October 31, 2023

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Balancing Upland Green Infrastructure and Stream Restoration to Control Urban Watershed Nutrient Export

Finding the sweet spot between concentrating environmental restoration in the uplands and streams of urban watersheds.

Illustration of Stream restoration and 1-meter land use and land cover implementing low-impact development scenarios: reforestation, roadside bioswale, and permeable road.

Stream restoration and 1-meter land use and land cover implementing low-impact development scenarios: reforestation, roadside bioswale, and permeable road in Scotts Level Branch. The photo on the lower left shows a finished stream restoration project in Scotts Level Branch.

[Reprinted with permission from Zhang, R., et al. "Balancing Upland Green Infrastructure and Stream Restoration to Recover Urban Stormwater and Nitrate Load Retention." Journal of Hydrology 626 (Part B) 130364 (2023). DOI:10.1016/j.jhydrol.2023.130364.]

The Science

Restoration of urban watersheds to reduce nutrient pollutant loading is expensive and poorly understood. Current efforts often target remolding stream channels to retain more nutrients and sediment. However, stormwater contributions of impervious uplands create flow conditions that often negate stream restoration effects. Therefore, a balance must be established between the form and location of the stream channel restoration and the amount and type of restoration practiced in the watershed’s upland portion to minimize damaging stormwater flows from entering streams.

The Impact

This research provides tools and methods to help guide urban watershed restoration. Urban watershed management has often underperformed in goals, leading to a lack of understanding of how restoration can be designed as a holistic treatment of both uplands and receiving stream channels.

Summary

A team of researchers developed advanced models of urban stormwater best management practices, including increased tree canopy, roadside bioswales, pervious pavement, and in-stream channel restoration, to determine the most efficient combination of investing in upland and in-stream reductions in nutrient pollutant loads. Researchers applied the methods to an urbanized watershed in Baltimore that was constructed before most stormwater regulations and is under regulation to reduce nutrient exports to the Chesapeake Bay. Methods are mappable to the level of individual communities that may benefit from these activities and the Chesapeake Bay nutrient loads.

Principal Investigator

Lawrence Band
University of Virginia
[email protected]

Program Manager

Sally McFarlane
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Urban Integrated Field Laboratories
[email protected]

Funding

Before Baltimore Social-Environmental Collaborative (BSEC) funding, long-term data was collected through the National Science Foundation–funded Baltimore Ecosystem Study (Long-Term Ecological Research).

References

Zhang, R., et al. "Balancing Upland Green Infrastructure and Stream Restoration to Recover Urban Stormwater and Nitrate Load Retention." Journal of Hydrology 626 (Part B), 130364  (2023). https://doi.org/10.1016/j.jhydrol.2023.130364.