The DCHomeland Security and Emergency Management Agency (HSEMA) is joining the Federal Emergency Management Agency (FEMA) and the National Oceanic and Atmospheric Administration (NOAA) in encouraging residents to be aware of floodprone areas in their community.  Residents should be familiar with preparation and protective actions they must initiate to protect their families, property and business.  Refer to the “It’s A Disaster”* Preparedness, Prevention and First-Aid guide for more information.

According to the National Weather Service (NWS), floods claim nearly 100 lives and cost billions in property damage in the United States each year.  In many communities, Spring is the peak flood season, however, floods can occur during any time of the year.  Floods have been a persistent problem in the District of Columbia.  The National Capital Planning Commission’s (NCPC) “Report on Flooding and Storm water in Washington, DC” indicates the District is susceptible to four types of flooding:

1. Overbank Flooding–occurs when the river channels receive more rain than they can handle, or when the river channel is blocked and does not permit the water to flow;

2. Urban Drainage Flooding–occurs when the sewer system constructed to handle water runoff is overloaded beyond the design capacity;

3. Levee-Caused Flooding–refers to areas with levees that can be inundated behind the levees because they are relatively flat, and the levee serves as a block to water flowing to the river. Channels may be built and/or pumps are installed to move the water past the levee.

4. Tidal/Storm Surge Flooding–occurs with an abnormal rise in the water level preceding a storm, usually a hurricane, due to the combined effects of wind and low atmospheric pressure. The Potomac, up to the base of Little Falls, is tidal, which causes the river to rise and fall with ocean tides. Normal tides have a mean range of three feet, but have been known to surge as much as 12 feet in a hurricane.

In addition, urban development has increased impervious surfaces, reduced vegetation coverage and further exacerbated flooding and storm water runoff through the entire watershed. Listed below are notable flood events that have occurred in the District:

History of Flood Events
Date	Declaration	Damage Areas
June 1889		Flood on Potomac River Basin (19.5 feet).  Recurrence interval 50 to >100 years
May 12-15, 1924		The flood in the Potomac Basin occurred after several periods of rainfall, the banks of the Chesapeake
March 28-30, 1924		Flood on the Potomac River Basin caused by snowmelt and intense rainfall runoff.  This event resulted in 5 deaths and $4 Million in damages. Recurrence interval 50 to > 100 years.
August 23, 1933		Tidal surge from the Chesapeake-Potomac hurricane of 1933.   Winds greater than 100 mph at landfall.  Tidal surge flood DC to a depth of 10 feet.  Ten people died aboard a train crossing the Anacostia, when flood waters swept the conveyance was swept from the tracks.
March 17-19, 1936		Flood on the Potomac River Basin induced by thick ice, snowmelt and intense rainfall runoff.  $2 million in damages.
April 25-28, 1937		Nor’easter accompanied by heavy rain caused widespread flooding in the entire region.
October 13-17, 1942		Widespread flooding throughout the area causes major damage within the region and the Potomac River.  Flood stage 17.7 ft 03 ft. higher than the 1936 flood (Swenson 1942).  Estimated damages $7.4M
July 1945		Prolonged rainfall produced widespread flooding in the entire region.
September 1952		Hurricane Able caused flooding along Rock Creek.
October 14-16, 1954		Hurricane Hazel accompanied by Heavy rain flooded the Potomac River and its tributaries.
August 1955		Hurricanes Connie and Diane produced heavy rain.  Two events within a 2-week period, resulted in region wide flood damage from Rock Creek, Potomac and Anacostia River basins
June 21-24, 1972		Flood resulted from Hurricane Agnes.  Recurrence interval 50 to >100 years.  Rainfall was 10-inches in the District of Columbia.
September 5-6, 1979		Flood occurred from Hurricane David causing 1.5 times the discharge having a 100-year recurrence interval.
November 4-7, 1985		Hurricane Juan combined with a stationary front caused flooding in the Potomac River basin.  This event is referenced as the “Election Day Flood”. Flood kills three people.  Hundreds of homes and businesses were destroyed.
May 5, 1989		Flood kills three people.  Hundreds of homes and businesses were destroyed.
January 20-23, 1996	Presidential	Flood along the Potomac River Basin (13.9 feet), caused by a combination of snowmelt and rainfall.  Washington DC declared $10M in property damages.
September 16, 1999		Remnants of Hurricane Floyd caused flooding in Northern VA and DC, especially secondary roads.
August 10-12, 2001	Presidential (August 18, 2001)	Flood induced by heavy rainfall (6 inches of precipitation in less than 3 hours).  Flooding exacerbated by an undersized combined sewer system, resulting in the worst flash flood since 1944.
September 18-19, 2003	Presidential	Hurricane Isabel caused a system malfunction in the 14th Street pumping station.  The Incident closed 395 in both directions for 48-Hours.  One motorist required helicopter rescue and three cars were completely submerged under water.   $125M in property damages, winds 75-80 mph flooding on Potomac and Anacostia Rivers.
June 22-23, 2006		A low-pressure front caused heavy precipitation, resulting in localized flooding throughout the region, damaged major Federal buildings, and major highways, including I-495  “the beltway”.  DC sustained $10M in damages.
Source:   District of Columbia Multi-Hazard Mitigation Plan, December 2007

District residents, businesses and visitors should prepare for floods before they occur.  This includes learning the difference between a watch and warning and knowing how to respond if a flood is forecasted for their neighborhood.  For information about how to prepare for and respond to flooding, visit the 72 Hours website. For additional information regarding floodplain management and to determine whether you are in a Special Flood Hazard Area, contact the DC Floodplain Manager at (202) 535-2248.