Topographical features of the City of Nagoya, characterized by flat land and hills in the eastern part, make storm drainage and flood control particularly important in this urban region. In the provision of land drainage, small and medium rivers in the City play an important role, but they generally lack adequate hydraulic capacity. Furthermore, there are sewered areas in the city where the local topography, characterized by depressions or sudden breaks in surface slopes between flat and inclining planes cause local flooding and water ponding. Consequently, the city has adopted a flood control program comprising construction of storage tanks in the areas susceptible to flooding, or where the hydraulic capacity of rivers is unreliable. The main concepts of this program include the construction of a variety of storage tanks designed to suit the local flood protection requirements. Scarcity of construction sites makes effective land utilization mandatory, so storage tanks are designed as facilities with dual functions serving as both flood and combined sewer overflow (CSO) controls, and, whenever feasible, the storage tanks are designed and implemented in conjunction with the existing facilities.