A novel approach, using regional climate model, to derive present and future Intensity-Duration-Frequency curves

Abstract

Optimal designs of stormwater systems rely much on the rainfall Intensity-Duration-Frequency (IDF) curves. As climate has shown significant changes in rainfall characteristics, the adequacy of the existing IDF curves is called for particularly when the rainfall is much more intense. For ungauged sites, developing IDF curves for the future climate is even challenging. The current practice is, e.g., to `borrow? or `interpolate? data from regions of climatologically similar characteristics. This thesis presents a novel approach in which data are extracted from a high spatial resolution Regional Climate Model (RCM; 30 ? 30 km) driven by Reanalysis data. Indonesia is selected to demonstrate the application of this approach. Extremes from projected rainfall are first used to derive IDF curves for 3 sites (meteorological stations) where IDF curves exist; biases observed resulting from these sites are used to derive present day IDF curves for ungauged sites. The final product of the present day derived IDF curves fall within +38% to +45%. This thesis also shows how the proposed approach presents future IDF curves, resulting from RCM driven by Global Climate Models of different emission scenarios. The proposed approach can be extended to other emission scenarios so that a bandwidth of uncertainties can be assessed for optimal mitigation measures.