Prediction of urban inundation and flooding of urban rivers caused by heavy rainfall and storm surge in Tokyo 23 wards

In recent years, damage caused by heavy rainfall and typhoons has frequently occurred in various parts of Japan due to climate change. Countermeasure to this climate change is necessary especially in the coastal area, and it is important to investigate the influence of storm surge and typhoon on urban inundation. In light of this situation, the Flood Control Law, revised in 2015, created a system for publicizing the inundation areas related to largest possible flood, inland water and storm surges. For each possible impact, it is demanded in future to take appropriate measures. In this study, using the sophisticated urban inundation prediction system S-uiPS developed by the first author, we assumed that both large-scale torrential rain and storm surge would occur at the same time, and the process of inundation occurring in the 23 wards of Tokyo is examined. In 23 wards of Tokyo, the rainwater exclusion system consisting of roads, drainage pipes and urban rivers has been maintained, and inundation is reduced by draining the water to urban rivers. When the sea level goes up at the time of storm surge, the water surface elevation of the urban river which flows down to Tokyo Bay become higher. In this case, the inundation will occur due to the reverse flow to the drainage system through the storm-water outfall. The objective is to elucidate the range of storm surge effects in urban rivers, and to make clear the inundation process and the local inundation risk in urban areas.