Kansas Geological Survey, Current Research in Earth Sciences, Bulletin 244, part 3
The Relationship Between Geology and Landslide Hazards of Atchison, Kansas, and Vicinity--Fig. 13

Fig. 13. The frequency of recent landslides for a given slope angle. The frequencies were determined by counting the number of landslides for 5-degree intervals of slope angle. The average slope angle for recent landslides is 22.2 degrees.