Vetiver grass hedges for erosion control on a cropped flood plain: Hedge hydraulics

Abstract

Vetiver grass is a tall perennial tussock grass from Asia which has been 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-retarding and sediment-trapping capability. In this paper, trials aimed at a quantitative description of the hydraulic characteristics of stiff vetiver grass hedges are described. Three hedges were planted across a large outdoor flume, perpendicular to the flow. Trials were conducted at various discharges and depths. The discharge and the depths upstream and downstream of each hedge were recorded. From these data a hydraulic relationship was developed between the depths and the discharge. Finally, this relationship was used to calculate the maximum vetiver grass hedge spacing required to control soil erosion on a cultivated flood plain of low slope subject to overland flow.