Installation of Flow Devices

What is a Flow Device?
“Flow device” is a general term that covers several different types of structure which have the
common goals of preventing or controlling beaver damming activity, reducing beaver related
maintenance, but still maintain the benefits that beavers create in ecosystems. Flow devices
are most commonly used to control the water level in beaver ponds or to prevent the blocking of
culverts.  

Why Use a Flow Device?
Flow devices offer the most cost-effective combination of reducing beaver nuisance impacts while
retaining the substantial benefits. Flow devices offer long-term protection from property damage.
They save time, money, and the frustration of dealing with ongoing beaver nuisance impacts. At the
same time, a flow device allows beavers to stay in natural ecosystems, creating and maintaining
ecologically valuable wetlands.

Flow devices cost more to begin with, but pay off over time when compared to labor intensive
traditional beaver management practices such as kill-trapping, dam removal, or culvert unplugging.
A 2006 study by the Virginia Department of Transportation compared the cost of flow device
installation to traditional maintenance (culvert unplugging, dam removal, trapping) and found that
every $1 spent on flow device installation saved $8 in maintenance costs.

How Do Flow Devices Work?
To prevent the blocking of a culvert, a specially designed "Culvert Guard Fence" can be installed.
The fence design employs knowledge of beaver behavior to make it much more difficult for them to
dam the culvert. Culverts are very attractive to  beavers because a roadbed with a culvert looks like
a dam with a hole in it.

To control the water level in free standing beaver ponds, a system of pipes and filter fencing can be
installed - the "Pipe and Cage System." This is appropriate where some ponded water is tolerable but
it cannot rise above a certain level without threatening adjacent property, structures, etc. The system
works like a permanent leak in the beaver dam and again, uses knowledge of beaver behavior to
prevent beavers from repairing this "leak."  

What Do Flow Devices Cost?
Prices range from $900 to $2900, not including travel.

Seventh Generation Institute has funding available to cover a portion of the cost of these
installations in sites where there is a conservation benefit to be gained by retaining beaver in the
ecosystem. Please contact us to inquire if your site is a candidate for use of this funding.

Each site must be custom constructed to address the management interests of the site
owners/managers and the circumstances of the problem. For these reasons, the cost to install a flow
device varies significantly from site to site. Factors that influence the final cost include the physical
layout of the site, difficulty and distance to access the site, how many flow devices are needed and
the types of flow devices needed.

What About Maintenance?
Any outdoor structure requires some maintenance. Although flow devices are designed and
constructed for minimal maintenance, the maintenance is critical. Depending on the environmental
conditions, and with proper maintenance, a flow device should last ten years or more.

  • Pipe and fence systems generally require an annual inspection, which the land owner can
    conduct.

  • Culvert guard fences should be inspected three to four times a year to remove any
    accumulated stream debris from the fence. Typically this is done after autumn leaves, spring
    runoff, and large debris-producing storms. This maintenance can be done by one person and
    usually requires less than fifteen minutes per cleaning. It is also much less dangerous and
    expensive than unblocking culverts that have been jammed by beaver.

Contact Seventh Generation Institute to discuss beaver management

Frequently Asked Questions

My neighbor built a flow device, but it didn’t work. What gives?
Most do-it-yourself flow devices are ineffective. A flow device is more than just a fence around a
culvert or a pipe through a dam -- the design details that appear small actually make a big difference.
A properly constructed device uses knowledge of beaver behavior to fool beavers and short-circuit
the instinct to dam. Well-constructed devices are also built to withstand harsh weather and minimize
maintenance related to debris, flooding, freeze-thaw cycles, corrosion, etc.

I have a problem with beavers. Can Seventh Generation Institute live-trap the
beavers and relocate them?
Seventh Generation Institute does live trapping and relocation, but not for the purposes of beaver
control - only as an ecosystem restoration tool where beaver are needed but absent from a stream
area.

Why? Because live-trapping and relocating beaver is rarely a long-term solution to a beaver conflict
for a number of reasons. First, it is time-consuming and expensive. Second, relocating beaver in New
Mexico requires permission from land owners who live near the relocation site. Finally, and most
importantly, new beaver almost always move into the trapped site once it is vacated. Approximately
80% of sites from which beaver are removed are recolonized by beaver within two years. Sometimes
recolonization can occur within days.

For many beaver conflicts, a flow device is a much more effective long-term solution. See the
description of flow devices above.

If I remove a dam, will the beavers go somewhere else?
No matter how many times you remove a dam, the beavers will rebuild it. Usually very quickly.

If you are concerned about loss of nearby trees that are used by beaver in dam building, be aware
that removing the dam actually leads to more tree loss. When the dam is partly or completely
removed, most of the dam building materials will wash downstream. The beavers will now cut more
trees to repair the dam.

Dam removal has a number of other negative effects on streams and wildlife, depending on the
specifics of the site. It can release a small flood of water that erodes the area immediately
downstream, or floods your neighbors property, which may create a financial liability for you. It may
send a large flush of sediment downstream, which may injure fish, or smother fish spawning areas.
Most beaver ponds are home to many fish and other wildlife – when a pond is destroyed, these
animals may be left without shelter or exposed to predators.

There must be  other alternatives …?
Conflicts with beaver are not new. Almost everything has been tried, with minimal success.
  • There are no poisons registered for use on beaver and none that are safe for other wildlife,
    fish, pets, or curious children.  
  • Even the “best” chemical repellants work for very short periods of time and under very
    limited circumstances. If your well-meaning  neighbor recommends garlic, deer repel or other
    products, don’t waste your time.  
  • Painted on textural repellents have some effectiveness but require labor-intensive repeat
    applications for most situations.  
  • Noise, dogs, electronic frightening devices and shock devices are also ineffective. Studies of
    these devices have shown that if there is any effect at all, it does not last more than one week.

Can I kill the beavers?
There are places where beaver just cannot be tolerated. However, beaver are classified as a
protected furbearer in New Mexico. If your property is in an area that is not a candidate for a flow
device, it may be appropriate to remove the beaver through kill-trapping, but it is necessary to first
contact the New Mexico Department of Game and Fish. They can provide additional information
and sometimes assistance as well. Be aware that this is a short-term solution and follow-up trapping
will likely need to be ongoing. Beaver from the surrounding areas can maintain their population
numbers even with a mortality rate of 30-40% each year.
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