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    黄土丘陵沟壑区小流域小型浅层滑坡对降雨和下垫面的响应

    Responses of small shallow landslide to rainfall and underlying surface of the small watershed in the loess hilly-gully region

    • 摘要: 受全球气候变化影响,极端暴雨发生频率越来越高,导致山区滑坡易发多发,严重威胁到人们的生命财产安全。利用2013和2020年坊塌小流域逐日降水资料,分析2年诱发滑坡的降雨特征;结合遥感和GIS技术,获取降雨型滑坡的分布特征;进而研究滑坡数量与规模对不同降雨特征及下垫面的响应,并探讨滑坡复发特征。结果表明:1)2013年7月长历时降雨和2020年8月5日暴雨是引发小流域2年滑坡群发的主要原因。2)滑坡类型主要为小型浅层滑坡,2013年比2020年的滑坡规模大,滑坡侵蚀模数分别为6 428.24 t/km2、4 197.40 t/km2。3)≥30°~50°坡度和≥11001250 m高程的区间是滑坡高敏感区间;林灌草区域滑坡较多,且距离道路越近滑坡可能性越大。4)流域内21.9%的滑坡复发,其中近90%的滑坡复发面积减小,部分滑坡出现多处小规模的复发。研究结果可为今后暴雨天气造成的滑坡侵蚀灾害的应对和防治提供科学依据。

       

      Abstract:
      Background Since the beginning of the 21st century, the global extreme weather has become normal, leading to frequent landslides, debris flows and other disasters have become a new normal. With the global climate change, extreme rainstorm events occur frequently, leading to more landslides in mountainous areas. Rainstorm events lead to frequent landslides. Understanding the occurrence and distribution of rainfall-based landslides in small watersheds can provide a decision-making basis for soil erosion prevention, rational disaster prevention and mitigation, and an effective guarantee of people’s life and property safety.
      Methods Based on the daily precipitation data of the Fangta watershed in 2013 and 2020, the characteristics of rainfall inducing landslide in these two years were analyzed. Combined with remote sensing and geographic information system technologies, the distribution characteristics of rainfall-type landslides were obtained by interpreting high-resolution images before and after the landslides occurred in the past two years. Descriptive statistics were used to study the response of different rainfall characteristics and underbed to the number and scale of landslides, and the characteristics of landslide recurrence were discussed.
      Results 1) The main rainfall processes that induced landslides in 2013 were characterized by large accumulative rainfall, long rainfall duration, heavy rainfall frequency, and short interval. In 2020, there were more rainfall events but low rainfall intensity and few rainstorm times but more rainstorms amount in a single day. 2) The landslides that occurred in these two years were mainly small shallow landslides. The landslide scale in 2013 was large, and that in 2020 was small. The landslide erosion modulus in the two years was 6428.24 t/km2 and 4197.40 t/km2. 3) The slope with gradient of ≥30°-50° and the elevation interval of 1100-1 250 m are highly sensitive areas of landslides. There are more landslides in the forest and shrub areas, and the closer the distance to the road, the greater the possibility of landslides. 4) 21.9% of the landslides in the basin had a recurrence, some of them had multiple small-scale recurrences and nearly 90% of them had reduced recurrence area.
      Conclusions The heavier and longer the rainfall, the more likely it is to cause landslides, and the steeper the slope and the more frequent the human activity in the area, the greater the likelihood of landslides. This study may provide a valuable reference basis for landslide erosion disasters caused by heavy rain in small watershed in the hilly-gully region of the Loess Plateau.

       

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