The Green and the White
Addressing these safety concerns, combined with cost sav-ings, environmental stewardship and highway beautification, the Iowa Department of Transportation's (DOT) living snow-fence program has shown amazing results over its more than 40-year development. These windbreaks may reduce the amount of plowing needed, increasing safety by increasing visibility and keeping snow off the roadway, while also providing wildlife habi-tat and controlling erosion. Additional safety benefits were recently shown in research done in Wyoming. This testing showed pavement temperatures were higher in areas pro-tected by snowfence when compared to unprotected sites. For states like Iowa that have severe winter weather, the ability to preserve higher pavement temperatures is critical to the effectiveness of salt and other chemicals used to combat the formation of ice on the roadway. Iowa's long-standing living snowfence program, both on and off of the right-of-way, consists of planting a combina-tion of trees and shrubs that serve as a windbreak, along with native grasses that help form a snow catch area for blowing and drifting snow. Iowa DOT project fund are used for living snowfence projects on highway rights-of-way. The rows are five feet apart and the shrubs are three feet apart within the row. The rows are staggered so the plant in one row fills the gap between plants in the adjacent row. With this spacing, Iowa DOT research has shown that the drifts downwind from these plantings will occur up to 10 to 12 times the heights of the shrubs. So by using 10-foot tall shrubs, the snow drifts will form up to 100 to 120 feet down-wind. Using its own The research also shows that the more open or porous the snowfence, the longer and shallower the drifts. Conversely, the more dense the snowfence, the resultant drifts are shorter and deeper. This information can be used to tailor a design to control the shape and length of the drift. The Iowa DOT partners with the Iowa Department of Natu-ral Resources (DNR) on many living snowfence projects in highway rights of way. Iowa DOT Chief Landscape Architect Mark Masteller says, For many projects, the agency is able to use plants from the Iowa DNR's nursery stock. This reduces costs for the DOT, giving it more miles of snowfence for the dollar, he says. We see the benefit in increased highway safety and reduced maintenance and the Iowa DNR sees increases in habitat for native songbirds, insects and small mammals, Masteller says. It's a program that works for both agencies. It's a program that works for both agencies. Working with the Iowa DNR's nursery stock and planting different plant species during the development process has 32 November 2009 Better Roads ApplicationsInnovations& S weeping winds during winter weather can cause dangerous conditions for motorists with greatly reduced visibility due to blowing snow and treacherous drifts if no wind protection is provided on rural sections of roadway. Natural Barriers: Living Fences Block Blowing Snow By Tracey Bramble, Iowa DOT