An Estimation of storm surge heights of Colombo coastline

Storm surges are one of the worst coastal marine hazards in the world. Coastal flooding due to tropical cyclone - induced storm surges has caused considerable damage and loss of life in the North Indian Ocean region including in Sri Lanka. Possible sea level rise is gradual and occurs over a long time frame. However, extreme weather events can occur at any time and can have a significant impact on the coast line. This study is about the estimation of storm surge heights at Colombo coastline. Sea water levels measured off Colombo Port for 31 years were analyzed using statistical methods to establish the design storm surge heights with known return periods. Harmonic analysis based computer program was used to generate astronomical tide and storm surges were considered as the difference between sea level and astronomical tide. The extracted surge data were statistically analyzed by using the Extreme Event Analysis method. Design sea levels with different return periods are calculated and presented with the paper. The storm surge height for 100 year return period was found to be 0.391m and corresponding design sea level height was 0.906 m relative to mean sea level