The 1999 Landslide of
Avalanche Pass
• Andrew Duling Mary Blackwell
The site of
the slide
High Peaks Region
Adirondacks, NY
What
Happened
Here???
•199,700 cubic meters slid
•Removing soil and
vegetation
• Exposing anorthosite
bedrock
•Characteristics of a debris
avalanche
What Caused the Slide?
Hurricane Floyd
4.26 inches in less 24 hours
Thin soil layer
Weak soil structure
Failure at the bedrock soil interface
The Precipitation
Table 1: The yearly maximum rainfall events occurring in a
single day. In 1999 the max rainfall for a single day was 4.26
just before the slide. Data was collected at the Lake Placid
weather station
Hurricane Floyd
Hurricane Floyd percipitation as a percentage of
1999 total percipitation
10%
Hurricane
Floyd
90%
Table 2: Hurricane Floyd's rainfall as a percentage of the 1999 yearly total
Conclusions
The large slide of Avalanche Pass was caused
by steep slopes and an abnormally large
amount of rain which caused the bedrock soil
interface to fail.
Further study and monitoring of the area is
suggested while no one was injured in this
slide the potential for similar slides in the area
exists and with that risks to lives and property.
Discussion