The four main forms of river erosion

• Hydraulic action - the force of the river against the banks can cause air to be trapped in cracks and crevices. The pressure weakens the banks and gradually wears it away.
• Abrasion - rocks carried along by the river wear down the river bed and banks.
• Attrition - rocks being carried by the river smash together and break into smaller, smoother and rounder particles.
• Solution - soluble particles are dissolved into the river.