In spite of the fact that the processes of erosion, transportation and deposition by running water are the same in both arid and humid lands, the resultant landforms in them differ widely.
There are certain reasons for this, such as the intermittent nature of desert runoff, the absence of a vegetation cover to protect surface materials against erosion, and the lack of drainage flowing through to sea.
One of the most common desert landforms is the channels of the intermittent streams. The rainstorms of the desert lands cut vertical-walled stream channels in unconsolidated alluvium which are called washes or arroyos in the southwest U.S.A., barrancas in Mexico, and Wadis in North Africa and Southwest Asia.
The flash floods in these streams prove most catastrophic to the dwellers in these risk areas. Wherever steep slopes are underlain by clays and shale’s, fast flowing intermittent streams create a maze of V-shaped gullies which create a rugged, complex and barren topography called a badland.
Other examples of badlands can be seen in the Death Valley, California. Where the desert land has been uplifted by tectonic movements, the desert streams and their tributaries cut steep-sided canyons.
Because of the fluvial processes of erosion in the arid areas, flat-topped, steep-sided mesas, capped by resistant layers are formed. Additional erosion from all sides of a mesa reduces it to a smaller remnant without a flat summit called a butte.
Because of the erosion of mountain slopes on the fringe of a desert basin by gully erosion and sheet wash, the slopes gradually retreat, and a new and gently sloping surface of bedrock is created. The new surface thus created is called a pediment.
Sometimes alluvium deposited on the surface of a pediment appears like a water-deposited alluvial fan. However, the layer of alluvium over a pediment is only very thin. About the formation of pediment there is a lot of controversy.