Author(s): San Chuin Liew; Shie-Yui Liong; Srivatsan V. Raghavan
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Keywords: IDF curves; Rainfall data sparse region; Regional Climate Model; Dynamical Downscaling; Flooding
Abstract: In recent decades severe flooding events have been witnessed more frequently both in urban and less urban cities causing significant economic and human losses. With climate change, one of the anticipated impacts is an increase in the intensity and frequency of extreme rainfall which will cause even much more casualties. Optimal mitigation measures can be taken only when projected rainfall is derived from high resolution regional climate models (RCM). From RCM extremes can be analyzed and thus Intensity-Duration-Frequency (IDF) curves for 2071-2100, for example, can be derived which are extremely essential in drainage design. There are many urban cities which have short or no rainfall records; deriving present climate’s IDF curves is an issue yet to be solved first before future climate’s IDF curves can be meaningfully presented. A novel approach is presented in this paper and demonstrated and validated on a site in Java, Indonesia. Study showed that IDF curves generated by RCM, driven by Re-Analysis data (ERA40), underestimated the existing IDF curves ranging from 21–45%at places in Singapore, Kuala Lumpur and Jakarta. This range was used to derive the upper and lower bounds of IDF curves at another site, Darmaga (in Java, Indonesia) and compared reasonably well with the existing IDF curves of Darmaga station. The paper also shows how the proposed approach presents future IDF curves, for 2071-2100 period, resulting from RCM driven by Global Climate Model ECHAM5 of A2 scenario. The proposed approach can be extended to other emission scenarios so that a bandwidth of uncertainties can be assessed for optimal mitigation measures.
Year: 2012