Beaver populations increased dramatically during the last half century. Beavers and beaver dams now are found on rivers, streams, and creeks across the country. Although beavers dam streams for their own benefit, the ponds create habitats for birds, fish, and other wildlife.

Unfortunately, as road engineers and maintenance crews know, beavers also plug culverts. When culverts are plugged (figure 1), roads can be washed away by flooding. Removing the beavers' dams usually requires heavy equipment, which is costly.

Figure 1—A culvert blocked by a beaver dam on the
Allegheny National Forest.

The U.S. Department of Agriculture (USDA) Forest Service Missoula Technology and Development Center (MTDC) was asked to investigate methods to solve the problem of beavers damming culverts. Road maintenance costs could be reduced if beavers could be prevented from damming culverts. Ideally, these methods would maintain beaver populations and associated wildlife.

MTDC asked Forest Service personnel about the strategies they had used to deal with problems caused by beavers. Additionally, MTDC requested the help of USDA Animal and Plant Health Inspection Service, National Wildlife Research Center (NWRC) beaver experts, and their colleagues. The NWRC presented a full report to MTDC. That report can be obtained from Andy Trent at MTDC.

This report includes the methods described by the NWRC experts followed by discussion of the experiences of the 50 Forest Service employees who responded. In some cases, no respondents had tried methods described by the NWRC. No silver bullet approach will take care of all beaver problems. But this report will describe a number of methods that can be used, depending on the particular situation.