2NDNATURE is applying our extensive urban hydrology and pollutant modelling expertise to create a simple and repeatable tool for stormwater managers to estimate urban catchment load reductions. Pollutant load reduction estimates are a Phase II MS4 permit requirement, yet the majority of urban hydrology models require advanced modelling knowledge to adequately represent an urban catchment and properly parametrize the model. We interpret the intent of these permit requirements is to ensure municipalities have a process to justify and annually communicate; 1. The water quality benefits to receiving waters as a result of their stormwater program and 2. Current water quality improvement priorities to continue to reduce pollutant loading to receiving waters in the future. 2NDNATURE modeling experts and statisticians have create a focused and simplified urban hydrology model that generated average annual urban catchment volumes that are consistently within 5% of the EPA SWMM results. By focusing the algorithms and user inputs on the effectiveness of structural and programmatic BMPs installed, implemented and maintained, TELR is a streamlined yet technically defensible platform that can be easily used by stormwater managers to inform decisions and meet MS4 permit requirements. The customized online data management platform ready for any Phase II MS4 will be available in mid 2016.
A typical goal of riparian restoration efforts is to improve water quality, yet our ability to quantify this benefit is costly, requires years of pre and post restoration monitoring, and is challenged to separate hydrologic variability from the signal of the restoration. Informed by years of pollutant fate and transport monitoring in fluvial systems, 2NDNATURE developed a simple yet standardized empirically based methodology to estimate the average annual fine sediment load reductions as a result of stream restoration actions. The Stream Load Reduction Tool (SLRT) is a customized MS Excel spreadsheet tool that automates average annual hydrologic inputs, estimates load reductions and provides supporting graphics based on a series of geomorphic inputs by the user. SLRT uses a simple mass balance approach to quantify the amount of fine sediment delivered to and retained on the floodplain and the amount of fine sediment generated from bank erosion for both the pre and post restoration geometry. 2NDNATURE then applied SLRT to a series of completed and planned stream restoration projects in the Upper Truckee River Watershed indicating a range of potential water quality benefits from different projects. Comparisons of the mass of fine sediment per US$ reduced provided valuable insight to restoration practitioners on how to evaluate completed projects and optimize designs for planned projects where water quality improvement is a priority. 2NDNATURE’s work on SLRT has helped to demonstrate that SEZ restoration is a valid way to achieve sustained pollutant load reductions to Lake Tahoe. The customized MS Excel templates and user guidance can be obtained at the links below.
The Pollutant Load Reduction Model (PLRM) is the accepted load estimation tool supporting the Lake Clarity Crediting Program and is the critical method used by the jurisdictions and the regulators to define pollutant load reduction targets and credit allocations for water quality improvements. PLRM is a user friendly platform that runs the EPA’s Storm Water Management Model (SWMM) continuous urban hydrology and a customized water quality model to estimate average annual pollutant load reductions. 2NDNATURE continues to collaborate with NHC to develop, refine and optimize the water quality module of the PLRM though both calibration and validation efforts, in addition to a series of functional user and input validation improvements.
2NDNATURE developed a simple hydrologic routing estimation tool to quantify parcel-scale load reduction benefits from low impact development. LRPT integrates both volume and pollutant load reductions expected as a result of treating (i.e., capturing and infiltrating) runoff from impervious surfaces via infiltration features. With the TRPA requirement that all land owners implement parcel scale BMPs to retain the 20yr 1hr storm onsite, LRPT provides a simple and standardized method to evaluate various site scale design improvements to optimize water quality benefits. LRPT also provides standardized quantification of the average annual volume and fine sediment load reductions as a result of the modeled parcel scale improvements. The custom MS Excel templates and user guide can be obtained at the link below.
Culverts used to construct road crossings over streams, if improperly constructed, can be a significant source of sediment to local streams. Road improvement programs throughout California provide technical and financial support to improve road stream crossings to reduce the risk of clogging, diversion, erosion and failure. Prior to replacement, field personnel commonly quantify the volume of sediment contained within the stream crossing/road prism to: (1) quantify and prioritize improvements based on the amount of sediment avoided if the crossing is improved and (2) provide critical design information for contractors to properly estimate the cost of the improvement actions. In partnership with the Napa RCD, 2NDNATURE developed the Road Fill Prism Calculator (RFP-Calc) to simply calculate the sediment volume of a culverted stream using the field assessment approach defined by the Department of Fish and Wildlife Salmonid Habitat Restoration Manual. The interface allows the user to enter the site survey data directly, from which the RFP–Calc automates the volume calculations, generates graphical site cross sections and longitudinal profiles, and summarizes key parameters necessary to inform the proper site improvement design. The user can also quantify the volumes desired for excavation and stream crossing culvert replacement by adjusting profile depths at multiple points and cutback slope angles at each cross section. The current version is an MS Excel customized spreadsheet, but the desired future version is a web-based platform available to authorized users that can simplify data management of both the temporal and spatial inventory of completed assessments.