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August 31, 2006
"Almost every year, floods ravage various states. According to news reports in most of the cases, the flood disaster has been caused by panic release of water from dams since inflow to the reservoir was very high. Maharashtra and Gujarat, both hit by floods
this year, together have more than half of the country's 4,500 large dams, so it is a moot point whether dams provide protection from flood.
Flood, a natural phenomenon, becomes a disaster when large quantities of water arrive very quickly or do not recede quickly. Rainwater comes too quickly either because of unprecedented rainfall and/or due to deforestation that causes very fast arrival of water
in the main rivers. A large dam can "control" flood only if the reservoir has sufficient empty capacity to absorb the sudden arrival of water. But in practice, reservoirs are never emptied in anticipation of flood because water from the reservoir is required
for irrigation or power generation. (If it is a low rainfall year
and the reservoir is empty, the flow will merely fill the reservoir and the downstream river will get no water at all). When the flood does arrive, the sluices are opened to save the dam and people, assured of protection from flood, who have occupied the flood
plain below the dam, suffer because of the sudden release of water from the reservoir.
Thus, while large dams may offer flood management advantages in a limited temporal or spatial context, they also create larger magnitude problems that are not generally recognized. Flood management and the performance of India's large dams for flood "control",
irrigation and power generation over the past few decades needs urgent and transparent review."
-Maj Gen S.G.Vombatkere (Retd) is a military engineer holding a PhD in Structural Engineering from I.I.T., Madras.
E-mail: sgvombatkere@hotmail. com
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