白龙江流域中游末次间冰期以来泥石流活跃性研究

Debris flows are one of the most serious disasters in the mountainous regions of China. To study the activities (frequency-magnitude) of debris flows under different climatic conditions is pivotal and challenging in the research of hazard prevention and mitigation. The Bailong River is one of the areas that are most severely influenced by debris flows in China. The debris flow deposits of different ages here formed distinct types of alluvial fans, which provide the materials for studying the activities of past debris flows. This study will focus on reconstructing the activities of the debris flows along the mid-stream section of the Bailong River since the Last Interglacial Period using a combined method of geomorphology, sedimentology and chronology. Firstly, the study will map and classify the alluvial fans along the mid-stream section of the Bailong River by image interpretation and field investigation. The study will then analyze the lithofacies that are present in different types of alluvial fans and recognize the lithofacies of debris flows using sedimentary logging. Using the techniques of radioactive carbon 14 and optically stimulated luminescence (OSL) dating, the study will analyze the active periods of debris flows and the associated frequency-magnitude characteristics within each period based on the timing of alluvial fan formation and the temporal sequences of debris flow deposits within each alluvial fan sedimentation. Lastly, the study will discuss the influence of climate on debris flow activities by examining the climatic conditions during each active debris flow period and anticipate the trend of debris flow activities in a changing climate regime. This research is key to hazard prevention and mitigation and national key construction projects.

泥石流是我国山区危害最为严重的灾害之一，不同气候条件下泥石流活跃性（频率-规模）变化是山区地质灾害防治研究中的重点和难点。白龙江流域是我国泥石流灾害影响最严重的区域之一，其河谷两岸发育大量泥石流堆积形成的冲积扇，是研究过去泥石流活跃性的理想区域。本项目将综合采用地貌学、沉积学及年代学的方法研究白龙江流域舟曲-武都段末次间冰期以来泥石流活跃性变化。首先，通过遥感影像解译和野外考察，调查研究区冲积扇的空间分布及发育特征，并对冲积扇及对应流域分类；在此基础上，利用沉积剖面记录研究典型冲积扇的沉积序列并识别泥石流沉积相，并通过放射性碳14和光释光测年技术，系统测定冲积扇的形成时代和泥石流堆积层序的时间序列，分析古泥石流活跃期、频率与规模等特征；进而对比区域气候特征，揭示气候变化对泥石流活跃性的影响，以探讨未来气候条件下泥石流活跃性的变化趋势。该研究对山区地质灾害防治及重大工程建设具有重要意义。

泥石流是我国山区危害最为严重的灾害之一，不同气候条件下泥石流活跃性变化是山区地质灾害防治研究中的重点和难点。尤其是在全球气候变暖以及极端降雨事件增多的情况下，泥石流活跃性的强弱变化趋势是事关国家防灾减灾宏观策略制定的重要依据。白龙江流域是我国泥石流灾害影响最严重的区域之一，其河谷两岸发育大量泥石流堆积形成的冲积扇，是研究过去泥石流活跃性的理想区域。本项目综合采用地貌学、沉积学及年代学的方法研究白龙江流域舟曲-武都段末次冰期以来泥石流活跃性变化。首先，通过遥感影像解译和野外考察，调查研究区冲积扇的空间分布及发育特征，并对冲积扇及对应流域分类；在此基础上，利用沉积剖面记录研究典型冲积扇的沉积序列并识别泥石流沉积相，并通过放射性碳14和光释光测年技术，系统测定冲积扇的形成时代，分析古泥石流活跃期；进而对比区域气候特征，揭示气候变化对泥石流活跃性的影响。..研究发现，不同泥石流沟小流域对气候变化的响应方式不同：流域面积较大的泥石流沟，在气候暖湿的情况下，容易形成洪水，对沟床进行下切侵蚀，不利于泥石流的形成；而流域面积较小的泥石流沟，在气候暖湿的情况下，容易发生坡面滑坡，进而转化为泥石流，形成冲积扇。因此在未来全球变暖及极端降雨事件增多的情况下，应该加强对流域面积较小的泥石流沟的监测以及防治，而对于流域面积较大的沟道，应强化对沟床的保护，防治沟床进一步下切，引发灾害。.