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1. J. David Rogers
INTRODUCTION TO
SLOPE STABILITY
AND
LANDSLIDES

2. • Landslide susceptibility map of the continental United
States, taken from the U.S. Geological Survey.
• Worldwide annual landslide losses cost between
US$10 and 20 billion per year, causing on average,
about 1,000 deaths per year in the CircumPacific
countries (from Schuster, 2003).

3. Part 1
BASIC CONCEPTS
OF SLOPE
EQUILIBRIUM

4. Slopes in equilibrium with their
environment typically exhibit
concave, straight, and convex
hillslope profiles shown at left.
Slopes out-of-equilibrium typically
exhibit anomalous, hummocky
profiles, shown at right
Concepts of Equilibrium

5. Stepped
Topography
• Stepped topography is not necessarily indicative of
slope instability, but can be structurally controlled by
underlying stratigraphy, as shown here. Shales are
most often associated with landslides.

6. Out-of-
Equilibrium
Slopes
• Slopes that are
experiencing
rampant erosion
are typically out-
of-equilibrium, and
exhibit truncated
concave slope
profiles, shown at
left.

7. • The slope profile is also
influenced by runoff
requirements and the
relative position of
controlling base level, as
sketched here.
• Note change in hill profile
as channel moves away
from the ridgeline

8. Beginning of an erosive cycle. Note slight changes in hillslope profile

9. Continuation of an erosive cycle, with gradual shift of the hillslope
profile, resulting in hummocky topography. Hummocky slopes are
typical of slopes experiencing landslippage.

10. EXAMPLES OF HUMOCKY
TOPOGRAPHY
Hummocky topography
is usually indicative of
solifluction or active
landslippage