Calibration of Urban Snow Process and Water Quality Model for Logan Airport

A USEPA Stormwater Management Model (SWMM) model incorporating snow processes was developed for Boston's Logan International Airport. The Logan model is unique in using calibrated urban snow processes for engineering analysis, and in coupling snow process simulation with pipe flow and mass transport. SWMM simulates snow processes using a modified degree-day approach. However, few US urban runoff models represent snow processes, and very few attempt calibration to winter conditions. While SWMM's process model omits solar radiation and snowpack albedo, its formulation was adequate for this application. The model simulates snow cover well both over the long term and for detailed simulation of complex snow handling operations at the airport. Debele et al. (2009) confirmed the practicality of the temperature-index approach. Long-term daily snowpack and temperature data were key to model calibration. Snowpack is available for 200 principal US climatological stations, and for 1,000 stations in the US Historical Climatology Network. As SWMM 5 graphically displays simulated and measured snowpack, and requires only hourly precipitation and daily maximum and minimum temperature as inputs, the procedures described here are adaptable for urban runoff models in the US and elsewhere.