Gully

Japanese: gully

…Furthermore, valley head erosion also occurs, and the length of the valley increases. Small valleys formed in this way are called rain clefts, or gully. Rain clefts form rapidly during rainfall, and muddy water flows down through them, but after rainfall the water level quickly drops and often no running water is seen. …

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. …

From [Mountain climbing]

... A wide grassland covered with torreya and Japanese kaya. A gully is a large rocky groove in a steep rocky mountain. Various terms such as crouarre, linnaeus, and couloir are used for this purpose, but they are generally synonymous.

*Some of the terminology that mentions "gully" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…さらに谷頭浸食も加わって，谷の長さも大きくなる。このようにして形成された小谷を雨裂といい，ガリgullyとも呼ぶ。雨裂は降雨時に急激に形成され，その中を濁流が流下するが，降雨後はたちまち減水し，流水がみられなくなることが多い。…

【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。…