岷江上游潜在性泥石流堰塞湖危害及判识
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摘要
汶川地震造成泥石流形成条件的改变,其次生灾害堰塞湖的危害已开始显现。如何对震后潜在性泥石流堰塞湖进行判识,成为迫切需要解决的问题。选取岷江上游映秀至汶川段为研究区,通过分析震后泥石流形成条件的变化、典型泥石流堰塞湖的危害及松散物质储量,选取潜在性泥石流堰塞湖的判识指标,利用模糊物元可拓模型,建立潜在性泥石流堰塞湖的综合判识模式。通过判识,研究区形成泥石流堰塞湖可能性高的一级支沟有17条,主要集中分布在映秀镇至草坡乡段,此段将是今后受堰塞湖危害的高危地段。
The Wenchuan earthquake caused numerous landslides and collapses that provided abundant loose solid materials for future mobilization as debris flows.The formation conditions for debris flows were changed consequently.Debris flows will be very active for a long time in the affected area.Their secondary disaster,barrier lake,is beginning to appear.Therefore,it is urgent to identify those debris flow gullies which are potential to form barrier lakes following the environmental changes caused by the earthquake.This paper selected the upper Min River from Yinxiu to Wenchuan as study area,analyzed the changed formation conditions of debris flows and the damages of a typical debris flow barrier lake,and interpreted the loose solid materials from TM satellite images and aerial photographs.Then,the identification factors were selected and classified based on the factor independence analysis.At last,the fuzzy matter-element extension theory was used to construct a model to identify potential barrier lakes.The potential future increase in debris flow activity relates directly to the great increase in loose materials.The interpretation results indicated that the area of the landslides and collapses caused by the earthquake is 39.40 km2,accounting for 6.97% of the total study area.Assuming 55% of the landslide and collapse area were their deposition area and the average deposition depth was 10 m,the volume of the loose solid materials can be estimated as 2.13×108m3 which was sufficient for debris flow formation.Based on the factor independence analysis,the volume of the loose solid materials per unit area,the discharge ratio between the debris flow gully and the main river,the slope gradient of debris flow channel,the main river width,and the included angle between the debris flow gully and the main river were determined as identification factors.According to the multi-factor comprehensive identification,among the 55 first-grade gullies,17 gullies have high probabilities for potential debris flow barrier lakes,15 have moderate probabilities,and 23 gullies have low probabilities.The most likely debris flow gullies for forming barrier lakes mainly distribute in the middle-to-lower reaches of the study area(Yingxiu Town to Caopo Town),and those with moderate and low probabilities are mainly distributed in the upper reaches of the study area(Caopo Town to Wenchuan County).In addition,among the 17 potential debris flow gullies with high probabilities,4 gullies already yielded barrier lakes during the 2008-2010 rainy seasons.The remaining debris flow gullies will produce barrier lakes in the future with high probability.
The Wenchuan earthquake caused numerous landslides and collapses that provided abundant loose solid materials for future mobilization as debris flows.The formation conditions for debris flows were changed consequently.Debris flows will be very active for a long time in the affected area.Their secondary disaster,barrier lake,is beginning to appear.Therefore,it is urgent to identify those debris flow gullies which are potential to form barrier lakes following the environmental changes caused by the earthquake.This paper selected the upper Min River from Yinxiu to Wenchuan as study area,analyzed the changed formation conditions of debris flows and the damages of a typical debris flow barrier lake,and interpreted the loose solid materials from TM satellite images and aerial photographs.Then,the identification factors were selected and classified based on the factor independence analysis.At last,the fuzzy matter-element extension theory was used to construct a model to identify potential barrier lakes.The potential future increase in debris flow activity relates directly to the great increase in loose materials.The interpretation results indicated that the area of the landslides and collapses caused by the earthquake is 39.40 km2,accounting for 6.97% of the total study area.Assuming 55% of the landslide and collapse area were their deposition area and the average deposition depth was 10 m,the volume of the loose solid materials can be estimated as 2.13×108m3 which was sufficient for debris flow formation.Based on the factor independence analysis,the volume of the loose solid materials per unit area,the discharge ratio between the debris flow gully and the main river,the slope gradient of debris flow channel,the main river width,and the included angle between the debris flow gully and the main river were determined as identification factors.According to the multi-factor comprehensive identification,among the 55 first-grade gullies,17 gullies have high probabilities for potential debris flow barrier lakes,15 have moderate probabilities,and 23 gullies have low probabilities.The most likely debris flow gullies for forming barrier lakes mainly distribute in the middle-to-lower reaches of the study area(Yingxiu Town to Caopo Town),and those with moderate and low probabilities are mainly distributed in the upper reaches of the study area(Caopo Town to Wenchuan County).In addition,among the 17 potential debris flow gullies with high probabilities,4 gullies already yielded barrier lakes during the 2008-2010 rainy seasons.The remaining debris flow gullies will produce barrier lakes in the future with high probability.
引文
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[18]崔鹏,庄建琦,陈兴长,等.汶川地震区震后泥石流活动特征与防治对策[J].四川大学学报(工程科学版),2010,42(5):10~19.
[2]吴树仁,石菊松,姚鑫,等.四川汶川地震地质灾害活动强度分析评价[J].地质通报,2008,27(11):1900~1906.
[3]游勇,柳金峰.汶川8级地震对岷江上游泥石流灾害防治的影响[J].四川大学学报(工程科学版),2009,41(增刊):16~22.
[4]常晓军,丁俊,魏伦武,等.岷江上游地质灾害发育分布规律初探[J].沉积与特提斯地质,2007,27(1):103~108.
[5]柳金峰,游勇.汶川地震触发潜在性泥石流研究:以岷江上游关山沟为例[J].四川大学学报(工程科学版),2009,41(增刊):70~75.
[6]胡凯衡,游勇,庄建琦,等.北川地震重灾区泥石流特征与减灾对策[J].地理科学,2010,30(4):566~570.
[7]徐永年,匡尚富.泥石流入汇的危险性判别指标[J].自然灾害学报,2002,11(3):33~38.
[8]郭志学,曹叔尤,刘兴年,等.泥石流堵江影响因素试验研究[J].水利学报,2004,11:39~45.
[9]张金山,沈兴菊,谢洪.泥石流堵河影响因素研究:以岷江上游为例[J].灾害学,2007,22(2):82~86.
[10]周必凡,李德基,罗德富,等.泥石流防治指南[M].北京:科学出版社,1991.
[11]游勇,柳金峰,陈兴长“.5.12”汶川地震后北川苏保河流域泥石流危害及特征[J].山地学报,2010,28(3):358~366.
[12]刘希林,陈宜娟.泥石流风险区划方法及其应用——以四川西部地区为例[J].地理科学,2010,30(4):558~565.
[13]郝航程,朱方海.基于可拓学理论的边坡潜在破坏模式识别方法[J].地下空间与工程学报,2007,3(4):698~702.
[14]付静,刘国东,张贞,等.模糊物元模型在土壤侵蚀等级划分中的应用[J].水土保持通报,2008,28(3):138~140.
[15]黄辉玲,吴次芳.基于可拓学的生态市建设评价——以哈尔滨市为例[J].地理科学,2009,29(5):651~657.
[16]李如忠,汪明武,金菊良.地下水环境风险的模糊多指标分析方法[J].地理科学,2010,30(2):229~235.
[17]徐辉,陈又星.模糊聚类模型及其在国际市场划分中的应用研究[J].地理科学,2010,30(3):350~354.
[18]崔鹏,庄建琦,陈兴长,等.汶川地震区震后泥石流活动特征与防治对策[J].四川大学学报(工程科学版),2010,42(5):10~19.
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