Floods Unleashed by Dams Should Also Be Part of Dam Safety Concerns

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          In the context of ongoing debates on dam safety and the pending legislation on this increasingly important subject, a neglected aspect is that when no harm is caused to dam structure but nevertheless large-scale damage is done by very excessive and unexpected discharge of flood water then this too should be considered an aspect of the wider understanding of dam safety .

A disturbing aspect of many flood situations in recent years has been that these were caused by sudden and heavy discharge of water from dams. The highly destructive flood in Surat in 2006, for example, were caused by such heavy release of water from Ukai dam. In fact around this time similar damage was reported from some other parts of the country as well. As the  South Asia Network of Dams, Rivers and People reported,  “Mismanagement and negligent operations of the largest reservoirs on Tapi, Narmada, Krishna, Godavari, Mahi and Sabarmati rivers have caused man-made disasters in Gujarat, Maharshtra, Madhya Pradesh, Karnataka and Andhra Pradesh. The big dams that were expected to reduce the floods have actually been responsible for the flood disaster visiting these states now, the states that also happen to have the largest number of big dams.”

It is clear from these disasters that the arrangements for proper regulation and release of water from dams need to be drastically improved. The release of water from dams is broadly of two types. Firstly the routine release and secondly there is the emergency release of water (generally  at the time of heavy rains) which is made when the capacity to absorb any more water does not exist and water has to be released, sometimes in very massive quantities, to prevent the over topping and possible collapse of dam.

In recent decades water releases from dams of the Damodar river system, dams of Bhakra-Beas system, Hirakund dam and several other dams have caused very destructive flash floods. Such floods are different from the gradual rise in river water seen in normal floods. This is like releasing a high wall of water suddenly. Clearly the destructive capacity of such floods is much higher than normal floods.

But officials point out that at times such discharge of water becomes unavoidable as the alternative will be over topping and collapse of dam which will be many times more destructive. However critics do not always accept this explanation. They ask why such a situation arises in the first place. One explanation they give is that due to the pressure to maximise hydropower as much as possible, enough attention is not given to flood-control aspects. Hence when the flood-flows come, there is not enough capacity in the dam reservoir to absorb it and an emergency situation is created which could have been avoided.

.Such situations are more likely to arise towards the end of the  monsoon season or an extended monsoon season if an unexpected torrent of rain comes. Around this it sometimes happens that the flood-control aspect is ignored and there is pressure to concentrate fully on maximising hydro power but when late rains come then destruction can be very high.

In 1988 a very serious flood situation emerged in Punjab due to excessive discharge of water from Bhakra-Pong dams. Bhakra dam, one of India’s biggest and most prestigious dam projects built on Sutlej river – as also its two sister dams built on the Beas river – the Pong and the Pandoh – came in for serious scrutiny following the destructive floods in Punjab and Himachal Pradesh which claimed several lives and destroyed crops and property over a vast area.

Dr. G. S. Dhillon, Prof. of Civil Engineering at Punjab Agriculture University wrote, “Bhakra and Pong, mighty dams that they are, still could not protect Punjab from flood rather discharges from their overfilled reservoirs added to the problem … The has led the people to lose their faith in large dams operated for the purpose of power and irrigation mainly and people feel that the flood control aspect has been neglected by the authorities in charge of operation and maintenance of these dams. If that is not the case, how can flood storage space of the Bhakra dam above EI 1685 be converted into storage in the interest of irrigation and power. It is rumored that the authorities panicked and released the volume stored above EI 1685, they forgot the headworks downstream have limited capacity.”

On the other hand, the BBMB (Bhakra-Beas Management Board) senior officials in their statements took the stand that rather than blame them for the floods, they deserved praise for saving the dam under very adverse conditions and thereby averting a much bigger tragedy. In his talk with newspersons the late Gen. B.N. Kumar, Chairman of the BBMB, made the following statements soon after the disaster –

“We all in Punjab and many others elsewhere were 0.03 inch away from one of the worst catastrophes in living memory during the last week of September when the Bhakra dam’s concrete structure registered a 0.99 inch tilt against its danger mark of 1.04 inches. We have saved the Bhakra dam as its survival was essential, else it would have been all over.

“We mesure the tilt of the dam by a piano-wire – like pensulum, through a hole which runs from top to bottom of the dam. The tilt during these four days (Sept. 24 to Sept. 27 was between 0.95 inches to 0.99 inches against its designed non-seismic tilt of 1.03 inches. In fact Punjab and other parts were 0.04 inches away from disaster.”

Asked what would have happened if Bhakra dam had given away, Gen. Kumar closed his eyes and raised his hands saying – “It is unthinkable, and the very thought is horrifying – we would not be here to review the flood disaster.”

This indicates that the issue of flash floods and excessive discharge of water can be very closely related to that of dam safety. So it is important that dam safety legislation as well as overall dam safety issues should also include issues relating to excessive discharge of water from dams and the resulting flash floods. Artificial separation of these issues or denying relationship of such floods with dam management issues will only make it difficult to avoid or reduce such damage in future. Dam managements should give adequate importance to flood-protection aspects

Bharat Dogra is a journalist and author. His recent books include  Planet in Peril and Man Over Machine.



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