Pacific Southwest Research Station

Tools to quantify urban stormwater load reduction from SEZ restoration actions

Proposal [pdf]

Abstract

This research will generate recommended methods to estimate: 1) pollutant load reductions expected from stream restoration projects, 2) load reduction benefits associated with the interception of urban stormwater outfalls to stream environment zones (SEZs) and 3) additional load reduction benefits if a degraded intercepting SEZ is restored. The methods will include necessary site-specific data collection and reporting metrics to document pre- and post-restoration physical and geomorphic characteristics of a specific stream or SEZ. Collectively, these estimates will support a load reduction opportunity analysis of the feasible pollutant load reductions achievable via functional stream and SEZ restoration actions in the Tahoe Basin. Researchers will build upon and extend current monitoring of the Trout Creek site and evaluate additional SEZ sites. Analysis will be conducted by integrating outputs derived from a spatially explicit USGS modeling platform (SPARROW), the Pollutant Load Reduction Model (nhc et al. 2009) and the Stream Load Reduction Tool (2NDNATURE 2010). SPARROW will be employed for the Tahoe Basin, calibrated and validated using the wide array of existing land use, hydrologic and water quality data from a selection of watersheds. The estimation methods will be validated to the extent possible on site‐specific stream and SEZ test sites, and used to inform a methodology to provide researchers and stormwater engineers with a consistent and relatively accurate method to estimate the pollutant load reductions from specific SEZ improvement projects. Available research will be analyzed to evaluate the feasibility and validity of approximating the urban derived pollutant loading to the upstream boundary of a stream restoration project, as well as the urban pollutant fraction retained. This research builds on existing models, datasets and past and ongoing SNPLMA‐funded efforts by the 2NDNATURE team, leverages existing datasets, methods and models in a manner consistent with the TMDL Pollutant Reduction Opportunity analysis (Lahontan Regional Water Quality Control Board [LRWQCB] and Nevada Division of Environmental Protection [NDEP] 2008), and is directly applicable to the Lake Clarity Crediting Program (LRWQCB and NDEP 2009).

Relation to Other Research Including SNPLMA Science Projects

This research will significantly leverage and utilize a wide array of existing datasets and will inform and/or build upon the following SNPLMA projects: 1) "Reductions in sediment loads due to stream restoration" (Round 7), 2) "Potential of floodplains to retain fine sediments" (Round 8), 3) "Measuring the ability of floodplains to treat urban runoff" (Round 9), and 4) "Priority urban stormwater monitoring to directly inform the Pollutant Load Reduction Model (PLRM)" (Round 9). The Stream Load Reduction Tool (SLRT) development, implementation and analysis funded by SNPLMA Round 9 ("Quantification and characterization of Trout Creek restoration effectiveness"). SLRT estimates the expected difference in pollutant loading pre‐ and post‐restoration actions based on changes to specific attributes of geomorphic form and floodplain characteristics that are key to achieving volume and pollutant retention. This new research will apply and scale these physical and geomorphic concepts to develop a methodology to estimate the load reductions achieved by routing an urban drainage outfall to an intercepting SEZ while preserving the geomorphic concepts applicable to smaller sized SEZ systems.