西藏东南部山洪灾害过程水文动力模拟和临界雨量

目的]研究西藏山洪致灾临界雨量确定方法,为西藏地区水文气象预警提供基础数据资料,以服务于高原山洪灾害防御工作。方法]采用水文动力模式Floodarea模型对西藏东南部的一次山洪过程进行模拟研究,并利用气象资料逐时降水量进行了淹没高度计算,得到了山洪致灾临界雨量。通过实地考察获取西藏自治区林芝市巴宜区2015年8月一次山洪灾害的基本参数资料,与模型模拟研究结果进行对比分析和模型验证。结果](1)Floodarea对暴雨诱发山洪过程的模拟结果较好,结合多源降水数据能更准确地模拟西藏山区山洪暴发的过程;(2)通过调整雨量情景设定可推算山洪不同淹没水深的临界雨量,得到较为准确的洪水淹没范围和降雨量—淹没深度关系;(3)应用降雨量—淹没深度关系计算得到巴宜区永久河山洪沟的4个淹没深度灾害山洪等级(0.1,0.6,1.2,1.8m)的6h累计临界雨量分别为33,55.7,75.4,91.9mm。结论]研究结果表明Floodarea软件适用于西藏高原水文观测资料匮乏的复杂地形山区,能较准确地重现山洪灾害过程和确定山洪临界雨量,可为复杂地形山区山洪防治和预警提供参考。

Hydrological Dynamics Simulation and Critical Rainfall for Flash Flood in Southeastern Tibet

Objective] In this paper, we aimed to determine the critical rainfall of flash flood in Tibet, in order to provide the basic data for hydrological and meteorological warning in Tibet and serve the flash flood prevention. Methods] We simulated the process of a flood in Southeastern Tibet by hydrodynamic model Floodarea, and calculated the submergence depth by using meteorological data of hourly precipitation, and we then obtained the critical rainfall of flash flood. To test the simulation result, we conducted a field survey to obtain the basic parameter of a flash flood disaster in August 2015 in Bayi Nyingchi region. Results] The Floodarea model could be well used in the simulation of rainfall induced mountain flood process. The critical rainfall of flood submerged in different water depth could be calculated by adjusting the rainfall scenarios. According to the relationships between rainfall amount and submergence depth, the critical 6 hours accumulated rainfall amounts in four mountain flood ditches with different submergence depths(0.1, 0.5, 1.2, 1.8 m) were 33, 55.7, 75.4 and 91.9 mm, respectively. Conclusion] Floodarea model software can be applied in the complex terrain mountainous areas that lack of hydrological observation data, in Tibetan Plateau. It can accurately simulate the flash flood disaster process and determine the critical rainfall. This study can provide reference for flood prevention and early warning in complex terrain mountainous areas.