Predicting Changes of Rainfall Erosivity and Hillslope Erosion across New South Wales, Australia

Abstract

New South Wales and Australia Capital Territory Regional Climate Modelling (NARCliM) project has produced a suite of 12 regional climate projections for south-east Australia spanning the range of likely future changes in climate. The aim of this study was to model and predict the impacts of climate change on rainfall erosivity and hillslope erosion risk across New South Wales using the NARCliM projections to assist the long-term climate change adaptation and regional planning. We developed a daily rainfall erosivity model for Southeast Australia to calculate monthly and annual rainfall erosivity values from the projected daily rainfall data for the baseline (1990-2009) and future periods (2020-2039 and 2060-2079). We produced monthly and annual hillslope erosion maps for these three periods using the Revised Universal Soil Loss Equation (RUSLE) with spatial interpolation to finer scale (100 m). Automated scripts have been developed in a geographic information system (GIS) to calculate the time-series rainfall erosivity and hillslope erosion so that the processes of large quantity climate projections are realistic, repeatable and portable. The model performance was assessed by comparing with data from Bureau of Meteorology for the baseline period and the overall coefficient of efficiency reached 0.9753 (RMSE 13.2%). 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. The change is highly uneven in space and time, with the highest increase occurring in the Far-west in autumn. The rainfall erosivity is generally higher in summer and lower in winter, with about 10 times difference between February (highest) and July (lowest).