Culverts can create the ideal conditions for beavers (figure 4). Beavers instinctively build a dam when they hear the noise of water channeled through a culvert. Culverts usually have hardened embankments that give beavers a foundation for their dams. Riparian areas nearby often provide habitat and a food source for the beaver.

Figure 4—Most culverts create ideal locations for beavers
to construct their dams.

Some national forests have demolished beaver dams in hopes that the beavers would leave the area. Dams can be demolished by hand, with backhoes or other types of equipment, or with explosives (not generally recommended). While demolition may work occasionally, beavers usually rebuild or repair the dam within days, especially in areas with good beaver habitat.

This report describes ways to manage beavers and existing culverts. In many cases, the ideal solution would be to replace or relocate the culverts to more suitable locations or conditions. Doing so can be very costly. New or replacement culverts should be designed to prevent beavers from damming them. Oversized culverts should be used to reduce the speed of flow through the culverts, decreasing the likelihood that beavers will want to dam them. Oversized culverts also make fish passage easier. Some people have had good success with steel culverts with flared ends or rectangular concrete culverts.

If replacing culverts is not an option, several methods of controlling beavers around existing culverts include:

• Installing devices that keep beavers from damming culverts
• Installing devices that reduce the speed of waterflow at the culvert's entrance or exit
• Trapping or shooting beavers
• Using devices to frighten beavers
• Using repellants
• Installing fencing

Common names of devices used to control beavers (beaver bafflers, beaver deceivers, or beaver relievers) have not been used in this report because these names are not used consistently across the country. One person's deceiver is another's reliever, and so forth.