Dams and Earthquakes

Taking up the call…improving Seismic dam safety.

(March 1, 2002) We cannot ignore the call for increasing the safety of existing dam projects, says Martin Wieland, chairman of ICOLD’s Committee on Seismic Aspects of Dam Design. If we do, opponents of new dams will use concerns over earthquake safety to their advantage.

To DATE, according to reports, the failure of well-engineered dams during an earthquake event has not resulted in any fatalities. Although this is encouraging news, such a favourable performance of dams does not guarantee inherent safety against earthquakes.

For example, during the Bhuj earthquake on 26 January 2001 in Gujarat Province in India, about 200 earth dams were damaged and needed repair and/or strengthening. As the water levels were extremely low during the time of the earthquake, there was no catastrophic release of water from the reservoirs of the severely damaged dams.

Despite the fact that these earth dams, which are less than 30m high, are often built by local communities and differ from the well-engineered dams for hydro power projects, we have to recognise that plenty of similar dams exist all over the world. The water stored behind these earth dams is used mainly for irrigation and water supply.

Furthermore, there are very few large dams which have been exposed to ground motions that may be expected during the maximum credible earthquake (MCE); an event which a dam must be able to resist successfully according to the current guidelines prepared by ICOLD’s Committee on Seismic Aspects of Dam Design.

The Bhuj earthquake also demonstrated that in countries with inadequate earthquake preparedness, strong earthquakes can cause a large number of casualties and huge economic losses. The problem is the largely unknown and often insufficient earthquake safety of existing buildings and infrastructure projects, as earthquake actions may not have been taken into account adequately in their original design.

Although earthquake regulations exist in most countries, if they are followed properly they only apply to new structures. The earthquake safety of many old structures is essentially ignored.

M. Wieland, International Water Power & Dam Construction, March 1, 2002

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