Despite the water balances of cold region towns being dominated by low intensity, long duration snowmelt events, urban drainage systems continue to be designed according to standards developed for short, high intensity rain storms. During the 1980s and early 1990s, work in Scandinavia (Bengtsson, 1983, 1984, 1986; Westerström, 1984; Bengtsson and Westerström, 1992; Thorolfsson, 1990) and Canada (Xu and Buttle, 1987; Buttle and Xu, 1988, Todhunter et al., 1992) identified fundamental differences between rural and urban snowmelt processes. They found that snow properties such as density and albedo varied both between town and country and within the town depending on land-use. Moreover, both the longwave and shortwave radiation balances are heavily modified by buildings. Thus melt and runoff generation occurs at different times and rates. Town centres can have melt rates almost double that of residential areas. Despite snow removal policies, snowmelt in town centres is extremely important as these areas are the most likely to have combined sewer systems. These revelations will come as no surprise to practitioners working in cold regions, however, there is a lack of published material. This paper documents urban snow research from the last decade, it is both a summary and continuation of the state-of-the-art review found in a UNESCO special report on urban drainage in cold regions (Chapter 2, Semadeni-Davies and Bengtsson, 2000). Topics discussed include snow distribution, snow energy balance, frozen soil and runoff generation and modelling approaches - water quality issues are outside the scope. How to improve temporal and spatial resolution with limited budgets and limited data availability are ongoing problems, however, recent coupling between major urban drainage models such as SWMM and MOUSE and Geographic Information Systems offers a glimmer of hope. While full physically-based snow melt modelling is still out of the question, GIS could allow improved representations of snow distribution and energetics.
Semadeni-Davies, A. (2003). Urban Snowmelt Processes – Current Research and Modelling Needs. Lund, Sweden: Lund University, Deptartment Water Resources Engineering.
Stormwater; Towns and Cities