Data_Yagci_Water_Resources_Research_2021

The present experimental study investigated how the growth of an isolated patch affected the local flow field and the scour pattern. The evolution of the vegetation patch was mimicked by considering an idealized case, in which a circular patch of rigid emergent stems becomes elongated, due to positive and negative feedbacks. The growth of the patch was simulated at three consecutive stages by aligning the different patches with the flow direction with a gradual decrease in density towards the downstream side. This variation in density was assumed to occur due to sediment and seedling deposition at different growth stages. The growth of the patch was considered to occur in three stages: (a) initial, (b) development, and (c) mature. Despite generally elongated obstacles are hydrodynamically favorable bodies, the morphometric analysis of the scoured bed obtained by laser scanner revealed that streamlined elongation of permeable patches amplifies global scour and it enhances localization of the local scour hole. Results also showed that as the vegetation patch grows, the steady-wake region of low velocity and suppressed turbulence that favors sediment entrapment becomes shorter, thus hindering the further expansion of the patch, indicating the existence of an ideal aspect ratio for vegetation patches. It was also seen that under the effect of the growth of the patch, in the wake region, vertical velocity distribution evidently deviates from the logarithmic velocity profile, and also near the bed region, flow recovers rapidly due to elevated bed-induced turbulence.