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The processes of erosion can create different landforms. The erosional features are often found in the upper course of the river.

Waterfalls and gorges

A waterfall is a sudden drop along the river course. It forms when there are horizontal bands of resistant rock (hard rock) positioned over exposed, less resistant rock (soft rock).

1. The soft rock is eroded quicker than the hard rock and this creates a step.
2. As erosion continues, the hard rock is undercut forming an overhang.
3. Abrasion and hydraulic action continue to erode the soft rock to create a plunge pool.
4. Over time this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses.
5. This process continues and the waterfall retreats upstream.
6. A steep-sided valley is left where the waterfall once was. This is called a gorge.

Interlocking spurs

In the upper course there is more vertical erosion as the river is less powerful, so material cannot be moved in suspension and is instead moved along the river bed using traction or saltation. This erosion, together with the movement of weathered material at the sides of the river, creates the classic V-shaped valley. If there are areas of hard rock which are harder to erode, the river will bend around them. This creates interlocking spurs of land which link together like the teeth of a zip.