Ninety percent of the bridges and culverts on the roads in Maine that cross salt marshes and tidal waterways are not equipped to handle the ebb and flow of the tides.
That means higher road maintenance costs along the state's scenic coast, along with a shortened lifespan for culverts and bridges, unplanned road closures that can put public well-being and safety at risk, and harm to commercial fisheries and important habitat.
As a result, the Department of Marine Resources' (DMR) Maine Coastal Program, along with 30 other organizations, has published a 100-page manual offering technical guidance on how to increase the safety of road crossings over Maine's coastal wetlands and waterways.
"The CoastWise Approach: Achieving Ecological Resilience and Climate-Ready Road Crossings in Tidal Environments" is designed to be a resource for municipal and private engineers, public works directors, land developers, landscape architects and habitat restoration practitioners, said Maine Coastal Program Director Kathleen Leyden.
The publication also may be of use to general audiences and those working to build community awareness, including local elected officials, neighborhood associations, conservation commissions, land trusts and the public, she added.
The manual provides information about tidal wetlands and the factors that are changing them.
"Safe, dependable roads are crucial for supporting Maine's economy, access to critical services, and a way of life valued by citizens and visitors alike," Leyden said. "The severity of today's tidal restrictions is likely to worsen as sea levels rise and the volume of water flows increases over the coming decades."
Among the other entities that worked to develop "The CoastWise Approach," a free publication, were the Maine Department of Transportation, Maine Audubon, the University of Maine, The Nature Conservancy, the Federal Highway Administration and the U.S. Army Corp of Engineers.
Additionally, several Maine towns contributed by participating in community surveys: Arrowsic, Blue Hill, Bremen, Cape Elizabeth, Damariscotta, Kennebunkport, Surry, Yarmouth and York.
Keeping Reliable Roads Across Wetlands a Challenge
Maintaining well-built roadways has become a challenge for most communities in the state, especially in coastal areas experiencing rapid change due to accelerated sea level rise, Maine DMR noted.
Where roads cross tidal wetlands at more than 800 locations in Maine, those challenges are magnified considerably, according to the new manual.
Tidal wetlands are essential to the state due to their ability to provide coastal storm and flood damage protection, pollutant filtration and breakdown, habitat for fish and wildlife, and opportunities for robust commercial harvesting and recreational activity for humans.
Maine DMR said that some wetlands, like salt marshes, also store atmospheric carbon that would otherwise contribute to sea level rise and other climate shifts.
To deliver those benefits, tidal wetlands must remain healthy and resilient to sea level rise. That requires unimpaired tidal flow.
But about 90 percent of Maine's tidal road crossings are tidal restrictions. Such crossings put the state's tidal wetlands at risk, but are also more apt to experience flooding, incur higher maintenance costs, and interrupt access to emergency services.
Tidal Complexities Abound
Traditional practices for designing tidal road crossings do not adequately address the unique complexities, uncertainties, risks, or benefits associated with tidal environments, according to the state's DMR.
In response, the Maine Coastal Program and the CoastWise Steering Committee convened experts in the field and marshaled the input of more than two dozen organizations to develop the new CoastWise manual, which discusses tidal wetlands as dynamic systems influenced by a wide range of interacting social and environmental factors requiring a design approach that addresses complexity and risk, both now and in the future.
The free publication offers best practices to help road owners, municipal staff, engineers and others in helping to replace tidal road culverts and bridges with safe, climate-resilient crossings, Leyden said.
Partners involved in the project are currently developing training modules, which are anticipated to be unveiled in 2024. To view the manual, visit www.maine.gov/dmr/programs/maine-coastal-program/coastal-community-support/the-coastwise-approach.
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