Levee gaps could swamp Smithsonian, National Mall

WASHINGTON -- Gaps deliberately left in a Depression-era levee could let as much as 10 feet of water rush over much of downtown Washington, inundating Smithsonian museums holding precious art and American icons and spreading to the base of Capitol Hill.The Justice Department, the Department of Health and Human Services and even the National Weather Service headquarters all could be swamped, along with several hundred homes and scores of commercial office buildings.That's a scenario that could unfold if the levee gaps aren't fixed, say federal officials overseeing the creation of new flood hazard maps for the city."There's a potential here for a lot of impact if this is not closed -- and closed in a timely manner,'' said Steve Gabarino, the U.S. Army Corps of Engineers project manager for the Potomac levee.The District of Columbia's flood-zone is a crescent-shaped area that stretches from the Jefferson and Lincoln memorials to the backyard of the White House and beyond. City officials have pledged to help plug the gaps within 17 months.The Corps built the Potomac Park Levee in 1940, a few years after record flooding had swamped low-lying areas southwest of the White House and Capitol. But the 10-foot high berm was left with several holes where 17th and 23rd Streets cross the National Mall.For nearly 70 years, officials have responded to floodwaters by sending crews to close the levee's gaps with steel plates and sandbags. Since 2000, the Corps has been seeking money to build more permanent pop-up floodgates, and it was largely the absence of such gates that landed the levee on the agency's list of deficient flood structures in 2006.Over the past 200 years or so, the Potomac has surged out of its banks many times, either from heavy rainfalls or tidal surges driven up the river by hurricanes.The Federal Emergency Management Agency's flood maps project that water running through the levee gap near the White House could leave 10 feet of standing water along Constitution Avenue from the Ellipse to the other end of the National Mall, then creep into a natural bowl for another half mile southwest of Capitol Hill. The executive mansion itself, constructed on higher ground, is not at risk of flooding.FEMA had planned to designate the new flood zone effective in September, but agreed to rescind the changes after D.C. officials pledged $2.5 million toward a temporary floodgate installation that could satisfy Corps and FEMA concerns.The permanent floodgate project envisioned by the Corps has a price tag of about $10 million and could take as long as four years to complete.E-mail Lee Bowman at Scripps Howard News Service at bowmanl(at)shns.com.(Distributed by Scripps Howard News Service, http://www.scrippsnews.net)