SUBGRID MODELING OF STORM SURGE INUNDATION IN A COASTAL URBAN AREA CONSIDERING INFLOW AND OUTFLOW INTO BUILDINGS

Abstract

 In this study, a water volume term indicating inflow and outflow into buildings was added to the mass conservation law in iDFM, a building-aware storm surge inundation subgrid model. An idealized numerical experiment (30 m spatial resolution) was conducted on a simple urban topography with buildings aligned so that the spatial building density in the grid is approximately 40%, 25%, and 20%, and the inundation characteristics of the iDFM before and after the development were compared. When the inundation depth was considered, the inundation depth was reduced by 36.6%, 36.5%, and 6.18% on average, respectively, mainly around the run-up tip, compared to the case when the inundation depth was not considered, and the sensitivity of the inundation depth was large when the building density was greater than 25%. A similar study was conducted in a storm surge inundation calculation using a pseudo-warming experiment for Typhoon No. 19 in 2019 in the coastal area of Tokyo, and it was confirmed that the inundation depth was reduced by 22.5% on average when water infiltration inside buildings was considered, suggesting the influence of water flow inside buildings on inundation characteristics.