Global climate change : impact on the coastal zone of Sri Lanka

Abstract

It is unequivocal that sea level is rising and it will further exacerbate the already existing problems in the coastal regions. With the increase of greenhouse gases, the global warming which is the main factor affecting the sea level rise has accelerated. Rise in sea level can cause many problems in the socio-economic activities and coastal eco systems due to coastal erosion, inundation, salt water intrusion, etc. Therefore countries having low lying coastal areas need to pay attention on this before the problems become worst. This study was conducted in order to assess the shoreline variation due to SLR in southwest coast of Sri Lanka. Four coastal locations (Ambalangoda, Bentota, Kalutara and Lunawa) were selected which have different morphological features. Nearshore wave climates at those locations were established considering SLR scenarios established by IPCC (Intergovernmental Panel on Climate Change) in 2007. Offshore wave measurements were used for the analysis. In establishing nearshore wave climate MIKE21 Nearshore Spectral Wave Model was used and the shoreline recession was estimated for different scenarios by Bruun Rule. In addition change in wind direction and speed considered only at Lunawa. The established nearshore wave climate shows a clear increase in significant wave height in both sea and swell waves at all the locations with the increase of sea level. However the changes in mean wave period and in mean wave direction at nearshore are not significant. Shoreline recession caused by sea level rise varies from place to place depending on the wave climate and the morphological features of the area. Generally shoreline recession is 50 to 120 times the sea level rise.