Urban flood hazard analysis in present and future climate after statistical downscaling: a case study in Ha Tinh city, Vietnam.

Vietnamese cities are highly vulnerable to urban flooding as a consequence of climate change and rapid urbanisation. In this study, current and future pluvial urban flood hazard was assessed for Ha Tinh city. Climate scenarios were obtained after statistical downscaling by applying a quantile-perturbation approach on ensembles of 170 global and 20 regional climate models. Flood impact analysis was based on the 1D-2D dual drainage modelling approach. Extreme daily rainfall intensities are projected to increase by 5 to 20%, whereas wet day frequency will decrease with some uncertainty. Larger changes in rainfall intensities were obtained for the finer scale climate models. Under the 95% upper limit scenario for future rainfall intensities (2071–2100), a 20-year intensity in the current climate would become a 2-year storm in the future and the flood extent is projected to increase by 30–40%. This indicates a need for climate adaptation measures and sustainable future urban planning. [ABSTRACT FROM AUTHOR]