Earthern dams may fail like other engineering structures, due to improper designs faulty construction & lack of maintenance etc.

The various causes leading to failure of earth dam are:

1. Hydraulic failures
2. Seepage failures
3. Structural failures

1. Hydraulic failures:

• About 40% of earth dam failures have been attributed to these causes. The failure under this category may occur due to the following reasons :
• By Overtopping: water may overtop the dam if the design flood is underestimated or spillway is of insufficient capacity or spillway gates are not properly operated.\ Sufficient freeboard should, therefore, be provided.\
• By erosion of upstream face: waves near the top surface of water due to wind try to notch out soil form u/s face & may even sometime cause a slip of upstream slope.\ Stone pitching or riprap should, therefore, be provided.
• Cracking due to frost action: Frost in the upper portion of the dam may cause heavy & cracking of soil with dangerous seepage & failure. An additional freeboard allowance up to a meter of say 1.5m, therefore, be provided.
• Erosion of downstream face by gully formation: Heavy rains falling directly over the down face and the erosion action of moving water lead to the formation of gullies on d/s face, ultimately leading to dam failure. This can be avoided by proper maintenance & providing different pitching or riprap up to a suitable height.

2. Seepage Failures :

• Uncontrolled or concentrated seepage the dam body or through its foundation may to piping or sloughing and cause the failure of the dam.
• Piping is the progressive erosion and subsequent removal of soil grains from within the body of dam or foundations.
• Sloughing is progressive removal of soil from the wet downstream face.
• More than 1/3rd of the earth dams have failed because of these reasons.