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打水沟为宝兴河右岸的一级支流,位于宝兴县城城区,流域面积1.01 km2,主沟长度1.85 km,主沟比降640‰。受芦山“4·20”地震的影响,流域中下游直接引发了大量的崩滑体,加之地形陡峻,且位于青衣江-鹿头山暴雨区边缘,极容易发生泥石流。一旦发生泥石流,将会对沟口建筑和人员的安全造成巨大危害。通过对打水沟地震前后遥感影像的解译,结合野外考察,综合判定该沟为地震触发的潜在性泥石流沟。进一步分析估算,由于地震震动导致流域内发育6处崩塌体,总面积20 375 m2,松散固体物质总量为15.20×104m3。在分析泥石流形成条件与发展趋势的基础上,提出了打水沟泥石流减灾方案,并对泥石流排导槽梯形最佳过流横断面进行了设计。通过计算分析得到,在排泄设计标准的泥石流时,排导槽的最佳过流断面宽度为2.38 m,深度为2.23 m。
Dashuigou, a tributary of the right bank of Baoxing River, is located in the urban area of Baoxing County. Its catchment area is 1.01 km2 with a main channel length of 1.85 km and a main channel ratio of 640 ‰. Affected by the Lushan earthquake, the middle and lower reaches of the river basin triggered a large number of landslides directly. In addition, the steep terrain and the edge of the Qingyuejiang-Luutoushan rainstorm area were extremely vulnerable to debris flow. In the event of debris flow, Mizoguchi construction and personnel will cause great harm to the safety. Based on the interpretation of the remote sensing images before and after the Dashigou earthquake and the field investigation, it is concluded that the ditch is a potential debris flow ditch triggered by the earthquake. Further analysis estimates that 6 collapsed bodies were developed in the basin due to the earthquake and the total area was 20 375 m2. The total amount of loose solid matter was 15.20 × 104 m3. Based on the analysis of the formation conditions and development trend of debris flow, a scheme of disaster mitigation for flood ditches was put forward, and the trapezoidal cross section of trapezoid was designed. Through calculation and analysis, it is found that the best cross section width of drainage channel is 2.38 m and the depth is 2.23 m when draining design debris flow.