| Successful management of stormwater runoff depends on the ability of urban planners and managers to predict accurately and in advance the effects that increased urban development will have on stormwater runoff. Computer simulation models can be an effective means of analyzing the effects of stormwater runoff in urban areas. In this study, two models were used: The PCSWMM 2012 software (one of the most comprehensive urban runoff models and support system for EPA SWMM5), and the IDEAL model (Integrated Design and Evaluation Assessment of Loading), to examine if Low Impact Development (LID) can restore pre-development site hydrology and to quantify the amount of LID controls necessary to meet pre-development site hydrology. The design was adapted to three representative watersheds that are all located in Oklahoma. These included watersheds located in Weatherford (WO), Walnut Creek Watershed (WCW) located in Oklahoma City, and 51 at Tradan Heights watershed (SWW) located in Stillwater.;Several different scenarios were evaluated including rainfall from these three locations, pre-development scenarios, post-development scenarios, high and low infiltration soils, and Integrated Management Practices (IMPs) with partial infiltration (with underdrain) and with complete infiltration (without underdrain). The peak runoff rates and runoff volume of the above scenarios were compared and the percent runoff reductions of runoff were calculated. The amount of LID in each model was increased until pre-development peak flow rates and water balance were met; this was accomplished using design storm simulations. Each model was then analyzed with a continuous simulation using historic rainfall data from two of the locations. The LID controls that were modeled included: permeable pavement, bioretention cells, and rain barrels. Simulation results showed that LID controls reduced the amount of peak runoff to half.;The results also showed that LID can restore pre-development site hydrology and reduce stormwater runoff to meet stormwater requirements. |
