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Flow devices or beaver deceivers are man-made solutions to
beaver Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers a ...
-related flooding problems. Traditional solutions have involved the trapping and removal of all the beavers in an area. While this is sometimes necessary, it is typically a short-lived solution, as beaver populations have made a remarkable comeback in the United States (after near extirpation in the nineteenth century) and rapidly recolonize suitable habitat. In fact, a 2006 survey found that trapping as a solution to beaver problems had a 79% failure rate within two years due to resettlement by new beavers. Flow devices are relatively cost-effective, low-maintenance solutions that regulate the water level of
beaver dam A beaver dam or beaver impoundment is a dam built by beavers to create a pond which protects against predators such as coyotes, wolves and bears, and holds their food during winter. These structures modify the natural environment in such a way t ...
s and keep
culvert A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdo ...
s open. A 2006 study by the
Virginia Department of Transportation The Virginia Department of Transportation (VDOT) is the agency of the state government responsible for transportation in the state of Virginia in the United States. VDOT is headquartered at the Virginia Department of Highways Building in downtow ...
found that for every $1 spent on flow-device installation relative to historical preventive maintenance, road repairs, and beaver population control activities, $8 was saved, for a return on investment of nearly 8:1.


Benefits of beavers

Beavers faced near extinction from unregulated trapping across North America during the early to mid-nineteenth century. This caused widespread environmental damage including the drying up of many streams and rivers formerly sustained by the high water tables associated with beaver dams. In addition, beavers create
wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (Anoxic waters, anoxic) processes prevailing, especially in t ...
s which increase biodiversity and improve water quality by removing sediment and pollutants. In fire-prone areas, beaver ponds serve as fire breaks. Salmon and trout easily cross beaver dams and scientific evidence shows that fish size and fish populations are larger when beaver are present. A
keystone species A keystone species is a species which has a disproportionately large effect on its natural environment relative to its abundance, a concept introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaini ...
, beavers create habitat for numerous other species, as exemplified by ponds created in
Alhambra Creek Alhambra Creek is a stream in Contra Costa County, in the East Bay region of the San Francisco Bay Area in northern California. Geography The creek drains into the Carquinez Strait at Martinez, via the historical Arroyo del Hambre. Alhambra ...
in
Martinez, California Martinez ( Spanish: ''Martínez'') is a city and the county seat of Contra Costa County, California, United States, in the East Bay region of the San Francisco Bay Area. Located on the southern shore of the Carquinez Strait, the city's popul ...
, by a new beaver colony in 2007 which colony, in turn, led to the return of numerous birds,
steelhead trout Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout or redband trout (O. m. gairdneri). Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and ...
(''Oncorhynchus mykiss''), river otter (''Lontra canadensis'') in 2008, and
mink Mink are dark-colored, semiaquatic, carnivorous mammals of the genera '' Neogale'' and '' Mustela'' and part of the family Mustelidae, which also includes weasels, otters, and ferrets. There are two extant species referred to as "mink": ...
(''Neogale vison'') in 2009. The most common beaver-related flooding issues that people encounter are caused by blocked road culverts or freestanding
beaver dam A beaver dam or beaver impoundment is a dam built by beavers to create a pond which protects against predators such as coyotes, wolves and bears, and holds their food during winter. These structures modify the natural environment in such a way t ...
s. Beaver-related flooding issues can usually be resolved with properly designed and installed water control devices, also known as flow devices. Flow devices are either specially designed pipes installed through beaver dams, or pipe and/or fence systems that protect road culverts from being blocked. The beneficial effects of beavers on stream flow, riparian habitat, salmon and trout, and wetland creation can be sustained with application of these inexpensive technologies, which require little maintenance.


History of flow device solutions to beaver dams

In 1952, the concept of installing perforated pipes in dams was introduced to control water levels at the Northeastern Wildlife Conference as a solution for problem beaver ponds. In 1963, Laramie reported that the
New Hampshire Fish and Game Department The New Hampshire Fish and Game Department (NHF&G) is a department within the government of New Hampshire in the United States. The Fish and Game Department manages New Hampshire's fish, game, and aquatic plant resources. Structure The Department ...
had successfully installed and maintained beaver pipes in 46 dams. In 1978, the
New York State Department of Environmental Conservation The New York State Department of Environmental Conservation (informally referred to as NYSDEC, DEC, EnCon or NYSENCON) is a department of New York state government. The department guides and regulates the conservation, improvement, and protection ...
began designing and testing various culvert protection devices, of which the T-culvert guard was the most effective and cost-beneficial. In 1992,
Clemson University Clemson University () is a public land-grant research university in Clemson, South Carolina. Founded in 1889, Clemson is the second-largest university in the student population in South Carolina. For the fall 2019 semester, the university enr ...
developed the Clemson Beaver Pond Leveler, a device that prevented beavers from damming areas of concern by directing water through existing dams using a strategically designed pipe system. Over the years, these designs have been modified and improved in order to address flow problems that occur in a variety of different landscapes. The most recent innovations in flow devices combine fencing techniques which exclude beaver with pipe systems which do deceive beavers.


Contemporary flow devices


Beaver dam pipes

Beavers diligently plug leaks in their dams because their survival depends upon the cover provided by the water in their pond. If a beaver can detect the flow of pond water into a pipe, it will plug the pipe with mud and sticks. To be successful, a beaver dam pipe must eliminate the sound and feel of water flowing into the pipe. Successful pipe designs (e.g. Flexible Pond Leveler, Castor Master, Clemson Pond Leveler) achieve this by protecting the intake end of the pipe with a cylindrical fence enclosure. A beaver swimming along the outside of the fence enclosure is unable to hear or feel the flow of water into the pipe and cannot reach it to block it. The pond level is controlled by the height of the pipe in the dam. Since beavers depend on water for their survival, the more a beaver pond is lowered with a pipe, the more likely it is that the beavers will try to build a new dam to return the water to its previous high level. In addition, the more a beaver pond is lowered, the more valuable wetland acreage is lost. Therefore, it is important to lower a beaver pond only enough to resolve the threat to human health, safety, or property.


Culvert protection

A culvert pipe under a road is a common target for beaver damming because the constriction speeds up the current and may resemble a hole in a dam. With a little work, a beaver can quickly plug a culvert with mud and sticks, and turn the entire roadbed into a large dam. Highway Departments often spend significant amounts of time and money repeatedly clearing beaver dams from culverts.


Culvert protective fences

The Beaver Deceiver (a trapezoidal shaped culvert fence) was invented by Skip Lisle in the 1990s while working for the Penobscot Indian Nation in
Maine Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and nor ...
. It is very effective at completely eliminating beaver damming of a culvert. It works in three ways. First, the perimeter of the trapezoidal fence is typically 40 – 50 feet long, making it difficult for a beaver to dam the entire fence. Second, as beavers try to dam the culvert, the fence forces them to dam in a direction away from the culvert, which is not in their nature. Third, as they dam farther out on the fence, the opening of the stream into which it flows gets wider. Therefore, the damming stimuli of the sound and feel of moving water decrease the farther they dam on the fence. If the sides of the fence are at least 12 feet long, the beavers will generally leave the fence alone. To be effective, however, a culvert fence must be surrounded by enough water that the beavers will need to dam the entire fence perimeter. In areas where the stream bed is narrow rather than wide, the fence must be narrow so that it is surrounded by water. Being narrow loses one advantage of the trapezoidal shape, but it can still deter beavers from damming the culvert. Since beavers are excellent diggers, a fence floor is usually needed to prevent beaver tunneling under the fence. The fence walls need only be 24 inches above the water line since beavers do not climb.


Fence and pipe culvert system

Combining a small culvert Fence with a Pond Leveler Pipe is another effective method to protect culverts from beaver damming. The culvert fence is made small enough to encourage the beavers to dam on it, but the resulting pond is prevented from rising to a dangerous level by a Pond Leveler Pipe installed through the culvert fence. The Fence and Pipe flow device needs very little maintenance and limits where and how high the beavers can dam; however, to be most effective, the intake end of the pipe should usually sit in at least 3 feet of water. When this water depth is not possible, a simple Culvert Protective Fence may be the best option.


See also

*
North American beaver The North American beaver (''Castor canadensis'') is one of two extant beaver species, along with the Eurasian beaver (''Castor fiber''). It is native to North America and introduced in South America ( Patagonia) and Europe (primarily Finland ...
*
Martinez beavers The Martinez beavers are a family of North American beavers living in Alhambra Creek in downtown Martinez, California. Best known as the longtime home of famed 19th/20th-century naturalist John Muir, Martinez has become a national example of urb ...
*
Beaver dam A beaver dam or beaver impoundment is a dam built by beavers to create a pond which protects against predators such as coyotes, wolves and bears, and holds their food during winter. These structures modify the natural environment in such a way t ...


References


External links


Worth a Dam non-profit foundation for beaver education


{{DEFAULTSORT:Flow Device Beavers Fur trade