Experimental study on the spatial traits of sedimentation driven by discontinuous nearshore vegetation patches

Abstract

In the rivers, the growth of aquatic plants from initial individual patches to elongated formations, and subsequent merging with the downstream or adjacent patches, is intricately linked to the spatial pattern of sediment deposition. Understanding the mechanism of suspended load deposition influenced by these plant patches is crucial. Therefore, we conducted experimental investigations into the spatial traits of sedimentation driven by discontinuous nearshore vegetation patches and its relationship with flow rates and vegetation density. The results indicate that, although the limited length of discontinuous vegetation patches restricts the development of coherent vortices at the interface, both fast and slow currents were observed, similarly to scenarios with continuous vegetation. Additionally, a unidirectional suspended loads transport from vegetation regions to the main channel was observed, contributing to the minimal sedimentation within the vegetation region originating from the main channel. However, the sedimentation in the retention zones, where is formed by the blocking and sheltering effects of discontinuous vegetation patches, was found to be most pronounced, approximately 1.5 to 3 times higher than in patch regions and main channels, which ascribes to longer retention time and the weaker turbulence in retention zones compared to the main channel and the vegetation region. The velocity differential between the main channel and vegetation region increases with greater flow rates, leading to the greater difference in the total deposition in the several typical areas: the vegetation region, the interval region, and the main channel. The positive correlation between the sedimentation spatial heterogeneity and flow rates was observed and quantified by the normalized standard deviation of the total deposition. These findings suggest that vegetation-mediated sediment trapping, alongside associated interval regions, generates distinct spatial patterns of sedimentation, which plays a crucial role in facilitating the longitudinal growth of vegetation patches downstream, ultimately contributing to the establishment of continuous nearshore vegetation zones. These findings provide insights into the potential applications of vegetation patches, particularly in river ecosystem restoration and water resource management.