“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. According to the Army Corps of Engineers, the wall’s design doesn’t take into account future sea-level rise caused by climate change. As the planet warms and the ice caps melt, the seas will begin advancing. In a tidal river like the Potomac, whose height rises and falls with the oceans, that can make a big difference when major storms hit. Every foot of sea-level rise will reduce the floodwall’s effectiveness, making the capital more vulnerable to storm surges.”