Rain wash - Usen

...Due to selective erosion, longitudinal rivers that run parallel to the geological structure tend to erode quickly, and transverse rivers that run perpendicular to the geological structure are prone to truncation (drawing the upstream part into their own drainage basin). Rain wash is the process by which rainwater directly erodes the land. Rain erosion includes splash erosion, in which rainwater collides with the ground and moves the soil, rill erosion, in which rainwater flows over the ground and turns into rills, which move the soil particles and create shallow depressions in the ground, sheet erosion, in which numerous rills spread over the ground and erode the land shallowly overall, and gully erosion, in which rills gather and carve gullies. ...

*Some of the terminology that refers to "rain washing" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…選択浸食により地質構造に並行する縦谷河川は浸食の進みが早く，地質構造に直交する横谷河川を截頭(上流部を自己の流域に引き込むこと)しやすい。雨食rain washは雨水が直接に土地を削り取る作用で雨洗ともいう。雨食には降雨が衝突して土を動かす雨滴浸食splash erosion，雨水が地表を流れて細流(リルrill)となり，土粒が動かされて地面に浅いくぼみがつく細流浸食(rill erosionリル･エロージョン)，幾多の細流が地面を覆って広がる布状洪水sheet floodによって土地が全体的に浅く削られる布状浸食sheet erosion，さらに細流が集中して雨裂(雨溝，ガリーgully)を刻むガリー浸食gully erosionが含まれる。…

※「雨洗」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報