Sentence:  <WSD>Corrasion</WSD> may be vertical or lateral. Vertical <WSD>corrasion</WSD> is <WSD>corrasion</WSD> of the bed of the river, deepening its channel. Lateral <WSD>corrasion</WSD> is <WSD>corrasion</WSD> of the banks, and leaves the bed untouched. 
Meaning of the word marked with <WSD> tags:  Corrading (erosion by abrasion) caused by such as: wind-blown or water-borne sand, stream-borne or glacier-borne stones, or collisions between stones under the influence of seaside breakers.