Observations of the effect of emergent vegetation on sediment resuspension under unidirectional currents and waves

Abstract. We present results from a series of laboratory experiments on a wave and current flume, where synchronous velocity and concentration measurements were acquired within arrays of rigid cylinders, representative of emergent vegetation and benthic communities, under different flow conditions. The density of an array of rigid cylinders protruding through a sandy bed affects the velocity field, sediment motion and resuspension thresholds when subjected to both unidirectional currents and regular waves. We compare the measured resuspension thresholds against predictions of sediment motion on non-obstructed flows over sandy beds. The results show that even if flow speeds are significantly reduced within the array, the coherent flow structures and turbulence generated within the array can enhance sediment resuspension depending on the population density.