Slideshow: Devastating Floods are a Historic and Ongoing Problem for the National Mall

The National Mall Coalition has proposed a way to implement the 2011 recommendations for a floodwater reservoir under the National Mall while also solving other Mall problems that will make the Mall more welcoming, lively, and resilient – the National Mall Underground.

Devastating Floods are a Historic and Ongoing Problem for the National Mall (1889 Photo courtesy Library of Congress)Devastating Floods for the National Mall (1930 Photo courtesy Library of Congress)1942 East Potomac Park and the Jefferson Memorial (Photo courtesy Library of Congress)1985 East Potomac Park with the Washington Monument in the distance (Photo courtesy Library of Congress)In fact, Washington has two separate flood threats: river flooding and stormwater floodingPotomac River flooding has inundated, clockwise from upper left, Pennsylvania Avenue at 6th Street NW in 1889, the Navy Yard in 1936, East Potomac Park (before the Jefferson Memorial) in 1936, and Washington Harbour in Georgetown in 2010The stormwater flood of 2006, by contrast, was caused by runoff from heavy rains on higher ground into this lowest lying part of the city along Constitution Avenue. (Image courtesy Arthur Cotton Moore)This “interior” flooding caused millions of dollars in damage to, clockwise from upper left, federal office buildings, the Department of Justice, the basement theater in the National Archives, and the 12th Street tunnel under the MallThese flooding problems are the result  of Washington’s topography and changes made to rivers and streams over the years This 1793 topographic map by Andrew Ellicott shows the site chosen for the nation’s capital at the confluence of the Potomac and Anacostia (Eastern Branch) Rivers with a broad creek – Tiber Creek – wending its way along the Mall area from the Capitol to the PotomacA satellite view of modern Washington superimposed on Ellicott’s 1793 topographic map shows Tiber Creek (now covered by Constitution Avenue) and the original shorelines of the Potomac and Anacostia (outlined in black).This diagram illustrates that while the levee may prevent Potomac River flooding (the area outlined in red), it will not address the separate interior stormwater flooding problem. No government action has been taken to address the ongoing stormwater flooding threat by implementing the recommendations of the 2011 Federal Triangle Stormwater Drainage Study sponsored by DC Water and the National Capital Planning Commission. Lacking a plan, Metro officials use sandbags to protect the Metro system from stormwater flooding.Washington’s flood threats continue to be well documented in recent government and private studies but no comprehensive plan has been developed

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Flood Control and Resilience with the National Mall Underground

 

 

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