This tool can be used to calculate the sediment transport index (STI) described by Moore and Burch (1986). This index is derived from unit stream-power theory and is sometimes used in place of the length-slope factor in the revised universal soil loss equation (RUSLE) for slope lengths less than 100 m and slope less than 14 degrees. The index combines upslope contributing area (As), under the assumption that contributing area is directly related to discharge, and slope (B). The index is calculated as:
STI = (m + 1) × (As / 22.13)m × sin(B / 0.0896)n
Where As is the specific catchment area (i.e. the upslope contributing area per unit contour length) estimated using one of the available flow accumulation algorithms in the Hydrology toolbox; B is the local slope gradient in degrees; the contributing area exponent, m, is usually set to 0.4 and the slope exponent, n, is usually set to 1.4. Notice that As must not be log-transformed prior to being used; As is commonly log-transformed to enhance visualization of the data. The slope image can be created from the base digital elevation model (DEM) using the Slope tool. The input images must have the same grid dimensions.
Grid cells possessing the NoData value in either of the input images are assigned NoData value in the output image. The output raster is of the float data type and continuous data scale.
The following is an example of a Python script that uses this tool:
wd = pluginHost.getWorkingDirectory()
caFile = wd + "contributing area.dep"
slopeFile = wd + "slope.dep"
outputFile = wd + "output.dep"
caExponentValue = "1.0"
slopeExponentValue = "1.3"
args = [caFile, slopeFile, outputFile, caExponentValue, slopeExponentValue]
pluginHost.runPlugin("SedimentTransportIndex", args, False)
This is a Groovy script also using this tool:
def wd = pluginHost.getWorkingDirectory()
def caFile = wd + "contributing area.dep"
def slopeFile = wd + "slope.dep"
def outputFile = wd + "output.dep"
def caExponentValue = "1.0"
def slopeExponentValue = "1.3"
String[] args = [caFile, slopeFile, outputFile, caExponentValue, slopeExponentValue]
pluginHost.runPlugin("SedimentTransportIndex", args, false)