This section provides an overview of the Peeks Creek Debris Flow
at Macon County, North Carolina in September 2004. Five people
were killed, two persons were seriously injured and 15 homes were
destroyed on September 16, 2004 about 10:00pm
The landslide section consists of several pages to facilitate on-line
user viewing. This page is the fourth of five that are based on a recent
staff geologist presentations at numerous public meetings. The pages
The following images were included in a MS PowerPoint presentation
used by North Carolina Geological Survey geologists from the Swananoa
office at many public landslide outreach meetings. The presentation
has been adapted to the Internet for broader distribution. This page
is on the "Peeks Creek Debris Flow, Macon County, North Carolina
- September 2004." Links to other topics appear in the contents
Slide numbers correspond to those of the original MS PowerPoint presentation.
Slide numbers "missing" are slides that were turned into text.
Captions are from the original presentation.
|Slide 89 - Notes from preliminary NCGS investigations
of the Sept. 16, 2004 Peeks Creek debris flow in Macon County. Arrow
points to initiation zone of the debris flow. Peak just to the left
of arrow is Fishhawk Mountain
|Slide 90 - Calculating estimates of the velocity
and discharge of the debris flow helps to give at idea of why this
debris flow was so destructive. Because a debris flow moves like
a viscous liquid, it banks as it rounds a curve in the stream channel.
We can calculate an estimate of the velocity based on that banking
angle, the channel gradient and the radius of curvature of the bend
in the channel. Velocity and discharge estimates were calculated
at 6 places along the debris flow track where cross sections were
constructed. Maximum velocity calculated is 33 mph at section H
and maximum discharge calculated is 45,000 cfs also at section H.
Section H is located at the downstream end of the steep incised
section previously mentioned. To put the discharge value into perspective,
the Swannanoa River in Asheville caused considerable flood damage
to Biltmore Village during Hurricane Frances. The peak discharge
at the Swannanoa was approximately 13,000 cfs.
|Slide 91 - Bottom Left: The September 16, 2004 Peeks
Creek debris flow scoured the stream banks revealing evidence of
at least two previous (prehistoric?) debris flow deposits in the
channel. Top Center: Field developed cross section shows the layering
observed in the channel also seen in the bottom left photograph.
Bottom Right: Photo shows an up close view of these deposits which
consist of crudely imbricated boulders in a orange-brown silty matrix.
|Slide 92 - Aerial view of damage along Peeks Creek
caused by the Sept. 16, 2004 debris flow.
|Slide 93 - Aerial shot of some of the damage shown
in the previous slide. The red arrow points to the location of fatalities,
and the red line indicates the boundary of the debris flow track.
You can see the damage done to the road that paralleled the old
stream channel. The channel is actually in a new location now. You
can see how difficult it most likely was to get up the channel to
|Slide 94 - Another aerial shot of the Peeks Creek
community. This is just downstream from the image shown in the previous
slide. The white house shown in the inset had a few mud splatters
on it but was not damaged. The arrow points to its location in the
air photo. Setbacks from the creek could have reduced damage and
possibly saved some lives.
|Slide 95 - Close-up view of Fishhawk Mtn. showing
the initiation zone of the Sept. 16, 2004 Peeks Creek debris flow
(Sept. 19, 2004 NCGS photo). Inset: Rock slope exposed in the scar
dips from about 30-50 degrees. Shallow groundwater seepage from
the soil-bedrock contact is visible on the rock slope.
|Slide 96 - Scratch marks and grooves caused by rock
fragments in the soil sliding over the bedrock surface now exposed
in the scar of the Peeks Creek debris flow near the top of Fishhawk
Mtn. Scribe points downslope.
|Slide 97 - Peeks Creek Debris Flow. Views of imbricated
large boulders deposited by the Peeks Creek debris flow. Some of
the larger boulders moved by the debris flow weigh on the order
of 16 tons.
|Slide 98 - Ancient imbricated debris flow deposits
exposed along the debris flow track of the Peeks Creek debris flow
(downstream to left).
|Slide 99 - Peeks Creek Debris Flow. Top: Destroyed
home located on the outside bend of the stream channel. Bottom:
Imbricated boulders deposited in the stream channel by the Sept.
16, 2004 debris flow. The large boulder here weighs nearly 16 tons.
|Slide 100 - Peeks Creek Debris Flow. Top Left. Edge
of grass marks the discrete line of the edge of the debris flow
in front of this spared home. Most of the debris flow deposit has
already been removed from the front yard. Top Right: Former two-story
home pushed 30 feet off its foundation by the debris flow. Bottom
Left: Destroyed automobile. Three people were killed at this location.
Bottom Right. Two homes destroyed by the debris flow. After being
pushed nearly 200 ft downstream by the debris flow, the home on
the right collided with the home on the left.
|Slide 101 - This graph shows rainfall amounts in mm
on left and inches on right for 5 different rain gauges at various
elevations with lower elevations in red and higher elevations in
blue from September 1 to September 18. This seems to indicate that
at least for these two storms, higher elevations received more rainfall
than lower elevations. Mooney Gap shown in dark blue is at a similar
elevation to Fishhawk Mountain and received approximately 10.5 inches
during Frances and another 11 inches of rain during Ivan.
|Slide 102 - This radar image is from the National
Weather service office in Greer, SC who is responsible for forecasting
weather for much of western North Carolina. It shows a strong storm
cell associated with Hurricane Ivan that passed over Fishhawk Mountain
at approximately 9:48 p.m. This cell had a history of producing
a tornado in Georgia. Macon county is outlined in black, and the
white dot with “Home” written next to it is Fishhawk Mountain.
|Slide 103 - Current work on documenting historical
landslides in Macon County, the pilot study county. Top and Bottom
Right: Track and initiation zone of Hurricane Ivan debris flows
near Wayah Road. Bottom Left: Upper track of Poplar Cove debris
flow – Hurricane Opal, Oct. 5, 1995.
|Slide 104 - Other ongoing activities in the landslide
hazard mapping program. Top Center: Photograph of multiple prehistoric
debris flow and flood deposits exposed in the channel scoured a
debris flow near Wayah Creek in Macon County during Hurricane Ivan.
Bottom Left and Right: Initiation zone of the Sept. 16, 2004 Peeks
Creek Debris flow.
|Slide 105 - Data compilation phase in which geologic
and soil maps, and other data are brought into the GIS environment.
|Slide 106 - This is a map showing different hazards
associated with the various soil types as mapped by soil scientists
(digital soil survey of Macon County) which is one map NCGS will
provide to the 19 declared counties of the Hurricane Recovery Act
of 2005 as part of the Landslide Hazard Mapping project. A strong
correlation between the locations of known slope failures (shown
in yellow) and the soils shown in dark red which have been determined
to be associated with landslides. Some slides do not appear to correlate
with landslide prone soils for two reasons: 1. Small areas of landslide
prone soils may not show up at this scale, or have not been mapped.
2. Slopes modified since the soil survey was done may fail due to
modifications and not necessarily due to soil type.
|Slide 107 - This is a slope map, another deliverable
we would provide to each county in a digital format. This map is
important because slopes greater than approximately 30 degrees are
more prone to landslides. This map shows the variations in slope
with flat slopes shown in blue and steeper slopes shown in the greens
and yellows. There is a fairly good correspondence between known
slope movements and steep slopes; most occur in the yellow and green
colors (steeper slopes). Landslides on the map that occurred in
blue/flatter areas could be embankment failures along rivers or
|Slide 108 - Preliminary Stability INdex MAP analysis
for Macon County. SINMAP is one program we plan to evaluate to model
the potential for slope failures such as shallow translational landslides
like debris flows and debris slides. It is a GIS-based program that
uses parameters such as slope angle; the soil properties - thickness,
shear strength, transmissivity; and, vegetative cover (root cohesion)
to assign a probability for failure. Areas in red are considered
unstable and areas in green are considered stable. It is important
to inventory landslides to help calibrate the model. For example,
known landslides should plot in the least stable areas of the map.
The inset shows that this preliminary run correlates fairly will
with the known landslide locations.
See: Pack, R. T., Tarboton, D. G., and Goodwin, C. N., 1998,
Terrain stability mapping with SINMAP, technical description and
users guide for version 1.00: Terratech Consulting Ltd., Salmon
Arm, B. C., Canada, Report Number 4114-0, 68 p.
For additional information
The contact for additional information about geologic hazards in North
Carolina is Mr. Richard Wooten, P.G.; his e-mail is Rick.Wooten@ncmail.net.
He is located in the Swannanoa, North Carolina office (western North
Carolina) and can be reached by telephone at 828.296.4500. His mailing
address is: 2090 U. S. Highway 70, Swannanoa, North Carolina 28778.
An alternate North Carolina Survey staff geologist contact is Dr. Jeff
Reid, P.G., 512 North Salisbury Street, Raleigh, North Carolina, 27699-1612.
His telephone number is 919.733.2423 x403. His e-mail is Jeff.Reid@ncmail.net.