Numerical Simulation of Debris Flows of the Catastrophic Event of February 2019 in Mirave - Peru

Abstract Debris flows are geophysical phenomena, caused by torrential rain, which occur in mountainous areas, characterized by the detachment of slope and riverbed materials and their consequent dislodge through watersheds and streams. Debris flows usually carry sludge, water and rocks, and can destroy everything in their path. On February 8th, 2019, an event of this type occurred and destroyed Mirave’s community in Peru, which was located in the areas of transport and deposition of debris flows. This research presents the modeling and numerical simulation to reproduce the transport and deposition processes of the debris flow that occurred in Mirave. The initiation process of the debris flow in streams was represented by hydrographs obtained from the estimated rain runoff volumes and solid materials found at each evaluated micro watershed. The numerical simulation results show acceptable results in terms of reproduction of the extension of the affectation and deposition areas of solids related to the studied debris flow. The resulting velocity field shows an adequate representation of the erosion zones observed in the area. The model used for evaluating the disaster risk by debris flows can predict and delimit, with acceptable accuracy, the potentially dangerous areas for a mudslide event. The application of the proposed methodology for assessing the disaster risk due to debris flows at watersheds and streams is useful to understand the extent of debris flow affectation during extreme weather events, as well as to develop emergency plans, and to formulate disaster management policies in Peru or in other countries with similar conditions.摘要 泥石流是一类由暴雨引发的地球物理现象，多发于山区，其核心特征为边坡与河床物质失稳剥离，并沿流域与河道发生运移。泥石流通常裹挟泥浆、水体与石块，可摧毁途经区域内的一切物体。2019年2月8日，秘鲁米拉韦社区遭遇此类灾害，该社区正处于此次泥石流的搬运与沉积影响范围内。本研究针对该次泥石流的搬运与沉积过程开展建模与数值模拟，以实现过程重现。泥石流在河道中的起始过程，通过各评估小流域的估算降雨径流量与获取的固体物质得到的流量过程线进行表征。数值模拟结果显示，其在重现本次泥石流影响范围与固体沉积区域方面表现良好；所得速度场可较好表征研究区域内观测到的侵蚀区域。该用于泥石流灾害风险评估的模型，能够以可接受的精度预测并划定泥石流事件中的潜在危险区域。本研究提出的适用于流域与河道的泥石流灾害风险评估方法，有助于理解极端天气事件中泥石流的影响范围，同时可为秘鲁或其他条件相似国家制定应急预案与灾害管理政策提供有效支撑。