Beaver Management
Public Works | Natural Resources Division
About Beavers
Beavers are nocturnal rodents that can be found anywhere their food—trees, woody plants, and other vegetation— is abundant. They typically live in rivers, streams, lakes, marshes, and even roadside ditches. The feel and sound of flowing water triggers their instinct to construct dams.
Beavers build dams to create suitable habitat for their beaver lodges, access to food, and protection from predators. Beavers use whatever materials are available to construct their dams, including stone, mud, wood, and plants.
Environmental Benefits
Beavers are keystone species, meaning that they have a huge impact on their ecosystem. They are “ecosystem engineers” that significantly alter their environment and create hotspots of biodiversity.
Beavers:
- Provide critical habitat for many terrestrial and aquatic species. This often includes salmon and other cold-water fish, migratory waterbirds which often nest or rest near beaver ponds, and many other amphibian and mammal species.
- Recharge groundwater and elevate water tables.
- Cool downstream temperatures of the waterway by almost 5 degrees Fahrenheit on average.
- Improve water quality by slowing and storing rainwater, excess sediments, and excess nutrients in their ponds.
- Store carbon in organic sediment in beaver ponds.
- Provide natural fire breaks by creating wetlands with wetter soils that can serve as a barrier to wildfire spreading.
- Increase hydrological complexity which may help mediate high winter flows.
Beavers on Your Property
If beavers are causing issues like flooding or plant loss on your property, there are several steps you can take.
Plant Choice
Choose plant species that beavers generally avoid, and plant them away from known beaver trails. Use plants such as cascara, elderberry, hawthorn, ninebark, osoberry, Sitka spruce, and twinberry. Avoid planting alder, birch, cottonwood, vine maple, and willow.
Tree Fencing
Tree fencing can be installed by wrapping the trunk of the tree with welded wire fencing, hardware cloth, or multiple layers of chicken wire. Corrugated plastic drainpipe can also be used, but dark colors may burn the tree in direct sunlight, so a wide diameter pipe or holes may prevent overheating. The fencing must be at least 3 feet high. Staking the barriers may prevent beavers from getting underneath or around the fencing.
Photo by Thinglass, Getty Images.
Textural Repellant
Textural repellant can be used to discourage beavers from cutting down trees. Apply a mixture of sand and latex paint to the first four feet of the tree trunk. Commercial taste and odor repellants are also available but often require reapplication and have mixed results.
Photo by GIPI23, Getty Images.
Culvert Protectors and Pond Levelers
Culvert Protectors protect the inlet of a culvert from being dammed by beavers by constructing a V-shaped, semicircular, or trapezoidal fence using woven wire mesh. This would require an HPA (Hydraulic Project Approval) permit from WDFW.
Pond levelers control the maximum water level behind a beaver dam. The effectiveness depends on the beaver, which may relocate upstream or downstream and build a new dam if the water level is dropped too low. A professional should perform installation and maintenance. Installing pond levers generally requires an HPA permit from the Washington Department of Fish and Wildlife (WDFW), which may be challenging to obtain if salmon use the stream.
Dam Notching or Removal
Beaver dam notching is a very temporary method to lower the water level behind the dam. This involves removing a one- to three-foot section of the dam to allow water to flow downstream. Beavers will usually repair the dam overnight.
Beaver dam removal is a temporary solution to allow free flow of the stream. Typically, beavers will rebuild the dam in the same location or nearby over the course of a few days.
Both dam notching and removal require an HPA permit from WDFW.
Beavers on Public Land
If beavers are causing flooding or damage on public property such as parks, roads, or other county or state land, you can report it to one of these numbers:
Damage to roads: Call our Operations Division at (360) 416-1480.
Damage to parks: Contact Parks and Recreation at (360) 416-1350 or parksrec@skagitcountywa.gov
Damage to public drainage utility: Contact (360) 416-1434 or aidam@skagitcountywa.gov
Damage to other public spaces: Contact CJ Jones, Drainage Utility Project Manager, at (360) 416-1448.
Banner photo by Jillian Cooper, Getty Images.
