Regional geological hazard risk assessment based on slope unit and AHP-evidence weight coupling model
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摘要:
危险性评价是我国西南山区防灾减灾的重要手段,目前大部分评价体系采用的评价模型层次浅显且指标单一,针对该问题,提出层次分析法(analytic hierarchy process,AHP)-证据权耦合模型,对马尔康地质灾害危险性展开评价研究。结合ArcGIS水文分析和人机交互实现了斜坡单元划分的优化,将研究区划分为5 695个斜坡单元,选取了年均降雨量、地层岩性、坡度、坡向、距水系距离、距断层距离、距道路距离、斜坡高差8个指标因子,采用AHP-证据权耦合模型分别求解指标因子权重值及下属区间对地质灾害事件的贡献度,得到研究区地质灾害危险性分区图。结果表明,高危险区和极高危险区分别占研究区总面积的14.96%和8.46%,主要集中在水系两侧的居民聚集区,受试者工作特征曲线(receiver operating characteristic curve,ROC)曲线下面积(area under the curve of the receiver operating characteristic,AUC)为0.78,模型整体预测精度较好。研究成果可为区域地质灾害的危险性评价提供参考,对于西南山区地质灾害排查的前期工作开展具有指导意义。
Abstract:Risk assessment is an important means of disaster prevention and mitigation in mountainous areas in the southwestern China. However, most current evaluation systems use models of shallow level and with single indicator. To address this problem, the authors in this paper proposed the AHP-evidence weight coupling model to conduct risk issessment of geological hazard in Maerkang. ArcGIS hydrological analysis and human-computer interaction were combined to optimize the division of slope units. The study area was divided into 5 695 slope units, and 8 index factors were selected, including rainfall, stratigraphic lithology, slope gradient, slope aspect, distance from water system, distance from fault, and distance from road. AHP-evidence weight coupling model was used to respectively solve the index factor weight value and the contribution of the subordinate intervals to geological hazard events, and the geological hazard risk zoning map of the study area was obtained. The results show that high-risk areas and extremely high-risk areas account for 14.96% and 8.46% of the total area respectively, and these areas are mainly concentrated in residential areas on both sides of the water system. The AUC is 0.78, and the model evaluation accuracy is good. The research results could provide references for the risk assessment of regional geological hazards and have guiding significance for the preliminary work of geological hazard investigation in the southwestern mountainous areas.
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表 1 数据来源信息
Table 1. Data source information
数据类型 数据源 时间 分辨率/m 既有地质灾害 四川省地质灾害信息系统 截至2023年2月 - 数字高程模型 SRTM DEM - 30 年均降雨量 中科院山地所 1991—2020年 30 地层岩性 四川省地质调查院 2008年 1∶25万 光学遥感影像 天地图 2023年 1.2 InSAR形变监测 自然资源部门 2023年 - 注: “-”代表该项内容不存在或未知。 表 2 研究区地质灾害分布统计
Table 2. Geological disaster distribution statistics table
乡镇名称 乡镇面积/km2 灾害数量/处 灾害点密度(10-2处·km-2) 滑坡 崩塌 泥石流 白湾乡 261.7 1 1 0 0.76 脚木足乡 450.7 4 1 8 2.88 康山乡 632.2 4 2 13 3.01 梭磨乡 1108.9 5 2 20 2.43 木尔宗乡 222.7 8 3 5 7.18 松岗镇 245.59 11 2 17 12.22 大藏乡 408.0 9 3 11 5.64 沙尔宗镇 387.3 12 4 12 7.23 日部乡 978.3 14 3 12 2.96 党坝乡 328.3 12 1 4 5.18 龙尔甲乡 345.4 26 3 9 11.00 马尔康镇 673.8 30 10 22 9.20 草登乡 589.8 22 8 31 10.34 合计 6 632.7 158 43 164 5.50 表 3 指标因子重要性判断标度
Table 3. Index factor importance judgment scale
判断标度 含义 1 表示两个因子a与b相比,它们的重要性相同 3 表示两个因子a与b相比,a比b稍微重要 5 表示两个因子a与b相比,a比b比较重要 7 表示两个因子a与b相比,a比b明显重要 9 表示两个因子a与b相比,a比b非常重要 2、4、6、8 表示上述相邻判断的中间值 倒数 若因子a与b的重要性之比为j,那么因子b与a的重要性之比为1/j 注: a、b表示指标因子; j表示判断标度。 表 4 随机一致性指标(RI)数值
Table 4. Random consistency index (RI) value
n 1 2 3 4 5 6 RI 0 0 0.58 0.9 1.12 1.24 n 7 8 9 10 11 RI 1.32 1.41 1.45 1.49 1.51 注: n表示指标因子数量。 表 5 研究区各指标因子分级
Table 5. Index factor grading in the study area
指标因子 分级数量 分级标准 地形条件 坡度/(°) 8 [0°,5°]; (5°,10°]; (10°,15°]; (15°,20°]; (20°,25°]; (25°,30°]; (30°,35°]; (35°,90°] 坡向/(°) 8 北(337.5°,22.5°];
北东(22.5°,67.5°];
东(67.5°,112.5°];
南东(112.5°,157.5°];
南(157.5°,202.5°];
南西(202.5°,247.5°];
西(247.5°,292.5°];
北西(292.5°,337.5°]斜坡高差/m 7 [0, 200]; (200,400]; (400,600]; (600,800]; (800,1 000]; (1 000,1 200]; (1 200,1 400];>1 400 水文条件 年均降雨量/mm 5 [635,655]; (655,675]; (675,695]; (695,715]; >715 距水系距离/km 8 [0, 2]; (2,4]; (4,6]; (6,8]; (8,10]; (10,12]; (12,14]; >14 地震条件 距断层距离/km 8 [0, 3]; (3,6]; (6,9]; (9,12]; (12,15]; (15,18]; (18,21]; >21 地质条件 地层岩性 5 三叠纪似斑状二长花岗岩; 三叠纪花岗岩; 三叠纪花岗闪长岩; 上三叠统厚层状变砂岩板岩; 中—上三叠统变砂岩板岩夹灰岩 工程活动 距道路距离/km 8 [0, 1]; (1,2]; (2,3]; (3,4]; (4,5]; (5,6]; (6,7]; >7 表 6 研究区层次分析法判别矩阵
Table 6. AHP discriminant matrix in the study area
因子 X1 X2 X3 X4 X5 X6 X7 X8 X1 1 1/3 1 2 2 3 1/2 1/6 X2 3 1 3 3 2 5 3 1/4 X3 1 1/3 1 2 1/2 3 1/2 1/6 X4 1/2 1/3 1/2 1 1/3 2 1/4 1/8 X5 1/2 1/2 2 3 1 2 1/4 1/7 X6 1/3 1/5 1/3 1/2 1/2 1 1/5 1/9 X7 2 1/3 2 4 4 5 1 1/5 X8 6 4 6 8 7 9 5 1 注: X1表示斜坡高差; X2表示地层岩性; X3表示距道路距离; X4表示距水系距离; X5表示距断层距离; X6表示坡向; X7表示坡度; X8表示年均降雨量。 表 7 研究区指标因子权重
Table 7. Index factor weight value in the study area
因子 X1 X2 X3 X4 X5 X6 X7 X8 权重 0.07 0.14 0.06 0.04 0.10 0.03 0.14 0.42 注: X1表示斜坡高差; X2表示地层岩性; X3表示距道路距离; X4表示距水系距离; X5表示距断层距离; X6表示坡向; X7表示坡度; X8表示年均降雨量。 表 8 研究区各指标因子下属层级贡献度
Table 8. Contribution of the subordinate levels of each index factor in the study area
因子 证据层 Ci值 证据层 Ci值 坡度/(°) [0°,5°] - (20°,25°] 0.14 (5°,10°] 1.10 (25°,30°] -0.17 (10°,15°] 3.09 (30°,35°] -0.71 (15°,20°] 2.17 (35°,90°] -1.28 坡向 北 -0.83 南 0.24 北东 0.24 南西 0.23 东 0.30 西 -0.15 南东 -0.02 北西 -0.79 斜坡高差/m [0, 200] 2.68 (800,1 000] -1.17 (200,400] 0.31 (1 000,1 200] -2.34 (400,600] -0.23 (1 200,1 400] -3.45 (600,800] -0.92 >1 400 -4.18 年均降雨量/mm [635,655] 0.70 (695,715] -0.49 (655,675] 1.04 >715 -2.41 (675,695] 0.57 - - 距水系距离/km [0, 2] 0.62 (8,10] -1.67 (2,4] -0.09 (10, 12] -1.99 (4,6] -0.35 (12, 14] -2.34 (6,8] -0.47 >14 -2.87 距断层距离/km [0, 3] 0.49 (12,15] -0.64 (3,6] -0.41 (15,18] -0.16 (6,9] 0.31 (18,21] -2.09 (9,12] -0.12 >21 -0.61 地层岩性 三叠纪似斑状二长花岗岩 -1.39 三叠纪花岗岩 - 三叠纪花岗闪长岩 - 中—上三叠统变砂岩板岩夹灰岩 -0.38 上三叠统厚层状变砂岩板岩 0.7 - - 距道路距离/km [0, 1] 2.24 (4,5] -2.73 (1,2] -1.64 (5, 6] -2.84 (2,3] -1.16 (6, 7] -3.02 (3,4] -2.51 >7 -3.61 注: “-”表示灾害不发育。 表 9 研究区各危险区划频率比
Table 9. Frequency ratio for each danger zone in the study area
危险区划 滑坡占比/% 面积占比/% 频率比 极低危险区 1.36 46.55 0.03 低危险区 3.52 8.09 0.44 中危险区 18.97 21.94 0.86 高危险区 24.12 14.96 1.61 极高危险区 52.03 8.46 6.15 -
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