SPRING-NEAP CHANGE IN TIDAL HYDRODYNAMICS IN THE LINGDINGYANG BAY OF THE PEARL RIVER DELTA, China

Understanding the evolution of estuarine hydrodynamics is essential for sustainable water resources management, since they directly link to estuarine environment by regulating the materials transportation (e.g. nutrients, sediments, organisms and pollutants). In this study, an enhanced harmonic analysis model for nonstationary tide (S_TIDE model) was used to extract the amplitudes and phases of two predominant tidal constituents (M₂ and K₁) in a daily scale in two tidal gauging stations (i.e., Chiwan, Sishengwei) in the Lingdingyang Bay of the Pearl River Delta from 1965 to 2016, with the purpose of exploring the spring-neap change in tidal hydrodynamics (e.g., tidal wave celerity and tidal damping/amplification rate). To understand the stepwise evolution of tidal hydrodynamics, we have divided the whole study period into three distinct periods: the pre-human (e.g., from 1965-1997), transitional (e.g., from 1998-2007) and post-human periods (e.g., from 2008-2016), based on the dynamics of wave celerity. It was shown that the long-term spring-neap change in tidal hydrodynamics was mainly driven by the highly-modified geometry (including deepening and narrowing) in the Lingdingyang Bay. To quantify the effects of estuarine morphological alterations in terms of deepening and narrowing on tidal hydrodynamics, an analytical hydrodynamics model was adopted to assess the spring-neap variations at different periods. The proposed method for evaluating the tidal dynamics owing to morphological changes is particularly useful for providing a theoretical guideline for protecting the estuarian environment in the Lingdingyang Bay and other estuaries that are subject to strong human interventions.