Beavers are attracted to dam road culverts and other drainage structures because with a little work they can create a large pond.
Fortunately, there are multiple cost-effective flow devices that can protect culverts and drains from beaver damming. Flow devices save time and money, protect infrastructure and improve public and work crew safety. They support human land uses while allowing the beavers to remain in place to create ecologically valuable wetlands. They are almost always better long-term options than beaver trapping.
Various Flow Devices to Protect Culverts, Sluiceways and Drains
Beavers need deep water for protection and survival. They typically will build dams where it is the least amount of work to create a large pond. This is often where stream channels narrow, or at manmade structures that constrict stream flow such as road culverts, manmade dam sluiceways, and drain pipes. Fortunately manmade structures can almost always be protected from beaver damming. Which type of device is most appropriate is determined by the specific site characteristics.
If water deeper than 3 feet is tolerable upstream of the structure, then a Fence and Pipe device is likely your best option. If you need to keep the water at the original stream level, then a Culvert Protective Fence is probably your best option. If a beaver dam is tolerable immediately upstream of the drainage structure provided the structure remains completely open, then a Diversion Dam may be the easiest and least expensive flow device to install. See the descriptions and photos of these devices below.
Culvert Protective Fences
Culvert Protective Fences are built in various shapes and sizes depending upon the topography of the stream channel, water depth and stream flow. They are ideal for shallow areas that cannot be impounded, since they keep water flowing at the original level of the structure. They work by converting the inlet of the culvert or drainage structure from the easiest place for beavers to dam, into the hardest. This encourages the beavers to dam elsewhere, leaving your infrastructure unblocked. With an hour of maintenance per year, Culvert Fences have a 95% success rate.
Fence and Pipe Device
The Fence and Pipe flow device is the most common method to protect road culverts and manmade drains. It allows beavers to create a pond by damming on a small exclusion fence on the structure inlet, and a Pond Leveler pipe is installed through the fence to control the height of the damming. The Pond Leveler pipe intake requires a pool depth of at least 3 feet to be effective. If that depth is not tolerable, a Culvert Protective Fence may be a better option. The Fence and Pipe device has a 99% success rate and requires less than 1 hour of maintenance per year.
A Diversion Dam is the simplest and easiest device to install to protect road culverts from beaver damming. It encourages the beaver to dam immediately upstream of the road culvert rather than in it. It keeps the culvert unblocked and lets us control where the beavers dam. It is best used where ponding upstream of the road is tolerable, and is nearly maintenance free. It also is the most most wildlife and fish friendly flow device. Diversion dams can be started with fencing, rocks or wooden posts and branches like a Beaver Dam Analog (BDA).
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Trapping & Breaching
In some regions with low beaver populations, problematic beavers can be live trapped and relocated to suitable habitat away from human development.
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