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?