The Challenge
This project will address climate change by providing restoration practitioners and infrastructure designers with tools that can be used to plan and design structures within transitional zones that are anticipated to be affected by sea level rise, and that have the potential to enhance flood (storm and coastal) resiliency, upstream flood storage capacity, utilize best practices to prepare for and reduce coastal erosion and scour, and mitigate resource impacts where coastal transportation corridors are critical for health and human safety. The potential climate impacts identified in the 2023 ResilientMass Plan addressed by this action include:
- Human Sector
- Loss of life or injury due to high vulnerability dams, hurricanes, wildfires, extreme flooding, or extreme temperatures
- Infrastructure Sector
- Damage to Coastal Buildings and Ports
- Natural Environment Sector
- Coastal Wetland Degradation
- Loss of biodiversity, habitats, and native species due to climate change impacts
- Governance Sector
- Damage to Coastal State and Municipal Buildings and Land
- Damage to Roads and Loss of Road Service
Project Alignment with ResilientMass Plan Priority Actions
This project is directly related to DER ResilientMass Plan Action “Transitional Crossings: Testing standards for evaluation, feasibility and design of culverts and bridges that will experience the impacts of sea level rise in the next 50 to 75 years”.
Climate Resilience Project Scope
Previously, under Phase I (FY21/22), DER developed draft climate resilience guidance for stream crossings in coastal and near-coastal environments. The goals for Phase 2 for FY25 involved revising guidance by incorporating case studies of real-world transitional crossing sites into the guidance while simultaneously advancing preliminary designs.
DER worked with a competitively selected engineering firm to complete documenting the site assessment processes, obtaining site-specific model data, developing preliminary designs for two competitively selected “transitional” culvert sites, located in Gloucester and West Newbury. The municipal transitional crossings were selected based on criteria focusing on location within the transitional zone, environmental impact as well as proximity to Environmental Justice communities. In conjunction with feedback from a Technical Advisory Committee, technical guidance for stream crossings in transition was revised.
This work provides technical guidance to assist municipalities along with restoration practitioners in the planning and design of stream and channel crossings that are anticipated to experience the increased influence of tidal conditions and sea level rise, as climate change impacts site conditions over the lifespan of new crossings in the next 75 – 100 years. Further, this work advances real-world examples of transitional crossings and prepares the selected sites to seek further assistance and support from programs such as the MVP Program and other funding opportunities.
Metrics and Results
The number of applications DER received from municipalities seeking to have their site selected, is an indicator of the level of interest from communities in advancing the planning and design of crossings anticipated to experience sea level rise and potential marsh migration. Eight communities proposed a total of 10 sites, and two were selected (Gloucester and West Newbury). Preliminary designs were developed for the two awarded communities.
Best Practices and Lessons Learned
During FY25, coordination with the Technical Advisory Committee (TAC) identified the need to review and consider relevant overlapping guidance and avoid contradiction with Federal Highway guidance and standards in the Hydraulic Engineering Circular No. 25 / Highways in the Coastal Environment, 3rd Edition.
Further Action
DER plans to continue to advance this project, developing the initial preliminary designs further from conceptual to pre-permitting, to understand if additional guidance may be helpful to develop relative to the alternatives analysis and public outreach phases of early planning and design. This will also build the culvert replacement pipeline and expand opportunities to also address marsh migration corridors. DER also plans to develop a coordination pathway with MassDOT to review Federal Highway guidance and revise transitional crossing guidance for consistency.