震后山区小流域山洪泥沙淤积增灾机制研究

The traditional theory of flood disaster is based on flood formation and evolution theory on the ordinary scale, which seldom considers the earthquake impact on the flood and the change of the structure of the loosely packed body, therefore, there are some imperfections on research methods, and also it can not justify the surging disaster mechanism caused by flood sedimentation deposition after the earthquake. Based on the post-earthquake change process of the rainfall - infiltration - runoff coupling mechanism under torrential rain conditions in mountain watershed, and the change relationship between the overland flow and the rainfall, the surface conditions, the project is aimed to reveal the multi-coupling dynamic mechanism of the flood formation and evolution. The research analyses the change relation between the flood evolution and sediment deposition characteristics with valley network morphology, artificial or natural dam system distribution, and degradation of surface conditions, and erects the dynamic process model of "overland flow, convergence evolution , flood hazard ", together with multi- flash process, cross-scale integrated simulation, and forecasting models. Considering the scope of the traditional theory, identifying potential problems, the project tries to propose an improved method and construct flood risk assessment system in earthquake zone. Furthermore, it is expected to supplement and improve the existing theory, and to provide some new insights and solutions to the earthquake prediction and mountain flood prevention.

传统意义的山洪致灾理论是基于普通规模的山洪形成演进理论，考虑强震对山洪过程影响、震后地表植被退化及松散堆积体构成变化较少，研究方法具有一些不完善的地方，难以合理解释地震后山洪泥沙淤积灾害增灾机制。本研究基于震后山区小流域暴雨条件下降雨-土壤入渗-地表产流耦合机制的变化过程和坡面产流随降雨、地表条件的变化关系，揭示山洪形成演进的多过程耦合动力学机制。分析山洪演进与泥沙冲淤特性随沟谷网络形态结构、人工或天然坝系分布、地表条件退化的变化关系，建立"坡面产流、汇流演进、洪水致灾"等基本过程的动力学模型，建立山洪多过程、跨尺度集成模拟方法和预报模型。考量暴雨条件下山洪演进和致灾传统理论的适用范围，找出存在问题，提出改进方法，构建强震区山洪灾害风险评价体系。本项研究成果将会对山洪灾害的形成与演进过程理论进行补充，也将为震后小流域山洪灾害预测和防御工程顺利实施提供一些新见解和解决途径。

山洪灾害的发生受地质、地形及气候等因素的影响，汶川地震产生了大量松散堆积体，使灾区地貌形态发生了较大变化。一般意义的山洪灾害理论是基于普通规模的山洪产生与演进过程理论，考虑强震对山洪泥石流形成的影响及震后沟道河谷松散堆积体构成的变化较少，研究方法上存在一些不完善的地方，难以合理解释震后山洪泥沙淤积灾害增灾机制。.本项目基于汶川地震后小流域暴雨条件下降雨-入渗-产流耦合机制的变化过程和坡面产流随降雨、地表条件（植被、堆积体增加等）的变化关系，运用流域分布式水文模型（WMS HEC-1）模拟碱坪沟流域降雨径流过程，及由强降雨引发的山洪过程，在此基础上对滑坡溃坝动力过程进行试验研究。通过测量水体中的泥沙浓度及不同浓度下的光谱数据，结合遥感图像，构建模型，基于该模型对泥沙浓度进行反演，为遥感技术运用于泥沙水动力研究打下基础。结合遥感技术创建了一种新型方法，完成河流边界信息的提取。运用近景测量和无人机航拍技术，对河道微地貌进行测量，获得河道高分辨率影像。完成了震后山区小流域典型河道的地貌、河流流速测量。在小流域布设3个小型气象站，对土壤湿度和降雨进行实时监测，获得了连续4年的降雨等气象数据。.本研究项目为考量传统暴雨条件下山洪演进和致灾理论的适用范围、研究方法和构建强震区山洪灾害风险评价体系打下基础。研究成果对山洪灾害的形成与演进过程理论进行补充，也将为震后山洪灾害的预测和防治工程顺利实施提供一些新的见解和解决途径。