Hillslope Position by Soil Series

Submitted by dylan on Wed, 2013-06-05 18:34.

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.

Code Example

# 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

hillslope position

Are you computing hillslope position from DEM then relating smu location to location of each hillslope position? Are these functions in sharpshootR? Or are you just taking the qualitative hillslope description for each smu component in SSURGO, assigning the particular position to a component, then computing the probability? sdd

Hillslope Position

Hi Steve, it is good to hear from you. These calculations are based entirely on what is in SSURGO. Probability calculations are based on proportions, and re-formatted in R. More information on the functions from the sharpshootR package can be found here:


Note that typing the function name on the R console without parenthesis will cause the function code to be printed. Give a call sometime and I would be happy to elaborate.