Vertical Erosion – Downward erosion of a river bed
Vertical erosion makes a river channel deeper. The 'V' of vertical should help you remember the V-shaped valleys that are created by this action.
When the rate of discharge in the upper reaches of a river is high, the riverbed is eroded downwards, usually into a V-shape. This is called vertical erosion. It happens due to the speed of the water and relatively large size of the rock particles it contains.
Lower stretches of the river move slower and the river's load – the sediment it carries – becomes much finer. Here, the river is more prone to lateral erosion (the erosion of the sides, or banks).