Waves-waves collide induced by different wind directions caused high exchanged in the water level at the open area Shallow Lake, China

Abstract

Wind from different directions induce waves-waves to collid at the central zone of Taihu Lake. It causes exchange in water bodies and release of internal nutrients which increases algal bloom. This study aims to analyz the impact of the interactions between waves-waves collision from different directions and different sources such as traveling ships and explored factors, causing sediment resuspension. The results were achieved to collect high-frequency data for measuring wind speeds, currents, waves, and suspended solid concentration (SSCs). The results indicate that the water exchange and the turbidity highly escalated when wind speeds reached 5 m/s. The surface flow velocities are very high, about 80 cm/s or more according to the raw data after calibrating the instruments. This finding is very important in the processes of sediments dynamic. Maybe in these wide area, high waves-waves collide leading to constructive interference from different sources generate waves. Sediment processes were categorized into three period A, B, and C corresponding to three shear-stress thresholds. Period A: Sediment bottom particals was stable with τw < 0.01 N/m 2. It did not change through this period and the averaged suspended solid concentration (SSCs) was approximately 50 mg/L. Period B: Sediment resuspension was small with a range between 0.01 ≤ τw < 0.1 N/m 2. It jumped up slowly and the averaged was in the range of 50 to 70 mg/L. Period C: Sediment resuspension was moderate with shear stress 0.1 ≤ τw < 0.8 N/m 2. The form of the sediment bed was changed at the second period, this shows that increase of the shear stress activated the sediment in this period. The bottom SSCs increased quickly from 60 to 350 mg/L in average. Outcomes of this paper presents the main factor causing sediment resuspension, which may assist further studies and estimate the real reasons for internal nutrient release from different waves induced waves-waves to collide in Lake Taihu.