Beavers build dams across smaller streams to create pond habitats to live in. They are active during the open water months building these dams and in the winter months, they live off of cuttings that they have stored under the surface of the pond in food caches of willow and poplar trees.
There is much controversy relating to their contribution to the natural environment and how they should be managed. Beavers are and will be a permanent occupant of all of our flowing waters, so understanding their purpose in the environment is important.
Since the encroachment of man into the beavers world, they have been trapped for their fur and to maintain their numbers. In many areas, the beavers natural predators have disappeared and their populations, left unchecked, have exploded! Beavers can flood vast areas of land on valley bottoms, creating a wasteland of dead trees and willows over time. For this reason, their presence requires a management plan to maintain a balance in the beaver populations.
On many small trout streams, a management plan designed to maintain beaver numbers is a necessity in order to allow spawning and migratory movements of trout. Sometimes this management plan may be as simple as opening up beaver dams, to allow spawning trout migrations upstream.
The best way to accomplish this task of dam removal is by creating an opening in large beaver dams by hand. This should be done at the right time in the trout spawning migration to allow for optimal fish passage up the spawning tributaries. It is wise to have a plan for dam removal in advance of organizing such an activity. Permissions and authorizations will also be required.
A Beaver Dam Removal Plan
Preparing a plan will require a simple survey of the stream to determine where the dams are located and if you have access to maps or information on key spawning locations, you will need to fit this info into your plan. Land owners are a valuable source of information and you will also require their permission for access. The following example of a beaver dam removal map will give you an idea of the plans purpose:
Example of an Old Beaver Dam that needed to be removed:
Right Photo: This old beaver dam was located on Canmore Creek, in the Town of Canmore, Alberta. It was last occupied by beavers four years earlier, but had been left unused and still standing. The dam was 2.3 metres in height and still in stable condition.
During freshets, the flow would pour over the dam across its width, but not with enough volume of flow to breach the dam. Stream resident trout could not pass beyond the structure upstream; however, small trout did attempt to pass over the top of the dam, in a downstream direction during high flow. Unfortunately, a number of small dead brook trout were discovered in the dam materials, when the dam was removed. I suspect that they were trapped in the web of willows and branches when they tried to swim over the top of the dam.
Depending on the geographic location of a trout stream, some watershed basins on smaller streams may not generate enough volume of flow to open up an old beaver dam. Once the wood in the dam has bio-degraded enough, this will facilitate a breach, but it may take years for this to happen. Coastal watersheds receive more annual precipitation and it is a common occurrence for beaver dams to be washed out on a yearly basis.