基于RAMMS数值模拟的短时强降雨型泥石流危险性评价

Hazard assessment of debris flow induced by short-time heavy rainfall based on RAMMS numerical simulation

浙江省由短时强降雨诱发的泥石流灾害频发,严重威胁当地居民的生命财产安全,因此对此类泥石流进行危险性评价对浙江省“灾害智治”工作具有十分重要的理论与实际应用价值。为研究浙江短时强降雨诱发小型泥石流的危险性,选取武山坑泥石流为对象,通过现场调查、三维倾斜摄影与数值模拟等手段,查明了武山坑泥石流的地质环境与发育特征,揭示了由短时强降雨诱发的泥石流灾害链生过程特征,选用RAMMS软件对不同降雨频率下泥石流运动特征进行了模拟,获取了泥石流深度、流速、堆积范围等特征参数,并基于特征参数进行了泥石流危险性评价。研究结果表明:陡坡处松散岩土体在短时强降雨作用下发生浅层滑坡,随后在坡面与沟道地形控制下向沟口运移,运动过程中通过侵蚀作用扩大泥石流规模,最终在宽缓堆积区沉积。随着研究区降雨强度增大至50 a一遇及100 a一遇,泥石流冲出规模扩大,但受限于堆积区宽缓的地形条件,未能于沟口形成有效冲出;但堆积扇上游居民区泥石流深度、流速等强度指标显著增大,堆积区内高强度区域面积大小由7276 m^(2)增大至12660 m^(2)。结合泥石流活跃性分析结果,采取形成区雨量监测、主沟谷流通区构建刚性、柔性或狭缝拦挡坝以及堆积区设置导流渠相结合的治理措施,可有效保障居民生命财产安全。研究成果可为武山坑及浙江省此类泥石流危险性评价、防治工程设计提供参考。

[Objective] Debris flows caused by short-term heavy rainfall are a frequent occurrence in Zhejiang Province and pose a serious threat to the lives and property of mountain residents.Therefore,the assessment of debris flow risk has significant theoretical and practical value for disaster management in the province.To investigate the hazard of debris flows caused by short-term heavy rainfall,the Wushankeng watershed was selected for research by means of field investigations and remote sensing interpretations,combined with numerical simulation.[Methods] The obtained results revealed the geological environment,development characteristics and disaster chain formation mechanism of debris flow in the watershed.The RAMMS numerical simulation software was used to simulate the debris flow depth and the velocity under different rainfall frequencies,and the hazard assessment was carried out based on these movement characteristics.[Results] The results of the research indicated that loose rock and soil at steep slopes experienced shallow landslides under the effect of short-term heavy rainfall.Then,under the control of the slope and gully topography,it migrated to the mouth of the gully,and during the movement,the scale of the debris flow was expanded by erosion.Finally,it was deposited in the wide and gentle accumulation area.As the intensity of the study area rainfall increased to a 50-year or 100-year occurrence,the scale of the debris flow increased,but it was limited by the gentle topographical conditions of the accumulation area,and it was unable to effectively discharge at the mouth of the gully.However,the indicators of mud depth and flow velocity in the resident areas upstream of the accumulation fan significantly increased,and the area of high-intensity areas in the accumulation area increased from 7 276 m^(2) to 12 660 m^(2).Combined with the results of debris flow activity analysis,the combination of rainfall monitoring in the formation area,constructing rigid,flexible,or slit check dams in the circulation area of the main channel,and setting up drainage channels in the accumulation area can effectively protect the lives and properties of residents.[Conclusion] The research results can provide reference for debris flow hazard assessment and engineering treatment in the study area and Zhejiang Province.