30 Jun2003

Overstory #123 - Living Snow Fences

Written by SDA Natural Resources Conservation Service Idaho Resource Conservation and Development Association USDA National Agroforestry Center, Lincoln Nebraska.

Introduction

In many temperate regions, blowing and drifting snow jeopardizes public safety and emergency services, interrupts businesses, and increases livestock and wildlife mortality. Snowplows can keep roads open, but annual costs are often high. When roads are subject to recurring snow blockage, a more permanent, cost-effective solution is often needed.

Structural barriers, commonly made of slated or picket fences, are a proven technique for reducing the impact of blowing and drifting snow. These are placed to interrupt blowing snow. With an action similar to a rock placed in a flowing stream, they cause an eddy effect that alters wind speed and direction, allowing snow to settle out.

However, another kind of snow fence, made of living plant materials such as grasses, shrubs and trees, can also be used and has several advantages over man-made structures. Often called living snow fences, they are actually densely planted windbreaks that have been specifically designed and planted to reduce blowing and drifting snow. Like a structural barrier, they cause blowing snow to settle in a designated area. Living snow fences are more cost-effective than structural barriers and provide a wide array of benefits beyond snow control.

Benefits

Living snow fences offer a wide range of options and will meet many objectives. These benefits continue to improve and multiply as a living snow fence grows and matures:

Longevity
Cost-effectiveness
Reduced annual maintenance
Snow and dust containment
Wildlife habitat
Aesthetic enhancement

Advantages of living snow fences

Service life is estimated at 50 to 75 years. The estimated life of a man-made slat snow fence is 5 to 7 years; over a 50-year span, the installation and maintenance costs would be 4 times more than a living snow fence.
Average cost is $3 per mile per year for each unit of snow trapped compared to $185 per mile per year for a 4-foot slat fence.
More efficient in capturing snow. When mature, a living snow fence may capture up to 12 times more snow than a slated fence.
Provide habitat for birds to nest, eat, and escape. Small mammals--even deer--are attracted to the habitat created by a living snow fence.
Can be designed to conserve energy for farmsteads, feedlots, and community facilities.

Some disadvantages to consider

Living snow fences require more space than slat snow fences.
New plantings must be protected from grazing.
It takes from 5 to 7 years for living snow fences to provide effective snow control and 20 years to fully mature.
Site conditions such as shallow soils and pH (acidity or alkalinity) may prohibit plant establishment.
Living snow fences must be well planned and located to achieve the myriad of benefits they offer. For example, a snow fence located in the wrong place could cause snow to accumulate on the road instead of protecting it.

Ten steps to ensure success

Step 1: Determine planting objectives. Your objective may be as simple as the control of blowing and drifting snow-or more complex with multiple objectives such as providing livestock protection or wildlife habitat, enhancing the beauty of the landscape, or water harvest and storage.

Step 2: Take an inventory of all on-site physical factors, including:

- Annual precipitation, average snow volume to be stored
- Topography and aspect, distance upwind available for planting
- Soil type, fertility, depth, and pH
- Current and potential land uses, land ownership, easements, restrictions

Step 3: Determine planting stock needed by species and number and who will order them.

Step 4: Decide what site preparation work is needed and who will do it.

Step 5: Determine fertilizer needed. Most windbreaks and living snow fences are not fertilized unless a deficiency shows in the growth and foliage of the trees and shrubs.

Step 6: Determine type of irrigation system needed to ensure plant establishment and survival. An irrigation system will need to be considered in areas with less than 20 inches of annual precipitation.

Step 7: Determine fencing needed to protect young plants from grazing livestock or wildlife. Decide who will install and maintain it.

Step 8: Decide what kind of weed barrier or mulch will be used and who will install it. Growth rates are significantly faster when weed barrier is used. Newly planted trees can't compete with annual weeds and grasses so make plans for cultivation, chemical weed control or mulching.

Step 9: Plan for proper maintenance

- Frequent inspections of irrigation systems and fences to allow speedy repairs when needed.
- Frequent inspection of plants to spot weed and pest problems to allow quick remedial action.
- Prompt replacement of any dead plants.

Step 10: Make a plan by listing decisions made, date actions will need to take place, and who will carry out each action.

Who should be involved in planning?

Living snow fences often involve multiple landowners or jurisdictions that can make planning more complex. Involve key decision makers and partners early in the planning stages.

Possible partners include private landowners, county commissioners, county road departments, conservation districts, Resource Conservation and Development councils, State Department of Highways, State Department of Lands, State Forester, and federal, state, or local land managing agencies.

Living designs

Height, density, length, and plant protection are key elements in the proper functioning of a mature living snow fence. To avoid problems, carefully consider these factors during the design phase.

Height

Determine barrier height by the tallest row in a planting. Barrier height affects snowdrift depth and length. Snow storage potential can be manipulated by barrier height. Doubling the barrier height will increase snow storage by four times--an important economic factor to consider in species selection.

Density

Determine the density of a living snow fence by the species, number of rows, spacing between rows, and spacing of plants in a row. A 50 percent dense barrier stores the greatest amount of snow if other factors are equal. Between row spacing can vary depending on design criteria and objectives. Twin row high-density plantings are recommended. Preferred species are evergreens, shrubs, and low growing broadleaf trees.

Length

Length determines the maximum area that can be protected if winds are perpendicular to it. Snow storage at the ends of a barrier is significantly less than near the center. Barrier design must extend far enough beyond the protected area to intercept winds that deviate 25 degrees from either direction of perpendicular. Extending a snow fence 100 feet beyond the area to be protected will mitigate this "end effect."

Planting Protection

If livestock can access the site, then fencing will be necessary to plantings. Significant damage can occur from trampling, rubbing, and browsing. Fencing will avoid soil compaction as well as physical damage to the irrigation system and weed barrier.

Key design elements

Orient living snow fence at right angles to prevailing winter winds.
Doubling the height will more than quadruple the amount of snow captured.
Vegetation with about 50% Density will capture and store the greatest amount of snow.
Conifers are ideal species to plant because of their height and year-round foliage.
Many deciduous trees and shrubs also work well, especially in combination with conifers.
There are hundreds of site-specific design options

Plant selection

Use of site-adapted plant species is critical to the success of a living snow fence. Consult your local office of the Natural Resources Conservation Service or Cooperative Extension for site-specific recommendations. Some commonly recommended species include:

Evergreen

- Eastern red cedar, Austrian Pine, Blue Spruce
- Rocky Mountain juniper and Utah juniper are very drought hardy
- Scotch pine and Ponderosa pine on soils under 7.90 pH

Low Broadleafs

- Siberian crabapple, Mancharian crabapple
- Russian olive on upland sites only because species can spread in areas with high water tables

Shrubs

- Amur honeysuckle, Blueleaf honeysuckle, chokecherry, golden current, Peking cotoneaster, Western sandcherry
- American plum, common lilac, and silver buffaloberry can spread by suckering
- Fourwing saltbrush, Siberian peashrub (caragana), Skunkbush sumac and Sagebrush

Original source

This article was adapted with the kind permission of the authoring organizations from:

USDA Natural Resources Conservation Service, Idaho Resource Conservation and Development Association, and USDA National Agroforestry Center. 1999. Living Snow Fences. USDA National Agroforestry Center, Lincoln, Nebraska. Web: unl.edu/nac/pubs.html [June 2003]

About the authoring organizations

The Natural Resources Conservation Service (NRCS) is the US Department of Agriculture's lead conservation agency. No other Federal US agency speaks for the health and fate of America's private land. NRCS relies on many partners to help set conservation goals, work with people on the land, and provide assistance. Its partners include conservation districts, state and federal agencies, NRCS Earth Team volunteers, agricultural and environmental groups, and professional societies.

Idaho Resource Conservation and Development Association provides a mechanism for local and government partnership to identify and solve social, environmental, economic and human problems in Idaho. Activities address local problems by developing appropriate projects as solutions and by obtaining assistance from the private sector, corporations, foundations and all levels of government while strongly supporting and utilizing science and technology.

The USDA National Agroforestry Center (NAC) is a partnership of the USDA Forest Service, Research & Development (R&D) (Rocky Mountain Research Station), and State & Private Forestry (S&PF) and the USDA Natural Resources Conservation Service. The Center's purpose is to accelerate the development and application of agroforestry technologies to attain more economically, environmentally, and socially sustainable land-use systems. To accomplish its mission, the Center interacts with a national network of cooperators to conduct research, develop technologies and tools, establish demonstrations, and provide useful information to natural resource professionals.

Contact: National Agroforestry Center North 38th St. & East Campus Loop UNL-East Campus Lincoln, Nebraska 68583-0822 Tel: 402-437-5178.