Analysis of Tidal Prism Evolution and Characteristics of the Lingdingyang Bay at Pearl River Estuary

Abstract

Tidal prism is a rather sensitive factor of the estuarine ecological environment. The historical evolution of the Lingdingyang water area and its shoreline were analyzed. By using remote sensing data, the evolution of the water area of the bay was also calculated in the past 30 years. Due to reclamation, the water area was greatly decreased during that period, and the most serious decrease occurred between 1988 and 1995. Through establishing the two-dimensional mathematical model of the Pearl River estuary, the tidal prism of the Lingdingyang bay has been calculated and analyzed. The hybrid finite analytic method of fully implicit scheme was adopted in the mathematical model’s dispersion and calculation. The results were verified though the method of combining the field hydrographic data and empirical formula calculation. The results showed that the main tidal entrance of the bay is the Lingdingyang entrance, which accounts for about 87.7% of the total tidal prism, while Hong Kong’s Anshidun waterway accounts for only 12.3% or so. Combining the numerical simulations and the historical evolution analysis of the water area and tidal prism, and compared with that in 1978, it showed that the tidal prism of the bay was greatly decreased, and the reduced area was mainly the inner Lingdingyang bay, which accounted for 88.4% of the whole shrunken areas. As weakening trends of the tidal powers of the medium and neap tides are obvious, the tidal prism is decreased during the medium and neap is larger than that during the spring.