Abstract
The impact of tide-induced morphological changes and water level variations on the sediment transport in a tidally dominated system has been investigated using the numerical model Delft3D and South-East England as a test case. The goal of this manuscript is to explore the long-term changes in morphology due to sea level rise and the large-scale morphodynamic equilibrium of the South-East England. Our results suggest that the long term (century scale) tidally-induced morphological evolution of the seabed slows down in time and promotes a vanishing net transport across the large scale system. Century-scale morphologically updated simulations show that both morphological changes and net transport values tend to decrease in time as the system attains a dynamic equilibrium configuration. Results further suggest that the presence of a gradual increase in mean sea level accelerates the initial morphological evolution of the system whose morphological rate of change gradually attains, however, same plateau values as in the absence of sea level rise. Given the same base morphology, increasing water levels enhance residual currents and the net transport near the coastline; and vice-versa, decreasing sea levels minimize both residuals and net transport near the coastline. The areas that are more affected by, water level and morphological changes, are the ones where the net transport is the highest. This manuscript explores and allows extending the idea of morphodynamic equilibrium at a regional scale, larger than the one for which this concept has been generally explored i.e., estuarine scale.
Highlights
A large part of the world’s coastline is threatened by human and environmental changes, such as urbanization, sea level rise, and possible increase in storm activity [1,2]
Tidal dynamics strongly impact the fate and transport of sediments, contaminants, and the morphological evolution of these environments, which prompts the continuous attention to the complex interaction between tidal motion, and sedimentary processes
The tides interact with the variable bathymetry leading to the creation of complex residual flow and residual sediment transport due to varying topography, bottom friction, and tidal asymmetries
Summary
A large part of the world’s coastline is threatened by human and environmental changes, such as urbanization, sea level rise, and possible increase in storm activity [1,2]. The authors investigated the existence of a long term equilibrium or quasi-equilibrium, for tide-dominated channels and well-mixed estuaries, by accounting for the morphological updates at the bottom They found that, given the tidal input at the mouth of the tidal channel, at a century time-scale, the longitudinal profile evolves from an arbitrary initial condition to a final equilibrium configuration characterized by a shallow area in the landward portion of the channel, whose concavity increases with channel convergence, and such that the relationship between the tidal prism and cross-sectional area evolves from an arbitrary distribution to a Jarret’s type law. The results might help unravel the complex dynamics regulating the long-term evolution of tidally-dominated systems
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