Predicting Multiple Hazards under Extreme Rainstorms: Fid-Bau Portal

Predicting Multiple Hazards under Extreme Rainstorms

Zhou, S. Y. / Zhang, L. M. / Shen, P.

Due to the subtropical weather condition and the changing climate, Hong Kong is experiencing extreme rainstorms more and more frequently, which can trigger a large number of natural hazards such as landslides, debris flows, and flooding. These hazards do not occur separately, but often occur simultaneously or consecutively, and interact with each other, creating amplification and cascading effects. For example, landslides can provide loose materials for debris flows, and debris flows can cause surface erosion and blockage of flood-control facilities. Therefore, it is necessary to evaluate possible scenarios of geo-hazards under extreme rainstorms. This paper aims to predict regional multiple hazards under extreme rainstorms and hazard interactions. Previously, landslides, flooding, and debris flows are often considered as separate hazards and simulated individually. In this paper, an integrated full-process model (EDDA 2.0, Erosion-Deposition Debris flow Analysis 2.0) is implemented to predict slope failures, debris flows, and flooding in a single simulation. Slope stability is analyzed first, and then debris flow initiation from landslides and from surface erosion is considered. Dynamic changes of flow materials are also modeled in the program. The model is first validated with the historical records during the June 2008 rainstorm. Then consequences under three extreme storms (i.e. 44%, 65%, 85% of 24-h PMP, probable maximum precipitation) are predicted. The results show that with the increase of rainstorm intensity, the hazard magnitude increases dramatically, which can pose great threat to the society. This study can be helpful for multi-hazard risk assessment and government policy making.