Coastal erosion is a complex process that has a variety of
causes, with rising sea level being only one of them. Most
importantly, whereas climate change and relative sea-level rise are
global and regional phenomena, respectively, coastal erosion is a
local process. 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). Where the coast
is protected by engineering structures, coasts are generally
experiencing a steepening of the intertidal profile. Both coastal
erosion and steepening 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. Management of coastal
erosion in the UK is the joint responsibility of Defra and coastal
councils, and Shoreline Management Plans (SMPs) are an important
non-statutory instrument to assist with coastal management at a
local and regional level.
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. Coastal erosion can also have a beneficial
effect: the introduction of eroded sediment into the nearshore
sediment system and the subsequent deposition can reduce the risk
of coastal flooding. 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, 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. Any predictions of general coastal response due
to climate change are therefore relatively meaningless and will
have a low confidence. However, if a detailed study is conducted
and long-term coastal change data are available, then
local or regional predictions of coastal response
to climate change can have medium confidence.
