Dam is a barrier for the flow of water and storage of water for irrigation, power generation, and drinking, it controls flood but it may also cause damages to men and animals and other properties of man. Dam failures are rare but the old ones should be given attention or well maintained. In India there are more than five thousand dams in use. It is not a good policy to construct big dams now. For power generation other methods shall be depended. Small dams can be constructed for irrigation and flood control.

Causes of Dam Failures

Over topping occurs when the water level in a dam is exceeded the capacity of the dam. This may be due to inadequate spillway or settlement of crest of the dam. Over topping occurs because of flash flood, heavy rain in the catchment area, landslides in the reservoir, tsunami. A failure of spillway also is a cause of failure of the dam example Morvi dam Gujarat India 1979.

Piping and Seepage, Earthen Dam Failures are mostly due to piping and seepage. These are semi permeable and can be failed when too much water seeps or leaks through the body of the dam. Dam structure can be weakened due to internal erosion or piping. Example Tenton dam USA 1976.

Defects can occur in the foundation which supports the dam. Concrete dams may fail due to this kind of defect. Supporting soil may be soft that will cause to unequal settlement of the structure. Due to earthquake movement of soil may happen this will also leads to the failure. Example St Francis dam

Poor maintenance and upkeep was the failure cause of Valdi Stava dam Italy

Substandard materials used and technique

Spillway design is poor

Foundation soil, if it is weak that can be a reason

Earthquake, excessive inflow, design error these are all causes the failure of dams.

Recent Dam Failures

First dam failure in India is in 1917, which is due to over topping. There are 36 Dam Failures are reported in India so far. The worst one was Machu dam in 1979. 44% failures were due to flooding 25%over topping due to inadequate spillway capacity, 14% due to piping/bad workmanship and 17% other distress. 30 dams were earthen dams which failed 3 masonry dams and 3 composite dams. All failures occurred in the 5 years after the construction. Majority of dams failed immediately after construction. Machu dam failure was considered because of spillway shutter failure.

The Investigation for Causes of Failure

The unpredictable Machu dam disaster caused destruction of every type of infrastructures. Around 15000 people lost their lives. Investigation was carried out by many agencies

The following observations are made after studying these failures

A good weather forecasting system is needed

Communication should be perfect

Warning system is needed.

Gate operation and maintenance is carried out by experts.

Disaster management plan is studied and implemented

Do not construct dams in earthquake prone areas

Before constructing any big dam rainfall pattern is to be studied.