Study of back-silting strength in the north passage channel of Changjiang Estuary

Temporal and spatial variations of the back-silting strength in the north passage channel of Changjiang Estuary are investigated using the empirical orthogonal function （EOF） method, with the aim to determine the imposed processes and time-scales. Data on back-silting quantity in every dredging unit of the channel have been collected since March 2000,predominantly once 15 d. The EOF analysis of the back-silting strength reveals two significant modes, which totally explain 58.33% of the overall variance, and the corresponding processes and time-scales. The first EOF mode shows a clear annual cycle which is determined by the riverine water and sediment discharge from the upstream. The second EOF mode reveals a close relation between the back-silting strength and project activities. Because the processes are greatly interrelated in this study case, the other EOF modes accounting for 41.67% of the total variance do not show clear processes and time-scales.