Caersws is in a valley and is on a flood plain, a section of the valley floor that is sometimes covered by the river when it floods

After a period of heavy rainfall further upstream, the River Severn overflows and floods the fields around Caersws. The flooding leaves a deposit of fine silt and mud on the valley floor.

Percy spots another fisherman standing in the river

The river channel is much wider now than it was up in the mountain. A larger river channel means there is less friction, so the water flows faster.

Key vocabulary

Depostion
When the speed of a river decreases it has less energy to carry its load, so it drops it (deposits it).

Sediment
The material that is carried by a river and then deposited.