A dam is constructed to store large quantity of water, which is used for the purpose of irrigation and power generation. A dam constructed with earth is called an earthen dam whereas a dam constructed with cement concrete is called masonry dam or gravity dam.

A dam may be of any cross- section, but the dams of trapezoidal cross-section are very popular these days. A retaining wall is generally constructed to retain earth in hilly areas.

Bhakara Dam is the highest gravity dam in the world.