Study on Inundation in the Coastal City Due to Heavy Rainfall Considering the Effect of Global Warming

Urbanization in the coastal area leads to inundation during heavy rainfall is the common problem. The reason for inundation is heavy rainfall, tidal phenomenon, sewerage system, and also rise of sea water level due to global warming. The frequency of heavy rainfall increasing in the recent year cause severe flooding. Flooding poses a threat to life and safety and can cause severe damage to public and private property. The aim of this study is to analysis the inundation situation of Nagoya city due to heavy rainfall considering the effect of global warming. The analysis region is around the Nagoya bay area, Nagoya city, rivers and streams which terminated into Nagoya bay area. Nagoya city is one of the largest city locates in central Japan. Sewerage system in the Nagoya city is also considered in this analysis. Sewerage system performs a vital role to drain the city area during heavy rainfall. The sewerage system is connected to the sea and rivers. Sewerage water is discharged to the sea and river through pumps. In this study, the water behavior due to heavy rainfall and other several cases such as tidal phenomenon existing sewerage system is considered. A synthetic analysis model is developed which includes sea model, inundation model, river model and sewer system model. Developed hydrodynamic model based on finite volume method solving the shallow water equation. The inundation water depth during heavy rainfall is examined by numerical simulation. Moreover, rise of sea water level due to global warming is also considered in this analysis. The inundation in two different cases such as considering global warming and without global warming (i.e. sea water level set 0.95m and 0m) are analyzed. Moreover, the inundation situation is evaluated and finally recommends appropriate mitigation measure is recommended.