Coastal dynamics and impact of coastal protection works on the Spurn Head spit (UK)

Abstract

The erosion of the glacial tills along the Holderness Coast (eastern England) 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 estuary. This paper examines the sedimentology and geomorphology of the spit and of the tidal flat behind it (Spurn Bight), and assesses the effects of coastal defences on the nearshore dynamics. A study of the coastal dynamics was carried out by analysing wind data and modelling wave shoaling and refraction at the estuary mouth, and on the tidal flat. The geomorphology and sedimentology of the beaches and the tidal flat were studied to assess the response of the spit system to different weather conditions. The results show that only 6% of the longshore drift produced by cliff erosion in Holderness is transported along Spurn Head, mainly by waves from the north and the north-east. This drift is stored in an area of sand and gravel banks at the tip. Medium-size sand is carried around the tip by south-easterly waves, leading to the formation of a small area of tidal sand waves. Waves from the southwest, which originate within the estuary, spread the sand over the tidal flat, but are not able to carry it towards the most northern inner part of the spit. Coastal defences built along the spit have slowed its rate of landward migration and prevented overwash processes. The defences 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 conditions exist.