River processes

River processes and landforms

It is said that 95% of a river’s energy is needed to overcome friction. In a time of flood, the river discharge will increase and there will be an energy surplus. The material known as load is then picked up and carried by the river.

Erosion

A river may erode in any of the following ways

Attrition

This occurs when boulders and rocks are knocked against each other and gradually reduce this stage.

Corrasion

Corrasion occurs when smaller material gets thrown against the riverbanks and erode them.

Corrosion

Corrosion occurs when acids in the river dissolve rocks, such as limestone.

Hydraulic action

Hydraulic action is when the sheer force of the river dislodges rocks from the riverbanks and bed

The formation of a water fall

A waterfall is formed when hard rock is overlying softer rock. The soft rock gets warn away from under the hard rock and so there is an overhang of harder rock which is formed. When the overhang gets too big and can’t support its weight it collapses and so a waterfall is formed. At the bottom of the fall, the water is falling which gains speed. When it gains speed it digs into the rock creating a feature called a plunge pool. Where the waterfall retreats there is a gorge that is formed.