Ignorance about beavers and their role in nature can cause alarm about having these large animals in the neighborhood. Fear of the unknown also often causes exaggeration, such as saying dozens of beavers are present when there are only a few. When a beaver fells a tree, a landowner may panic, unaware that such change is part of nature's cycle. Tree cutting stimulates more growth in many trees, such as willows, aspen and cottonwoods. For example, for each willow stem that is cut, three or four will appear in the spring. (Click on "Tree Cutting" for ways to protect trees).
After almost being extirpated from North America by trapping by the early 1900s, beavers are currently recolonizing some former territory. Only a small percent of the beavers that populated the continent prior to European settlement exist today. Because of the species' benefits in creating vital wetlands, and because removal is rarely a lasting solution, working with beavers gives the best results. Because of their great benefits, beavers are also being restored to Europe.
Beavers probably see culverts beneath
roads as a hole in an otherwise fine dam. So they plug the hole and flooded
roads result. Semi-circular fences of sturdy, large diameter wire mesh around
road culverts (see the drawing above) can prevent road flooding by protecting
culverts from being plugged. These are called pre-dams, or diversion dams
(because they divert the beaver's attention from the culvert). When road
beds are high enough and the water level upstream does not matter, this
may be sufficient.
One or more drain pipes are added through the pre-dam fencing, or are set in a beaver dam, to control the water level. The beavers will then dam against the pre-dam fence while water continues to flow freely. These systems may require annual maintenance that takes much less time and expense than previously spent by road crews unclogging culverts. These cost effective systems, which were first used at Canada's Gatineau Park in the 1980s, are currently used at many locations in North America, where they save taxpayers' money and also save vital wetlands.
Large diameter corrugated plastic pipes (or PVC drain pipes for small drainage areas) are set in pre-dams or directly in beaver dams to control flooding. Pipe inlets must be protected with large cylindrical cages (note the cage in the water in the picture to the right) made of large diameter (4-6" squares) sturdy mesh fencing. Lowering the water level more than one foot increases the chances of the beavers damming elsewhere, but a second device can then be installed. Be sure to check with your state wildlife agency to obtain any required permits and obtain permission from landowners, before installing a device.
A "Coexisting with Beavers" DVD is available from the BWW catalog page on this web site, and shows how to build and install a flexible leveler to manage beaver flooding upstream of a dam or a road culvert. (It also has about half an hour on the natural history of beavers, including how to protect special trees, plus a few minutes about Dorothy Richards, the "beaver woman" of the 20th century.)
A 12-page booklet "How to Control Beaver Flooding" and the video "Outwitting Maine's Busy Beaver" are available from our catalog.
In additon, you can find engineering plans for both a flexible leveler, used in a dam or semi-circular fence around a culvert, and a trapezoidal fence, which are mainly used to protect culverts, at the website of the Snohomish County, WA Public Works Dept., plus other useful information about beaver management.
Skip Lisle installs his version of the Pipe & Cage method, but uses double walled pipes and is called the "Castor Master".
Skip Hilliker, a beaver consultant for the Humane Society of the U.S., uses the Pipe and Cage flow device to successfully solve beaver/human conflicts in Connecticut and nearby states. He can be contacted via the wildlife hotline at 203.389.4411.
Mike Callahan (413.527.6472), who runs Beaver Solutions in Massachusetts, has installed hundreds of effective devices as well. A 2006 study from Tufts University showed that 93% of clients were satisfied with the results of beaver flow device installations done by the above three contractors.
A typical Beaver Deceiver is a trapazoidal fence that is narrow at the culvert and widens upstream. The one shown is 15 ft. x 15 ft. x 15 ft., but sizes and shapes vary, according to the site. Skip Lisle of Vermont, who beaver-proofed 130,000 acres of Penobscot Indian lands in Maine, invented this device. It is made with cedar posts and heavy gauge wire fencing with 6 inch squares (this comes in 5 ft. x 10 ft. sheets or rolls). These devices, which are often works of art are the best solution where the water flow is too great for a Pipe and Cage system.
At busy roads, leaving about 10" between one of the roadside posts and the culvert can allow wildlife to pass through. This size of passageway helps avoid traffic accidents, but is too small for beavers to bring in large branches. Add a floor and top to deter burrowing and climbing beavers.
Part of the secret to the Deceiver's success is that water flows from the inside of the trapezoid's sides out and beavers do not dam the fence on the sides, an unnatural angle for their damming. At a website on nonlethal beaver control by the King County, WA Natural Resources and Parks Dept., has step by step directions for the installation of a Beaver Deceiver. Skip Lisle also installs dam systems that he has trademarked as CastorMasters. He can be contacted at Beavers Deceivers, International (802.843.1017).
In Colorado, Sherri Tippie (303.935.4995) of Wildlife 2000 has sucessfully relocated hundreds of beavers to areas where their dam building is desired to create ponds and raise the water level.
The U.S. Fish and Wildlife Service Partners for Wildlife program may supply funding and /or materials for a beaver water level control device if an organized entity (such as a non-governmental orgranization or a governmental orgranization) applies. Ready-made devices to protect culverts, or use in dams, are available from Beaver Proof Add On, and Beaver Stop.
BeaverPower!, which sells beaver-related merchandise, promotes alternative energy and plans to install minihydrogenerators in beaver dams with flow devices to encourage coexistence. The Environmental News Network has news about wetlands, beavers and other environmental topics.
Where roads are of such low elevation that it is impossible to have a
wetland without road flooding, either trapezoidal fences or inexpensive
beaver bafflers can be the solution. (The beaver baffler is especially useful
in areas where ice and snow damage does not occur). A baffler consists of
5-foot-long concentric cylinders of 4 to 5" welded wire with the inner
tube of a size to fit inside the road culvert. Connect each 5-foot-long
section end to end to make the desirable length (normally 20-feet-long or
more) to fit your site.
Covering the inside cylinder with 1 by 2" mesh welded wire (garden variety) fencing prevents beaver from stuffing it with debris. Beavers will pack mud and sticks below the baffler, but usually only do this for a few feet. Heavy loads of snow/ice can crush the baffler, so this works best in the South
Maintenance with a potato hook may be needed periodically depending upon seasonal flooding and local beaver activity. (Our 12-page booklet "How to Control Beaver Flooding" gives more details: catalog).
Fencing off the culvert's outlet on the other side of the road may be necessary to prevent beavers from entering downstream, although this rarely occurs.