Future changes in extreme precipitation, rainfall erosivity and hillslope erosion in southeast Australia.

NARCliM (NSW/ACT Regional Climate Modelling project) is a regional climate modeling project for the Australian area. It provides a comprehensive dynamically downscaled climate dataset for the CORDEX-AustralAsia region at 50km, and South-East Australia at a resolution of 10km. NARCliM data is being used by the NSW and ACT governments to design their climate change adaptation plans. Data is available through the AdaptNSW website (http://climatechange.environment.nsw.gov.au/). NARCliM uses WRFv3.3 regional climate model (RCM) to perform an ensemble of simulations for the present and the projected future climate. WRF is run in three different model configurations (different combinations of physical parametrizations) that have been shown to perform well in the South-East Australia and were chosen based on performance and independence. These three RCMs are simulating three different periods: 1990-2009, 2020-2040 and 2060-2080. Four different GCMs (MIROC-medres 3.2, ECHAM5, CGCM 3.1 and CSIRO mk3.0) from CMIP3 are used as initial and boundary conditions for the WRF simulations. These GCMs were chosen through a process that considered model performance, independence and projected future changes. Thus an ENSEMBLE of 12 simulations for each period is obtained. Future changes in extreme precipitation vary spatially and seasonally. Consequently, soil erosion rates may be expected to change in response to changes in the erosive power of rainfall or rainfall erosivity. This study examines the impacts of climate (rainfall) change on rainfall erosivity and hillslope erosion risk in southeast Australia based on the NARCliM ensemble projections. A daily rainfall erosivity model has been specifically developed and applied to calculate monthly and annual rainfall erosivity values from the NARCliM projected daily rainfall data for the baseline and future periods. Monthly and annual hillslope erosion risks for the same periods were estimated using the Revised Universal Soil Loss Equation (RUSLE). Both rainfall erosivity and hillslope erosion risk are predicted to increase about 7% in the near future, and about 19% increase in the far future compared with the baseline period, though this change is very uneven in space.