Redesigning Constructed Stormwater Wetlands: An Integrated Modeling Approach to Optimize Form and Function

Constructed stormwater wetlands (CSWs) have tremendous potential in managing stormwater runoff. These systems are shallow marsh environments that are built to minimize both peak flow rates and contaminant loads to aquatic ecosystems following storm events. In order to meet these goals, CSWs are constructed with few guiding principals. Despite these principles, little research has been conducted to optimize the biological, chemical, and physical processes involved in stormwater mitigation. A four tiered modeling approach is underway to redesign Villanova's CSW, however, this paper focuses on MIKE 11 a hydraulic model. Four plan view designs were created which included a one pond, two pond, one pond and meander, and continuous meander design. Using the same inflow data, a modeled outflow hydrograph was simulated. Three parameters were obtained from this hydrograph: peak flow rate, time to discharge, and time rate of change of flow. The best performing design was the continuous meander design which had the lowest peak flow rate, longest stormwater discharge time, and lowest mean change in flow rate. The second best performing design was the one pond design. As a general rule of thumb, increasing the length to width ratio increases the hydraulic performance. Although this may be true, the single pond design had the lowest length to width ratio but was the second best performing model. Based on these results, volume storage was the best predictor of model performance.