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https://www.nationalacademies.org/trb/events

Quantifying the Flood Resilience Value of Water Quality Best Management Practices on Vermont Roads

Transportation networks have been recognized as contributors to water quality impairment by discharging stormwater, sediment, and nutrients to receiving waters. These contributions can occur through chronic inputs of water and pollutants washed from the road surface during storm events or through episodic and often catastrophic road failure by mass wasting or fluvial erosion at structure crossings during extreme storms. Research studies in forested areas of the eastern United States, and elsewhere, including those conducted by members of this project team, have documented rates of erosion and mass wasting from low volume roads and impacts on water quality. Our previous research has also documented the importance of unpaved roads on water quality impairment and quantified the effectiveness of best management practices (BMPs) in reducing sediment and phosphorus contributions. The Phosphorus Total Maximum Daily Load for Vermont Segments of Lake Champlain (a.k.a. TMDL) called for reductions in phosphorus contributions from developed lands, motivating a need to address stormwater runoff from the state’s transportation network. Statewide efforts to achieve the reductions required by the TMDL led to the development of the Municipal Roads General Permit (MRGP) in 2018 and subsequent revisions. Recent extreme flooding events across the state, in particular the July 10-11, 2023 North Country Storm event and associated Great Vermont Flood which will be the focus of this project, in addition to subsequent flood events in December 2023 and July 2024, have resulted in the need for emergency repairs of damaged transportation infrastructure, and revealed the need to clearly communicate the cost benefit of improved stormwater management on the transportation network. In past research projects funded by the Vermont Department of Environmental Conservation and the Vermont Agency of Transportation, we conducted retrospective analyses (i.e. a review of project planning documents and site visits to assess existing conditions) of transportation stormwater upgrades funded by the state’s Better Roads and Grants in Aid programs and found that the BMPs installed through these grants were highly robust to extreme flood events. This project therefore aims to expand on the research teams’ prior work to assess the life cycle cost-benefit of BMP adoption with a focus on the BMPs required by the Municipal General Roads Permit (MRGP), Sections 1 and 2 of the VT Road and Bridge Standards for municipal roads, and VTrans Drainage Management Standards for State roads. The data and results of this project may be used to update VT AOT’s Transportation Resilience Planning Tool or other mitigation practices. To facilitate this work, we will form a technical advisory committee (TAC) composed of VTrans project champions (Todd Eaton), Vermont Department of Environmental Conservation (VT DEC) staff engaged in the implementation of the Municipal Roads General Permit, members of at least one Regional Planning Commission, and others identified by VTtrans. The role of the TAC will be to help guide study design, facilitate the use of existing data, leverage on-going implementation of erosion control projects, and provide context for agency needs.