High-resolution modeling of tsunami run-up flooding: a case study of flooding in Kamaishi city, Japan, induced by the 2011 Tohoku tsunami

Natural Hazards and Earth System Sciences. 2017;17:1871-1883 DOI 10.5194/nhess-17-1871-2017

 

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Journal Title: Natural Hazards and Earth System Sciences

ISSN: 1561-8633 (Print); 1684-9981 (Online)

Publisher: Copernicus Publications

Society/Institution: European Geosciences Union (EGU)

LCC Subject Category: Technology: Environmental technology. Sanitary engineering | Geography. Anthropology. Recreation: Environmental sciences | Science: Geology

Country of publisher: Germany

Language of fulltext: English

Full-text formats available: PDF, XML

 

AUTHORS

R. Akoh (Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan)
T. Ishikawa (Tokyo Institute of Technology, Kanagawa, 226-8503, Japan)
T. Ishikawa (retired)
T. Kojima (TOKEN C. E. E. Consultants Co., Ltd., Tokyo, 174-0004, Japan)
M. Tomaru (TOKEN C. E. E. Consultants Co., Ltd., Tokyo, 174-0004, Japan)
S. Maeno (Graduate School of Environmental and Life Science, Okayama University, Okayama, 700-8530, Japan)

EDITORIAL INFORMATION

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Time From Submission to Publication: 43 weeks

 

Abstract | Full Text

Run-up processes of the 2011 Tohoku tsunami into the city of Kamaishi, Japan, were simulated numerically using 2-D shallow water equations with a new treatment of building footprints. The model imposes an internal hydraulic condition of permeable and impermeable walls at the building footprint outline on unstructured triangular meshes. Digital data of the building footprint approximated by polygons were overlaid on a 1.0 m resolution terrain model. The hydraulic boundary conditions were ascertained using conventional tsunami propagation calculation from the seismic center to nearshore areas. Run-up flow calculations were conducted under the same hydraulic conditions for several cases having different building permeabilities. <br><br> Comparison of computation results with field data suggests that the case with a small amount of wall permeability gives better agreement than the case with impermeable condition. Spatial mapping of an indicator for run-up flow intensity (<i>I</i><sub>F</sub> = (<i>h</i><i>U</i><sup>2</sup>)<sub>max</sub>, where <i>h</i> and <i>U</i> respectively denote the inundation depth and flow velocity during the flood, shows fairly good correlation with the distribution of houses destroyed by flooding. As a possible mitigation measure, the influence of the buildings on the flow was assessed using a numerical experiment for solid buildings arrayed alternately in two lines along the coast. Results show that the buildings can prevent seawater from flowing straight to the city center while maintaining access to the sea.