Unintended consequences of urban stream restoration.

Excess nitrogen (N) and phosphorus (P) from human activities have contributed to degradation of coastal waters globally. A growing body of work suggests that hydrologically restoring streams and rivers in agricultural and urban watersheds has potential to increase N and P retention. However, certain restoration techniques and circumstances may yield unintended, undesired consequences including low dissolved oxygen levels, metal and phosphorus mobilization, loss of biota, loss of riparian trees, and increased sediment loads from banks. Using recent case studies and our long-term data sets from urban study sites in Maryland, Washington DC and Pennsylvania, I discuss the causes of undesired consequences of stream restoration and suggest approaches to achieve desired outcomes such as N removal and biological uplift.

Impact/Purpose

This invited presentation is a follow up to the meetings I attended to contribute to the document produced by the Urban Stormwater Work Group that revised and updated the “Consensus Recommendations for Improving Protocols 2 and 3 on Effect of Stream and Floodplain Restoration Projects Built for Pollutant Removal Credit” completed in 2020. https://www.chesapeakebay.net/documents/FINAL_Approved_Group_4_Memo_10.27.20.pdf. This meeting will be attended by resource agencies and practitioners throughout the Chesapeake Bay and Mid-Atlantic to better understand how to address nutrient management of the Bay watershed and utilize stream restoration as a BMP to receive nutrient credits under the Chesapeake Bay TMDL.

Citation

Mayer, P. Unintended consequences of urban stream restoration. Bay-wide Stormwater Runoff Rendezvous, Urban Stormwater Workgroup, NA, MD, April 06, 2021.