There is a lot of talk right now about living with beaver in urban landscapes. Beavers are helping to store water in drought times and build habitat for many of our critical species in our cities. But beavers are not always good neighbors to our human built community, especially when they build dams in or near culverts. Beaver deceivers are one way to remedy beavers often considered nuisance behavior while also allowing them to keep working their magic as keystone species.
Over the last few years our Tigard, Knez preserve has had very active beavers near an important culvert. This fall Cascade Education Corps, an alternative high school program spent the week with TWC building and installing a beaver deceiver to lower the flooding risk and keep the beavers in the wetland. It is not an exact science, installing a beaver deceiver, but when you get it right, it is amazing to see how we can all live together.
Thanks to the City of Tigard for all the materials needed to build the deceiver!
Beaver Deceiver Photo Story
The function of a beaver deceiver is to lower the water in the pond behind the beaver dam, but allow the beaver to continue to build their dams at their normal rate. Here we begin to build the cage, that will be installed with the pipe into the dam. The cage keeps the beaver from blocking the pipe once it is installed in the dam.
The cage is done, and it is big! Now it can be installed with the pipe. The pipe is the “deceiver”, if done correctly it continuously releases water so the pond never goes above the level of the pipe.
Part of the deceiver is also a fish passage gate in the cage. This is the beginnings of the gate built out of PVC. The gate allows fish that swim into the pipe to get out of the cage, most importantly it allows spawning salmon to continue their journey upstream.
The last details of the fish passage gate, now painted green, get put together just before installation into the pond.
The pipe and cage are ready to be installed. Now we carry them down to the beaver dam and prepare the dam for installation.
Before the pipe can be installed, the beaver dam has to be notched. The pipe is placed into the notch. These brave students are holding the pipe in place getting ready to secure the pipe the cage in the pond.
Now to hide the pipe and rebuild the dam! Beavers make it look easy, but putting the dam back together is tough. The idea is bury the pipe so the beaver never know the pipe was installed into the dam and to once again dam up the water so that it is only flowing through the buried pipe.
The final product, water is flowing through the pipe and the dam is rebuilt so water is now only flowing through the pipe and the beavers can continue their work!