- hydraulic action - the pressure of the water breaks rock particles away from the bad and banks. its strongest in rapids and waterfalls and during floods
- abrasion (corrosion) - eroded pieces of rock in the water scrape and rub against the bed and banks, removing material. most erosion of river beds and banks happens by abrasion.
- attrition - eroded rocks smash into each other and break into smaller fragments. their edges also get rounded off as they rub together. attrition doesn't erode the bed and banks - it just makes the particles of rock in the river smaller and more rounded
- cavitation - air bubbles in turbulent stretches of water implode causing shock waves and that break pieces of rock off the banks and bed
- corrosion (solution) - the dissolving of rock by chemical processes. carbon dioxide dissolves in water to form a weak acid, which reacts with rocks like limestone and chalk, breaking them down.
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