Design of Storm Sewer Networks

Five methods for design of storm and combined sewers are compared by determining the size of the sewers of an example network. The Illinois Storm Sewer Systems Simulation (ISS) Model appears to be the most accurate method suitable for large expensive networks, and can also be used to study on-line retention storage. The conventionally used steady-flow routing method with shifting of hydrographs due to sewer flow time is simple and does not require use of a computer; thus it can be used for small networks and when high accuracy is not required. The version of steady-flow routing method without time shifting of hydrographs is not recommended because it consistently gives overdesign. The Chicago method provides no improvement in design and yet is more complicated than the time-shifting version of steady-flow routing method. The EPA Storm Water Management Model and the kinematic-wave model are improvements over the steady-flow routing method. They can be used for large networks but presumably are less accurate than the ISS Model.