基于数值模拟的耳阳河流域泥石流灾害危险性评价

Debris flow hazard assessment of the Eryang River watershed based on numerical simulation

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。

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.