Most people don’t think about culverts, the large pipes that carry streams and runoff underneath our roads. Even with their essential role in our transportation infrastructure, culverts tend to be in the spotlight only when they fail. In dramatic ways, Hurricane Irene and other recent storms have put culverts (and bridges) to the test. Unfortunately, the high water from these storms overwhelmed many culverts, washing out roads, causing millions of dollars in damages across the Adirondacks, and disrupting life in many communities. For example, the town of Jay sustained about $400,000 in damage to its culverts and adjacent roads as a result of Irene. Across the Northeast, the story is much the same.
Following Tropical Storm Irene, I was part of a team of conservation professionals to assess the performance of road-stream crossings (i.e., culverts and bridges) in Vermont’s Green Mountain National Forest. The peer-reviewed study, published in the current issue of Fisheries, found that damage was largely avoided at crossings with a stream simulation design, an ecologically-based approach that creates a dynamic channel through the structure that is similar in dimensions and characteristics to the adjacent, natural channel. On the other hand, damages were extensive, costly, and inconvenient at sites with stream crossings following more traditional designs.
Ideally, what do we want from a culvert? Effective culverts permit water, sediment, debris, fish and other wildlife to travel without interruption. Undersized and poorly placed culverts can put people at risk, because they are more likely to clog with debris, contribute to flooding, and fail during large storms. In addition, they can be very costly, especially as we see more frequent intense storms, because they require more frequent maintenance and repairs. Culverts that are too small, shallow, or perched above the streambed obstruct fish and wildlife movement. They can prevent brook trout, for instance, from reaching cool tributaries when main stem rivers become dangerously warm.
Improving stream crossings is a cost-effective, concrete action that can better prepare communities for the more frequent and intense storms we are seeing, while also benefiting the long-term health of our rivers and streams. In the Ausable River Watershed, the Adirondack Chapter of The Nature Conservancy, in partnership with local highway departments, the Ausable River Association, Essex County Soil and Water Conservation District, and environmental agencies, is working to prioritize culvert replacements to ensure that investments are made in locations where the most ecological, economic and social benefits are expected.
In the towns of Jay, Wilmington, Keene, North Elba, and Black Brook, the overlay of ecological data with expert knowledge of problem culverts (e.g., culverts with recurring flood problems during large storms and/or requiring frequent maintenance) has narrowed the focus to about 25 of over 500 total culverts. With our partners, we are now taking first steps toward improving five of these high priority culverts, which will open 25 miles of upstream habitat for fish, while also alleviating maintenance costs and reducing flood risks. You can learn more here.
Photo: Stream simulation design culvert at Jenny Coolidge Brook (Vermont), installed in June 2010, showing height of 100-year design flow in red and height of Tropical Storm Irene flood level in blue. Photo courtesy Brian Austin, Green Mountain National Forest.
Jessica Levine works with the Adirondack Chapter of The Nature Conservancy on projects to improve aquatic ecosystem health, flood resilience, and transportation infrastructure.