With the variation of parameters aligned to a spatial layer representing the Grazing Land Management Land Types that has been intersected with a representation of the degree to which grazing activities are considered ‘open’ or ‘closed/forested’ (GLM). The features of this intersected data set have been simplified to assist in storage and analysis.
To apply the RUSLE to each of the GLM polygons within a defined project area of interest, P2R Projector submits the footprint of each intersection (with relevant C Factor change parameters a and b) to a computation engine known as PEPER. PEPER is part of the VegMachine suite of analysis tools, however, is only accessible through P2R Projector. PEPER is called from P2R Projector via a specific API, which triggers an analysis of 11 Spring (late dry season, 2012-2022) representations of seasonal ground cover combined with Rainfall Erosivity (R Factor), Soil Erodibility (K Factor) and Slope Steepness (S Factor) from the Queensland Spatial Catalogue (RKS layer combined from individual factor layers).
Note: Prior to the 2023 version upgrade, PEPER-based P2R Projector estimates of erosion rates used a Statewide RKLS (see the inclusion of Slope Length (L) Factor) representation and 11 Spring ground cover layers spanning 2004-2014. The 2023 PEPER data upgrade will, in most cases, provide lower erosion estimates. However, changing the time span of consideration for PEPER calculations does mean that localised erosion estimate increases might be observed.
The PEPER computation returns an estimated average BASELINE total soil erosion rate (tons per hectare per year, BASERATE) for each feature submitted, and an estimated average ADJUSTED total soil erosion rate for a cover adjusted scenario (tons per hectare per year, ADJUSTRATE).
BASERATE is the average of all RKS * C Factor cell values within the feature’s footprint (that is, the average of 11 representations of RKS * C Factor for the feature). C Factor is converted from cover (%) using an efficient transformation that combines 2 conversions:
- Convert satellite (objective) cover to visual cover according to Trevithick and Scarth (2013)
- Convert visual cover to C Factor according to Rosewell (1997) (found conveniently in Searle and Ellis 2009)