Sediment particle selectivity and its response to overland flow hydraulics within grass strips
2020
Luo, Mingjie | Pan, Chengzhong | Cui, Yongsheng | Wu, Yun | Liu, Chunlei
Particle selectivity plays an important role in clarifying sediment transport processes in vegetative filter strips (VFS). 10‐m long grass strips at slopes of 5° and 15° were subjected to a series of sediment‐laden inflows experiments with different particle sizes to investigate the sediment transport and its response to overland flow hydraulics. The inflow sediments came from local soil, river‐bed sand, and mixed, with median particle size d₅₀ of 39.9, 207.9 and 77.4 μm, respectively. Three independent repeated experiments were carried for each treatment. The results show that when the sediment trapping lasted for a certain length of time, the re‐entrainment of some small‐sized particles was greater than the deposition; that is, net loss occurred, which was not erosion of the original soil. Net loss of particles is mainly determined by the particle diameter. The coarser the inflow sediment particles and/or the steeper the slope, the coarser the particles can be net lost. Deposited sediment causes the VFS bed surface to become smooth and hydraulic resistance decrease exponentially. Unit stream power P is more suitable than shear stress τ of overland flow to be used to describe the process of sediment particle transport in VFS. The relationship between P and d₅₀ of outflow sediment is very consistent with the form of power function with a constant term. These results are helpful to understand the physical process of sediment transport on vegetation hillslopes.
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