Development of a coupled coastal flood model of surge, wave, precipitation and sewer backflow for urban area

Abstract

 Compound physical processes of storm cause floods in coastal urban areas. The present study develops a coupled coastal flood model by considering the sequential physical process of surge overflow, wave overtopping/runup over breakwaters, surface runoff due to precipitation, and backwater from sewer systems. In the present coupled coastal flood model, a surge, wave and tide coupling numerical model (SuWAT) simulates the surge and wave. Integrated Formula of wave Overtopping and Runup Model (IFORM) calculates the wave overtopping discharge/overflow over the breakwater. The Storm Water Management Model (SWMM) estimates the surface runoff and backwater at each grid. The overflow rate, the surface runoff and the backwater are used for boundary conditions in inland flood calculations of SuWAT. The proposed model was applied to a simplified bathymetry to investigate the effect of the complex physical process by conducting a series of numerical experiments. As a result, the flood depth in the coastal urban area increased when all physical processes were considered. Earlier peak precipitation and allowed reverse flow caused the maximum flood depth. The results indicate that the developed model successfully simulates the coastal flood due to the compound factors of the surge overflow, wave overtopping, reverse flow of seawater, and backflow of rainwater through sewer systems.