Variation mechanisms of suspended sediment concentration in complex estuary determined through remote sensing, observation and modeling coupling

Abstract

Suspended sediments are vital indicators of water quality, so understanding the dynamic processes and influence factors of suspended sediment concentration (SSC) is crucial in estuaries or coastal waters. This study presents a comprehensive strategy for coupling several methods of remote sensing, field observation, and numerical simulation to systematically study spatio-temporal variability of suspended sediment in the Liao River Estuary (LRE) and Daliao River Estuary (DLRE), and then driving forces are analyzed. The SSC retrieval algorithm is suitable to interpret the dynamic SSC changes in shallow and turbid waters of the LRE and the DLRE. The results indicated that the SSC is higher during the muximum period of flood and ebb tide velocities but lower near the periods of flood and ebb slacks. SSC of the LRE and the DLRE is higher in spring tide cycle than that in neap tide under similar wind conditions. Wind conditions and waves caused by wind markedly influenced the SSC distribution in the LRE and the DLRE. Specifically, continuous turbidity zones are often formed due to sediment resuspension caused by larger bed shear stress under the action of strong southwest winds. The effect of river discharge on SSC in dry season is almost negligible in these study regions, and the river discharge during wet season leads to an increase of SSC. These results provide a fresh perspective on the complex sedimentary processes in estuary waters.