Debris Slides and Related Flood Effects in the 4-5 August 1938 Webb Mountain Cloudburst: Some Past and Present Environmental Geomorphic Implications
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University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 12-1974 Debris Slides and Related Flood Effects in the 4-5 August 1938 Webb Mountain Cloudburst: Some Past and Present Environmental Geomorphic Implications Carl A. Koch University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Geology Commons Recommended Citation Koch, Carl A., "Debris Slides and Related Flood Effects in the 4-5 August 1938 Webb Mountain Cloudburst: Some Past and Present Environmental Geomorphic Implications. " Master's Thesis, University of Tennessee, 1974. https://trace.tennessee.edu/utk_gradthes/3239 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Carl A. Koch entitled "Debris Slides and Related Flood Effects in the 4-5 August 1938 Webb Mountain Cloudburst: Some Past and Present Environmental Geomorphic Implications." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Geology. G. M. Clark, Major Professor We have read this thesis and recommend its acceptance: Don W. Byerly, Garrett Briggs Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the·Graduate Council: I am submitting herewith a .thes is written by Carl A. Ko ch entitled "Debris Slides and Related Flood.Effects in.the.4-5 Augus t 1938 Webb Mountain Cloudburst: Some Past · and Present Environmental Geomorphic Implications ." I recommend that it .. be accep ted in partial fulfillment of ·the requirements for the degree of Mas ter of Science, with a major in Geology. G M. C� . G. M. Clark, Ma jor Professor We have read this thesis and recommend its acceptance : &..u. (!.,;Po Accepted for the Council: Vice Chancellor . Graduate Studies and Research DEBRIS SLIDES AND RELATED FLOOD EFFECTS IN THE 4-5 AUGUST 1938 WEBB MOUNTAIN CLOUDBURST : SOME PAST AND PRESENT ENV IRONMENTAL GEOMORPHIC IMPLICAT IONS A Thesis Presented for the Master of Science :pe�ree The·University of Tennessee Carl A. Koch Decemb er 1974 ' ACKNOWLEDGE�NTS The writer wishes to express hi� sincere appreciation to all the p�ople who assisted in making this study possible. He espec;tally wi�hes to express his gratitude to his committee chairman, Dr. G. Michael Clark . The·writer ac�nowledges indeb tedness tp the Departm,ent of Defens e for the financial assistance which made part of this·study possible. He also thanks committee members Dr . Garrett Briggs and Pr . Don W.' Byerl.y for their suggestions in the development of this thesis. In addition, the writer is grateful to num�rous individuals who contributed tp this study. T�anks go to,Dr. Otto Kopp� Department of Geology , Un�versity of Tennessee ; Mr . Glenn Cardwell, Natipnal Park Service; Mr . B. C. Moneymaker , Mrs . Eleanor Southern , ancl Mrs. Margaret W�secarver , Tennessee Valley Authority ; invaluable field assis tance was provided by Mr . Joe R'-:lzicka , Mr . Eric Og}.esby, Mr . Don Bogucki and Mr . John, Rishel . Spec!al thanks are extended tq my wife for her invaluable assis tance and support. ii ABSTRACT On th e night of 4-5 August, 1938 a cloudburst occurred over.Webb Mountain , Tennessee, tha t lasted thr ee hours with a _rainfa ll in ex�ess of twelve inches . This sudden qeluge ca�seq co� siderable debris sliding and fl9oding which result�d in the loss. of eight' lives and extensive l ' property damage in the narrow valleys be low- the slide area . Over 100 individual slide scars were id en tifieq in the study area, 40 of which oc�urred in the Matthew Creek wa tershed . The_debris slide mo vement is thought to have been initiated by sli4ing at the �ea� of th e scar, with the mass of moving rock, soil and _ fo�est debris remaining intact and then developing into a de bris flow as it progr essed downslope. The.major vo! ume of material was ca rried out of the uppe� stream channels and slide tracks and deposited in the lower reaches of th e st�eams . Intense summ er �ains torms are the major cause of debris slides in ' the,Appa!achian Highlands south of the glacial border . Complex cult�ral and physical factors interact to affec t an individual slide location. Pr ecipitation is a c� itical localizing factor. as well as �he rate of water !�f iltration whi ch increa�es. the �oil pore pressur e very rapidly during intense rainfall, such t� at so� l a�d regolit� fail by sudden reduct ion in their shearing st�ength . Careful field inves tigation was · the met�od of ob taining detaileq , data on t�e �lide areas. All slides were plo tted on a large map of the en tire area. The Ma tthew Creek slide area wa s the center of detailed fi i iv Evaluation of several types of imagery indicated the Ekatachrome I� frared Aero film to be the mo st us eful. The look angle , altitude a� d vegetational foliage are important factors in defining the slide scars with aerial phot�graphy. The accum�la tion of data over lo�ger time intervals will improve recurrence interva� proj ec tions . Fur ther deb+ is s� id e st�d ies will add to t�e unde�� tanding o{ slide leG alization and dis tr ib ution factors and areas of slide potential can better be determined . TABLE OF CONTENTS CHAPTER PAGE I. INTRODUCTION • 1 Statement of the Problem • 1 Data Collection and Analysis . 3 Historical records 3 Field research data. 0 3 Airborne imagery 4 II. THE STUDY AREA • .. 6 Location • 6 Relief and Drainage. 6 Bedrock Geology. 7 Climate. 10 Soils. 14 Vegetation 15 Settlement and Economy 0 16 IIL MASS MOVEMENT. 18 Introduction • .. 18 Classification • 18 Terminology. 0 18 Distribution • 23 IV . CLIMATOLOGICAL AND GEOMORPHIC EVENTS ON ·THE NIGHT OF 4-5 AUGUST 1938. 25 Introduction • 25 v vi CHAPTER PAGE The Storm. 25 The Floods • 27 Slid� Characteristics. 29 Slope,gradients. 29 Distribution and orientation 31 General description. '• 33 Flow track, erosion, and deposition. ·• 37 Water blowouts • ' • . 38 v. POST SLIDE RECOVERY (AS OF 1974) .. 44 Introduction · , . 44 Soils. 44 Revegetation 52 Interpretation and Evaluation of Airborne Imagery. 58 VI, PLAUSIBLE SLIDE LOCALIZING FACTORS AND ORIGINS • 70 Introduct�on • · , .. 70 Meteorological and Climatological Factors. 70 Slope and Other Geological Factors • 73 Pedological and Vegetational Factors 75 Cultural Factors • . 80 VII. SUMMARY AND CONCLUSIONS. 90 BIBLIOGRAPHY . 96 APPENDICES 101 . Appendix A . •. 102 Appendix B • .. 103 vii CHAPTER PAGE Appendix C • 108 VITA • 112 LIST OF TABL ES TABL E PAG E I. Stratigraphic Units of Oc oee Series in the Great Smoky Mountains • . ' . ... 11 II. Annual Temperature Data for Gatlinburg . 13 III. Mass Movement Classification by c. F. Stewart Sharpe, 19 IV. Ma ss Movement Classification by David J. Varn es ••• • ' Cl • 20 V. Discharge Data for the Webb Mountain Area 4-5 August, 1938 . 28 · I VI . Range·of .Sl ope Steepness in Debris Sl ide Ar eas of Webb . Mountain. • . ·. • . 30 VII. Aspect (Fac ing Direction) of Slopes with Sl ides in the Webb Mountain Debris Sl ide Area • • • • • 0 • . 32 VIII. Emulsion/Fil ter Comb ination and Sc anner Facilities Used on Rem ot e Sensing Missions over Webb Mountain • • • ·• 68 viii LIST OF FIGURES FIGURE PAGE 1. Map of Great Smoky Mountains Region , Tennessee and North Carolina . ·. .. · . 2 2. General Drainage Map of the Webb Mountain Area •••· • • • • • 8 3. Sc�ematic Block Diagram Illustrating t�e Terminology Used for Features Produced by Rapid Mass Movements • ·• •• 22 4. Index Map , Appalachian Debris Slide Areas South of the Glacial Border. • • • • • • , • • • • ·• • • • ·• • • • .. 24 5. A Debris Slide Scar near the Upper End of Matth�ws Creek. 34 6. Debris Slides at the Head of Draw No. 3 (Plate 1) in the · Matthew Creek Slide Atea •••• . 36 7. Erosion of a Channel in the Upper End of Matthew Creek , · Looking Upstream. • • , • • • • • • • ·• • • • ·• • 39 8. Boulder Deposits in the.Main Channel of Draw 4 (Plate 1) . 40 9. A Small Water .Blowout Along Webb Creek, Above Pittman Center . 42 10. A L�rge Water Blowout.Ne.ar the M.outh of Jones Branch.·. • • • 43 11. Bedrock Exposed �n the Head of a Debris Slide Scar, Located in the Matthew Creek Slide Area • • • ·• • • • 4 7 12. Rock Deposited in'.Matthew Creek �elow the Mouth of Draw 3 (Plate 1), which can be Seen,in the Extreme Right Hand Side of the Picture • • • • • ·• . .. 49 13. A Recent View of the Rock Debris Shown in Figure 12, page 49. 50 14 . A Recent View of a Debris Slide Scar at the Head of Dr�w 3 (Plate 1) in the Matthew Creek Area . 54 ix X FIGURE PAGE 15. A Debris Slide Scar Located near the Head of Draw 5 · (Plate ·1) in the Matthew Creek Area •••••• • ••·• • • 56 . 16. A Water Blowout S�ar in the Lower Part of Draw 4 (Plate 1) in the Matthew Creek Area • • • . 57 17. A Water B.lowout Scar Located Above the Head of Draw 4 (Plate .1) in .the Matthew Creek Area • • • ·• • • • ·• 59 18. Revegetation of a Channel Lpcated in Draw 5 (Plate 1) in the Matthe� Cre� Area.