Erosion wears away the banks on the outside of a meander bend, to make a stream cliff.

This is because the water current is strongest (fastest speed) on the outside of a bend.

Most of the time the Bourn Brook is a shallow and gently flowing stream. This means it can usually only erode small bits of material from the stream cliff (soil, clay, sand) and transport (carry) it away.

Most of the erosion at the stream cliff happens after heavy rain.

This is because the stream becomes much deeper and faster flowing. It can then erode and transport away more material from the stream cliff.

The material that is transported away (soil, clay, sand, stones) helps erosion. It chips away other bits of the stream bed and banks, when it hits them further down.