You do not usually associate deserts with rain but it does rain in deserts. When this happens the desert sand does not soak up water quickly and flash floods occur.
The rain usually pelts down in bucket load sand the runoff from the torrential rains cascades into the steep canyons in a matter of minutes. Walls of water swirl through the canyons picking up mud, trees, and other debris. Plants and animals are caught and swept along the onrushing torrent that takes place without any warning. More people have been killed by floods in the deserts than by thirst.