Abstract Submission: A perennial constructed stormwater wetland (CSW 2.0) was re-designed in 2010 at Villanova University to manage stormwater runoff from a 47% impervious 17-hectare watershed on Villanova's campus. From the inlet structure, runoff flows through a series of three meanders and an outlet control structure to the downstream receiving Mill Creek. The design goal was to reduce peak flow and to treat stormwater pollutants over the lengthened residence time. To complement point-based monitoring data, a 2D HEC-RAS model for CSW 2.0 was developed to detail the hydraulic processes. An accurate terrain model is a crucial component of a comprehensive hydraulic model, which can be difficult to determine in a dynamic system like a CSW. To ensure the reliability of the HEC-RAS model, unique field data collection was performed to construct an accurate terrain input. The digital elevation model (DEM) included Trimble GPS survey point data, drone flight imaging, and hydrophone profiles to best depict elevation change throughout the system. Incorporation of the three differing elevation data required interpolation into existing USGS terrain files of the greater Philadelphia area using terrain modification tools in HEC-RAS and ArcGIS Pro. The drone digital surface model also contained detailed vegetation heights, which were used to assign appropriate roughness coefficients to account for the vegetation's seasonal effect on CSW 2.0 processes. With a robust terrain, model calibration introduced the Villanova Center for Resilient Water Systems decade-long inflow and outflow data as model boundary conditions, allowing for independent analysis on performance over time and by season. Results demonstrate the procedure to develop a robust terrain and the subsequent capability to simulate hydraulic processes including the terrain elevation impact.
