Flow device
Encyclopedia
Flow devices are man-made solutions to beaver-related flooding problems. Traditional solutions have been focused on the trapping and removal of all the beavers in the 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 re-settlement by new beavers. Flow devices are relatively cost-effective, low maintenance solutions that regulate the water level of beaver dam
s and keep culvert
s open. A 2006 study by the Virginia Department of Transportation
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.
s which increases biodiversity and improves 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
, beavers create habitat for numerous other species, as exemplified by ponds created in Alhambra Creek
in Martinez, California
by a new beaver colony in 2007 which, in turn, lead to the return of numerous birds, steelhead trout (Oncorhynchus mykiss) and river otter (Lontra canadensis) in 2008, and mink
(Neovison vison) in 2009.
The most common beaver-related flooding issues that people encounter are caused by blocked road culverts or freestanding beaver dam
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.
Fish and Game Department had successfully installed and maintained beaver pipes in 46 dams. In 1978, the New York State Department of Environmental Conservation
began designing and testing various culvert protection devices, of which the T-culvert guard was most effective and cost-beneficial. In 1992, Clemson University
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.
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.
. 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 their nature.
Third, as they dam further out on the fence, the opening of the stream it is flowing into is getting wider. Therefore, the damming stimuli of the sound and feel of moving water decrease the further 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 streambed 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 always generally needed to prevent beaver tunneling under the fence. The fence walls only need to be 24 inches above the water line, since beavers do not climb.
Beaver dam
Beaver dams are dams built by beavers as protection against predators such as coyotes, wolves, and bears, and to provide easy access to food during winter. Beavers work at night and are prolific builders, carrying mud and stones with their fore-paws and timber between their teeth...
s and keep culvert
Culvert
A culvert is a device used to channel water. It may be used to allow water to pass underneath a road, railway, or embankment. Culverts can be made of many different materials; steel, polyvinyl chloride and concrete are the most common...
s open. A 2006 study by the Virginia Department of Transportation
Virginia Department of Transportation
The Virginia Department of Transportation is the agency of state government responsible for transportation in the state of Virginia in the United States. Headquartered in Downtown Richmond, VDOT is responsible for building, maintaining, and operating the roads, bridges and tunnels in the...
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 wetlandWetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
s which increases biodiversity and improves 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
Keystone species
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and...
, beavers create habitat for numerous other species, as exemplified by ponds created in Alhambra Creek
Alhambra Creek
Alhambra Creek is a stream in Contra Costa County, California in Northern California which drains into the Carquinez Strait by way of the historical Arroyo del Hambre. Alhambra Creek and its valley take their name from Cañada del Hambre, Spanish for "valley of hunger", apparently because of some...
in Martinez, California
Martinez, California
Martinez is a city and the county seat of Contra Costa County, California, United States. The population was 35,824 at the 2010 census. The downtown is notable for its large number of preserved old buildings...
by a new beaver colony in 2007 which, in turn, lead to the return of numerous birds, steelhead trout (Oncorhynchus mykiss) and river otter (Lontra canadensis) in 2008, and mink
American Mink
The American mink is a semi-aquatic species of Mustelid native to North America, though human intervention has expanded its range to many parts of Europe and South America. Because of this, it is classed as Least Concern by the IUCN. Since the extinction of the sea mink, the American mink is the...
(Neovison vison) in 2009.
The most common beaver-related flooding issues that people encounter are caused by blocked road culverts or freestanding beaver dam
Beaver dam
Beaver dams are dams built by beavers as protection against predators such as coyotes, wolves, and bears, and to provide easy access to food during winter. Beavers work at night and are prolific builders, carrying mud and stones with their fore-paws and timber between their teeth...
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 at the Northeastern Wildlife Conference as a solution for problem beaver ponds to control water levels. In 1963 Laramie reported that the New HampshireNew Hampshire
New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...
Fish and Game Department had successfully installed and maintained beaver pipes in 46 dams. In 1978, the New York State Department of Environmental Conservation
New York State Department of Environmental Conservation
The New York State Department of Environmental Conservation is responsible for the conservation, improvement, and protection of natural resources within the U.S. state of New York. It was founded in 1970, replacing the previous Conservation Department...
began designing and testing various culvert protection devices, of which the T-culvert guard was most effective and cost-beneficial. In 1992, Clemson University
Clemson University
Clemson University is an American public, coeducational, land-grant, sea-grant, research university located in Clemson, South Carolina, United States....
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.
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, as 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 MaineMaine
Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost...
. 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 their nature.
Third, as they dam further out on the fence, the opening of the stream it is flowing into is getting wider. Therefore, the damming stimuli of the sound and feel of moving water decrease the further 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 streambed 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 always generally needed to prevent beaver tunneling under the fence. The fence walls only need to be 24 inches above the water line, since beavers do not climb.