Impact of Land Reclamation on Coastal Water in a Semi-Enclosed Bay

Abstract

Land reclamation has a profound impact on coastal environments. On the Chinese coast, the new Xiang’an International Airport has been built on newly reclaimed land. The impact of the massive land reclamation project (finished in 2018) on water quality and coast conditions in a nearby semi-enclosed bay is investigated using remotely sensed data. Factors affecting surface water quality and coast conditions are further analyzed using multiple regression. All water quality and coast condition indices show no long-term trend from 2005 to 2021. The suspended solid concentration (with a maximum value of 96.11 mg/L) is much lower than the threshold of 188 mg/L. When considering variations in sediment concentration, the probability that the concentration reaches the threshold is less than 1×10−6%; therefore, suspended solids have little threat to the local oyster-growing industry. The trend of dissolved inorganic nitrogen concentration is steady, implying little alteration to nutrient circulation in the semi-enclosed bay. Within the observation timeframe of 2005–2021, a recent sedimentation trend (surrogated by the normalized difference water index) appears after 2018 but it needs to be confirmed by a longer observation. Statistical models based on multiple regression highlight the following links: (1) the sediment source is outside the bay, (2) the overland runoff from newly claimed land dilutes nutrient concentrations, and (3) the coast conditions are mainly affected by tides and rainfall. Neither actively reclaimed or cumulative reclaimed areas form a direct causal relationship to water quality or coast conditions in the semi-enclosed bay.