| Description |
With the aging water infrastructure becoming a concern, sustainable solutions have become a focus. Green stormwater infrastructure such as bioretention, pervious pavement, and green roofs are becoming more common solutions to this problem. Much of the research focus on these technologies focuses on warmer climates not affected by snow or ice. The objective of this study is to determine whether regulatory agencies in cold weather states need to amend current requirements for stormwater treatment design to include snowmelt modeling. In this study, a generalized simulation is employed by modeling the cold weather performance of bioretention cells in three cities: Salt Lake City, Boston, and Milwaukee. These cities were chosen as test cities from survey participants for the Environmental Protection Agency (EPA) Community-enabled Lifecycle Analysis of Stormwater Infrastructure Costs (CLASIC) project. Models were setup using EPA Storm Water Management Model (SWMM) to simulate performance of a bioretention cell attached to a half-acre, 65% impervious lot. Each city has a model to only simulate precipitation as rain and a second model that treats precipitation as snowfall when certain parameters are met. Hydrologic simulations were run from January 1, 1990 to December 31, 2009. Precipitation and temperature data were obtained through National Oceanic and Atmospheric Administration (NOAA) from each city's airport station. To determine variables for infiltration calculations, a soil map was generated for the downtown area of each city using the United States Department of Agriculture iv (USDA) Web Soil Survey. To determine snowmelt factors, long-term data from the nearest Snow Telemetry (SNOTEL) site to each city was used. Models were surprisingly insensitive to changes of inputs that calculate heat transfer rates between snowpack and surrounding environment and moderately sensitive to those inputs regarding soil temperature and temperature during which snow occurs. Climate change results only show a small change of the percentage of precipitation that occurs as runoff or infiltration. Monthly results show an increase in bioretention runoff depth and the number of runoff events, while infiltration loss decreased during winter months. Results in summer months remained unchanged when comparing presnow vs. snow models. Boston showed the greatest differences in results between presnow and snow models, while Salt Lake City had the smallest difference. The compilation of all the results suggest that no amendment is needed to bioretention sizing to account for the effects of cold weather. Better proximity to soil temperature and SNOTEL data would improve Boston and Milwaukee models. Results are muted due to the small magnitude of snowmelt runoff events and snow depths being represented as snow water equivalent. I |
