If an earthen dike, or dam, is built with a 3-to-1 slope, it is unlikely that beavers, or other semi-aquatic animals, will burrow into it as they prefer steeper slopes. Dikes with steep slopes can be protected with either bowling ball-size rip-rap or sturdy wire fencing on the upstream side of the dike. If fencing is used, it should be staked to extend about two feet above the water level and several feet below.
Since beavers live on lakes and rivers with docks, occasionally one will take advantage of a manmade “roof” by modifying a dock’s understructure into a den. This is especially true of floating docks supported by foam blocks, as a beaver may hollow out a cavity in the foam for a nest. Wrapping galvanized welded wire fencing around the flotation blocks protects them, and similar fencing prevents any gnawing of wooden supports. Replacing the foam blocks with flotation logs, encased in a resistant polyethylene shell, is the best solution because exposed foam slowly crumbles into the water, and must be replaced with a sealed version since 2013.
At times it is desirable to stabilize a beaver dam, where a break would cause excessive flooding downstream and/or much loss of wetlands habitat upstream. To do this, drive a series of fence posts into the dam, plant vegetation on the dam, and bring branches to the site for the beavers to use.
When beavers are being transplanted to a site to manage a stream’s flow, consider creating a starter pond by driving a series of fence posts into the stream bottom at the site where the dam is desired.