This dataset and its metadata statement were supplied to the Bioregional Assessment Programme by a third party and are presented here as originally supplied.
MrVBF is a topographic index designed to identify areas of deposited material at a range of scales based on the observations that valley bottoms are low and flat relative to their surroundings and that large valley bottoms are flatter than smaller ones. Zero values indicate erosional terrain with values 1 and larger indicating progressively larger areas of deposition. There is some evidence that MrVBF values correlate with depth of deposited material.
The MrVBF product was derived from the Smoothed Digital Elevation Model (DEM-S; ANZCW0703014016), which is based on the 1 second resolution SRTM data acquired by NASA in February 2000.
The 1 second SRTM-derived Smoothed Digital Elevation Model (DEM-S; ANZCW0703014016).
MrVBF calculation
The MrVBF method is described in Gallant and Dowling (2003). It is based on slope and position in landscape (ranking within a 3- or 6-cell circular window) calculated from the original DEM and progressively generalised DEMs. The algorithm used to create this product is version 6g-a5, which is slightly different to that in the original paper.
Each value of MrVBF is associated with a particular scale and slope threshold. For each successive value the slope threshold halves and the scale triples. At each scale a location is considered erosional if it is high (ranked above the majority of the surrounding cells) or steep (slope greater than the threshold), and depositional otherwise. The largest value takes precedence at each location, so a value of zero indicates the site is considered to be erosional at all scales.
Value Threshold Resolution Interpretation
slope (%) (approx)
0 30 m Erosional
1 16 30 Small hillside deposit
2 8 30 Narrow valley floor
3 4 90
4 2 270 Valley floor
5 1 800 Extensive valley floor
6 0.5 2.4 km
7 0.25 7.2 km Depositional basin
8 0.125 22 km
9 0.0625 66 km Extensive depositional basin
MrVBF has been used with topographic wetness index (TWI) to predict soil depths; see McKenzie, Gallant and Gregory (2003) for details.
The MrVBF calculation was performed on 1° 1° tiles, with overlaps to ensure correct values at tile edges, for the finer scale steps (1 through 3). The coarser scale steps use lower resolution data so could be processed for the entire continent as a single piece, starting with a generalised version of DEM-S at 9 second resolution. The tiled processing clipped out the relevant parts of the 9 second results and combined them with the finer scale results from the 1 second DEM-S.
CSIRO (2016) AUS SRTM 1sec MRVBF mosaic v01. Bioregional Assessment Source Dataset. Viewed 18 June 2018, http://data.bioregionalassessments.gov.au/dataset/79975b4a-1204-4ab1-b02b-0c6fbbbbbcb5.