Sheet flow measurement in the north passage of Yangtze estuary with pedestal based synchronous field survey system

Abstract

In order to measure sheet flow near the bottom in the north passage of Yangtze Estuary during the typhoon, a submerged synchronous field survey system composited of Nortek AquaPro, Nortem AquaPro HR, AWAC and OBS 3+ was equipped on a pedestal based structure. The system was used to survey sheet flow field during the flooding season in 2015. The pedestal base synchronous field survey system can give reasonable estimation about stability of itself, and also capture simultaneously the wave climate as well as the current feature and the sediment concentration near the bottom. Analyzing the data collected by the system, it is found that the tidal current dominates the sedimentation concentration near the bottom in the Yangtze Estuary without waves, and the only peak value of suspended sediment concentration occurs at the fall slack time. The suspended sediment concentration above 50cm to the bottom is usually not larger than 15kg/m³, and it is not significantly correlated with the wave. When typhoon happens, the suspended sediment concentration increases significantly below 30cm to the bottom. There are two peaks of the suspended sediment concentration at the spring slack and the fall slack time respectively.