Park Perspectives: Culverts as a common cause

The Ausable River is a far-reaching system, fed by dozens of streams dropping out of the eastern High Peaks, moving water into the major courses of the East and West Branches before the rivers join to tumble out of the foothills and into Lake Champlain.

At some point in its travels much of the flow from this great gathering of water is funneled through one or another of hundreds of culverts, man-made tunnels placed in streambeds to carry the flow beneath roadways. Not many of us are aware of the culverts hidden below as we tool along the highway, but these constructions where the river meets the road are deceptively sensitive intersections of wild and human communities.

Researchers in 2011 set out to survey two hundred culverts in the Ausable system. They studied how their various designs can form obstacles to fish that need to move upstream from the large branches into the cooler tributaries. There they find adequate oxygen in the heat of summer and safe spawning areas that will survive the winter. This was essentially an ecological approach.

Then on August 28, one day after the first season of data collection was complete, the role of culverts along the Ausable became emphatically and violently the subject of human concern. Tropical Storm Irene dumped torrents of rain on the region, inundating the watershed.  Floodwaters couldn’t squeeze through the too-narrow openings of many culverts and spread instead over roadways and adjoining property. Debris crashed against the culverts, creating dams that exacerbated flooding and in many cases shattering culvert pipes that then washed downstream.

The study of the places where the river meets the road suddenly became a study, too, of the places where ecological health meets human safety.

This brings me early this November to the confluence of Holcomb Brook and the West Branch of the Ausable River, where the brook flows through a culvert under River Road near Lake Placid. With me are Corrie Miller, executive director of the Ausable River Association, and Michelle Brown, conservation scientist with the Adirondack chapter of the Nature Conservancy. Along with researchers from Plattsburgh State University, they have been responsible for the culvert survey.

Holcomb Brook falls over a series of gentle rapids as it approaches the concrete opening of the culvert, then funnels into a six-foot diameter metal pipe beneath the road from which it drops about a foot to the streambed below and joins the West Branch.

Like so many along the river, this is a problem culvert. It is too narrow, squeezing the river and making it prone to overflow in high water and magnifying the force of the current in a flood. A fragment of metal from a shattered culvert draped on a rock in the West Branch shows what Irene did to the pipe.

And the drop from the culvert is too high for trout to jump, cutting them off from important habitat upstream. As these conditions repeat themselves all along the Ausable system they increase the danger for native trout, which are not only an integral part of the environment here, but a major recreational attraction.

“The fish passage is directly related to the economy,” says Brown, who estimates river activities bring nearly $4 million a year to the region.

Miller and Brown are talking about the need to improve the river’s “resilience.” For the natural habitat, this means the fish need to be able to respond naturally to threatening conditions. In particular, trout should be able to move to cooler, more oxygen-rich waters when summer heat makes the main branch inhospitable.

In a larger sense, resilience means this sprawling, ecologically rich river system needs to be able to accommodate climate change. Those warm waters that stress the trout are likely to become more dangerous for longer periods as the climate heats up. Redesigning these innocuous-seeming culverts could be a key to a river that is resilient enough to adjust to these changes.

“I really get excited about this particular project because climate change can be such an overwhelming issue,” says Brown. “It’s hard to figure out how to get your head around it and how you can make a difference. I feel like we can do this one. We can make it happen here. It’s really important for people, and it’s really important for this special place.”

The idea of resilience also applies to the man-made environment. A culvert that is wide enough to handle floodwaters (one rule of thumb is one and a half times the width of the stream) makes it better able to withstand floods without damage to the road or people’s homes.

So this is another kind of confluence. The same construction project that improves ecological resilience also brings financial and public-safety benefits. This gives the organizers of the culvert survey a direction to go with their study results. They have developed a list of the most important culverts from an ecological viewpoint (considering the size and quality of upstream habitat, for instance). Working with local highway superintendents, they have overlaid this list with an inventory of priority sites from the public-works and safety perspective. Where the priorities coincide are culverts that should be first in line for redesign. Miller and Brown are working with local governments to find funding to begin culvert replacement in 2013.

Culverts are just one system within the complex of natural and man-made systems interacting in the Ausable watershed. Solving this problem won’t be the end of concern for the river. But it would be an important step.  And the work is even more exciting as a demonstration of how to find common ground with environmental, financial, and public-policy benefits.

Says Miller: “It’s really fun to be out with a highway superintendent who says, ‘Now when I see a drop from a culvert I think, The fish! The fish!’” And they like to hear me say, ‘Oh, look at this maintenance problem.’ For me there’s this interface between the river ecosystem and the human infrastructure. We’re going to be better off as we go into the future if we can make those interfaces healthier.”

–Tom Woodman, Publisher