IntroductionWater is a basic human need and as a country, which its economy is considerably depend on the rainfall and availability of the water resources, studies conducted in Rainfall pattern analysis is really important for Sri Lanka. Rainfall in Sri Lanka is governed by the seasonal varying monsoon system in Indian Ocean. There are two inter monsoon seasons (first and second inter monsoon) and two principal rainfall seasons (south-west and north-east monsoon). (Burt & Weerasinghe, Rainfall Distributions in Sri Lanka in Time and Space:An Analysis Based on Daily Rainfall Data, 2014)Over the past few decades due to deforestation, population growth, environmental pollution, rise of greenhouse gases and many other factors, balance in the environment was affected in a bad manner. Therefore regular rainfall pattern in Sri Lanka over the past is also seems to be affected.Rainfall is a key element in several fields such as agriculture, hydropower, irrigation etc. So it is very important to identify the patterns (time, space trends in rainfall). But even with the modern sophisticated technologies it is very difficult to forecast the rainfall accurately.Problem StatementEven though the rainfall is important in many industries and in the economy of the country, it has some adverse and destructive effects such as floods due to excessive rainfall. Over the past year Sri Lanka was heavily affected by number of severe floods and last year even a portion of Southern Expressway (which was designed for a 100 year return period) was flooded. So it is believed that the annual precipitation is increased. But these heavy rainfalls was normally followed by severe droughts which last for months. (Jayawardene & Sonnadara, 2005) So this situation is not a healthy scenario for the economy of the country. Therefore a study in rainfall pattern analysis is far more important.2CE4902A01_140012CSignificance of the ResearchThe aim of this research is to identify the impacts on time trends in Colombo rainfall pattern on design rain events. As the capital of Sri Lanka, Colombo has a far more importance than other cities since it is the economical center of the country. There are three main major characteristics in rainfall such as intensity, frequency and amount. A reasonable knowledge in those parameters will come in handy when designing, planning and managing rainfall related activities as well as flood mitigation.Scope of the StudyThis research mainly focused on the analysis of rainfall patterns in Colombo by analyzing the data collected from Department of Meteorology Sri Lanka and analyzing them using non-parametric Mann-Kendal trend test, linear regression method analysis and Sen’s slope estimator method. (Karunathilaka, Dabare, & Nandalal, 2017)Aims and Objectives of the ResearchThe main objective of this research is to identify the time trends (if there is any) in Colombo rainfall pattern and to predict future rainfall patterns using appropriate mathematical methods.Proposed Methodology? Refer adequate related literature on rainfall pattern analysis? Obtain relevant rainfall data from Department of Meteorology? Data presentation in suitable graphs? Selection of suitable methods to analyze the data? Data analysis? Identify the trends in rainfall (if there is any)? Predictions for the future rainfall trends based on the research.