Abstract
To evaluate tsunami hazards with strong locality in urban areas, this study developed a novel tsunami inundation model based on nonlinear shallow water wave equations and a porous body model (PBM). By applying a kinematic boundary condition that includes both porosity and surface permeability of the porous medium, the proposed model could accurately incorporate geometric effects such as the flow anisotropy caused by the distributions of buildings. The proposed PBM demonstrated as good accuracy for the inundation heights around buildings near the coastline as with a conventional three-dimensional simulation with high resolution. In addition, the model showed its capability to reproduce a tsunami’s essential behaviors in urban areas. In particular, the amplification effect of flow velocity along straight roads surrounded by buildings was reasonably reproduced. It can be expected that the present model can become a useful tool to accurately evaluate the tsunami risks in urban areas.
Highlights
7a,b and Discussions show the maximum water level obtained by Landuse-n and the proposed porous body model (PBM), Figure 7a,b show the maximum water level obtained by Landuse-n and the PBM, respectively, where the green lines are the field survey resultby forLanduse-n the inundation areaproposed by Haraguchi
PBM, respectively, where the green lines are the field survey result for the inundation area by During the tsunami, the building destruction could lead to change the flow path respectively, where the green lines are the field survey result for the inundation area by Haraguchi and and and
(a) Difference between Coastal-forest and Landuse-n/Topography (b) Difference between Flood and Landuse-n/Topography (c) Difference between PBM and Landuse-n/Topography coastal-forest model, Flood: flood model, PBM: proposed model based on the porous body model) and and Landuse-n/Topography, where the green lines are the field survey result for the inundation area
Summary
The damage induced in heavily populated areas by the tsunami generated during the 2011 Great. East Japan Earthquake was enhanced because the tsunami struck an urban area [1,2]. The town of Onagawa, Miyagi Prefecture, Japan (shown in Figure 3), was one of the affected areas that suffered tremendous damage during the tsunami generated by the 2011 Great East Japan. The breakwater in the mouth of Onagawa Bay was greatly damaged, and the seabed around the opening was eroded by as much as 9 m [44]. Time series of the flow depths and flow velocities in urban areas were obtained from an analysis of video images by Koshimura et al [45], where the maximum flow depth and velocity in their analysis
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