The stream transports (carries) material that has been eroded (soil, clay, sand, stones).

When this transported material is put down, it is called deposition.

Deposition happens where the water current is weakest (slowest speed). At Woodgate Valley deposition forms stream beaches on the inside of meander bends - where the water current is the slowest.

Most of the time the Bourn Brook is a shallow and gently flowing stream. This means it can usually only transport (carry away) and deposit (put down) very small amounts of material.

After heavy rain the stream is deeper and faster flowing. This means more material is eroded and transported, so there is more material to be deposited on stream beaches. The stream beaches can be seen once the water level has fallen.