2.1 Study area
The research area of this study is the Zhoutungou watershed (36°42’10” N to 36°47’10” N, 109°09’00” E to 109°13’45” E), a typical small watershed in the hilly and gully region of the Loess Plateau, with an average altitude of 1,235.37 m (Fig. 1 (a) and (b)). The annual average temperature is 8.80℃ and annual average rainfall is 550 mm (74% falls from July to Sept.). The soil type is loessial soil of the Zhoutungou watershed. The total watershed area is 33.60 km2, with 18.70 km2 (55.57%) of valleys (Jiang et al. , 1999). The ephemeral gullies are distributed mainly on slope surfaces in the southern region, accounting for about one-third of the slope area. The main measure for ephemeral gully regional governance is planting grasses and shrubs. The main valley in the watershed runs southwest to northeast, with the number of branch valleys gradually increasing from northeast to southwest. The valley and branch valley sections have a ‘U’ or ‘V’ shape, with the terrain of each valley comprising hills, slopes, and channels. In addition, we selected two slope types for field investigations to obtain measured values of ephemeral gully morphological parameters. Slope A is on sunny slopes, with an area of 22,532 m2. Slope B is on shady slopes, with an area of 11,004 m2 (Fig.1 (c)). We investigated 13 ephemeral gullies on slope A and six ephemeral gullies on slope B.