Sand fences are structures designed to manage the movement of natural elements such as sand and snow, shaping landscapes and protecting human infrastructure. These barriers are strategically placed to influence wind patterns, encouraging the accumulation of airborne particles in desired locations. Their general purpose involves controlling erosion and stabilizing dynamic environments like coastlines and arid regions.
What Are Sand Fences?
Sand fences are permeable barriers that resemble slatted walls, designed to manage the movement of sand and snow. These fences are not solid, allowing some air to pass through them. This porous design is a defining characteristic, differentiating them from solid walls that would merely deflect wind and its carried particles. Common materials used in their construction include thin wooden slats, synthetic fabrics, plastic mesh, or even bamboo. The wooden slats are often connected by twisted wire and attached to wooden or metal stakes. While some designs use perforated plastic sheets, traditional wooden slat fences are frequently preferred for coastal applications.
How Sand Fences Work
The functionality of sand fences relies on their permeable design to alter wind dynamics. As wind carrying sand or snow encounters a sand fence, its velocity is significantly reduced on the leeward side of the barrier. This reduction in wind speed causes suspended sand or snow particles to lose momentum and fall, accumulating to form or rebuild dunes or drifts directly in front of and behind the fence. The spaces between the slats or the porosity of the fabric allow some wind to pass through, which is crucial for the deposition process. This permeability prevents the fence from becoming quickly buried, enabling continuous accumulation. Over time, this process leads to the formation or reinforcement of natural barriers.
Common Applications of Sand Fences
Sand fences are widely utilized across various environments to address specific challenges posed by wind-driven sand and snow. In coastal areas, they are frequently employed for dune restoration and shoreline protection. By trapping windblown sand, these fences help to build new dunes or bolster existing ones, which then act as natural buffers against storm surges and high tides, protecting inland properties. In arid or desert regions, sand fences prevent sand encroachment on infrastructure, keeping roads, railways, and agricultural lands clear from drifting sand. These fences act as windbreaks, mitigating the movement of sand across open, sandy areas, and during winter months, they also function as snow drift control measures. They reduce wind velocity to cause snow to accumulate in desired locations, keeping roads and other infrastructure clear.
Placement and Types of Sand Fences
The effectiveness of sand fences depends on their strategic placement and design. Generally, fences are erected perpendicular or nearly perpendicular to the prevailing wind direction to maximize sand or snow trapping. Their height typically ranges from 2 to 4 feet, though taller fences of 4 to 6 feet may be used in areas with higher wind velocities; for optimal sand deposition, fences often have a porosity, or open space, of around 50%. Different types of sand fences exist, primarily distinguished by their material and configuration. Traditional wood slat fences are common, featuring thin wooden pickets wired together; other materials include plastic mesh or synthetic fabric barriers. Some designs involve single lines parallel to the shoreline, while others use double rows, zigzag patterns, or lines with perpendicular spurs to create wider dunes or trap sand from multiple directions.