Abstract
Abstract. Assessing the impacts of both natural (e.g. tidal forcing from the ocean) and human-induced changes (e.g. dredging for navigation and land reclamation) on estuarine morphology is particularly important for the protection and management of the estuarine environment. In this study, a novel analytical approach is proposed for the assessment of estuarine morphological evolution in terms of tidally averaged depth on the basis of the observed water levels along the estuary. The key lies in deriving a relationship between wave celerity and tidal damping or amplification. For given observed water levels at two gauging stations, it is possible to have a first estimation of both wave celerity (distance divided by tidal travelling time) and tidal damping or amplification rate (tidal range difference divided by distance), which can then be used to predict the morphological changes via an inverse analytical model for tidal hydrodynamics. The proposed method is applied to the Lingdingyang Bay of the Pearl River Estuary, located on the southern coast of China, to analyse the historical development of the tidal hydrodynamics and morphological evolution. The analytical results show surprisingly good correspondence with observed water depth and volume in this system. The merit of the proposed method is that it provides a simple approach for understanding the decadal evolution of the estuarine morphology through the use of observed water levels, which are usually available and can be easily measured.
Highlights
Understanding the morphological changes in estuaries due to natural processes and human interventions is especially important with regard to sustainable water management and ecological impacts on the estuarine environment (Prandle, 2004; Schuttelaars et al, 2013; Winterwerp and Wang, 2013; Wang et al, 2015; Hoitink et al, 2017; Luan et al, 2017)
If tidal damping and wave speed are known from observations, analytical models can be used to estimate the unknown tidally averaged depth and other tidal dynamics. Following this line of thought, the main objective of this study is to provide an analytical framework to assess the morphological evolution of estuaries based on the tidally averaged depth derived from the observed tidal hydrodynamics
The observed wave celerity is derived from the travelling time of both high and low water levels, while the tidal damping rate is computed according to Eq (27)
Summary
Understanding the morphological changes in estuaries due to natural processes and human interventions is especially important with regard to sustainable water management and ecological impacts on the estuarine environment (Prandle, 2004; Schuttelaars et al, 2013; Winterwerp and Wang, 2013; Wang et al, 2015; Hoitink et al, 2017; Luan et al, 2017). It is noted that these highresolution and successive field data are rare or unavailable in most estuaries, especially because the determination of detailed morphological changes is usually time and energy consuming. The development of a simple yet effective approach for the assessment of decadal morphological evolution without the need for bathymetric data collection is desirable, which is especially the case for ungauged basins (Gisen and Savenije, 2015)
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