Morphodynamic Behavior of Modaomen, Pearl River Estuary, South China

The morphodynamics in estuaries reflect the interaction among runoff, wave and tidal current-driven sediment transport and and will significantly influence the behavior of shoal and channel. However, the driving mechanisms around estuarine deltas and channel are complex, making it difficult to understand the role they play within estuarine morphodynamic evolution systems. Here, recent morphodynamic evolution of Modaomen Estuary (ME), one of the estuaries of the Pearl River Deltas (PRD), and associated controlling factors were analyzed based on unique Landsat satellite imagery, high-resolution surveyed bathymetry data, and situ hydrographic measurements. The results indicate that the ME have pronounced temporal and spatial dynamic, in which the bathymetric is relatively balanced with barely deposition and erosion before 1990s while overall erosion was found thereafter, and this phenomenon will be further aggravated due to the reduction of sediment transport rate. Meanwhile, the outer channels are also suffered remarkable morphological evolution. Before 1990s, there is only a single waterway to transport upstream material entering PRD, but since 2000 it diverted to be a bifurcation channel including western channel and eastern channel. Recently, the eastern channel gradually fade away so that the bifurcation channel diverted to be a single waterway again (i.e., western channel), and meanwhile this remaining channel exhibits an anticlockwise migration. Furthermore, the estuary channel exhibits a cyclic behavior over its long term history. According to the currently estuarine dynamic characteristics, we proposed a model of sediment bypassing and associated shifts to better understand the future channel migration at ME. Overall, the results provide useful guidance for planning of the navigation channels aligning and estuary management in this area.

Keywords: Morphodynamic behavior; Driving mechanisms; Channel migration; Modaomen.