At Milepost 18 along Highway 22 in Tillamook County, Oregon, beaver dams used to clog a 6-foot-diameter culvert, blocking fish passage and over-saturating the roadfill. Not anymore. Oregon Department of Transportation (ODOT) biologists enticed the beavers to build upstream of the culvert. To accomplish this feat, they slowly lowered the dam until the pool around it reached the historic creek elevation. Then they went 20-30 feet upstream, where they pounded wood stakes into the stream bed in a slightly upstream arch, making sure the stakes protruded no more than 8 inches above the water so the stream would flow normally and fish would not have to jump over the structure. Material from the old dam was placed on the upstream side of the stakes to "bait" the beavers into replacing their dams at the new location. The strategy worked. After a few "return visits" to the culvert, the beavers re-established dams upstream where the stakes had been placed. Even when these new dams were breached by severe storms, the beavers kept coming back to the same spot to build new ones. The technique was so successful ODOT used it at other State highway locations.
--Aug 21, 2006
|Construction of a beaver diversion structure upstream of the culvert. The diversion device is used to entice beavers to construct their dams upstream|