Wetland modeling in PCSWMM to predict impacts of urbanization

Wetlands in Southern Ontario are experiencing degradation from urban development. Hydrologic analysis is important to demonstrate that a development will not have negative impacts on wetlands. A wetland water balance study has been conducted to develop reference hydrologic regimes for two wetlands in Pickering, Ontario. Knowledge gained from wetland water balance analysis informed the development of PCSWMM models. The modelling went beyond quantifying changes in surface runoff and infiltrated water on the catchments to include the wetlands and predictions of their hydrologic response to urban development (i.e. changes to the wetland hydroperiods). The objective of this study was to explore options for incorporating and defining wetlands in PCSWMM, select groundwater interaction parameters, and optimize the process for creating a calibrated catchment-wetland model using known seasonal wetland water levels. Continuous monitoring data was used for calibration and validation of the models. Methods, calibration targets, and challenges encountered when defining groundwater interactions and stage-storage relationships will be highlighted. The study will identify areas where increased data collection could improve the model parameterization. The discussion will address the value of a model which can both adequately represent the development and the wetland by incorporating infiltration/runoff effects, evapotranspiration changes, LID practices, groundwater regimes, and dynamic feedbacks between the wetland water level and the system.