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Title: Morphological evolution of nearshore sand banks : the Great Yarmouth banks, UK
Author: Thurston, Karen
ISNI:       0000 0004 2718 0988
Awarding Body: University of East Anglia
Current Institution: University of East Anglia
Date of Award: 2011
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The Great Yarmouth sand banks are a group of nearshore banks in the southern North Sea, off the Norfolk coast in the UK. The banks are highly dynamic and the processes driving their behaviour are not well understood. Bank movements control access to two ports in the region, and the banks are home to a large wind farm. Better understanding of the factors driving bank evolution is a vital first step towards predicting future bank behaviour. Numerical modelling, combining the TELEMAC system for hydrodynamics with an external morphological model, was directed towards understanding the importance of a range of hydrodynamic conditions in the morphological evolution of the banks. Long-term changes are considered through the investigation of two very different system configurations, several decades apart. Medium-term evolution is explored through the modelling of the banks at six-yearly intervals. The model performs well, reproducing key features of bank behaviour. Examination of historical bathymetries shows that the Great Yarmouth bank system takes on two configurations, 'open' and 'closed', which are stable for several decades, interrupted by periods of transition. The model demonstrates that the wide-scale system configurations are self-sustaining, through hydro- and morphodynamic feedback mechanisms, and provides evidence that the transition between system configurations may be linked to high-energy events. The banks build up in fair weather conditions, and storms serve to maintain rather than reduce the banks. Wave direction has a stronger influence than the presence or absence of surges on the magnitude of bed change experienced during a storm. Model outputs and observations demonstrate that the offshore banks in the group (Cross Sands) play an important role in the northward transport of sediment out of the bank system. Transport is likely to occur by two methods: as a flow of sediment from bank to bank, and through the migration of Cross Sands.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available