This study determines the effect of drag and lift forces for riparian grasses under different flow conditions
using a series of flume experiments. A novel installation is used to measure the lift force in the channel flow.
Flow changes the front projection area for the riparian grasses, so the drag and lift forces are linearly correlated with velocity. This correlation differs from that for a rigid object. However, as the Reynolds number increases, the front projection area, the drag coefficient and the lift coefficient gradually decrease and approach a constant value. The constant drag coefficient is found to be 0.6 (Re = 40,000) and the constant lift coefficient is 1.15 (Re = 24,000). At this stage, the characteristics of riparian grasses are similar to those for rigid objects, for which the lift coefficient reaches a constant value earlier than the drag coefficient.
Keywords: Riparian vegetation, drag coefficient, lift coefficient