22nd IAHR-APD CONGRESS 2020 IN SAPPORO

Session6: Water-related Disaster Risk Reduction

6-7

Title: FLOOD DISASTER AND SAFE EVACUATION IN DRAINAGE AREA WITH SMALL RIVERS

Yukimi Wakayama, Taisuke Ishigaki


In recent years, fluvial flood damage has been mitigated by strengthening embankments, however, pluvial flood damage by heavy rainfall is increasing in mega and provincial cities. In August 2014, pluvial flood occurred in Fukuchiyama, where the drainage system includes small rivers. Such drainage system is popular in provincial cities, and small rivers cause widespread inundation. In order to enhance safety against such disasters, it is necessary to strengthen not only structural measures but also non-structural measures. The fluvial flood hazard map is mandatory, and pluvial flood hazard map should be made early. In hazard maps, the risk level is evaluated based on the inundation depth, but there are only few cases that evaluate the risk level including the flow condition. In this study, this kind of pluvial flood in Fukuchiyama is discussed with numerical results by InfoWorks ICM, which can be modelled rivers and sewerages. The inundation characteristics in this area showed that inundation started from the north and south side of the city, and spread from there. In addition, the inundation characteristics when pluvial flooding and fluvial flooding occurred at the same time were examined. The difficulty of evacuation was evaluated using specific force per unit width which can be able to consider fluid force and hydrostatic pressure simultaneously, and the time to start evacuation from small areas was discussed.





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