Hillslope Position by Soil Series

Posted: Wednesday, June 5th, 2013

Soil survey data are typically built upon a foundation of soil-landscape relationships that have been verified in the field. SSURGO data contain several geomorphic descriptions of landscape, landform, hillslope position, and surface shape for each soil component. In an ideal setting, suites of soils predictably occur along the standard hillslope positions (summit, shoulder, backslope, footslope, toeslope), forming what is known as a catena. Reality is usually much more complex, and soil component Alpha may actually have been found at several hillslope positions. With a little aggregation and re-formatting of the raw data, it is possible to use SSURGO to produce a probability matrix for a set of named components (e.g. soil series) describing where these soils are most likely to occur. A new function in the sharpshootR package makes this operation very simple.

# you will need to install these packages assoc. dependencies
# soils of interest
s <- c('auburn', 'pardee', 'amador', 'pentz')
# get hillslope position probability matrix from SDA
y <- hillslope.probability(s)
# view results (below)
  compname Toeslope Footslope Backslope Shoulder Summit
1   amador       NA      0.03      0.45       NA   0.21
2   auburn       NA      0.03      0.70     0.04   0.17
3   pardee     0.18        NA      0.27     0.09   0.36
4    pentz     0.02        NA      0.58       NA   0.39