Hybrid Approach in Surface Flow Modelling for Regional-Scale Flood Inundation Mapping
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With the alarming increase of extreme weather events in recent years, comes a corresponding increase in exposure and vulnerability to flooding hazards. To mitigate the effects of these hazards, several works have been done in pursuit of accurate and reliable prediction of flood inundation. Regional-scale flooding and inundation analyses have been particularly relevant in disaster management due to its capability of simultaneously covering multiple locations over wide areas. However, one of the known challenges in regional-scale flood inundation analyses is the trade-off between the size, resolution, and extent of the computational domain with the accuracy and computational efficiency of the numerical calculations involved. To address this concern, simplified surface flow models of the two-dimensional shallow water equations are utilized. Particularly, a hybrid approach of the zero-inertia and the local-inertia flow models is introduced. This approach takes advantage of the numerical stability and computational efficiency of each model allowing for regional-scale analyses with larger computational domains or higher spatial resolutions. The model is applied in Marumori, Japan which sustained a number of flooding disasters during Typhoon Hagibis in 2019. Validation indicates that the model could successfully simulate the hydrologic response when compared with observed channel flow and inundation depths.
