Tuesday, October 2, 2007

Good article on flood control

Inland flooding is a natural process in most areas of the world, but human settlement and construction along with attempts to out-engineer Nature have complicated the situation. This article was written about a location in India, but refers to the recent flooding experiences in England, France and Belgium as examples of the consequences of building along river banks.

Flood control requires an integrated understanding of hydrology and ecology of the Valvonti river basin. Controlling such floods in future needs joint monitoring and management of Valvonti’s inter-state catchments. There are natural and man-made reasons for the recent flash floods. Natural reasons may include higher rainfall intensity, bottlenecks in the silted streams feeding the tributaries and truncation of the normal flow channels. Man-made reasons could be several but the systematic destruction of the steep slopes of the Virdi hills by plantation owners in the catchment area of Valvonti is a major cause. The floods might have lasted for a few hours but the intensity and consequent damages were far greater this time than in the past. In Keri, Sattari such flash floods were experienced for the first time in 60 years, so the people were caught by surprise, especially as they took place in the night. The government thinks that longer, taller and stronger RCC embankments will control the floods. But these are of limited use if the flood water carries a heavy sediment load and acquires a higher momentum downstream. Embankments which fragment the natural flood plain could actually cause more havoc in the downstream areas.

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