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

Chapter 2: Hazard Identification
SMC Multi-jurisdictional Hazard Mitigation Plan
• On 4 February 1998, a powerful nor'easter, carrying heavy moisture from the Gulf of Mexico
and Caribbean region, dumped between 2 and 4 inches of rain across much of Maryland
between the foothills and the Chesapeake Bay. The nor'easter, coming on the heels of one
just a week earlier, caused tides of 3 to 4 feet above normal from the Calvert County/Anne
Arundel County line south to Point Lookout in extreme southeastern St Mary's County; and
along the lower tidal Potomac River along the Charles and St Mary's Counties shoreline,
including Cobb Island and St George Island. A daily rainfall record was broken at
Baltimore/Washington International Airport (BWI); the 1.65 inches that fell on the 4th broke
the 78 year-old Baltimore area mark of 1.48 inches. Flooding was most pronounced in St
Mary's County. During the peak of the storm, 26 roads were closed due the combination of
wind and rain. Nine roads were closed due to flooding alone. State thoroughfares affected
included Routes 5, 237, 238, 243, and 271. Evacuations were initiated in Great Mills and on
St George Island due to rapid increases in tide levels. At least 200 residents were
evacuated, including one 3 year-old boy who required a water rescue. Four fire fighters were
treated for hypothermia at St Mary's Hospital. Some cars were nearly submerged in lowlying
areas. In the Golden Beach neighborhood, Lake White overtopped its banks, and poor
drainage contributed to the widespread flooding. The dam at St. Mary's Lake held; overflow
problems were minimal. The sewage system serving Lexington Park failed due to the
abnormally heavy flow of water, which caused manholes to flood. Four thousand citizens
were affected in St Mary's County. Property damage of $145,000 and crop damage of
$200,000 was reported.
Lightning
Overview
Lightning is defined as a sudden and violent discharge of electricity from within a thunderstorm
due to a difference in electrical charges and represents a flow of electrical current from cloud-tocloud
or cloud-to-ground. Nationally, lightning causes extensive damage to buildings and
structures, kills or injures people and livestock, starts untold numbers of forest fires and
wildfires, and disrupts electromagnetic transmissions. Lightning is extremely dangerous during
dry lightning storms because people remain outside due to the lack of precipitation; however,
lightning is still present during the storm.
At any given time, there are nearly 2,000 thunderstorms in progress over the earth's surface.
There are at least 100,000 thunderstorms annually across the United States. To the general
public, lightning is often perceived as a minor hazard. However, lightning-caused damage,
injuries, and deaths establish lightning as a significant hazard associated with any thunderstorm
in any area of Maryland.
Damage from lightning occurs four ways: (1) electrocution/severe shock of humans and
animals, (2) vaporization of materials along the path of the lightning strike, (3) fire caused by the
high temperatures associated with lightning (10,000-60,000°F) and (4) the sudden power surge
that can damage electrical/electronic equipment. Large outdoor gatherings (e.g., sporting
events, concerts, campgrounds, etc.) are particularly vulnerable to lightning strikes that could
result in injuries and deaths.
Historic Activity
There have been 16 major lightning events in St. Mary’s County between January 1950 and
August 2010, resulting in $662,000 worth property damage. No injuries, fatalities, or crop
damage was reported. Some of these are discussed below:
• A structure was heavily damaged by a fire when lightning struck on 16 July 2000.
Scattered thunderstorms that produced winds in excess of 55 MPH, heavy rainfall, large
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