Flooding is more of a risk than most people think, according to the Environment Agency. Five million people already live on the flood plains of England and Wales and the demand for housing means they will be joined by many thousands more. They may never experience the horrors of a Hurricane Katrina but surface run-off after heavy rain wreaks its own devastation, as the residents of Boscastle in Cornwall witnessed in August last year. (The same month 600,000 tonnes of raw sewage overflowed into the Thames when freak storms overtaxed London's creaking sewer system.) Concreting prevents natural drainage through the soil. Vast numbers of new houses, and old drainage systems that already struggle to cope, mean the situation will get worse before it gets any better.
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