Potholes are holes in the river bed.
They vary in size from a few centimetres to several metres in diameter.
Potholes are formed by corrasion.
Pebbles carried by the river are swirled around on the river bed. This action erodes the rock on the river bed forming potholes.
Over time, they may widen and join with other potholes to form larger potholes, and the whole river bed is deepened.
Rapids are stretches of fast-flowing water tumbling over a rocky-shallow riverbed.
Different resistance among rocks cause rapids.
They are formed when the water goes from one hard rock that resists the water’s erosion to a softer rock that is easier eroded.
As result, the rapids form a series of steps.
Waterfalls occur when a band of hard rock lies across the river with softer rock downstream which is more rapidly eroded.
At first rapids would form but then develop into a waterfall as the softer rock erodes further.
Variations may be caused by the rock structure.
The formation of waterfalls have two ways;
Waterfalls (vertical) formation
The river erodes the less resistant rock more rapidly and this result in a change in the gradient.
Waterfalls (horizontal) formation
A waterfall is formed where there is the sudden fall in height. The river plunges and hits the bottom of the river bed with great force.
Rocks are swirled around to form a deep pool at the river bed known as a plunge pool
Gorges are formed when rivers erode vertically through resistant rocks.
Since these rocks are not easily erode , the sides of the valley remain steep.
Gorges is a deep valley, narrow and steep sided.