What is the single word for the dry drainage channels thorugh which water flow only in the rains?

Answer 1

A wash or desert wash is normally a dry streambed in the deserts of the American Southwest which flows only after significant rainfall. Washes can fill up quickly during rains, and there may be a sudden torrent of water after a thunderstorm begins upstream, such as during monsoonal conditions. These flash floods often catch travellers by surprise. An intermittent stream can also be called an arroyo in Latin America, or a wadi in the Arabic-speaking world.
http://en.wikipedia.org/wiki/Stream

Answer 2

A Wash

Answer 3

wadi