The Application of the Vetiver System in Erosion Control and Stabilization for Highways Construction and Maintenance in Thailand

Abstract: Since 1993, The Vetiver System (VS) has been applied both in construction and maintenance projects of mountain roads in the Northern, Northeastern, and Southern regions of Thailand. Over 2.5 million slips are planted each year. The Department of Highways (1994) has prepared a Standard Drawing [SP-204 1994 and SP-206 (Revision) 1999, “ Vetiver grass planting for highway slope protection”] that consists of detail of the pattern of planting on back slope, side slope and bridge slope. The drawing covers planting at high erosible area, side ditch lining, bank protection. It also includes suitable slips, hole digging and ground preparation, planting, period for plant, planting caring, leaf trimming and fertilizing application. This drawing is used as a guideline in development of other engineering departments. The VS plays an importance role and replaces other techniques for erosion control, and solves highway slopes damage caused by erosion or scouring at the curved section of road, surface slope, the end of surface drainage systems and toe slope. Vetiver slips have been planted depending on the seriousness and tendency of erosion. Their growth on side slope was usually better than back slope. Slips were obtained from: The Highway District’s multiplication plots, Land Development Department and other agencies. Polybagged slips kept in the nursery are recommended and fertilizer should be applied at the bottom of the planting holes. The VS has been proven and accepted to be an effective and low-cost technique for erosion protection in roadworks, suitable for a sustainable economy with limited budget. Some defects of the vetiver planting in the roadworks are found in the Northern region of the country where some local weeds grow more rapidly than the vetiver. So, in the first year, more care is needed. Suitable period for planting is limited in the rainy season that is not correlated well with construction that takes place in dry season