A Study on the Influence of Submergence Ratio on the Transport of Suspended Sediment in a Partially Vegetated Channel Flow. Issue 3 (8th March 2023)

• Record Type: Journal Article
• Authors: Wang, Mingyang; Mi, Shuo; Avital, Eldad; Li, Na; Chen, Yuejun; Williams, John
• Is Part Of: Water resources research. Volume 59:Issue 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-08
• Subjects: suspended sediment transport -- submergence ratio (SR) -- submerged vegetation flow -- turbulent structures -- probability density function (PDF) -- particle vertical suspension; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2022WR032876
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: Riparian or aquatic vegetation thrives with seasons. The understanding of canopies' Submergence‐Ratio (SR = stem height/water depth) influence on suspended sediment transport is still limited. Thus, Large Eddy Simulations coupled with the Discrete Phase Method are used to investigate the particles' three‐dimensional distribution in a partially vegetated straight channel. The spanwise distribution of particles are quantified by the probability density function (PDF), showing a non‐uniformity of particles in time as quantified by the PDF variance. We found that (a) with SR rising, the particles' depletion effects exerted by the vegetation‐side mixing layer is improved along the interface between vegetated and vegetation‐side bare channel region. However, the SR has little effect on the variance of the particles' PDF in the spanwise direction when the mixing layer is fully developed. (b) During the developing stage of the over‐canopy mixing layer, submerged vegetation with higher SR gains a stronger upwards (vertical) entrainment capability. The case (SR = 60%) has a higher sediment concentration than other cases in the fully developed vertical mixing layer region over canopy. (c) The vertical suspension of particles in the vegetation‐side bare channel region is analyzed. Particles migrating from the vegetated region are entrained into the vegetation‐side bare channel region by turbulent structures. Nevertheless, the vertical concentration profile is more uniform in the vegetated region than in the vegetation‐side bare channel at the same streamwise location. The cases SR = 40% and 60% still have higher sediment concentration than other cases in the vegetation‐side bare channel's upper region. Plain Language Summary: Rivers are the blood vessels of the Earth, constantly transporting water, sediments, biomes, etc., and constantly shaping the surface of the Earth. The vegetation in the river, through its physical, chemical and biological functions, has a profound impact on the river's role in transporting sediment. In different seasons of the year, the water level of rivers and the height of aquatic plants change. The purpose of this study is to reveal the effect of the height of vegetation relative to water depth on the movement of sediment particles in water flow. The UK national high‐performance computer was used to carry out high‐fidelity simulations of sediment transport in a straight with partially vegetated covered channel. We found that the increase of the relative height of the vegetation highly influence the distribution of the particles in the spanwise of the channel. In the present vegetation condition, the sparse vegetation whose height is slightly over the half flow depth promote higher sediment concentration in the high location of the channel flow (away from the channel bottom) than other vegetation height conditions in the vegetated region. Interestingly, the sediment concentration in the vegetation‐side bare channel region almost has the same characteristics, namely, vegetation with half water depth have the strongest ability to improve the sediment concentration in the upper region of the bare channel flow. The results of this research are very beneficial for green ecological management of river sediment and the management of sediment deposition in key sections of rivers. Key Points: Relationship between submergence ratio and sediment's transport is investigated for vegetated and non‐vegetated bare channel regions Case Submergence Ratio (SR) = 60% has higher normalized concentration than other cases (such as SR = 20%, 40%, and 80%) in the upper layer of a fully developed vertical mixing layer Vertical suspension of particles in the non‐vegetated bare channel region occurs due to presence of riparian vegetation along the channel