VETIVER GRASS HEDGES FOR EROSION CONTROL ON A CROPPED FLOOD-PLAIN - HEDGE HYDRAULICS

Vetiver grass is a tall perennial tussock grass from Asia which has be en used in a variety of soil conservation applications in that region, Interest in this grass outside Asia is increasing but its application is handicapped by a lack of quantitative knowledge of its flow-retard ing and sediment-trapping capability. In this paper, trials aimed at a quantitative description of the hydraulic characteristics of stiff ve tiver grass hedges are described. Three hedges were planted across a l arge outdoor flume, perpendicular to the flow. Trials were conducted a t various discharges and depths, The discharge and the depths upstream and downstream of each hedge were recorded, From these data a hydraul ic relationship was developed between the depths and the discharge. Fi nally, this relationship was used to calculate the maximum vetiver gra ss hedge spacing required to control soil erosion on a cultivated floo d plain of low slope subject to overland flow.