小流域拦砂坝上下游冲淤特征调查分析

Investigation and Analysis of Upstream and Downstream Erosion and Sedimentation Characteristics of Check Dams in Small Watershed

极端降水诱发的泥石流具有规模大、沿程侵蚀严重、淤埋范围大等特点,需要在小流域内修建梯级拦砂坝工程进行调控。在汶川地震影响区域内选取33条典型泥石流沟道进行调查,获取了105座拦砂坝特征参数以及梯级拦砂坝作用下的沟道冲淤形态变化,总结了拦砂坝的类型及判别方式,提出了实体坝与透过性坝的4种坝型组合模式、梯级坝的坝间距下2种回淤模式。进一步分析了梯级坝的特征模式(坝型组合模式、回淤模式)对沟道的冲淤形态(回淤坡降折减系数、冲刷深度相对系数)的影响。结果表明实体坝与透过性坝的组合模式(SO、OS模式)对沟道回淤形态影响明显,两种回淤模式中的互馈式运行模式对淤积形态影响显著,回淤相互不影响的独立运行模式下的冲刷作用更强烈。研究结果可为小流域内梯级坝的坝型选择、坝间距优化提供参考。

Debris flows resulting from extreme precipitation exhibit extensive scale,severe erosion along their paths,and substantial sediment deposition,necessitating the implementation of cascade check dam projects in small watersheds for hazard mitigation.In the Wenchuan earthquake-affected area,we investigated 33 typical debris flow gullies and obtained characteristic parameters for 105 check dams,along with the erosion pattern changes in gullies under the influence of cascade check dams.We summarized the types of check dams and their identification criteria and proposed four combinations of solid dams and open dams,as well as two back-silting modes under different spacings of cascade dams.We further analyzed the effects of characteristic patterns of cascade dam(dam type combination mode and back-silting mode)on channel’s erosion and deposition pattern(slope reduction coefficient due to sedimentation and relative erosion depth coefficient).The results indicated that the combination of solid and permeable dams(SO mode and OS mode)significantly influenced the back-silting pattern of channel,and the interactive back-silting mode had a notable impact on deposition pattern,while the independent back-silting operation mode yielded stronger erosion effect.The research findings offer reference for the selection of check dams and the optimization of dam spacing of cascade dams in small watersheds.