Investigation of the impact of hydrodynamic conditions on sediment resuspension in shallow lakes

In this study, we sampled the original sediment columns from three points located in the eastern, central, and western areas of Chaohu Lake, and then investigated sediment resuspension under hydraulic disturbances in the laboratory. The results showed that when the hydraulic disturbance is weak and sediment surface shear stress is small (<0.02 N/m(2)), sediment surface layer moves alone. When the hydraulic disturbance is moderate and sediment surface shear stress is within a threshold (3.7 N/m(2)), only a small proportion of the surface sediments begins to move. However, when the hydraulic disturbance is further strengthened and sediment surface shear stress is larger than the threshold value, surface sediments move smoothly. By the experimental results, we found that the plankton layer is about 1 mm (1.56% of the maximum content of suspended matter (SSCmax)), which is the major contribution of individual sediment initiation. The new sediment layer is about 19-22 mm (20.9% of the SSCmax), which considerably affects sediment resuspension in shallow lakes. The consolidated layer is about 22 mm below the bed surface, which requires high shear stress and is hard to be transferred to the water column. The quantified experimental observation results are further verified with the theoretical results.

Automated summary

This study investigated sediment resuspension under hydraulic disturbances by sampling sediment columns from different points in Chaohu Lake and conducting laboratory experiments. The results showed that the response of the sediment surface to hydraulic disturbances varied depending on the strength of the disturbance and sediment surface shear stress. The plankton layer and the new sediment layer were found to play important roles in sediment resuspension.