多因子组合的地质灾害易发性空间精度验证

Evaluation on spatial accuracy and validation of geological hazard susceptibility based on a multi-factor combination

地质灾害的发生是多种因素相互作用、制约和触发的结果。长期以来,研究人员通过统计历史地质灾害所在区域的地质、地形、水文等环境因素预测未来地质灾害可能发生的位置、时间(或频率),即地质灾害易发性评价。地质灾害易发性评价前提工作是进行影响因子选取,而地质灾害发生的影响因子有数十种,是否叠加因子越多模型评价精度就越高?是否存在“最优因子数量”?这一简单而又关键的问题值得探讨。文章以四川省汶川县为例,选取11种广泛应用于地质灾害易发性评价的影响因子,按照4种排列组合模型,叠加3到11个因子信息量获得对应的地质灾害易发性指数分布图。运用成功率曲线确定线下面积值对各个结果进行预测精度评价。试验结果表明,按照初步设定的4种排列组合模型叠加因子数量到8个时,模型预测精度达到最大值;但在因子叠加过程中发现各个因子对于易发性的控制性与个人经验确定的控制性存在一定差异,按照实际因子控制性从大到小与从小到大排列组合后,叠加多个关键因子后模型预测精度才会达到峰值。研究成果表明,地质灾害易发性评价中叠加的因子数量越多,模型预测精度越高,叠加过程中如未加入关键因子,模型预测精度将不会达到峰值,说明地质灾害易发性评价不存在“最优因子数量”。

The occurrence of geological hazards is the result of the interaction,constraints,and triggers of various factors.For a long time,researchers have predicted the potential locations and time(or frequency)of future geological hazards in areas prone to historical geological disasters based on environmental factors such as geology,topography,and hydrology,known as geological hazard susceptibility assessment.A prerequisite for geological hazard susceptibility assessment is the selection of impact factors,and there are dozens of factors contributing to the occurrence of geological hazards.Does the accuracy of assessment model increase with the addition of more factors?Is there an“optimal number of factors”?This simple yet crucial question is worth exploring.Taking Wenchuan County,Sichuan Province,as an example,this study selects 11 commonly used influencing factors in geological hazard susceptibility assessment and arranges them into four different combination,superimposing information from 3 to 11 factors to obtain corresponding distribution maps of geological hazard susceptibility indexes.The area under curve(AUC)value was used to evaluate the predictive accuracy of the results.Experimental results show that the prediction accuracy of the model reaches its maximum value when the number of superposition factors added to the model reaches 8 according to the preliminary set four combinations.However,during the process of factor superposition,it is found that there are certain difference between the control of susceptibility by each factor and the control determined by individual experience.When the actual factor control is arranged from largest to smallest or from smallest to largest,the predictive accuracy of the model reaches its peak value after superposition of multiple key factors.The research findings indicates that the more factors added to the geological hazard susceptibility assessment,the higher the predictive accuracy of the model.If key factors are not included during the superimposition process,the predictive accuracy of the model will not reach its peak,indicating that there is no“optimal number of factors”in geological hazard susceptibility assessment.