Eigenfunction analysis of decadal fluctuations in sandbank morphology at Gt Yarmouth

Empirical orthogonal function (EOF) analysis (or Principal component analys is) has become an established technique for investigating interannual beach level fluctuations. In this paper, EOF techniques are applied to a series of historical bathymetric surveys of a nearshore sandbank system in order t o investigate their long term morphological behaviour. The sandbanks cover an area approximately 30km alongshore and 10km cross-shore and lie similar to2 kilometres offshore from Gt. Yarmouth which is situated on the East Coa st of the UK. Geographical Information Systems (GIS) techniques were used t o create digital models of the seabed from historic survey data. The models were analysed using EOF and GIS methods to identify any trends or cyclic b ehaviour in the morphology of the sandbanks. Evidence of changes in gross s andbank configuration, long term trends and potentially recurrent behaviour have been identified, and their significance for current coastal managemen t practice are discussed.