汶川地震滑坡与强降雨驱动的输沙量增加研究——以岷江上游为例
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摘要
为了能够详细刻画汶川地震及其震后强降雨对岷江上游输沙量增加量的影响,在对SPOT图像、航片和数字高程图的影像资料进行解译的基础上,对岷江上游滑坡、泥石流进行了标定,同时通过收集该流域1980-2010年期间输沙量、降雨量、滑坡量、泥石流量等方面的资料,分析了汶川地震前后岷江上游降水量、输沙量、滑坡量、泥石流量之间的相关关系,定量计算了汶川地震前后该流域输沙量的变化,进一步探析了汶川地震后强降雨驱动的滑坡、泥石流对岷江输沙量增加的控制作用。研究结果表明:1)由汶川地震的同震构造抬升和同震滑坡、泥石流所导致的输沙量增加值为30%左右,表明在汶川地震后岷江上游输沙量的增加主要受同震滑坡、泥石流的控制;2)震后强降雨导致的输沙量是震前的1.75倍,震后强降雨泥石流的产砂量对当年新增输沙量的贡献率达到37.49%;3)强降雨带与地震断裂带和地震滑坡带基本重合,导致了汶川地震后输沙量的增加与强降雨量之间存在正反馈关系;4)汶川地震震动所引发地表物质松动和驱动滑坡导致了河流输沙量加大,这是未来几十年所面临的灾害。
In order to characterize the increase of the sediment discharge caused by the Wenchuan earthquake and post-seismic heavy rainfall in the upper Min River,the SPOT images,aerial photographs and digital elevation map were interpreted,and landslides,mudslides in the area were marked. Data on sediment discharge,rainfall,landslides,and debris flows were collected for the period of 1980—2010 to describe the effects of the Wenchuan earthquake and post-earthquake heavy rainfall on the increase in sediment discharge of the area. The relationship among precipitation,sediment discharge,landslides,and debris flows before and after the Wenchuan earthquake was analyzed. The variation trends of sediment discharge in the river basin before and after the earthquake were calculated quantitatively. The research results showed that sediment discharge increased by approximately 30% due to coseismic uplift,coseismic landslides,and debris flows after the Wenchuan earthquake. The sediment discharge caused by heavy rainfall after the earthquake was 1. 75 times larger than that before the earthquake. The percentage contribution of the sediment yield of debris flows induced by heavy rainfall after the earthquake to the increase in sediment discharge was 37. 49%. The heavy rainfall zone basically coincided with the earthquake fault zone and the seismic landslide zone. Therefore,there was a positive-feedback relationship between the increase of sediment discharge and heavy rainfall after the Wenchuan earthquake. The loosening of surface materials and landslides driven by the Wenchuan earthquake resulted in an increase in sediment discharge into the river,bringing about a great disaster which will need to be addressed in the coming decades.
In order to characterize the increase of the sediment discharge caused by the Wenchuan earthquake and post-seismic heavy rainfall in the upper Min River,the SPOT images,aerial photographs and digital elevation map were interpreted,and landslides,mudslides in the area were marked. Data on sediment discharge,rainfall,landslides,and debris flows were collected for the period of 1980—2010 to describe the effects of the Wenchuan earthquake and post-earthquake heavy rainfall on the increase in sediment discharge of the area. The relationship among precipitation,sediment discharge,landslides,and debris flows before and after the Wenchuan earthquake was analyzed. The variation trends of sediment discharge in the river basin before and after the earthquake were calculated quantitatively. The research results showed that sediment discharge increased by approximately 30% due to coseismic uplift,coseismic landslides,and debris flows after the Wenchuan earthquake. The sediment discharge caused by heavy rainfall after the earthquake was 1. 75 times larger than that before the earthquake. The percentage contribution of the sediment yield of debris flows induced by heavy rainfall after the earthquake to the increase in sediment discharge was 37. 49%. The heavy rainfall zone basically coincided with the earthquake fault zone and the seismic landslide zone. Therefore,there was a positive-feedback relationship between the increase of sediment discharge and heavy rainfall after the Wenchuan earthquake. The loosening of surface materials and landslides driven by the Wenchuan earthquake resulted in an increase in sediment discharge into the river,bringing about a great disaster which will need to be addressed in the coming decades.
引文
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[2]Huang R Q,Fan X M.The landside story[J].Nature Geoscience,2013,6(5):325-326.
[3]Li Yong,Huang Runqiu,Zhou Rongjun,et al.The Ms8.0Wenchuan earthquake and co-seismic river response[J].Journal of Sichuan University:Engineering Science Edition,2010,42(5):20-33.[李勇,黄润秋,周荣军,等.汶川Ms8.0级地震的水系响应[J].四川大学学报:工程科学版,2010,42(5):20-33.]
[4]Korup O,Densmore A L,Schlunegger F.The role of landslides in mountain range evolution[J].Geomorphology,2010,120(1/2):77-90.
[5]Dadson S J,Hovius N,Chen H,et al.Earthquake-triggered increase in sediment delivery from an active mountain belt[J].Geology,2004,32:733-736.
[6]Cao Shuyou,Liu Xingnian,Huang Er.Advances in studies of river sediment and fluvial processes of the Upper-Yangtze river in earthquake background[J].Journal of Sichuan University:Engineering Science Edition,2009,41(3):26-33.[曹叔尤,刘兴年,黄尔.地震背景下的川江流域泥沙与河床演变问题研究进展[J].四川大学学报:工程地质学,2009,41(3):26-33.]
[7]Lin G W,Chen H,Niels H,et al.Effects of earthquake and cyclone sequencing on landsliding and fluvial sediment transfer in a mountain catchment[J].Earth Surface Processes and Landforms,2008,33(9):1354-1373.
[8]Lin C W,Shieh C,Yuan B,et al.Impact of Chi-Chi earthquake on the occurrence of landslides and debris flows:example from the Chenyulan River watershed,Nantou,Taiwan[J].Engineering Geology,2004,71(1/2):49-61.
[9]Lin C W,Liu S,Lee S,et al.Impacts on the Chi-Chi earthquake on subsequent rainfall-induced landslides in central Taiwan[J].Engineering Geology,2006,86(2/3):87-101.
[10]Koi T,Hotta N,Ishigaki I,et al.Prolonged impact of earthquake-induced landslides on sediment yield in a mountain watershed:The Tanzawa region,Japan[J].Geomorphology,2008,101(4):692-702.
[11]Tang Chuan,Li Weile,Ding Jun,et al.Field investigation and research on giant debris flow on AUGUST 14,2010in Yingxiu town,epicenter of Wenchuan earthquake[J].Earth Science—Journal of China University of Geosciences,2011,36(1):172-180.[唐川,李为乐,丁军,等.汶川震区映秀镇“8·14”特大泥石流灾害调查[J].地球科学——中国地质大学学报,2011,36(1):172-180.]
[12]Chu Shengming,Yu Bin,Li Li,et al.Forming mechanism and characteristics of debris flow happened on August13,2010 in Jianping Gully[J].Soil and Water Conservation in China,2011(8):52-54.[褚胜名,余斌,李丽,等.“8·13”碱坪沟泥石流形成机理及特征研究[J].中国水土保持,2011(8):52-54.]
[13]Ma Yu,Yu Bin,Wu Yufu,et al.Research on the disaster of debris flow of Bayi Gully,Longchi,Dujiangyan,Sichuan on August13,2010[J].Journal of Sichuan University:Engineering Science Edition,2011,43(1):92-98.[马煜,余斌,吴雨夫,等.四川都江堰龙池“八一沟”大型泥石流灾害研究[J].四川大学学报:工程科学版,2011,43(1):92-98.]
[14]Zhou Zhidong,Huang Qiang,Deng Ting.Study on development mechanism of debris flow in Hongchungou[J].Water Resources and Hydropower Engineering,2011,42(9):55-58.[周志东,黄强,邓婷.四川红椿沟泥石流成因初步分析[J].水利水电技术,2011,42(9):55-58.]
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