DUXBURY, Vt. (AP) — Bridges get a lot of attention when they fail, but scientists are working to eliminate what they say can be an even greater scourge, because of their sheer numbers and their effect on wildlife: culverts.
These passages that carry smaller streams under roads and driveways number in the thousands across the East, and their importance came into sharp focus during storms Irene and Sandy in the past few years, when floodwaters washed many of them out and cut off access for days or weeks.
"Every culvert is a potential disaster for our roads," said Rose Paul of the Vermont Chapter of the Nature Conservancy, which has been working with the state to assess its culverts. "At the same time, it's a potential big problem for fish and other aquatic life. So we need culverts, but we need them to be well designed."
Vermont, which has been assessing its culverts for about a decade, helped develop a program being put into place for 13 Eastern states that are contributing to a regional database of those road-stream crossings that will help policymakers decide which culverts should be replaced or upgraded first, said Rich Kirn, a biologist with the Department of Fish and Wildlife who has helped lead Vermont's efforts.
The crossings are being examined to determine if the culvert is big enough for the waterway it is carrying by looking at the width of the stream and the stream bank. Crews are also looking at how far the water falls when it comes out of the culvert.
A short stretch of back road in the town of Duxbury provides an example of what's good and what's not.
The good: The bottom of a large culvert carrying the Crossett Brook is the same combination of rock, sand and gravel as the streambed, and there's no clear indication where it begins or ends.
The bad: In another culvert, the water from a smaller brook that empties into the Crossett falls about 3 feet from a round pipe that has scoured a deep pool in the brook.
The network standardizes uniform data collection for the tens of thousands, if not hundreds of thousands, of culverts across the region. In addition to the six New England states, it includes Virginia, West Virginia, Pennsylvania, New Jersey, Delaware, Maryland and New York.
In Massachusetts, there are about 35,000 road crossings, said Scott Jackson, an associate professor in the Department of Environmental Conservation at the University of Massachusetts at Amherst, who is leading the regional effort that builds on separate programs that have been underway in parts of New England.
He estimated there is a similar number in Vermont and New Hampshire while in the larger states, like New York and Pennsylvania, the numbers are much greater. "It's an enormous number," he said.
Jackson helped develop the larger program involving the 13 states along with the Vermont Agency of Natural Resources, the Nature Conservancy and the U.S. Fish and Wildlife Service. The collaborative is funded with $475,000 from the North Atlantic Landscape Conservation Cooperative through the Disaster Relief Appropriations Act of 2013, which dedicates federal funds for Superstorm Sandy recovery.
"We recognize that some of these road-stream crossings are going to be significant barriers to fish and other aquatic life, and others are not," Jackson said.
In the summertime, some species of fish, like trout, will seek the cooler waters of the smaller brooks and streams.
A bridge is a stream-crossing structure that has abutments, a deck and a natural stream bottom. A culvert is a stream-crossing structure that has some sort of fill over it, said Alex Abbott, a fish passage specialist in Maine who works in cooperation with the U.S. Fish and Wildlife Service and other groups and is helping develop the region-wide protocol.
"We culvert people have been working in the shadows for a while," Abbott said. "This is a problem most people are oblivious of."
North Atlantic Aquatic Connectivity Collaborative: http://www.streamcontinuity.org