Inundation Analysis of the Oda River Basin in Japan during the Flood Event of 6–7 July 2018 Utilizing Local and Global Hydrographic Data

Shakti P C,Hideyuki Kamimera,Ryohei Misumi

doi:10.3390/w12041005

Shakti P C, Hideyuki Kamimera + Show 1 more

Open Access

https://doi.org/10.3390/w12041005

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Abstract

During the first week of July 2018, widespread flooding caused extensive damage across several river basins in western Japan. Among the affected basins were the Mabicho district of Kurashiki city in the lower part of the Oda river basin of the Okayama prefecture. An analysis of such a historical flood event can provide useful input for proper water resources management. Therefore, to improve our understanding of the flood inundation profile over the Oda river basin during the period of intense rainfall from 5–8 July 2018, the Rainfall-Runoff-Inundation (RRI) model was used, with radar rainfall data from the Japan Meteorological Agency (JMA) as the input. River geometries—width, depth, and embankments—of the Oda river were generated and applied in the simulation. Our results show that the Mabicho district flooding was due to a backwater effect and bursting embankments along the Oda River. The model setup was then redesigned, taking into account these factors. The simulated maximum flood-affected areas were then compared with data from the Japanese Geospatial Information Authority (GSI), which showed that the maximum flood inundation areas estimated by the RRI model and the GSI flood-affected area matched closely. River geometries were extracted from a high-resolution digital elevation model (DEM), combined with coarser resolution DEM data (global data), and then utilized to perform a hydrological simulation of the Oda river basin under the scenarios of backwater effect and embankment failure. While this approach produced a successful outcome in this study, this is a case study for a single river basin in Japan. However, the fact that these results yielded valid information on the extent of flood inundation over the flood-affected area suggests that such an approach could be applicable to any river basin.

Highlights

Flooding due to extreme rainfall causes loss of life, infrastructure damage, and significant economic loss in many countries every year, making it a major threat to human civilization [1,2]
In a previous study done by P.C. and Kamimera [37], default empirical equations were used to generate river width (RW) and river depth (RD) with no embankments, with clear indications that river geometry reconstruction is necessary to obtain correct information on flood inundation over the basin
Oda river are acceptable for further that model performance similar for the event analyzed here; we suggest that there is no need inundation analysis overwas the basin

Summary

Introduction

Flooding due to extreme rainfall causes loss of life, infrastructure damage, and significant economic loss in many countries every year, making it a major threat to human civilization [1,2]. Unpredictable rainfall behavior over complex urban systems and changing environments may cause an increased risk of flooding. Previous studies have suggested that the frequency of extreme, short duration rainfall events is increasing, such that there may be a higher chance of increased magnitudes and frequencies of flooding [1,3]. Projection reports suggest that flood frequency may increase, especially over southeast Asia [4,5]. In Japan, torrential rainfall and heavy floods are common and occur during the rainy season Understanding the hydrological response to these past events can be a good reference for the proper management of future water-related disasters.

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