COASTAL DYNAMICS AND IMPACT OF COASTAL PROTECTION WORKS ON THE SPURN HEAD SPIT (UK)

The erosion of the glacial tills along the Holderness Coast (eastern E ngland) has released material which has led to the formation of a 4.5 km sand and gravel spit, Spurn Head, across the mouth of the Humber es tuary. This paper examines the sedimentology and geomorphology of the spit and of the tidal flat behind it (Spurn Eight), and assesses the e ffects of coastal defences on the nearshore dynamics. A study of the c oastal dynamics was carried out by analysing wind data and modelling w ave shoaling and refraction at the estuary mouth, and on the tidal fla t. The geomorphology and sedimentology of the beaches and the tidal fl at were studied to assess the response of the spit system to different weather conditions. The results show that only 6% of the longshore dr ift produced by cliff erosion in Holderness is transported along Spurn Head, mainly by waves from the north and the north-east. This drift i s stored in an area of sand and gravel banks at the tip. Medium-size s and is carried around the tip by south-easterly waves, leading to the formation of a small area of tidal sand waves. Waves from the southwes t, which originate within the estuary, spread the sand over the tidal flat, but are not able to carry it towards the most northern inner par t of the spit. Coastal defences built along the spit have slowed its r ate of landward migration and prevented overwash processes. The defenc es have not been maintained for the last 30 years so that the spit is now likely to be breached in the winter months whenever surge conditio ns exist. (C) 1997 Elsevier Science B.V.