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

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.