A Numerical Investigation on Tidally Induced Sediment Transport and Morphological Changes with Changing Sea Level in South-East England

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.

Modeling the effects of interior headland restoration on estuarine sediment transport processes in a marine-dominant estuary

“…Barring anthropogenic influence, tide and wave dynamics govern the fate and transport of sediments and the subsequent morphologic evolution of coastal systems. In estuaries, sediment transport potential varies with local bathymetry, bottom friction, and tidal asymmetries (Leonardi et al, 2019). Sea level rise (SLR) can alter tidal hydrodynamics and resultant sediment transport particularly along low-gradient coastlines like the northern Gulf of Mexico (Passeri et al, 2015).…”

“…SLR has been associated with increases in tidal prism (Xie et al, 2022). Increases in tidal prisms can lead to higher net sediment fluxes, which, in turn, alters bed level (Leonardi et al, 2019). Increases in flood currents under higher sea levels may resuspend sediment from the bed and deposit it onto the marsh platform, while increases in ebb currents and bottom shear stresses erode sediment and transport it out of the system (Zhang et al, 2019); this effect is, in some instances, more significant for sand fractions than mud fractions (Zhang et al, 2020), where mud fractions may be deposited on and retained by the marsh.…”

“…Integrating sediment transport modeling into early phases of restoration planning aids in identifying where and under what conditions restoration will most likely be successful (Ganju, 2019). Process-based numerical models such as Delft3D are used to simulate hydrodynamics, sediment transport, and resulting morphological evolution in estuarine and coastal environments (Leonardi et al, 2019;Zhang et al, 2019;Zhang et al, 2020). This allows for detailed physics-based assessments of how natural and human drivers including restoration actions and SLR may impact estuarine physical processes to help inform management decision-making.…”