Dynamic Response of the Suspended Sediment Change in the Tidal Channel of Jiangsu Sea Area

Abstract

Taking the observed data of water and sediment of two tidal cycles during middle tide at 4# station of Dongdagang as an example, the thesis reveals the spectral relation and phase relation between the wavelet analysis signals in five layers about flow velocity, water depth, wind speed and sediment concentration in various layers in the tidal channel where 4# station is located using wavelet analysis in combination with maximum entropy power spectrum analysis, analyzes the signals about sediment concentration at different frequency bands in the tidal process in various layers of the water body and identifies their response and change mechanisms. There is complex response relation between suspended sediment concentration in the tidal channel and the change of wind speed, flow velocity as well as water depth. The change of suspended sediment concentration in the tidal channel relates to wind speed, flow velocity and water depth. Asymmetry of flood and ebb tidal currents, background sediment concentration in water body, flow turbulence, gravity action and response delayed effect have an impact on suspension and settlement process of suspended sediment at various layers in tidal dynamic process. Flow velocity, water depth and wind speed have different relative action on the change of suspended sediment concentration on different wavelet analysis layers. High-frequency change of sediment concentration mainly results from the change of flow velocity. From the view of spectral structure of wind speed and flow velocity, there is coupling response relation between wind speed and current and wind speed acts on the change of sediment concentration through impacting tidal current velocity and producing waves. Dynamic forcing and sediment concentration are not in linear correspondence, but characterized by nonlinearity.