Vol18 No.4: 932-951
【Title】Activity evolution of landslides and debris flows after the Wenchuan earthquake in the Qipan catchment, Southwest China
【Author】SHI Qing-yun1, TANG Chuan1*, GONG Ling-feng2, CHEN Ming1, LI Ning3, ZHOU Wei1, XIONG Jiang1, TANG Hai4, WANG Xiao-di5, LI Ming-wei1
【Addresses】1 State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China; 2 Chengdu Geological Survey Center, China Geological Survey, Chengdu 610081, China; 3 School of Emergency Science, Xihua University, Chengdu 610039, China; 4 11th Geology Team of Zhejiang Province, Wenzhou 32500, China; 5 Sichuan Academy of Environmental Sciences, Chengdu 610044, China
【Corresponding author】TANG Chuan
【Citation】Shi QY, Tang C, Gong LF, et al. (2021) Activity evolution of landslides and debris flows after the Wenchuan earthquake in the Qipan catchment, Southwest China. Journal of Mountain Science 18(4). https://doi.org/10.1007/s11629-020-6494-4
【Abstract】The Wenchuan earthquake that occurred on 12 May 2008 induced numerous landslides. Loose landslide materials were deposited on hillslopes, and deep channels were easily remobilized and transformed into debris flows by extreme rainstorms. Twelve years after the Wenchuan earthquake, debris flows were still active in the Qipangou Ravinein the quake-hit area. In this paper, we continuously tracked the spatiotemporal evolution ofthelandslides and vegetation restoration and evaluated the evolution of debris flow activity in the Qipan catchment with the aid of a GIS platform and field investigationsfrom 2008 to 2019. We observed that the area withactive landslides increased sharply immediately following the earthquake, and then decreased with time; however, the total area of landslides continued to increase from 6.93 km2 in 2008 to 10.55 km2 in 2019. The active landslides shifted towards lower angles and higher elevations after 2013.Since 2009, the vegetation coverage has been gradually increasing and approaching the coverage present before the earthquake as of 2019. The landslide activity was high and the vegetation recovery rates were rapidly rising during the first five years after the earthquake; the recovery rates then slowed over time. Therefore, we divided the evolution that occurred during the post landslide period into an active period (2008-2013), a self-adjustment period (2013-2026) and a stable period (after 2026). We then proposed a quantitative model to determine the trends of landslide activity rates and NDVI values in the catchment, which indicated that the landslide activities and postseismic vegetation restoration rates in this catchment will return to preseismic levels within approximately two decades.We also analysed the runout volumes of the debris flows after the earthquakes (Diexi and Wenchuan) and the standard deviation of the vegetation coverage and predicted that the debris flow activities will last for an additional 50 years or more.
【Keywords】Evolution of debris flow activity; Seismic landslides; Vegetation recovery; Qipan catchment