RESIDENTIAL LANDSLIDE STUDY, ERWIN, TENNESSEE

Landslides are a constant threat in the mountains of East Tennessee and a major concern for property owners. This study reports on a monitoring project for a landslide site with three previously known debris flow events which also incorporated some bedrock. The site is located on a residential driveway on the side of Buffalo Mountain, Erwin, Tennessee and has a number of risk factors that suggest further movement is likely and that even the residence is at serious risk. The cabin foundation and drive way are cut into a steep (50^˚) slope and sit approximately 20 m above an access road that parallels North Buffalo Creek. The base of the hill has been over-steepened by construction of the access road. The hill has been further destabilized by removal of vegetation to enable a view of North Buffalo Creek, by poorly directed drainage from the cabin roof, and by recent animal burrowing activity. The house is located directly over the Buffalo Mountain thrust and on well bedded Cambrian dolomites that both dip subparallel to the hill slope. A large exposure of the dolomite 300 m down strike from the cabin has a well-documented history of slides that have closed the access road several times. The bedrock is overlain by 2.5 m of coarse gravels which have produced at least three debris flows in the last 10 years and large trees, above the debris flow scar and house, which exhibit evidence of creep. A grid of steel pin targets were placed across the site to monitor activity with a laser range finder every two weeks. Additional monitoring was carried out with a time lapse camera directed at the center of the debris flow scarp with a number of boulders painted day-glow orange in order to document motion. A rain gauge was installed to track rainfall amounts and determine possible correlation between rain events and slope movement and soil hydrometer tests have been used to evaluate soil saturation. In addition, digital elevation models have been used to determine drainage patterns in and around the landslide area in order to better understand the origin of the slides. Pin data results indicate that there has been an average of 50 mm of downslope motion over the first six months of the study and boulders in the debris flow have moved an average of 5.0 m.