September 24, 2010
This fall, construction is set to begin on a $4 million pop-up floodwall near the National Mall in Washington, D.C. It’s designed to be assembled quickly in the event that torrential rains cause the nearby Potomac River to spill into the city. (Four years ago, heavy storms led to the flooding of buildings like the National Archives and the offices of the IRS.) The ten-foot wall is high enough that it should be able to stop even monster floods like the one in 1942 that caused millions of dollars in damage. But the new barrier will have one glaring flaw.