The following images were included in a MS
PowerPoint presentation used by North Carolina
Geological Survey geologists from the Asheville
Regional Office at many public landslide
outreach meetings. The presentation has been
adapted to the Internet for broader
distribution. This page is on "Rock Slope
Landslides and landslide related fatalities
from the mid-July 1916 hurricane in
Transylvania County, NC. Damage from landslides
and flooding occurred over much of the
south-central mountain area. The July 15-16,
1916 flood is considered the flood of
record in western North Carolina.
Color-infrared aerial photograph of the Gorges
State Park area, Transylvania County, North
Carolina showing mapped locations of deposits
left by the catastrophic failure of Lake
Toxaway Dam on August 13, 1916. The dam failure
triggered a debris flow along the Toxaway River
that traveled over 7 miles and into South
Carolina. Lake Jocassee is underlain by cobble,
gravel and sand deposits from the flood. The
original dam was in about the same location as
the current dam. The quote shown is from S.W.
McCallie, State Geologist of Georgia at the
time. Studies by the North Carolina Geological
Survey estimate that the outflow just below the
dam was on the order of 293,938 cfs (discharge)
and 50 mi/hr (velocity). Information from
Geology of Gorges State Park, N.C. Geological
Survey Information Circular 31.
Top: View looking downstream along the Toxaway
River below the dam showing the assumed scour
lines and the location of cross section D
(bottom) used to reconstruct the super
elevation angle of the dam failure torrent.
This information goes into computing an
estimated velocity and discharge of the
Top Left: 60-foot long boulder weighing nearly
900 tons transported by the flood waters along
the Toxaway River from the August 13, 1916 Lake
Toxaway Dam failure. Photograph taken about 0.5
miles downstream from Toxaway Falls. Top Right.
Imbricated boulders at the crest of the boulder
levee shown in red in the cross section at
Bottom Left. Bottom Right. Photograph of the
contact (shown by arrow) of the boulder flood
deposits overlying pre-existing flood plain
deposits along the Toxaway River.
Left: Detailed map of a ~4 acre active
weathered-rock slide along the Toxaway River in
Gorges State Park. This slow-moving landslide
was probably triggered by the 1916 dam failure
torrent that eroded and over-steepened the
slope along the river. Right: Tree ring studies
of trees on and off the slide indicate a period
of slide movement during the 1965-1974
timeframe corresponding to a period of above
average rainfall. Tree ring studies were done
cooperatively with the U.S.F.S. Coweeta
Hydrologic Laboratory, Otto, N.C. Information
contained in Geology of Gorges State Park, N.C.
Geological Survey Information Circular 31.
Trees growing on an active landslide are
commonly curved. The tree tilts with the moving
slide, and over time attempts to regain
vertical growth resulting in the curved trunk.
A and B. Curved trees showing the effects of
movement on the Toxaway River weathered-rock
slide. White arrow points to person for scale
in photo A (left).
Field developed cross section view of the
Toxaway River weathered-rock slide in Gorges
State Park. Information contained in Geology of
Gorges State Park, N.C. Geological Survey
Information Circular 31.
Left: Example of landslide
hazard mapping. Slope movements (landslides),
flood and other surficial deposits mapped in
Gorges State Park by the N.C. Geological
Right: Bedrock geologic map of Gorges
State Park. Mapping landslides and surficial
units along with bedrock provides the best
geologic framework for constructing landslide
hazard maps. Information contained in Geology
of Gorges State Park, N.C. Geological Survey
Information Circular 31.
Center: Schematic block diagram showing
the relationships between bedrock structure,
streams, and slope movements for Gorges State
Park, Transylvania County, N.C.
For additional information
about landslide hazards in North Carolina,
please contact Mr. Richard Wooten
with their Asheville Regional Office:
2090 U. S. Highway 70,
Swannanoa, North Carolina 28778.