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Coastal erosion and coastal geomorphology

Plymouth University

WHAT IS ALREADY HAPPENING WHAT COULD HAPPEN
  • Coastal erosion is occurring along 17% of the UK coastline (30% of England's coastline; 23% Wales; 20% Northern Ireland; 12% Scotland).
  • Almost two-thirds of the intertidal profiles in England and Wales have steepened over the past 100 years.
  • Steepening of the intertidal profile is particularly prevalent on coasts protected by hard engineering structures (this represents 46% of England's coastline; 28% Wales; 20% Northern Ireland and 7% Scotland).
  • Both coastal erosion and steepening of intertidal profiles are expected to increase in the future, due to the effects of sea-level rise and changes to wave conditions.

A large proportion of the UK coast is currently suffering from erosion (17% in the UK; 30% in England; 23% in Wales; 20% in Northern Ireland; 12% in Scotland).  Almost two-thirds of the intertidal profiles in England and Wales have steepened over the past hundred years, a process which is particularly prevalent on coasts protected by hard engineering structures (this represents 46% of England's coastline; 28% of Wales; 20% of Northern Ireland and 7% Scotland). Both coastal erosion and steepening of intertidal profiles effects are expected to increase in the future due to the effects of climate change, especially sea-level rise and changes to the wave conditions.

The natural response of coastal systems to sea-level rise is to migrate landward according to the roll-over model, through erosion of the lower part of the nearshore profile and deposition on the upper part. This process is accompanied by the onshore transport of sediment. The roll-over model is applicable to estuaries, barriers and tidal flats, and the rate of coastal recession is likely to increase with the rate of sea-level rise. Rocky coasts (hard and soft) are erosional coasts and retreat even under stable sea-level conditions. Their retreat rates are expected to increase as a result of sea-level rise and increased storminess, but along soft-rock coasts, the introduction of cliff material into the nearshore zone may slow down local erosion rates through the formation of beaches. Human activities, such as land reclamation, the building of hard coastal defences and the construction of jetties and marinas significantly impair the ability of coastal systems to respond naturally to changes in the forcing by restricting the free movement of coastal sediments.

It is very important to consider, however, that the coastal response to sea-level rise is very much determined by site-specific factors. These include relative sea-level history, Isostasy is the Equilibrium in the earth's crust such that the forces tending to elevate landmasses balance the forces tending to depress landmasses.isostatic land-level change, solid and drift geology, wave/tide conditions, longshore sediment transport, human impacts and the interactions between different coastal systems. More often than not, it is these site-specific factors that determine the coastal response, rather than a global change in sea level or a regional change in wave climate. Therefore any predictions of coastal response due to climate change will have a low confidence, unless a detailed study is conducted and long-term coastal change data are available.

What is already happening - High

High confidence for the present statement is derived from the detailed and comprehensive studies that have been carried out to assess current coastal erosion rates (EUROSION, Futurecoast and ForeSight projects).

What could happen in the future - Low

Low confidence for the future stems firstly from uncertainties about the effect of climate change on the rate of sea-level rise and, especially, the wave climate (storminess and wave direction), and secondly from the highly interconnected nature of coastal systems and the complex and not very well understood coastal response to changing sea-level and wave conditions.

Apart from uncertainties about the effect of climate change on sea-level and wave climate, the coastal response to these changing boundary conditions is complex due to the connectivity between coastal sub-environments (cliff, beach, dune, estuary). The Futurecoast approach of considering the coast as a series of Coastal Behavioural Systems (CBS) is a significant improvement to previous approaches, because it acknowledges these connections, and also the need to consider coastal evolution over long time scales. However, at present our understanding of how these CBSs function is largely conceptual and this needs to be much more quantitative.

Increased coastal erosion due to climate change will provide significant opportunities for environmental engineers (mainly coastal engineers) to develop additional, or redesign existing, coastal protection measures, whether in the form of hard engineering structures, or soft engineering practices (beach recharge and managed realignment). Increased implementation of beach recharge schemes will have a considerable commercial effect on the aggregate industry. Depending on how society responds to increased coastal erosion, there can also be a very significant effect on the tourist industry through the loss of beach frontage and recreational beach area.

Gerhard Masselink
School of Geography, Room 104, 12 Kirkby Place, Drake Circus, University of Plymouth, Plymouth, Devon, PL4 8AA

Paul Russell
School of Earth, Ocean & Environmental Sciences, A528, Portland Square, Drake Circus, University of Plymouth, Devon, PL4 8AA