Windblown snow, sand, and dust can create hazardous driving conditions by reducing visibility and forming drifts on roadways to block or impede traffic movement. Blowing snow also causes icy roads, which are a major cause of vehicle accidents. Blowing snow also causes significant problems on railroads by forming drifts that block the passage of trains where tracks pass through cuts in hills, and by clogging switches and interfering with the operation of electronic sensors for detecting over-heated journals and dragging equipment.
To alleviate the problems created by blowing and drifting snow, snow control devices in the form of snow fences and other structures have been used for many years. A snow fence causes the wind-borne snow crystals or particles to settle out of the wind in a protected or sheltered area other than at a critical area, such as a roadway or railroad tracks where snow accumulation is not wanted.
The typical construction of a snow fence is a two-dimensional panel with a series of slots, holes or openings formed through the panel to create porosity. The snow fence creates aerodynamic drag and alters the structure of the turbulence which slows the velocity of the wind and diminishes its capacity to carry snow. In addition, a porous snow fence reduces the scale of turbulence by breaking up large eddies into smaller ones. These effects on the airflow allow the suspended particles to settle out and accumulate in the protected area which is sheltered by the snow fence. In the case of a porous fence, most of this deposition occurs on the downwind side of the barrier or panel. By positioning the snow fence far enough away from the roadway, the snow settles out of the wind at the sheltered or protected area, so the wind is relatively free of snow at the adjoining critical area. However, because the wind will pick up additional snow particles by blowing over expanses of snow-covered ground, the snow fence and its protected area must be close enough to the critical area to prevent the wind from accumulating snow again before reaching the critical area. Otherwise, the placement of the snow fence will be ineffective in preventing snow accumulation on the roadway or critical area.
Typically, the panels of a snow fence are assembled in long continuous rows. Long continuous rows of the artificial panel structures are usually necessary to achieve the best snow and windblown particle control effects over relatively long expanses of critical areas such as roadways and railroad tracks. The panels are typically constructed of wood planks and/or steel or plastic sheeting. Posts or triangular support frame structures anchor the panels to the ground and hold them upright to confront and withstand the forces from the wind. Because of their relative massive, complex and sturdy nature, conventional snow fences are usually built in place at the location of use. The bulky nature of the materials used to construct such snow fences usually makes their fabrication a time-consuming exercise. In addition to being bulky, the construction materials are usually expensive and difficult to transport to the construction site of the snow fence. The typical end result of constructing such snow fences is a collection of immobile, expensive and artificial structures which are visually obtrusive and aesthetically objectionable in a natural environment.
While it is theoretically possible to remove the snow fences during the seasons of the year when they are not needed, and thereby avoid the objectionable environmental obtrusion during some parts of the year, the cost of dismantling a typical snow fence and reassembling the snow fence when or where it is needed, becomes a predominant deterrent, resulting in the snow fence remaining in place on a year-around basis. The same considerations apply with respect to moving those snow fences which have not been placed in an optimal position to prevent snow from drifting and accumulating in the critical area. Empirical experience may be required to obtain the optimal placement of a snow fence.
The cost of dismantling a snow fence is approximately the same as the considerable cost of fabricating the snow fence in the first place. Then, the dismantled snow fence must be reconstructed, again at a further cost approximately equal to the original fabrication cost. The time required to dismantle a snow fence may be slightly less than the time required to fabricate the snow fence in the first instance, but the time requirements are nevertheless considerable and significant. The relatively permanent posts and anchoring structures used to hold the snow fence panels to the ground are usually not removable, even though the panels which create the aerodynamic effects might be removed from the anchoring posts and structures.
Even ignoring the substantial expense and time required to disassemble a conventional snow fence, the relatively large amount of bulky material from which the snow fence is fabricated must be stored until the time when the snow fence is again reassembled. The amount of material and the transportation costs of those materials between the site of use and the storage location creates additional problems and difficulties. The amount of space required to stow the numerous and bulky constituent materials of a typical wooden panel snow fence is substantial. Use of that space for storage constitutes an additional cost associated with disassembling a snow fence and is therefore an added detriment to dismantling conventional snow fence during those times of the year when it is not needed.
Because of the negative impacts of the cost, obtrusiveness, fabrication, dismantlement, removal and storage issues described above, previous artificial snow fences and windblown particle control structures have not been used on a prevalent basis for other beneficial purposes such as accumulating snow in agricultural fields to increase the soil moisture content for growing crops, retaining the topsoil against wind erosion, or shielding immature plants from the shear stress of wind and from the rapid evaporation of soil moisture at their critical early-growth stages. These and other potentially beneficial uses of windblown particle control devices would become more prevalent if the costs of the windblown particle control devices were reduced to enable the more cost-effective uses of such control devices over large expanses of the agricultural fields, and if such control devices could be fabricated and dismantled on a convenient, cost-effective and efficient basis. Dismantling such control devices and removing them from agricultural fields is essential after stable plant growth has been established to permit harvesting the crops, among other things.
Many other disadvantages associated with the deployment of snow fences and windblown particle control devices are known and appreciated. The disadvantages associated with the use of conventional snow fences have led to the significant improvements of the present invention.