Long-term morphodynamic evolution of the Pearl River Delta from the perspective of energy flux and dissipation changes

Abstract

The Pearl River Delta (PRD) is an extremely complex, large-scale estuary system in China. In this study, a long-term process-based morphodynamic model was developed to investigate the characteristics of variations in energy flux and dissipation and their evolution alongside the hydrodynamic and topographic evolution of the PRD since the Holocene transgression maximum. The results show that the evolution of the dynamics and topography of the PRD are largely influenced by the geological and geomorphological structures of the region. Energy flux and dissipation in the inner estuary exhibited a patchy distribution, with areas of high energy flux appearing in deep troughs, near headlands, and in gorges containing bedrock islands, and areas of relatively small energy flux appearing in the flow shadow zones of the islands, tidal fluctuation confluence area, and shoals. Corresponding to the energy flux distribution, sediment accumulation also exhibited a high degree of spatial and temporal variability. The evolution of the coastline of the PRD is not driven from north to south, or from the river outlet to the downstream area. Rather, multiple deposition bodies simultaneously developed in the north and south without overlapping. With the deposition of sediment in the estuary, the isoamplitude lines of tidal waves were gradually extrapolated and the spatial distribution gradually shifted from the northwest to the southwest. This indicates the mutual transformation between the estuarine river and tidal power, and also reflects the development characteristics of the river system.