Keeping the Water Away

however high they build the artificial riverbanks, the floods keep coming back. And when they come, they seem to be worse than ever. B Engineers are now turning to a different plan: to sap the water's destructive strength by dispersing it into fields, forgotten lakes and flood plains. They are reviving river bends and marshes to curb the flow, and even plugging city drains to encourage floodwater to use other means to go underground. Back in the days when rivers took a winding path to the sea, floodwaters lost force and volume while meandering across flood plains and inland deltas, but today the water tends to have a direct passage to the sea. This means that, when it rains in the uplands, the water comes down all at once. Worse, when the flood plains are closed off, the river's flow downstream becomes more violent and uncontrollable; by turning complex river systems into the simple mechanics of a water pipe, engineers have often created danger where they promised safety. C The Rhine, Europe's most engineered river, is a good example. For a long time, engineers have erased its backwaters and cut it off from its flood plain. The aim was partly to improve navigation, and partly to speed floodwaters out of the Alps and down…