Coastal bluff erosion encroaches on a house on Long Island, a member of the Greater Portland Council of Governments. Contributed / GPCOG

The Greater Portland Council of Governments is implementing an initiative to help Casco Bay communities threatened by coastal erosion.

Over the next two years, the council will work with project partners on educating municipalities on coastal bluff erosion, designing erosion mitigation plans and coastal bluff mapping. A bluff is a steep shoreline slope formed in sediment (loose material such as clay, sand and gravel) that has 3 feet or more of vertical elevation just above the high tide line, according to the Maine Geological Survey.

The project received a $350,000 grant through the National Fish and Wildlife Foundation’s Coastal Resilience Fund.

The initiative began as part of the larger project Climate Ready Casco Bay, which began in 2022 and received funding from the fund to examine environmental vulnerabilities in communities in Casco Bay. Through this process, it became apparent to the Council of Governments that coastal bluff erosion was a pressing issue in the Greater Portland region, threatening private property, public infrastructure and vulnerable ecosystems.

“Things that could potentially accelerate erosion: sea-level rise, increased storm intensity, variable changing temperature in the winter – so your frost and thaw cycles can accelerate erosion, as well,” said Gretchen Anderson, the council’s sustainability program coordinator. “It’s all the heavy hitters, if you will, of climate change that will impact this problem.”

The council comprises 30 cities and towns in Cumberland and York counties, not all of which have coastal bluffs. The organization has identified Brunswick, Freeport and small areas between Falmouth and Portland as having coastal bluffs facing erosion in need of mitigation. Casco Bay islands including Long Island, Chebeague Island and Great Diamond Island of Portland are experiencing coastal erosion by the surrounding waves.

“We want to make sure we’re sort of casting a wide net to understand what the impact could be across the whole region,” said Sara Mills-Knapp, the council’s director of sustainability.

Erodible coastal bluffs make up 40% of Maine’s coastline, and at least one-third of coastal bluffs are eroding at some rate, according to the Maine Geological Survey. The Greater Portland Council of Governments will assist municipalities with adopting ordinance language that allows “nature-based” solutions to erosion.

An eroding coastal bluff on Great Diamond Island in Casco Bay. Contributed / GPCOG

“Nature-based” mitigation refers to techniques that use organic materials to slow erosion such as planting a living shoreline, placing felled trees and promoting the development of flatlands to absorb wave impact. This approach promotes healthy coastal habitats and is an alternative to hard infrastructure that armors the shore with riprap or rocks. Armoring often just diverts wave action to adjacent areas that then erode.

Regulatory language that may allow for hard infrastructure solutions does not always apply to nature-based mitigation techniques and can be a barrier to their implementation, Mills-Knapp said.

The council also will identify three high-priority communities in Casco Bay for which it will specifically design nature-based shoreline protection plans. Those municipalities will then seek additional funding to implement the developed plan.

“If they’re having some sustained erosion and slough loss to a public parcel that’s an economic driver or benefit to the town or municipality, (we will) see how we could help facilitate design,” Anderson said.

“If we can help with that initial design process, hopefully we could potentially facilitate funding afterwards,” she said. “It’s really hard to get funding without a plan.”

Installing nature-based erosion mitigation is not yet widespread in Maine, though it has gained popularity in similar shorelines in Massachusetts, Anderson said. She said the council hopes this program will increase implementation of nature-based solutions to erosion on Maine coasts.

For the data-gathering aspect of the initiative, the Maine Geological Survey will update maps of coastal bluffs using advanced techniques including drone imagery. Updated information on coastal bluffs in Casco Bay lead to better management and ecosystem protection, according to a news release from the council, which also emphasized the importance of these ecosystems for Maine’s growing aquaculture industry.

“The sediment supply from natural erosion of coastal bluffs is vital to the survivability of many adjacent protected resources like beaches, dunes, mudflats and coastal wetlands, so proper management of bluffs is integral to the overall health of many ecosystems in Casco Bay,” Peter Slovinsky, a coastal geologist with the Maine Geological Survey, said in the news release.

The Cumberland County Soil and Water Conservation District will partner with the Greater Portland Council of Governments to help educate municipal staff, community members and environmental contractors about planning for coastal erosion and the benefits of nature-based solutions.

“You’re also dealing with climate change and sea-level rise, not just erosion coming from the land and issues there, but you’re also being hit with water levels and such,” said Heather Hunt, the Cumberland County Soil and Water Conservation District project manager.

“This is a special grant fund with climate resiliency in mind, and we like to see projects that actually end up being implemented on the ground, so that they’re not just concepts,” she said.