17th Street levee

17th Street levee installed as part of annual testing

National Park Service photo

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The 17th Street levee in Washington, D.C. is a critical segment of the larger Potomac Park Levee System that protects downtown and southwestern portions of the city from flooding by the Potomac River. The levee includes permanent floodwalls and berms along much of its length, and at 17th Street — between Constitution Avenue NW and Independence Avenue SW — a removable post-and-panel closure system was installed in 2014 to fill a natural low-lying gap where the permanent earthworks could not provide sufficient flood protection.

In times of high water on the Potomac, panels made of aluminum between steel posts are put in place across 17th Street by the National Park Service to seal off the flood-prone area, thereby safeguarding important federal buildings and infrastructure in the downtown core — including parts of the Federal Triangle neighborhood — from inundation.

The levee system was originally authorized and built in 1939 following a severe flood in 1936, but the 17th Street closure is the result of modern upgrades that replaced older, less reliable sandbag-and-earthen-fill barriers.

Today the 17th Street levee closure is maintained by National Park Service, under the oversight of U.S. Army Corps of Engineers. It is tested once a year, usually in the fall, to ensure that the flood-protection barrier can be deployed effectively if needed.