Third, the DeGraff method is very sensitive to whether the mapping of "landslides' include the source area, the deposit, or both.
If the toes of long-runout landslides are not differentiated from source areas and are thus included in the inventory, the characteristics of the land beneath the toes become associated with landsliding.

Imagine a series of inventoried landslide that slid off a steep escarpment, with its toe resting on a gently sloping surface underlain by fan deposits; this exact situation occurs at the base of Jacks Hill.
Using the DeGraff method, low-angle fan deposits will be associated with all the slide pixels in the toe, a landslide density will be calculated for the class of low-angle fan deposits, and all low-angle fan deposits will be assigned that density, wherever they are in the study area.
Pixels on the margins of Kingston Harbour, far from any escarpment, would have the same slide density as the pixels at the base of Jacks Hill.
To voice this problem, we performed this DeGraff analysis only for landslide source areas.
However, the reader must understand that the areas downslope of pixels with high or very high susceptibility for initiating landslides may also have a high susceptibility for being the deposition site of debris.
This is especially true of large landslides (such as at Jacks Hill) or long-runout failures such as debris slides-debris flows.