基于频率比—层次分析法的金沙江巧家段滑坡灾害易发性评价

Evaluation of Landslide Susceptibility in Qiaojia Section of the Jinsha River Based on Frequency Ratio and AHP Model

滑坡灾害经常会造成重大的经济损失,并威胁生命安全,特别是地势高陡的地区,滑坡灾害的威胁更为严重。金沙江流域地势高陡,构造活跃,加上人类工程活动的影响,地质灾害非常发育。基于野外调查以及遥感解译,获取了金沙江巧家段流域的3573个滑坡灾害的空间分布,并基于层次分析法与频率比法相结合的方法,建立了金沙江巧家段滑坡的易发性评估模型。首先以高程、地形起伏度、坡度、坡向、土壤、土地利用类型、岩性、多年平均降雨量、地面峰值加速度(PGA)等因子作为触发因素,确定相应的滑坡相对频率(mLRF)。然后采用层次分析法确定各滑坡影响因子的相对权重,并对权重分配进行一致性检验。再根据权重将各影响因子的图层进行叠加计算,得到金沙江巧家段的滑坡灾害易发性评价图,结果表明:研究区60%以上属于中低易发性,约12%为高易发性区域,并多位于河谷两侧。最后,利用相等面积的滑坡和非滑坡像元,通过统计ROC曲线的线下面积(AUC)检验模型的准确性,结果为0.827,说明该模型是可靠的。由此,可以根据研究区的易发程度而采取相应的防灾减灾规划措施,以减轻该地区的滑坡风险。

Landslide hazards often cause significant economic losses and threaten life safety.In the mountain areas,landslide disaster is more serious.The Jinsha River area is often threatened by serious geological disasters,especially landslides,because of high and steep terrain,intense tectonic activity and the influence of human engineering activities.Based on field investigation and remote sensing images,a landslide inventory is built,including 3573 landslides in the Qiaojia section of the Jinsha River.And the frequency ratio method and the analytic hierarchy process are combined to form the new method of the landslide susceptibility evaluation.Firstly,the trigger factors such as elevation,topographic relief,slope,aspect,soil,land use type,lithology,annual average rainfall,peak ground acceleration(PGA)are used to determine the corresponding landslide relative frequency(mLRF).Then,the relative weight of each impact factor is determined by the analytic hierarchy process,and made consistency examination.By calculating the layers of each influence factor based on the weight values,an evaluation map of landslide susceptibility in the Qiaojia section of the Jinsha River can be obtained.The results show that over 60%of the study area belongs to medium to low susceptibility,and about 12%is high susceptibility,mostly located on both sides of the river.Finally,landslide and non landslide pixels of equal area are selected,and the accuracy of the model is examined by calculating the offline area(AUC)of the ROC curve.The AUC result is 0.827,indicating that the model is reliable.Therefore,it is necessary to adopt different disaster prevention and reduction planning measures based on the susceptibility map to reduce the landslide risk.