1 Influence of vegetation density and projected area on streambank hydraulics

Vegetation along the toe of a streambank can slow down water and deflect flow away from banks, altering the forces applied to the bank surface and protecting banks against erosion. Five flume experiments were used to explore how changes in vegetation planform density (number of plants/horizontal area) and projected area (number of leaves/vertical area) influence channel velocity and turbulent kinetic energy (TKE) on a 30 ° vegetated bank toe at three discharge rates. Increased vegetation density and projected area reduced bank toe streamwise velocities by>34 % and increased main channel streamwise velocities by 50-75%. Higher projected area increased turbulence, especially along the bank toe-channel margin interface where turbulence increased five-fold. Results from this study indicate the importance of considering plant density and projected area when studying resistance and turbulence on vegetated banks