Oyster River Watershed Culvert Study
As a pilot project of the Climate Ready Estuaries Program, this study addresses climate adaptation on a watershed scale and provides a methodology for other coastal watersheds seeking to incorporate future climate conditions in planning and development. In 2008, the Piscataqua Region Estuaries Partnership (PREP) received a grant to conduct an inventory and assessment of climate change impacts on road and stream networks in the Oyster River watershed. The team has identified specific culverts that are likely to fail under projected precipitation pattern changes associated with climate change, and created a strategy with specific recommendations to help reduce habitat degradation, infrastructure damage, and public safety risks from flooding.
This is a pilot project of the Climate Ready Estuaries Program to identify and assess potentially vulnerable road culverts in the Oyster River Watershed. Many culverts are vulnerable to failure from flooding during the increasingly extreme storm events that are expected with climate change. PREP is working with partners to assess culverts in the watershed, model changes in stormwater runoff expected from extreme coastal storms, and develop recommendations for culvert improvements in the Oyster River Watershed and other coastal communities.
This project originated because of concerns over cumulative effects of changes in precipitation and storm events as a result of climate change and typical habitat alterations like the development of roads, roofs, parking lots, and other impervious surfaces. Flooding related to undersized culverts as a result of highly destructive storm events in 2006 and 2007 generated public awareness and concern over increasing storm intensity and potential vulnerabilities of present infrastructure. Current road culverts in New England roads are vulnerable to failure, which will result in increased runoff and potential for flooding leading to damage to property and infrastructure, habitat degradation, and public health risks.
The overall purpose of this project is to develop an adaptation strategy to reduce climate change impacts on habitat and structure. The PREP initiated an effort to inventory and assess the capacity of culverts to withstand the effects of flooding based on current and projected precipitation patterns.
In 2008, the PREP applied for and received a grant from the U.S. Environmental Protection Agency’s Climate Ready Estuaries Program to conduct a vulnerability assessment of climate change impacts on existing road and stream networks in the Oyster River watershed. The primary project partner is the EPA; PREP also is working with the Town of Durham (New Hampshire), New Hampshire Fish and Game Department, and the Strafford Regional Planning Commission.
The PREP assessed and mapped over 100 culverts, and collected and incorporated data on culvert capacity, slope, land use, and more into a GIS model to calculate runoff volumes based on current and projected precipitation scenarios. The model also evaluated two land use scenarios – one assuming current development patterns and the second demonstrating low impact development techniques. Using these results, the project team is developing recommendations for culvert improvements based on risk analysis and cost estimates; these results demonstrate how climate change is expected to affect community infrastructure and safety and will provide a strategy useful for application in coastal watershed communities in the Oyster River watershed and beyond. The project has real economic consequences for towns to consider in improving culverts and general road infrastructure, especially in the face of likely climate change effects. The project team is working to expand its outreach efforts and disseminate their results to include and inform decision makers from the towns of Durham, Madbury, Dover, Lee, and Barrington.
Outcomes and Conclusions
Using the results of the inventory and assessment of current culvert capacity in the Oyster River watershed, the PREP study team plans to engage in more outreach to local towns and to create a finalized, written narrative and adaptation strategy that can be applied to different coastal watersheds around the country. In addition, the team hopes to coordinate with state policy efforts in New Hampshire and Maine. This project is still in progress with plans to continue into the future. In addition, the PREP is in the process of rewriting its Comprehensive Conservation and Management Plan; there are plans to write climate change into the plan as an overarching theme with both adaptation and mitigation strategies included.
Gregg, R. M. (2010). Oyster River Watershed Culvert Study [Case study on a project of the Piscataqua Region Estuaries Partnership]. Product of EcoAdapt's State of Adaptation Program. Retrieved from CAKE: http://www.cakex.org/case-studies/oyster-river-watershed-culvert-study (Last updated January 2010)