Under the generic term Erosion a number of processes are summarized which describe the wearing away and transport of sediments by superficial and underground running water (mainly linear erosion), as well as by snow creep and avalanches and by landslides and slope failures (mainly sheet or surface erosion). Erosion is the opposite process of deposition or accumulation of debris.

Bank erosion Oberrickenbach
Erosion on streambed (bank and bed erosion)
Sheet erosion
Erosion on slopes (sheet erosion)

When abundant water is present (during thunderstorm, high rainfall intensity or long-lasting rainfall, snow melt) the discharge on open slopes has the ability to erode the underground. The erosional processes develop gullies and ravines. In most cases the eroded material is finally transported to a stream. Processes like landslides or mud flows transport additional solids (debris) into mountain torrents