Conclusion

In this study, the physical process of three major rainfall derived infiltration and inflow (RDII) sources: roof downspout, sump pump, and leaky lateral, were investigated using physics-based models. These three sources represent three different flow patterns through: a direct connection of runoff catchments, course porous media, and compacted soil, respectively. The typical flow response of each RDII source was expressed as impulse response functions (IRFs) that indicate the flow responses to a representative rainfall. Three IRFs were superposed to produce the total RDII flows and the weighting factors of each IRF were calculated using the actual sewer flow data in a few neighborhoods in Illinois based on a genetic algorithm (GA) technique. The results can shed light on identifying the contributions of different RDII sources in a sewershed that enables decision makers to better understand the local RDII issues which in turn facilitates a more effective management of the sewer system.