The coastal zone is an area of interaction between terrestrial and marine processes. It is area with immense geomorphological and ecological interest. The coastline is dynamic in nature and undergoes frequent changes, continuously shaped by the processes of erosion and accretion. This environment is highly susceptible to change due to sea level rise secondary to global warming, physical factors such as waves, increased activity of storms and near shore currents and anthropogenic factors such as man-made structures and coastal engineering. Our review of literature on coastline changes with emphasis on shoreline erosion has highlighted the magnitude of the problem worldwide and the complexity of the processes that shape the coasts. In this part of our review, we will attempt to present up to date published work which will assist us to gain better understanding of the complex coastal processes modifying the shoreline with special emphasis on the coastline of theUnited Kingdom.
Coastal erosion secondary to sea-level rise was proposed long ago by Bruun (1962). Bruun developed a model predicting that coasts will erode 50-200 times the rate of sea-level rise. The relationship of sea-level rise to erosion has become known as the Bruun Rule. Sea –level rises allow waves to affect further up the shores and as a result transport sand offshore, leading to coastal retreat and erosion. Williams et al (1999) investigated the coastal forest retreat on the west coast of Florida, USA. His study concluded that the coastal forest replacement by salt marshes was consistent with impacts of rising sea levels. In the same context Douglas (2001) reported average sea-level rise rates of 2-3mm/year in the United States, whereas Crawford and Thomson (1999) reported predicted sea-level rise estimates of between 3 and 9 mm/year along the Canadian British Columbia shoreline for the next 80 years Crawford & Thomson (1999) Crawford, W. R., & Thomson, R. E. (1999). Sea level rise in British Columbia. In C. J. Stewart (Ed.), Proceedings of the 1999 Canadian Coastal conference (Vol. 1. pp. 265–276). Canadian Coastal Science and Engineering Association.. Snoussi et al (2009) investigated the risk of flooding in the Tangier Bay, Morocco as a result of the accelerated rise of sea-level using a GIS-based inundation analysis and an erosion modelling approach. Vulnerable socio-economic sectors such as the coastal defences, the port, the urban area, the industrial area, the railway and the tourist coastal infrastructures were assessed. Results derived from this study indicate that shoreline erosion would affect nearly 20% and 45% of the total beach areas respectively in 2050 and 2100.