帕隆藏布流域雨型特征及其对降雨型泥石流启动的影响机理

Rainfall-induced debris flows are always neglected by researchers in Parlung Zangbo Valley, Southeast Tibet, while they possess great threaten to local roads, residents and pedestrians and need researchers' attention. Based on the existing research home and abroad, this research designs this program, considering the specialty of rainfall pattern and moraine in this valley. By statistics of rainfall intensity, duration and accumulation rainfall from the 14 rain gauges along Parlung Zangbo, we obtain the rainfall pattern characteristics, and the corresponding rainfall pattern for the historical debris flows in the last 5 years. The field survey and the permeability test can tell the permeability coefficient of the moraine from the rainfall-induced debris flow source area. By combination of rainfall pattern and conductivity coefficient, the debris flows triggering experiments are conducted in Parlung Zangbo Valley. The penetration depth, soil moisture, pore water pressure and volume of the slides are all recorded and analyzed to disclose the influence mechanism of rainfall pattern and permeability coefficient on rainfall-induced debris flow triggering, and also the effectiveness of antecedent rainfall and its influence factors. Achievement of this research can replenish the research of rainfall characteristics in this valley, pave the road for the initiation mechanism, prediction and engineering prevention of rainfall-induced debris flows from moraine, and also provide support for the study of glacier debris flows.

西藏东南部帕隆藏布流域的降雨型泥石流常被研究者所忽视，但其造成的灾害严重，需要进一步研究。本项目在国内外已有研究的基础上，基于流域雨型和冰碛物物源的特殊性进行研究方案设计。项目通过统计分析帕隆藏布流域新增的14个降雨观测站的雨强、降雨历时和累计降雨等基本参数，概化流域降雨的雨型并确定其特征值；在野外调查的基础上，通过渗透实验确定流域降雨型泥石流易发区冰碛土体的渗透系数及其差异；基于雨型和渗透系数的组合，设计并在帕隆藏布流域完成野外泥石流启动实验，分析冰碛土入渗深度、含水量、孔压和启动规模的变化，研究雨型和渗透系数对冰碛土体启动泥石流的影响机理，探讨前期降雨的有效性及其影响因素。研究成果将弥补流域降雨基础研究的缺失，奠定流域降雨型泥石流启动机理、预测评估与工程防治的基础，部分成果还可为冰川型泥石流启动模型研究提供支撑。

西藏东南部帕隆藏布流域的降雨型泥石流常被研究者所忽视，但其造成的灾害严重，需要进一步研究。本项目在国内外已有研究的基础上，详细分析了藏东南地区林芝、波密、察隅和嘉黎四个气象站的日降雨数据，建立了日降雨的规模与频率特征，在此背景下开展了帕隆藏布流域近7年的降雨数据与泥石流事件分析。项目利用沿着帕隆藏布流域新建的培龙、古乡、波密、松宗和米堆雨量站的观测数据，详细分析了雨强、降雨历时和累计降雨等基本参数的分布规律，概化流域降雨的雨型并确定其特征值；综合渗透试验、泥石流启动试验和泥石流阈值发现，流域内泥石流阈值具有较大的差异性，松宗以下的泥石流主要有长历时高强度降雨激发，松宗至玉普的泥石流可由长历时低强度降雨过短历时高强度降雨激发，而玉普以上的泥石流可由短历时低强度降雨激发，而前期降雨的作用在松宗以下较为显著。降雨阈值空间分异的原因主要在于区域气候、植被与土壤特征差异所引起的渗透性差异。研究还发现，冰缘地区泥石流存在较多共性，气候变化导致冰川退缩，冰冻冰碛物转化为活动性冰碛物是高山地区泥石流发育的基础，而物源的进一步演变则影响着转化为泥石流所需要的降雨阈值。研究成果将弥补流域降雨基础研究的缺失，奠定流域降雨型泥石流启动机理、预测评估与工程防治的基础，部分成果还可为冰川型泥石流研究提供支撑。