Types of erosion
The energy in a river causes erosion. The bed and banks can be eroded making it wider, deeper and longer.
Headward erosion makes a river longer. This erosion happens near its source. Surface run-off and and throughflow causes erosion at the point where the water enters the valley head.
Vertical erosion makes a river channel deeper. This happens more in the upper stages of a river (the V of vertical erosion should help you remember the v-shaped valleys that are created in the upper stages).
Lateral erosion makes a river wider. This occurs mostly in the middle and lower stages of a river.
There are four main processes of erosion that occur in rivers. These are:
hydraulic action;
abrasion / corrasion;
attrition; and
corrosion.