A Tale of 25,000 Culverts
Restoring a landscape of healthy, connected Maine waterways, one measurement at a time.
by Kira Bennett Hamilton
If you’re ever driving through Northern Maine with TNC Maine Aquatic Restoration Manager Hadley Couraud, expect some detours to look at her favorite culverts.
In case you haven’t yet had the pleasure of studying them yourself, culverts are human-made structures built to channel water beneath roads, bridges and other infrastructure. They’re necessary wherever roads intersect with waterways—which, in Maine, happens in over 25,000 locations.
Many are made of black corrugated pipe or concrete. Others, in a testament to Yankee thrift and ingenuity, employ more creative salvaged materials. And thanks to two summers spent measuring culverts on TNC’s stream crew earlier in her career, Couraud has encountered many of them. “We’ve found culverts hidden behind downed trees or inside beaver dams, and others innovatively fashioned out of overturned dump trucks or old rail cars,” she says with a laugh.
Why Culverts Matter
Culverts, though they may look unassuming, have an outsized impact on mitigating some of the dangerous effects of climate change. Storms are stronger than they used to be, sending surges of rainfall or snowmelt coursing through rivers and streams. An undersized or ill-placed culvert can easily get clogged or collapse. This leads to flooded and damaged roads. The impact is also severe on wildlife and natural habitat—when water can’t flow under roads naturally, the movement of sediment and nutrients is disrupted, and fish and wildlife struggle to migrate up and down stream to complete their life cycle.
Upgrading undersized culverts is a powerful action that communities and private landowners can take to boost their climate resilience and reduce risks to people and buildings, while simultaneously making profound ecological impacts. It’s an economical choice as well because more resilient infrastructure requires less maintenance, and hence smaller budgets, over time. But which culverts are most at risk? Couraud’s job today as aquatic restoration manager involves working statewide to support communities in planning and implementing stream crossing upgrades that can yield the greatest benefits for people and nature. And it all rests on data painstakingly collected by seasonal stream crew members like her over the course of 13 years.
A 13-Year Research Project
In 2006, TNC started working with the Maine Department of Marine Resources and the United States Fish and Wildlife Service to collect data on road-stream crossings. Starting with only volunteers, the effort grew to include paid summer crews and invaluable contributions and partnerships with numerous other state and federal agencies, non-profits and Tribes. Ultimately, after 13 years, the teams assessed more than 25,000 crossings—over 90% of the total found in Maine.
For Couraud and the crews she led in 2018 and 2019, this meant 10-hour days spent driving around Aroostook County to where maps told them culverts should be, figuring out where they actually were (maybe inside that beaver dam?) and measuring the dimensions of each culvert. They observed how water flowed through the crossing and compared those measurements to a nearby section of the stream that was not affected by the culvert. After recording the data, they would hop back into the truck and drive on to the next crossing.
The crew worked through clouds of blackflies and swarms of mosquitos, in fair weather and foul. “When it rained,” Couraud says, “we’d keep going unless it came down so hard the tablets couldn’t register the difference between our fingers and the raindrops. Or if our supposedly waterproof paper started dissolving, then it was time for a break.”
Hadley Couraud and Joshua Royte collecting culvert & stream data in the field.
After their work day was done, the crew would set up camp for the night. Sometimes they’d be invited to stay at a guest house or an empty camp, or to join neighbors for a meal. One time this meant pitching tents in the front yard of a logging camp and sharing a meal with a group of loggers at the end of the day, swapping stories about equipment and why in the world the crew cared so much about culverts!
Once the crossing assessment project wrapped up in 2019, the coalition of partners had amassed the most comprehensive set of road-stream crossing data in the United States—and quite possibly the world. It was time to put the data in action.
Quote: Hadley Couraud
My vision for the rivers and streams of Maine is a landscape of healthy, connected waterways.
From Research to Action
“All over the state, there are undersized or dilapidated culverts that block fish from swimming upstream and are at risk of blowing out during storms,” explains Dan Coker, TNC Maine’s Interim Director of Conservation Science. “Using the road-stream crossing data, we developed an Aquatic Barrier Prioritization Tool that can help towns, private landowners and Tribes figure out which crossings are both important for fish and likely to flood, so they can make plans to upgrade them. In Phillips, for example, town officials used the tool to identify five at-risk culverts to upgrade. In 2023 and early 2024, back-to-back storms flooded roads and washed out culverts throughout the Sandy River Valley—but the upgraded culverts were unharmed by the floods.”
After her time as a stream crew lead, Couraud took a position with Sebago Clean Waters (SCW), a collaborative of conservation organizations working to keep Sebago Lake’s waters clean and clear through forest conservation. “At SCW, I worked with the Lakes Environmental Association and Casco Bay Estuary Partnership to plan strategic road-stream crossing improvements using that data set," says Couraud. “It was rewarding to see firsthand how other organizations beyond TNC were using the tool to advance their missions.”
In 2022, Couraud rejoined TNC’s freshwater team. Today, she works with communities throughout the state to plan restoration projects using the wealth of information in the road-stream crossing database. For instance, in Aroostok County, the Houlton Band of Maliseet Indians is leading the Wolastoq-St. John Restoration Initiative. Using data collected by the stream crews, project partners are working with town officials to plan road-stream crossing upgrades that can reduce flood risks while also improving fish passage and water quality.
Couraud’s ultimate goal in this work? “My vision for the rivers and streams of Maine is a landscape of healthy, connected waterways that carry fish and aquatic critters alongside the stories, livelihoods and heritage of Maine’s human communities. It’s crucial that this vision centers the Wabanaki, new and rural Mainers and provides ways for everyone to have a positive connection with the incredible rivers flowing through the home we share here.”
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