Here's a breakdown of what happens:

* Erosion: Rivers erode the land around them, picking up soil and rock as they flow. This is due to the force of the water and the friction it creates.

* Transportation: The river carries the eroded material, also called sediment, downstream. The size of the sediment that can be carried depends on the speed and volume of the water.

* Deposition: As the river slows down, it loses energy and can no longer carry all the sediment. The heavier sediment is deposited first, usually at the bottom of the river channel. As the river slows down even further, finer sediments are deposited, forming floodplains, deltas, and other landforms.

Deposition is a crucial part of the river's role in shaping the landscape. It creates:

* Floodplains: These are flat areas along the river, formed by deposited sediment during floods.

* Deltas: Triangular-shaped areas of land at the mouth of a river, formed by deposited sediment as the river flows into a larger body of water.

* Alluvial fans: Fan-shaped deposits of sediment at the base of mountains, formed as a river emerges from a narrow canyon onto a wider plain.

Deposition can also have negative consequences, such as:

* Sedimentation in reservoirs: Sediment deposited in reservoirs reduces their capacity and lifespan.

* Coastal erosion: Deposition of sediment at river mouths can alter coastline shapes and lead to erosion.

Overall, deposition is a natural process that plays a vital role in the Earth's landscape, shaping the land and influencing various ecosystems.