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A dam is a barrier across flowing water that obstructs, directs or slows down the flow, often creating a reservoir, lake or impoundments. Most dams have a section called a spillway or weir over which, or through which, water flows, either intermittently or continuously, and many have hydroelectric power generation systems installed.
Dams are considered "installations containing dangerous forces" under International Humanitarian Law due to the massive impact of a possible destruction on the civilian population and the environment. Dam failures are comparatively rare, but can cause immense damage and loss of life when they arise.
Main causes of dam failure
Common causes of dam failure include:
- Spillway design error (South Fork Dam)
- Geological instability caused by changes to water levels during filling or poor surveying (Vajont Dam, Malpasset)
- Poor maintenance, especially of outlet pipes (Lawn Lake Dam, Val di Stava Dam Collapse)
- Extreme rainfall (Shakidor Dam)
- Human, computer or design error (Buffalo Creek Flood, Dale Dike Reservoir, Taum Sauk pumped storage plant)
Deliberate dam failure
A notable case of deliberate dam failure (prior to the Humanitarian Law rulings) was the British Royal Air Force Dambusters raid on Germany in World War 2 (codenamed "Operation Chastise"), in which three German dams were selected to be breached in order to impact on German infrastructure and manufacturing and power capabilities deriving from the Ruhr and Eder rivers. This raid later became the basis for several films.
List of dam failures
| Dam/incident | Year | Location | Details |
|---|---|---|---|
| Vega de Tera | 1959 | Ribadelago, Spain | |
| Baldwin Hills Reservoir | 1963 | California, USA | Subsidence caused by over-exploitation of local oil field |
| Banqiao and Shimantan Dams | 1975 | China | Extreme rainfall beyond the planned design capability of the dam |
| Big Bay Dam | 2004 | Mississippi USA | |
| Buffalo Creek Flood | 1972 | West Virginia USA | Unstable loose constructed dam created by local coal mining company, collapsed in heavy rain |
| Camará Dam | 2004 | Brasil | |
| Dale Dike Reservoir | 1864 | South Yorkshire, England | Defective construction, small leak in wall grew until dam failed. |
| South Fork Dam | 1889 | Johnstown, Pennsylvania USA | Blamed locally on poor maintenance by owners; court deemed it an "Act of God". Followed exceptionally heavy rainfall. |
| Kelly Barnes Dam | 1977 | georgia USA | Unknown, possibly design error as dam was raised several times by owners to improve power generation. |
| Lawn Lake Dam | 1982 | Rocky Mountain National Park | Outlet pipe erosion; dam under-maintained due to location |
| Malpasset | 1959 | Côte d'Azur, France | Geological fault possibly enhanced by explosives work during construction; initial geo-study was not thorough. |
| Opuha Dam | 1997 | new Zealand | |
| Shakidor Dam | 2005 | pakistan | Unexpectedly extreme rain |
| St. Francis Dam | 1928 | Los Angeles, California | Geological instability that could not have been detected, combined with human error that assessed developing cracks as "normal" for a dam of that type. |
| Taum Sauk reservoir | 2005 | Lesterville, Missouri | Computer/operator error; gauges intended to mark dam full were not respected; dam continued to fill. Minor leakages had also weakened the wall through cavation |
| Teton Dam | 1976 | Idaho USA | Water leakage through earthen wall, leading to dam failure. |
| Tous Dam | 1982 | Valencia, Spain | |
| Vajont Dam | 1963 | Italy | Filling caused geological failure in valley wall, leading to 110 km/h landslide; dam filled with rock, water escaped in a megatsunami. Valley had been (incorrectly) assessed stable. |
| Val di Stava Dam Collapse | 1985 | Italy | Poor maintenance and low margin for error in design; outlet pipes failed leading to pressure on dam. |