Protect Culverts from Beavers – Easily

Protecting road culverts from beaver damming is a massive issue as I described in previous blogs. Fortunately though, there are many ways to prevent beavers from damming culverts, and one of them is easy and inexpensive! It is called a Diversion Dam.

Beaver Institute™

This culvert was completely blocked. Once open this newly installed Diversion Fence keeps beaver damming out of the culvert.

Beaver Institute™

Weeks later beavers have dammed on the Diversion Fence, and the road culvert remains 100% open.

Beaver Dam Analogues work on the same principle of encouraging beavers to dam at a spot of our choosing. Basically you use a short fence or stones across the stream channel to start a small beaver dam 10 to 15 feet upstream of the culvert. Ideally your construction will start to pool a little water to attract the beaver’s attention. Your “diversion dam” then becomes the preferred spot for the beavers to build a dam, rather than in the culvert. The end result is a simple beaver dam immediately upstream of the culvert that is very conducive to fish and wildlife passage.

I have been installing many Diversion Dams over the past couple years and they work very well.

I like to check them after a week or two to ensure that the beavers got the memo. Once in a while they don’t cooperate, and still dam the culvert. If so, will pull the damming materials out of the culvert and add the sticks to my diversion dam. Then the laggards typically get the idea and only dam on the Diversion Fence. See this Diversion Dam handout for more details.

Diversion dams are best for areas where the roadbed is high and some ponding is tolerable. A pond leveler pipe can be installed through the dam at a later date if the dam height needs to be controlled. For areas were no ponding is tolerable a Keystone Culvert Fence may be a better option.

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Happy Winter Solstice!

Posted 12-21-17

Video - Beaver Diversion Dam Maintaining an Open Culvert