Delineating suspended sediment concentration patterns in surface waters of the Changjiang Estuary by remote sensing analysis

Three Landsat TM imageries (taken on 18 May 1987, 4 August 1998 and 28 July 2007) were used as the data source to identify the spatial and temporal variations of the suspended sediment concentration (SSC) in surface waters of the Changjiang Estuary. Atmospheric correction was carried out to determine the water-leaving reflectance using the FLAASH module. A regression equation between surveyed SSC and suspended sediment index was chosen to retrieve the SSC from the Landsat TM images. In addition, tidal harmonic analysis was performed to calculate tidal conditions corresponding to the acquisition time of satellite images. The results show that the SSC spatial patterns are similar to the in situ observation results, which show the highest SSC in the region of turbidity maximum zone in the Changjiang Estuary. For the period of 1987 to 2007, the SSC pattern is controlled mainly by tidal dynamic conditions and wind speeds, rather than sediment discharges from the river.