Urban Stream Restoration Practices: An Initial Assessment

Urban stream restoration projects are being designed and constructed in increasing numbers across the country. Numerous stream restoration techniques are being employed that vary from “hard” structural approaches to “soft” bioengineering approaches. The one factor that all stream restoration projects share, however, are the individual stream restoration practices that together make up a stream restoration project. A recent study by Brown (2000) examined 24 different types of stream restoration practices and included over 450 individual practice installations. The practice types were broadly classified into four practice groups based on their intended restoration objective: bank protection, grade control, flow deflection/concentration and bank stabilization. Each practice was evaluated in the field according to four simple visual criteria: structural integrity, function, habitat enhancement, and vegetative stability. Our assessment of urban stream restoration practices found that most practices, when sized, located, and installed correctly, worked reasonably well and are appropriate for use in urban streams. Of the 24 practices evaluated, only two appeared to have questionable value in urban stream restoration. Overall, nearly 90% of the individual stream restoration practices assessed remained intact after an average of four years. This result suggests that most stream restoration practices have the potential for longevity. Yet, 20 to 30% experienced some degree of unintended scouring or sediment deposition, indicating the potential for future failure. While the vast majority of practices remained intact, only 78% fully achieved the practice objective. The greatest deficiency identified was the ability of the practices to enhance habitat. Less than 60% of the practices fully achieved even limited objectives for habitat enhancement. Most importantly, this study found that the key factors for practice success were a thorough understanding of stream processes and an accurate assessment of current and future stream channel conditions. This paper presents only a summary of the findings from the study. The complete study methodology and detailed findings are presented in Urban Stream Restoration Practices: An Initial Assessment published by The Center for Watershed Protection, Ellicott City, MD.