Debris flow hazard assessment of the Eryang River watershed based on numerical simulation
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摘要:
洮河流域中游位于甘肃省南部，属泥石流高发区。耳阳河是洮河流域中游的一条重要支流，泥石流灾害尤其严重。为研究甘肃省南部小流域泥石流灾害的危险性，以耳阳河流域为研究对象，选取流域内居民相对集中的6条泥石流沟，用FLO-2D模型模拟了2012年5月10日实际降雨条件下的泥石流运动特征和堆积特征，得到了泥石流流量随时间的变化曲线、泥石流流体深度和流速在沟谷不同地段的空间分布，对“5·10”泥石流灾害过程进行了重现。模拟结果表明：泥石流爆发15～30 min后达到洪峰，约3 h后流量逐步回落；泥石流流动速度在流通区快，到沟口迅速下降，固体物质淤积阻塞河道。通过野外现场调查和遥感解译，发现模拟得到的泥石流发生过程、堆积区分布、泥石流影响区与现场调查和访问得到的实际情况基本相符。进而，采用相同的方法和参数，对2.0%和0.2%降水频率下泥石流的堆积范围、深度和流速进行了模拟分析，分别制作了上述工况下的泥石流危险性分区图，圈定了潜在威胁较大的人口聚集区，为耳阳河流域泥石流灾害的预防和治理提供了依据，也为类似泥石流提供了一种危险性分析的技术方法。
Abstract:The middle reach of the Taohe River in the southern part of Gansu Province is severely threatened by debris flow hazard. The Eryang River is an important branch of the Taohe River. On May 10, 2012, a large amount of debris flows was triggered by extreme heavy rainfall (with 1% frequency), resulting in serious losses of human life and property in Minxian County of Gansu Province. In order to recognize the hazard of debris flow in small watersheds, six key debris flow gullies in the Eryang watershed were selected as the research areas. The numerical simulation software FLO-2D was used to simulate the debris flow movement and accumulation characteristics of each debris flow gully under the actual “5·10” rainfall conditions, so as to reconstruct the "5·10" debris flow disaster scenario. Numerical simulation results show that the flow speed increased to the maximum after 15～30 minutes since the outburst. The flow lasted for about 3 hours. The speed in the moving section was very high, and decreased sharply at the gully-mouth, deposits accumulated in the river valley. According to the remote sensing and field investigation, the simulation results were compared with the actual situation. The comparison shows the simulation effect is good, and the deposition area, the discharge process, and the main damage area are well reconstructed by FLO-2D simulation. The same method and parameters are used to simulate the accumulation range, depth and velocity of debris flow under the precipitation of 2.0% and 0.2% frequencies, and the risk zoning map is produced by the simulation data. The potentially threatened houses and properties are also outlined. These provide references to the local government to control the debris risk. This work also provides a practical approach for the debris flow hazard assessment.
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Key words:
- Taohe watershed /
- Eryang river /
- debris flow /
- FLO-2D /
- hazard assessment
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表 1 泥石流沟特征参数
Table 1. Property list of the key debris flow gullies
泥石流沟名称 流域面积/km2 主沟长度/km 纵比降/‰ 相对高差/m 拉龙沟 1.47 1.31 205.9 350 扎龙沟 1.36 1.66 217.4 400 义子沟 2.12 2.48 189.7 550 接哈沟 2.47 1.67 250.0 650 拉路沟 0.90 1.19 316.9 450 牌嘴沟 0.54 1.31 246.0 400 
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表 2 模拟结果与调查结果对比表
Table 2. Comparison of the simulation and survey results
沟名 堆积扇范围/m2 堆积扇均厚/m 调查值 模拟值 误差率/% 调查值 模拟值 误差率/% 拉龙沟 3968 11500 189.8 1.50 1.12 −25.3 扎龙沟 9826 11600 18.1 1.60 1.31 −18.1 拉路沟 731 21400 2827.5 1.10 0.31 −71.8 牌嘴沟 9218 10500 13.9 0.58 0.57 −1.7 义子沟 15956 20500 28.5 0.60 0.74 23.3 接哈沟 21971 20600 −6.2 1.60 1.48 −7.5
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表 3 泥石流危险性分区指标
Table 3. Risk classification of debris flow
危险性 堆积深度/m 逻辑关系 堆积深度和流速的乘积 高 h≥1.5 OR vh≥1.5 中 0.5<h<1.5 AND 0.5<vh<1.5 低 0.01≤h≤0.5 AND 0.1≤vh≤0.5
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表 4 泥石流危险性分区统计表
Table 4. Statistics of debris flow hazard zoning
沟名 占总危险面积比例/% 高危险 中危险 低危险 拉龙沟 13.89 70.83 15.28 扎龙沟 38.60 35.09 26.32 拉路沟 16.36 54.55 29.09 牌嘴沟 2.20 71.43 26.37 义子沟 15.03 58.55 26.42 接哈沟 34.23 47.75 18.02
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表 5 不同频率的降雨参数
Table 5. Rainfall amounts of different frequencies
暴雨历时 频率及小时降水量/mm 2.0% 1.0% 0.2% 1 h 33.2 42.0 49.3 6 h 48.2 52.9 64.4
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表 6 2.0%和0.2%降雨频率条件下泥石流堆积区危险性分区统计表
Table 6. Statistics of hazard zoning of debris flow accumulation area in 2.0% and 0.2% rainfall frequencies
沟名 高危险区 中危险区 低危险区 面积/m2 占总面积的比例/% 面积/m2 占总面积的比例/% 面积/m2 占总面积的比例/% 2.0%降雨概率 拉龙沟 100 1.64 3 400 55.74 2 600 42.62 扎龙沟 600 13. 95 2 300 53.49 1 400 32.56 拉路沟 0 0 2 400 58.54 1 700 41.46 牌嘴沟 0 0 1 500 27.78 3 900 72.22 义子沟 0 0 4 800 50.53 4 700 49.47 接哈沟 600 7.06 5 300 62.35 2 600 30.59 0.2%降雨概率 拉龙沟 2 000 23.26 5 800 67.44 800 9.30 扎龙沟 2 400 35.82 3 200 47.76 1 100 16.42 拉路沟 1 100 18.64 3 600 61.02 1 200 20.34 牌嘴沟 0 0 4 800 57.83 3 500 42.17 义子沟 2 500 12.82 13 100 67.18 3 900 20.00 接哈沟 4 000 34.78 5 700 49.57 1 800 15.65
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