supplies and gas, sewer, and water lines should 

be expected. Earthquakes may trigger fires, dam failures, landslides, or releases of hazardous 

material, compounding their disastrous effects. 

Landslides 

Overview 

Landslides include a wide range of ground movement, such as rock falls, deep failure of slopes, 

and shallow debris flows. Although gravity acting on an over steepened slope is the primary 

reason for a landslide, there are other contributing factors: 

• Erosion by rivers, glaciers, or ocean waves creates over-steepened slopes. 

• Rock and soil slopes are weakened through saturation by snowmelt or heavy rains. 

• Earthquakes create stresses that make weak slopes fail. 

• Earthquakes of magnitude 4.0 and greater have been known to trigger landslides. 

• Volcanic eruptions produce loose ash deposits, heavy rain, and debris flows. 

• Excess weight from accumulation of rain or snow, stockpiling of rock or ore from waste 

piles or from man-made structures may stress weak slopes to failure. 

Slope material that becomes saturated with water may develop a debris flow or mud flow. The 

resulting slurry of rock and mud may pick up trees, houses, and cars, thus blocking bridges and 

tributaries causing flooding along its path and upstream of the blockages. Landslides occur in 

every state and U.S. territory. The Appalachian Mountains, the Rocky Mountains, the Pacific 

Coastal Ranges, and some parts of Alaska and Hawaii have severe landslide problems. Any 

area composed of very weak or fractured materials resting on a steep slope can and will likely 

experience landslides. 

Landslides are often prompted by the occurrence of other disasters. Floods or long duration 

precipitation events create saturated, unstable soils that are more susceptible to failure. The 

forces of earthquakes can also cause landslides. 


No records of major landslides have been found for St. Mary’s County since 1950. 

Minor slides have occurred along the Patuxent scarps due to toe erosion and , freeze thaw of 

groundwater acting to loosen soils. The weight of development can also cause collapse of the 

cliff face. Localized slides have occurred along the Potomac River on areas underlain by a 

deposit of Blue Marl clay. These areas have been typically occupied by farm fields and forest 

but as the shoreline has developed, the weight of the development, including the weight of 

stone revetments intended to protect the shore from erosion, has caused the Blue Marl to slide 

out into the river and the shoreline and structures above the clay deposits to slide down and out 

toward the river. 

44



Profile 

Landslides constitute a major geologic hazard because they are widespread, occurring in all 50 

states, and cause $1-2 billion in damages and average more than 25 fatalities on average each 

year. Landslides pose serious threats to highways and structures that support fisheries, tourism, 

timber harvesting, mining, and energy production as well as general transportation. Landslides 

commonly occur with other major natural disasters such as earthquakes and floods that 

exacerbate relief and reconstruction efforts. Expanded development and other land use has 

increased the incidence of landslide disasters. 

Landslides are common throughout the Appalachian region and New England. The greatest 

eastern hazard is from sliding of clay-rich soils; related damages in urban areas such as 

Pittsburgh, PA, and Cincinnati, OH, are among the greatest in the U.S. Landslides also occur 

across the Great Plains and into the mountain areas of the western U.S. in weathered shales 

and other clay-rich rocks, particularly where there are steep slopes, periodic heavy rains, and 

vegetation loss has occurred after wildfires. Earthquakes and volcanoes also cause landslides; 

the catastrophic 1980 eruption of Mount St. Helens in Washington State was preceded by the 

development of a large landslide on the north side of the volcano. The 1994 Northridge 

earthquake in the San Fernando Valley triggered thousands of landslides in the Santa Susanna 

Mountains north of the epicenter. 

Based on the Landslide map from the United States Geological Survey, St. Mary’s County is in 

an area of high susceptibility and moderate incidence (Figure 4.8). Note: Susceptibility is not 

indicated where same or lower than incidence. Susceptibility to landslide was defined as the 

probable degree of response of [the area] rocks and soils to natural or artificial cutting or loading 

of slopes, or to anomalously high precipitation. High, moderate, and low susceptibility are 

delimited by the same percentages used in classifying the incidence of landslides. Some 

generalization was necessary at this scale, and several small areas of high incidence and 

susceptibility were slightly exaggerated. 

Figure 4.8 - Landslide Incidence/Susceptibility for the Northeastern United States 

45



Land Subsidence 

Overview 

Figure 4.9 - Landslide Subsidence in the United States 

Land subsidence occurs when large 

amounts of groundwater have been 

withdrawn from certain types of rocks, 

such as fine-grained sediments. The 

rock compacts because the water is 

partly responsible for holding the 

ground up. When the water is 

withdrawn, the rock falls in on itself. 

Common causes of land subsidence 

from human activity are pumping 

water, oil, and gas from underground 

reservoirs; dissolution of limestone 

aquifers (sinkholes); collapse of 

underground mines; drainage of 

organic soils; and initial wetting of dry 

soils (hydrocompaction). Land 

subsidence occurs in nearly every 

State of the United States (Figure 4.9). 


While no major historic activity has 

been reported in the County, naturally 

occurring regional land subsidence is 

occurring throughout Maryland and the 

Chesapeake Bay region. This 

subsidence is mostly a result of 

postglacial rebound or readjustment 

(sinking) of land elevations since the retreat of the glaciers at the end of the last ice age. 

Subsidence data included in the report of the Maryland Commission on Climate Change 

Adaptation and Response Working Group shows that St Mary’s County is within an area that 

has experienced nearly 8 inches of subsidence in the last century. This subsidence combined 

with rise in tidal waters has resulted in 1.08 feet of sea level rise reported by the National 

Oceanic and Atmospheric Administration ( NOAA) for the tidal gauge in Solomon’s Island 

measured between 1937 and 1999. 

Localized sink holes have occurred in areas with highly erodible soils—particularly in the 

Patuxent River watershed where subsurface waters have undermined and flowed around rather 

than through underground drainage structures carrying away the surrounding erodible subsoil. 

Land subsidence in the Patuxent watershed typically is often treated as an erosion event since, 

due to the steep terrain, sink holes that form intersect the slope and result in formation of large 

gullies with sediment deposited in streams, wetlands and tidal creaks. A relatively large sink 

hole formed and caused a portion of the northbound lane of Three Notch Road to collapse in the 

vicinity of Woodlake requiring an extensive fill and repair project by Maryland State Highway 

Administration. 

Profile 

Land subsidence is usually not observable as it occurs because it occurs over a large area. 

When land subsidence is isolated in a small area, they appear as a sinkhole. In areas where 

46



climate change results in less precipitation and reduced surface-water supplies, communities 

will typically pump more ground water. In the southern part of the United States from states on 

the Gulf Coast and westward including New Mexico, Colorado, Arizona, Utah, Nevada and 

California, major aquifers include compressible clay and silt that can compact when 

groundwater is pumped. Land subsidence is a significant problem in California, Texas, and 

Florida, all of which have experienced hundreds of millions of dollars of damage over the years. 

However, parts of western Maryland have also begun to experience sinkholes as a common 

natural hazard. 

Summary of Events 

Based on Table 4.14, the county 

has experienced approximately 

215 natural hazards events 

since 1950. These events 

include atmospheric, wildfire, 

and hydrologic hazards. 

Thunderstorms are the most 

common occurring hazards in 

the county, followed by hail, 

winter storms, and extreme heat 

events. 

The total property damage in 

the County from these hazards, 

the bulk of which were from the 

hurricanes/tropical storms, was 

almost $ 593.23 million and total 

crop damage was approximately 

$428,000,. 

Of the 13 hazards assessed, the 

following six were considered to 

be high risk hazards in St. 

Mary’s County. These included 

the following: 

Table 4.14 - Summary of Hazard Events 1950 – 2010 

Hazard Event Total Events Death Injured Property Damage Crop Damage 

Atmospheric 

Thunderstorms 125 0 9 $ 1.01 million $ 5,000 

Lightning 13 0 0 $402,000 $ - 

Tornadoes 18 0 4 $ 4.06 million $ 205,000 

Hurricanes 2 1 200 $ 531.4 million $ 190,000 

Hail 27 0 0 $12,000 $ - 

Winterstorms 16 2 11 $ 5.58 million $ - 

Ex treme Heat 24 76 427 $30,000 $ 10,000 

Ex treme Cold 5 0 0 $0 $ 18,000 

Wildfires 

Wildfires/Urban Interface 982 na na na na 

Hydrologic 

Flood/flashfloods 25 0 0 $1.45 million $ - 

Drought 12 0 0 0 $50.04million 

Erosion na na na na na 

Earthquakes 0 0 0 0 0 

Landslide/Land Subsiden 0 0 0 0 0 

Total 215 79 651 $ 593.23 million $ 428,000 

• Coastal/shoreline erosion due to the increasing number of structures that may be at risk in 

the next 10 to 25 years. This was identified as a major concern for the county after 

Hurricane Floyd, Tropical Storm Isabel. 

• Flooding due to the frequency of floods that has historically affected the county on average 

of once every 2 years. 

• Hurricanes/tropical storms based on the number of events that have passed with 50 miles of 

county in the past 118 years. The frequency of occurrence for all events was estimated at 

one event occurring every 3 years and an event of F1 or greater magnitude occurring every 

39 years. 

• Severe storms because thunderstorms affect the county in some way each year. 

• Winter storms on average affect the county in some way each year and occur on a larger 

magnitude of impact approximately every 2 years. 

47



• Tornadoes because the county has experienced an average of one every 3 years. 

Four hazards were assigned a risk rating of moderate: hail, extreme heat, drought and lightning. 

The moderate rating indicated that a number of events have been documented in St. Mary’s 

County, but their historic rate of occurrence placed them at a lower priority for the county than 

the hazards listed as high risk. The remaining three hazards (earthquakes, landslide, land 

subsidence, and wildfires) were assigned a risk rating of low for St. Mary’s County. The low 

rating indicated that either no documented events have occurred in the county, or in the case of 

earthquake, the documented events did not result in structural damages in the county. The low 

risk rating does not mean that these hazards cannot occur in the future nor does it mean that, if 

a hazard occurred that it would not result in any damages or injuries. 

Conclusions 

Based on the hazard history and profiles of the aforementioned hazards, the hazard frequency 

for St. Mary’s County was determined (Table 4.15). This was achieved by reviewing the 

National Climate Data Center Query results for the last 50 years. The hazard frequency was 

calculated by dividing the number of events observed by the number of years. For example, 46 

hailstorms divided by 60 years indicated that an average of.76 hailstorms occur in St. Mary’s 

County in any given year. 

The natural hazards addressed in this section have been ranked as low, medium, or high 

priority (Table 4.16). The hazards have been prioritized based on several factors including the 

frequency of occurrence, amount of damage caused, potential for significant damage, and the 

community’s interest in the hazard. Of the hazards, the high priority hazards such as hurricane 

wind, tornadoes, winter storms, and floods, will be assessed in the following chapter for their 

vulnerability. Hazards such as hail, extreme heat, drought, erosion, and lightning have been 

categorized as medium priority hazards, and earthquakes, and landslides/land subsidence and 

wildfires have been characterized as low priority hazards based on their infrequent occurrence. 

Table 4.15 – Frequency of Occurrence 

Hazard Total Events Years in Freq/Prob 

Record per Year 

Atmospheric Hazard 

Thunderstorms 125 60 2.08 

Lightning 16 60 0.26 

Tornadoes 18 60 0.30 

Hurricanes 3 60 0.05 

Hailstorm 46 60 0.76 

Winterstorms 40 60 0.67 

Extreme Heat 111 60 1.85 

Extreme Cold 33 60 0.55 

Wildfire Hazard 

Wildfires 982 25 39.28 

Hydrologic Hazard 

Flood/flashfloods 25 60 0.42 

Drought 12 60 0.20 

Erosion na na na 

Geologic Hazard 

Earthquakes 0 0 0 

Landslides/Land subsidence na na na 

Table 4.16 – Hazard Probability of Occurrence 

High Priority M edium Priority Low Priority 

Thunderstorms Hail Earthquakes 

Tornadoes Extreme Heat Landslide/Land Subsidence 

Hurricanes Drought Wildfires 

Winterstorms Lightning 

Flood 

Eros ion 

48

Chapter 4: Goals and Objectives 


CHAPTER 3 – VULNERABILITY ANALYSIS 

Overview 

A vulnerability assessment is performed to determine the impact that hazards have on the built 

environment and how they can negatively affect people’s safety. The results of the Hazard 

Identification indicate that some hazards warrant a vulnerability assessment. For those natural 

hazards with a relatively short frequency of occurrence or those which have caused major 

damage in St. Mary’s County, a vulnerability assessment was deemed appropriate. Therefore, 

the effects of flooding, erosion, wind related events (thunderstorms, tropical storms, and 

tornadoes), and wildfires will be analyzed. 

Development Trends 

To understand the vulnerability of the built environment an analysis of the County’s 

development trends is necessary. This allows us to focus on where and what type of future 

development will occur and determine how to fortify it to be hazard-resistant. 

Development Trends 

The Lexington Park Development District serves as a destination and a focus for St. Mary’s 

County, offering a mix of governmental, retail, office, residential, entertainment, and recreational 

uses. The Patuxent River Naval Air Station is the pride of Lexington Park. Commercial uses are 

concentrated primarily in Leonardtown and Lexington Park, and in the town and village centers. 

The county’s Comprehensive Plan discusses promoting development of designated traditional 

rural service centers, Budds Creek, Oraville, Helen, Avenue, St. James, Dameron, and Park 

Hall. The county also has plans to encourage expansion of rural services and moderate 

residential growth in the seven village centers: Callaway, Chaptico, Clements, Loveville, Ridge, 

St. Inigoes, and Valley Lee. 

Population Trends 

Table 5.1 - Population Change 

The geographical size of St. Mary’s Jurisdiction 1960-1970 1970-1980 1980-1990 1990-2000 2000-2010 

County is approximately 373 square 

State of Maryland 21.0% 7.0% 11.8% 9.7% 9.1% 

miles and contains 15 census tracts. Calvert County 23.5% 40.3% 32.6% 31.1% 23.1% 

In 2000, the County’s total population Charles County 31.7% 34.5% 28.1% 16.1% 20.2% 

was 86,211 people with 30,642 

St. Mary's County 17.9% 20.9% 21.2% 13.5% 22.3% 

households. The Maryland 

Department of Planning (MDP) estimated that there were 35,050 households in 2005 

households with a population of 96,450 and MDP projects that the county will have 

approximately 38,875 households with a population of105,400 in 2010. The increase from 1990 

to 2000 was considerably, smaller than the increase in population in Charles and Calvert 

Counties during the same period, but the growth rates during the period from 2000 to 2010 of 

the three counties are now much closer (Table 5.1).. 

Land Use Trends 

As of 2007, the majority of the County’s land (52.5 percent) was in forest use. Agricultural land 

accounted for 23.7 percent of the total land use. Developed land increased from 16 percent to 

28 percent from 1985 to 1997. Most of the lost forest and agricultural land was converted to low 

density residential use. Between 1996 and 2001, nearly 2,700 dwelling units were built on 

8,500 acres. Residential growth, while ubiquitous, has been concentrated in a broad swath 

between Leonardtown and Lexington Park, and in the northern third of the County centered on 

the Charlotte Hall and Mechanicsville town centers. The rural preservation district has typically 

captured a slight majority of new housing units, but the targeted growth areas have captured 

49



nearly all townhouse and multi-family residential development. The county has put strong 

measures into place to direct new single-family units to the growth areas, but this type of 

housing will continue to be located on existing vacant rural parcels and in new clustered 

developments within the rural preserve. 

Non-residential development has occurred principally in the Lexington Park Development 

District within a narrow corridor on either side of major roads, especially Three Notch Road 

(MD235) and Great Mills Road (MD246). The northern town centers of Charlotte Hall and 

Mechanicsville have attracted non-residential development within a narrow corridor on either 

side of Three Notch Road (MD5) to a lesser extent. The town centers of Piney Point and 

Hollywood are targeted for this type of land use, but growth has been slow. 

Within Leonardtown, the County Seat, there has been a steady growth in jobs and facilities 

associated with law and government, the hospital, and the Leonardtown campus of the College 

of Southern Maryland. These trends are expected to continue. Leonardtown has accomplished 

revitalization of a public wharf which is attracting business and residential growth. In addition to 

non-residential activities, home occupations and agri-business; roadside stands, and farmers 

markets continue to occur. 

Building Inventory 

The 2009 Maryland Department of Assessments and Taxation Property View database and 

building polygon data developed from 2007 aerial photography was used to analyze the 

County’s building inventory. Per Maryland Property View, there are 47,500 parcels which 

provide over 52,000 dwelling units (single family, condominiums, townhouse and apartments). 

Fair Market Value of the structures is $1.8 billion (2009 dollars) and the total building 

replacement cost (including contents) was estimated per FEMA guidance at $3.5 billion (2009 

dollars). Losses associated with function and services and costs for displacement are not 

included in the analysis. The impervious coverage layers, drawn using 2007 aerial photographs 

and identify 37,064 buildings and another 45,547 structures (sheds barns, garages) 

demonstrates that losses would likely be even greater than can be estimated from the available 

Maryland Property view information. 

Table 5.2 - Building Count and Exposure by Use 

Asset Number Value of Structures ($) Source 

People 101,808 MDP estimate for 2010 

Structures in 2007 82,611 SMC GIS Data 

Fair market value in 

Parcels Dwellings FMV of Structures ($) 

Agricultural 2,607 2,770 $318,046,850 MD. PropertyView '09 

Residential 41,825 46,091 $505,471,980 MD. PropertyView '09 

Commercial 2,845 3,168 $891,654,460 MD. PropertyView '09 

Industrial 82 1 $84,458,300 MD. PropertyView '09 

Exempt 140 124 $19,380,540 MD. PropertyView '09 

Totals 47,499 52,154 1,819,012,130 MD. PropertyView '09 

Infrastructure and 

Lifelines 

Critical Facilities Number Value of Structures ($) Source 

Dams 1 MEMA 

Airports 1 $ 219,500 MD. PropertyView '03 

Fire Stations 17 $ 10,806,050 MD. PropertyView '03 

Police Stations 2 $ 1,130,400 MD. PropertyView '03 

Schools 40 $ 222,342,970 Board of Ed./MDPV '03 

Hospitals/Health Related 

20 $ 36,679,250 MD. PropertyView '03 

Facilities 

Total Critical Facilities 81 $ 

271,178,170 

50



Data for these structures was not available by Table 5.3 - Building Count and Exposure by 

building type in 2003 and information is still 

B u ild in g T y p e 

% o f T o t a l 

unavailable for 2007 therefore a new HAZUS 

W ood 58.9% 

update was not run for the 2007 data. As 

Masonry 28.0% 

reported in the 2006 Hazard Plan, information Concrete 3.9% 

from the HAZUS database categorized 

Steel 7.6% 

structures by construction type (Table 5.3). 

Manufactured Homes 1.6% 

Steel and reinforced masonry structures are Total 100.0% 

considered strong and more resistant to the 

forces of nature, while wood and unreinforced masonry structures are more vulnerable to high 

wind and other hazards. Approximately 59 percent of the county’s building stock is wood 

structures. Masonry buildings constitute 28 percent of buildings. Steel buildings comprise 7.6 

percent of the total building stock, and manufactured housing approximately 1.6 percent. 

Critical Facilities Inventory 

Critical facilities are those facilities that warrant special attention in preparing for a disaster 

and/or facilities that are of vital importance to maintaining citizen life and health safety, and 

community order during and/or directly after a disaster event. In order to assess the vulnerability 

of the community, particularly to natural hazards, an inventory of the county’s structures and 

critical facilities was performed. ArcVIEW shape files were provided by the County’s GIS 

department containing data about existing structure locations, land use, streams, transportation 

network, and the 100-year floodplain. 

The St. Mary’s County inventory of critical facilities includes emergency response facilities such 

as police stations and fire stations; hospitals and nursing homes; schools; local government 

buildings; and important transportation facilities including airports. A count of the types of 

facilities in St. Mary’s County is provided in Table 5.4, based on information provided by the 

County’s Department of Land Use and Growth Management. A total of 40 school buildings, 17 

fire stations and rescue squads, 20 hospitals and health related facilities, and 2 police 

departments with multiple structures are located in St. Mary’s County. The total value of these 

facilities is estimated at approximately $271 million. In addition to these, are the SMECO substations, 

water treatment/pumping stations, and emergency operation centers. The Patuxent 

River Naval Air 

Station is also 

Table 5.4 - Critical Facilities Count and Exposure 

considered a critical 

Critical Facilities Number Value of Structures ($) Source 

facility. 

The county’s 

primary evacuation 

routes should be 

inventoried as a 

part of the critical 

facilities inventory, 

since the response 

to natural disasters 

may depend on the 

Dams 1 MEMA 

Airports 1 $ 219,500 MD. PropertyView '10 

Fire Stations 17 $ 10,806,050 MD. PropertyView '10 

Police Stations 2 $ 1,130,400 MD. PropertyView '10 

Schools 40 $ 222,342,970 Board of Ed./MDPV '03 

Hospitals/Health 

Related Facilities 

20 $ 36,679,250 MD. PropertyView '10 

Total Critical 

Facilities 81 $ 271,178,170 

ability to ingress/egress via all or part of the county’s transportation network. The county-wide 

transportation plan adopted in 2006 addresses this issue. 

Impacts of Population, Buildings, and Critical Facilities 

51



After the critical facilities were identified and mapped, their vulnerability to various hazards was 

assessed. Based on the hazard event profile that was described in the previous chapter, GIS 

data were used to determine the total number of structures as well as the critical facilities that 

are potentially vulnerable to specific hazards. Hazards such as tornadoes and severe storms 

are not mapped at the county level because they are likely to impact the entire county or 

undefined locations within the county. As such, the entire county must be considered 

vulnerable to these hazards. In regard to the other identified hazards, coastal/shoreline erosion, 

flooding, and wildfires, maps showing specific hazard locations have been included. 

Loss Estimation 

Describing vulnerability in terms of dollar losses provides the County and the State with a 

common framework with which to measure the effects of hazards on the county’s assets. 

However, the estimated dollar losses obtained through this process are only approximate and 

should not be used for other purposes. 

The damage estimate methodology used was based on FEMA’s publication Understanding 

Your Risks: Identifying Hazards and Estimating Losses. The result is an estimate of the 

potential hazard losses that could occur due to an event impacting and causing damages. 

The basic process for calculating loss estimates requires assessing the level of damage from a 

hazard event, both as a percentage of the asset’s structural and content replacement value, and 

as a loss of function. Next, the level of damage percentage needs to be multiplied by the value 

of the structure, its contents, and use. In this manner, comprehensive loss estimation can be 

developed that includes the risk to a structure itself, as well as the contents and functions of the 

structure. 

The St. Mary’s County loss estimation included an estimate of structural loss by determining the 

number of structures within the hazard area, grouped by specific occupancy class. The average 

structural replacement cost was used to determine the estimated losses. Since data on content 

loss were not available, they were not included as part of the loss estimation. 

Winter Storms 

Description of Vulnerability 

Vulnerability to the effects of winter storms on buildings depends on the age of the building, the 

building codes in effect at the time it was built, type of construction, and condition of the 

structure (i.e., how well it has been maintained). 

Snow and ice can be extremely hazardous. The entire county would be affected by snow, ice, 

and extreme cold. It could reduce visibility and surface accumulation could reduce traction and 

put a strain on power lines, roofs, and other structures. Severe winter storms could result in an 

expected increase in traffic accidents, impassable roads, and lost income as normal commuting 

could be hindered. 

Severe storm activity poses a significant threat to unprotected or exposed lifeline systems. 

Generally, commercial power networks are very susceptible to interruption from lightning strikes, 

high winds, ice conditions, and hail. Other utilities, including underground pipelines, may be 

impacted if not protected from exposure. 

All critical facilities in the county are vulnerable to the effects of severe winter storms due to the 

potential disruption of services and transportation systems as well as possible structure failure 

due to heavy snow loads. Severe winter storms have been and will continue to be a significant 

threat to the economic and social well being of St. Mary’s County. 

52



An analysis of the age of housing stock prior to and after 1940 revealed that 5 percent of St. 

Mary’s County’s housing units were built prior to 1940 (Table 5.5). Census tracts 24037995100, 

24037995300, 24037996100, and 24037996200 have a higher percentage of houses built prior 

Table 5.5 - Age of Housing Units (built before 1940) 

Census Tract Built Before 1940 Built After 1940 Total Built % Built Before 1940 

24037995000 13 1,817 1,830 0.7% 

24037995100 165 1,314 1,479 11.2% 

24037995200 194 3,114 3,308 5.9% 

24037995300 255 1,250 1,505 16.9% 

24037995400 142 2,198 2,340 6.1% 

24037995500 104 1,573 1,677 6.2% 

24037995600 98 2,413 2,511 3.9% 

24037995700 93 2,500 2,593 3.6% 

24037995801 8 1,304 1,312 0.6% 

24037995802 72 1,411 1,483 4.9% 

24037995900 34 4,010 4,044 0.8% 

24037996001 13 1,994 2,007 0.6% 

24037996002 19 2,341 2,360 0.8% 

24037996100 258 2,626 2,884 8.9% 

24037996200 202 2,051 2,253 9.0% 

Total 1,670 31,916 33,586 5.0% 

face these severe storms. 

to 1940 than the other census tracts. While 

some structures may be well preserved and 

constructed of stronger 

materials using better 

craftsmanship that more 

modern buildings. . 

However, some older 

structures may not be in a 

condition to weather these 

storms due to construction 

prior to code requirements 

(poor building quality, 

plumbing, etc.), and poor 

maintenance and decay 

over time and these would 

structures require adequate 

measures to ensure that they 

are brought up to code to 

A similar analysis of the age of housing stock age before and after 1990 was conducted (1990 

was used as the benchmark since the adoption of the International Building Code in 1988). 

Table 5.6 indicates that 72.5 percent of the county’s building stock was built prior to 1990 (i.e., 

prior to the new code). These structures may have to be inspected in detail to uncover potential 

construction issues. 

Mitigation Measures 

Table 5.6 - Age of Housing Units (built before 1990) 

Weather forecasting and 

warning county residents 

as far in advance as 

Census Tract Built Before 1990 Built After 1990 Total Built % Built Before 1990 

possible would allow time 

24037995000 1,321 509 1,830 72.2% 

to prepare for winter 

24037995100 1,134 345 1,479 76.7% 

storms. Stocking adequate 

24037995200 2,217 1,091 3,308 67.0% 

quantities of salt and sand 

24037995300 1,340 165 1,505 89.0% 

24037995400 1,804 536 2,340 77.1% 

expedites and improves 

24037995500 1,131 546 1,677 67.4% road clearing. Public 

24037995600 1,918 593 2,511 76.4% education concerning safe 

24037995700 2,100 493 2,593 81.0% driving, driving only if it is 

24037995801 

24037995802 

24037995900 

24037996001 

24037996002 

1,248 

1,272 

2,468 

1,334 

1,168 

64 

211 

1,576 

673 

1,192 

1,312 

1,483 

4,044 

2,007 

2,360 

95.1% 

85.8% 

61.0% 

66.5% 

49.5% 

required, and also stocking 

up on food, water, 

batteries, and other 

supplies will prepare 

people for the storm. 

24037996100 2,002 882 2,884 69.4% 

24037996200 1,879 374 2,253 83.4% The Department of Public 

Total 24,336 9,250 33,586 72.5% Works and Transportation 

maintains a Snow 

Emergency Plan and executes snow and ice removal operations, which includes coordination 

with volunteer fire and rescue stations for emergency response capabilities and with SMECO for 

53



power restoration priorities. Sheltering of citizens is a priority during extended periods of power 

outages which can occur during extreme winter storms. The Department of Public Safety and 

the Department of Social Services are responsible for the activation and execution of sheltering 

operations at local area high schools. 

The 2009-2010 winter seasons brought 2 extreme winter storms which record levels of snowfall 

occurred. During this event, multiple structures collapsed or incurred physical damages. It 

became clear the critical facilities must have structural analysis completed in order to document 

actual snow load capacities and to prioritize mitigation measures accordingly. 


The losses associated with winter storms are a result of structural damages, content damages, 

and disruption of business. 

Severe Storms 


Severe storms can strike anywhere in the county; therefore, specific building counts are not 

practical to use to assess the vulnerability to this hazard. Impacts from severe storms have 

been moderate, with localized flooding occurring from severe thunderstorms, minor damages 

from high wind events, and power and transportation disruptions from winter storms. The impact 

from hail and lightning has been limited to minor damages at specific locations. Severe storms 

could have a major economic impact on St. Mary’s County when utility systems, including 

electricity, are disrupted for an extended period of time. 


The losses associated with severe storms are a result of structural damages, content damages, 

and disruption of business. 

Wildfires 


Based on 2007 data from the State, approximately 54 percent of St. Mary’s County’s land area 

is forested. The State has delineated extreme wildfire risk areas for each county in the Maryland 

2010 Risk Assessment. Based on this information, there are approximately 6,289 out of a total 

of 51,358 structures (12.2%) in extreme wildfire areas. A total of 16 critical facilities are located 

in these wildfire high risk areas (Table 5.7). They include 3 schools, 3 churches, 1 fire station, 

and 4 bridges. 

Table 5.7 - Critical Facilities in 

Wildfire High Risk Areas 

Critical Facility Type Number 

Bridges 4 

Gas Chlorine Plant 2 

Dam 1 

Fire Department 1 

School 3 

Church 3 

SHA property 2 

Total 16 

Future wildfires could cause substantial loss of property along 

with direct and indirect economic effects for residents and 

community businesses. As indicated earlier, in recent years, St. 

Mary’s County has experienced an increase in population in the 

urban and rural areas. As more development is planned in the 

more rural areas and on forested or agricultural lands, the 

occurrence of human-caused fires and the number of people and 

property at risk due to wildfires will likely increase. Land supply 

will not be a deterrent to future population growth in the urbanwildland 

interface areas. 

54



Wildfire activity poses a threat to life and property and, can cause severe erosion and silting of 

stream beds, damage to watersheds, and flooding due to loss of ground cover. 

In assessing physical vulnerability, the most important factor is the extent to which structures 

get damaged when they are exposed to fire and heat. Current standard loss estimation tables 

do not exist for wildfires. The local fire station and structural engineers should help estimate 

structure and content damage from wildfires. 

Most wildfire-related deaths occur as a result of fire suppression activities. However, if roads 

are damaged or there is insufficient warning time, other injuries and deaths could occur. Since 

there are no death or injury statistics curves for wildfires, they are estimated based on past 

wildfire events. 


As people move to the County’s more rural and forested areas, increased development in these 

areas creates danger for both forests and the population located there. Mitigation options for 

wildland fires need to address not only the management of fuels, but also the potential for a 

growing population in wildfire threat areas. These measures may also define the necessary 

interface between private property needs and natural resource needs, public education, fire 

breaks, and maintenance of fire roads. 


Based on data from the Maryland Department of Natural Resources Forest Service for Southern 

Maryland, St. Mary’s County experienced a total of 1,004 fires between 1985 and 2010, 

resulting in a total a total of 873 acres burned. 

Tornadoes 

Table 5.8 - Manufactured Homes 


Tornadoes have occurred in St. Mary’s 

County in the past and are expected to 

occur in the future. Tornadoes often 

result in buildings with missing roofs, 

uprooted road signs, fallen powerlines 

and trees, destroyed homes and water 

towers, and damaged cars. The impact 

of tornadoes primarily depends upon 

their occurrence in developed areas – 

tornadoes in undeveloped areas may 

cause damage only to a few trees and 

may even go unreported. As 

development and population in the St. 

Mary’s County increases, a larger 

number of structures and people may be 

subject to tornadoes. 


In assessing vulnerability, the most important factor is how likely structures are to fail when 

subjected to wind loads that exceed their design or to flying debris that penetrates the building. 

Census Tract Manufactured Homes Total Buildings % of Total 

24037995000 63 1,830 3.4% 

24037995100 75 1,650 4.5% 

24037995200 109 3,341 3.3% 

24037995300 77 1,503 5.1% 

24037995400 130 2,261 5.7% 

24037995500 183 1,606 11.4% 

24037995600 91 2,224 4.1% 

24037995700 139 2,744 5.1% 

24037995801 0 579 0.0% 

24037995802 33 1,577 2.1% 

24037995900 511 2,822 18.1% 

24037996001 187 1,451 12.9% 

24037996002 417 2,082 20.0% 

24037996100 218 2,955 7.4% 

24037996200 322 2,227 14.5% 

Total 2,555 30,852 8.3% 

55



In general, building damages can range from cosmetic to complete structural failure, depending 

on wind speed and location of the building with respect to the tornado path, and can be 

analyzed by a structural engineer. Measures to reduce damages from tornadoes would include 

proper anchoring and strapping of buildings to their foundations and designing and constructing 

shelters and other critical facilities for appropriate wind speeds. 


Because there are no standard loss estimation models and tables for tornadoes, losses for 

tornadoes are based on exposure by older structures (built prior to 1940) and of manufactured 

homes. As indicated in Table 5.8, based on HAZUS data, there are 2,555 manufactured homes 

out of a total of 30,852 structures (8.3%) that were built prior to 1940. The total dollar exposure 

of manufactured homes in St. Mary’s County is approximately $130 million. Manufactured 

homes are particularly vulnerable to tornadoes and high-wind hazards. Census tracts 

24037995500, 24037995900, 24037996001, 24037996002, and 24037996200, each have over 

10 percent manufactured homes out of the total housing stock. Some of the older structures 

could also be more vulnerable to wind hazard events. In terms of calculating human losses, 

shelters throughout the community should be assessed for their locations, capacities, and 

strengths in order to ensure they are able to house residents and withstand the design wind 

speed. 

Since tornadoes are not location specific in terms of reoccurrence, it is difficult to anticipate 

where they could occur, based on past occurrences. 

Hurricane Winds 


Having investigated the different wind hazard issues of concern in St. Mary’s County, an 

analysis was conducted to assess the current, relative vulnerability of structures in the county to 

high wind hazards. Tropical storms, thunderstorms, and tornadoes are the types of events 

considered most probable to have a widespread effect on the county. Wind vulnerability of 

structures is dependent on several factors, including: 

• structure location particularly coastal vs. inland areas, 

• level of engineering design attention to quality of materials and construction, 

• structure exposure and height, 

• beneficial or adverse effects of nearby trees and structures, 

• age and condition, and 

• degree of rainfall or water penetration. 

The primary hazard caused by wind is the transport of debris, which can cause casualties and 

property loss or even the dislodging of manufactured homes from their foundations or vehicles. 

High winds may also cause damage to poles and lines carrying electric, telephone, and cable 

television service. As mentioned earlier, older structures built prior to the adoption of the 1988 

IBC could be more susceptible to wind damage. 

Although St. Mary’s County has not been directly hit by a hurricane, it is very vulnerable to one, 

by virtue of being a peninsula. The county is subject to the wind and flooding effects from 

hurricanes that hit the east coast and travel inland. Older critical facilities are vulnerable to wind 

damage due to the age of construction and possible poor condition, especially in the more rural 

and isolated areas of the county. It is important to identify specific critical facilities and assets 

that are most vulnerable to the hazard. Evaluation criteria include the age of the building (and 

56



what building codes may have been in effect at the time of construction), type of construction, 

and condition of the structure (i.e., how well the structure has been maintained). 

As development in the county and population density increase, wind may present an increased 

threat to the people and structures in the county. Building codes currently in place should be 

reviewed to ensure that they sufficiently address the excessively high wind velocities 

occasionally experienced in the county. 


The entire county can be affected by wind hazards. Aged, dilapidated, and poorly constructed 

buildings, and buildings not constructed to applicable building codes are more susceptible to 

wind and weather hazards. As mentioned earlier, manufactured housing units are especially 

susceptible to wind events. Strong winds can rip roofs off houses, overturn manufactured 

homes, or cause total failure of poorly constructed structures. Gable-ended roofs are also 

especially vulnerable to strong winds. Special attention should be paid to these structures in 

terms of strapping and anchoring of foundations. 


The HAZUS-MH Hurricane Model from FEMA’s loss estimation software was used to estimate 

losses to St. Mary’s County. A probabilistic scenario was developed for a Category 2 hurricane 

(96-110 mph 1 minute-sustained winds) that made landfall in the county. Hurricane parameters 

(wind speed, radius to maximum winds, central pressure, and time) were defined to simulate the 

effects a Category 2 hurricane, the losses for which were calculated. 

Based on this analysis, HAZUS estimates that approximately 253 buildings will suffer at least 

moderate damage (this includes severe damage and destruction) and 2,254 buildings will suffer 

minor damage. Of those that incur minor damages, the majority will be wood buildings (1,523). 

Approximately 580 and 100 masonry buildings will incur minor and moderate damage, 

respectively. Three buildings, one mobile home, and two wood structures will be completely 

destroyed. 

Building related losses are broken into two categories: direct property damage losses and 

business interruption losses. Direct property damage losses are the estimated costs to repair 

the damage caused to the building and its contents. Business interruption losses are the losses 

associated with the inability to operate a business because of the damage sustained during the 

hurricane. Business interruption losses also include temporary living expenses for those people 

displaced from their homes. The total building-related economic losses due to the modeled 

hurricane are estimated at $50 million. Of this, the largest loss was sustained by residences 

($48.7 million) and $ 950,000 was sustained by commercial properties. 

Approximately 1.3 million tons of debris would be generated, of which most would be tree 

debris. If the building debris tonnage is converted to an estimated number of truckloads, it 

would require 202 truckloads at 25 tons/truck to remove the debris generated by the hurricane. 

In terms of shelter requirements, approximately 21 households would be displaced due to the 

hurricane and of these, 5 people would seek temporary shelter in public shelters. 

Note: 1: These estimates are based on the HAZUS-MH Hurricane Model estimate of total 

number of structures identified at 30,852 (approximately 74 percent of the actual building count 

of 41,530) and total dollar exposure of these structures estimated at $5.05 billion. Since these 

numbers are much lower that numbers provided by the County’s Department of Land Use and 

Growth Management, they should be adjusted for the difference. These figures are only for 

indicative/informative purposes and should not be viewed literally for analytical purposes. 

57



Note 2: HAZUS-MH is one of many planning tools used by states and local governments. Other 

tools should be considered in developing the hazard analysis and risk assessment for local 

communities. In some cases, other tools and methodologies may offer more usefulness than 

HAZUS in the performance of a measure hazard analysis and risk assessment. 

Flooding 


Flooding of vacant land or land that does not have a direct effect on people or the economy is 

generally not considered a problem. Flood problems arise when floodwaters inundate 

developed areas, locations of economic importance, and infrastructures. Damage to buildings, 

particularly residential buildings, is usually the largest single flood-related problem faced by a 

community. 

There are a significant number of people living and working within or near the coastal and 

riverine floodplains who would be affected by flooding resulting primarily from thunderstorms, 

tropical storms, and hurricanes. The probability of repeated inland flooding, inability to mitigate 

the existing drainage problems due to a lack of funding, and the location of the pre-Flood 

Insurance Rate Map (Pre-FIRM) structures results in a high level of vulnerability to flood 

hazards. Given the large number of people can be affected by flooding, high economic costs 

and moderate response costs, the vulnerability to flooding is high in St. Mary’s County. Note: 

Pre-FIRM construction refers to structures built prior to the issuance of the community’s first 

Flood Insurance Rate Map (FIRM). St. Mary’s County was issued the first FIRM on 19 February 

1987. 

Data from the County’s Department of Land Use and Growth Management indicates that there 

are approximately 2,331properties in the 100-year flood zone. Of these 1,605 are residential, 

with a total value of approximately $258 million. 109 properties are of agricultural use with a 

total value of $27.2 million. The total value of all properties in the 100-year floodplain is 

approximately $454 million. Therefore, a significant portion of existing development in the 

county is vulnerable to flooding and flood damages (Table 5.9). 

Land Use Total Structures Land Value Im provem ents Value Total Value 

Agricultural 109 $ 14,258,940 $ 13,021,550 $ 27,280,490 

Commercial 85 $ 14,090,400 $ 13,320,470 $ 27,410,870 

Exempt 22 $ 4,561,500 $ 1,031,900 $ 5,593,400 

Exempt Commercial 15 $ 35,534,960 $ 80,221,500 $ 115,756,460 

Industrial 2 $ 5,412,000 $ 13,854,300 $ 19,266,300 

Residential 1,605 $ 137,292,000 $ 121,213,600 $ 258,505,600 

Other 493 NA NA NA 

Total 2,331 $ 211,149,800 $ 242,663,320 $ 453,813,120 

Based on the information provided by FEMA’s National Flood Insurance Program (NFIP), there 

are 1,319 policies in the County and 18 policies in the Town of Leonardown, insured at a total 

amount of $ 35.3 million and approximately $959,800 in premiums. The loss statistics indicate 

that there were approximately 11 loss cases in Leonardtown and 478 losses in the County and 

12 losses in Leonardtown between September 1978 and December 2010, resulting in nearly $ 

9.7 million in insurance payment. 

Note: Flood insurance is available for any structure (except in certain circumstances in mapped 

Coastal Barrier Resource or Otherwise Protected Areas) even those structures outside of the 

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mapped Special Flood Hazard Area (SFHA). Therefore, in some cases, the number of policies 

in a community includes policies for structures that are outside the mapped floodplain. 

Repetitive Loss Areas 

A repetitive loss structure is defined by FEMA as any structure for which two or more flood 

insurance claims have been paid for more than $1,000 in a 10-year period. While these 

properties make up only one percent of the flood insurance policies currently enforced, they 

account for 38 percent of the Nation’s flood insurance claim payments. A report on repetitive 

loss structures recently completed by the National Wildlife Federation found that 20 percent of 

these structures are listed as being outside of the 100-year floodplain. The United States 

General Accounting Office reports that between 1978 and 2004 NFIP's repetitive loss properties 

have cost $4.6 billion in flood insurance payments and numerous other flood-prone properties 

continue to remain at high risk in the Nation's floodplains. Therefore several programs have 

been developed to encourage communities to identify the causes of their repetitive losses and 

to mitigate these losses. 

Data from St. Mary's County Department of Land Use and Growth Management (Table 5.10) 

indicate that St. Mary’s County has had 57 repetitive loss structures; the majority in Scotland 

and St. George's Island, two in Tall Timbers, and one in Great Mills. Each of these properties 

has claimed at least two losses, some claiming three; the majority of the repetitive loss 

structures suffered damage in 2003 from Hurricane Isabel and in 2006 from Tropical Storm 

Ernesto. Eight of the 57 structures have been mitigated, either by demolishing and rebuilding a 

structure complaint with County regulations or by elevating the existing structure; St. Mary's 

County Dept of Land Use has applied to the NFIP to have those structures removed from the 

repetitive loss list. Of the eight structures one is commercial, nine are residential; three have 

been elevated above flood protection elevation (base flood elevation plus one foot freeboard), 

and five have been demolished and replaced. The insurance claim payments have ranged from 

approximately $1,100 to $178,000 and average $53,000 per insurance claim (includes contents 

and structural payments).Identifying areas of repetitive losses within a community is a good 

indicator to use in determining areas of the highest flood damage vulnerability. Although flood 

damage is not necessarily limited to these areas, repetitive loss data provides location 

indicators for areas where structures are experiencing recurring and costly flood damage. 

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Property Use Built 

Number 

Pre/Post FIRM of Losses Mitigated Mitigation Action Taken 

Year 

Mitigated 

1 RESIDENTIAL 1965 PREFIRM 3 NO none n/a 

2 COMMERCIAL 1950 PREFIRM 2 NO none n/a 

3 RESIDENTIAL 2005 POSTFIRM 2 YES REPLACEMENT STRUCTURE 2005 


5 RESIDENTIAL unknown PREFIRM 2 NO none n/a 


7 RESIDENTIAL 1953 PREFIRM 2 YES ELEVATED STRUCTURE 2008 

8 COMMERCIAL unknown unknown 2 NO none n/a 






14 RESIDENTIAL 2000 POSTFIRM 2 NO none n/a 


16 COMMERCIAL 2009 POSTFIRM 2 YES REPLACEMENT STRUCTURE 2009 







23 RESIDENTIAL unknown unknown 2 unknown none n/a 












35 unknown unknown unknown 2 NO none n/a 






















57 unknown unknown unknown 2 NO none n/a 

Critical Facilities in the Floodplain 

The county’s critical facilities database was used for identifying the facilities that are located in 

the 100-year floodplain. The analysis of these facilities revealed that there are no critical 

facilities in the 100-year floodplain. There is a school (Piney Point Elementary School) and a fire 

station (Harry Lunderberg Company 8) in the 500-year floodplain. 

However, an assessment of wastewater facilities by St. Mary’s County Metropolitan 

Commission revealed that portions of the Marlay-Taylor Water Reclamation Facility, Great Mills 

Wastewater Lift Station, St. George Island Wastewater Lift Station, and portions of the gravity 

and pressure sewer systems in many areas of St. Mary’s County, including St. George Island, 

Piney Point, Airedele Road, St. Clement’s Shores, and Wicomico Shores lie in the 100-year 

floodplain. Steps in each of these facilities have been taken to mitigate damage due to flooding. 

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The Town of Leonardtown has three critical facilities that are located in the floodplain: 

• Leonardtown Wastewater Treatment Facility- The Leonardtown facility is a 680,000 gallon 

per day facility that was built in the 1950s and upgraded in the 1980s and upgraded again to 

BNR in 2003. The Town began the process to expand the plant to a 1.2 MGD and 

upgraded the process to ENR, however, the downturn in the economy put the project on 

hold until early 2011. At that time, the Town will begin negotiation with MDE to decide when 

the project will be required to move forward for at least the ENR upgrade. Financing of the 

expansion is dependent upon income from new development which is dependent upon the 

economy. 

• McIntosh Pumping Station - This pumping station located along Rt. 5 near McIntosh Run, 

was upgraded in 2009. The upgrades included (2) two centrifugal pumps and electrical 

controls. A new 60 KW emergency backup generator will be installed in 2011. 

• Wharf Pneumatic Sewage Ejector Station - This facility was upgraded in 2009 and is online. 

The upgraded consisted of (2) duplex commercial pumps capable of pumping 132 gpm and 

a new emergency backup generator. 


The following mitigation actions are currently in place: 

• The county has a collective listing of roadways that have become inundated and/or 

overtopped by flood waters. 

• A capital improvement project named the Culvert/Bridge replacement is in place whereby 

undersized crossings are upgraded to the appropriate recurrent interval storm, the projects 

partially use Federal Bridge Replacement dollars for eligible structures. 

• The county also has an inventory of all ‘bridge’ structures that are can be included on a GIS 

layer. All major bridge structures and minor culvert structures are inspected by a certified 

professional. 

• To control flooding in public/private stormwater management facilities, the county has a 

contract with the Maryland Environmental Services (MES) to inspect the facilities for proper 

functioning and corrective maintenance. 

• More stringent floodplain regulations than required by the Code of Federal Regulations Title 

44, Parts 59-80. County regulations include a freeboard requirement, substantial 

damage/substantial improvement cumulative tracking, mandatory setbacks from the SFHA, 

limitations on fill in the floodplain, and limitations on enclosed space below base flood 

elevation (excluding crawl spaces) on new or substantially improved structures. 

• Documentation has begun for county participation in the National Flood Insurance 

Program's (NFIP) Community Rating System (CRS), a voluntary incentive program that 

recognizes and encourages community floodplain management activities that exceed the 

minimum NFIP requirements in exchange for county wide reduction in flood insurance 

premiums. Achieving a Rate Class 8 would reduce yearly flood insurance premiums paid by 

residents by $95,000. With minimal changes to the county regulations, we could achieve a 

Rate Class 7 which would reduce yearly premiums by over $140,000. 

• Given the high risk for flooding in the county, the comprehensive plan recommends that the 

county work to implement a “No Adverse Impact“ program for floodplain and stormwater 

management as recommended by the Association of State Floodplain Managers to reduce 

risk and increases in flooding due to new development. 

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Coastal/Shoreline Erosion 


St Mary’s County has 534 miles of shoreline. 

Table 5.11 shows that less than 7% of the 

shoreline has any significant risk for erosion. 

Some of the impacts from shoreline erosion 

include the direct loss of land and its 

economic, cultural, and ecological values as 

well as the offsite impacts caused by 

increased sediment. 

The Erosion Vulnerability Assessment (EVA) 

planning tool was developed and released in 

2008 by the Army Corps of Engineers 

5.11 Risk of Erosion for St. Mary’s County shorelines 

Category Miles Percent of shoreline 

No Change 164.00 30.7% 

Protected 83.79 15.7% 

Accretion 37.07 6.9% 

Slight 216.11 40.4% 

Low 10.34 1.9% 

Moderate 5.56 1.0% 

High 0.80 0.1% 

No Data 17.05 3.2% 

Total 534.72 100% 

(ACOE) to assist Bay jurisdictions to assess vulnerability of shorelines to erosion. The tool uses 

a 50-year planning window to project shoreline position in 50 years and identify what resources 

will be vulnerable. The EVA was developed through a partnership between Maryland 

Department of Natural Resources (DNR), the Baltimore District ACOE, and the Virginia Institute 

of Marine Science (VIMS). It was designed as an online interactive map interface to inform local 

planners where community infrastructure, cultural resources, and habitat are potentially at risk 

from erosion in the future. A classification was developed by MGS to characterize shoreline 

change in the following categories: High erosion > 8 ft/yr; Moderate erosion 4-8 ft/yr, Low 

erosion rate 2-4 ft/yr, Slight erosion rate 0-2 ft/yr, No change, Accretion > 0.01 ft/yr, Protected 

erosion control structures in place, No Data no historic data available to compute change and 

unknown available data unreliable. As a planning tool, the final products can enhance or 

redirect future development options for individual communities, and define areas where 

opportunities for conservation easements could be directed. 

The County’s Department of Land Use and Growth Management used GIS to overlay the EVA 

data on the county property polygon data to identify the properties most vulnerable to erosion. 

There are approximately 329 properties in the 50-year erosion zones mapped as having High, 

Moderate, Low erosion rates. Of these just over half (175 properties) are residential with a total 

value of approximately $93.4 million. Approximately 21properties are commercial or exempt 

commercial, with a total value of $38.4 million. The total value of all properties is approximately 

$180 million. 


The EVA as well as the “Shorelines Online” website and tools development by Maryland DNR 

allows county and state agencies to recommend appropriate shoreline protection measures to 

landowners and where future threats to infrastructure are identified, to seek funding for 

installation of shore line erosion practices. Another important component of planning for 

shorelines is the avoidance or minimization of protection for shoreline reaches that have 

minimal current or historic erosion and to target the use of appropriate protection measures 

based on the energy present in the system. Because shoreline environments are by their 

nature dynamic inappropriate protection can promote erosion on currently stable shorelines. 

Changes to state law in 2007 established requirements to use the “softest possible measures 

for protection. These measures often referred to as “living shoreline” measures appear to 

provide adequate protection that are more resilient than hardened structures damage from daily 

and extreme events and also provide habitat and water quality benefits. 

62



A comprehensive plan to coordinate protection efforts and an education and outreach effort to 

educate shoreline owners about the natural process of shore erosion is needed. On 29 August 

2009 at the Lexington Park Public Library and again on 12 January 2010 County staff along with 

DNR and MDE staff held workshops to educate waterfront homeowners on types of living 

shorelines, the cost of installation, appropriate maintenance, and funding sources. 

While 76 percent of the county shoreline experiences some degree of erosion each year, the 

EVA analysis shows that St. Mary’s County has only 25.8 miles of shoreline in the low erosion 

category, 5.4 miles in the moderate erosion category and 3.1 miles in the high erosion category. 

This means that a very low percentage of the County’s total shoreline falls in the most 

vulnerable category and requires significant protection measures. Using DNR data on cost per 

foot for shore erosion control structure, estimated cost for protecting the most vulnerable 

shorelines could exceed $44.6 million with project primarily accomplished by private land 

owners on a parcel basis without coordination or between projects. 

Chapter 4 - Goals and Objectives 

Introduction 

This chapter presents a series of goals and objectives to guide St. Mary’s County and the Town 

of Leonardtown toward identifying and selecting mitigation actions to address its vulnerabilities. 

The mitigation actions address the vulnerabilities discussed in Chapter 5 by identifying 

measures to help the County avoid, prevent, or otherwise reduce damages from hazards. 

While the Hazard Identification and Vulnerability Assessment chapters, Chapters 4 and 5, 

respectively, identified potential hazards and the areas and facilities in the county that are 

vulnerable to them, this Chapter will identify broad ideas to address these vulnerabilities and 

reduce the risk from natural hazards. Chapter 8 will layout a specific mitigation strategy by 

elaborating the action items, prioritizing the mitigation actions, identifying the implementation 

strategy of who is responsible for the action, completion, and identifying possible funding 

sources. 

Mitigation Goals and Objectives 

In the Hazard Mitigation Planning Committee meetings, County Commissioner meetings, and 

Public meetings which were held between June 2009 and December 2010, local government 

representatives discussed the findings of the vulnerability assessment and its implications for 

mitigation strategies. This information was presented to citizens at a Public Information Meeting 

and the community provided feedback which reconfirmed that the main desire was that 

mitigation objectives maintain the social, economic and environmental fabric of the community. 

First and foremost, mitigation objectives should address the protection of people, property, local 

governments, and the local economy from the effects of natural hazards. 

Hazard Mitigation Planning Committee discussed the goals which were outlined in the 2006 

plan and developed new goals according to the current vulnerability assessment, completion of 

certain projects outlined in the 2006 plan and based on needs identified by participating 

agencies. A list of goals that addressed various hazards was developed by the Committee 

based on risk assessment. The goals were reviewed and revised by the committee as 

necessary. The committee then developed additional goals specific to certain areas of the 

county and Leonardtown. These goals represent the vision for reducing damages caused by 

natural hazards and have been categorized into broad groups. 

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After the Hazard Mitigation Planning Committee developed the mitigation goals to achieve for 

the community, they identified specific mitigation objectives to help accomplish the goals. Each 

of the objectives was then developed into specific actions, discussed in Chapter 8 of the Plan. 

Definitions: 

Goals are general guidelines that explain what you want to achieve. They are usually broad 

policy-type statements, long term and represent global visions. Objectives define strategies or 

implementation steps to attain the identified goals. Unlike goals, they are specific and 

measurable. Goals and Objectives have been classified into the following 13 categories: 

− Flooding 

− Erosion 

− Wildfires 

− Wind 

− Winter Storms 

− Drought 

− Critical Facilities 

− Public Awareness 

− Existing Plans & Ordinances 

− Sustainable Development 

− Building Construction 

− Communications 

− Shelters 

Flooding 

Goal 1: Minimize damage caused by flooding. 

Objective 1: Minimize damage to existing structures, infrastructure and property caused by 

coastal, riverine, and stream channel flooding. 

Objective 2: Increase monitoring capabilities in areas which are frequently impacted by coastal 

riverine, and stream flooding for the protection of life and safety. 

Objective 3: Reduce damage to repetitive loss properties. 

Erosion 

Goal 1: Minimize damage caused by shoreline erosion. 

Objective 1: Determine whether existing land management measures in shoreline erosion 

hazard areas are adequate. 

Wildfires 

Goal 1: Minimize damage due to wildfires. 

Objective 1: Reduce damage and loss to existing community assets including residential and 

commercial structures and infrastructure due to wildfires. 

Objective 2: Reduce vulnerability of critical facilities located in wildfire high risk areas by 

identifying appropriate measures. 

64



Wind 

Goal 1: Reduce exposure of structures to wind hazards. 

Objective 1: Document conditions of current Critical Facilities and upgrade structures to current 

Maryland Building Codes where applicable.. 

Objective 2: Assess all mobile home communities in the county and outreach on most 

appropriate mitigation alternatives to reduce wind and flood damage. 

Objective 3: Document Wind Load capacities of all critical facilities within St. Mary’s County 

Government. 

Objective 4: Educate building inspectors and homeowners on the most recent code 

requirements. 


Goal 1: Minimize the impacts of winter storms on county residents. 

Objective 1: Inform residents about safety measures both before and after a major winter storm. 

Objective 2: Protect utilities, including underground pipelines, so that they may not be impacted 

and interrupted from exposure to hazards such as hail, icy conditions, etc. 

Objective 3: Document Snow Load capacities for critical facilities within St. Mary’s County 

Government. 

Objective 4: Strengthen critical facilities structures to current Maryland Building Codes. 

Drought 

Goal 1: Minimize loss due to drought. 

Objective 1: Educate residents on water conservation. 

Critical Facilities 

Goal 1: Ensure adequate protection of critical facilities and infrastructure throughout the 

county. 

Objective 1: Identify wastewater treatment plants and community wells in high hazard areas. 

Objective 2: Document Snow and Wind Load capacities on critical facilities within St. Mary’s 

County Government. 

Objective 3: Increase communications capabilities between Critical Infrastructures and 

Emergency Response personnel. 

Public Awareness 

Goal 1: Increase public understanding, support, and demand for hazard mitigation. 

Objective 1: Ensure proper real estate disclosure to enable buyers to make informed purchase 

decisions. 

Objective 2: Increase public access to Flood Insurance Rate Maps (FIRMs). 

Objective 3: Create awareness among residents of the potential hazards associated with 

specific hazard areas (floodplain, shoreline erosion, wildfire risk areas) and how they can 

protect themselves and their properties from these events. 

Objective 4: Identify and seek multiple funding sources that will support hazard mitigation 

awareness and training programs. 

65



Existing Plans and Ordinances 

Goal 1: Ensure hazard mitigation goals are consistent with goals and objectives of other 

plans in the county. 

Objective 1: Revise existing plans to incorporate Mitigation measures where appropriate. 

Objective 2: Consider increasing freeboard requirement for all new & substantially improved or 

damaged structures in the 100-year floodplain. 

Objective 3: Guide new development away from high hazard areas. 

Objective 4: Increase flood insurance program participation by landowners and renters and 

reduce risk to property by implementing “No adverse impact” recommendations and 

participating in the Community Rating System program. 

Sustainable Development 

Goal 1: Promote sustainable development to improve the quality of life. 

Objective 1: Increase natural resource protection through open space easements and 

acquisitions. 

Objective 2: Ensure all acquired properties that are in the floodplain are cleared of structures 

and remain in public ownership in perpetuity. 

Building Construction 

Goal 1: Encourage high construction standards. 

Objective 1: Ensure current building codes and standards follow FEMA’s basic guidelines and 

are properly implemented and enforced. 

Objective 2: Create an awareness of constructing buildings to safe standards. 

Communications 

Goal 1: Promote public understanding, support and involvement in mitigation related 

activities. 

Objective 1: Develop an education/public information program for the county. 

Objective 2: Develop a distribution plan for brochures and other relevant information. 

Objective 3: Create a standard user friendly public web-site for emergency mitigation, 

preparedness, response, and recovery information. 

Goal 2: Improve public warning systems. 

Objective 1: Ensure the entire county is within range of a hazard alert siren. 

Goal 3: Increase communications capabilities within Public Educational facilities. 

Objective 1: Ensure all education facilities in St. Mary’s County have full radio coverage for 

Emergency Response purposes. 

66



Shelters 

Goal 1: Provide for adequate shelters throughout the county to serve as refuge areas 

during hazard events. 

Objective 1: Increase public awareness on the importance of private shelters or safe rooms. 

Objective 2: Consider hardening for new schools and community facilities and require shelters 

in these buildings. 

Objective 3: Enact local ordinances to require community storm shelters within sizable 

(Quantify) mobile home parks and subdivisions (Quantify). 

Objective 4: Require construction of safe rooms in all new public buildings (schools, libraries, & 

community centers). 

Objective 5: Ensure local area shelters have power solutions for long term sheltering events 

during extended power outages. 

67

Chapter 5: Mitigation Strategy SMC Multi-jurisdictional Hazard Mitigation Plan 

Chapter 5 – Mitigation Strategy 

Range of Mitigation Initiatives and Policies 

The goals and objectives were integrated with the known and newly recognized hazards and 

vulnerabilities within St. Mary’s County to produce a series of specific mitigation actions 

designed to protect lives and properties of county residents. 

Developing a range of proposed mitigation initiatives and updating the policies, ordinances, and 

regulations that guide these efforts allows the systematic achievement of the goals of this plan. 

The Committee identified a range of mitigation initiatives and policies from the following 

categories: 

Preventive Measures 

Preventive measures are designed to minimize the potential development of new natural hazard 

problems and are intended to keep existing natural hazard problems from becoming worse. 

They ensure that future land development projects do not increase local and/or regional natural 

hazard damage potentials. Preventive measures are usually administered by local building, 

zoning, planning, and/or code enforcement officials and typically include the following: 

• Land use plans 

• Zoning ordinances 

• Subdivision and land development ordinances 

• Building codes 

• Floodplain development regulations 

• Erosion regulations 

• Stormwater management regulations 

• Operations and maintenance (O&M) procedures 

• Subsurface investigation requirements 

Emergency Services 

Emergency services protect people during and immediately following a natural hazard event. 

Counties and municipalities typically develop an Emergency Operations Plan (EOP) to formally 

document their emergency preparedness and response planning. The local EOP identifies 

standard operating procedures for various emergency management personnel and establishes 

the location and operating conditions of the Emergency Operations Center (EOC). As such, 

adopting and implementing the EOP is a critical first step in providing local emergency services 

measures in response to a natural hazard event. 

Emergency services measures can be implemented at the local, county, State, and/or Federal 

level, depending on the severity of the hazard event, and typically include the following: 

• Hazard indicators 

• Hazard warning 

• Hazard response 

• Critical facilities protection 

• Health and safety maintenance 

68


• Post-disaster recovery and mitigation 

Property Protection 

Property protection measures are used to minimize an existing structure’s vulnerability to a 

known hazard rather than trying to modify or control the hazard itself. Property protection 

measures involve improvements to publicly- or privately-owned property and must therefore be 

coordinated (and potentially even cost shared) with the respective property owners. Many of 

these measures do not affect the appearance or use of the structure, which make them 

particularly appropriate for historical sites or landmarks. Implementation of a property protection 

measure typically requires acquisition of a local building permit. As such, property protection 

measures include the following: 

• Relocation/acquisition 

• Elevation 

• Flood proofing 

• Insurance 

• Brush/shrub removal 

• Emergency response planning 

Structural Projects 

Structural projects are typically constructed to keep floodwaters and other natural hazards away 

from select areas. They are usually designed by engineers and managed or maintained by 

public works staff. From a flood hazard mitigation standpoint, structural projects can be used to 

control flows and water surface elevations for both flood minimization and recreational 

purposes. However, due to their limiting costs and potential environmental implications, 

structural projects are not normally constructed to protect individual properties, but are largescale 

undertakings designed to protect a large number of people and properties. As such, 

structural hazard mitigation projects typically include the following: 

• Dams/levees/floodwalls 

• Bridge/culvert modifications 

• Channel modifications/diversions 

• Firebreaks 

• Shelters/safe rooms 

Natural Resource Protection 

Natural resource protection activities implemented as hazard mitigation measures can be 

multiple in scope, purpose, and outcome. They are generally aimed at preserving (or in some 

cases restoring) local natural areas or environmentally sensitive resources, but can also play a 

significant role in reducing local and regional damages caused by natural hazard events. 

Natural resource protection activities are typically implemented by park, recreation, or 

conservation agencies and organizations, but are not limited to these types of entities. Any 

responsible entity, such as a local government, can develop and implement a natural resource 

protection program that will minimize the impacts of natural hazards while enhancing the local 

and regional environment. Natural resource protection activities that can minimize the potential 

impacts of natural hazards include the following: 

69


• Open space preservation 

• Wetland protection 

• Implementation of Best Management Practices (BMPs) 

• Water resources management planning 

Public Information 

Public information provides the public with accurate and relevant information as a key 

component of a successful hazard mitigation program. Public information activities advise 

residents, business owners, and local officials about natural hazards and how they can protect 

themselves, their property, and their constituents from these hazards. Public information 

activities can be aimed at the entire county or at select residents and business owners in known 

hazard areas. These programs are intended to motivate people to take precautionary steps on 

a pre-disaster basis. These public information activities include the following: 

• Map information 

• Library resources 

• Outreach projects 

• Environmental education 

Mitigation Actions 

Once the goals and objectives were developed, specific mitigation actions were identified and 

evaluated to address each goal and objective. This task was performed by the Hazard 

Mitigation Planning Committee. These actions range from construction projects (e.g., retrofitting 

existing structures) to non-construction related projects (e.g., the implementation of educational 

awareness programs). 

While some mitigation actions pertain to all hazards, others are specific to hazards such as 

flooding, wildfire, etc. Mitigation actions identified below are presented along with the estimated 

cost, the office or agency responsible for implementing the action, a timeline, and possible 

sources of funding and implementation. An overall priority is assigned to each action based on 

its effect on overall risk and property, ease of implementation, political and community support, 

and potential funding. 

Flooding 

Issue: A total of 8,918 properties lie within the 100-year floodplain. Their breakdown by location 

is as follows: 

Project 1: Increase flood hazard protection from localized flood hazard events by identifying at 

least 10 flood risk structures annually to develop measures to increase protection due to storm 

drain system improvements. This will reduce the depth and frequency of localized flooding in 

buildings and yards and reduce the danger of street flooding associated with old storm drains. 

Responsible Organizations - St. Mary’s County Department of Public Works and Transportation 

and Land Use and Growth Management, County Attorney’s Office – Real Property Manager, 

Town of Leonardtown 

Estimated Costs – Varies with each property 

70


Possible Funding Sources – USACE’s Floodplain Services Program, Pre-disaster Mitigation 

Assistance Funds administered by MEMA, Hazard Mitigation Grant Program Technical 

Assistance Funds administered by MEMA 

Timeline for Implementation – 2-5 years 

Project 2: Complete additional mitigation projects at area with repetitive loss. 

A Piney Point Mitigation project was completed to elevate two homes above the 100-year flood 

level. Additional sites will be identified throughout the jurisdiction as potential mitigation projects 

to assist homeowners that have repetitive flood properties. 

Responsible Organizations - St. Mary’s County Department of Public Works and Transportation, 

County Attorney’s Office 

Estimated Costs - $ 50,000 per structure 

Funding Agency – Maryland Emergency Management Agency (MEMA) 

Timeline for Implementation – 3 years 

Project 3: Expand the recently completed mitigation project at Mansfield to extend outward to 

the Great Mills Business Corridor and additional repetitive flood properties. 

The Mansfield Mitigation project involved the displacement/relocation of tenants, acquisition of 

property, and razing of an existing apartment structure near the intersection of Great Mills Road 

and Maryland Route 5. There are additional structures which are still subject to flooding 

conditions during extended rain events. These properties will be reviewed for possible Hazard 

Mitigation projects. 


and Land Use and Growth Management, County Attorney’s Office 

Funding Agency – Federal Emergency Management Agency 

Estimated Costs – 1.5 million 

Timeline for Implementation – 2 - 4 years 

Issue: The Maryland Department of the Environment contains an extensive database of 

repetitively flooded properties (those having two or more claims of $1,000 or more within any 

10-year period of time). The five properties that have been identified by MDE include: 2 

properties in Scotland; 2 properties in Tall Timbers; and one property in Great Mills. 

Project 4: The State recommends considering demolishing the structures and acquiring the 

properties. If this option is not feasible, elevate utilities and wet flood proof the structures. 

Consider procuring the services of a consulting engineer/surveyor to determine and inventory 

the following on potential repetitive loss structures: 1 st floor elevation, basement elevation, 

lowest opening, lowest adjacent ground grade, type of construction, use, and condition. 


and Land Use and Growth Management, County Attorney’s Office 

Possible Funding Sources – HMGP, PDM 

Estimated Costs – Consultant fees 


Issue: The State only has records of those properties having flood insurance are included in this 

database. The county will need to rely upon their own records to determine any repetitively 

71


flooded properties that do not carry flood insurance. Properties such as the Maryland Antique 

Center in Leonardtown that are in the 100-year floodplain have incurred repeated or significant 

losses and are not recorded as repetitive-loss properties. 

Project 5: Ensure that high-risk, pre-FIRM structures do not get repeatedly flooded by using 

retrofitting techniques to reduce the flood risk to the properties by developing a “flood inventory” 

of all repetitive loss structures that are currently not in the MDE’s database. Consider procuring 

the services of a consulting engineer/surveyor to determine and inventory the following on 

potential repetitive loss structures: first floor elevation, basement elevation, lowest opening, 

lowest adjacent ground grade, type of construction, use, and condition and then develop 

appropriate mitigation measures for each property. 

Responsible Organizations - Town of Leonardtown, State Highway Administration, County 

agencies 

Estimated Costs - Consultant fees, if applicable 

Possible Funding Sources – USACE’s Floodplain Services Program, Pre-disaster Mitigation 


Assistance Funds administered by MEMA, Flood Mitigation Assistance Program Technical 

Assistance Funds 

Timeline for Implementation: 1 year 

Issue: An Inventory of flooded conditions and resulting road closures on county maintained 

roads is maintained by the Department of Public Works and Transportation. Many of the existing 

storm drainage conveyance systems have recently been repaired to handle the runoff, which 

results in localized flooding, roadway closures, pavement failures, and other potential safety 

concerns. Reported flooding conditions occur at depths of 4-6 inches over portions of 

a roadway, with road closures (major flooding) required when an excess of 6 inches is 

experienced over a roadway. Portions of Friendship School , Bushwood Road and Baptist 

Chruch Road have experienced flooding. Several other roadways have experienced reported 

flooding conditions, often in areas where alternative access in unavailable. Local major collector 

roadways are designed to accommodate up to the 25-year recurrent storm event and safely 

pass the 100 year storm (flood). The evaluation, re-design, and replacement additional problem 

areas is needed. 

Project 6: Undersized bridges/culverts have been identified along the roadways mentioned 

above that result in roadway inundation or closure and determine appropriate measures to 

systematically replace and repair them and upgrade them to handle a 10-year and 25-year 

storm. Several sites have already been addressed and this project will continue until completion 

over the next 5 year period. 

Responsible Organizations - Department of Public Works and Transportation, State Highway 

Administration 

Estimated Costs - Consultant fees, if applicable 

Possible Funding Sources – MEMA, FEMA, MDE 

Timeline for Implementation: 2-5 years 

Erosion 

Sandgates, Sotterley and Far Cry Roads, and on St. Inigoes and Smith Creek there are a 

number of areas with concentrations of at risk structure, located in the following areas of the 

county: 

41 properties – Colton’s Point / Blackistone areas, 7 th District 

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12 properties – St Clements Shores 

32 properties – Breton Bay PUD, Society Hill, Rosebank and Newtown Neck 

27 properties – Breton Beach, Blake Creek and vicinity 

35 properties – Heron Creek, Cedar Cove, Tall Timers in Piney Point 

27 properties – St. George’s Island 

8 properties – Drayden, Carthagena Creek in Valley Lee 

29 properties – St Jerome’s Neck, Hayes Beach, Scotland, Cornfield Harbor and Point Lookout 

vicinities in Ridge 

17 properties – Town Creek, Myrtle Point, Kingston Creek vicinities in Hollywood 

52 properties – Scotch Neck, Clarkes Landing, Steerhorn Neck areas around Cuckold Creek in 

Hollywood 

There are 70 existing road segments totaling 1.86 miles of road length that occur in the 100 - 

year erosion zone. In many cases these segments constitute the only access route to properties 

protection of these segments, relocation and repair will be necessary. 

The 2003 St Mary’s County’s Shoreline Conditions Assessment identified a total of 171 potential 

sites that are experiencing erosion problems. These sites were evaluated using an iterative 

screening process to prioritize erosion control and shoreline protection needs. The objective of 

the screening process was to narrow the focus of the investigation of those areas experiencing 

the most critical erosion problems. After five iterations, a total of 12 potential erosion control 

project sites were identified and prioritized based on the severity of the problem and potential 

impacts. 

Project 7: For each of the 12 potential erosion control project sites, conduct a detail field 

evaluation to refine the proposed erosion project concept and estimated construction costs. Also 

identify properties that are subject to inland erosion. 

Responsible Organizations – St Mary’s County Department of Public Works and Transportation 

and Land Use and Growth Management, State Highway Administration, Maryland Department 

of the Environment, Amy Corps of Engineers, Soil Conservation Service, and the Town of 

Leonardtown. 

Estimated Costs – Varies with each property 

Possible Funding Sources – Corps of Engineers Section 103/14, DNR Shore Erosion Control 

Program, MDE Water Quality Revolving Fund. 

Time for Implementation – 8 -10 years 

Issue In areas with existing structures close to the edge, those landowners who own properties 

that are highly erodible ad have the means to do so are armoring the shoreline (where a site 

bulkhead, revetment- rip rap on shoreline, stone fill, jetties to capture sand) In many cases, 

owners of properties that are not highly erodible in nature are also doing so. This has increased 

the risk of erosion on either side of the protected properties, because hardening the shoreline 

magnifies the wave energy so, when it hits the unprotected area, it erodes faster. Thus a means 

to address this unnecessary protection is needed 

Project 8: Implement 2007 MDE requirements for installation of appropriate living shoreline 

protection methods, work with the MDE to appropriately implement the waiver process for 

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hardened shorelines in high energy environments and inform landowners about the guidelines 

that require the use of sire appropriate methods to protect shoreline 

Responsible Organizations – Land Use Growth Management, Maryland Department of the 

Environment (Tidal Wetlands Division) 

Estimated Cost – No cost anticipated 

Possible Funding Sources – No funding required 

Timeline for Implementation – 2 – 5 years 

Wildfires 

Issue: There are currently 16 critical/community facilities that are located in wildfire high risk 

areas, including 3 schools, 3 churches, and 1 fire department. 

Project 9: Identify appropriate measures to reduce the vulnerability of these critical facilities that 

may include the review of zoning regulations to defensible space practices to reduce loss. 

Responsible Organizations - Public Safety, GIS, Maryland Forestry Service and County Fire 

Departments 

Estimated Costs: Regular employee pay and volunteer time 

Possible Funding Sources - No funding required 

Timeline for Implementation - 2-5 years 

Issue: There are a number of service roads, abandoned road beds, public roads, farm roads, 

logging roads, utility corridors and pipelines, and other private access corridors in high hazard 

areas that may serve as good fire breaks. These roads are overgrown and, as a result, are not 

being used for the purposes for which they were intended. 

Project 10: Identify these roads that could be used as fire breaks and maintain them on a 

regular basis so that they can be used as natural breaks. 

Responsible Organizations - Department of Public Works and Transportation, GIS, Maryland 

Forestry Service, Fire Departments, St. Mary’s County Metropolitan Commission, and Southern 

Maryland Electric Service Cooperation 

Estimated Costs - Regular employee pay 



Issue: Residents are not very familiar with the concept of defensible space practices 

(buffer/stand-off distances of about 50 feet) that could reduce the potential for damage by 

wildfire). In addition, citizens must be educated on fire prevention safety measures such as 

defensible space practices and county regulations and ordinances for outdoor burning. 

Project 11: Develop procedures in county and State regulations to enhance the concept of 

defensible space practices and raise public awareness. Develop and Public Communications 

Campaign to familiarize residents with county regulations and ordinances and to promote the 

concept of defensible space practices in urban interface areas, which emphasizes that trees 

around new homes be thinned or cut down to create a buffer zone or stand-off distance of 

approximately 50 feet to reduce the potential for damage from wildfire. Create flyers and web- 

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site information easily obtained by residents on county regulations and ordinances for outdoor 

burning and utilize media outlets such as Channel 95 and 10, radio and print advertisement to 

deliver public outreach messaging on these issues. 

Responsible Organizations - Fire Services, Land Use and Growth Management, Public Safety, 

Public Information Office 

Estimated Costs - $70,000 for trifold brochure to be distributed to approximately $35,000 

residence in St. Mary’s County. Regular employee pay will be used for content and layout 

preparation and approximately $2 for printing a trifold brochure and postage. 

Possible Funding Sources - Hazard Mitigation Grant Program (HMGP), Pre Disaster Mitigation 

grant (PDM), Assistance to Firefighters Grant (AFG) through the Federal Emergency 

Management Agency (FEMA) 

Timeline for Implementation - 1 year 

Responsible Organizations – Department of Public Safety, Land Use and Growth Managment 

Wind 

Project 12: All mobile homes in the county have been identified and mapped to determine the 

most appropriate mitigation alternatives to reduce wind and flood damage. Residents within 

these communities must be educated on the hazards of living in these structures. Public 

Outreach will occur within these communities to help educated on hazards such as high winds, 

hurricanes/tropical storms and tornados and the appropriate measures which must be 

considered to protect life and safety. 

Responsible Organizations - Land Use and Growth Management, Public Safety 

Estimated Costs - Normal staff time 

Possible Funding Sources – Local Emergency Planning Grant and Citizens Corp Grant 


Project 13: Continue to educate building inspectors on the most appropriate tie-down 

procedures available for all structures including modular and mobile-homes and update subdivision 

regulations. Also, continue to educate homeowners on the most recent code 

requirements. 

Responsible Organizations - Land Use and Growth Management, Local Insurance providers, 

Insurance Service Organizations 




Issue: Publicly maintained roads throughout the county can become lined with trees that are 

vulnerable to wind damage. 

Project 14: Identify areas with trees and determined if they need to be cut down, trimmed, etc., 

to reduce vulnerability and risk of falling during or after a high wind event. 

Responsible Organizations - Public Works and Transportation, State Highway Administration, 

Southern Maryland Electric Cooperation, Maryland Forestry Service 

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Estimated Costs - To be determined 

Possible Funding Sources – County funding and Hazard Mitigation Grant 



Project 15: Inform residents about safety measures both before and after a winter storm. 

Prior to and during the winter, provide adequate information to educate citizens about: 

• Location of emergency shelters that may be opened as needed 

• Preparations to wait out a winter storm at home 

• Guidance on the use of portable and standby generators 

• Winter travel and tips for driving in bad weather 

• Fire hazards of space heaters 

• Protecting plumbing during a winter storm 

• Coping with winter power failures 

Responsible Organizations - Department of Public Safety, Town of Leonardtown, SMECO, 

Public Information Office, Department of Public Works and Transportation, State Highway 

Administration, St. Mary’s County Metropolitan Commission 


Possible Funding Sources - County funding, Pre Disaster Mitigation Grant and Local 

Emergency Planning Committee Grant 


Drought 

Project 16: Identify areas throughout the county where water reuse projects may be feasible 

(e.g., golf courses, non-potable domestic, commercial, and industrial uses). 

Responsible Organizations - Department of Parks and Recreation, Maryland Department of the 

Environment, St. Mary’s County Metropolitan Commission, and Land Use and Growth 

Management and Town of Leonardtown 

Estimated Costs - Staff time 


Timeline for Implementation - 5years 

Critical Facilities 

Issue: Currently, portions of the Marlay-Taylor Water Reclamation Facility, Great Mills 

wastewater lift station, St. George Island wastewater lift station, and portions of the gravity and 

pressure sewer systems in many areas of St. Mary’s County, including St. George Island, Piney 

Point, Airedele Road, St. Clement’s Shores, and Wicomico Shores lie in the 100-year floodplain. 

Mitigation measures have been taken at each of these locations to minimize flooding. These 

measures include elevated walls, standby generators, sealed wet wells, installation of water 

resistant pumps, etc. Leonardtown has three critical facilities located in the floodplain: the 

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Leonardtown Wastewater Treatment Facility, McIntosh Pumping Station, and Wharf Pneumatic 

Sewage Ejector Station. 

Project 17: Determine what flood mitigation measures may still be needed for each of these 

facilities and determine if additional funding is required. 


and St. Mary’s County Metropolitan Commission, Land Use and Growth Management, Town of 

Leonardtown 

Estimated Costs - Varies with each property 

Possible Funding Sources - USACE’s Floodplain Services Program, Pre-disaster Mitigation 


Assistance Funds administered by MEMA, Flood Mitigation Assistance Program Technical 

Assistance Funds, Small Flood Control Projects 


Public Awareness 

Issue: There is a need to develop a single distribution point for residents to conveniently access 

hazard information. 

Project 18: Designate the county’s website, fairs, St. Mary’s County Welcome Center, county 

libraries (Leonardtown, Lexington Park, and Charlotte Hall) as places for residents to seek 

information on flooding and other hazards. Interested property owners can read or check out 

handbooks or other publications that cover their particular situation. The county could develop 

and run their own public information campaigns with displays, lectures, and other projects, 

which could augment the county’s activities. These assigned locations should also house a 

number of FEMA publications dealing with various flood and other hazard related topics. In 

addition to the community library, publications should also be available at the county offices for 

public review. An informational brochure dealing with the health and safety issues of various 

hazards should be developed by the Emergency Management Director. This should include 

mapping of local evacuation routes and emergency shelters. 

The following information and manuals could be obtained from FEMA on various topics 

including flooding, risk management series, etc., and used for reference purposes. 

1. http://www.fema.gov/fima/rmsp426.shtm - FEMA 426- Reference Manual to Mitigate 

Potential Terrorist Attacks Against Buildings 

2. http://www.fema.gov/fima/rmsp428.shtm - FEMA 428- Primer to Design Safe School 

Projects in Case of Terrorist Attacks http://www.fema.gov/nfip/publicat.shtm - 

publications 

3. http://www.fema.gov/about/faq1.shtm - information on ordering publications and 

frequently asked questions 

4. http://www.fema.gov/nwz97/97050.shtm - This link contains information on publications 

for people with disabilities, Hispanic population, etc. 

5. http://www.fema.gov/hazards/floods/lib234.shtm - Repairing Your Flooded Home 

Create awareness at local fairs by distributing brochures. Fairs for the elderly are held in various 

parts of the county. Most municipalities have large fairs that can be used as avenues to 

distribute information to large groups of people. Use local fairs and carnivals in the county as 

opportunities to disseminate information to the public and identify specific points of contact in 

each municipality to take the lead in distributing this information. The Emergency Management 

77


could have handouts at the annual St. Mary’s County Fair held every September. Other festivals 

should be identified for opportunities to disseminate information to residents. Also, develop a 

public awareness program for Public Access Television. 

Responsible Organizations - Public Safety, St. Mary’s County Public Library system, Public 

Information Office, Volunteer Fire Companies, Town of Leonardtown, Local TV stations 

Estimated Costs - No costs incurred 



Project 19: The Citizens Emergency Response Team (CERT) program was developed and has 

been successful in recruitment and retention of volunteers. Since 2008, the Department of 

Public Safety has been successful in training over 60 volunteers through annual trainings and 

exercises. This program will be extended to reach organizations such as local businesses, faithbased 

organizations, Public Schools and local Colleges. Most CERT programs require 20 

hours of emergency management preparedness and response training for the members, but for 

some it can just be a way to improve their community’s preparedness capability through 

education programs. The project will continue training, maintenance and activation standards 

as well as administrative requirements like publications and establishing a database. Identify, 

designate, and train coordinators in various neighborhoods on CPR, and first aid. Due to this 

programs growth, it will also be necessary to train more coordinators and trainers to help 

continue all CERT related trainings and exercises. All CERT Volunteers will be utilized during 

community outreach events, Emergency Preparedness trainings and exercises, as well can be 

activated during actual events to help supplement the Emergency Response Community which 

can become overwhelmed during large scale incidents. 

Responsible Organizations: Public Safety, Public Information Office 

Estimated Costs: $5,000 

Possible Funding Sources: Citizens Corp Grant 

Timeline for Implementation: Continuous 

Timeline for Implementation: 2-5 years (to train coordinators) 

Existing Plans and Ordinances 

Issue: Natural hazards are currently not addressed in the county’s comprehensive plan. This 

Hazard Mitigation Plan should thus be viewed as and integrated as a ”safety” component to the 

county’s Comprehensive Plan. This guidance document provides a model natural hazards 

element that incorporates best practices and other best practices for local planning for natural 

hazards and long-term post-disaster recovery. 

Project 20: The Comprehensive Plan drives all ordinances. Integrate this all-hazard mitigation 

plan into the county’s and Town’s Comprehensive Plan during the next revision of the 

Comprehensive Plan and ordinances, to avoid development in hazard-prone areas. The county 

and Town of Leonardtown must review their comprehensive plans to ensure that designated 

growth areas are not in high hazard areas identified in this plan. 

Responsible Organizations: St. Mary’s County Department of Land Use and Growth 

Management, Emergency Services, Public Works and Transportation, Town of Leonardtown 

Estimated Costs – Normal staff salary 

Possible Funding Sources – None required 

78



Issue: High hazard areas are sometimes not taken into consideration when planning for new 

development. 

Project 21: The county’s Land Use and Growth Management department and the Town of 

Leonardtown should review their capital improvement plans to ensure that programmed 

infrastructure improvements are not in high hazard areas. An estimate should be made of 

potential dollar losses from hazards for each of the alternative growth scenarios developed as 

part of the county’s comprehensive planning proves. This will enable the public to take future 

disaster costs into account as they plan for future growth. This should also be taken into 

account for economic development initiatives. Steering business development away from 

hazardous areas will save businesses from the expensive cycle of disaster damage and repairs. 

Responsible Organizations: St. Mary’s County Department of Land Use and Growth 

Management, CIP, Board of County Commissioners, Town of Leonardtown 

Estimated Costs – Normal staff salary 

Possible Funding Sources – None required 

Timeline for Implementation – 1 year 

Issue: St. Mary’s County currently has a freeboard requirement of 12 inches for all buildings. 

Project 22: Consider increasing the current 12 inch freeboard requirement to 2 to 3 feet. 

Although no changes are required to be made to the floodplain services ordinances at this time, 

St. Mary’s County and the state of Maryland recommends that the following changes be 

considered, to strengthen the ordinance, based on lessons learned from Hurricane Isabel. The 

recommended changes to the State Model Floodplain Ordinance are outlined below. If the 

county did not adopt the State Model, they must determine how to best fit these changes into 

their ordinance. 

An increase in the freeboard requirement can be implemented simply by modifying the Flood 

Protection Elevation definition. Currently it is 12 inches foot of freeboard, but changing it to 2 or 

3 feet will implement a higher elevation requirement. Also, it is recommended that "repetitive 

loss" be added to the definitions. This will allow extension of the Increased Cost of Compliance 

(ICC) coverage in flood insurance policies that pays up to $30,000 in additional coverage to 

bring repetitive loss as well as substantially damaged properties into compliance with the 

floodplain ordinance. The community must be willing to treat repetitive loss properties the 

same as new and substantially improved structures to qualify. If this is adopted, they must 

require that repetitive loss properties meet all code requirements as new structures, but they will 

be making ICC payments available to these structures. 

Point of contact: John Joyce, State National Floodplain Coordinator, MDE. Email: John Joyce at 

jjoyce@mde.state.md.us. 

Responsible Organizations - St. Mary’s County Department of Land Use and Growth 

Management, CIP, Maryland Department of the Environment, Town of Leonardtown 

Estimated Costs - Normal staff salary 

Possible Funding Sources - None required 


79


Sustainable Development 

Issue: Ensure all acquired properties that are in the floodplain are cleared of structures & 

remain in public ownership in perpetuity. 

Project 23: Regardless of the source of acquisition or relocation project funds, once a flood-- 

prone property is cleared of structures, it should be maintained as open space in perpetuity. The 

properties can be enhanced to make better use of wetland or ecological habitat, but in no case 

should any type of structure be allowed, except perhaps for elevated walkways through 

wetlands to facilitate providing access to these areas for the purposes of learning about wetland 

habitat and ecology. Draft and submit ordinance to the County Commission/Leonardtown 

Commissioners to assure cleared floodplain land remains open in perpetuity. 

Responsible Organizations - Department of Land Use and Growth Management, County and 

Town Attorneys, Maryland Department of the Environment, Town of Leonardtown 

Estimated Costs - Normal staff salary 

Possible Funding Sources - General Fund 


Building Construction 

Issue: St. Mary’s County currently uses the 2009 International Building and Residential Code. 

The International Code Series is the most comprehensive series of code to date. These codes 

address essentially all areas of building construction and the various building services such as 

electrical, plumbing/gas and mechanical, and certain natural hazards. The 2009 building code 

stipulates that structures should be designed to withstand windspeeds of 100 miles per hour in 

their loading designs. Also, more stringent requirements will be imposed for roof tie-down 

requirements to avoid blow-offs during high wind storms. Trusses/rafters will be tie/strapped 

down to the foundation of the structure. Locally, there are over 100 facilities and structures 

which are owned and operated by County Government. Many of the structures listed are not 

built to current Maryland Building Codes and it is unknown as to the wind rating and snow load 

capacity, making it hazardous to allow citizens to shelter or staff to operate during severe 

weather events in these facilities. 

Project 24: Ensure current building codes and standards follow FEMA’s basic guidelines & are 

properly implemented. Examine infrastructure (water lines, electrical, etc.) for all new 

development periodically to ensure that they are designed to safe and high construction 

standards. 

Responsible Organization - Department of Land Use and Growth Management 

Estimated Costs - Staff time 

Possible Funding Sources - General Fund 


Project 25: Review design, construction and current facility conditions of emergency response 

and direct support facilities owned, operated and maintained by the County, to include any 

subsequent facility alterations to bring facility up to Category II Hurricane wind conditions and 30 

PSF snow loads. Scope of work includes structural analysis to determine live load that the 

current roofs can support. In addition, facilities which house cultural, historical or community 

based activities and equipment need to be reviewed to protect St. Mary’s Counties programs 

and history from damages which can occur during natural disaster. After the analyses are 

80


completed, construction upgrade projects can be outlined and prioritized accordingly and grant 

funding can be pursued. 

Responsible Organizations: St. Mary’s County Department of Public Works and Transportation, 

Public Safety and Land Use and Growth Management. 

Estimated Costs: $100,000 for engineering costs for structural analysis of all county owned 

facilities. Additional costs for structural upgrades will vary. 

Possible Funding Sources: Local funds, HMGP, (EMPG), PDM and the State Homeland 

Security Grant. 


Communications 

Issue: Currently, the entire county is not within range of a hazard alert siren. 

Project 26: Conduct a county-wide siren coverage study and prioritize areas that are in need of 

siren coverage. Identify major developments, municipalities, and other populated centers for 

the installation of additional warning devices. Incorporate voice Public Announcement 

capabilities where useful and ensure new procedures are developed and training occurs within 

appropriate disciplines. Develop a booklet to educate the public on meanings of warnings, and 

appropriate action to take before and during a disaster or emergency. 

Responsible Organizations: St. Mary’s County Department of Public Safety, Town of 

Leonardtown and Patuxent River Naval Air Station. 

Estimated Costs: $120,000 – sirens and radios cost approximately $15,000 per location. 

Estimate the need of 8 additional sirens county-wide. Cost for public education at $2.00 per 

booklet for 35,000 households equals $70,000. 

Possible Funding Sources: Local funds, HMGP, (EMPG), PDM and the State Homeland 

Security Grant. 


Issue: Portions of St. Mary’s County are vulnerable to specific hazards, such as coastal areas, 

floodplains and Calvert Cliffs Nuclear Power Plant Emergency Protective Zones. Public Safety 

is the responsible agency during emergencies to notify these populations. Current technology 

can be utilized with proper assistance from Information Technology to increase notification 

capabilities. 

Project 27: Utilize the reverse 9/11 system to notify citizens through the use of predefined 

groups, including Emergency Evacuation Zones within coastal areas, flood plains affected by 

the St. Mary’s County Dam and also those citizens impacted by Calvert Cliffs Nuclear Power 

Plant. 

Responsible Organizations: St. Mary’s County Department of Public Safety and the County 

Information Technology Department 

Estimated Costs: Normal staff time 

Possible Funding Sources: N/A 

Timeline for Implementation: 1 year 

81


Shelters 

Project 28: Increase public awareness on the importance of private shelters or safe rooms. 

Introduce the concept of constructing a tornado safe room in residences and involve Channel 95 

and the real estate community to promote safe rooms. These rooms protect against injury and 

death that could result from the dangerous forces of extreme winds. Work with builders to offer 

tornado safe rooms as an option for new construction and encourage builders to show safe 

rooms in model homes. Also promote the retrofitting of existing structures to include tornado 

safe rooms. A small interior room above grade is the best location for a safe room. Safe rooms 

are often used for other non-emergency purposes. Bathrooms and large closets are a frequent 

choice. Because warning times for tornadoes can be very short, quick access to the safe room 

is important in choosing location. If the owners have any special accessibility needs, these 

should be considered in the location and design of the safe room. The cost of a safe room 

varies according to the size and location of the shelter, number of exterior walls used in its 

construction, type of door used, type of foundation, and if the safe room is in a new house or a 

retrofit of an existing house. The average cost for an 8-foot by 8-foot tornado safe room in a 

new home ranges from $3,000-$6,000. FEMA's publication 320, Taking Shelter From the Storm: 

Building a Safe Room Inside Your House, and the accompanying construction plans and 

specifications may be ordered by calling 1-888-565-3896 or by visiting the FEMA Safe Room 

website at www.fema.gov/mit/saferoom. The designs in FEMA 320 can be built by most 

residential contractors. The qualifications and reputation of any contractor can be checked by 

the homeowner for all projects. The Wind Engineering Research Center at Texas Tech 

University also provides technical guidance about shelters. Their toll-free number is 1-(888) 

946-3287, ext. 336. Refer to FEMA publication Taking Shelter from the Storm: Building a Safe 

Room Inside Your House and call 1-(800) 480-2520 to obtain a copy of this publication. 

Responsible Organizations: Public Safety, in coordination with the other county departments – 

Land Use and Growth Management, Public Information Office, Board of Education, Maryland 

National Capital Building Industry Association 

Estimated Costs: Normal staff salary 

Possible Funding Sources: None required 


Project 29: Evaluate the need to develop local ordinances to require community storm shelters 

within sizable mobile home parks and subdivisions, and certain sized new construction including 

large commercial developments, community buildings (schools, libraries, & community centers). 

Responsible Organizations: Land Use and Growth Management 

Estimated Costs: Normal staff salary 

Possible Funding Sources: No funding required 


Issue: Currently the (3) area High Schools, Great Mills, Leonardtown and Chopticon are utilized 

as Public Shelters. Each site only has generator capabilities to run emergency lighting during 

power outages. During extended power outage events, local government does not have the 

ability to provide mass sheltering with necessary capabilities such as hot meals, showers and 

heating and air conditioning. 

Project 30: Install Emergency Generator Transfer Switches at all (3) locations which will allow 

for the temporary use of generators which can power necessary portions of the facilities which 

will provide power related services. State contracts are in place with multiple vendors in the 

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region which can be used to rent the necessary equipment. In addition, the Federal Emergency 

Management Agency (FEMA) has a supply of generators and local jurisdictions can request 

resources from FEMA before, during and after an event which impacts this region. 

Responsible Organizations: St. Mary’s County Public Schools and the Department of Public 

Safety and Maryland Emergency Management Agency 

Estimated Costs: $180,000 ($60,000 per site location) 

Possible Funding Sources: Emergency Management Performance Grant and State Homeland 

Security Grant Funds 

Timeline for Implementation: 2 years 

Project 30: Install Distribution Antennas on local area schools to increase communications 

capabilities within the facilities. Currently there is a lack of coverage in areas within structures 

which creates risk for emergency responders, staff and students during emergency events. 

Estimated Costs: $300,000 

Responsible Organization: St. Mary’s County Public Schools and the Department of Public 

Safety. 

Possible Funding Sources: Hazard Mitigation Grant, Emergency Management Performance 

Grant and State Homeland Security Grant Funds. 

Timeline for Implementation: 2 years 

83

Chapter 6: Action Plan 


Identification and Analysis of Hazard Mitigation Measures 

Each of the proposed mitigation actions was evaluated to assess level of impact to four 

elements: Life/Safety, Administrative/Legal, Capital Costs, and Operating/Maintenance. 

The Life/Safety impact element evaluated the direct and indirect impacts on St. Mary’s 

residents, businesses, and public safety. The impacts were considered low if the mitigation 

action would have a minimal or negligible impact, moderate if the action would have an indirect 

impact, and high if the action would impact public safety. 

The Administrative/Legal impact element assessed the mitigation action by determining if it 

would satisfy any legal or statutory requirement. The impacts were considered low if the 

mitigation action did not satisfy a legal or statutory requirement. They were considered 

moderate if the action would result in improved data collection and storage or administrative 

processes. The impact was considered high if it satisfied a statutory requirement or if it was a 

continuance of a key function. 

The Capital Costs impact was evaluated to determine the costs of the mitigation actions. The 

impacts were considered low if the costs were estimated to be less than $50,000; moderate if 

the costs were $50,000 to $250,000; and high if the costs exceeded $250,000. 

The Operating/Maintenance impact element was evaluated to determine the estimated on-going 

costs to the county from the mitigation action. The impacts were considered low if the on-going 

costs were less than $15,000; moderate if the costs were $15,000 to $30,000; and high if the 

costs exceeded $30,000. 

Timeframe 

The proposed mitigation actions were also evaluated to determine the estimated implementation 

timeframe. Actions that were determined to be short ranged had an implementation schedule 

within 1 year. Medium-ranged actions had an implementation schedule between 2 and 5 years 

and long-ranged actions had an implementation schedule between 5 and 10 years. Table 9.1 

identifies each mitigation action and evaluates the above mentioned criteria and assigns a 

timeline to it. 

Scoring Criteria for Mitigation Actions 

Life/Safety impact element - direct and indirect impact on St. Mary’s County residents, 

businesses, and public safety. 

Administrative/Legal impact element – to determine if it would satisfy any legal or statutory 

requirement. 

Capital Costs impact – to determine the costs of the mitigation actions. Low if the costs were 

less than $50,000; moderate if the costs were $50,000 to $250,000; and high if the costs 

exceeded $250,000. 

Operating/Maintenance impact element - to determine the estimated on-going costs to the 

county from the mitigation action. Low if on-going costs were less than $15,000; moderate if the 

costs were $15,000 to $30,000; and high if the costs exceeded $30,000. 

84



Evaluation Element 

Life/Safety 

Administrative/Legal 

Level of Impact 

L M H 

Minimal/negligible Indirect impact Direct impact on public 

impact 

safety 

Does not satisfy a 

legal or statutory 

requirement 

Improvement on data 

collection and storage 

or admin process 

Capital Costs $250K 

Operating/Maintenance $30K 

Satisfies a statutory 

requirement/continuance of 

key functions 

Timeframe 

“S” indicates short range – action implemented within 1 year 

“M” indicates medium range – action implemented between 2 and 5 years 

“L” indicates long range – action implemented between 5 and 10 years 

Scoring 

10 points for a “high” vote 

5 points for a “medium” vote 

1 point for a “low” vote 

7 points for a “short range” activity 

5 points for a “medium range” activity 

3 points for a “long range” activity 

85



Table 9.1 – Mitigation Action Table 

Project 

No. 

Project Description 

Life/ 

Safety 

Impact 

Admin/L 

egal 

Impact 

Capital 

Costs 

Oper./ 

Main. 

Costs 

Time 

frame 

Total 

Score 

1 

2 

3 

Increase flood hazard protection from localized 

flood hazard events by undertaking storm drain 

improvements to reduce flooding. 

Complete additional mitigation projects at areas 

with repetitive loss. 

Expand the recently completed mitigation 

project at Mansfield to extend outward to the 

Great Mills Business Corridor and additional 

repetitive flood properties. 

H H H H M 45 

M H M L S 28 

M M M M M 25 

4 

5 

6 

7 

8 

9 

Consider demolishing repetitive loss structures 

and acquiring the properties. If this option is not 

feasible, elevate utilities and wet flood proof the 

structures. 

Developing a “flood inventory” of all repetitive 

loss structures that are currently not in the 

MDE’s database. 

Continue projects related to undersized 

bridges/culverts that result in roadway 

inundation or closure and execute appropriate 

measures to systematically replace and repair 

them and upgrade them to handle a 10-year 

and 25-year storm. 

For each of the 12 potential erosion control 

project sites identified by the county’s Shoreline 

Study, conduct a detail field evaluation to refine 

the proposed erosion project concept and 

estimated construction costs. Also identify 

properties that are subject to inland erosion. 

Initiate discussions with MDE to identify 

appropriate shoreline methods to require the 

use of the methods if they protect the shore. 

Identify appropriate measures to reduce the 

vulnerability of these critical facilities that may 

include the review of zoning regulations to 

defensible space practices to reduce loss. 

M M H H L 22 

L M L L S 15 

H M H H M 40 

H H H H L 43 

H M L L S 24 

H H L M M 31 

86



Project 

No. 


Life/ 

Safety 

Impact 

Admin/L 

egal 

Impact 

Capital 

Costs 

Oper./ 

Main. 

Costs 

Time 

frame 

Total 

Score 

10 

11 

12 

13 

14 

15 

16 

17 

Identify existing service roads, abandoned road 

beds, public roads, farm roads, logging roads, 

utility corridors and pipelines, and other private 

access corridors in high hazard areas that 

could be used as fire breaks and maintain them 

on a regular basis. 

Develop procedures in county and State 

regulations to enhance the concept of 

defensible space practices and raise public 

awareness through a flier to introduce residents 

to defensible space practices in urban interface 

areas. 

Public Outreach to all mobile homes in the 

county on mitigation alternatives to reduce wind 

& flood damage and educate on potential 

hazards and ways to protect life and safety. 

Inform residents about safety measures both 

before and after a major winter storm. Prior to 

and during the winter, provide adequate 

information to educate citizens. 

Identify areas throughout the county where 

water reuse projects may be feasible (e.g., golf 

courses, non-potable domestic, commercial 

and industrial uses). 

Complete flood mitigation measures for the 

wastewater facilities in the 100-year floodplain 

are adequate and determine if additional 

funding is required. 

Designate the county website, local fairs, 

libraries (Leonardtown, Lexington Park, and 

Charlotte Hall) as places for residents to seek 

information on flooding and other hazards and 

create awareness at local fairs by distributing 

brochures. 

Continue CERT training, maintenance and 

activation standards as well as administrative 

requirements. Identify, designate, and train 

coordinators in various neighborhoods on 

CERT, CPR, and first aid. Develop a Citizens 

Corp Council. 

H M L M M 26 

H M L L S 24 

M L L M M 17 

H L L L S 20 

L L L M L 11 

M H H H ,M 40 

L L L H M 18 

M L M H S 28 

18 

Integrate this all-hazard mitigation plan all 

H H L L M 27 

87



Project 

No. 


Life/ 

Safety 

Impact 

Admin/L 

egal 

Impact 

Capital 

Costs 

Oper./ 

Main. 

Costs 

Time 

frame 

Total 

Score 

future updates of the county’s Comprehensive 

Plan during the next revision of the 

Comprehensive Plan, to avoid development in 

hazard prone areas. Identify means to ensure 

that local radio stations are able to continuously 

broadcast during power outages. Last plan 

updates were 2009/2010 

20 

21 

22 

23 

24 

Review county’s and Leonardtown’s capital 

improvement plans to ensure that programmed 

infrastructure improvements are not in high 

hazard areas. Integrate this all-hazard 

mitigation plan into the county’s 

Comprehensive Plan during the next revision of 

the Comprehensive Plan, to avoid development 

in hazard prone areas. 

Consider increasing the current 1 foot 

freeboard to 2 or 3 feet for all buildings. Review 

county’s and Leonardtown’s capital 

improvement plans to ensure that programmed 

infrastructure improvements are not in high 

hazard areas. 

Once a flood-prone property is cleared of 

structures, it should be deeded to a public 

entity and maintained as open space in 

perpetuity. Consider increasing the current 1 

foot freeboard to 2 feet for all buildings. 

Conduct a county-wide siren coverage study 

and prioritize areas that are in need of siren 

coverage. Identify major developments, 

municipalities, and other populated centers for 

the installation of additional warning devices. 

Continue to utilize the reverse 9/11 system to 

notify citizens through the use of predefined 

groups, including Emergency Evacuation 

Zones within coastal areas, flood plains 

affected by the St. Mary’s County Dam and 

also those citizens impacted by Calvert Cliffs 

Nuclear Power Plant. 

H H L L S 29 

H H L L M 27 

M H L M S 28 

M L M M M 25 

H L L L H 40 

27 

Increase public awareness on the importance 

of private shelters or safe rooms. 

H L L L H 25 

28 

Install Emergency Generator Transfer Switches L L H L M 28 

88



Project 

No. 


Life/ 

Safety 

Impact 

Admin/L 

egal 

Impact 

Capital 

Costs 

Oper./ 

Main. 

Costs 

Time 

frame 

Total 

Score 

at all (3) High Schools which will allow for the 

temporary use of generators which can power 

necessary portions of the facilities which will 

provide power related services. 

30 

Design new radio system to increase 

communications capabilities within identified 

critical facilities 

H M H H H 38 

89


High Priority Projects (highest scores) 

1. Increase flood hazard protection by undertaking storm drain improvements to reduce 

flooding. Identify at least 10 flood risk structures annually to develop measures to increase 

protection. 

2. For each of the 12 potential erosion control project sites identified by the county’s Shoreline 

Study, conduct a detailed field evaluation to refine the proposed erosion project concept and 

estimated construction costs. Also identify properties that are subject to inland erosion. 

3. Identify undersized bridges/culverts that result in roadway inundation or closure and 

determine appropriate measures to systematically replace and repair them and upgrade 

them to handle a 10-year and 25-year storm. 

4. Determine if flood mitigation measures for the wastewater facilities in the 100-year floodplain 

are adequate and determine if additional funding is required. 

5. Review the counties and Leonardtown’s capital improvement plans to ensure that 

programmed infrastructure improvements are not in high hazard areas. 

6. Identify areas with trees and determine if they need to be cut down, trimmed, etc., to reduce 

vulnerability and risk of falling during or after a high wind event. 

7. Identify appropriate measures to reduce the vulnerability of critical facilities in wildfire high 

hazard areas. 

8. Determine appropriate areas where overhead wires may be buried underground. Protect 

utilities, including underground pipelines, so that they may not be impacted and interrupted 

from exposure to hazards. 

90


SMC Multi-Jurisdictional Hazard Mitigation Plan 


Introduction 

This Plan document is considered St. Mary’s County’s road map for evaluating hazards, 

identifying resources and capabilities, selecting appropriate actions, and developing and 

implementing mitigation measures to eliminate or reduce future damage from those hazards in 

order to protect the health, safety, and welfare of its residents. The proposed projects in this 

plan will be implemented when funding is available and pursued by all means necessary to 

mitigate from the hazards outlined in Chapter 4: Risk Assessment. 

Monitoring, Evaluating, and Updating the Plan 

Monitoring, evaluating, and updating the Plan are critical to maintaining its relevance. Effective 

implementation of mitigation activities paves the way for continued momentum in the planning 

process and gives direction for the future. This section identifies who will be responsible for 

monitoring, evaluating, and updating the Plan, and what those responsibilities entail. This 

section also lays out the method and schedule of these and describes how the public will be 

involved on a continuing basis. 

Hazard Mitigation Planning Committee 

A permanent entity the “Hazard Mitigation Committee” is responsible for maintaining the Plan 

and for monitoring, evaluating, and updating it. The Director of Public Safety has been chosen 

as the committee chairman that will ensure that annual Hazard Mitigation meetings occur and 

the plan is updated as we move forward. 

The Hazard Mitigation Committee will oversee the progress made on the implementation of the 

identified action items and update the Plan, as needed, to reflect changing conditions. The 

Committee will serve as the focal point for coordinating countywide mitigation efforts and will 

meet annually to address all its responsibilities. It will serve in an advisory capacity to the St. 

Mary’s County Department of Public Safety. 

The Committee will monitor the mitigation activities by reviewing reports from the agencies 

identified for implementation of the different mitigation actions. The Committee will request that 

the responsible agency or organization submit a semi-annual report, which provides adequate 

information to assess the status of mitigation actions. The Committee would then provide their 

feedback to the individual agencies. 

Evaluation of the Plan should include not only checking on whether or not mitigation actions are 

implemented, but also assessing their degree of effectiveness. This would be done through a 

review of the qualitative and quantitative benefits (or avoided losses) of the mitigation activities. 

These would then be compared to the goals and objectives that the Plan was intended to 

achieve. The Committee would also evaluate mitigation actions to see if they need to be 

modified or discontinued in light of new developments. The Committee would document 

progress annually. 

The Plan will be updated every 5 years by the Department of Public Safety, as required by the 

DMA 2000, or following a disaster. The updated Plan would account for any new developments 

in the county or special circumstances (post-disaster). Issues that come up during monitoring 

and evaluation, which require changes in mitigation strategies and actions, should be 

incorporated in the Plan at this stage. 

Public Involvement 

91


SMC Multi-Jurisdictional Hazard Mitigation Plan 

The Committee should involve the public during the evaluation and update of the Plan through 

annual public education activities, public workshops, and public hearings. A public meeting was 

held on December 8, 2010 to obtain public input for plan evaluation. The meeting was facilitated 

by the Department of Public Safety. The public was notified through a newspaper 

advertisement. No one from the public was in attendance. It was video taped and was televised 

on Channel 95 (County Information Channel) It was also recommended that the county’s 

website serve as a means of communication by providing information about mitigation initiatives 

and to include having the plan available for citizens. In addition, following natural disasters 

which impact this jurisdiction, the Department of Public Safety will capture public comment and 

concerns for future updates within the plan where applicable. 

Updating the Plan 

Throughout the hazard analysis and vulnerability assessment, descriptions of missing or 

inadequate data indicate some areas in which the county and town could improve their ability to 

identify vulnerable structures. As the county and town governments work to increase their 

overall technical capacity and implement their comprehensive planning goals, they should also 

attempt to improve their ability to identify assets vulnerable to hazards. 

92

St. Mary's County Multi-Jurisdictional Hazard Mitigation Plan

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