湖南省山洪易发流域起暴区成灾动力学特征研究

Mountain torrent hazard is one of the major natural disasters in Hunan Province. While returning farmland to forests and farmers into the city to enhance the degree of vegetation cover, but Flood disasters and river sediment load is not significantly reduced, and disaster losses show an upward trend. Therefore, the formation mechanism of mountain torrent hazards is necessarily further studied. Three river basins of different rocks whose flood disasters happened in past years are chose to be researched. In which, the DEM diagrams of vegetable cover and soil and geology surface are protracted using remote sensing diagrams and surveyed results on the spot, the information such as: thicknesses, gradients, slopes, and rates of gradients of vegetation and loosen layers is picked up to classified spatially. Combining the capability of remaining rain by vegetation and water retention of soil and characteristic of rain and flow rate on slope and infiltration rate, the moisture content and mass of loosen layers are calculated. Using the theory of slope hydrodynamics and the measured results of friction coefficient between the loosen layer and rock, the stabilities of loosen layers are classified, and the sediment content of runoff are estimated. The quantity and rate of the flow and midstream in sail are estimated using the retention ability of vegetation and loosen layer, and the diversification relationship between the flow quantity and rain is discussed. Then the critical condition of mountain torrent hazard and ability of causing disaster are made certain preliminarily. Comparing the results of three river basins, the veracity of predicting mountain torrent hazard is improved. And all these may afford gist for control flood using ecological and engineering measures.

山洪是湖南省的主要自然灾害之一，尽管全省的植被覆盖度增大，植物量增加，但山洪灾害和河流输沙量并没有明显减少，因此对山洪灾害形成机理有待于进一步探讨。拟在湖南省历年山洪频发区，选择3个典型流域，利用遥感图像和实地测量结果绘制流域的植被、疏松层和母质表层的DEM图，提取坡面植被和疏松层的厚度、坡度、坡向及坡度变化率等信息进行空间分类；结合植被截留能力、土壤保水性能、坡面流速和入渗能力随降雨的变化关系，计算疏松层含水量及径流流速和流量变化，估算河流流量随降雨强度的变化及响应时间；利用力学理论，分析坡面与界面及周边区域的受力情况以及疏松层质量的变化，确定疏松层的非稳定区域及产生滑坡和崩塌的概率，估算出此可能产生的泥沙量，结合各汇流点的流量初步确定其引发山洪的临界条件及成灾能力。比较三个流域研究结果，分析地质和地形引起的差异性，为研究结果全省推广提供基础，并为采取合理的防洪措施提供理论依据。

湖南省山洪易发流域较多，强降雨是导致山洪的主要原因，土壤入渗速率、坡地植被和山体滑坡是影响山洪灾害强度的主要因素，本课题在前人对山洪灾害研究的基础上，从改进土壤入渗仪入手，使之能有效测量林坡地土壤入渗速率，从而较准确地预报土壤与下垫面之间的水分含量及水流速率，结合室内滑坡临界坡度测量结果以及山洪易发流域植被覆盖度、根系分布特征和土壤厚度分布，根据降雨强度和历时的变化，预报山体可能的滑坡区域，将滑坡影响因子加入流域水蚀水文模型，使山洪灾害预报更加准确。本课题将于2017年出版著作1部，已成功申请发明专利1项，正申报了发明专利1项，实用新型专利1项，发表论文13篇，其中SCI论文1篇，培养研究生8人。

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