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How do wind and scarce rainfall create pediments dunes dry washes and alluvial fans?

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Davis's proposed landscape-development states
continental landform Davis's proposed landscape-development states. The morphology shown is not actually time-indicative. For example, A could be a gully system in soft sediment or a canyon such as the Royal Gorge in Colorado, which is millions of years old. The ridge-ravine topography of B would normally develop under humid conditions, but the river meandering on alluvium indicates a prior or extraneous non-humid aggrading mechanism. The riverine plain of C implies a complex history of planation and aggradation in a current fluvial mode.

In arid and semiarid environments, the scarcity of rainfall and the prevalence of wind are primary drivers of landscape evolution. These landforms are shaped by the interplay of sporadic, intense water flow and wind-driven sediment transport.123

Water-Driven Landforms

  • Alluvial Fans: These are fan-shaped deposits of sediment that accumulate at the mouths of mountain canyons. In deserts, they are formed by sporadic, intense rainfall or rapid snowmelt that triggers flash floods. As fast-flowing streams exit the confined canyon and enter a wider basin, their velocity drops, causing them to deposit their sediment load.1
  • Pediments: A pediment is a relatively flat bedrock surface found at the base of a mountain or hill. These are shaped by intense, brief rainfall that creates laminar sheet flow across the surface, which gradually erodes and bevels the bedrock.4
  • Dry Washes: Also known as wadis or arroyos, these are steep-sided, usually dry valleys. They are carved by the violent, spasmodic runoff that occurs during rare, heavy desert rainstorms.35

Wind-Driven Landforms

  • Dunes: These are built by wind, which transports sand through saltation (bouncing) and creep. When wind velocity decreases—often due to surface irregularities—sand is deposited, initiating dune growth. Once a dune reaches equilibrium, it migrates as wind erodes the windward slope and deposits sand on the leeward slip face.6

While wind is a significant agent of erosion and transport, running water remains the most effective force in modifying the desert surface.7