Analyzing Urban Rain-on-Snow Events: Impacts and Stormwater Management Solutions

Abstract Submission: Climate impacts have been causing changes in weather patterns, increasing extreme weather events, and changing the frequency and timing of rain-on-snow events. These events generate more runoff compared to rainfall or snowfall alone, making them a critical concern for stormwater management. While rain-on-snow events have been studied in mountainous regions, research on their impacts in urban areas with high imperviousness in the United States remains limited. Previous literature revealed that Low Impact Development designs and detention ponds worked best in cold climates to mitigate excess runoff. In this study, historical climate data from the National Weather Service are used to analyze the frequency and extremity of rain-on-snow events in various U.S. urban areas, with their hydrologic impacts simulated through the Storm Water Management Model (SWMM). The study aims to identify those regions likely to experience more frequent rain-on-snow events due to climate change and evaluate the best stormwater control measures for those regions. We found that varying definitions of rain-on-snow events can influence the number and type of events identified. Of particular interest were those events that have a significant hydrologic impact in urban areas, causing more runoff. Future work will involve simulating extreme rain-on-snow events through SWMM, analyzing the effects of those events in urban areas, and categorizing those events based on hydrologic impacts.

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