沙漠沟谷暴雨洪水侵蚀产沙特征

在半干旱区的季节性沙漠沟谷,暴雨引发的洪水过程侵蚀产沙强度大,水土流失严重,对区域及下游河道生态造成严重威胁。以毛布拉孔兑的支沟苏达尔沟为研究对象,以苏达尔沟2011—2015年6次暴雨洪水事件的观测数据为基础,分析洪水流量、泥沙浓度及地表沉积物粒度特征,给出暴雨洪水侵蚀产沙输沙特征。结果表明:观测期间暴雨洪水侵蚀产沙量平均每次约37.69×10~4t,产沙模数为0.57×10~4t·km^-2;其中最大的洪水事件130721号暴雨洪水过程侵蚀产沙量高达90.47×10~4t,产沙模数达1.36×10~4t·km^-2。流域总侵蚀产沙以0.25～0.063 mm泥沙为主,约占总侵蚀量74%。洪水总侵蚀产沙量随暴雨产流强度增强而增加,同时下游沙漠沙地段产沙贡献比重也随之增加,风沙贡献也相应增大。坡面侵蚀约占暴雨洪水总侵蚀的4.37%,且主要集中在上游砒砂岩坡面。

Erosion Sediment Yield Characteristics of Storm-floods in the Ephemeral Desert Watershed

In ephemeral desert river in semi-arid regions, flash floods induced by storm rain can cause a hyper-intensity of erosion sediment yield and make a serious soil and water loss, posing a threat to local ecology-environment system and downstream river system. In this paper, we have chosen Sudaer river as the study area to reveal typical ephemeral desert watershed flood erosion characteristics caused by storm rain, which support water and soil conservation locally and integrated watershed management. Based on analysis for the six storm-floods monitored from 2011 to 2015 in the Sudaer watershed, we have analyzed sediments characteristic of the underlying surface and storm-flood process, and shown erosion sediment yield characteristic induced by flood in this desert watershed. Results show that the total sediment yield of single storm-flood was about 37.69×10⁴ t on average, with a maximum 90.47×10⁴ t of flood event 130721№; specific sediment yield was 0.57·10⁴ t·km^-2 on average, with a maximum 1.36×10⁴ t·km^-2 of flood event 130721№. Main grain fraction of sediments yield caused by storm-flood was 0.25-063 mm that made up about 74% of the total sediment yield. Meanwhile, the lager storm-flood event, the higher sediment yield intensity, and the bigger contribution of the lower desert reaches to total sediment yield, coupled with increased the contribution of aeolian sand. In addition, slope erosion amount accounted for about 4.37%, mainly occurred in the upstream hillslope.