Impact of Anthropogenic Activities and Sea Level Rise on a Lagoon System: Model and Field Observations

Cuiping Kuang,Huaming Zhan,Wei Zhao,Xin Cong,Qingping Zou,Zhichao Dong

doi:10.3390/jmse9121393

Abstract

The long-term geomorphological evolution of a coastal lagoon is driven by hydrodynamic forcing and is influenced by climate changes and human activities. In this study, a numerical model of the Qilihai lagoon (QL) system was established based on field measurements, previous hydrology data and satellite remote sensing measurements, to simulate the geomorphological evolution of QL from 1900 to 2018. The influences of sea level rise, runoff and human activities on the evolution of geomorphology were investigated. The results of the model show that the construction projects including the tide gate, the bridge, reclamation and the straightening or widening of the tidal channel increased the net deposition within the QL system. Furthermore, the spatial distribution of tidal asymmetry during the natural time period was similar to that of the change in bed thickness. However, bed erosion or deposition was not only dependent on tidal asymmetry but it was also affected by the external sediment supply and the discharge of upstream rivers. Moreover, sea level rise had a significant effect on the tidal asymmetry; therefore, it enhanced the accumulation of sediments in the QL system, while runoff had little effect on the tidal asymmetry or geomorphological changes in the system.

Highlights

Coastal lagoons are highly productive coastal systems in the transitional area between ocean and land that provide a range of ecosystem services and habitats for many species that society values [1,2,3,4]
2018was was simulated assess impact of sea level rise, runoff and human activities and the mechanism of erosion impact of sea level rise, runoff and human activities and the mechanism of erosion and deposition was examined in relation to tidal asymmetry, which provides a reference for the sediment transport mechanism and geomorphological evolution of other lagoons in the global region
Under the influences of sea level and runoff discharge, the lagoon stayed in a slight deposition state, while the tidal creeks were eroded slowly and the increased river discharge could intensify the erosion in tidal creeks

Summary

Introduction

Coastal lagoons are highly productive coastal systems in the transitional area between ocean and land that provide a range of ecosystem services and habitats for many species that society values [1,2,3,4]. Geomorphological evolution of lagoon is determined by terrestrial and marine sediment transport driven by hydrodynamic forces which can be wave-dominated and tide-dominated [10,11]. The spatial distribution of sediment is mainly dictated by the asymmetrical structure of flow induced by runoff, tide and wave. Because coastal areas are densely populated and vital ecosystems are at the same time important for biodiversity [12], extensive human interventions, including reclamation and tidal gate and bridge construction have occurred in the lagoon and other coastal zones

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