Fluvial erosion is the is the process by which a river wears away the land. The ability of a river to erode depends on its velocity.
There are two types of erosion that happen at different stages along a river. Vertical (downwards) erosion often occurs in the upper stages of a river whereas lateral (sidewards) erosion typical occurs in the middle and lower stages of a river.
There are four main processes of erosion. These are:
- Abrasion or corrasion
- Hydraulic Action
- Solution or corrosion
What is abrasion or corrosion?
Abrasion, also known as corrasion, is when boulders and stones wear away the river banks and bed. Angular stones, that have entered the channel recently are very effective tools of abrasion. Abrasion is responsible for both lateral and vertical erosion of the river channel.
What is attrition?
Attrition is when the bed load itself is eroded when sediment particles knock against the bed or each other and break, becoming more rounded and smaller.
What is hydraulic action?
Hydraulic action is when the force of fast-flowing water hits the bed and banks and forces water into cracks in the bedrock. Air is compressed in cracks and the repeated changes in air pressure cause the bedrock to weaken. Hydraulic action causes vertical erosion in the upper part of the river and lateral erosion to the banks in the lower stretch of the river. This forms the outside bend in a meander in the middle and lower course. Lateral erosion is partly responsible for the migration of means across a floodplain.
What is solution or corrosion?
Solution, or corrosion, is when acidic water dissolves rocks such as chalk or limestone.