Flood Control in the Capital

Many museums, memorials, and federal office buildings lie within the most flood-prone areas of Washington, DC. To ensure that these iconic structures are protected from flooding, NCPC coordinated federal and local efforts to improve the city’s flood defenses and stormwater management.

National Mall Levee Improvements

Currently, if the Potomac River overflows its banks, significant federal office buildings, cultural facilities, private businesses, and city residents are at risk of flooding. Unfortunately, an existing levee that has been in place since the early 1930s doesn’t meet post-Katrina federal standards. As a result, downtown, the Mall, and parts of Southwest Washington are now identified by the Federal Emergency Management Agency as being in the 100-year flood plain. This in turn has triggered new flood insurance requirements for residents, businesses, and major facilities in these areas.

Fortunately, a solution is now on the near horizon. On November 15, 2010 NCPC officials joined with representatives from the National Park Service, the U.S. Army Corps of Engineers, and the District of Columbia to officially announce plans for the construction of a new 17th Street levee that will protect these areas from river flooding. The new levee, funded by the American Recovery and Reinvestment Act, will consist of a removable post and panel closure system across 17th Street and Constitution Avenue, NW.  It will replace an existing earthen levee that requires the use of Jersey barriers, sand bags, and a soil berm.

Diagram of proposed levee system
Overhead view of post and panel closure system

Completion of the project is expected in late 2011 and will cost an estimated $9 million.  The design firm OLIN worked on the design and Hirani Engineering & Land Surveying, P.C. of Jericho, New York will construct the levee improvements.

The project will be implemented in 2 phases:

  • Phase 1: Construction of the closure system
  • Phase 2: Improvements to the system's appearance & integration with the surrounding landscape

Additional information on the levee is available here.

NCPC approved final site development plans for Phase 1 and commented favorably on the concept design for Phase 2 in May 2009. Final approval for Phase 2 occurred in March 2011.


Stormwater Management

NCPC examined flooding risks in the capital city after a June 2006 rainstorm shut down federal buildings in the monumental core and disrupted vital government services.

The Report on Flooding and Stormwater in Washington, DC:

  • Identifies flood risks to the monumental core
  • Outlines regulations governing flood control and stormwater management
  • Describes flood risks east of the Anacostia River
  • Recommends further actions to coordinate policymaking efforts

NCPC—along with other federal, local, and regional agencies—is currently modeling stormwater activity under a variety of conditions and developing strategies to reduce the risk of flooding.

Read more about the capital's flood risks.