Multi-resolution Valley Bottom Flatness (MrVBF)

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.\n\nThis collection includes 1 arc-second and 3 arc-second resolution versions of MrVBF.\n\nThe 3 arc-second resolution product was generated from the 1 arc-second MrVBF product and masked by the 3” water and ocean mask datasets.\n\nLineage: Source data\n1.\t1 arc-second SRTM-derived Smoothed Digital Elevation Model (DEM-S; ANZCW0703014016).\n2.\tThe 1 arc-second MrVBF product\n3.\t3 arc-second resolution SRTM water body and ocean mask datasets\n\nMrVBF calculation\nThe 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.\n\nEach 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.\n\nValue Threshold Resolution Interpretation\n slope (%) (approx)\n 0 30 m Erosional\n 1 16 30 Small hillside deposit\n 2 8 30 Narrow valley floor\n 3 4 90\n 4 2 270 Valley floor\n 5 1 800 Extensive valley floor\n 6 0.5 2.4 km\n 7 0.25 7.2 km Depositional basin\n 8 0.125 22 km\n 9 0.0625 66 km Extensive depositional basin\n\nThe 3 arc-second version of MrVBF was derived from the 1 arc-second MrVBF using the median value in each 3 x 3 group of 1 arc-second grid cells.\n\nMrVBF has been used with topographic wetness index (TWI) to predict soil depths; see McKenzie, Gallant and Gregory (2003) for details.\n\nGallant, J.C. and Dowling T.I. (2003) A multiresolution index of valley bottom flatness for mapping depositional areas. Water Resources Research 39(12) 1347-1360. \n\nMcKenzie, N.J., Gallant, J.C. and Gregory, L. (2003) Estimating water storage capacities in soil at catchment scales. Cooperative Research Centre for Catchment Hydrology Technical Report 03/3.