A monitoring and assessment framework to evaluate stream restoration needs in urbanizing watersheds

Urbanization has a significant impact on rivers and streams, modifying flows, sediment loads, channel morphology, water quality and nutrient processing, and aquatic biota. Because of these impacts, a majority of the streams in urban and urbanizing watersheds are reported on §303(d) state lists as impaired from siltation, habitat alteration, nutrients, bacteria, and other stressors. States are required to develop total maximum daily loads (TMDLs) under 40 CFR 130, and watershed-scale implementation plans are produced to rehabilitate impaired streams by achieving target TMDL allocations. Stream restoration practices are commonly used as corrective measures to meet TMDLs, particularly for siltation and habitat alteration. However, urban stream restoration typically consists of reach-scale projects that may not be well integrated into a watershed corrective plan. Rather, project scope and location are commonly determined by local perceptions of need and accessibility. Watershed planning is needed in urbanizing watersheds for various reasons. Most importantly, planning is needed because hydrology and sediment loads change as developments occur over time until ultimate build-out, and future infrastructure constraints affect channel planform stability. These reasons underscore the critical need for restoration projects to be implemented based on a watershed plan, and a plan that integrates implementation of stormwater management best management practices (BMPs). The objective of this paper is to present a framework for monitoring and assessment protocols for urban and urbanizing watersheds, with the aim to better support planning of stream restoration projects and improve restoration outcomes. This is the product of a joint task committee by the Urban Stream Committee of the Urban Water Resources Research Council and the River Restoration Committee of the Hydraulics and Waterways Council.