sheet flood

Japanese: sheet flood（英語表記）sheetflood

…It is also called head erosion or retreat erosion. Normally, no running water is seen at the head of the valley, but when it rains, a sheet flood occurs, which does not form a stream but flows like a sheet, washing away weathered and collapsed materials from the valley wall slope. In addition, groundwater gushing from a spring just downstream of the head of the valley causes the strata above the spring to be undermined. …

From [Erosion]

…Rain wash is the process by which rainwater directly erodes the land. Rain erosion includes splash erosion, in which rainwater collides with the soil and moves it; 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 cover the ground and spread out, resulting in shallow erosion of the land as a whole; and gully erosion, in which rills gather and carve gullies. Rain erosion is most noticeable on gentle slopes such as the foothills of volcanoes, flat surfaces such as continental plateaus, and terraced surfaces, and occurs in places relatively higher than the head of a river valley. …

*Some of the terminology that refers to "sheet flood" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…頭部浸食，後退浸食ともいう。谷頭ではふだん流水を見ないが，降雨時には水流を形成せずに布状に面として流れる布状洪水sheetfloodが発生して谷壁斜面の風化物質や崩壊物質を洗い流す。また，谷頭のすぐ下流側にある泉からの地下水の湧出により，泉の上部にある地層が掘り崩される。…

【浸食作用】より

…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。雨食が目だって作用するのは火山麓のような緩傾斜面や大陸台地のような平たん面や段丘面などであり，河川の谷頭よりも相対的に上位にあたる場所におこる。…

※「sheet flood」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

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