The Effect of Rigid Vegetation on the Sediment Transport Rate on the Coast
2021
Mirzakhani, Golnaz | GhanbariAdivi, Elham | Fattahi, Roohalla
Sedimen load is one of the important factors affecting the hydraulic performance and morphological structure of the beach. One of the solutions to reduce sediment transportation is vegetation as a bio system for sediment trapping. Vegetation due to flow obstruction and turbulence change, affects sediment transport. In this study, the effect of vegetation density on sediment transport rate along the shoreline was investigated. To consider this effect, beach and vegetation models were embedded in a knife edge flume equipped with a load cell and an Acoustic Doppler Velocimeter system (ADV). Experiments were performed in two triangular and rectangular layouts with a density of 12 to 273 stems per unit area. The results showed that by increasing the density of the vegetation and the number of tree rows, the sediment transfer rate decreases; So that in the highest density, the sediment transfer rate has increased up to 80% and in the lowest density this amount has reached 20%. Also, the triangular arrangement at the highest density was 25% and at the lowest density, it was 3% superior to the rectangular arrangement in reducing the sediment transfer rate. According to the variables studied in this investigation, density number changes have the greatest effect on sediment transfer rate, so that sediment transfer rate would decreases by increasing vegetation density. Through experimental formulas such as Kamphuis, Galvin, C.E.R.C and Van Der Meer, the obtained results were compared with the other studies.According to the statistical analyzes performed, the modified C.E.R.C formula would calculate the estimated sediment by a correlation coefficient of 92%.
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