Cities across the United States are struggling with issues of storm water because buildings and roads cannot soak up rain like soil. Instead, rain that falls on cities runs off the buildings and roads. Cities are spending billions of dollars to manage this extra water. They are investing in green infrastructure, which is infrastructure on the land that can soak up and hold rainwater. One of these green infrastructure approaches is storm water ponds. However, across the southeastern U.S., beaver live in urban streams, and they build ponds, too. Beaver are considered a nuisance species and are often killed, even though their ponds may be similar to storm water ponds for slowing water and improving water quality. The first goal of this project is to compare how well beaver ponds store water during both dry and wet periods compared to storm water ponds. In addition to retaining and slowing the flow of storm water from cities, both beaver and storm water ponds receive nutrients than can feed algae blooms. The second goal of this project is to evaluate if urban beaver ponds increase the storage of nutrients and sediments from water that passes through their dams. This is important because it will improve downstream water quality. The final goal of this project is to map where beaver may be building these ponds in urban areas. This will inform city managers on what to do with the ponds. To determine if the ponds work the same way in different cities, this work will be conducted in Atlanta, GA, Charlotte, NC, and Raleigh-Durham-Chapel Hill, NC. The project will provide multiple broader impacts, including increasing diversity in the geosciences, collaborating with conservation groups, such as Adopt-a-Stream and Chattahoochee Riverkeeper, to educate the general public about the benefits of beaver, and helping local watershed managers to better manage beaver and adopt benefits that might exist from their ponds. In addition, this research will be done at multiple minority serving institutions by a diverse group of investigators. The multi-institution project will allow students to collaborate across institutions.
This project will test a conceptual model of how the physical features of urban beaver and stormwater ponds impact streamflow attenuation and water quality. Cities are spending billions of dollars on installing green infrastructure to capture stormwater runoff, when cities in the southeastern U.S. may have infrastructure that fills a similar role already in beaver ponds. The functioning of beaver ponds compared to stormwater ponds has not been systematically studied anywhere. This project aims at (1) quantifying the nutrient and sediment retention of beaver and stormwater ponds, (2) quantifying the transit time of water through beaver and stormwater ponds and floodplain-stream reconnection around dams at both high and low flow, and (3) using remote sensing products and GIS to estimate the total number of beaver ponds in cities and scale-up quantification of retention to the whole-city scale. The hypothesis for objectives 1 and 2 is that the hydrologic and nutrient retention response of the pond will be driven by the hydrologic source of the water—specifically inflows dominated by surface or groundwater—and readily quantifiable metrics of pond geomorphology. The hypothesis for objective 3 is that identified ponded water from aerial imagery can be combined with the drivers of beaver habitat, including stream slope and vegetation, to pinpoint locations of beaver activity. The project entails conducting field work on urban beaver dams and stormwater ponds in the Piedmont cities of Atlanta, GA, and Charlotte and Raleigh, NC to compare influent to effluent mass fluxes of nutrients and total suspended solids (TSS) over two years, sample hyporheic waters in the dam and floodplain to understand nutrient cycling in the sediments and quantify travel time distributions of water through beaver ponds and how they compare to engineered stormwater ponds. The proposed research will develop a conceptual framework through rigorous testing using intensive field studies that will yield new and transformative knowledge within the field of urban hydrological science. The study will be carried across a range of factors, including pond size, watershed land use, sediment, geology, and infrastructure age to assess controlling drivers and predict the response in other systems. In addition, larger-scale mapping of these systems will help to evaluate landscape-level impacts on entire cities.In addition to the intellectual merits, this project will increase diversity in STEM by recruiting underrepresented students to complete M.S. degrees at minority serving institutions, mentored by a diverse group of faculty. The project will also entail public outreach on the ecological benefits of beaver leveraging existing relationships with non-profit conservation groups. Beaver are considered a nuisance species, and thus to reap the benefits their ponds may have on hydrologic and nutrient retention, conversations between watershed managers and beaver pond neighbors must be facilitated to allow for science-based decisions on the fate of these ponds.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
