Estimation of future intensity duration curve by considering the impact of climate change: case study for Kuching city

Floods are occurring more frequent nowadays. The parameter used to analyse the severity of flood event is annual return interval (ARI). Hydrologists very often analyse the ARI of flood, which is 100 years, meaning the flood will occur only once in 100 years. Few months later, when flood hit the same place and the analysis showed that the severity of flood is 100-year ARI again. Theoretically, this is very confusing. One of the acceptable explanations might be the rainfall intensity has changed over the years due to the impact of climate change. Even engineers designed the drainage system strictly according to design guidelines, floods continue to occur as the rainfall intensity is increasing from year to year. Therefore, there is an initiative in this study to derive a new rainfall intensity duration curve (IDF) by including the forecasted future rainfall using “delta” approach. The selected study rainfall station is Kuching Airport. Results revealed that the newly projected IDF curves at various durations and ARIs are slightly higher than historical IDF curve. However, the results obtained are not consistent enough as data used for simulation are monthly mean and maximum rainfall data. For achieving more accurate results, it was recommended to use daily data for IDF curve projection in nearest future and disaggregate into hourly rainfall intensities using K-nearest neighbour method