Agri Business

Dam break analysis must for Mullapperiyar, says expert

| Updated on: Nov 23, 2011
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Kerala cannot afford to delay a ‘dam break analysis' with respect to the century-old Mullapperiyar dam, according to an expert.

Such an analysis will help enhance the state of preparedness when faced with an eventuality, if at all, according to Mr P. M. Pareethu Bava Khan, a former Additional Development Commissioner and Director with the State Institute of Rural Development.

SIMULATING MOVEMENT

The objective of dam-break modelling or flood routing is to simulate the movement of a dam-break flood wave along a valley or indeed any area ‘downstream' that would flood as a result of dam failure.

An expert committee appointed by the State Government has stated that the spillways at downstream Idukki dam do not have the capacity to handle even the probable maximum flood (PMF) discharge from Mullapperiyar, not to speak of a breach.

The PMF of Mullapperiyar basin is 6,003 cumecs (cubic metre per second) while the maximum spillway and outlet capacity provided at the Idukki reservoir is only 5,100 cumecs.

DAM STRENGTH

This means that a big flood in the Mullaperiyar basin itself can endanger the Idukki dam if they are at or near full reservoir levels. All these should raise concerns even if the Mullapperiyar dam is strong enough.

Kerala has some of the oldest dams of the world, Mr Khan said. The level of risk associated with a dam is a function of probability as well as consequences of dam failure.

The fact that the failure of the Mullapperiyar dam could lead to failure of the Idukki dam increases the magnitude of the risk associated with its continued use.

Given the size of Idukki, the extent of the devastation that could result from failure of the dam there is unimaginable, Mr Khan said.

Idukki's reservoir capacity is about 74,400 million cubic feet of water with a weight of more than 2,100 million tonnes.

Evacuation of people in the event of a dam-break from three highly populated districts is practically impossible.

The problem is compounded by the fact that hardly any up-to-date early warning system, emergency action plan, including an evacuation plan, exists.

The National Committee on Dam Safety (NCDS) oversees dam safety activities in various States and suggests improvements to bring these in line with the latest and consistent with Indian conditions.

But its guidelines have been largely observed in their breach, Mr Khan said.

Published on March 12, 2018

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