The answer is "Deposition"
When sediment from erosion and weathering of rocks falls or lands somewhere.
erosion
Sediment that builds up on land can come from sources like rocks breaking down, erosion from water, wind, or glaciers, and deposition of materials carried by rivers and streams. Over time, these processes contribute to the formation of soil and landforms.
Wind picks up sediment which causes erosion when it hits the rock.
I'm afraid you've misunderstood sediment, and you can't concatenate two such different structures as you have. Sediment is deposited fragments of material sized from silt up to cobbles or boulders, resulting from weathering and erosion of any rock. Deltas are estuarine deposits of sediment transported suspended in the river, from erosion up-stream. Caves, or most of them anyway, do not result from erosion of sediments, but from the erosion by chemical weathering (dissolution) of sedimentary rock - specifically limestone - and the material is carried away in solution not suspension.
erosion
Weathering breaks down rocks into sediment, which is then transported by erosion to rivers and carried to the delta. Deposition occurs when the velocity of the river decreases as it enters the sea, causing sediment to settle and build up the delta. These processes are essential for shaping and building deltas over time.
A delta. Deltas are landforms created by the deposition of sediment carried by a river as it enters a larger body of water such as an ocean. The sediment accumulates at the river's mouth, building up and forming a flat, often triangular-shaped landform.
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The erosion of sediment by wind, known as aeolian erosion, occurs when wind picks up and carries particles of sediment like sand and dust. These particles are then deposited in new locations, shaping landforms like sand dunes. Aeolian erosion can result in the loss of topsoil and impact ecosystems.
Tributaries can both erode and deposit sediment. In the upper reaches of a tributary, erosion may occur as the flowing water picks up and moves sediment. Closer to the main river, deposition may happen as the velocity of the water slows down and sediment is dropped.
Sediment can build up because of the wind or water.