More Than Mundane: As Climate Warms, A New Focus On Culverts For Trout Survival, Road Durability

Oct 10, 2019

Retired Chequamegon-Nicolet National Forest scientist Dale Higgins demonstrates stream measurement techniques on Drake Creek near Crandon.
Credit Ben Meyer/WXPR

Few drivers zipping along Northwoods roads probably think about the culverts they cross, culverts sending stream water underneath the pavement or gravel.

Instead, it’s Jon Simonsen’s job to worry about the structures, which play a major role in both transportation and fish habitat.

“People don’t give a culvert much thought, and they’ll pass over it.  But they think about it a lot when the road is washed out and the road has failed,” said Simonsen, a DNR transportation liaison.  “So that’s when it has become significant.”

For example, heavy storms, flooding, and washouts made much of Wisconsin’s Lake Superior region impassable three years ago.

The DNR's Jon Simonsen explains principles in culvert design and construction.
Credit Ben Meyer/WXPR

Standing above a culvert on Drake Creek Lane just northwest of Crandon, Simonsen said the issue is often simple.  Many culverts are just too small to handle the amount of water they may face.

“Yeah, that’s the biggest problem.  The culverts are much narrower than the water that the stream tries to carry,” he said.

There are more than 265,000 places where roads cross rivers, creeks, and streams that flow into the Great Lakes.

Most of those crossings are just small culverts, and many of them are too small.  Researchers believe almost two in three of those culverts block fish movement and hurt their habitat.

What’s more, as our climate changes, those culverts are more susceptible to flooding, washouts, and road blockage.

The Drake Creek culvert is one of those undersized structures.

On the site a few weeks ago, Simonsen gave presentations to about 80 federal, state, local, tribal, and nonprofit workers from across the state who are looking to learn more about road-stream crossings.

Dale Higgins is another one of the instructors.  He addressed a small group while wearing chest waders and standing in Drake Creek itself.

“There’s another way than just putting in the smallest culvert you can to save money,” Higgins said.

Higgins was employed for more than three decades with the Chequamegon-Nicolet National Forest, where he worked on about 250 road-stream crossings.  He’s retired, but he’s here because these streams are important to him.

“The thing that’s great about it is you feel like you’re trying to restore, improve the environment, but also help people,” Higgins said.

He’s passionate about well-designed culverts to prevent road flooding and washouts, but also to restore good trout habitat.  That habitat is at risk when undersized culverts create underperforming trout streams.

“A big focus is on trout being able to move up and down the streams to get to winter, summer, foraging, and spawning habitat.  Wisconsin is blessed with a lot of trout water,” said Chris Collier, the Great Lakes Stream Restoration Manager for Trout Unlimited, the group that helped organized the workshop.

Collier knows trout need to be mobile and have access to colder waters to survive.

“The biggest issue facing those trout waters in northern Wisconsin is fragmented habitat, so they can’t get up and down,” he said.

Anyone can identify a poorly designed culvert just by looking at it, according to Collier.

“They’re too small.  It’s quite simply, they’re too small,” he said. 

“If you look into the stream, you don’t want to see water shooting out of a culvert really fast, or dropping off like a mini-waterfall.  Those are all signs that something’s wrong.  The culvert’s installed wrong or it’s the wrong size for that stream.”

Undersized culverts don’t let the water or fish move freely.

The Drake Creek culvert is an example.

Because it’s too small, debris collects on the upstream side, helping lead to water backups.

Debris collects on the upstream side of the undersized culvert as Drake Creek crosses under Drake Creek Lane.
Credit Ben Meyer/WXPR

Downstream, water shoots out quickly, eroding the streambed.

“Some of [the culverts] were pretty bad.  A lot of them were bad, but there has been a lot of progress made over the last 20 years, trying to recognize the shortcomings of the old, strictly, put in the smallest culvert you can, squeeze water through the culvert [model], and the impacts that has both to the environment and then to the infrastructure, too,” Higgins added.

Drake Creek, like thousands of waterways in the region, probably could use a new, bigger culvert, one designed for more than just the present, said Higgins.

“These structures could be in the ground maybe as much as a hundred years,” he said.  “What’s the climate going to be like and the flood flows in the future?”

Retired Chequamegon-Nicolet National Forest scientist Dale Higgins reviews charts with Vilas County Conservation Specialist Quita Sheehan.
Credit Ben Meyer/WXPR

The DNR expects a warmer, wetter climate with more heavy rainstorms and flooding.

In its Inland Trout Management Plan, finalized in March, the DNR calls climate change a “major threat” to cold-water fish like trout.

Climate change and more water will also put pressure on the culverts trout move through, said the DNR’s Simonsen.

“We already see a lot of culverts out there that are undersized, that are barely just hanging on,” he said.  “We have to start thinking long-term and planning for that now so we’re not just chasing washed out roads when our options are limited.”

In 2017 and 2018, Trout Unlimited helped replace or remove 11 road stream crossings in and near the Chequamegon-Nicolet National Forest.

It’s a start.

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