The impacts of storminess were examined in detail at three sites in the Outer Hebrides, Scotland; six sites in Western Ireland; four sites in NW France; two sites in NW Spain; and three sites in Portugal: one in the Algarve and two in the Azores. The sites covered a latitudinal range from 37ºS to 58ºN, and involved primarily local barrier beach and dune environments with aspects from south to north-facing and coastal configurations ranging from fully open, high-energy environments to sheltered low-energy environments with varying tidal ranges from macro tidal to meso tidal. In all areas, relative sea level has been rising for the last 2000 sidereal years, and is rising at present at a rate of between 1 and 4 mm/yr., making this coastline increasingly susceptible to storminess.
In terms of immediate effect, storminess impact depends upon the configuration of the coastline, its aspect to the wind and wave conditions, the local nearshore bathymetry, local coastal morphology, with tidal conditions and the meteorology of the storm. This work found that a slowly moving but deep extra tropical cyclone generating onshore winds in a low-lying and open coastline creates the greatest flooding.
In the longer term, whilst aspect, configuration, nearshore bathymetry and coastal morphology are important, sediment supply from both the local coastline and the nearshore zone are important, together with the frequency, magnitude, and direction of movement of the storm systems. This work found that changes in coastal geomorphology (for example in dune and barrier systems) can occur on human timescales dependent upon the interaction of these factors.
This work also found evidence to suggest that storminess may be more effective in changing coastal geomorphology during periods of relative sea level rise.
The database has been compiled, and contains instrumental records for the last circa 300 years, and documentary records for up to 1000 years. Geological evidence for the last 2000 years is reported in the individual contractors' reports contained in this document. A common methodological approach has been used.
This work has shown that there has been an increase in the frequency and magnitude of storms in the last decade across the coastline as a whole. The work has also identified periods of greater and lesser storminess during the last circa 300 years, and has sought to relate these to variations in the North Atlantic Oscillation (NAO), finding that the relationship is a complex one, with a present episode of storminess being related to a strongly positive NAO index, but the episode during the late nineteenth century not so strongly correlated. It should of course be noted that the NAO is only a crude index of the complete Atlantic atmospheric structure.
The variability of the coastal response to storminess identified in (i) above has made the development of detailed behavioural/conceptual models difficult. However, a model of barrier evolution based upon the Algarve has been developed, appropriate to many of the barrier environments of the area examined. A numerical model of storminess impact for given rises of relative sea level for Scotland has also been developed. More widely, using estimates of sea surface temperature and sea ice extent, and using a high revolution global circulation model (GCM), changes in the wide and storm climate have been estimated. The model predicts a general upstream shift in wind and storm climate across the Atlantic towards the east, with fewer but more intense storms in northern European areas. Models support the trend in observational information, showing a seasonal shift in the principal cyclone tracks.
The CODACS database developed in this contract contains information for many areas of the Atlantic coastline which may form the basis for informed coastal zone management, and is sufficiently flexible for additional data to be added for specific areas. The studies carried out on storminess impact at a wide range of sites will provide analogies for studies of specific areas for which detailed coastal zone management is required.
Funding SchemeCSC - Cost-sharing contracts
BT7 1NN Belfast
15071 La Coruña