The recent sedimentology of Scolt Head Island, Norfolk

• Main Author: Roy, Peter Stanton
• Published: Imperial College London 1967
• Subjects: 551
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.623002

Recent sediments forming Scolt Head Island have been divided into beach, dune and tidal inlet environments on physiographic and sedimentological criterion. A technique of particle, analysis, based on the Emery Settling Tube, has been developed to investigate grain-size characteristics. It was found impossible to distinguish the different environments by this property alone. A theory of fractionation has been proposed to interpret the general grain-size trends shown by these sediments. An attempt has been made to relate the sediments to the existing dynamic (wave and current) conditions controlling their deposition. The theoretical wave activity on the Scolt Head Island beach has been calculated from meteorological data. A residual westward longshore component of wave action has been determined. The tidal range has been shown to cause an increase in wave action on the beach as the tide rises. This causes an increase in both the grain-size of the beach material, and of the beach slope, from the low to the high water level. Current action along the front of Scolt Head Island is believed to produce an eastward residual sediment transport in the near-shore zone. This is balanced by the residual westward longshore drift of the fine grained sand on the lower part of the beach. Direct current measurements have been related to the sediment carried in suspension in Brancaster Harbour which separates Scolt Head Island from the mainland. The grain-size distribution of certain sand deposits in the inlet have been related to the local current pattern. A comparison between a series of Ordnance Survey maps indicates that Scolt Head Island has, during historical time, migrated shorewards and grown by accretion at its western end. Its shorewards migration results from coastal erosion caused by the post glacial rise in sea level; while the accretion at its western end reflects the dominant westward littoral drift, as well as (indirectly) the erosion of the Burnham Bank Complex lying to the north of the north Norfolk coast. The evolution of this bank complex has been studied by comparing a series of Admiralty charts. Changes in its topography have been related to the tidal current pattern. This indicates that a. closed circulation, based upon the directions of the strongest currents (and, therefore, of residual sediment movement), causes sediment to be deposited. Erosion occurs where a closed circulation is absent.