A thirteen-year record of bathymetric changes in the North Passage, Changjiang (Yangtze) estuary

The mouths of major rivers in the world have always been important waterways and as a result, subject to significant human intervention. Therefore, it is necessary to understand the coupling of natural processes and human intervention in the sediment movement and deposition to determine long-term morphodynamic evolution in the mouth regions of major rivers. A multivariate technique was used to analyze high-resolution bathymetric data from the North Passage of Changjiang (Yangtze River), which is the vital shipping channel in the mouth region and for the entire Changjiang waterway. Our findings show that there are two modes of bathymetric changes. The first mode represents 85% of the variability, which includes the deposition in the peripheral groin fields along the shipping channel and deepening of the shipping channel, which is primarily due to the channel maintenance. The second mode represents 6% of the variability of the river-mouth shoal (seaward migration and size reduction), attributable to the declining sediment discharge of the Changjiang due to the Three Gorges Dam, and the enhancement of the ebb flow as the result of dredging.