The role of vegetation on streambed instability

An experimental campaign in a laboratory flume is performed in order to study the streambed instability phenomena in channels with randomly-distributed vegetation, varying vegetation density, diameter, and height and flow conditions. The morphology of the sediments bed is captured with the photogrammetry technique and a Laser Scanner, and its modifications with the vegetation and flow conditions are investigated. The results suggest that the vegetation influences in promoting the streambed stability and the formation of multiple bars. In runs with few vegetation elements, the sediment bedload is primarily in the longitudinal direction. By increasing the vegetation elements, the bed structures become shorter than before, but with a similar trend. The presence of submerged vegetation instead of emergent vegetation leads to the formation of a higher number of isolated structures in bed morphology. Thin vegetation has a lower impact on bed modification as compared to thick vegetation. In addition, a lateral dispersion of sediments is observed in the runs with low flow discharge.