Climate change is expected to impact soils through changes in both soil erosion and rainfall erosivity. Change in erosion can have significant implications for natural assets, agricultural lands and water quality. The Office of Environment and Heritage has applied selected projections from NARCliM to current ACT HGL land degradation layers and modeled hillslope erosion data in order to provide updated information on the projected impacts of climate change on soil erosion and rainfall erosivity in the near future (2030). A number of steps were taken to derive erosion hazard and climate risk ratings for the ACT: (i) Divide ACT HGL into two groups – highland and lowland. (ii) Cut modeled current hillslope erosion to the highland group boundary. (iii) Assign 1 to 5 rating: (< 0.5 t/ha/yr = 1; 0.5 to 2 t/ha/yr = 2; 2 to 5 t/ha/yr = 3; 5 to 10 t/ha/yr = 4; > 10 t/ha/yr = 5). (iv) Cut water erosion LSC to lowland group boundary. (v) Assigned 1 to 5 rating: LSC 1 & 2 =1 (Very Low); LSC 3 & 4 = 2(Low); LSC 5 = 3 (Moderate); LSC 6 = 4 (High); LSC 7 & 8 = 5 (Very High). (vi) Combine highland and lowland groups to form continuous ‘current erosion hazard’ feature. (vii) Convert hazard feature to a GRID. (viii) Determine percent change in predicted rainfall erosivity (r-factor) from modeled NARCliM hillslope erosion data for three selected near future regional climate projection ensembles (multimodel mean, CCCMA3.1-R2, ECHAM5-R3) (ix) Classify results in to five classes and assign scores: (< -10% = -2; -10% to -5% = -1; -5% to 5% = 0; 5% to 10% = 1; > 10% = 2) (x) Using raster maths in ArcGIS, add current erosion hazard scores and percent change in predicted rainfall erosivity scores to derive overall climate change risk ratings for each of the selected climate projection ensembles (1-Very Low, 2-Low, 3-Moderate, 4-High, 5-Very High). (xi) Convert climate change risk grids to feature classes and dissolve on ‘rating’. (xii) Join extra fields for GIS use. (xiii) Combine new hazard and risk features into a single geodatabase.

Updates: This product is a ‘first-pass’ assessment, but can be updated as required if new or better mapping become available. It is expected changes will be made as new NARCliM and ACT soil landscape products become available.

Fit for purpose: This dataset was captured at 1:25,000 scale. This dataset is fit for use as a tool for identifying current and future erosion hazards under climate change at the paddock-scale in the ACT, but this does not negate the need for site assessment at a scale suitable to any potential land use or development under consideration. The mapping was mapped in GDA1994 MGA Zone 55s and transformed to GDA2020 MGA Zone 55s.

Credits: Rob Muller (NSW OEH), Wayne Cook (NSW OEH), Allan Nicholson (NSW DPI), Alie Cowood (UC)

Disclaimer: While all care is taken to ensure accuracy, the ACT Government does not warrant that the map is free from errors.