Southwest Florida - Hernando County

Floodplain Justification Reporl Centralia Watershed (8206) 

Hernando County, Florida 

FLOODPLAIN JUSTIFICATION REPORT 

FOR MAINTENANCE OF WATERSHED PARAMETERS AND MODELS 

IN THE 

CENTRALIA WATERSHED (8206) 

Prepared for: 

SOUTHWEST FLORIDA WATER MANAGEMENT 

DISTRICT 

2379 Broad Street 

Brooksville, Florida 34604-6899 

and 

HERNANDO COUNTY GOVERNMENT 

20 North Main 

Brooksville, Florida 34601 

Prepared by: 

Southwest Florida 

Water Management District 

December 2,2009 

Southwest Florida Water Management District December 2, 2009

2379 Broad Street, Brooksville, Florida 34604·6899 

Southwest Florida 

(352) 796-7211 or 1·800423·1476 (FL only) 

Water Management District 

TOD only: 1·800·231·6103 (FL only) 

............~--~ 

On the Internet at WaterMatters.org 

An Equal 

Opporw"''Y 

E~ 

Bartow Service Office Sarasota Service Office Tampa Service Office 

170 Century Boulevard 6750 Fruitville Road 7601 Highway 301 North 

Bartow, Florida 33830-7700 Sarasota, Florida 34240-9711 Tampa, Florida 33637-6759 

(863) 534·1448 or (941) 377·3722 or (813) 985-7481 or 

1-800-492·7862 (FL on ly) 1-800-320-3503 (FL only) 1-800-836-0797 (FL only) 

Todd Pressman 

Chair, Pinellas 

Ronald E. Oakley 

Vice Chair, Pasco 

Hugh M. Gramling 

Secretary, Hillsborough 

Sallie Par1l.s 

Treasurer, Pinellas 

Carlos Beruff 

Manatee 

Bryan K. Beswick 

DeSoto 

Jennifer E. Closshey 

HIllsborough 

Neil Combee 

Polk 

Albert G. Joerger 

Sarasota 

Maritza Rovira-Farino 

Hillsborough 

H. Paul Senft, Jr. 

Polk 

Douglas B. Tharp 

Sumter 

Judith C. Whitehead 

Hernando 

David L. Moore 

Executive Director 

William S. Bilenky 

General Counsel 

PROFESSIONAL ENGINEER CERTIFICATION 

I hereby certify that I am a registered professional engineer in the State of Florida 

practicing with the Southwest Florida Water Management District, a public corporation 

authorized to provide engineering analyses by the state of Florida Department of 

Professional Regulation, Board of Professional Engineers, and that I, or others under my 

direct supervision, have prepared the hydraulic and hydrology evaluations, findings, 

opinions, calculations, conclusions, inundation maps, electronic databases, and models 

inputs hereby represented in the Justification Report for the Centralia Watershed, 

Hernando County, Florida. 

This information was developed in accordance with the Southwest Florida Water 

Management District's Watershed Management Program Guidelines and Specifications 

(G&S). The G&S define the watershed parameters used to develop a computer model 

that simulates projected surface water levels. The model includes watershed and rainfall 

event simulation parameters such as a design rainfall event and associated antecedent 

moisture conditions. This information, including projected surface water levels, was 

reviewed for substantial conformance with G&S, through a public review and comment 

period, and refined based on comments. The parameters and models are revised 

periodically based upon updated information and issued Environmental Resource 

Permits (ERPs). The District will consider site specific details and other refinements 

during the regulatory review process to revise model parameters and results. Therefore, 

the District cannot guarantee its completeness and shall not be liable for any damages 

suffered as a result of using this information. Those interested in using this information 

should contact the District for the current version of a model and results for a specific 

watershed . ERP applicants are encouraged to schedule a pre-application meeting(s) 

with the District's Regulatory staff to discuss the use of any watershed study/model in a 

subsequent ERP application. 

If you have questions, please contact the Southwest Florida Water Management 

District's Engineering Section at 352-796-7211 ext. 4232. 

Southwest Florida Water Management District 

Company Name 

Harry C. Downing 

Name 

, . 

FL P,E. ~~ 35'i02: 

",' e\ 

. 001\'~l 

-.

Floodplain Justification Report 


Centralia Watershed (B206) 

_____________________________________________________________________________ 

TABLE OF CONTENTS 

1.0 INTRODUCTION ___________________________________________ 1 

2.0 GUIDELINES & SPECIFICATIONS _____________________________ 1 

3.0 WATERSHED DESCRIPTION _________________________________ 1 

4.0 FLOODPLAIN MODEL DEVELOPMENT METHODOLOGY _________ 2 

5.0 VERIFICATION & VALIDATION DATA _________________________ 12 

6.0 MODELED FLOODPLAINS __________________________________ 14 

7.0 FLOODPLAIN JUSTIFICATION _______________________________ 15 

8.0 PUBLIC MEETING _________________________________________ 16 

9.0 CONCLUSION ____________________________________________ 16 

10.0 REFERENCES _____________________________________________ 16 

ATTACHMENTS 

FIGURES 

TABLES 

EXHIBITS 

Figure 1 - Location Map 

Figure 2 - Existing FEMA Floodplain 

Figure 3 - 1960 Potentiometric Surface Above Land Surface 

Figure 4 - Western Region Floodplain Comparisons 

Figure 5 - Corresponding Land Surface and 1960 Potentiometric Surface 

Figure 6 - Evaluation Areas for Multi-Day 

Figure 7 - Projected 1- and 5-day Elevation Comparison 

Figure 8 - Two-Sink Area Investigation 

Figure 9 - Catchments Selected for Multi-Day Assignment 

Figure 10 - Well Levels 

Figure 11 - Withlacoochee River and Weeki Wachee Well Levels 

Figure 12 - 1960 Potentiometric Surface Overlain On To 1970 Aerial Photos 

Figure 13 - Centralia Romp Well with Historic Contours 

Figure 14 - Pasco 16 Well 

Figure 15 - Modeled 100-Year/24-Hour Floodplain 

Table 1 - Floodplain Justification Summary 

Exhibit – Model Map 

________________________________________________________________ 





_____________________________________________________________________________ 

1.0 INTRODUCTION 

The purpose of this Floodplain Justification Report is to provide information regarding the reasonableness 

of the floodplain elevations simulated as part of the Centralia Watershed Management Plan Efforts. This 

effort is an update of the preliminary floodplains generated during previous watershed management 

efforts in 2006. After review and acceptance of this effort, the floodplain information will be used as part 

of the map modernization process in updating flood hazard areas for flood insurance mapping (FIRM) 

purposes. 

Engineering staff of the Southwest Florida Water Management District (District) and subcontractors ECT, 

Inc. conducted this watershed management effort to be used by the District and Hernando County, 

Florida as part of the floodplain mapping modernization process for Hernando County. This justification 

report was prepared by the District. 

A watershed model and Geographic Information System (ESRI ArcMap TM ) database is provided along 

with the report. Additional information used to support the development of the floodplains is provided in 

electronic deliverables. An overview of the methodology and results is provided for general reference 

only. More detailed information is provided in the enclosed electronic databases. 

This Floodplain Justification Report reflects comments made during internal reviews conducted in August 

2008, March 2009, and June 2009. Responses and modifications to the modeled floodplains are 

provided in a spreadsheet related Geodatabase located under the “COMMENT” subdirectory of the 

project submittal. 

2.0 GUIDELINES AND SPECIFICATIONS 

The watershed management activities were conducted in general accordance with the following 

documents: 

SWFWMD Guidelines & Specifications (G&S), current version with addendums 

FEMA Guidelines & Specifications for Flood Mapping Partners, 2003 

3.0 WATERSHED DESCRIPTION 

The Centralia Watershed is approximately 25.2 square miles (16,105 acres) in size and is located in 

north-west Hernando County (Figure 1). General characteristics of the watershed are summarized 

below: 

 

 

Topography – the terrain slopes from approximately 200 feet NAVD 88 beginning with 

Bailey Hill located in the southeast portion of the watershed and gradually declining to 

elevations less than 10-feet at the Gulf coastal areas located near US 19. The watershed 

is characterized by numerous depressions created by dissolution and collapsing of the 

underlying limestone that become more characteristic of wetlands near the coast. A 

natural channel exists in the eastern portion of the watershed, but gradually disappears 

as it enters the more karst areas of the watershed. 

Water Bodies – no significant lakes exist within the watershed. Sinks, wetlands, and 

predominantly dry depressions are pervasive throughout the watershed. A creek (Dry 

Creek) in the southeastern part of the watershed conveys runoff from Bailey Hill. A 

remnant creek still exists in the northeastern portion of the watershed that conveyed 

runoff from an area that has now been mined for limerock. 

________________________________________________________________ 




Hernando County, Florida Page 2 of 31 

_____________________________________________________________________________ 

Soils – deep sandy soils characterize (predominantly Candler) approximately 60-70 

percent of the watershed. Candler soils are characterized as hydrologic „A‟ soils which 

have good infiltration and very low runoff potential. The upper horizon of this soil has a 

permeability of 70 feet per day on average, based on the Soil Survey Geodatabase 

(SSURGO). A lower horizon below 4 feet has a permeability of 26 feet per day. Water 

tables within these soils are 6-8 feet or greater below the surface. With deep 

characteristic water tables these soils can infiltrate significant volumes of rainfall even at 

very high intensities. 

 

 

Landuse – the watershed is predominantly rural with a large portion of the watershed 

located east of U.S. 19 developed into single family residential lots that are about 0.5 

acres in size, but can range up to 10 acres. Approximately 25% of the lots are occupied. 

Limerock pits and spoil area characterizes the northeast portion of the watershed while 

the southeast portion of the watershed remains in its natural condition. The portion of the 

watershed located west of US 19 is predominately in its natural state. 

Existing Floodplains - a large portion of the watershed has no existing Federal 

Emergency Management Agency (FEMA) floodplain designations (Figure 2.). FEMA 

delineations total approximately 237 acres of which most are characterized as Zone A. A 

few AE zones exist along the western boundary of the watershed. Delineations appear to 

have been based on 5-foot contour map accuracy or USGS quadrangle resolution since 

floodplain boundaries cross several contours from the more accurate LiDAR derived 

topography. 

4.0 FLOODPLAIN MODEL DEVELOPMENT METHODOLOGY 

Compilation of acquired data, reports and historical data elements were relied upon to develop what is 

considered reasonable floodplain elevations throughout the watershed. Watershed management 

activities conducted in support of the generation of the floodplains included the following: 

 

Digital Topographic Information 

o 

Terrain for the watershed was based on LiDAR collected in January 2007 for Hernando 

County areas having a 95% vertical accuracy of ±0.5 foot for ground that is readily 

visible. The acquired LiDAR data at 6-foot post spacing was converted to a Digital 

Elevation Model (DEM) of 5-foot spacing for processing catchment information. 

Adjustments were made to the terrain in basins BS1400, BS1500, and BS1540 to 

account for a conveyance system that was located during the public input process. 

Terrain elevation data is in NAVD 88. 

 

Watershed Evaluation 

o 

o 

Generic watershed feature collection, evaluation, and assembly into datasets from 

existing sources. Existing data sources from the previous study and ERP construction 

plans were used to identify watershed features, and populate the Geographic Watershed 

Information System. ERP data and construction plans used within the watershed 

evaluation are documented in the Technical Support Data Notebook (TSDN). 

In some areas of the watershed the available terrain and construction details were not 

sufficient to develop the connectivity of the watershed. In such cases, field 

reconnaissance was performed to identify conveyance patterns and contributing areas to 

key storage areas, especially along the Suncoast Corridor that traverses the watershed. 

In some instances Geospatial data were collected to verify (xyz) information of key 

structure elements that appeared suspect. Limited survey accuracy techniques, GPS 

________________________________________________________________ 





_____________________________________________________________________________ 

and relative elevations to roadways crowns, depth of cover, etc. were used to meet the 

time constraints of the project schedule. All data were converted to NAVD 88. 

o 

Watershed boundaries, catchment boundaries, surface storage, and conveyance 

features of interest were developed based on the 2007 topographical data supplemented 

with conveyance feature information. Centralia watershed boundaries contiguous to 

other watersheds were matched to prevent overlaps and gaps as much as possible. 

o 

From use of the topographical data, closed conveyance features locations were 

anticipated and inventoried for pipes and inlets. When such conveyance systems did not 

exist, open conveyance systems such as channels, and overland weirs were used to 

connect catchments throughout the watershed. 

 

Watershed Management Plan 

o 

o 

o 

Under this element of the plan, generic and specific hydraulic feature information were 

processed into GIS feature layers and tables in support of the computer simulation 

model. 

Watershed feature information from GIS and other table information were translated into 

compatible input data for the ICPR Version 3.10 PercPack computer model to 

characterize the hydrology and hydraulic features of the watershed. The FEMA approved 

ICPR TM model version 3 for analyzing the watersheds response to design and historic 

storm events. 

Storm Events modeled: 

• The 100 year – 24-hour, 3-day, 5-day, 7-day durations and 500 year – 24-hour 

duration events using Technical Paper 49 (Weather Bureau, 1964) and the 

SWFWMD G&S designated rainfalls depths of 12.5, 14.8, 16.8, 18.0 inches for 

the 100-year events and 16.0 inches for the 500-year event, respectively were 

modeled. The 24-hour and 5-day distributions were based on the SWFWMD 

G&S. The Florida Type II Modified rainfall distribution was used for the one-day 

events according to the SWFWMD G&S. The multi-day events were distributed 

using the FDOT distributions as provided with ICPR, while the 5-day distribution 

was based on the Bear Creek Study provided in the SWFWMD G&S. The 24-hr, 

Florida Type II Modified distribution includes short-term peak intensities in order 

to simulate peak runoff rates that occur for small contributing areas during 

intense thunder storms. 

• Twenty-four and multi-day (5-day) rainfall events were simulated for the 

watershed. For the large relief and low permeable soils in the eastern portion of 

the watershed, the 24-hour storm generated the highest peak stages. For the 

western portion of the watershed, the multi-day generated the highest stages due 

to the filling of the available depression and soil storage. It was decided to use 

the 24-hour storm event for determining the resultant floodplains for the eastern 

portion of the watershed since there was no compelling evidence for the multiday 

event floodplains. For the western portion of the watershed model results, 

available historic and more recent high water marks, and potentiometric surface 

information generated in 1960 provided compelling evidence for the multi-day 

events. 

• Multi-day Justification - As part of the Peer Review, it was indicated that that a 

multi-day rainfall event would provide a better projection of the floodplain in 

certain areas of the Centralia watershed rather than the 24-hour event. Typically, 

________________________________________________________________ 





_____________________________________________________________________________ 

the 24-hour distributed with the Type II Modified SCS distribution addresses flood 

projections associated with peak responsive areas, whereas multi-day events 

address volume responsive areas. The Centralia watershed exhibits both 

characteristics. Initially, it was theorized that the starting water table or seasonal 

high elevations would characterize the volume sensitive areas, but modeled 24- 

hour flood projections in the western portion of the watershed still exhibited 

slightly lower elevations than might be expected in some areas. The 24-hour 

projections were sufficient for the eastern portion of the watershed based on high 

water marks that were available and the modeling results. 

The Centralia watershed is dominated by unconfined to semi-confined aquifer 

system that affects the surface level response to rainfall. The 2004 

potentiometric surface in concert with iterative simulation adjustments were used 

to develop initial water table conditions throughout the watershed since this 

period represented the most recent magnitude rainfall whereby documented 

flood elevations (high water marks) could be readily obtained. High water marks 

from collected data and aerial photos were used to determine the 

reasonableness of the results. Historical aerial photos provided the visual signs 

(tree-lines, wet prairies, etc.) regarding reasonableness of floodplains primarily in 

the western portion of the watershed. Aerial photos showing tree-lines from 

1944, 1951, and 1970, and the more recent photography of 2004 and 2005 were 

used to make inferences about historical flooding. 

In general it appears that 1960 may have generated the highest sustained flood 

elevations as evidence by the tree die-off manifested in the 1970 aerials and the 

now observed re-growth in the 2000 vintage series photography. The best 

verification came from the high water mark information from the recent 

hurricanes of 2004 and comparing those elevations to simulated flood elevations. 

The 2004 high water marks were used to verify the parameterization of the model 

along with the ROMP monitoring well data for the surficial and Floridan 

monitoring water level data. The 1960 tree-line or clear zone and the 1960 

potentiometric surface provided information on the near upper limit of most likely 

flooding. It should be noted that specific elevations for historical high water 

levels are sparse. The intersection of the 1960 potentiometric surface with land 

surface elevations provided better spatial inferences than can be achieved by the 

high water mark information alone. 

Comparison of the 1960 potentiometric surface intersection with land surface and 

the 1970 photos generally indicate that the multi-day events provide better 

projections of the 100-year event particularly in the western portion of the 

watershed. In a majority of the basins, the multi-day events are contained within 

the 1960 potentiometric intersected surface or polygon areas (Figure 3). 

Simulated floodplains trended smaller than the 1960 potentiometric surface area 

in the southwest portion of the watershed (Figure 4). It may be that the 

extensive ditching and draining of this area has had an impact on the 

potentiometric surface and flood elevations. There has also been a significant 

reduction in the contributing area in a subwatershed located just upstream of this 

area. In any event, it is recognized that there is compelling evidence that flood 

projections within these areas are better reflected by the multi-day event. 

The area where the multi-day better represents historical flood signatures 

corresponds to areas where land surface elevations are 25-feet or less (Figure 

5). These are the only areas that the multi-day can be applied provided the 

following criteria are met. The use of multi-day results will be used in areas 

where land elevations within a basin are typically 25-feet or less and the multiday 

floodplain is within the foot print of the 1960 intersected pot surface with land 

________________________________________________________________ 





_____________________________________________________________________________ 

surface. If the one-day or the multi-day (5-day) event produces a floodplain 

greater than the 1960 pot surface, the one-day will be used in that basin. There 

is one exception area that is identified in Figure 7. Mining areas where earthen 

material has been excavated down to the water table is also apparent in the map. 

These areas will be excluded from floodplain mapping. 

Simulations for 1 thru 7-day durations were conducted to determine the 

watershed‟s response to single and multi-day events and are included in a 

geodatabase table “ICPR_Node_Results.” Based on the simulations, 594 

junctions out of 932 non-boundary junctions exhibited a higher or same peak 

response with the 1-day (within ± 0.01 feet) as compare to the multi-day rainfall 

indicating peak sensitivity. None of the junctions exhibited peak elevations with 

the 3-day rainfall. One hundred seventy-two (172) junctions exhibited peak 

elevations with the 5-day rainfall. Of the 177 junctions that exhibited peak 

elevations with the 7-day rainfall, 156 were less than 0.5 feet higher than the 5- 

day rainfall and 108 of those were within 0.1 feet or less. Only 21 had projected 

peaks greater than 0.5 feet. To maintain consistency throughout the watershed, 

it is recommended that the either the one-day or 5-day be used. The one-day 

will be used wherever land surface elevations within a basin are greater than 25- 

feet which occur primarily in the eastern portion of the watershed. There is no 

compelling information to indicate that the multi-day should be imposed in this 

area. Mining areas will be excluded from floodplain assignment. In the western 

portion of the watershed where basins have land surface elevations 25-feet or 

less, the most appropriate rainfall duration will be used based on the compelling 

evidence. In this case, if the multi-day is higher than the 1-day and the multi-day 

floodplains are within the 1960 pot surface intersect with the land surface, then 

the multi-day (5-day for consistency) will be used. Otherwise, if either the 1-day 

or 5-day exceeds the 1960 pot surface the 1-day results will be used. Figure 6 

indicates the basins where the multi-day was evaluated. 

Figure 7 represents the results of the 1-day and 5-day comparisons. Green dots 

represent the junctions with flood elevations that are higher for the 1-day rainfall 

duration or the 1-day is within 0.01-foot of the 5-day duration rainfall. Yellow dots 

represent where the 5-day is less than one-half foot higher than the 1-day, while 

the red dots indicate where the 5-day is greater than one-half foot. Since the 1- 

day event is in agreement with high water marks observed in the eastern portion 

of the watershed the multi-day will not be applied in that area. 

On July 9, 2009, a field investigation was conducted in an area where significant 

differences existed between the one-day and multi-day events (Figure 8). This 

area is located in the southwest central portion of the watershed, and represents 

the terminal or last receiving area of runoff from a creek system. A rather large 

sink resides (Two-Sinks) in this location which is considered a volume sensitive 

area. High water marks (lichen lines) were very apparent and were higher than 

what the aerial photos of 2005 would lead one to expect. Preliminary review of 

collected high water elevations were between 27-28 feet, which is higher than the 

1960 potentiometric surface for the same area. This suggests that more than 

just local runoff is reaching the area from upstream portions of the watershed, 

and it is being infiltrated at such at rate that tree mortality is minimal. The recent 

observation of past flooding in this area provides compelling evidence for flood 

projections using a multi-day rainfall event, since the resultant flooding from the 

one-day duration is less than the recent flooding for the Two-Sinks area. 

The Frances rainfall simulation in concert with the high water marks collected 

were used to adjust the infiltration capacity in this area. A culvert of a specific 

diameter, length, and roughness factor was used to simulate the additional 

________________________________________________________________ 





_____________________________________________________________________________ 

infiltration capacity of the sink area not reflected by percolation. This area will be 

included in multi-day response area along with adjacent basins that area 

affected. 

The multi-day (5-day) will be applied only in the areas indicated in Figure 9 

based on the multi-day evaluation for each of the basins which includes the Two- 

Sink area previously mention. One hundred five basins out of 230 selected for 

evaluation had the multi-day rainfall applied for determining the 100-year flood 

elevations. The total number of basins in the watershed is 877. The darker 

purple color is the location of where the multi-day was applied. The lighter purple 

color are areas that were evaluated for multi-day assignment, but did not meet 

the criteria for compelling information (i.e., either the one-day or the 5-day 

exceeded the 1960 intersect area). The mining area located in the eastern 

portion of the watershed will be excluded from the floodplain mapping. 

• Doppler (OneRain) temporally and spatially derived rainfall for Hurricane Frances 

from September 4 to September 9, 2004 (96 hrs.) was applied to the watershed 

for verification of the model parameters. Rainfall during this period ranged from 

10.8 to 15.5 inches with an average of 13.4 inches. 

o 

The ICPR Model included the following elements: 

• 877 subbasins (delineated based on the DTM) 

• 948 active nodes representing storage in the form of ponds and depressions, 

channel junctions, boundaries, and receiving groundwater. 

• 3266 active reaches of which 1084 had simulated flow - 

 

 

 

 

 

123 Channels (all flowing) - representing 11.4 miles 

230 Pipes (200 with flow) – representing primarily conveyance 

connection through roadways 

2463 Weirs (342 with flow) - representing fixed structures, and natural 

and road overflows 

13 Drop structures (11 with flow) - mainly associated with SMAs 

455 (445 Percolation links active) – representing ground water infiltration 

within streams and depressions 

o 

Model Parameterization was based on the following criteria: 

• Hydrologic Parameterization 

Catchment delineation was based on the following watershed 

characterization: 

o 

o 

All significant depression storage areas were parameterized 

Channel segments or reaches identified based on a maximum 

length of 500 feet, change in grade and hydraulic characteristics, 

and confluences. 

________________________________________________________________ 





_____________________________________________________________________________ 

o DRAs identified through ERPs, topographic information, and field 

investigation 

o 

Complex conveyance systems to DRAs were simplified 

(especially along the Suncoast Parkway where multiple inlets 

within the median were identified) 

 

Green-Ampt method used in ICPR Model for generating rainfall excess 

o 

Soil parameters were provided by the SWFWMD in the form of 

GIS layer information and look-up tables and applied in 

accordance with the procedures discussed in the draft 

document, "Determination of Green-Ampt Parameters for 

Hydrology Computations In ICPR, SWFWMD August 2008." 

Sources for the data include the IFAS Soil Characterization Data, 

and the NRCS Soil Survey GeoDatabase. These parameters 

were used in the initial simulations and adjusted based on the 

comparison of observed vs. simulated results. These 

parameters were converted to the appropriate units and 

representation for use in the ICPR model. Parameters include: 

• Hydraulic Conductivity (SSURGO) – with a factor of onehalf 

applied to the specified value. The resultant value is 

in agreement with the reported ERP values particularly 

for the Candler Soils. 

• Depth to the Water Table (Seasonal High) – SSURGO 

values used for initial simulations with verification based 

on the September 2004 potentiometric surface map. 

Other data was used as this typically represents the 

initial conditions for modeling. In some instances the 

seasonal high is above the ground surface. 

• Soil Storage and porosity (IFAS Database and table 

provided by Rawls and Brakensiek, respectively). Soil 

storage is based on the IFAS Characterization data with 

an assumed depth to the water table and the soil at field 

capacity. 

• Effective Porosity = 0.90 x soil porosity. 

• ICPR Cutoff Depth is ICPRs representation of the 

location of the water table below the ground surface and 

is equal to (soil storage) / (effective porosity). 

• Suction Head = initial suction head of the soil based on 

literature values. It was found that the soil infiltrated 

volume is relatively insensitive to this parameter. 

o 

o 

Soil parameters were calculated individually for each subbasin 

using GIS processing tools and SAS. 

Percolation locations were based on an initial ICPR model run 

without percolation to identify where floodplains occurred in deep 

water table areas. After the percolation locations were identified, 

an iterative process was initiated to determine the percolation 

________________________________________________________________ 





_____________________________________________________________________________ 

area for each location. The accepted percolation areas were 

then included in the basin hydrology as impervious areas. 

 

Impervious and Directly Connected Impervious Area Determination 

o 

Impervious area determination of the watershed was based on 

the processing of County Tax Assessor information and paved 

areas. Percent impervious area on a lot-by-lot basis was 

determined for Hernando County and then applied to the 

watershed. Directly Connected Impervious Areas (DCIA) 

percentages were calculated using equations derived from 

studies throughout the United States. The percent DCIA was 

calculated from the impervious areas and type. It was decided to 

use this method rather than build upon the FDOT fluccscode. 

DCIA percentages for the percolation areas were set to 100 to 

turn-off the Green-Ampt infiltration calculations and just use the 

percolation component of the model. 

 

 

Time of Concentration (Tc) based on the determination of the longest 

flow path for each catchment using GIS tools and the TR-55 

methodology. The flow paths were intersected with the District's 

Landuse layer to determine whether paved or unpaved areas were 

encountered. 

The unit hydrograph method was applied to the time series rainfall 

excess to simulate runoff from the individual catchments. A 256 peak 

factor unit hydrograph was used per the G&S. A 256 peak or shape 

factor represents gently sloping terrains. 

• Hydraulic Parameterization 

 

 

 

Storage representation for depressions at ICPR junctions was based on 

the DTM of the watershed and extracted using the ESRI ArcHydro tools 

at specified elevation intervals. 

Channel storage is directly accounted for in the ICPR model during the 

routing process based on cross section data. Junction storage was not 

applied to catchments that had channel conveyance features other than 

some minor storage to help maintain model stability. 

Irregular cross-sections were determined from the DTM and the LiDAR 

data of the watershed. 

o 

Cross-sections for overland flow weirs were based on the 

intersection of DTM and shared catchment boundaries, and the 

use of the ET-GEOWIZARD to extract the sequenced xyz points. 

SAS Loess smoothing techniques were applied to both the xy 

and z data to reduce the number of data points used to represent 

the cross-section. Smoothing of the xy data was necessary due 

to the artifact of using a DEM grid. Weir lengths were more 

correctly estimated with the application of the smoothing. 

Lengths were typically 20-30% shorter than representation from 

the DEM grid with artifact kinks. 

________________________________________________________________ 





_____________________________________________________________________________ 

o Cross-sections for the channels were extracted directly from the 

LiDAR data using the LP-360 tool with xyz data provided every 

foot. Only smoothing of the z or elevation data was required 

because channel cross sections were represented by straight 

line segments. 

 

Culvert Inverts 

o 

Based on survey data, as-build-plans, construction plans, and 

estimated from the DEM with cover requirements when conflicts 

arose or no other data was available. 

 

Outfalls Along Watershed Boundaries 

o 

o 

Most outfalls for the watershed occurred along the western 

coastal boundary and were represented as overland flow weirs 

with no tailwater. 

One overflow into the Tooke Lake watershed occurred through a 

small culvert. Overflows into contiguous areas did not appear to 

be interactive so no time series elevations or tailwater interaction 

was considered. 

• Junction and Water Table Initial Conditions Evaluations 

 

Information Summary 

o 

o 

o 

o 

o 

o 

o 

o 

SSURGO depths to water table converted to elevations using the 

DEM and raster calculations 

September 2004 potentiometric surface map 

October 1960 potentiometric surface map (USGS Report) 

High water information from FDOT construction plans 

Limited Surficial Well Data 

Limited Geotechnical data to DRAs 

High water signatures based on review of 1970 aerial black & 

white photos 

Vegetative boundaries tree lines and wetlands used as indicators 

of water table conditions 

 

The 2004 potentiometric surface corrected to represent the surficial 

aquifer levels was used for the modeled initial stage for 100-year flood 

level projections This entailed the addition of 4.5 feet to the 2004 

surface. The resultant elevations were compared to the USGS 

measured October 1960 potentiometric surface after hurricane Donna in 

September of 1960. The 1960 surface was still significantly higher than 

the 2004 corrected surface. The corrected initial condition only affects 

the western third of the watershed where above or near surface water 

________________________________________________________________ 





_____________________________________________________________________________ 

table conditions exists. It is not a factor for the remaining portions of the 

watershed due to the relative large depths to the potentiometric surface 

or water table. 

 

 

For dry depression areas where no wetlands were observed and 

significant depths to the water table were projected, the low elevation of 

the DTM was used for initial conditions. For the channels the crosssection 

low points were used for the starting elevation due to the large 

depths to the water table and the lack of any significant sustained base 

flow conditions in the creeks. Depths to the water table were determined 

by subtracting the water table elevations from the land surface. 

Initial Junction Water surface elevations were adjusted to low point 

overflows or slightly below when indicated water tables were higher. 

These overflows and adjustments were made through the modeling 

process by turning the runoff and percolation off and observing where 

flow was occurring. 

• Use of Channel versus Overland Weir 

 

 

Channels were used when the DTM clearly indicated a defined water 

course. 

Irregular weirs were used to represent connectivity between depressions 

with significant ridges with no observed channel course. 

• Percolation as an Outfall 

 

 

Percolation Areas were used in channels and depressions where 

hydrologic „A‟ type soils were prevalent and where the water table was 

one-foot or greater below the surface or a DRA existed. 

Percolation was not included where: 

o 

o 

Shallow or above ground water tables were projected. 

Soils groups were not hydrologic „A‟ soils. 

 

Percolation in creek channels that flowed through characteristic 

hydrologic „A‟ soil areas were included due to the observed 

geomorphology (i.e., the channels ended internally within the watershed 

indicating significant infiltration along its path). 

o 

Boundary conditions were set up to allow flow from the watershed 

• Most overflows from catchments along the outer watershed boundary were set 

up automatically even if they would not flow. The same process was followed for 

internal overflows between catchments to prevent "glass walls." 

• Where boundary overflows would affect other modeled watersheds, resultant 

flow hydrographs were furnished to the respective project manager. Due to the 

relative small flow rates, no consideration for full interaction was considered. 

________________________________________________________________ 





_____________________________________________________________________________ 

o Floodplain Analysis using ICPR model results and GIS mapping methods 

• Floodplains in depressions were delineated by projecting model stage results 

onto the watershed DEM using the "Cut and Fill" tool provide with ArcInfo TM . 

The resultant areas were considered to be inundated by the 100-year flooding 

and have a base flood elevation (BFE) corresponding to a typical Zone AE 

designation used by FEMA Federal Insurance Rate Maps (FIRMS). 

• Sloping floodplains along channel features were delineated using contours and 

inundation levels from the cross-sections. Since cross-sections are located at 

model junctions, the resultant floodplain elevation was applied to the xyz points 

providing a guide for the delineations. Contours were then used to interpolate 

floodplain boundaries between the cross-sections. These areas were considered 

to be inundated by 100-year flooding and have a base flood elevation (BFE) 

defined at model junctions corresponding to a typical Zone AE designation use 

by FEMA FIRMS. 

• In depressions where peak flood elevations intersected with the catchment 

boundary a transitional floodplain down the contiguous catchment boundary flow 

path was generated to represent potential down slope flooding. No elevations 

are provided for these transitions. 

 

 

 

Where evidence of a road side swale or other type ditch system exists on 

the downstream slope of the receiving catchment, the floodplain width at 

the overflow is tapered down to the approximate top width of the 

conveyance feature. 

In the event only shallow sheet flow is expected along the downstream 

slope of relative short distance, gradual tapering according to 

engineering judgment was performed. 

For long shallow sheet flow systems, greater than 300-500 feet in length, 

a gradual tapering is applied down to an approximate estimate of a 

steady-state flow width along the ArcHydro designated flow path. 

o 

Model instabilities in stages and flows were reviewed to determine whether projected 

peak flood stage results were reliable. 

• In areas where several contiguous depressions can coalesce, link instabilities 

can occur as the model computations attempt to compensate for large 

conveyances with very small hydraulic gradients. When this occurs there is 

oscillations in the flow (going from positive to negative flows, repeatedly), but 

typically this is not observable in the stage data. In all cases the stages were 

stable and appeared reliable and reasonable. Weirs that were used to represent 

overland flow links between depressions exhibited this phenomenon. Half 

second time steps were implemented to reduce the number of instabilities or in 

this case, oscillations and changing from the Fread to the Mavis weir equation. 

Plots of every junction and flow link were reviewed as good engineering practice, and in accordance with 

the SWFWMD & FEMA guidelines and specification. The resultant flood elevations are considered 

reasonable for use in projecting floodplains using the procedures discussed previously. 

________________________________________________________________ 





_____________________________________________________________________________ 

5.0 VERIFICATION & VALIDATION DATA 

Some limited water surface elevation data exists whereby independent verification of model assumptions 

and/or reasonableness of the results could be made. The available data used is summarized below: 

 

Hydrologic Gauge Data: No long term lake, pond, or aquifer level data is available within 

the watershed proper for use as verification or validation of model results. A well located 

south of the watershed (Weeki Well) that is used to compute discharges for Weeki Wachee 

Springs based on the nearby aquifer levels was considered appropriate for determining the 

expected return frequency of potentiometric surface elevations throughout the area. The 

period of record for the well is 1964 to present. It was determined that the potentiometric 

surface is a good indicator of flood levels in watersheds areas characterized as unconfined to 

semi-confined. A review of the yearly maximum water surface elevations for the Weeki Well 

indicates that the 2004 level at the well (approximately 23 feet NGVD) has occurred several 

times in the past suggesting that the 2004 water potentiometric surface elevations are not 

representative of a 100-year event, but more in line with a 10- to 20- year event based on the 

number of occurrences (Figure 10). Groundwater elevations within the Weeki and 

Masaryktown wells similar to the 2004 water levels have occurred several times in the recent 

past. 

Regression analysis was performed with a well located within the Brooksville Air Port (ROMP 

CB-4N Masaryktown Avpk FLDN) to determine whether the Weeki Well record of maximum 

annual events could be extended to include a known flood event that occurred in 1960. The 

R 2 of the regression was 0.86 on a scale from 0 to 1.0 where 1.0 is a perfect prediction. The 

projected water surface elevation for the Weeki Well for 1960 was 28.5 feet NGVD 

(Figure 10). A Florida Geological Survey (USGS, RI No. 34, 1964) estimate of the 1960 

potentiometric surface at the well location after the passing of hurricane Donna was between 

27-28 feet NGVD which verifies the regression results. This elevation is significantly higher 

than that achieved during the 2004 event by 5 feet or more. Based on this analysis it was 

concluded that flood levels greater than 2004 would be more indicative of a large return 

interval event such as the 100-year. This analysis allows bracketing of the historical high 

water marks which are discussed later. 

To determine the expected return frequency for the 1960 event potentiometric surface in 

areas like Centralia, surface water flows and levels for the USGS Gage at Trilby for the 

Withlacoochee River were reviewed. River flows typically extend back almost 100 years, and 

the USGS has recently performed return frequency analyses on these gauging stations 

(USGS, SIR 2005-5080, 2005). Based on this report, the 1960 event is about a 75-year 

event for the river with two other known floods in 1933 and 1934 of greater magnitude. A 

comparison of the Weeki Well water elevations to the river stages at the Trilby gage was 

conducted to determine whether any correlation exists whereby a return frequency for 

observed high water marks in depressions and potentiometric surfaces within the Centralia 

Watershed could be established. A review of Figure 11 indicates that maximum annual 

levels in the Weeki Well correspond for the most part to the maximum annual flows and 

levels within the Withlacoochee River. Other comparative reviews from wells and lake level 

data generated similar results. 

To gain a better understanding of the spatial extent of the flooding in 1960, the resultant trend 

surface of the 1960 potentiometric surface (RI No. 34) was compared to the LiDAR terrain 

data for the watershed. This was performed by subtracting the 1960 surface from the terrain 

to determine the areas of inundation. The areas of inundation were then compared to aerial 

photography for verification. Also, the potentiometric surface elevations were compared to 

high water mark elevations within the watershed. 

________________________________________________________________ 





_____________________________________________________________________________ 

 

SWFWMD Highwater Database: The SWFWMD has compiled high water information from 

various sources that includes FDOT plans, surveyed water marks from 2004, flooding 

complaints, potentiometric surface maps from 1960, and aerial photography. This 

information was reviewed to determine whether projected flood elevations were reasonable 

for the Centralia Watershed. 

o 

o 

o 

Photographic Documentation: No photographs at the exact time of the flooding are 

available for this watershed, but available photographs do provide interpretative 

information regarding the extent of the potential flooding. Figure 12 provides an 

overlay of where the 1960 potentiometric surface exceeded ground elevations onto 

the 1970 aerial photography. The purple polygons indicate the flood extent based 

upon the potentiometric surface. The polygons line-up very well to the tree line of the 

photo which is indicative of a water surface that occurred of sufficient duration to 

establish an open area surrounded by trees that are not tolerant of long-term 

inundation. A review of the 2004 aerials indicates that over the recent 40-50 years 

that the tree line has moved down slope suggesting that floods of the 1930s, 50s, 

and 60s have not occurred recently, but there is nothing to suggests that they would 

not under the right hydrologic conditions. 

High Water Marks – of various vintages have been acquired from various sources. 

Once such location is the depression located at the north side of the intersection 

between Centralia Road (CR-476 and U.S. 19). High water information indicates that 

levels have ranged between 15 feet to almost 20 feet over recent history. Fifteen feet 

corresponds to the 2004 events, while the 19.8 foot probably corresponds to the 

1960 condition, which is very close to the 1960 potentiometric estimate of 19.2 foot. 

Other highwater marks exists along a creek that crosses Centralia Road in several 

places and originates in the upper elevations of Bailey Hill (topographic high of the 

watershed). Modeled 100-year elevations corresponded very well to the indicated 

highwater marks in this area. 

Documented Flooding Areas: There is a couple documented flooding complaints in 

the watershed where flooding is projected to occur, but the extent of the flooding at 

the time is unknown. The author of this report experienced first hand flooding in the 

watershed, particularly in 1974 when Centralia Road washed out in several areas 

from a rather large high intensity event. 

 

 

Simulated Rainfall – Hurricane Frances Rainfall of 2004 derived from Doppler Radar data 

(OneRain) was developed and used to provide general verification of the model parameters. 

Flood results compared favorably with the high water elevations throughout the watershed 

when initial water surface conditions were adjusted surficial water tables rather than Floridan. 

Initial conditions - Hurricane Frances and the design event simulations were based on the 

2004 potentiometric surface maps with adjustments. For Hurricane Frances the 

potentiometric surface with a correction elevation addition of 3.0 feet was used for estimating 

the surficial rather than the Floridan. For the 100-year event the potentiometric surface with a 

correction addition of 4.5 feet was used. The necessity for the correction is based on high 

water mark information within the watershed from the 2004 hurricane season. To achieve the 

indicated flood levels in the western portion of the watershed the initial Seasonal High Water 

Table had to be adjusted to the 2004 potentiometric surface plus 3.0 feet. The western 

portion of the watershed is where the potentiometric surface can exceed land surface 

elevations and express itself as surface water. 

________________________________________________________________ 





_____________________________________________________________________________ 

Review of information provided by the Centralia Regional Observation Monitoring Program 

(ROMP) Well in comparison to the potentiometric surface elevations of the September 2004 

and October 1960 provide further justification for correcting the initial water table condition 

(Figure 13). Both the surficial and the Floridan (Ocala) aquifers are monitored at this well 

which is located about mid position of the watershed along Centralia Road. Based on the 

data, the peak surficial aquifer level demonstrated a response that was higher than the peak 

Floridan by 3-4 feet for 2004. This suggests that a restrictive horizon exists between the 

surficial sands and the upper Floridan in the watershed generating high water elevations than 

measured in the Floridan when extreme rainfall events occur, justifying the need to increase 

the initial conditions. The 1960 potentiometric surface was 10-feet higher than the 

September 2004 contour map elevations and 5-feet higher than the measured maximum 

surficial elevation in 2004 at this location. The land surface elevation at the well is about 10- 

12 feet above the 1960 potentiometric surface elevation. 

Further review of well level data (Figure 14) from the Pasco 16 Well (located in the southeast 

portion of the Pasco High) in Pasco County and the ROMP CB-4N Masaryktown AVPK 

FLDN (located at the Brooksville Airport) suggests that aquifer levels were near their 

maximum elevations when Hurricane Donna occurred driving levels up further by about 2-3 

feet. These two wells are the only wells where water level data was available during the 

1960 events. The lesser response (change in levels) to Hurricane Donna as compared to the 

tropical depression response in later July prior to Donna would suggest that aquifer levels 

were near land surface and possibly discharging to surface water features. This 

phenomenon is exhibited in the 1960 potentiometric surface overlay with land surface, 

whereby some model nodes exhibited flow at time zero. 

 

Public Comments Data – no public meetings have been conducted at this time. 

6.0 MODELED FLOODPLAINS 

The 100-year / 24 hour and 5-day (1% annual probability) storm events were used for estimation of 

floodplains for this watershed. These storm events were used due to the peak sensitive characteristics 

of the eastern portion of the watershed as a result of steep sloping terrain and shallow depths to the 

seasonal high water table and the 5-day in the western portion which is more volume sensitive and 

subject to groundwater discharge. Comparison of flood results between the 100-year / 24 hour and a 

multi-day event (5-day) indicated that the watershed did in fact demonstrate a greater flood response in 

the eastern area for the 1-day event and the western with the 5-day event. The western portion of the 

watershed demonstrated a greater response to the multi-day event because of the depressional 

characteristics of the watershed which respond more to the volume of rainfall rather than intensity. 

Historical review of the aquifer response to rainfall in these karst areas indicates that the initial 

watershed conditions before a storm are highly dependent on pre- rainfall antecedent conditions. The 

selection of initial conditions and rainfall is a major factor for projecting reasonable flood elevations. For 

Centralia, it was opted to go with the 1-day and the 5-day events, and an adjusted water table because 

of the volumetric considerations for the western portion of the watershed. Accordingly, the 100-year / 

24-hour and 5-day storms with the projected initial conditions were considered most reasonable to use 

for this floodplain delineation effort. 

The results of the modeling provided a better indication of the watershed floodplain delineation than 

currently designated by FEMA. The analyses performed projected significantly more floodplain than 

FEMA from a historical and modeling perspective: 2,051 acres – excluding mine floodplains (12.7% of 

the watershed) as compare to 237 acres (1.5% of watershed) for existing FEMA floodplain areas. The 

existing floodplains are broken down as follows: 

 

 

271 acres – associated with major conveyance systems or creeks 

838 acres in depressions 

________________________________________________________________ 





_____________________________________________________________________________ 

900 acres in wetlands 

42 acres transitional 

The maximum floodplain depth is 22.07 feet at a sink located at the terminal end of a conveyance system, 

with an average maximum depth for the nodes throughout the watershed of 2.5 feet. Of the total 

floodplain area of 2,223 acres, approximately 900 acres are 1-foot or less which includes transitional 

areas. Individual depressional floodplains with a maximum depth of 1-foot or less represents about 102 

acres. 

Figure 15 and Exhibit 1 provide the resulting floodplains based upon the modeling and analysis efforts for 

the 100-year events. Table 1 includes elevation and depth information for the modeled floodplains as 

well as apparent flood impacts to roads, yards, houses, etc. on a catchment by catchment basis. Table 1 

data was used to evaluate the reasonableness of the modeled floodplains in comparison to other 

information, such as pot surface information, etc. Information provided in the tables and figures includes: 

basin information, general land cover, flood area, flood depths, and types of flooding. 

In general, floodplain areas increased in the watershed as compared to FEMA. The primary reason for 

the difference is the limited data available to FEMA (terrain and water level data) from which to delineate 

floodplains in comparison to the level of effort conducted under this study. Based on the superiority of 

the terrain information (LiDAR vs. USGS Quadrangle maps), modeling (dynamic vs. steady-state), and 

availability of historical data investigations, the 100-year flood hazards in this study are by far considered 

more reasonable. Historically, FEMA floodplain delineations efforts have been concentrated around 

rivers and connected lakes where level and flow data are available to statistically determine floodplains. 

7.0 FLOODPLAIN JUSTIFICATION 

The goal of this report is to provide information (verification / validation data) that the preliminary 

floodplains developed are reasonable and justified by sound engineering practices. Historical photos, 

high water marks, potentiometric surface maps, well data, statistical analyses, and computer modeling 

were used to determine and verify the floodplains delineated. Evaluation data of subbasin conditions to 

support justifications are provided in Table 1 on a subbasin by subbasin basis. Table 1 data was used 

to evaluate the reasonableness of the modeled floodplains by providing evaluative information and 

floodplain statistics. Comparative floodplain information to existing FEMA information is for the most 

part non-existent. All 877 modeled subbains are listed. 

The vast majority of the floodplain areas delineated have no previous existing FEMA floodplain 

identified. This is not the result of change in watershed conditions (although some areas have 

experienced development and significant land use alterations, especially in the mined areas); but the 

result of the first time holistic watershed floodplain study using the most up-to-date methodologies. The 

newly identified floodplain areas have the benefit of detailed topographical and engineering analyses to 

provide accurate assessment of the flood prone areas even in the small areas that have been identified 

previously by FEMA. Detailed consideration of watershed hydro-geomorphic characteristics has allowed 

for a more refined delineation of the flood prone areas. 

In comparison to riverine floodplain studies, the Centralia watershed does not have comprehensive longterm 

time data from which statistical inferences or complete validation can be made of the floodplain 

results. Reasonableness of model results is based on the model techniques used, and the comparison 

of records of past events where available. Flood results from locations where data were qualitatively 

validated and calibrated were applied systematically throughout the watershed. The flooding that 

occurred in the 1960s is considered the flood of record for these karst coastal areas and was used to 

bracket the expected flood levels from other historical events including the 2004 hurricanes. Available 

information indicates that the 2004 Hurricane season in the Centralia area probably generated what is 

considered a 10- to 20-year flood because of recent historical reoccurrence of similar levels. 

________________________________________________________________ 





_____________________________________________________________________________ 

The 1960 event while known to cause significant flooding in this area, but not well documented, was 

considered a 100-year plus event because the rainfall data from the Brooksville rain gage indicates that 

the flooding was the result of above average rainfall for 3-4 contiguous years, the largest recorded 2- 

year rainfall on record, and the combination of 4 major storm events occurring within a little more than 

year of each other. As a result of this comparative analysis, it is concluded that the floodplain generated 

in this study are reasonable. Floodplains generated in this study are generally considered to be lower 

than what occurred in 1960, but are higher than what occurred in 2004. Results vary depending on 

location within the watershed. 

Evidence suggests that the upper portion of the watershed is more responsive to the 100-year / 24-hour 

event, while the western third of the watershed is responsive to both the 1 and 5-day events and water 

table elevations. It was determined that these two storms provide reasonable estimation of flood hazard 

areas in the Centralia Watershed. Based on the data summarized in the previous sections, the 

engineering methodology relied upon in the estimation of flood prone areas are considered reasonable. 

Accordingly, the delineated floodplains are considered reasonable and their presence and estimated 

depth and extent justified as such. 

8.0 PUBLIC MEETING 

A public meeting was noticed and held at the Southwest Florida Water Management District on July 28, 

2009 regarding the SWFWMD floodplains. As a result of the notification, about 20 inquiries were made 

by attendance or phone call. Of the 20 inquiries, 1 resulted in a field investigation and subsequent 

adjustments to the model to better reflect the conveyance in the area of basins BS1400, BS1500, and 

BS1540 (also see comment geodatabase for location). A channel was investigated that had greater 

flow depth than previously modeled. The watershed DEM, and model conveyance was modified to 

reflect the changes. The residence previously in the floodplain is no longer. Two other inquiries were 

made regarding the addition of a culvert under a driveway, and the removal of insignificant floodplains 

within the property. All others homeowners who had inquiries were in agreement with the results. 

9.0 CONCLUSION 

Based on the information provided herein, the floodplains appear reasonable and justifiable based on 

the available data and the methodology employed. 

10.0 REFERENCES 

Determination of Green-Ampt Parameters For Hydrology computations in ICPR, SWFWMD 

August 2008. 

FEMA Guidelines & Specifications for Flood Mapping Partners, FEMA 2003. 

SWFWMD Guidelines & Specification (G&S), current version with addendums. 

Geohydrologic Reconnaissance of Pasco and Southern Hernando Counties, Florida, USGS and 

Florida Geological Survey, Report of Investigations No. 34, Tallahassee 1964. 

Estimating the Magnitude and Frequency of Floods for Streams in West-Central Florida, 2001, 

Scientific Investigations Report 2005-5080, USGS. 

Well Level and Potentiometric Surface Maps (USGS and SWFWMD) as noted in report. 

Technical Paper No. 49, Two- to Ten-day Precipitation for Return Periods of 2 to 100 Years in the 

Contiguous United States, Weather Bureau, 1964. 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 1: Location Map 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 2: Existing FEMA Floodplain 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 3: 1960 Potentiometric Surface Above Land Surface Areas 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 4: Western Region Floodplain Comparisons 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 5: Corresponding Land Surface and 1960 Potentiometric Surface 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 6: Evaluation Areas for Multi-Day 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 7: Projected 1 and 5-day Elevation Comparison 

________________________________________________________________ 


Two-Sink Area 




_____________________________________________________________________________ 

Figure 8: Two – Sink Area Investigation 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 9: Catchments Selected for Multi-Day Flood Assignment 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 10: Well Levels 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 11: Withlacoochee River and Weeki Wachee Well Levels 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 12: 1960 Potentiometric Surface Overlain On To 1970 Aerial Photos 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 13: Centralia Romp Well with Historic Contours 

________________________________________________________________ 





_____________________________________________________________________________ 

Figure 14: Pasco 16 Well 

________________________________________________________________ 


Suncoast 

Parkway 

US 19 




_____________________________________________________________________________ 

Figure 15: Modeled Floodplain 

________________________________________________________________ 


SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 

SUBBASIN PREDOMINANT 

LANDUSE (RESIDENTIAL, 

COMMERCIAL, 

INSTITUTIONAL, 

AGRICULTURAL, 

TRANSPORTATION, OPEN 

SPACE, OPEN WATER, 

MINING, OTHER) 

SUBBASIN PRIMARY 

MODELED FLOOD 

FEATURE 

(DEPRESSION, WET 

POND, WETLAND, 

CONVEYANCE) 

SUBBASIN DISCHARGE 

CONDITIONS (CLOSED 

BASIN OR POSITIVE 

OUTFALL) 

SUBBASIN INITIAL STAGE 

ASSUMPTIONS (DRY(DTM 

USED)), AERIAL 

INTERPRTATION FOR 

AVERAGE WET WATER 

SURFACE CONTROL 

ELEVATION 

SUBBASIN 

PERCOLATION 

INCORPORATED IN 

MODELING 

SUBBASIN VERIFICATION / 

VALIDATION DATA AVAIILABLE 

(YES OR NO - IF YES PROVIDE 

TABLE 1 

FLOODPLAIN JUSTIFICATION SUMMARY 

CENTRALIA WATERSHED - HERNANDO COUNTY, FL 

(100YR/24HR STORM 12.5" RAINFALL, SCS II FLMOD) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 

BASIN ID JUNCTION ID 

DETAIL) 

or AE) (ACRES) 

BA1015 NA1015 5.64 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 1.48 26.2% 13.82 0.64 11.41% 3.64 0.00 0.64 11.41% -0.84 0 0 0 0 YES 

BA9640 NA9640 3.64 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 13.16 0.93 25.65% 4.02 0.00 0.93 25.65% 0.93 0 0 0 0 YES 

BA9730 NA9730 19.78 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 12.54 4.45 22.50% 2.52 0.29 4.74 23.97% 4.74 0 0 0 0 YES 



BA9880 NA9880 4.32 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 15.04 1.25 28.84% 1.95 0.00 1.25 28.84% 1.25 0 0 0 0 YES 

BA9910 NA9910 7.63 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 14.53 1.78 23.33% 5.22 0.00 1.78 23.33% 1.78 0 0 0 0 YES 

BA9920 NA9920 7.97 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 0.0% 15.04 3.74 46.96% 1.92 0.00 3.74 46.96% 3.74 0 0 0 0 YES 



BA9950 NA9950 14.10 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 4.71 33.4% 13.69 6.10 43.29% 4.36 0.00 6.10 43.29% 1.39 0 0 0 1 YES 

BA9980 NA9980 14.08 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 3.22 22.9% 14.32 2.81 19.98% 4.14 0.00 2.81 19.98% -0.41 0 0 0 0 YES 

BB6860 NB6860 24.48 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 11.81 2.59 10.59% 1.66 0.41 3.00 12.27% 3.00 1 0 0 0 YES 

BB7030 NB7030 8.76 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 12.40 3.79 43.29% 2.28 0.32 4.11 46.94% 4.11 0 0 0 1 YES 

BB7270 NB7270 7.06 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Yes 0.0% 14.52 3.30 46.68% 1.61 0.00 3.30 46.68% 3.30 0 0 0 1 YES 


BB7560 NB7560 16.54 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Off 0.0% 14.57 2.43 14.71% 1.69 0.00 2.43 14.71% 2.43 0 0 0 0 YES 



BB7830 NB7830 8.05 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 15.32 0.00 0.03% 0.00 0.00 0.00 0.03% 0.00 0 0 0 0 YES 

BC2610 NC2610 5.50 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 17.43 0.00 0.05% 0.00 0.00 0.00 0.05% 0.00 0 0 0 0 YES 

BC2620 NC2620 7.70 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 17.17 0.00 0.03% 0.00 0.00 0.00 0.03% 0.00 0 0 0 0 YES 

BC2640 NC2640 20.96 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 1.11 5.3% 8.66 7.92 37.77% 2.83 0.49 8.41 40.10% 7.30 1 0 0 0 YES 

BC2730 NC2730 6.34 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 16.09 1.11 17.49% 5.41 0.00 1.11 17.49% 1.11 0 0 0 0 YES 

BC2880 NC2880 9.14 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 11.53 3.21 35.08% 2.96 0.00 3.21 35.08% 3.21 0 0 0 0 YES 



BC3040 NC3040 11.19 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Yes 0.0% 14.77 2.52 22.52% 1.67 0.00 2.52 22.52% 2.52 0 0 0 0 YES 











BC3930 NC3930 92.61 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 17.52 18.9% 9.14 41.48 44.79% 3.03 0.54 42.02 45.38% 24.50 0 0 0 2 YES 


BD8360 ND8360 13.44 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 4.12 30.7% 10.77 3.99 29.68% 3.73 0.00 3.99 29.68% -0.13 0 0 0 0 YES 


BD8790 ND8790 11.67 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 13.47 2.43 20.83% 3.24 0.00 2.43 20.83% 2.43 2 0 0 0 YES 

BD8970 ND8970 12.85 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 14.27 0.00 0.02% 0.00 0.00 0.00 0.02% 0.00 0 0 0 0 YES 







BD9320 ND9320 3.28 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.75 22.9% 10.77 1.02 30.97% 1.72 0.11 1.13 34.32% 0.38 1 0 0 0 YES 

BD9520 ND9520 28.89 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 13.95 5.57 19.27% 5.15 0.00 5.57 19.27% 5.57 0 0 0 0 YES 


BD9650 ND9650 10.07 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet 1.85 18.4% 13.93 3.27 32.48% 0.59 0.00 3.27 32.48% 1.42 0 0 0 0 YES 




BF7720 NF7720 16.82 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 24.09 0.05 0.28% 0.15 0.00 0.05 0.28% 0.05 0 0 1 1 YES 

BF7750 NF7750 3.61 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 21.27 0.00 0.07% 0.00 0.00 0.00 0.07% 0.00 0 0 0 0 YES 

BF7870 NF7870 6.27 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 0.0% 21.28 0.46 7.33% 3.71 0.00 0.46 7.33% 0.46 1 0 0 0 YES 


BF7890 NF7890 11.20 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 15.52 0.23 2.05% 0.83 0.00 0.23 2.05% 0.23 0 0 0 1 YES 

BF7920 NF7920 6.96 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Nat_Wet 0.0% 19.70 1.28 18.35% 3.37 0.00 1.28 18.35% 1.28 1 0 2 0 YES 



BF8020 NF8020 12.84 100y_5d OPEN SPACE WETLAND CLOSED BASIN Period_Wet 0.0% 17.44 1.24 9.63% 3.00 0.00 1.24 9.63% 1.24 0 0 0 2 YES 

BF8040 NF8040 27.61 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Period_Wet Yes 0.0% 21.49 3.66 13.27% 3.49 0.00 3.66 13.27% 3.66 0 0 3 0 YES 



BF8100 NF8100 29.25 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 4.94 16.9% 9.85 5.47 18.71% 2.59 0.20 5.67 19.39% 0.73 0 0 0 1 YES 


BF8120 NF8120 5.66 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 1.40 24.7% 16.96 1.32 23.27% 4.13 0.00 1.32 23.27% -0.08 0 0 0 0 YES 

BF8150 NF8150 14.85 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 7.50 50.5% 16.10 6.28 42.32% 5.94 0.00 6.28 42.32% -1.22 0 0 0 2 YES 







MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 

OF TOTAL ACRES 

MODELED 

FLOODPLAIN MAX 

DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 

FLOODPLAIN AREA- 

MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 1 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 



BF8280 NF8280 36.61 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 0.0% 19.42 1.64 4.48% 4.72 0.00 1.64 4.48% 1.64 0 0 0 1 YES 

BF8290 NF8290 13.66 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry 0.0% 20.32 0.25 1.81% 1.42 0.00 0.25 1.81% 0.25 0 0 0 0 YES 

BF8310 NF8310 22.23 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet Yes 0.0% 18.70 1.19 5.38% 3.26 0.00 1.19 5.38% 1.19 0 0 0 3 YES 




BF8450 NF8450 34.11 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet 0.0% 15.16 0.00 0.01% 0.00 0.00 0.00 0.01% 0.00 0 0 0 0 YES 





BF8560 NF8560 7.04 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 13.78 0.01 0.14% 0.50 0.00 0.01 0.14% 0.01 0 0 0 0 YES 








BF8890 NF8890 25.70 100y_5d OPEN SPACE WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 19.29 5.13 19.96% 0.70 0.00 5.13 19.96% 5.13 0 0 0 2 YES 




BF9000 NF9000 23.28 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 3.46 14.9% 17.13 0.00 0.01% 0.00 0.00 0.00 0.01% -3.46 0 0 0 0 YES 

BF9010 NF9010 61.39 100y_5d OPEN SPACE DEPRESSION CLOSED BASIN Period_Wet Yes 19.32 11.37 0.76 0.00 0 0 0 3 YES 

BF9020 NF9020 8.03 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet Yes 17.17 0.66 2.91 0.00 0 0 0 1 YES 

BF9030 NF9030 8.91 100y_5d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 19.34 2.12 1.22 0.00 0 0 0 2 YES 

BF9040 NF9040 1.08 100y_1d COMMERCIAL DEPRESSION CLOSED BASIN Dry Yes 16.84 0.20 0.69 0.00 0 0 1 1 YES 




BF9080 NF9080 3.38 100y_1d COMMERCIAL DEPRESSION CLOSED BASIN Dry 20.87 1.04 0.81 0.00 1 0 0 0 YES 



BF9170 NF9170 21.87 100y_5d OPEN SPACE DEPRESSION CLOSED BASIN Dry Off 18.68 6.69 4.97 0.00 1 0 1 0 YES 

BF9180 NF9180 20.64 100y_5d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 17.95 5.29 1.50 0.00 0 0 0 0 YES 


BF9200 NF9200 18.46 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 20.44 2.35 0.99 0.00 1 0 0 1 YES 

BH5140 NH5140 3.46 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Nat_Wet 0.0% 11.62 1.62 46.77% 2.42 0.08 1.70 49.08% 1.70 0 0 0 0 YES 

BH5180 NH5180 16.16 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Nat_Wet 0.0% 11.58 9.57 59.20% 4.19 0.07 9.64 59.63% 9.64 0 0 0 0 YES 

BH5190 NH5190 13.12 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 12.37 3.04 23.15% 2.28 1.08 4.12 31.39% 4.12 1 0 0 0 YES 

BH5250 NH5250 8.24 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Nat_Wet 0.21 2.5% 8.96 1.41 17.08% 0.86 0.00 1.41 17.08% 1.20 0 0 0 0 YES 

BH5360 NH5360 6.77 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 12.31 1.81 26.77% 1.30 0.47 2.28 33.72% 2.28 2 0 0 0 YES 




BH6000 NH6000 88.57 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 16.79 19.0% 13.54 48.88 55.19% 5.48 0.84 49.72 56.13% 32.93 0 0 0 2 YES 

BH6210 NH6210 17.56 100y_5d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 16.26 7.70 43.85% 2.20 0.00 7.70 43.85% 7.70 0 0 0 0 YES 







BH6960 NH6960 24.19 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Yes 0.0% 15.08 2.94 12.14% 2.03 0.21 3.15 13.01% 3.15 1 0 0 0 YES 















BI3800 NI3800 10.16 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 13.29 4.77 46.93% 5.01 0.00 4.77 46.93% 4.77 1 0 0 0 YES 

BI3960 NI3960 10.84 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 20.16 0.07 0.64% 0.11 0.00 0.07 0.64% 0.07 0 0 0 0 YES 


BI4000 NI4000 6.06 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Yes 0.0% 14.80 2.52 41.65% 3.60 0.00 2.52 41.65% 2.52 0 0 0 0 YES 


BI4100 NI4100 9.16 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet Yes 0.0% 16.73 1.94 21.20% 4.30 0.00 1.94 21.20% 1.94 0 0 0 0 YES 










MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 2 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 




BI4520 NI4520 20.69 100y_1d OPEN SPACE WET POND POSITIVE OUTFALL Wet_Dep 0.0% 14.27 2.75 13.29% 2.81 0.00 2.75 13.29% 2.75 1 0 0 0 YES 






BI4730 NI4730 42.86 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Nat_Wet 0.0% 11.05 5.58 13.01% 1.72 3.24 8.82 20.57% 8.82 1 0 0 0 YES 

BI4740 NI4740 12.95 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 31.63 0.04 0.28% 0.46 0.00 0.04 0.28% 0.04 0 1 0 0 YES 


BI4810 NI4810 17.70 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 0.0% 23.44 0.26 1.48% 1.35 0.00 0.26 1.48% 0.26 0 0 1 0 YES 


BI4850 NI4850 6.96 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Off 0.0% 17.07 0.69 9.84% 4.67 0.00 0.69 9.84% 0.69 0 0 0 0 YES 



BI4910 NI4910 21.13 100y_5d OPEN WATER WETLAND CLOSED BASIN Nat_Wet 0.0% 17.43 15.57 73.70% 8.38 0.00 15.57 73.70% 15.57 1 0 0 0 YES 


BI4950 NI4950 1.89 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry 0.0% 37.47 0.00 0.14% 0.00 0.00 0.00 0.14% 0.00 0 0 0 0 YES 


BI4970 NI4970 9.14 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry 0.0% 60.30 0.00 0.04% 0.43 0.00 0.00 0.04% 0.00 0 0 0 0 YES 






BI5100 NI5100 39.11 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 22.95 0.35 0.90% 0.42 0.00 0.35 0.90% 0.35 0 0 1 1 YES 












BI5340 NI5340 93.24 100y_5d OPEN WATER WETLAND POSITIVE OUTFALL Nat_Wet 42.16 45.2% 17.10 64.50 69.18% 9.04 0.01 64.51 69.19% 22.35 0 0 0 3 YES 









BI5520 NI5520 16.47 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 47.55 0.01 0.07% 0.85 0.00 0.01 0.07% 0.01 0 0 0 1 YES 

BI5540 NI5540 25.90 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 14.94 3.76 14.53% 3.31 0.00 3.76 14.53% 3.76 1 0 0 0 YES 


BI5580 NI5580 54.94 100y_1d AGRICULTURAL DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 22.28 2.59 4.71% 0.79 0.00 2.59 4.71% 2.59 0 0 0 2 YES 

BI5620 NI5620 16.00 100y_1d OPEN SPACE WET POND POSITIVE OUTFALL Wet_Dep 0.0% 17.29 0.99 6.20% 3.22 0.00 0.99 6.20% 0.99 2 0 0 0 YES 

BI5630 NI5630 2.41 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Yes 0.0% 17.10 0.57 23.54% 4.77 0.00 0.57 23.54% 0.57 0 0 0 0 YES 



BI5690 NI5690 4.91 100y_1d AGRICULTURAL DEPRESSION POSITIVE OUTFALL Dry 0.0% 39.73 0.01 0.11% 0.66 0.00 0.01 0.11% 0.01 0 0 0 0 YES 

BI5750 NI5750 24.05 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet Yes 0.01 0.0% 17.10 3.35 13.93% 5.02 0.00 3.35 13.93% 3.34 0 0 0 0 YES 

BI5760 NI5760 1.68 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 25.85 0.01 0.64% 0.34 0.00 0.01 0.64% 0.01 0 0 0 2 YES 

BI5770 NI5770 18.98 100y_5d AGRICULTURAL WETLAND POSITIVE OUTFALL Nat_Wet 0.29 1.5% 17.10 8.91 46.96% 5.01 0.00 8.91 46.96% 8.62 0 0 0 2 YES 




BI5910 NI5910 3.84 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 26.20 0.01 0.17% 0.80 0.00 0.01 0.17% 0.01 0 0 1 1 YES 

BI5920 NI5920 9.72 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 22.31 0.01 0.05% 0.91 0.00 0.01 0.05% 0.01 0 0 0 0 YES 


BI5960 NI5960 20.06 100y_1d RESIDENTIAL WETLAND CLOSED BASIN Period_Wet Yes 0.0% 33.24 0.43 2.14% 2.31 0.00 0.43 2.14% 0.43 0 0 0 2 YES 




BI6050 NI6050 4.46 100y_1d AGRICULTURAL WET POND CLOSED BASIN Wet_Dep 0.0% 17.23 1.56 34.99% 3.69 0.00 1.56 34.99% 1.56 0 0 0 0 YES 


BI6080 NI6080 19.23 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 2.41 12.5% 21.78 2.57 13.37% 8.68 0.00 2.57 13.37% 0.16 0 0 1 5 YES 

BI6090 NI6090 32.03 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Nat_Wet 10.79 33.7% 19.44 7.32 22.86% 10.30 0.00 7.32 22.86% -3.47 0 0 3 6 YES 

BI6100 NI6100 57.32 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 4.69 8.2% 16.51 14.72 25.68% 6.55 0.00 14.72 25.68% 10.03 0 0 0 0 YES 

BI6140 NI6140 6.41 100y_1d TRANSPORTATION DEPRESSION CLOSED BASIN Dry Yes 0.0% 20.94 0.15 2.27% 1.57 0.00 0.15 2.27% 0.15 0 0 0 0 YES 



BI6200 NI6200 20.87 100y_1d RESIDENTIAL WETLAND POSITIVE OUTFALL Nat_Wet Yes 0.0% 21.86 1.47 7.04% 4.78 0.00 1.47 7.04% 1.47 0 0 0 3 YES 


BI6270 NI6270 10.98 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Nat_Wet 0.0% 19.44 0.93 8.43% 6.99 0.00 0.93 8.43% 0.93 0 0 1 3 YES 




BI6400 NI6400 25.17 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Nat_Wet 4.33 17.2% 19.43 4.49 17.83% 10.42 0.00 4.49 17.83% 0.16 0 1 0 0 YES 


MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 3 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 










BI6730 NI6730 18.76 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 22.53 1.32 7.02% 1.27 0.00 1.32 7.02% 1.32 0 0 0 0 YES 




BI6930 NI6930 8.77 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 36.63 0.00 0.04% 0.63 0.00 0.00 0.04% 0.00 0 0 0 1 YES 

BI6980 NI6980 16.33 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Nat_Wet Yes 0.0% 17.25 0.21 1.30% 3.73 0.00 0.21 1.30% 0.21 0 0 1 0 YES 




BI7260 NI7260 13.95 100y_5d RESIDENTIAL WETLAND POSITIVE OUTFALL Nat_Wet 0.97 7.0% 19.16 0.66 4.74% 10.10 0.00 0.66 4.74% -0.31 0 0 1 0 YES 

BI7270 NI7270 0.55 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Period_Wet 0.0% 18.54 0.02 4.11% 0.26 0.00 0.02 4.11% 0.02 0 0 0 0 YES 


BI7340 NI7340 12.56 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry 0.0% 22.13 0.32 2.58% 0.73 0.00 0.32 2.58% 0.32 0 0 1 0 YES 




BI7390 NI7390 52.49 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 13.13 25.0% 18.78 10.94 20.85% 8.21 0.00 10.94 20.85% -2.19 0 0 2 2 YES 

BJ0100 NJ0100 1.12 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 0.0% 17.48 0.26 23.01% 0.99 0.00 0.26 23.01% 0.26 1 0 0 2 YES 




BJ0140 NJ0140 16.76 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry 0.0% 16.02 0.05 0.30% 2.22 0.00 0.05 0.30% 0.05 0 0 0 0 YES 

BJ0150 NJ0150 5.07 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 11.99 0.58 11.45% 1.44 0.00 0.58 11.45% 0.58 0 0 0 0 YES 

BJ0180 NJ0180 18.29 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 9.72 6.48 35.43% 2.40 0.71 7.19 39.31% 7.19 1 0 0 0 YES 




BJ0230 NJ0230 13.58 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Nat_Wet 0.0% 9.72 6.62 48.77% 2.59 0.00 6.62 48.77% 6.62 0 0 0 0 YES 


BJ0260 NJ0260 5.74 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Nat_Wet Yes 0.0% 15.98 0.50 8.67% 1.93 0.00 0.50 8.67% 0.50 0 0 0 1 YES 


BJ0300 NJ0300 3.81 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 0.0% 20.04 0.12 3.20% 0.93 0.00 0.12 3.20% 0.12 0 0 0 1 YES 



BJ0350 NJ0350 3.22 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 22.48 0.00 0.14% 0.48 0.00 0.00 0.14% 0.00 0 0 0 1 YES 










BJ0550 NJ0550 2.54 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 22.21 0.04 1.57% 0.11 0.00 0.04 1.57% 0.04 0 0 0 1 YES 

BJ0560 NJ0560 23.45 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 59.55 0.04 0.15% 0.19 0.00 0.04 0.15% 0.04 0 0 1 0 YES 



BJ0640 NJ0640 7.65 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 22.23 0.06 0.74% 0.20 0.00 0.06 0.74% 0.06 0 0 0 1 YES 
















BJ0860 NJ0860 5.58 100y_1d RESIDENTIAL WETLAND CLOSED BASIN Period_Wet Yes 0.0% 19.19 0.23 4.19% 0.46 0.00 0.23 4.19% 0.23 0 0 0 0 YES 



BJ0890 NJ0890 8.72 100y_1d RESIDENTIAL WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 22.46 0.03 0.31% 0.09 0.00 0.03 0.31% 0.03 0 0 0 1 YES 







BJ0970 NJ0970 7.47 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Off 0.0% 13.58 0.83 11.09% 0.69 0.00 0.83 11.09% 0.83 0 0 0 0 YES 

BJ0990 NJ0990 431.82 100y_5d OPEN WATER WETLAND CLOSED BASIN Nat_Wet 0.0% 9.29 267.28 61.90% 4.18 2.86 270.14 62.56% 270.14 0 0 0 0 YES 


MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 4 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 













BJ1160 NJ1160 7.17 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Yes 0.0% 15.31 0.38 5.26% 1.69 0.00 0.38 5.26% 0.38 0 0 0 0 YES 






BJ1230 NJ1230 5.44 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 64.80 0.66 12.13% 0.68 0.00 0.66 12.13% 0.66 0 0 0 3 YES 





































BJ1690 NJ1690 56.27 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Nat_Wet 0.0% 12.55 2.67 4.75% 2.84 0.42 3.09 5.49% 3.09 0 0 0 2 YES 





BJ1760 NJ1760 3.14 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Wet_Dep 0.0% 22.60 0.06 1.87% 0.90 0.00 0.06 1.87% 0.06 0 0 0 1 YES 









BJ1910 NJ1910 21.80 100y_1d RESIDENTIAL WET POND CLOSED BASIN Wet_Dep 0.0% 18.57 1.02 4.70% 7.05 0.00 1.02 4.70% 1.02 0 0 1 3 YES 








BJ2040 NJ2040 16.45 100y_1d RESIDENTIAL WETLAND POSITIVE OUTFALL Nat_Wet Yes 0.0% 18.72 0.70 4.27% 4.07 0.00 0.70 4.27% 0.70 0 0 0 2 YES 


BJ2060 NJ2060 10.05 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Nat_Wet 0.0% 12.92 0.85 8.42% 2.84 0.14 0.99 9.81% 0.99 0 0 0 0 YES 







MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 5 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 












BJ2420 NJ2420 10.36 100y_5d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry Off 0.0% 14.77 2.24 21.58% 2.24 0.00 2.24 21.58% 2.24 0 0 0 2 YES 

BJ2430 NJ2430 15.58 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Off 0.0% 23.98 2.40 15.40% 0.90 0.00 2.40 15.40% 2.40 0 0 2 1 YES 

BJ2440 NJ2440 0.52 100y_1d TRANSPORTATION DEPRESSION POSITIVE OUTFALL Dry 0.0% 13.31 0.00 0.65% 0.65 0.00 0.00 0.65% 0.00 0 0 0 0 YES 

BJ2470 NJ2470 24.78 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry 0.0% 47.04 0.00 0.02% 1.14 0.00 0.00 0.02% 0.00 0 0 0 2 YES 





















BJ2860 NJ2860 1.74 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 31.10 0.01 0.63% 1.46 0.00 0.01 0.63% 0.01 0 0 0 0 YES 









BJ3030 NJ3030 5.85 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry 0.0% 24.70 0.09 1.59% 0.28 0.00 0.09 1.59% 0.09 0 0 0 0 YES 









BJ3250 NJ3250 16.44 100y_5d OPEN SPACE WET POND POSITIVE OUTFALL Wet_Dep 0.0% 14.90 1.64 9.95% 2.89 0.00 1.64 9.95% 1.64 0 0 0 0 YES 












BJ3540 NJ3540 17.55 100y_1d RESIDENTIAL WET POND CLOSED BASIN Dry Yes 0.0% 18.90 1.22 6.95% 3.56 0.00 1.22 6.95% 1.22 0 0 2 1 YES 

BJ3590 NJ3590 7.48 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 25.20 0.00 0.03% 0.00 0.00 0.00 0.03% 0.00 0 0 0 0 YES 







BJ3760 NJ3760 7.33 100y_5d OPEN SPACE WET POND POSITIVE OUTFALL Wet_Dep Yes 0.0% 15.52 2.76 37.60% 3.25 0.00 2.76 37.60% 2.76 0 0 0 1 YES 

BJ3770 NJ3770 24.39 100y_5d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet Yes 0.0% 15.52 7.11 29.16% 3.83 0.00 7.11 29.16% 7.11 0 0 0 4 YES 




BJ3840 NJ3840 14.28 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Off 0.0% 17.07 1.77 12.39% 2.97 0.00 1.77 12.39% 1.77 0 0 0 0 YES 




BJ3900 NJ3900 4.89 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 49.28 0.12 2.42% 0.80 0.00 0.12 2.42% 0.12 0 0 0 1 YES 




MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 6 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 




















BJ4450 NJ4450 27.01 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 46.97 0.61 1.92 0.00 1 0 0 1 YES 







BJ4740 NJ4740 2.45 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 46.14 0.38 1.08 0.00 1 0 0 0 YES 





BK2070 NK2070 23.93 100y_1d RESIDENTIAL CONVEYANCE POSITIVE OUTFALL Dry Yes 0.0% 58.34 12.72 53.17% 4.64 0.00 12.72 53.17% 12.72 0 0 1 2 YES 

BK2080 NK2080 17.39 100y_1d AGRICULTURAL CONVEYANCE POSITIVE OUTFALL Dry Yes 0.0% 54.33 8.62 49.59% 1.91 0.00 8.62 49.59% 8.62 0 0 2 0 YES 

BK3470 NK3470 33.80 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Period_Wet 2.72 8.0% 95.33 3.79 11.21% 4.04 0.40 4.19 12.39% 1.47 0 0 0 1 YES 

BK3490 NK3490 63.89 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Period_Wet 0.0% 100.09 2.57 4.02% 5.48 0.00 2.57 4.02% 2.57 0 0 1 2 YES 

BK3570 NK3570 8.48 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 0.0% 97.83 0.25 2.96% 0.67 0.00 0.25 2.96% 0.25 0 0 1 2 YES 

BK3780 NK3780 17.00 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Period_Wet 0.0% 95.57 1.66 9.76% 4.27 0.26 1.92 11.29% 1.92 0 0 1 0 YES 

BK3790 NK3790 2.39 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry 0.0% 98.11 0.51 21.48% 0.92 0.45 0.96 40.31% 0.96 0 0 0 0 YES 

BK3890 NK3890 43.79 100y_1d TRANSPORTATION WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 89.57 12.63 28.83% 12.27 0.00 12.63 28.83% 12.63 0 0 0 0 YES 

BK4010 NK4010 17.04 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry 0.0% 81.73 0.24 1.40% 2.43 0.03 0.27 1.57% 0.27 0 0 0 4 YES 


BK4060 NK4060 2.26 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 98.57 0.38 16.74% 3.39 0.00 0.38 16.74% 0.38 1 0 1 0 YES 

BK4170 NK4170 42.27 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet 0.0% 96.93 6.02 14.23% 7.80 0.00 6.02 14.23% 6.02 0 0 3 0 YES 

BK4280 NK4280 21.84 100y_1d OTHER WETLAND CLOSED BASIN Period_Wet Yes 0.0% 72.34 0.21 0.98% 1.79 0.00 0.21 0.98% 0.21 0 0 0 2 YES 

BK4310 NK4310 34.04 100y_1d AGRICULTURAL WETLAND CLOSED BASIN Period_Wet Yes 0.0% 86.64 2.99 8.79% 5.53 0.19 3.18 9.35% 3.18 1 0 1 0 YES 

BK4360 NK4360 62.79 100y_1d OPEN SPACE CONVEYANCE POSITIVE OUTFALL Dry Yes 0.0% 72.60 2.56 4.07% 1.53 0.08 2.64 4.20% 2.64 0 0 0 11 YES 

BK4420 NK4420 29.63 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 0.0% 68.46 0.27 0.92% 0.73 0.00 0.27 0.92% 0.27 0 0 0 1 YES 

BK4540 NK4540 9.44 100y_1d TRANSPORTATION WETLAND CLOSED BASIN Period_Wet Yes 0.0% 84.94 1.64 17.38% 6.59 0.11 1.75 18.55% 1.75 0 0 0 0 YES 



BK4690 NK4690 5.06 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 68.07 0.07 1.48% 0.36 0.00 0.07 1.48% 0.07 0 0 0 1 YES 

BK4700 NK4700 9.77 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 62.94 0.15 1.55% 0.89 0.04 0.19 1.96% 0.19 1 0 1 1 YES 

BK4860 NK4860 21.19 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 88.98 0.60 2.82% 0.78 0.00 0.60 2.82% 0.60 0 0 0 1 YES 


BK4920 NK4920 15.16 100y_1d TRANSPORTATION WETLAND POSITIVE OUTFALL Period_Wet 0.0% 93.65 2.06 13.56% 6.15 1.22 3.28 21.61% 3.28 0 0 2 3 YES 







BK5230 NK5230 5.64 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 75.92 0.25 4.42% 2.80 0.00 0.25 4.42% 0.25 0 0 1 0 YES 

BK5250 NK5250 18.13 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry 0.0% 85.68 0.02 0.10% 3.51 0.00 0.02 0.10% 0.02 0 0 0 0 YES 


BK5290 NK5290 5.48 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 78.05 0.36 6.60% 2.93 0.04 0.40 7.33% 0.40 0 0 0 0 YES 

BK5310 NK5310 16.79 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 64.54 3.35 19.93% 12.54 0.25 3.60 21.42% 3.60 0 0 0 1 YES 



BK5410 NK5410 26.89 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Period_Wet 0.0% 72.95 8.68 32.29% 4.61 0.23 8.91 33.14% 8.91 0 0 2 0 YES 

BK5420 NK5420 1.44 100y_1d TRANSPORTATION CONVEYANCE POSITIVE OUTFALL Dry 0.0% 76.80 0.56 38.61% 5.80 0.00 0.56 38.61% 0.56 0 0 0 0 YES 

BK5430 NK5430 35.54 100y_1d RESIDENTIAL CONVEYANCE POSITIVE OUTFALL Dry 0.0% 80.07 4.55 12.80% 4.97 0.25 4.80 13.50% 4.80 0 1 1 0 YES 










BK5750 NK5750 10.88 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Wet_Dep 0.0% 96.28 1.41 12.93% 5.08 0.12 1.53 14.03% 1.53 0 0 1 1 YES 


BK5790 NK5790 21.69 100y_1d AGRICULTURAL WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 67.26 10.30 47.49% 3.44 0.00 10.30 47.49% 10.30 0 0 0 2 YES 




MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 7 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 







BK6250 NK6250 35.08 100y_1d RESIDENTIAL CONVEYANCE POSITIVE OUTFALL Wet_Dep 0.0% 60.84 15.38 43.84% 3.69 0.00 15.38 43.84% 15.38 0 1 2 1 YES 









BK6530 NK6530 12.03 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry 0.0% 135.31 0.00 0.02% 0.00 0.00 0.00 0.02% 0.00 0 0 0 0 YES 

BK6550 NK6550 4.50 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 35.60 0.79 17.46% 3.10 0.30 1.09 24.12% 1.09 0 1 1 3 YES 




















BK7080 NK7080 5.77 100y_1d OTHER DEPRESSION CLOSED BASIN Dry Yes 0.0% 70.02 0.00 0.05% 0.00 0.00 0.00 0.05% 0.00 0 0 0 0 YES 









BK7220 NK7220 7.59 100y_5d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 1.27 16.7% 30.22 2.45 32.29% 20.92 0.00 2.45 32.29% 1.18 0 0 0 0 YES 










BK7540 NK7540 56.29 100y_5d OPEN SPACE WETLAND POSITIVE OUTFALL Period_Wet Yes 1.66 2.9% 30.23 27.58 48.99% 16.98 0.03 27.61 49.05% 25.95 0 2 1 9 YES 











BK7900 NK7900 5.76 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Nat_Wet Yes 0.0% 22.57 0.31 5.39% 7.09 0.00 0.31 5.39% 0.31 0 0 1 3 YES 




















MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 8 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 













BK8740 NK8740 44.95 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Period_Wet Yes 0.0% 22.23 8.07 17.96% 8.60 0.00 8.07 17.96% 8.07 0 1 1 9 YES 












BK8990 NK8990 8.28 100y_1d RESIDENTIAL WET POND POSITIVE OUTFALL Wet_Dep Yes 0.0% 21.53 0.68 8.17% 3.06 0.00 0.68 8.17% 0.68 0 0 2 3 YES 

BK9010 NK9010 15.34 100y_5d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Yes 0.0% 18.47 0.28 1.79% 0.65 0.00 0.28 1.79% 0.28 0 0 0 0 YES 




BK9090 NK9090 21.26 100y_5d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 0.0% 20.92 1.57 7.41% 2.24 0.00 1.57 7.41% 1.57 0 0 0 1 YES 

BK9110 NK9110 57.12 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry Yes 0.13 0.2% 30.82 0.66 1.15% 1.37 0.00 0.66 1.15% 0.53 0 0 0 5 YES 

BK9140 NK9140 72.54 100y_1d RESIDENTIAL WET POND POSITIVE OUTFALL Wet_Dep Yes 0.0% 22.17 1.54 2.12% 3.03 0.00 1.54 2.12% 1.54 0 0 4 8 YES 


BK9180 NK9180 44.28 100y_5d RESIDENTIAL WETLAND CLOSED BASIN Nat_Wet 0.0% 21.45 14.93 33.71% 11.66 0.00 14.93 33.71% 14.93 0 0 1 5 YES 




BK9250 NK9250 22.43 100y_1d RESIDENTIAL WETLAND CLOSED BASIN Nat_Wet 0.0% 23.45 0.98 4.37% 7.27 0.00 0.98 4.37% 0.98 0 0 1 5 YES 

BK9260 NK9260 10.81 100y_5d RESIDENTIAL WET POND CLOSED BASIN Wet_Dep 0.0% 21.68 1.03 9.50% 7.40 0.00 1.03 9.50% 1.03 0 0 1 2 YES 


BK9360 NK9360 3.85 100y_5d OPEN WATER WETLAND POSITIVE OUTFALL Nat_Wet 0.0% 21.45 1.42 36.85% 7.71 0.00 1.42 36.85% 1.42 0 0 0 3 YES 






BK9550 NK9550 47.35 100y_5d RESIDENTIAL WETLAND POSITIVE OUTFALL Nat_Wet 5.03 10.6% 21.21 6.81 14.39% 7.92 0.00 6.81 14.39% 1.78 0 0 8 10 YES 










BL1600 NL1600 11.29 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 74.36 0.17 1.52% 0.35 0.00 0.17 1.52% 0.17 0 0 0 2 YES 

BL1710 NL1710 41.12 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 0.0% 73.28 0.27 0.67% 2.52 0.00 0.27 0.67% 0.27 0 0 0 2 YES 


BL1790 NL1790 19.63 100y_1d TRANSPORTATION WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 93.38 2.20 11.20% 4.90 0.00 2.20 11.20% 2.20 0 0 0 0 YES 

BL1900 NL1900 3.54 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 0.0% 69.50 0.05 1.37% 0.28 0.00 0.05 1.37% 0.05 0 0 0 1 YES 

BL1970 NL1970 11.10 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 55.46 0.25 2.22% 0.43 0.00 0.25 2.22% 0.25 0 0 0 1 YES 

BL2100 NL2100 24.04 100y_1d TRANSPORTATION WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 91.76 3.02 12.56% 12.82 0.00 3.02 12.56% 3.02 0 0 0 0 YES 

BL2110 NL2110 12.51 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 88.12 0.14 1.15% 1.41 0.00 0.14 1.15% 0.14 0 0 0 1 YES 

BL2120 NL2120 9.66 100y_1d OTHER DEPRESSION CLOSED BASIN Dry 0.0% 81.33 0.00 0.03% 0.00 0.00 0.00 0.03% 0.00 0 0 0 0 YES 

BL2130 NL5130 7.78 100y_1d OPEN SPACE CONVEYANCE POSITIVE OUTFALL Dry Yes 0.0% 88.10 0.26 3.40% 0.00 0.00 0.26 3.40% 0.26 0 0 0 12 YES 


BL2190 NL2190 3.51 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry 0.0% 85.26 0.16 4.58% 2.56 0.00 0.16 4.58% 0.16 0 0 0 1 YES 







BL2570 NL2570 7.06 100y_1d OTHER DEPRESSION CLOSED BASIN Dry Yes 0.0% 85.45 0.02 0.34% 0.07 0.00 0.02 0.34% 0.02 0 0 0 1 YES 



BL2690 NL2690 34.12 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 83.32 1.36 3.99% 1.85 0.73 2.09 6.13% 2.09 0 0 0 17 YES 


BL2740 NL2740 14.54 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 0.0% 80.68 0.12 0.80% 0.26 0.00 0.12 0.80% 0.12 0 0 0 2 YES 


BL2800 NL2800 6.63 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry 0.0% 66.07 0.00 0.05% 0.79 0.00 0.00 0.05% 0.00 0 0 0 0 YES 



BL2940 NL2940 46.32 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 1.55 3.3% 82.00 5.88 12.70% 0.00 0.00 5.88 12.70% 4.33 0 0 1 7 YES 


MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 9 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 




BL3090 NL3090 15.39 100y_1d OPEN SPACE CONVEYANCE POSITIVE OUTFALL Dry 0.09 0.6% 81.21 2.72 17.67% 4.22 0.00 2.72 17.67% 2.63 0 0 1 11 YES 




BL3700 NL3700 21.46 100y_1d OTHER CONVEYANCE POSITIVE OUTFALL Dry Yes 0.0% 75.76 2.82 13.16% 5.51 0.00 2.82 13.16% 2.82 0 0 0 6 YES 




BL5170 NL5170 11.07 100y_1d MINING DEPRESSION POSITIVE OUTFALL Dry 0.0% 91.77 0.13 1.19% 1.56 0.00 0.13 1.19% 0.13 0 0 0 0 YES 


BL5190 NL5190 8.48 100y_1d TRANSPORTATION DEPRESSION POSITIVE OUTFALL Dry 0.0% 91.77 0.23 2.69% 5.40 0.00 0.23 2.69% 0.23 0 0 0 0 YES 

BL6000 NL6000 3.97 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Wet_Dep 0.0% 91.91 0.05 1.27% 3.51 0.00 0.05 1.27% 0.05 0 0 0 0 YES 


BM6040 NM6040 3.91 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 60.19 0.01 0.24% 0.23 0.00 0.01 0.24% 0.01 0 0 1 0 YES 

BM6190 NM6190 24.53 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 0.0% 65.60 0.40 1.64% 1.22 0.00 0.40 1.64% 0.40 0 0 0 1 YES 



BM6580 NM6580 10.37 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Off 0.0% 62.23 0.00 0.04% 0.00 0.00 0.00 0.04% 0.00 1 0 0 0 YES 

BM6630 NM6630 15.02 100y_1d OPEN SPACE WETLAND CLOSED BASIN Period_Wet Yes 0.0% 71.01 2.31 15.38% 1.54 0.14 2.45 16.31% 2.45 0 0 0 1 YES 

BM6640 NM6640 16.36 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry Yes 0.0% 58.51 0.00 0.02% 0.00 0.00 0.00 0.02% 0.00 0 0 0 1 YES 

BM6660 NM6660 1.60 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 74.15 0.02 1.03% 0.05 0.00 0.02 1.03% 0.02 0 0 1 0 YES 

BM6810 NM6810 10.33 100y_1d RESIDENTIAL WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 73.55 2.21 21.38% 6.75 0.09 2.30 22.25% 2.30 0 0 0 1 YES 



BM7310 NM7310 49.45 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry 0.0% 94.54 0.62 1.25% 6.04 0.00 0.62 1.25% 0.62 0 0 0 1 YES 

BM7320 NM7320 26.67 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry Yes 0.0% 94.54 0.61 2.28% 6.04 0.00 0.61 2.28% 0.61 0 0 0 0 YES 

BM7330 NM7330 10.12 100y_1d TRANSPORTATION WETLAND POSITIVE OUTFALL Period_Wet Yes 0.0% 87.26 0.77 7.63% 5.99 0.00 0.77 7.63% 0.77 0 0 0 0 YES 

BM7340 NM7340 15.08 100y_1d TRANSPORTATION DEPRESSION POSITIVE OUTFALL Dry 0.0% 76.75 0.36 2.35% 2.06 0.00 0.36 2.35% 0.36 0 0 0 0 YES 

BM7360 NM7360 27.04 100y_1d AGRICULTURAL DEPRESSION POSITIVE OUTFALL Dry 0.0% 92.37 0.04 0.14% 5.00 0.00 0.04 0.14% 0.04 0 0 0 0 YES 


BM7480 NM7480 31.70 100y_1d RESIDENTIAL WETLAND CLOSED BASIN Period_Wet Yes 0.0% 74.04 1.63 5.15% 1.72 0.00 1.63 5.15% 1.63 0 1 1 1 YES 


BM8070 NM8070 3.69 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 95.05 0.02 0.42% 0.03 0.00 0.02 0.42% 0.02 0 0 0 1 YES 

BO0290 NO0290 10.44 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Off 0.0% 14.12 2.48 23.78% 2.88 0.00 2.48 23.78% 2.48 2 0 0 0 YES 

BO0380 NO0380 0.37 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep Off 0.0% 12.99 0.08 22.14% 1.52 0.00 0.08 22.14% 0.08 0 0 0 0 YES 

BO0420 NO0420 0.87 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 12.91 0.15 16.67% 3.57 0.00 0.15 16.67% 0.15 0 0 0 0 YES 

BO0480 NO0480 17.03 100y_1d OPEN SPACE WETLAND CLOSED BASIN Nat_Wet 0.0% 13.58 5.91 34.68% 8.30 0.00 5.91 34.68% 5.91 0 0 0 0 YES 




BO1430 NO1430 1.09 100y_1d OPEN SPACE WET POND CLOSED BASIN Wet_Dep 0.0% 13.49 0.27 24.90% 2.30 0.00 0.27 24.90% 0.27 0 0 0 0 YES 


BQ4490 NQ4490 4.53 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry 0.0% 99.12 1.00 22.15% 3.90 0.00 1.00 22.15% 1.00 0 0 1 0 YES 

BQ4500 NQ4500 9.63 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry 0.0% 99.12 1.75 18.19% 3.05 0.00 1.75 18.19% 1.75 0 0 1 0 YES 

BQ4780 NQ4780 37.97 100y_1d MINING DEPRESSION CLOSED BASIN Dry 0.0% 98.25 12.18 32.07% 13.11 0.02 12.20 32.12% 12.20 0 0 2 2 YES 

BQ4800 NQ4800 8.34 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry 0.0% 98.29 1.10 13.21% 4.15 0.01 1.11 13.32% 1.11 0 0 2 0 YES 

BR1000 NR1000 7.14 100y_1d OPEN SPACE CONVEYANCE POSITIVE OUTFALL Dry 0.0% 103.34 4.69 65.64% 7.84 0.00 4.69 65.64% 4.69 0 0 1 3 YES 




BR1400 NR1400 8.79 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry Yes 0.0% 172.58 0.06 0.68% 5.91 0.00 0.06 0.68% 0.06 0 0 0 0 YES 






BR2100 NR2100 8.48 100y_1d RESIDENTIAL CONVEYANCE POSITIVE OUTFALL Dry 0.0% 186.30 0.27 3.19% 0.61 0.00 0.27 3.19% 0.27 0 0 1 0 YES 



BR2400 NR2400 15.64 100y_1d OPEN SPACE CONVEYANCE POSITIVE OUTFALL Dry Yes 0.0% 129.22 1.11 7.08% 2.72 0.00 1.11 7.08% 1.11 0 0 0 0 YES 




BR2800 NR2800 15.30 100y_1d OPEN SPACE WETLAND POSITIVE OUTFALL Period_Wet 0.0% 153.49 0.38 2.48% 0.79 0.00 0.38 2.48% 0.38 0 0 0 1 YES 

















BR4500 NR4500 6.19 100y_1d AGRICULTURAL DEPRESSION CLOSED BASIN Dry 0.0% 138.72 0.45 7.20% 3.26 0.00 0.45 7.20% 0.45 0 0 2 0 YES 

BR4600 NR4600 21.12 100y_1d RESIDENTIAL DEPRESSION POSITIVE OUTFALL Dry 0.0% 135.57 0.08 0.37% 3.88 0.00 0.08 0.37% 0.08 0 0 0 0 YES 


MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 10 of 11

SUBBASIN 

AREA 

(ACRES) 

MAPPED 

FLOOD 

EVENT 



COMMERCIAL, 


AGRICULTURAL, 





MODELED FLOOD 

FEATURE 



CONVEYANCE) 




OUTFALL) 







ELEVATION 

SUBBASIN 

PERCOLATION 


MODELING 




DETAIL) 

FEMA % OF 

TOTAL AREA 

(ACRES) 

MODEL MODEL 

FEMA AREA (A 






BR5400 NR5400 8.65 100y_1d OPEN SPACE DEPRESSION CLOSED BASIN Dry 0.0% 106.99 1.37 15.85% 2.50 0.00 1.37 15.85% 1.37 0 0 0 0 YES 






BR6000 NR6000 19.69 100y_1d OPEN SPACE DEPRESSION POSITIVE OUTFALL Dry 0.0% 108.79 0.57 2.87% 4.33 0.00 0.57 2.87% 0.57 0 0 0 0 YES 






BR6510 NR6510 6.80 100y_1d RESIDENTIAL WET POND POSITIVE OUTFALL Wet_Dep 0.0% 128.53 0.05 0.67% 4.73 0.00 0.05 0.67% 0.05 0 0 0 1 YES 


BR6800 NR6800 887.87 100y_1d MINING WET POND CLOSED BASIN Wet_Dep 6.02 0.7% 30.49 120.65 13.59% 16.47 0.00 120.65 13.59% 114.63 0 0 0 5 YES 

BR6810 NR6810 6.59 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 139.18 1.74 26.36% 11.74 0.00 1.74 26.36% 1.74 1 0 2 1 YES 


BR6900 NR6900 27.21 100y_1d MINING DEPRESSION CLOSED BASIN Dry 0.0% 64.47 4.40 16.18% 15.06 0.00 4.40 16.18% 4.40 0 0 0 0 YES 







BS1100 NS1100 27.82 100y_1d RESIDENTIAL DEPRESSION CLOSED BASIN Dry 0.0% 95.91 0.24 0.88% 2.55 0.00 0.24 0.88% 0.24 0 0 4 0 YES 

BS1200 NS1200 5.21 100y_1d OPEN SPACE CONVEYANCE POSITIVE OUTFALL Dry 0.0% 95.96 2.82 54.12% 10.26 0.00 2.82 54.12% 2.82 0 0 3 1 YES 

BS1300 NS1300 5.72 100y_1d RESIDENTIAL CONVEYANCE POSITIVE OUTFALL Dry 0.0% 96.09 2.69 46.96% 8.39 0.00 2.69 46.96% 2.69 0 0 2 1 YES 




BS1600 NS1600 5.24 100y_1d OPEN SPACE CONVEYANCE POSITIVE OUTFALL Wet_Dep 0.0% 98.88 5.69 108.51% 7.38 0.00 5.69 108.51% 5.69 0 0 1 1 YES 









MODELED 

FLOODPLAIN 

ELEVATION 

(FEET NAVD) 

MODELED 

FLOODPLAIN 

(ACRES) 

MODELED 

FLOODPLAIN % 


MODELED 


DEPTH (FEET) 

TRANSITIONAL 

(ESTIMATED) 

FLOODPLAIN 

AREA 

TOTAL 


MODELED PLUS 

TRANSITIONAL 

ACRES 

TOTAL 

FLOODPLAIN % 

OF TOTAL AREA 

FLOODPLAIN 

DIFFERENCE - 

MODELED 

MINUS FEMA 

(ACRES) 

APPARENT 

FLOOD 

IMPACT: 

ROADS 

APPARENT 

FLOOD 

IMPACT: 

DWELLINGS 

APPARENT 

FLOOD 

IMPACT: YARDS 

APPARENT 

FLOOD IMPACT: 

VACANT LOTS 

MODELED 

FLOODPALIN 

REASONABLE 

BASED ON 

AVAILABLE 

INFORMATION 

MARCH 2009 11 of 11

Southwest Florida - Hernando County

Create successful ePaper yourself

Delete template?

Save as template?