New Englanders may only think about culverts when they fail. Often, we don’t know a road even has a culvert until it has collapsed or is dammed with sediment, causing flooding.
What may be less obvious is that culverts can protect against storm surge and tidal flooding, especially as sea levels rise.
Massachusetts is piloting an initiative to help municipalities think about how to replace or upgrade culverts and other infrastructure with resilience in mind. The Massachusetts Department of Fish & Game’s Division of Ecological Restoration is working with two municipalities to plan how to replace two culverts under roads near the ocean, with the goal of making the culverts, and the municipalities, more resilient to projected sea level rise and storm surge.
The culverts in Gloucester and West Newbury currently connect freshwater waterways, but these waterways will likely be increasingly impacted by saltwater intrusion in the future. Such saltwater intrusions may be hard to see on the ground, but aerial photos show the saltwater may already be infiltrating upstream, where a band of dead trees ring the periphery of the marshy areas, said Georgeann Keer, the Division of Ecological Restoration’s wetland restoration program manager.
The National Park Service estimates that coastal marshes provide nursery habitat for some 75 percent of commercially fished species.
“Sometimes when you look at photos, particularly in the summer growing months where you see that gray edge, that platform of dead trees, it’s typically called ghost forest,” Keer said.
Coastal environments change over time, but they can change rapidly if culverts fail. Saltwater intrusion brings a different set of dynamics for culverts, bringing tidal flooding and increased sediment flow that can dam up the culvert, which can trap saltwater storm surge upstream. If a culvert system isn’t built to handle these surges, flooding can occur very quickly and have an impact on the ecosystem that can last for years.
“The negative impacts can be a sudden acute situation rather than a chronic [one],” Kerr said.
Unmanaged tidal flooding could impact nearby homes, wash out roads, and damage commercial fisheries. The National Park Service estimates that coastal marshes provide nursery habitat for some 75 percent of commercially fished species.
Municipalities have learned the art of planning ahead to replace aging infrastructure, but planning ahead for rapidly changing storm surges and rising sea-level rise is more complicated. Effective planning to make infrastructure more resilient to these changing conditions takes coordination and forethought among many stakeholders, including state agencies, municipalities, and abutting landowners.
DER is providing expertise and resources to help Gloucester and West Newbury think of the steps needed to complete the culvert replacement projects.
“Our understanding and our concerns have shifted from not just focusing on the existing conditions and coastal systems, to what the future will hold for these environments and these systems and the infrastructure that’s around them,” Kerr said. “How do we now build this into our thinking and planning about projects as the goalpost is literally shifting beneath us?”
DER is just one of many state agencies which are working to help Massachusetts communities become more resilient to rapid ecological change. The hope is that the processes these two communities undertake will be instructive for other communities facing similar challenges.
Similar efforts are being undertaken throughout New England, and there is growing interest to work together to help critical coastal infrastructure be future ready, said Robert Van Riper, a tidal habitat restoration coordinator with the Maine Department of Marine Resources.
Van Riper has helped form a group of regional stakeholders who regularly share ideas about climate change and infrastructure in New England. In his opinion, these efforts in Maine lag behind those in Massachusetts, and that’s largely because smaller Maine municipalities have fewer financial resources for them. Another hurdle is red tape, as infrastructure changes require a more rigorous permitting process than wetland restoration.
Parker Gassett, the Marine and Coastal Communities Specialist with UMaine Cooperative Extension, said the key to help cash-strapped municipalities invest in such processes to make their infrastructure future-ready may be in centering such efforts in economic pragmatism.
“The cost of culvert replacement and of replacing gravel washed away in heavy rainfall is one of the first serious exposures that Mainers have to climate change,” Gassett said. “Budgeting for those costs in advance… is a good way to start thinking about long-term community investment in storm resilience.”
