Glendale/Peoria ADMPU, Northwest Region Update, Hydrologic Study

WOODPATEL managed the study to update hydrologic computer models to address the impact of new development, future development and capital improvement projects (CIP) on the watershed hydrology. Since the completion of the ADMPU (2002), several significant developments had been constructed and new developments were in various stages of planning and design within the 35 square mile watershed. Both existing and future conditions were modeled for the 10-year and 100-year, 6-hour storm and the 100-year, 24-hour storm. Existing conditions included developments that were under construction and funded CIP drainage improvements within the watershed. Future conditions included planned CIP drainage improvements. For future conditions, land uses were assumed to be fully developed which incorporated additional on-site retention. The study evaluated the impacts of NOAA 14 precipitation depths and illustrated that the updated peak discharges would be significantly lower than those identified in the ADMPU models. Two major factors contributed to the lower runoff estimates. The first factor was the unit hydrograph computational routine (MCUHP1). The second factor is that detention/retention facilities within the new developments reduce the peak discharges.