The differences in morphological development between the intertidal flats of the Eastern and Western Scheldt

Abstract

Human interventions have a large impact on estuarine morphology. The intertidal flats in the Eastern Scheldt and Western Scheldt estuaries (The Netherlands) have faced substantial morphological changes over the past decades. These changes are thought to be caused by human interventions, such as the construction of the storm surge barrier in the mouth of the Eastern Scheldt, and the deepening of the navigation channels of the Western Scheldt. This paper analyses several datasets and numerical simulations of hydrodynamics, providing an overview of the various morphological characteristics of the intertidal flats in the two estuaries over time and space. Apart from the volume, area and average height of these areas, also the integral steepness of each flat is quantified based on its full geometry. The analyses focus on the intertidal flats surrounded by water, which allows for a robust comparison between the different flats. The intertidal flats in the Western Scheldt appear to be substantially steeper compared to those in the Eastern Scheldt. The data indicates that a larger average height of a flat is related to a larger steepness. Despite variations in the evolution of the different flats, distinct characteristics of both estuaries are observed. An opposed trend is identified over time: the flats in the Western Scheldt have mainly increased in height, whereas the flats in the Eastern Scheldt have lowered after the completion of the storm surge barrier. This opposing development is associated with differences in tidal flow velocities in the estuaries, which are the result of human interventions.