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Process Understanding of the Togagawa River Flooding 2008 Using a Distributed Rainfall-Runoff/Flood-Inundation Model

Author(s): Kenichiro Kobayashi

Linked Author(s): Kenichiro Kobayashi

Keywords: Togagawa River; Drainage network; Shallow water equation; Unsaturated flow equation;

Abstract: A very rapid rise of the river water level occurred in Togagawa River, Hyogo, Japan around 2:40 PM on July 28 2008 due to a localized so-called guerrilla rainfall. The water level rise at Kabutobashi Bridge was 1.3m during 2-3 minutes until 2:50 PM. 5 people including 3 children are dead due to the water level rise in the river. Tounderstand the process of the flooding in an urbanized area on the time, the authors made rainfall-runoff/flood-inundation models with 5 and 10m resolutions using a 2D surface flow simulation model based on a shallowwater equation coupled with a 2D subsurface flow model of the forest area with a depth-integrated unsaturatedflow equation. The river and drainage networks were also modelled. By analyzing the situation using the model,it was inferred that the water level rise was due to the rainwater falling mainly on the urban paved area and thecontribution of the water from the mountain area was not significant.

DOI: https://doi.org/10.3850/38WC092019-0642

Year: 2019

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