Susceptibility evaluation of debris flow in Bomi-Metuo area based on Pearson Chi-square test algorithm
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摘要: 西藏地区地貌单元复杂、地质构造活跃,为该地区泥石流提供了良好的孕育环境,也对人类生命财产构成了极大威胁,开展泥石流易发性评价可为地区防灾减灾明确重点区域。以西藏自治区波密县-墨脱县为研究区域,利用Pearson卡方检验算法优选出高程、坡度、地层岩性、降雨量等12个对泥石流影响较高的因素作为评价指标,以研究区282个泥石流点和非泥石流点为样本数据库,基于ArcGIS平台利用信息量法和机器学习方法建立了4种易发性评价模型,并引入ROC曲线和AUC指标对泥石流易发性精度进行评估。研究表明:(1)考虑不同维度泥石流类型和主控因素不同,采用纬度和气温相融合的归一化系数作泥石流易发性评价指标,在一定程度上消除了低海拔地区泥石流对温度的过度响应。(2)气温、距水系距离、距道路距离、地层岩性、高程是研究区泥石流发生的主控因素;植被覆盖率、地形湿度、坡度等因素也发挥着重要作用。(3)考虑泥石流灾害点和影响因子分级属性关系,对影响因子各分级属性赋分,作为输入特征进行训练,机器学习模型预测效果较好,平均AUC为0.980,整体优于传统的信息量模型。(4)SVM模型的AUC高达0.987,高易发区FR值为41.13且预测面积占比最小,具有在大尺度区域内进行高精度预测的能力。Abstract: The complex geomorphic units and active geological structures in Tibet provide a good breeding environment for debris flow in the region, but also pose a great threat to human life and property. The evaluation of debris flow susceptibility can identify key areas for disaster prevention and reduction in the region. Taking Bhumi County and Medog County of Tibet Autonomous Region as the study area, 12 factors with high influence on debris flow, including elevation, slope, stratigraphic lithology and rainfall, were selected by Pearson Chi-square test algorithm as evaluation indexes, and 282 debris flow points and non-debris flow points in the study area were taken as sample database. Based on ArcGIS platform, four susceptibility evaluation models were established by using information method and machine learning method, and ROC curve and AUC index were introduced to evaluate the susceptibility accuracy of debris flow. The results show that: (1) Considering the different types of debris flow in different dimensions and the different controlling factors, the normalization coefficient of latitude and air temperature is used as the evaluation index of debris flow susceptibility, which can eliminate the excessive response of debris flow to temperature in low altitude areas to a certain extent. (2) Air temperature, distance from water system, distance from road, formation lithology and elevation are the main factors of debris flow occurrence in the study area; Factors such as vegetation coverage, terrain humidity, and slope also play an important role. (3) Considering the relationship between the disaster point of debris flow and the classification attributes of the impact factors, the classification attributes of the impact factors were assigned scores and trained as input features. The prediction effect of the machine learning model was good, and the average AUC was 0.980, which was better than the traditional information model on the whole. (4) The AUC of SVM model is as high as 0.987, the FR value of the highly prone region is 41.13, and the prediction area of highly prone regions takes up the smallest proportion, so it has the ability to perform high-precision prediction in large-scale regions.
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