Washout

The washing out or away of earth, etc., especially of a portion of the bed of a road or railroad by a fall of rain or a freshet; also, a place, especially in the bed of a road or railroad, where the earth has been washed away.

the erosive process of washing away soil or gravel by water (as from a roadway); "from the house they watched the washout of their newly seeded lawn by the water"