Impact assessment of climatic and land-use changes on flood runoff in southeast Queensland

Over the past century, land-use has changed in southeast Queensland, and when coupled with climatic change, the risk of flooding has increased. This research aims to examine impacts of climate and land-use changes on flood runoff in southeast Queensland, Australia. A rainfall-runoff model, RORB, was calibrated and validated using observed flood hydrographs for one rural and one urbanized catchment, for 1961-1990. The validated model was then used to generate flood hydrographs using projected rainfall based on two climate models: the Geophysical Fluid Dynamics Laboratory Climate Model 2.1 (GFDL CM2.1) and the Conformal-Cubic Atmospheric Model (CCAM), for 2016-2045. Projected daily rainfall for the two contrasting periods was used to derive adjustment factors for a given frequency of occurrence. Two land-use change scenarios were used to evaluate likely impacts. Based on the projected rainfall, the results showed that, in both catchments, future flood magnitudes are unlikely to increase for large flood events. Extreme land-use change would significantly impact flooding in the rural catchment, but not the urbanized catchment.