AU SABLE FORKS, N.Y. — The humble highway culvert, cheaper than a bridge and unseen by drivers tooling through stream-laced mountains, has become a focal point in efforts to help communities and wildlife adapt to climate change.
The critical role of these structures — essentially big pipes or concrete boxes carrying streams beneath roads — was demonstrated dramatically in a series of extreme weather events in the Northeast in recent years. In 2011, severe spring flooding followed by Hurricane Irene and Tropical Storm Lee in late summer washed out roads on the mountains of New York and New England as culverts not designed for such huge volumes of water were overwhelmed.
The planned rebuilding of aging or storm-damaged culverts is giving ecologists a rare opportunity to help wildlife expand their range into cooler regions to adapt to climate change by eliminating barriers imposed by highways and poorly designed culverts.
‘‘We’ve been exploring using culverts as a way to alleviate flooding and protect human safety, as well as helping fish and wildlife,’’ said Connie Prickett of the Adirondack chapter of The Nature Conservancy.
New York’s Department of Transportation has incorporated into its project planning a simple computer tool developed by The Nature Conservancy to highlight areas where reconstruction will have the greatest benefit for wildlife.
‘‘You can do a lot of research that ends up being a report on a shelf. That doesn’t help,’’ said Deborah Nelson, a state transportation official. ‘‘The information they’ve given us has been really helpful.’’
Nelson said DOT started using a Geographic Information System program developed by the conservancy’s Adirondack researchers last year. It identifies 149 culverts out of 1.2 million statewide as priority ones to replace with environmentally friendly designs that allow aquatic and land creatures to pass through.
A well-designed culvert allows fish to swim upstream through it by ensuring the water flow is not too fast and there’s not a big drop from the culvert edge to the stream surface. In many cases, that means replacing a round pipe with a wide concrete box-like structure. A dry shelf may be added for wildlife such as bobcats.
When replacement is cost-prohibitive or impractical, the culvert might be made more hospitable to fish and the streambed more resistant to flood damage by installing large boulders to create a step-like structure in the stream at the downstream end of the culvert, said Michelle Brown, an Adirondack Nature Conservancy biologist.
New York’s transportation agency estimates its $90 million annual cost of culvert maintenance and installation would be increased by as much as 80 percent if all stream crossings were rebuilt to ecological standards. The new tool identifying the most crucial sites — those that will open up the longest segments of stream and benefit important species such as native brook trout — makes the most of limited resources, Nelson said.