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How do alluvial fans and bajadas form at the bases of mountains?

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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.

Alluvial fans and bajadas are depositional landforms that develop at the base of mountains as part of an erosional-depositional system.12

Alluvial Fans

An alluvial fan forms when a mountain stream, carrying sediment eroded from higher elevations, emerges from the confines of a canyon into an adjacent, open basin. As the stream exits the canyon, its velocity decreases, causing it to lose the capacity to transport its sediment load. This material is deposited in a fan-shaped pattern, with the apex located at the canyon mouth. These features are particularly prominent in arid and semiarid regions, where they are often shaped by sporadic, high-energy events like flash floods or mudflows.123

Bajadas

A bajada is a broad, gently sloping surface of debris that forms along the base of a mountain front. It is created through the lateral coalescing of several individual alluvial fans. As these fans grow and merge over time, they form a continuous, uniform slope of gravelly alluvium that can extend for several kilometers.42