An analysis of the potential erosional changes in the KwaZulu-Natal coastline due to the effects of sea level rise and associated storm surges.

Abstract

The coastlines around the world are currently in the process of being eroded by naturally occurring oceanic conditions. The vast majority of people living near or on these coastlines have no idea what they may be in store for them, with a notable exception being the coastline of the Netherlands. The aim of this research is to understand which areas on the KwaZulu-Natal coastline may be affected by the occurrence of sea level rise including the effects of future storm surges at various time intervals. The coastline is eroded continuously due to the cyclic movement of tides, waves and winds, however the most significant erosion events are likely to occur due to the combination of sea level rise and storm surges, as these both extend further inland and reach higher altitudes than the day-to-day processes of coastal erosion. The storm surge that occurred on the East Coast of South Africa in March 2007 was therefore used as a reference for storm surge as a means of comparing and modelling future storm surge events. While there is some controversy, literature suggests that the mean annual sea level rise occurs at a rate of some 15.5mm per year, although some researchers argue in favour of a rate of almost twice that. The year 2100 was used as the target date to replicate the worst case scenario storm event, but without accounting for a potential increase in the storm intensity driven by global warming.. Coastal protection infrastructures have been installed in some areas, but have been found not to work effectively, occasionally even exacerbating the effects of erosion. Results suggested that by 2100, the sea level rise alone would not have had much of an effect as it is projected to rise by an average of 2m. When this is, however, coupled with a storm surge threshold of 3.5m, most of the study sites along the KZN coastline would experience significant flooding and associated destruction. The research is of a hypothetical origin and the predictions may or may not occur. If the hypothesis would have to be correct, then the planning for prevention methods may be too late. Thus this research must be considered as new information to assist with coastal management. If the projection into the future is taken to include replication of an event with the intensity equivalent to that of the March 2007 event, flooding may reach as high as 10m with catastrophic social and economic consequences. Only time and judicious forward planning with a re-think of the Coastal Zone Management Act will alleviate problems in the future.