What process describes the laying down of material to the bottom of a river?

The laying down of material to the bottom of a river is referred to as deposition. This process occurs when the water's velocity decreases, causing sediment carried by the river to settle out and accumulate on the riverbed. Deposition is crucial in shaping the river's landscape, as it contributes to the formation of features such as sandbars and deltas.

In the context of river systems, deposition can happen during times of lower flow, such as during dry seasons or when rivers widen. It is a natural part of the sediment cycle in a river system, where sediments are transported from upstream areas and eventually deposited downstream. Recognizing deposition helps to understand the overall dynamics of river environments, highlighting how rivers can both erode and build landscapes over time.