This tool can be used to calculate the relative stream power index. This index is directly related to the stream power if the assumption can be made that discharge is directly proportional to upslope contributing area (As). The index is calculated as:
RSP = Asp × tan(B)
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; and, p is a user-defined exponent term that controls the location-specific relation between contributing area and discharge. 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"
args = [caFile, slopeFile, outputFile, caExponentValue]
pluginHost.runPlugin("RelativeStreamPowerIndex", 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"
String[] args = [caFile, slopeFile, outputFile, caExponentValue]
pluginHost.runPlugin("RelativeStreamPowerIndex", args, false)