Possible erosion of Ynyslas beach-face due to
extreme storms
Time estimated: 6 to 12 months
Participant: Nguyen Quang Chien, Dept. Physics and another team member
In Programme: Joy-Welch Charitable Fund
Various stretches of the Welsh coastal dunes have been exposed to
vulnerability[1],
yet estimation of risks are mostly qualitative with more emphasis on
description[2]
rather than prediction. Dynamic modelling of how such dune faces would reshape
during extreme events such as storms accompanied by high tides would aid in
risk evaluation. Dune geomorphology is a crucial physical boundary for the
growth of plants within the dune ecosystem. As a proof of concept, the erosion
of the Ynylas dune (Ceredigion, GB) would be simulated for local extreme events
such as the January 2014 storm.
A cascading analysis will be used. Firstly, oceanographic conditions
associated with the storm event should be determined. This task is done through
hydrodynamic modelling with commonly used open-source software such as Delft3D, Swan and XBeach.
This condition should ideally be compared to field measurement data, but we
referred to relevant published works due to the lack of equipment and personnel[3].
Secondly, the output of such simulation model is analysed to highlight
major driving forces to the change of this beach: waves, storm surge and wind.
In addition, the background evolution of beach morphology due to the tidal
process is considered[4].
Next, the detailed flow field and erosion hot spots on a specific
coastal transect will be identified. The simulation of turbulence and
potentially sediment stirring processes can be performed with the aid of the
Flow3D software. Computation in a multi-core system will be conducted if
possible with support from Supercomputing Wales at Aberystwyth.
The research work will provide the following outputs:
·
Time-varying fields of tide, wave and wind over the Ynyslas coastal
region during the storm events;
·
Series of map representing the change of dune and beach face over time;
·
Turbulent flow field, shear stresses and potential sand grain movement
in selected coastal transects (‘erosion hot-spots’);
·
Collection of input and parameters for hydrodynamics solvers; offering
reproducible research and readily applied to other cases.
These findings will be released to the public in 2022, including an open
access paper and an online software repository.
[1] Williams and Davies (2001). Coastal dunes of Wales; vulnerability and protection. Journal of Coastal Conservation 7: 145-154
[2] Caldwell and Yule (1981). Beach morphology changes at Ynyslas spit, Dyfed, Wales. Cambria 8: 51-69
[3] Thompson, Karunarathna and Reeve (2017). Modelling extreme wave overtopping at Aberystwyth promenade. Water 9: 663
[4] Robins and Davies (2010). Morphological controls in sandy estuaries: the influence of tidal flats and bathymetry on sediment transport. Ocean Dynamics 60: 503-517