佳芦河流域特大暴雨洪水对下垫面治理的响应

根据实测水文资料，从下垫面治理入手，对佳芦河流域“2012-7-27”暴雨洪水进行了实地调查和成因分析。采用回归分析方法分析了流域洪水泥沙关系和汛期降雨产流关系及其变化，采用“指标法”计算了流域水土保持措施减洪减沙量，并分析了水土保持措施减沙能力和植被措施对流域洪水泥沙的削减作用。结果表明:（1）“2012-7-27”暴雨的雨量、雨强和笼罩面积都很大，但洪峰流量、最大含沙量、洪水量和洪水输沙量却明显减小；流域汛期降雨产流关系具有明显的分区特征，以场次洪水对应的面平均雨量为参数，可以分为暴雨区、大雨区和一般降雨区等3个区。（2）流域水土保持措施削洪减沙作用十分明显。“2012-7-27”暴雨中水土保持措施减洪减沙效益分别达到26.8%和38.3%，其中坝地减洪减沙所占比例最大，分别为71.0%和51.9%，林草等植被措施（包括封禁治理）减洪减沙所占比例其次，梯田减洪减沙所占比例位居第三。（3）植被措施对流域洪水泥沙削减作用显著，但梯田、林地减沙能力均未达到其最大减沙能力，抵御暴雨洪水的空间仍然很大，草地减沙能力约为其最大减沙能力的1.8倍，需要继续加大植被措施建设力度。同时，在流域治理中要继续加大治沟骨干工程建设力度，大力实施“坡改梯”工程。

Response of Extraordinary Rainstorm and Flood to the Harnessing for Underlying Surface in Jialu River Basin

According to the measured hydrological data and the field survey, the factors analysis of ‘2012-7-27’ rainstorm and flood in Jialu River Basin was done based on the harnessing of underlying surface. The relationship of the flood and sediment and the relationship of the rainfall and the runoff in the flood season and its changes of the watershed were analyzed using regression analysis. The flood and sediment reduction of the soil and water conservation measures was calculated using the index method. The ability of soil and water conservation measures on reducing the sediment and the reduction effect of vegetation measures on the flood and sediment of the watershed were analyzed. The results showed that: (1) ‘2012-7-27’ rainstorm rainfall, rainfall intensity and the coverage area were great, but the peak flow, maximum sediment concentration, the amount of flood and flood sediment load significantly reduced; the relationship of the rainfall and runoff of basin had obvious regional features, three zones of rainstorm areas, heavy rain areas and normal rainfall areas were divided corresponding to the average region rainfall related to the flood; (2) the effect of the soil and water conservation measures on reducing the flood and sediment was very obvious, the reduction effect of the soil and water conservation measures on the flood and sediment reached 26.8% and 38.3%, respectively, during ‘2012-7-27’ rainstorm. The reduction effect of the dam on the flood and sediment had the largest ratios, reached 71.0% and 51.9%, respectively. The reduction ratio of forest, grass and other vegetation measures (including closing hillside for afforestation) was the second; the reduction ration of the terrace was the third; (3) the flood and sediment reduction of vegetation measures was significant. The terrace and forest did not reach their maximum capacity of sediment reduction, which have the capability to resisting heavy rain floods. The sediment reduction of grass is about 1.8 times of the maximum capacity of sediment reduction, therefore, the vegetation measures need to be increased. Meanwhile, the key projects of controlling gully in the watershed should increase; the ‘terrace on the slope’ project should be carried out widely.