Features and impacts of currents and waves on sediment resuspension in a large shallow lake in China
2018
Ding, Wenhao | Wu, Tingfeng | Qin, Boqiang | Lin, Yingtien | Wang, Han
Wind-induced hydrodynamics are important forcing mechanisms of sediment resuspension in lakes. However, the relative contributions of wind-induced waves and currents on sediment resuspension during a wind event remain unclear. This study used high-frequency sensors to investigate the effects of wind waves, lake currents, and shear stress on sediment resuspension under different wind conditions (10 September to 17 October 2017) in Lake Taihu (China). Measurements showed that wind speed varied from 0.3 to 11.5 m/s, wave height varied from 0.035 to 0.46 m, lake current speed ranged from 0.001 to 0.39 m/s, and turbidity changed from 36.5 to 158.7 NTU. Sediment resuspension resulted primarily from wave- and current-induced shear stresses. Calculation showed these quantities varied in the range 0.045–0.338 and 0.002–0.127 N/m², respectively. Total shear stress showed positive correlation with turbidity. Wave-induced shear stress contributed more than 60% of the total. Waves and currents have different responses to wind. During periods of increasing turbidity, the percentage of wave-induced shear stress was initially high (> 85%) before decreasing with the development of the current. During periods of decreasing turbidity, the percentage of wave-derived shear stress declined initially before increasing with the decrease of current speed. The results showed a clear process regarding the contributions of shear stress from waves and currents during different stages of hydrodynamic development, which could be used to describe sediment resuspension in large shallow lakes that would help in the development of high-efficiency sediment resuspension models.
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