Peeks-Creek-Debris-Flow-2004

Peeks Creek Debris Flow, 2004

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. Scroll down for more information.

Landslide presentation

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 the "Peeks Creek Debris Flow, Macon County, North Carolina - September 2004." Links to other topics appear in the contents shown above.

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 an 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.

Aerial shot of damage due to an earth slide

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 rescue residents.

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.

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

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.

Upper Right 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 modified roads.

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.

Contact Information

For additional information about landslide hazards in North Carolina, please contact Dr. David Korte with our Asheville Regional Office:

2090 U. S. Highway 70,
Swannanoa, North Carolina 28778.
828-296-4540
david.korte@deq.nc.gov