NUMERICAL MODELING OF TSUNAMI INUNDATION OVER A COASTAL CITY CONSIDERING BUILDING VOLUMES

Abstract

 Although tsunami inundation calculations for urban areas have been performed using high-resolution topography and taking buildings directly into account, it is important to use a calculation method that uses a resolution coarser than the width of the building from the viewpoint of computational load.

 In this study, the model is improved by feeding back the building volume to the mass conservation law, which has not been considered in the subgrid-scale model iDFM, the averaged individual building drag model by Fukui et al. Replication of the idealized numerical and tsunami inundation experiments confirmed that the improved iDFM causes water exclusion in the grid due to the building volume, resulting in higher water levels and inundation depths than before the improvement. As a result, the accuracy of the inundation depth on the buildings near the shoreline, which tended to be underestimated before the improvement, was improved. In contrast, the overestimation of the inundation depth in the inland area (especially where the wet fraction in the grid is small) was confirmed.