Want to reduce flooding? Leave it to beavers


HINSDALE, N.H. -- The breach of a beaver dam at least a half-mile from Route 63 caused a headache Thursday when the ensuing flood of water washed out part of the road. The New Hampshire Department of Transportation was on the scene within an hour or so and workers began restoring the stretch of state highway.

The flood of water broke off chunks of the road, exposing the four-foot concrete pipe underneath. The roadway was closed until Saturday, when a NHDOT crew out of Winchester deemed it suitable to handle traffic. Hinsdale Police Chief Todd Faulkner told the Reformer NHDOT reduced the road, near Echo Farms Puddings, to one-lane traffic Monday to put on some finishing touches. Both lanes were reopened by Tuesday.

NHDOT Foreman Chris Hope said the pipe underneath the road could not handle the massive volume of water unleashed when a 12-foot-high beaver dam breached, sending water roaring down a small stream toward the road. Hope described it as a flash flood and was happy to report there were no injuries.

The act of nature caused an inconvenience late last week, but wildlife experts say beaver dams do much more good than harm. Patti Smith, a naturalist with the Bonnyvale Environmental Education Center in West Brattleboro, Vt., and a columnist for the Reformer, said beaver dams and beaver wetlands are actually beneficial to roads because they typically slow down the release of water during high-water events.

"It's only when a lot of water is backed behind a particularly large dam that beavers have not been actively maintaining and the dam gives way all at once like that, you get an event like what happened in Hinsdale," she said, adding that beaver dam breaches are "pretty uncommon" and not something to worry about.

Bernie Rideout, the chairman of the Hinsdale Board of Selectmen, told the Reformer he was eating lunch when he heard of the washout and drove to the scene, where he was amazed at what he saw.

"There was a lot of water coming off that mountain," he said, " and I mean, a lot."

He said the washout created a hassle for people who work in north Brattleboro, or Keene, but the inconvenience lasted for only a few days. He said any Route 63 driver starting in Chesterfield was probably forced to take Stage Road to get back to Route 9 and go to Brattleboro, while those in Hinsdale could get as far as Echo Farm Puddings and turn around to take Route 119 to Brattleboro. Rideout told the Reformer the surge of water came from a wet spot on the mountain.

He said he was impressed with the work of NHDOT, which he commended for its speedy response. The concrete pipe, he said, was not replaced because it was still in excellent condition.

Jon McKeon, the chairman of the Chesterfield Board of Selectmen, echoed the sentiments of his counterpart and said there were plenty of signs posted along Route 63 to advise drivers of the closed road.

"Surprises are very difficult to deal with and I think they did very well," he said.

McKeon said the washout put a lot more pressure on North Hinsdale Road.

Breaches can be avoided through the use of flow devices, which keep culverts open. Skip Lisle, a Grafton, Vt., resident, is known for inventing two beaver dam pipes that he said create "permanent leaks" in beaver dams and prevent reservoirs from getting too big. Lisle's inventions -- the Castor Master and The Beaver Deceiver -- allow for a steady release of water. He told the Reformer a dam breach is usually a sign that beavers have left the area, because the animals constantly maintain the structures, which are in a never-ending state of decay. This decay that beavers are always working to counter causes dams to become uneven and erode in certain spots.

Lisle said many people concerned about dam breaches think killing beavers or removing them from a habitat will alleviate the problem, but it is actually counter-productive because the dams will decay and breach without beavers around to maintain them.

"Ninety to 95 percent of beaver dams prevent flood damage," he said. "The more beaver dams there are, the more resistant you are to floods."

Rob Calvert, a wildlife damage specialist with the N.H. Fish and Game Department, said nothing at the state level will be done in terms of handling the dam's remains, though nearby beavers may reconstruct it. He said though dam breaches are certainly not an epidemic, they are much more common in southern New Hampshire (as opposed to the northern part of the state) because the wetlands attract an abundance of beavers. He told the Reformer there are "a fair amount" of dam breaches, but it is very uncommon for someone to get hurt.

Lisle said beaver dam breaches are a rare occurrence, especially in Vermont and New Hampshire. Though there are plenty of wetlands, reservoirs or beaver-created wetlands big enough to cause an issue require large areas, which are scarce in the two neighboring states due to the high number of mountains and hills.

"Reservoirs here are pretty small due to topography," he said. "You need flat land for wetlands, and it's very hilly here."

In addition to flow devices, Kim Royar -- the special assistant to the Fish and Wildlife commissioner -- said water control structure can be used when there is a potential for flooding, in order to reduce the volume of water in the reservoir. She said the structure lowers the amount of water and "keeps it at a reasonable level."

She also told the Reformer beaver dams contribute to the health of wetlands because they slow down the water flow, filtering a lot of silt and providing for clearer water downstream. Also, an incredible habitat forms once a dam is built and a reservoir accumulates. Royar said this greatly helps the natural circle of life because the water creates a vibrant invertebrate population, which provides food for fish, which in turn are food for birds.

Domenic Poli can be reached at dpoli@reformer.com, or 802-254-2311, ext. 277. You can follow him on Twitter @dpoli_reformer.


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