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Flood defences 防洪减灾 Dambusterbusters 堤坝除险，以水御水 Some clever, new ways of stopping rivers flooding 防止河水泛滥的绝妙新方法 THE destruction of New Orleans by Hurricane Katrina in 2005. 2005年的卡特利娜飓风摧毁了新奥尔良。 showed the importance of keepingleveesthe artificial banks that contain the flow of partly canalised riversin tip-topcondition. 这场惨剧提示我们部分渠化的河流其人造大坝即使在洪峰到来，河水漫坝的情况下也要挺住而不出现垮塌是多么重要。 In practice, though, that is hard. 然而，实际上这很难做到。 Levees fail for many reasons, not all of them associated with violent storms, 导致堤坝垮塌的原因很多，并非全都是狂风暴雨所致。 and there are so many of them that keeping an eye on all of them is an almost impossibletask. 而且堤坝数量众多，难以对所有的堤坝状况都进行密切监视。 It is good, therefore, to have a backup plan to block up unexpected holes before they cancause too much damage. 因此，事先储备预案极为重要，一旦堤坝出现未曾预料的缺口时能够及时予以封堵，以防造成更大灾难。 | 
