Earth cofferdam is the simplest form of a cofferdam. It is very easy to construct but it is not effective for such places where the depth of water is above 2 m.
The earth is likely to be easily washed away so this type of cofferdams are not suitable where water velocity is high. Its use is limited to small depths of water say up to 2 m.
The width of such dams should not be less than 1 m at the top. And, the sides of the bank should be properly sloped to provide stability and imperviousness. The sides slope of the earth cofferdam depends on the type of soil used for its construction.
Earth cofferdam may be made from a mixture of sand and clay. To prevent scouring effect due to action of water, the side slopes should be protected by covering with rip rap or stone rubble pitching.