I have raster DTM image of lidar data, mapped to Washington state plane north (US survey feet), where each pixel represents an elevation value in feet.
Generating a "slope map" which shows all of the areas with slopes equal to or greater than 40% is easy enough.
However, what I really want to generate is a map that shows slopes with an average incline of 40 percent or more, that also have an elevation of change of at least 10 feet within a horizontal distance of 25 feet. For the purpose of this definition, a slope area is where the ground surface drops (or rises) 10 feet or more vertically within a horizontal distance of 25 feet.
Currently I am generating a slope map, then generating 10 foot contours, and manually identifying areas that meet the criteria. There has to be a better way, but my QGIS skills are not up to the task. Can anyone please point me in the right direction.
Thanks in advance.