Science Serving Maryland's Coasts


Development of A Technical Brief to Guide Stream Restoration Strategies to Reduce Nitrogen Loads in Urbanizing Chesapeake Bay Watersheds

Principal Investigator: 

Sujay Kaushal

Start/End Year: 

2011 to 2013


University of Maryland, College Park

Strategic focus area: 

Viable coastal communities and economies


OBJECTIVES: We propose to create a technical brief that can guide decisions regarding stream restoration and that can be used by water quality managers to examine if/when stream restoration may be effective, inform restoration approaches based on site characteristics, and identify factors contributing to variability in outcomes.

METHODOLOGY: The technical brief will contain a: (1) literature synthesis (2) meta-analysis, and (3) decision support tool. The proposed research will investigate stream restoration effectiveness by conducting a literature synthesis profiling projects and successful and unsuccessful outcomes, performing a meta-analysis of existing data on rates of N removal, and develop a decision support tool based on results from the meta-analysis. Generally, engineered approaches to stream restoration have fallen into two broad categories, 1) in-stream manipulation and 2) integrated stream-wetland complexes. The literature synthesis and meta-analysis will involve comprehensively searching the literature for all available published data, as well as grey literature, at global, state, and local levels with an emphasis on Maryland Piedmont streams. We will identify and specify criteria for selection of papers and guidelines for QA/QC of data sets. We will extract information on % N removal from the papers and reports, and develop a standard metric of N removal for study comparison. We will then identify appropriate a priori methods for the analysis of data including curvilinear fits, categorization of data into explanatory variables and controls. This information will be used to construct a decision support tool and conceptual model for guiding stream restoration and informing if/when restoration approaches are likely to be effective within a watershed context. We will submit a draft version of the technical brief for peer review and demonstration at a pilot user workshop. Once we receive feedback, we will revise, prepare the final technical brief, submit for publication as a peer-reviewed EPA Technical Brief, and disseminate to end users via a workshop and websites.

RATIONALE: Water quality managers are faced with increasing regulatory requirements such as Total Maximum Daily Loads and permitting to reduce nitrogen loads in coastal tributaries. Various best management practices including source reduction, land-use management, and riparian buffers are employed to remediate stream impairment from nutrients. A growing body of literature from research conducted in Maryland and elsewhere suggests that stream restoration may have the potential to represent an effective nutrient BMP because denitrification and N removal in streams can increase after restoration under certain conditions. Stream restoration can be performed in areas that were developed in uplands prior to current stormwater regulations and can be coupled with bank stabilization efforts and repair of aging storm water and sanitary infrastructure. However, there may be variability in outcomes and effectiveness of N removal associated with different engineered stream restoration approaches (in-stream manipulation vs. integrated stream-wetland complexes). Although research on stream restoration has been distributed in the peer-reviewed literature, it has not been synthesized and summarized into an easy to use technical brief, particularly suited for water quality managers in the region where measurements were made. We propose to develop a technical brief based on comprehensive analysis of all available empirical data and also within a geographic context of where data were collected, that will aid water quality managers in efforts to effectively employ stream restoration in urbanizing watersheds of the Maryland Piedmont. We will leverage previously funded research from U.S. Environmental Protection Agency (EPA), Maryland Sea Grant, and National Science Foundation that has quantified effects of urban stream and wetland restoration on denitrification and N removal with varying site characteristics and engineered stream restoration approaches.


This section describes how this project has advanced scientific knowledge and/or made a difference in the lives of coastal residents, communities, and environments. Maryland Sea Grant has reported these details to the National Oceanic and Atmospheric Administration (NOAA), one of our funding sponsors.

SUMMARY: Research on effective strategies for stream restoration was developed, synthesized, approved by expert panels, shared with resource managers and used to update the Chesapeake Bay Program’s watershed model for water quality..

RELEVANCE: Local officials and water quality managers in Maryland are looking for ways to comply with regulatory requirements to reduce loads of nitrogen, phosphorus, and sediments in coastal tributaries. The Environmental Protection Agency has established a set of targets (TMDLs or Total Maximum Daily Loads) that states and municipalities must achieve by 2025, and milestone loads for 2017, to improve water quality in the Chesapeake Bay. One method for municipalities to comply is to carry out projects to restore buried streams in urban areas. Restoring streams to their natural flow patterns can reduce nitrogen levels there and in downstream tributaries by increasing natural nitrogen-reduction and denitrification processes; such processes are minimal or absent in streams engineered to flow only through pipes and restricted channels. By tracking the locations and methods used to restore these streams, water quality managers can calculate reductions in nitrogen that local officials can report to the EPA’s Chesapeake Bay Program as helping to meet nitrogen-reduction targets.

Although research on stream restoration has been distributed in the peer-reviewed literature, it has not been synthesized and summarized into an easy-to-use format suited for water-quality managers in Maryland’s Piedmont region. For several years, Maryland Sea Grant funded basic research on stream research by this principal investigator and his graduate students that laid the groundwork for this project to produce such a synthesis.

RESPONSE: The principal investigator of this research effort is Sujay Kaushal of the University of Maryland, College Park. He and colleagues conducted a meta-analysis and literature synthesis of peer-reviewed studies and produced six publications relevant to determining nitrogen-load reductions associated with particular techniques used for stream restoration. Kaushal participated in an expert panel that incorporated this research in a synthesis report defining the qualifying conditions under which local stream restoration projects may be eligible to receive credit for reducing nitrogen transport.

RESULTS: In 2013 the expert panel’s synthesis report was accepted by the Chesapeake Bay Program Water Quality Goal Implementation Team and other program oversight panels. The Chesapeake Bay Program used the findings to update its Watershed Model, which it uses to assess compliance with nitrogen-reduction targets. Kaushal participated in a series of workshops and webinars to share these research findings with local water quality managers in the Chesapeake Bay region. The findings are being further disseminated by two nongovernmental organizations working closely with Kaushal, the Center for Watershed Protection and the Chesapeake Stormwater Network. Going forward, these methods and findings about stream restoration are expected to be used widely by local officials to help satisfy the Chesapeake Bay’s TMDL regulatory requirements.

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