The Gulf of Maine is an international watershed in the North Atlantic stretching north from Provincetown at the tip of Massachusetts Bay in the Commonwealth of Massachusetts to Cape Sable on the Bay of Fundy in the province of Nova Scotia in Canada. For over 13,000 years, the Gulf has been developed around access to the coast for fishing, trading, and recreation. Today, these coastal development patterns put the cultural landscapes, economies, communities, and aging infrastructure systems along the Gulf at risk.
Climate Futures on the Gulf of Maine uses place-based scenario planning to illustrate the risks, vulnerabilities, and plausible futures for ten infrastructure systems along the rim of the Gulf. Place-based scenario planning is a method of long-term strategic planning that creates representations of multiple, plausible futures that are used to inform decision-making in the present. While complementary to probabilistic models used to forecast future vulnerabilities, scenario-based planning shifts emphasis from statistical probability to ways of thinking about the future. The goal of place-based scenario planning is not to predict the most likely outcome, but to reveal biases and blind spots in complex and non-linear situations.
Climate Futures uses the medium of landscape representation to surface the cultural value systems embedded in existing infrastructural systems, and position landscape as a driver when evaluating design from individual infrastructures to the Gulf of Maine watershed.
Infrastructure > Road
US-ROUTE 1 DIKE BRIDGE #2246
Main Street over Middle River Reservoir
Machias, ME 04654
The Machias Dike Bridge carries United States Route 1 (US-Route 1), the primary north-south highway in the region, over the Middle River in the Town of Machias, Maine on the unceded land of the Passamaquoddy Tribe. 1 The dike and four tidal gates limit the flow of the Machias River into the brackish Middle River. 2
Bridge #2246 consists of four box culverts within a causeway that was originally constructed out of timber and earthen fill in 1868 by the Town of Machias. 3 The construction of the dike blocked tidal flow and fish passage from the Machias River into the Middle River, both of which are considered essential fish habitat 4 for marine and estuarine species, including Atlantic salmon (Salmo salar), Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus), and shortnose sturgeon (Acipenser brevirostrum). 5
The bridge was enlarged in the 1890s to support the Washington County Railroad, and widened in 1930 and 1944, when tidal gates were added over four box culverts under the structure. 6 From 2008 to 2018, the Maine Department of Transportation performed piecemeal repairs, including reinforcing and repaving the road and replacing broken tidal flaps. 7 8 Beginning in 2009, a series of public meetings were held and studies conducted to determine an appropriate solution to the aging infrastructure problem. 9
These discussions are ongoing, with several alternative options proposed by the Maine Department of Transportation and National Marine Fisheries Service. 10 These include a bridge with open culverts, an in-kind replacement, and a pile-supported span bridge that would allow for full tidal transparency. 11
While restoring tidal flow with open culverts or a bridge would allow for fish passage and restore salt marsh habitat upstream of the dike, the fluctuation in water level may flood residences, businesses, and a capped municipal landfill upstream of the bridge. 12 The bridge project also requires coordination with recent resiliency efforts by the Town of Machias to protect the Downtown Machias waterfront from increasing coastal flooding. 13 14
Bridge #2466 is located adjacent to the downtown area, and is the main transportation corridor connecting the waterfront area to East Machias and northern Towns in Washington County. During emergencies, the bridge is critical for fire, rescue, and emergency response teams. Today, the bridge and large portions of the Downtown area are located within the Federal Emergency Management Agency (FEMA) AE Flood Zone, at risk of flooding during a 100-year storm. 15 This area includes another piece of critical infrastructure: the Town’s Wastewater Treatment Plant. 16
In 2024, the Maine Department of Transportation publicly announced a plan to install a temporary bridge over the existing Dike Bridge with an expected lifespan of 15-20 years, giving the Town, State, and federal agencies additional time to consider the future of the dike bridge and its adjacencies. 17 The uncertainty around the deferred timeline, interagency cooperation, and phasing regarding the future not only of Bridge #2466, but also the Downtown Machias waterfront, provide an opportunity to re-evaluate the future of the causeway and dike built across the Machias and Middle Rivers, and consider potential future scenarios, including a coordinated coastal armoring system, or restoration of the coastal ecosystem and essential fish habitat.
Scenario 0: Storm of the Century 2030
The temporary bridge over the Machias and Middle Rivers collapses when storm surge rushes up the Machias River, damages the tidal gates, and washes out the causeway. Recovery efforts are overwhelmed by flooding throughout Downtown Machias, including at the nearby wastewater treatment plant.
Scenario 1: Fortified Systems
A pile-supported span bridge is installed across the reconnected Machias and Middle Rivers. US-Route 1 shares the bridge with the Sunrise Trail and a protected pedestrian walkway. Beneath the bridge, tidal flow and fish passage are restored. The project is completed in tandem with an armoring project around downtown Machias that installs revetments and seawalls around the wastewater treatment plant, residences, and businesses.
Scenario 2: Catchment Commons
The existing dike and culverts are removed and traffic is rerouted south to Route 92 from Machiasport to East Machias. A reinforced timber boardwalk is installed across the rivers, restoring tidal flow. A living shoreline is installed around downtown Machias as part of a comprehensive adaptation plan for which the wastewater treatment plant is relocated and business and residences are elevated.
International Watershed | Gulf of Maine | Hydrologic Unit Code |
Region (HUC-2) | New England | HUC 01 |
Subregion (HUC-4) | Maine Coastal | HUC 0105 |
Basin (HUC-6) | Maine Coastal | HUC 010500 |
Subbasin (HUC-8) | Maine Coastal | HUC 01050002 |
Watershed (HUC-10) | Lower Machias River | HUC 0105000206 |
Subwatershed (HUC-12) | Outlet Machias River | HUC 010500020604 |
See “Passamaquoddy History,” Passamaquoddy People, www.passamaquoddypeople.com/passamaquoddy-history, accessed February 25, 2025.
The tidal gates installed on the culverts have changed the hydrology between the Middle and Machias Rivers, resulting in reduced water quality, reduced pH, and changes in the salt marsh upstream of the bridge. See Ian Gorecki, “Machias, Bridge #2246, U.S. Route 1,” Public and Agency Information Document (Augusta, ME: Maine Department of Transportation, November 2024): Appendix 1-46.
The 1000’ causeway structure is constructed of timber cribbing with rubble and earthen fill. The 130’ long, 6’ wide and 5’ high culverts are constructed of timber and stone masonry. Ian Gorecki, “Machias, Bridge #2246, U.S. Route 1,” Public and Agency Information Document (Augusta, ME: Maine Department of Transportation, November 2024): Appendix 1-1.
NOAA Fisheries defines essential fish habitat (EFH) as “essentially, fish habitat.” EFH “includes all types of aquatic habitat for fish spawn, breed, feed, or grow to maturity.” See “Essential Fish Habitat,” NOAA Fisheries, www.fisheries.noaa.gov/national/habitat-conservation/essential-fish-habitat, accessed May 26, 2025.
The Machias River is one of eleven rivers in Maine that support naturally spawning Atlantic salmon with historic river-specific characteristics. Ian Gorecki, “Machias, Bridge #2246, U.S. Route 1,” Public and Agency Information Document (Augusta, ME: Maine Department of Transportation, November 2024): 15-19.
Ian Gorecki, “Machias, Bridge #2246, U.S. Route 1,” Public and Agency Information Document (Augusta, ME: Maine Department of Transportation, November 2024): 5.
Ian Gorecki, “Machias, Bridge #2246, U.S. Route 1,” Public and Agency Information Document (Augusta, ME: Maine Department of Transportation, November 2024): 5.
There was no single storm event that damaged the dike bridge. Instead, the bridge has been damaged for years, and increasingly stressed by flooding events, especially those during high tides. Across northern Maine, warming spring temperatures melt snowpack more quickly than watersheds can handle, causing water bodies like rivers and streams to overflow and flood low-lying roads. See Washington County Emergency Management Agency, “Washington County Hazard Mitigation Plan – 2018 Update” (Machias, ME: Washington County Emergency Management Agency, 2018): 4-21.
The Maine Department of Transportation has compiled a Public and Agency Information Document and online Story Map documenting the Dike Bridge Project. See Maine Department of Transportation, “Machias, Route 1, Dike Bridge,” ArcGIS Story Map, November 2024, storymaps.arcgis.com/stories/b399dfadf78c46bdb36c83d2abc2f4b6.
The Maine Department of Transportation published a matrix of alternative options from three studies in 2015, 2019, and 2020-2023. Each study uses an Existing Condition/No Action Alternative to compare options against. See Ian Gorecki, “Machias, Bridge #2246, U.S. Route 1,” Public and Agency Information Document (Augusta, ME: Maine Department of Transportation, November 2024): Appendix 2 Alternatives Matrix.
The National Marine Fisheries Service strongly prefers the pile-supported span bridge. At 13.1 ft (NAVD88) the top of the proposed dike bridge would offer 5.7 feet of freeboard above the current mean higher-high tide water line (7.44 ft) during the highest average tides in Machias. See Michael Johnson, “Climate Change Case Study: Machias Dike Bridge Project.”
Ian Gorecki, “Machias, Bridge #2246, U.S. Route 1,” Public and Agency Information Document (Augusta, ME: Maine Department of Transportation, November 2024): Appendix B Inundation Figures.
The coastline around Downtown Machias has been altered for fishing, logging, and ship-building since colonization. The dike bridge is just one example of the way humans have armored the coast and changed the hydrology and habitats here. See Baker Design Consultants, “Town of Machias, Maine Waterfront Resilience Study” (Machias, Maine: Town of Machias, 2019).
A preliminary study of a seawall and levee system for the downtown area proposes raising US-Route 1 and the boat ramp to 15 ft (NAVD88). Baker Design Consultants, “Town of Machias, Maine Waterfront Resilience Study” (Machias, Maine: Town of Machias, 2019): 8.
The Base Flood Elevation (BFE) that FEMA determined is 10.7 ft. The FEMA AE Flood Zone notes areas that have a 1-percent change of being inundated by a flood event in any given year. The 1-percent annual chance flood is also referred to as the 100-year flood. See “Glossary,” Federal Emergency Management Agency, www.fema.gov/about/glossary.
Baker Design Consultants, “Town of Machias, Maine Waterfront Resilience Study” (Machias, Maine: Town of Machias, 2019): 11.
Bruce A Van Note to Machias Board of Selectmen, “Re: Dike Bridge, Route 1, Machias, Maine,” November 26, 2024, https://uploads.mainedotpima.com/4f6ae40b-53fe-4318-8c5a-7ccc9ce57f32.pdf.
