Risk assessment of mass debris flow based on numerical simulation: An example from the Malu River basin in Min County
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摘要:
岷县是甘肃南部泥石流频发地区。岷县泥石流多分布于洮河干支流两岸，为群发性泥石流。为了研究群发性泥石流的运动及堆积特征，选取了甘肃岷县麻路河流域为研究区域，以流域内2012年“5·10”暴发泥石流造成重大损失的6条泥石流沟作为整体研究对象，并考虑主河对泥石流堆积物的冲刷携带，运用FLO-2D模拟降雨前主河流动情况及不同降雨频率条件下主河及泥石流的流动情况。根据野外调查结果对比2%降雨频率条件下泥石流模拟结果，验证模型的可靠性。基于模拟结果用ArcGIS进行危险性评价，识别流域内高危险泥石流沟并划定高危险居民区，统计受冲击范围，为泥石流防治和预警工作提供科学依据。
Abstract:Min County is an area with frequent debris flow in the south part of Gansu Province. In order to study the movement and accumulation characteristics of debris flow, the Malu River basin in Min County, Gansu Province, which was affected by serious debris flow on May 10, 2012, is selected as the research area. Six debris flow gullies in the basin are taken as the research object, which are taken as a whole. Considering the main river's scouring and carrying of debris flow deposits, FLO-2D is used to simulate the flow situation and different rainfall frequency of the main river before rainfall. According to the field investigation results, the debris flow simulation results under the condition of 2% rainfall frequency are compared to verify the accuracy of the model. Based on the simulation results, ArcGIS is used to carry out the risk assessment, identify the high-risk debris flow gully in the basin, delimit the high-risk residential area, and make statistics of the impacted area, so as to provide scientific basis for debris flow prevention and early warning.
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Key words:
- Malu River basin /
- mass debris flow /
- risk assessment /
- FLO-2D /
- ArcGIS
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表 1 泥石流沟特征参数表
Table 1. Characteristic parameters of debris flow gullies
沟名 汇水面积/km2 纵比降/（‰） 主沟长度/km 相对高差/m 杨家沟 3.26 207 3.09 640 叶家沟 4.04 169 2.83 480 张家沟 7.19 209 3.3 690 大湾沟 1.83 366 1.01 370 峡里沟 3.98 213 2.29 490 拉路沟 2.75 174 2.01 350 
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表 2 麻路河流域泥石流沟松散物质量（单位：104 m3）
Table 2. Volume of loose material in debris flow gullies of Malu River basin (unit: 104 m3)
沟名 松散物质体积量 坡面耕地 崩塌滑坡 沟道淤积 人工弃渣 杨家沟 19.87 4.59 3.90 0.19 叶家沟 35.20 4.19 2.10 0 张家沟 52.12 5.76 4.80 0 大湾沟 15.97 2.35 1.29 0 峡里沟 8.21 5.53 3.45 1.72 拉路沟 15.58 1.55 1.80 0
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表 3 层流阻滞系数表
Table 3. Laminar retardation coefficient
地面条件 K值范围 混凝土/沥青 24～108 裸露沙土 30～120 级配土 90～400 被侵蚀的粘性土 100～500 稀疏植被 1 000～4 000 矮草原 3 000～10 000 早熟禾属植物草地 7 000～50 000
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表 4 不同频率的降雨参数（单位：mm）
Table 4. Rainfall parameters at different frequencies（unit: mm）
暴雨历时 设计频率 1% 2% 5% H1p 42.0 33.2 28.4 H6p 52.9 48.2 42.2
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表 5 模拟-调查误差率表
Table 5. Simulation & survey comparison table
沟名 堆积扇范围/m2 堆积扇均厚/m 调查值 模拟值 误差比率 调查值 模拟值 误差比率 杨家沟 42 469.19 45 200 6.43% 0.30 0.239 −20.33% 叶家沟 79 884.45 81 600 2.15% 0.46 0.406 −11.74% 张家沟 50 921.10 56 800 11.55% 0.71 0.509 −28.31% 大湾沟 26 773.79 31 600 18.03% 0.25 0.210 −16.00% 峡里沟 29 760.92 40 400 35.75% 2.20 0.706 −67.91% 拉路沟
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表 6 数值模拟精度表
Table 6. Numerical simulation accuracy table
沟名 堆积扇范围/m2 Ac 调查值 模拟值 重叠值 杨家沟 42 469.19 45 200 36 800 0.71 叶家沟 79 884.45 81 600 72 000 0.80 张家沟 50 921.10 56 800 46 800 0.76 大湾沟 26 773.79 31 600 25 600 0.77 峡里沟 29 760.92 40 400 27 600 0.63 拉路沟
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表 7 泥石流危险性分区指标
Table 7. Risk classification of debris flow
危险性 堆积深度/m 逻辑关系 堆积深度流速乘积 高 H>1.5 or VH>1.5 中 0.5<H≤1.5 and 0.5<VH≤1.5 底 0.1<H≤0.5 and 0.1<VH≤0.5
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表 8 1%、2%、5%降雨频率条件下泥石流堆积区危险性分区统计表
Table 8. Statistical table of hazard zoning of debris flow accumulation area in 1%、2%、5% rainfall frequency
降雨频率 沟名 高危险面积/m2 占总面积比例 中危险面积/m2 占总面积比例 低危险面积/m2 占总面积比例 P=1% 杨家沟 6 800 30.36% 10 800 48.21% 4 800 21.43% 叶家沟 12 400 36.47% 17 600 51.76% 4 000 11.76% 张家沟 18 800 68.12% 6 400 23.19% 2 400 8.70% 大湾沟 4 400 34.38% 6 400 50.00% 2 000 15.63% 峡里沟 20 400 69.86% 6 400 21.92% 2 400 8.22% 拉路沟 P=2% 杨家沟 5 600 25.93% 10 000 46.30% 6 000 27.78% 叶家沟 8 800 31.43% 14 800 52.86% 4 400 15.71% 张家沟 16 400 62.12% 7 200 27.27% 2 800 10.61% 大湾沟 3 600 29.03% 6 400 51.61% 2 400 19.35% 峡里沟 17 200 64.18% 7 200 26.87% 2 400 8.96% 拉路沟 P=5% 杨家沟 4 800 24.00% 9 200 46.00% 6 000 30.00% 叶家沟 7 200 26.87% 14 400 53.73% 5 200 19.40% 张家沟 11 600 45.31% 10 800 42.19% 3 200 12.50% 大湾沟 2 400 20.69% 6 400 55.17% 2 800 24.14% 峡里沟 15 600 62.90% 6 800 27.42% 2 400 9.68% 拉路沟
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