Software for the hydraulic design of underground stormwater detention tanks

The quantitative and qualitative impacts of stormwater runoff have become a key issue in urban development design. Traditional methods of addressing the quantitative impacts of increased peak flows and increased runoff volumes, through stormwater detention/retention, have used above ground structures such as stormwater management ponds. Insufficient space, high land values, topography, maintenance, aesthetics and liability issues are reasons why underground detention is being considered more frequently. This chapter presents the development of a computer program for designing underground stormwater detention tanks. The program was developed by the Corrugated Steel Pipe Institute (CSPI) as a tool to simplify the hydraulic design of corrugated steel pipe (CSP) detention tanks. The program has four main functions: develop or allow the direct input of an inflow hydrograph, size the structure and develop a stage-storage relationship, design the release structure and develop the stage-discharge relationship, and route the inflow hydrograph through the structure The design methodology is the same as that used to design above ground systems, tailored to underground tanks. Two design examples are presented.