1、 Guidelines for Vegetation Managementii 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law. 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is
2、 a violation of applicable law.iiiExEcutiVE coMMittEE20102011Voting MembersOfficers:President: Susan Martinovich, NevadaVice President: Kirk Steudle, MichiganSecretary-Treasurer: Carlos Braceras, UtahRegional Representatives:REGION I: George Campbell, New Hampshire, One-Year TermBeverley Swaim-Stale
3、y, Maryland, Two-Year TermREGION II: Mike Hancock, Kentucky, One-Year TermH. B. “Buck” Limehouse, South Carolina, Two-Year TermREGION III: Thomas K. Sorel, Minnesota, One-Year TermVacant, Two-Year TermREGION IV: Amadeo Saenz, Jr., Texas, One-Year TermFrancis G. Ziegler, North Dakota, Two-Year TermNo
4、n-Voting MembersImmediate Past President: Larry L. “Butch” Brown, MississippiAASHTO Executive Director: John Horsley, Washington, DC 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.Guidelines for Vegetat
5、ion ManagementivSubcoMMittEE on MaintEnancE20102011Chair: Carlos Braceras, UtahVice Chair: Robert “Chris” Christopher, P.E., WashingtonSecretary: Celso Gatchalian, FHWA Liaison: Steve Olson, AASHTOStatE MEMbErSalabaMa G. Mike Harper George H. Conner, P.E. Ronald D. Pruitt alaSka Michael Coffey arizo
6、na Lonnie D. Hendrix Marwan Aouad Dennis G. Halachoff arkanSaS Tony Sullivan Emanuel Banks california Steve Takigawa Alan R. Mills colorado David C. Wieder, P.E.connEcticut Robert P. Mongillo Richard Baron dElawarE Alastair Probert diStrict ofcoluMbia Mesfin Lakew Aaron Horton florida Tim Lattner GE
7、orGia Eric Pitts Keith Golden, P.E. Rachel Brown Hawaii John Williams idaHo Brent Jennings, P.E. Steve Spoor illinoiS Aaron Weatherholt, P.E.indiana Todd Shields iowa Bob Younie, P.E.kanSaS Roy D. Rissky, P.E. Peter Carttar, P.E. Tim D. Cunningham kEntucky Nancy B. Albright louiSiana Gill M. Gautrea
8、u Janice P. Williams, P.E. William Drake Jr.MainE Michael E. Burns Brian T. Burne John E. Buxton David Bernhardt, P.E.Maryland Russell A. Yurek MaSSacHuSEttS Thomas Loughlin, P.E. Ron Dionne MicHiGan Jon W. Reincke, P.E.MinnESota Steven M. Lund MinnESota Susan J. Lodahl ,P.E.MiSSiSSippi John D. Vanc
9、e Celina Sumrall MiSSouri Don Hillis, P.E. James Carney Montana Jon Swartz nEbraSka Michael T. Mattison, P.E. Craig R. Lind nEVada Richard J. Nelson, P.E. William Hoffman, P.E.nEw HaMpSHirE Caleb B. Dobbins, P.E. Douglas Gosling nEw JErSEy William Carter nEw MExico Dennis Ortiz nEw york Peter Weykam
10、p nortH carolina Lacy D. Love, P.E. Jennifer P. Brandenburg, P.E. Dan Holderman nortH dakota Brad Darr oHio David Ray, P.E., P.S. Halle Jones Capers, P.E., S.I.T.oklaHoMa Kevin S. Bloss Tom Wadley orEGon Lucinda M. Moore pEnnSylVania Daryl R. St. Clair W. James Smith Charles C. Goodhart puErto rico
11、Jorge A. Vega-BarriosrHodE iSland Paul R. Annarummo SoutH carolina James J. Feda SoutH dakota Ed Rodgers, P.E. Jason Humphrey 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.vtEnnESSEE Joe Holt Greg Dunc
12、an Chris Harris tExaS Toribio Garza utaH Carlos Braceras Richard L. Clarke, P.E. Steven J. McCarthy, P.E.VErMont Scott A. Rogers Wayne Gammell, P.E.VirGinia Erle W. Potter Anwar S. Ahmad, P.E., C.E.M.Robert E. Prezioso, P.E.waSHinGton Robert “Chris” Christopher, P.E.wESt VirGinia Steven B. Cole, P.E
13、.wiSconSin David I. Vieth Thomas R. Lorfeld wiSconSin John Kinar, P.E.wyoMinG Ken L. Shultz, P.E.u.S dot MEMbEr fHwa Eugene Hoelker Wade Casey Christopher Newman Paul Pisano William Beatty Steve Mueller Peter Kopac Mike Moravec Celso Gatchalian aSSociatE MEMbErintErnational britiSH coluMbia Rodney C
14、hapman nEw brunSwick Kenneth Connell noVa Scotia Bruce Fitzner ontario Jeff Baker SaSkatcHEwan Brent Marjerison, P.E.otHErtrb Frank Lisle Jr., P.E. Amir N. Hanna ChairJohn W. RowenVegetation make rubbish removal difficult; and cause, after heavy rains, rubbish and debris to accumulate and block drai
15、ns, flooding the road and making travel unsafe.Reduces Driver Fatigue with Variety of Changing AestheticsDriver fatigue is a major contributor to road accidents. Anything that can reduce driver fatigue will reduce roadside accidents. Landscaping and vegetation has been shown to reduce driver frustra
16、tion and fatigue (22, 300). Ulrich (1979) found that plants increased positive feelings and reduced fear and anger.Reduces Fire Potential at Pavements EdgeC.C. Wilson (1979) found that 75 percent of all wildfires occur within 10 feet of a road before spreading to grass-land and forestland. R.F. John
17、son (1963) (307) reported that over 52 percent of man-made fires in California occurred within 33 feet of a road edge. Other studies showed similar results, reinforcing the correlation between roads and wildfire (California Division of Forestry and USDA Forest Service, 1968 245). Dry vegetation pres
18、ents a fire hazard when allowed to grow too close to the travel lane. Wilson (1979) also found that a reduction of fuel (dry vegetation) within the first 10 feet of a roadside greatly reduced the incidence of fire; especially since ignition sources abound, such as tossed cigarette butts, backfiring
19、vehicles, hot exhaust pipes, or a shower of sparks from metal objects scouring the road surface. The fuel source (high and dry grass) and subsequent potential for fire can be reduced through an effective vegetation management program. Roads and well maintained roadsides can provide valuable fuel bre
20、aks in fire-prone regions. Bare ground and low growing grass reduce fire intensity, and physical separations of tree crowns prevent fires from spreading at the crown level. These factors improve fire fighter safety and reduce the potential for fires to spread across roads. An increase in width of ba
21、re ground and mowed recovery zones have been used by state Departments of Transportation (DOTs) and the U.S. Forest Service as effective fuel breaks. Roads, especially when the roadsides have been treated as fuel breaks, are a preferred location from which to start backfires, often the safest and mo
22、st successful method of stopping intense fires. 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.4-3chapter 4objectives of roadside Vegetation Management4.2 EconomicsA well-cared-for neighborhood can incr
23、ease property values, keep neighbors happy, reduce costly complaints, and aid business by encouraging travelers to return. An interview-based survey of business owners found that trees and landscaping in neighborhood commercial districts created a pleasant space that attracts people; acts as an outd
24、oor extension of the business customer service commitment; and can help to develop a distinctive identity for and de-fine the boundaries of a business district, thereby encouraging return visits (313).Without vegetation management, our roads would rapidly deteriorate. Effective vegetation management
25、 practices decrease damage to facilities and structures and reduce maintenance costs. Roadside vegetation management plans support transportation agency efforts to maintain roads and highways at their lowest life-cycle cost. A healthy road-side environment also limits the liability of the governing
26、agency (129).All aspects of roadside vegetation management impact the economics of maintaining a road.Vegetation Management Reduces Liability from Visibility AccidentsA well-maintained roadside will increase the motorists reaction time and enable them to take evasive action from oncoming traffic, ve
27、hicles entering the roadway, animals such as deer, and roadside fixtures. Fewer accidents results in less litigation against agencies for negligence.Vegetation Management Reduces Maintenance CostsWell-planned, self-sustaining landscapes are easier to maintain and less costly. Sustainable landscapes
28、consist of locally adapted plants that can spread at their own rate to cover roadside areas. They help to reduce annual main-tenance costs and improve worker and public safety because they do not require more expensive mowing or even herbicide treatments.Vegetation Management Protects Highway Assets
29、Maintained vegetation keeps highway structures from sustaining vehicle hits, accidents, etc. In addition, roots from encroaching vegetation can penetrate and heave road surfaces, and cause failure of the road subsurface (14, 129). Roadside vegetation reduces costly erosion slides and slip out events
30、 on roadsides.4.3 Erosion controlThe most efficient and cost effective form of erosion control is prevention. The most cost effective, environmentally friendly, and aesthetically pleasing form of prevention is the use of vegetation. When properly installed and main-tained, vegetation can protect slo
31、pes by reducing erosion, strengthening soil, and inhibiting landslides by generally increasing slope stability. Vegetation is often a key factor in the management of stormwater (28, 37, 186).The use of vegetation to manage erosion and protect slopes is relatively inexpensive, does not require heavy
32、machin-ery on the slope, establishes wildlife habitat (155), and can improve the aesthetic quality of the roadside. 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.Guidelines for Vegetation Management4-4
33、Helps Maintain Integrity of Shoulder AreaThe roadside shoulder slope must be maintained to prevent the erosion and cracking of the roadway surface itself. Grass is the best and least expensive method of preventing erosion on slopes. The root structure of vegetation holds the soil together and the to
34、p-growth breaks up the speed and intensity of rainfall droplets and slows the movement of water across the slope.Prevents Guardrails from FailingWhen slopes erode behind rail posts they can fail to hold in place when struck by a vehicle, presenting a safety hazard and a potential lawsuit. In additio
35、n, it is costly to replace erosion damaged guardrails. The roots of vegetation keep slopes stable around guardrails and other fixtures. However, vegetation around guardrails needs to be maintained at a height low enough to allow for visibility and function of the guardrail.Preserves Stream BanksVege
36、tation will control runoff and reduce stream bank erosion. Established vegetation will cover slopes and prevent them from drying out and cracking, exposing them to future erosion events. Increasingly, vegetation management is part of new stream restoration techniques used to protect highways and bri
37、dges from erosion. Vegetation is often a key component in designs to slow water and limit or reduce scour.Prevents Drains from CloggingVegetation can limit debris from entering drain grates. Controlled vegetation around drain pipe outfalls will help prevent erosion.Helps Preserve WetlandsVegetation
38、management will limit runoff contaminating surrounding wetlands and help mitigate environmental wetland issues.4.4 EnvironmentalOwing to their relatively large area, road networks have a significant effect on the natural environment (88). State DOTs manage over 17 million acres of right-of-way, some
39、 of which contain rare ecosystems and endangered species (112, 114).Roadside management practices reflect the legislative obligations, economic pressures, and community values of the time. In the past, less consideration was given to the environmental value of roadside vegetation. Today, the environ
40、-ment is at the forefront of public concerns (Minnesota Department of Transportation, 2003) (165). Roadside vegetation can significantly improve the environment by improving water quality, managing stormwater, protecting the soil, in-creasing biodiversity, creating habitat for wildlife, and reducing
41、 the number of invasive weeds (Bedard et al., 2000) (11).Aids in Compliance of Runoff Water Quality RegulationsRegulations enacted by the Environmental Protection Agency (EPA), state agencies, or commissions often hold engineers liable for damage caused by stormwater runoff. Regulations usually requ
42、ire DOTs to maintain slopes for water quality and sediment control. Natural vegetation is the best and least expensive control measure that a DOT 2011 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.4-5chapte
43、r 4objectives of roadside Vegetation Managementcan use to meet regulations. There is a changing trend in land development and stormwater management through-out the United States. It has been called many things, including smart growth, conservation development, and low impact development (LID). LID i
44、s alternative, ecologically sensitive design that mimics the way natural areas store and infiltrate rainwater. The LID approach protects local and regional water quality by decentralizing stormwater management and absorbing rainfall throughout the landscape. Low impact development minimizes the amou
45、nt of impervious surfaces and mitigates the impact of necessary impervious surfaces. There are a variety of conservation practices that work together to mitigate these effects, such as pervious paving, rain gardens, bioretention cells, bioswales, native landscaping, and soil quality restoration. Bio
46、swales are sometimes a cost effective way to manage stormwater runoff. Bioswales are stormwater runoff conveyance systems that provide an alternative to storm sewers. They can absorb low flows or carry runoff from heavy rains and snowmelt to storm sewer inlets or directly to surface waters. Bioswale
47、s improve water quality by enhancing infiltration of the first flush of stormwater runoff and filtering the large storm flows they convey.Water, Air Quality, and Noise ControlVegetation can filter and provide cleaner water to streams and wetlands. Roadside vegetation absorbs the carbon dioxide that
48、contributes to global warming, as well as other gases that contribute to urban pollution. Trees combat global warming by absorbing the carbon emitted by vehicles, lowering carbon emissions from fossil fuel-burning plants, and reducing the energy used for climate control in buildings. One tree can re
49、move 26 pounds of carbon dioxide from the atmosphere annually, equaling 11,000 miles of car emissions. Landscape plants, including shrubs and turf, remove smoke, dust, and other pollutants from the air. One study showed that 1 acre of trees has the ability to remove 13 tons of particles and gases annually (291).Vegetation can absorb sound waves, and significantly reduce unwanted “noise pollution” from traffic and other man made sources of noise. Additionally, in the presence of a breeze, some tre
