Date of Award

12-1970

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Geography

Major Professor

Sidney R. Jumper

Committee Members

Edwin H. Hammond, John B. Rehder, Robert G. Long, G. Michael Clark

Abstract

Numerous debris slides and considerable flood damage resulted from the September 1, 1951, cloudburst over the Mt. Le Conte-Sugarland Mountain area in Great Smoky Mountains National Park. Over 100 individual slide scar heads were found in the study area, 41 of them in the Alum Cave Creek watershed, area of detailed field study.

The movement is thought to have been initiated by sliding at the head of the scar, with the mass of moving rock, soil, forest debris, and water developing flow characteristics downslope. Mt. Le Conte-Sugarland Mountain slide tracks may be divided into three sections: (1) the scar head, (2) the middle zone, and (3) the area of deposition.

Slide dimensions vary considerably. Nineteen slides within the Alum Cave Creek watershed were surveyed with a Wild RDS self-reducing tacheometer and sketched planimetrically at a scale of one inch to 50 feet. The scar head of Slide SB-10, largest within the study area, covers approximately 112,532 square feet and had an estimated removal of about 121,534 cubic feet of material. In contrast, the scar head of Slide ACC-3 occupies approximately 1,662 square feet and had about 2,160 cubic feet of material removed.

Slide scar heads in the Mt. Le Conte-Sugarland Mountain area are at elevations ranging from 4000 to 6300 feet. Field measurements in the Alum Cave Creek watershed indicate slope angles on individual scar heads range from approximately 35° to 44°, with a mean of 40°. Slides originated on all four quadrant exposures.

Slide location and distribution are controlled by the complex interaction of numerous physical and cultural factors. Because all known debris slides in the Appalachian Highlands south of the glacial border have been associated with heavy rainfall on steep slopes, intense or prolonged rainfall and slope angle must be considered the most important factors contributing to debris slide formation.

Precipitation is a critical localizing agent, but how much and how fast rain must fall to produce sliding is as yet unanswered; and computing an accurate recurrence interval for slide producing storms is nearly impossible. At best, a storm similar to the September 1, 1951, cloudburst probably has a recurrence interval of greater than 100 years, and possibly much longer, for the Mt. Le Conte-Sugarland Mountain area.

Detailed field investigation in the Alum Cave Creek watershed provided the basis for locating and mapping debris slides and related flood damage by using airborne imagery for the entire Mt. Le Conte-Sugarland Mountain area. Evaluation of the imagery indicated that Ektachrome Infrared Aero film is the best overall sensing medium for slope damage analysis in this particular area. Slide age and ground conditions vary considerably among the different slide areas in the Appalachian Highlands south of the glacial border, and other emulsions or sensing devices might prove better suited for investigating slop damage in these locations.

The need for further debris slide studies is apparent. All slopes are not hazardous; but few, if any, are stable in an absolute sense. If the various parameters of debris slide localization and distribution are understood, areas of slide potential can be determined.

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