Long-Term Geomorphological Evolution of the Mouth Bar in the Modaomen Estuary of the Pearl River over the Last 55 Years (1964–2019)

Zhiyuan Han,Bing Yan,Huaiyuan Li,Mingxiao Xie,Hualiang Xie

doi:10.3390/w14010090

Abstract

Based on mass bathymetric data and remote sensing data in the Modaomen Estuary, this study explored the long-term evolutionary characteristics of the mouth bar in the Modaomen Estuary of the Pearl River from 1964 to 2019. In the past 55 years, due to the impact of human activities, such as shoal reclamation and estuarine regulation in the Modaomen Estuary, the river mouth moved out of the shallow sea covered by several islands and faced the South China Sea directly. Therefore, the mouth bay became a siltation center in the estuarine region and expanded outwards, gradually evolving a geomorphic pattern with three shallow shoals and two distributary branches; a west branch as the main branch accompanied by a small east branch. Over the past decade, high-intensity sand dredging activities in the mouth bar have led to a considerable deepening of the water depth and a significant refinement of bed sediments, forming a discharge pattern of a wide and shallow channel flowing into the sea. Therefore, the evolutionary characteristics of the mouth bar have become abnormal in recent years, so additional field bathymetric data and hydrological data are required for further research regarding the subsequent evolution of the mouth bar, against the background of a significant reduction of sediment discharge and high-intensity human activities.

Highlights

Estuarine regions with strong land–ocean interactions are complicated; usually affected by fluvial dynamics, tidal dynamics, wave dynamics, and morphological evolution; the ecological environment of such regions is sensitive and fragile [1,2,3]
This study explored the long-tern morphological evolution of the mouth bar in the Modaomen Estuary of the Pearl River from 1964 to 2019
In the last 55 years, due to the impact of human activities, such as shoal reclamation and estuarine regulation in the Modaomen Estuary, the river mouth moved out of the shallow sea covered by several rock islands and faced the South China Sea directly

Summary

Introduction

Estuarine regions with strong land–ocean interactions are complicated; usually affected by fluvial dynamics, tidal dynamics, wave dynamics, and morphological evolution; the ecological environment of such regions is sensitive and fragile [1,2,3]. With the development of the estuarine regions, human activities, such as upstream dam construction, large-scale land reclamation in estuarine shoals, sand dredging, as well as the construction of ports, navigation channels, and sea-crossing bridges, have notably altered the river discharge and sediment input, underwater topography, wave and tidal dynamic conditions. The morphological evolution of the mouth bar, which is influenced by runoff, tides, waves, sea-level rise, storm surge, and human activities, is an important research topic regarding land–ocean interactions in the coastal zone (LOICZ) [4,5,18]. The research topic involves estuarine regulation, navigation development, water resources management, and other fields [19,20,21,22]

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Conclusion