Washout

A washout is the sudden erosion of soft soil or other support surfaces by a gush of water, usually occurring during a heavy downpour of rain (a flash flood) or other stream flooding. These downpours may occur locally in a thunderstorm (particularly in summer, when they are often nearly stationary), or over a large area, such as following the landfall of a tropical cyclone. If a washout occurs in a crater-like formation, it is called a sinkhole, and usually involves a leaking or broken water main or sewerage pipes. (Other types of sinkholes, such as collapsed caves, are not washouts.)