Understanding the changes of sediment concentration in rivers, especially under heavy rains, is of great significance to accurately evaluate the effectiveness of soil and water conservation measures in the Loess Hilly Area. On July 26, 2017, an extremely heavy rain (maximum rain intensity of 66.6 mm/h, the highest rainfall of 256.8 mm in 10 h, and a return period of 100 years) occurred over the 821 km2 Xiaoli River watershed in the Wuding River watershed. In order to understand the sediment concentration during the heavy rain event, 10 dam‐controlled catchments in the center of the rainstorm (3 in the Xiaoli River watershed and 7 in its adjacent watersheds) without drainage and damage were selected. All the retained runoff and sediment in the check dams were measured by the cross‐sectional survey according to the flood marks left by the heavy rain. Combined with the observed runoff and sediment transport data by the hydrological station at the outlet of the Xiaoli River watershed as well as the deposited sediment investigated in the watershed during the heavy rain event, the change of sediment concentration and the role of check dam were analyzed. Results showed that under heavy rain, all the sediment concentrations of runoff in the dam‐controlled catchments ranged from 344 to 552 kg/m3, suggesting that the sediment retaining effect of slope measures (woodland, grassland, and terrace) is limited and cannot prevent the occurrence of hyperconcentrated flows. The gully measures (check dams) in the Xiaoli River watershed can hold a large amount of sediment under heavy rain and make the runoff no longer a hyperconcentrated flow at the watershed outlet. In order to control the transport of hyperconcentrated flows to the downstream, more attention should be paid to the construction of check dams while carrying out vegetation ecological construction in the Loess Hilly Area.

中文翻译：

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黄土丘陵区暴雨期间淤地坝对流域泥沙浓度的影响


了解河流尤其是暴雨条件下河流含沙量的变化，对于准确评价黄土丘陵区水土保持措施的有效性具有重要意义。 2017年7月26日，无定河小李河流域821平方公里出现特大暴雨（最大雨强66.6毫米/小时，10小时最大降雨量256.8毫米，100年一遇）分水岭。为了了解暴雨期间的泥沙浓度，选取了暴雨中心10个未排水、未受损的坝控流域（小沥河流域3个，邻近流域7个）。淤地坝内的截留径流和泥沙全部根据大雨留下的洪水痕迹进行断面测量。结合小澧河流域出口水文站实测径流、泥沙输送资料以及暴雨期间流域调查的沉积泥沙，分析了流域含沙量的变化及淤地坝的作用。结果表明，大雨条件下，坝控流域径流含沙量均在344~552 kg/m3之间，表明坡度措施（林地、草地、梯田）的拦沙效果有限，不能有效阻止水土流失。超集中流动的发生。小沥河流域的沟壑措施（检查坝）可以在大雨时截留大量泥沙，使流域出口径流不再是超浓缩水流。 为了控制超浓水流向下游输送，在黄土丘陵区开展植被生态建设的同时，应更加注重淤地坝的建设。