Hillslope water erosion hazard was digitally mapped as part of the DPIPWE Water for Profit Program to enhance identification of Enterprise Suitability by effectively incorporating a sustainability measure of vulnerable soils. The mapping shows areas where a water erosion hazard might exist if sufficient groundcover is not maintained, which could lead to soil resource degradation through soil, organic matter and nutrient loss, resulting in sedimentation and contamination of drainage lines and waterways after significant rainfall and runoff events. Assigned classes are; Very Low, Low, Moderate, High, Very High and Extreme as classified ratings of a soil erosion. The index was generated as an erodibility factor (K) as part of the Revised Universal Soil Loss Equation (RUSLE), combining Digital Soil Mapping (DSM) inputs of the soil properties Coarse Fragments, Sand %, Silt %, Clay %, Organic Carbon %, Soil Permeability, and Soil Structure, with Slope and Slope-Length (from the SRTM Digital Elevation Model). The mapping covers the entire state of Tasmania at 30m resolution.

Each Raster cell is attributed by multiple soil models to arrive at an erodibility rating. The accuracy is therefore limited by the precision of the input models. The result of the validation diagnostics can be made available for each surface on request. The input soil models validated to at least a reasonable level with the standard error within acceptable ranges. Preliminary field validation was carried out to ensure integrity had been maintained and from this, attribute accuracy of the suitability categories was estimated to be no worse than 70%. During the Water for Profit project in 2015-2017 an additional 400 soil sites were sampled and combined with approximately 6,500 DPIPWE soil database sites. Logical Consistency: All raster cell data are labelled with an approximate erodibility rating. There are no duplicates. Completeness: The spatial layers cover the entire state of Tasmania, excluding Macquarie Island. Additional: Component layers of Digital Soil Mapping components are available upon request. Digital Soil Assessment is being used to model land suitability in recently commissioned irrigation schemes in the State of Tasmania, Australia, in support of Government agricultural expansion policy. The model requires comprehensive soil, climate and terrain parameters to rate the suitability of land for each chosen enterprise. The Wealth from Water pilot program commenced in a 20,000 ha irrigation district in the Meander Valley Region. This was later extended to cover a further 25,000 ha in the Meander area, 27,000 ha through the Midlands around Tunbridge, Woodbury, York Plains, Nala and Andover and an additional 10,000ha on Flinders Island. The project has now evolved to the state wide extent as part of the Water for Profit program, an element of the Tasmanian government AgriVision 2050 plan for agriculture with an additional concentration of soil and climate sampling occurring for the Midlands area of Tasmania (approximately 40,000 ha of additional detailed analysis). Digital soil mapping techniques were used to produce soil information at 30m resolution. Soil attribute spatial layers were produced from interpolation of the soil core data using the regression trees data mining algorithm in concert with predictive covariate data such as the SRTM DEM and derivatives, Gamma Radiometrics, legacy soil map, surface geology, and Satellite imagery. Layers produced included soil depth, pH, electrical conductivity, clay and stone content, drainage, and depth to sodic and/or impeding layer. Uncertainty assessment of the surfaces involved running a K-fold cross validation procedure, the result of which can be requested from the custodian. In general, however, the assessment resulted in acceptable prediction accuracies for each surface with the Root Mean Square Error (RMSE), R2 and concordance coefficient within acceptable ranges. The diagnostics information and RUSLE calculations can be made available upon request. The combination of soil and slope data was used to generate the erosion hazard rating, and appropriate management of hillslope water erosion can be found in the DPIPWE management guidelines, here: Vulnerable Soils - https://nrmdatalibrary.dpipwe.tas.gov.au/FactSheets/WfW/ListMapUserNotes/Vulnerable_soils.pdf Further reading: Kidd, D., Malone, B., Mcbratney, A., Minasny, B., Odgers, N., Webb, M., Searle, R., 2014a. A New Digital Soil Resource for Tasmania, Australia, 20th WORLD CONGRESS OF SOIL SCIENCE, pp. 612-613; Kidd, D., Webb, M., Malone, B., Minasny, B., McBratney, A., 2015a. 80-metre Resolution 3D Soil Attribute Maps for Tasmania, Australia. Soil Research; Dataset Classification Definitions- 15.5: Very Low 16: Low 16.5: Moderate 17: High 17.5: Very High 20: Extreme