Pediment

A pediment, also known as a concave slope or waning slope, is a very gently sloping bedrock surface inclined between about half a degree and seven degrees. It typically forms as a concave surface running down from the base of a steeper, retreating desert cliff or escarpment, or around a monadnock or inselberg, and it can persist even after the higher ground behind it has eroded away. Pediments are erosional surfaces: they develop when sheets of running water, called sheet floods, wash across them during intense rainfall, and they may carry a thin cover of gravel washed down from the foot of the mountains. A pediment is not a bajada, which is a merged group of alluvial fans built from material redeposited from canyons rather than bedrock with a thin gravel veneer.