Rain-on-Snow Project

Brandon Morgan, Colin Huber, Keegan Pederson


The effects of rain-on-snow events are typically neglected during stormwater management design in Monroe County, NY and climatically similar regions. A study was conducted to examine the validity of this methodology by analyzing the combination of meltwater and precipitation over impermeable frozen ground. Studies were conducted using historical meteorological data for March and a theoretical test site located in Monroe County, NY for return periods of: 1, 2, 5, 10, 25, and 100 years. Meltwater flowrates and equivalent depths were calculated from March precipitation data using equations derived from thermodynamic principles. The March meltwater depths were compared to annual precipitation depths typically used in rainfall runoff analyses. It was determined that March rain-on-snow runoff depths were significantly less than annual precipitation rates for each of the return periods. Sensitivity analyses were conducted in order to determine the effects of snow pack depth and air temperature. Additionally, sensitivity analyses of the soil type and land use on the pre and post-development peak flows for the test site were conducted. The study confirmed that the runoff from rain-on-snow events is minimal in terms of percentage and overall magnitude compared to annual precipitation depths. Therefore, the current practice of neglecting rain-on-snow events during stormwater management design is valid in Monroe County, NY and climatically similar regions.


Stormwater Management, Rain-on-snow, Northeast United States

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