特大暴雨条件下小流域沟道的泥沙连通性及其影响因素——以陕西省子洲县为例

[目的]研究特大暴雨条件下小流域沟道泥沙输移路径、泥沙连通程度及其影响因素,旨在探讨水库溃坝的原因,为沟道防洪措施的布设提供依据。[方法]以陕西省子洲县"7·26"暴雨条件下小流域沟道泥沙连通情况为例,选取面积相近、形状相异的清水沟和蛇家沟小流域,对沟道泥沙淤积情况进行现场调查,同时将沟道分为坝地沟段和自然沟段,选取流域面积与形状系数、沟道比降,以及淤地坝的类型与分布进行对比分析两个小流域沟道泥沙连通性的差异。[结果]在此次特大暴雨条件下,清水沟和蛇家沟的淤地坝大都呈现打开状态,由上游到下游清水沟泥沙连通性呈现较强的增长趋势,蛇家沟泥沙连通性则呈现先增长后减弱的趋势。整体上清水沟的泥沙连通性比蛇家沟的强,且清水沟流域的土壤侵蚀也较为严重。串联和混联坝系以及修建有卧管、竖井和排水渠的淤地坝防洪能力更强。[结论]流域面积、流域形状和沟道比降均影响着沟道泥沙的连通性,而淤地坝类型及分布是影响沟道泥沙连通性的主导因子。

Channel Sediment Connectivity and Influence Factors in Small Watersheds Under Extremely Rainstorm -A Case Study at Zizhou County, Shaanxi Province

[Objective] The sediment transport path, sediment connectivity and its influencing factors in the small watershed under the condition of extreme rainstorm of the reservoir were explored in order to explore the causes for dam failure and provide basis for the channel flood control. [Methods] Qingshuigou and Shejiagou small watersheds with similar areas and different shapes were selected to investigate the sedimentation in the channel after the rainstorm event occurred in Zizhou County, Shaanxi Province, on 26th July, 2017. The channel was divided into dam-gully section and natural gully section. The area and the shape coefficient of the watersheds, channel gradient and the type and distribution of check dams were used as factors to analyze the differences in sediment connectivity of the channels between the two small watersheds. [Results] Under the extreme rainstorm, all the check dams in Qingshuigou and Shejiagou were opened. The sediment connectivity showed a strong growth trend from the upstream to the downstream in Qingshuigou watershed, while it increased initially and then decreased in Shejiagou watershed. The sediment connectivity of the Qingshuigou watershed was stronger than that of Shejiagou watershed. Additionally, the soil erosion in Qingshuigou watershed was also more serious than that in Shejiagou watershed. Parallel dam system and hybrid dam systems, as well as check dams with horizontal tubes, shafts and drains showed better flood control capacity. [Conclusion] The area, the shape coefficient of watershed and channel gradient all affect the connectivity of channel sediment, while the type and distribution of check dams are the major factors.