Rainwash, also spelledrain-wash orrain wash or sometimes calledhillwash, is a process oferosion in which loose surface material is carried away byrainwater that has reached the surface, but has not yet become concentrated intostreams. The term is also applied to the movement under the force of gravity of material loosened by rainwater, or to the material itself.^[1]

Rainwash is sometimes regarded as a combination of two processes:rain-splash, which is the detachment and movement of small soil particles from raindrop impact, andsoil-wash, in which material is moved downslope by surface water flow.^[2]