Posted by Duncan Page on Wed, Dec 02, 2009
According to Wikipedia "drift fences were used in the Texas Panhandle from 1882 to 1887 to control cattle drift, the winter migration of livestock to warmer territory." In an effort to prevent cattle in Oklahoma, Colorado, and Kansas from crossing into the state during blizzards, Texas ranchers built a barbed wire drift fence that stretched for 200 miles with a gate every three miles.
The drift fence prevented cattle from migrating to better grazing land during the heavy snows of the 1886-87 winter. Most froze to death along the fence. It was removed in 1890 after passage of a law prohibiting fencing of public property.
Drift fences are still in use today but the application has changed. The long continuous barriers are one of the most effective techniques to sample wildlife species in a particular area to learn such things as population density. Reptiles and amphibians, insects and small mammals are often the subjects studied. When the animals come upon the fence, they move along looking for an opening. Many can be captured in a single night, when many species are most active and hard to observe.
Different materials are used to make the fences. They can be strategically placed in areas with different ecosystems where wildlife movement is most active. Depending on the location, metal flashing or silt fence might be used. Various types of traps, such as pitfall and funnel, are used along the fence to capture subjects. Hundreds can be collected in a single night.
Drift fence is an example of a type of fence that retains the original name while its application has changed over the years. Can you think of other examples?
Posted by Duncan Page on Mon, Nov 23, 2009
In early 1999, four women's bras were attached to a wire fence along a road in rural New Zealand. The local land owner left the bras on the fence. News spread and The Cardrona Bra Fence quickly became a controversial tourist attraction. By the end of February 60 bras had been hung.
Shortly thereafter someone took on the task of removing all the bras from the fencing. The local press got wind of the story and the news spread throughout New Zealand. Bras soon began to reappear on the fence. By October 2000 the total number of bras reached 200.
Once again all the bras were removed. When this was reported by the press the news spread far beyond the shores of New Zealand. The Cardrona Valley now had a genuine tourist attraction. Not only did people come in person to hang bras, but also people sent bras from other areas to be hung. By 2006 the number of bras on the fence approached 800.
The Cardrona Bra Fence received mixed reviews from the local population. Some saw it as a potential hazard, distracting motorists. Some considered it a tourist attraction, bringing people to the area. Others felt strongly that it was a blot on the rural landscape. Some even claimed that the fence might offend visitors from other cultures.
In April of 2006, after several legal attempts to have all bras stripped from the fence, The Cardrona Bra Fence was declared a "traffic hazard" and an "eyesore". By September, when the local council finally took action, 1,500 were removed. The fence itself is still in place. Without its bras, some may now look upon it as a naked fence.
How would you feel about a bra fence being in your area?
Would you see it as an "eyesore"?
Would you welcome it as an unconventional tourist attraction?
Posted by Duncan Page on Tue, Nov 10, 2009
New types of security fencing are currently being developed and evaluated. One type is called "floating" fence. There are two different "floating" fences - one for use on land and the other one on water.
Floating fencing on land
A 15 foot high fence stretches along a seven mile section of the US-Mexico border in the Imperial County sand dunes between Calexico, California and Yuma, Arizona. This particular area is subject to drifting sand which causes changes in the topography.
Built at a cost of $40 million, the unique floating fencing is designed to be unfastened to anything below the sand's surface. When drifting sand starts to bury the fence line, sections can be lifted up by a machine and placed back on top of the sand allowing the 15 foot height to be maintained. New fencing does not have to be erected. Known as the "floating fortress" and "sand dragon", this new fence design is credited with reducing not only illegal immigrants but also drug smuggling.
See a picture of the floating fence.
Floating fencing on water
The other type of "floating" fence is being used by the US Navy as way of protecting ships from terrorist attacks. Termed a "Waterfront Force Protection Barrier System", over 30 kilometers of floating fences have been successfully installed around Navy installations.
The floating fence, capable of stopping high speed boats, is adapted from a fixed security barrier system. The fencing consists of independent 35 to 50 foot modules that are connected to each other. Pontoons support a steel structure. Vertical steel nets, usually 9 feet tall, are secured to this structure and sit on cylindrical shaped floats that form the actual fence. Variations in currents and tidal ranges up to 30 feet are accommodated. Gates are incorporated into the design as required.
Read the PDF about floating fences from Harbor Offshore Barriers, Inc.
Can you think of other situations where either of these fences could be of use? Do you think they're cost effective?
Posted by Duncan Page on Mon, Nov 02, 2009
In April of 1976, after four years of planning and obtaining required permits and permission, construction began on an unusual fence. Completed on September 10, Christo and Jeanne-Claude's "Running Fence" was removed, leaving no traces, fourteen days later on September 23rd.
The 18 foot high fence was made with 2,222,222 square feet of heavy woven white nylon fabric. It wound for 24-1/2 miles through the rolling hills of Sonoma and Marin counties in northern California, terminating in the Pacific Ocean in Bodega Bay. The Running Fence crossed 14 roads and the town of Valley Ford. Openings were left for cars, people, cattle and wildlife. It was placed so that it could be viewed from 40 miles of public roads, as shown in this old super 8 movie.
350,000 hooks were used to attach the top and bottom edges of the heavy fabric to steel cables. The cables were secured to 2,050 - 3-1/2"x21' tubular steel posts set 36" in the ground. Posts were not set in concrete. 90 miles of cable and 14,000 earth anchors were used to laterally brace the posts. Close to 400 people helped install the fence. After its removal, all material was given to the ranchers who allowed it to pass through their property.
In addition to the materials used, all paid for by Christo and Jeanne-Claude, this monumental art project consisted of:
- 18 public hearings
- participation of local ranchers
- 42 months of collaborative efforts
- drafting a 450 page Environmental impact Report
- three sessions of the Superior Courts of California
- temporary use of hills, the Pacific Ocean and the sky
The project elicited strong reactions.
Do you think this is a work of art?
Posted by Duncan Page on Mon, Oct 26, 2009
Living fencing can be an alternative to conventional wire, wood, vinyl and masonry fences. As noted in David Beaulieu's excellent article "Living Walls as Privacy Fences", living fencing has certain advantages:
- lower cost
- more attractive
- fruit production
- reduces traffic noise
- seasonal foliage variation
- provides a habitat for birds and small animals
- sometimes less restricted by zoning regulations
- can be pruned and sculpted into different shapes
Living fences make excellent privacy screens around your property. Planting a thicket of small trees or shrubs creates an effective barrier. Flowering bushes, deciduous and evergreen shrubs can be planted. The type of plants used will determine the height, width and appearance of the fence. How they are planted will determine the visual and physical tightness of the barrier. If necessary, a conventional fence can also be used to keep pets and children in the yard. A living fence can also be used around smaller areas in the yard such as patios.
Living snow fences can also be a great alternative to plastic or wood snow fencing. The design will determine downwind snow distribution. A dense multiple row living snow fence will pile snow in a restricted area, reducing the need to plow highways and driveways. To make windbreak for the uniform distribution of snow across a field, a single row of tall deciduous trees can be spaced 15 to 20 feet apart. Snow will be distributed to a distance of 10 to 15 times the height of the trees.
The following articles about living snow fences are very informative:
Have you ever considered planting a living fence?
Would living snow fencing be a solution that would work for you?