Past and future trends in Australian floods: what are the causes?

The possibility of changing flood hazards due to climate change is an issue of concern for engineers, governments and emergency services. However it is not yet clear how flood hazard will change and how these changes may vary across Australia. Here we approach these questions by considering the complex interactions between flood-causing variables. This is achieved by synthesizing existing research on the trends and likely changes in the causes of floods. These causes include the possible changes to meteorological variables, in particular extreme rainfalls, as well as impacts of changing catchment conditions including catchment wetness and land use modifications due to vegetation changes and/or urbanization. There has been research into trends in daily rainfall extremes around the world and for Australia but less work on sub-daily rainfall. Australian daily rainfall extremes show limited evidence of trends when the annual maximum series is considered although there is significant variability in these time series and changes in seasonality are not accounted for in this type of analysis. Sub daily rainfalls show clearer evidence of generally increasing trends. The interaction between these generally increasing trends and changes to catchment wetness which are more likely to be linked to annual rainfall and evaporation trends is a question of particular interest.