England's Thames Barrier is the world's second-largest (after the Oosterscheldekering in the Netherlands) set of movable floodgates. About 10 miles downriver from central London, the barrier has been in place since 1982 to keep storm surges from overwhelming the city, prompted by the North Sea Flood of 1953, which killed 307 people. The threat of flooding has increased over the years thanks to rising water levels—about eight inches in the last century—and the “tilting” of Britain caused by post-glacial rebound. Plans call for raising the height of the gates 12 inches.