This tool can be used to map gully depth from a digital elevation model (DEM). The user must specify the name of the DEM file and the output gully depth map file, the maximum gully width (in the xy-units), the minimum and maximum gully depths (in the z-units), a threshold in difference from mean elevation (DFME), a plan curvature threshold, and a smoothing parameter. Gullies within the DEM are differentiated from larger valleys or ravines because they have widths and maximum cross-sectional depths that are less than the specified parameters. The DFME threshold is used to determine low-lying areas, in which gullies are included. A gully cross-section must also cross at least one grid cell with a plan curvature value larger than the specified threshold. Areas of high plan curvature tend to follow the bottoms of fluvial erosional features like gullies. The smoothing parameter is used to smooth the input DEM prior to estimating the plan curvature grid.
The user must also specify whether the background value (non-gully grid cells) should be NoData or zero. The tool will create two to three temporary files that will be deleted upon completion.
The following is an example of a Python script that uses this tool:
wd = pluginHost.getWorkingDirectory()
demFile = wd + "dem.dep"
outputFile = wd + "output.dep"
maxGullyWidth = "25"
maxGullyDepth = "3.0"
minGullyDepth = "0.25"
dfmeThreshold = "0.0"
planCurvThreshold = "100.0"
smoothing = "5"
useNodataBackground = "true"
args = [demFile, outputFile, maxGullyWidth, maxGullyDepth, minGullyDepth, dfmeThreshold, planCurvThreshold, smoothing, useNodataBackground]
pluginHost.runPlugin("MapGullyDepth", args, False)
This is a Groovy script also using this tool:
def wd = pluginHost.getWorkingDirectory()
def demFile = wd + "dem.dep"
def outputFile = wd + "output.dep"
def maxGullyWidth = "25"
def maxGullyDepth = "3.0"
def minGullyDepth = "0.25"
def dfmeThreshold = "0.0"
def planCurvThreshold = "100.0"
def smoothing = "5"
def useNodataBackground = "true"
String[] args = [demFile, outputFile, maxGullyWidth, maxGullyDepth, minGullyDepth, dfmeThreshold, planCurvThreshold, smoothing, useNodataBackground]
pluginHost.runPlugin("MapGullyDepth", args, false)