The Behavior of Daily Rainfall Extremes in the Context of Climate Change

Abstract

The devastating floods from extreme rainfall in Sri Lanka during January - February 2011, caused billions of rupees in damages which included a major loss in the rice crop. Nearly a million people were rendered homeless and 62 lives were lost. Furthermore, during the last one hundred years, Sri Lanka has experienced severe floods at various times due to extreme rainfall. Given this scenario and the ever growing concerns of climate change, the objective of this paper is to investigate whether a trend exists in extreme rainfall, so that extreme events can be identified and the likely consequences reduced. Accordingly, annual maximum daily rainfall series at six meteorological stations were analyzed using over 100 years of data. Three statistical tests, Spearman's Rho, Mann - Kendall and Linear Regression which cover both parametric and non-parametric approaches have been used to identify trends. These tests indicate the absence of a significant trend at all stations. However, if very recent data (2006-2010) for Colombo are included in the analysis interestingly a significant increasing trend is shown. Such features in the trend of rainfall extremes will have implications in hydrologic design and dam safety studies. The research findings suggest that the risk of disasters associated with severe floods is very likely to increase and deserves close monitoring. A better understanding of trends in extreme rainfall, will help mitigate the impact flood disasters, enabling society to achieve greater economic prosperity and forge towards sustainable development.