Stormwater and flooding on the UNR campus: A current and future modeling assessment
AuthorHenning, Jessica Lynn
Environmental Sciences and Health
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Abstract. The University of Nevada, Reno (UNR) has experienced significant flooding problems in the past decades. This flooding is partially a consequence of the routing of Evans Creek into the storm sewer system under south campus. The south campus storm sewer system has a capacity of 245 cubic feet per second (CFS) maximum. When rainfall increases Evans Creek flow, stormwater runoff backs up on campus and floods, causing significant monetary damage to buildings. Low impact development (LID) is a mitigation technique used to reduce stormwater runoff and associated flooding events. The Win TR-55 model was used to determine peak flows for storm return periods of 2, 5, 10, 25, 50 and 100 years using the Type II rainfall distribution and 24 hour storm duration. The UNR campus was split into two main areas due to the storm sewer system routing. These areas were further broken up into sub-basins using 1 ft elevation contours, land use and location of stormwater pipes as criteria. Land use was determined from aerial photography and quantified using ESRI ArcGIS (geographic information systems) desktop applications. Land use was entered in the Win TR-55 model to determine an area-weighted average curve number for each sub-basin. Flow was then routed through the designated storm sewer section for each sub-basin. A routing schematic was developed for the two areas. The land use characteristics were then modified to illustrate the difference between current conditions and the implementation of LID practices, specifically employing permeable pavements (80%, 60% and 40% pervious area) for all sidewalk and parking lot areas. All model scenarios were run three times, at the average, dry and near saturation moisture conditions. Results indicate that the south campus storm sewer system can handle precipitation falling directly onto campus. The use of permeable pavements leads to a small change in flow (~30 CFS) when permeable pavements are introduced to the model. However the primary source of stormwater runoff flow orginates from Evans Creek, not the UNR campus. Reductions due to pervious pavements will not make a difference in flooding situations. Other mitigation options should be considered for the Evan's Creek watershed to reduce the flooding impacts in on the UNR campus.