Estimation of Design Rainfall Based on Climate Change Scenario in Jeju Island

As occurrence of gradually increasing extreme temperature events in Jeju Island, a hybrid downscaling technique that simultaneously applies by dynamical method and statistical method has implemented on design rainfall in order to reduce flood damages from severe storms and typhoons.

The region has high density of rain gage stations consist of 24 rain gage stations, but more than 30 long-term data are using for trend analysis. Accordingly, Jeju and Seogwipo rain gage stations has selected to comparatively analyze and design for daily rainfall data actually measured at rain gage stations for over 30 years and rainfall data predicted for A1B scenario (Source: Climate Change Information Center). Future rainfall design has computed for each rain gage station based on the analysis result.

As a result of computation, Case 1 shows a strong tendency to excessively compute rainfall, which is continuously increasing. While Case 2 showed similar trend as Case 1, low design rainfall has computed by rainfall in A1B scenario. Based on the design rainfall computation method mainly used in Preventive Disaster System through Pre-disaster Effect Examination System and Basic Plan for River of Jeju Island which are considering climatic change for selecting 50-year and 100-year frequencies. Case 3 selecting for Jeju rain gage station and Case 1 for Seogwipo rain gage station. The results were different for each rain gage station because of difference in rainfall characteristics according to recent climatic change, and the risk of currently known design rainfall can be increased in near future.