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Why Did the Fish Cross the Road?

The Nature Conservancy, with funding from the Vermont Department of Environmental Conservation and the Vermont Fish & Wildlife Department, is assessing whether animals can move through culverts in Champlain Basin watersheds.

July 10, 2013

Culvert 125 by 83

Why did the brook trout cross the road? It couldn’t. A poorly designed culvert blocked its way. In Vermont such structures not only fragment aquatic habitat, they’re also the ones most likely to fail catastrophically during extreme flood events like Tropical Storm Irene.

That’s why the Vermont Department of Environmental Conservation (DEC) and the Vermont Fish and Wildlife Department (VFWD) are partnering with the Vermont Chapter of The Nature Conservancy to assess undersized and poorly designed culverts.

The just completed Lamoille River Basin assessment is representative of others conducted in the Lake Champlain Watershed. It evaluated culverts for both Aquatic Organism Passage (AOP) and geomorphic compatibility (a structure’s ability to withstand high flows without failing).

In 2011, The Nature Conservancy received a $26,122 Ecosystem Restoration Program grant from DEC and $17,004 in matching funds from VFWD to manage the Lamoille River Basin assessment. In 2012, DEC awarded the Conservancy an additional $12,968 to assess culverts in the Lewis Creek and Otter Creek watersheds. VFWD is expected to contribute $19,000 toward this new effort.

“Cataloguing and prioritizing the structures is the first step to solving the aquatic connectivity problem,” says Nature Conservancy conservation biologist Paul Marangelo. “In some towns, we found 60 to 80 percent of culverts evaluated to be partially or completely incompatible with aquatic passage. Out of the 1,160 culverts assessed in the Lamoille River Basin, 440 were completely incompatible with aquatic organism passage.” Most of those also have a high likelihood of washing out in major storm events.

Fragmentation of Vermont’s waterways means that aquatic ecosystems are less resilient. Game fish—like brook trout and salmon—minnows, turtles, salamanders and invertebrates need to move freely to find food and breed, maintaining genetic diversity. Fish also need to take refuge from harsh conditions, seeking warmer waters in winter, and cooler water in summer, a need now made increasingly dire by climate change.

The Lamoille River Basin assessment uncovered significant culvert failings: “I found some jammed with old bicycles, dammed with logs, or crushed, while others were disconnected in the middle, with the water not running all the way through,” says Dan “Rudi” Ruddell of Redstart, Inc. The Conservancy contracted with Redstart, Inc. to conduct the fieldwork in the Lamoille watershed.

The worst barriers are undersized, perched culverts. “When a stream passes through an undersized culvert during high flows, the water shoots out the downstream end like a fire hose, scouring a deep pool, and leaving the culvert perched above, inaccessible to fish,” says Vermont FWD fisheries biologist Rich Kirn. “We have undersized perched culverts all over the state.”

The Nature Conservancy is playing a major role in informing towns about the new assessment. “TNC created reports for all the watershed towns, and we’ve worked closely with them to educate municipalities about the importance of replacing inadequate culverts, for both enhanced geomorphic compatibility and aquatic organism passage,” said Amanda Holland, until recently a transportation planner with the Lamoille County Planning Commission.

Now the towns must find funding to replace the culverts, which can cost $50,000 or more per structure. “The data TNC gathered, tying geomorphic compatibility to aquatic organism passage, lets us tell a more complete compelling story,” that can appeal to a variety of potential funders, says Holland. “We’ll share the assessment with town conservation commissions, the Lamoille River Anglers Association, and other conservation groups who may want to help. Sometimes it’s about marrying the right group to the right opportunity.” Funding also comes from state and federal coffers.

“There has been great cooperation, communication and enthusiasm from the state level down to the town level,” concludes Marangelo. “By helping fish, we are also helping our municipalities to prevent costly future flooding.

The Nature Conservancy has now completed aquatic connectivity assessments in the Lamoille, Poultney, Mettowee, Missisquoi, Pike, and Rock river watersheds, with evaluations soon to be underway in the Lewis and Otter Creek watersheds.

Learn more


The Nature Conservancy is a leading conservation organization working around the world to conserve the lands and waters on which all life depends. The Conservancy and its more than 1 million members have protected nearly 120 million acres worldwide. Visit The Nature Conservancy on the Web at

Contact information

Paul Marangelo
Conservation Ecologist
802-229-4425 x119

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