4. Where does dam related emergencies occur?

In the world there are currently about 50,000 large dams with reservoirs. Large dams are defined as those which are 15 meters high from the foundation to the top, or, if the height is between 5 to 15 metres, those which have a reservoir capacity of more than 3 million cubic meters.
The largest dam in the world, which stores an enormous volume of water, is the Three Gorges Dam (China):

Three Gorges Dam (China):
Hoover Dam in USA (left) and the highest Enguri arch dam in Georgia are very unique dams.

Large dam-related disasters with large consequences can therefore occur anywhere in the world where dams are erected.

Many dams are erected in narrow canyons, which as a rule result from active tectonic motion. In turn, active tectonics means that the area (and dams) are prone to the impact of earthquakes, large landslides and tectonic creep. 
Large floods and human activities can also damage dams. It will be recalled, for example, that a large disaster occurred in Vajont (Italy) due to landslide, that dams were destroyed during World War II in Germany, and that a number of dams failed in India and China due to heavy floods. 

However, there are now a number of new projects with a much larger damage potential than the dams mentioned above. Due to population growth, economic development etc. the risks are steadily growing while safety remains unchanged.

The causes of the largest dam accidents prior to 2000 are presented in the following table:

Failure of Shih-Kang Dam due to Chi-Chi earthquake 1999 (China)
Dam failure due to San Fernando earthquake 1971.

Since 2000, several major dam accidents have occurred all over the world:

  • Extreme rainfall during the 2002 European floods affected the Soběnov dam (Czech Republic)
  • Unexpectedly heavy rain in 2005 affected the Shakidor Dam (Pakistan)
  • A computer/operator error in 2005 affected the Lesterville dam (Missouri, United States); here gauges intended to mark the dam as full were not respected and the reservoir continued to fill.
  • Poor maintenance and heavy monsoon rain in 2009 affected the Taum Sauk reservoir in Tangerang, Indonesia
  • A turbine accident in 2009 affected the Sayano–Shushenskaya dam, Russia