(2) Water Eroded Arid Landforms – Rill, Gully,Ravine, Badland Topography,Bolsons, Playas, Pediments,Bajada etc. In form and function there is no difference between a pediment and an alluvial fan; however,pediment is an erosional landform while a fan is a constructional one. A true pediment is a rock cut surface at the foot of mountains. Bajadas are moderately sloping depositional plains located between pediments and playa. Several alluvial fans coalesce to form a bajada. The intermontane basins in dry regions are generally known as bolsons. Drainage systems, also known as river systems, are the patterns formed by the streams, rivers, and lakes in a particular drainage basin. They are governed by the topography of the land,whether a particular region is dominated by hard or soft rocks, and the gradient of the land.