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Mass movements are one of the most important geological processes for shaping up the morphology of the mountainous highland slopes. A slope becomes unstable when the acted force on the surface of the slope exceeds the shear strength of the slope forming materials. Most highlands have experienced at least one type of slope failure under critical landslide causing conditions and triggering factors such as rainfall and earthquake (van Western, 1993). Debris-slide and debris-flow are the predominant forms of slope failure in the Appalachian region. Debris-slide takes place when broken rock fragments mixed with plant debris, soil and water move downslope due to gravitational pull and might turn into a debris-flow with increase in the water content. More than 3000 rapidly moving slides have been recorded in the southern Appalachian Highlands, which have directly caused nearly 200 deaths since 1940 (Pariseau & Voight, 1979; Scott 1972; Wooten et al., 2016), and posed serious damage to houses, road networks, and federal properties.
Debris-slides in the Appalachian region are mainly triggered by torrential rainfall associated with severe storms (Wieczorek, et al., 2000) that increases pore water pressure in the soil cover and rock discontinuities (Eshner & Patric, 1982; Hupp, 1983), which facilitates the movement of the materials. Slope movements in the Great Smoky Mountain National Park (GRSM) area initially starts as slides at the scar head and flowage becomes the main mechanism as it moves rapidly along the drainage system towards the lower reaches of the mountains (Bogucki, 1970). For debris-slide risk assessment, it is important to identify potential slides initiation areas. One of the effective ways to identify such areas is to create a debris-slide susceptibility map. Debris-slide is a complex geological phenomenon that depends on several factors such as elevation, lithology, topographical slope angle, soil type, hydrological condition etc. in varying degree of influence (Ghosh et al., 2013). Therefore, it important to understand the interrelationship between occurrences of debris-slide and associated causative factors. The role of these causative factors, also known as geo-factors, can be determined by examining the areas where debris-slides have taken place repeatedly in past (Jones, 1992). Debris-slide susceptibility map predicts the spatial extent of future debris-slide with the assumption that the factors, which have caused debris-slides in the past, will cause sliding in the future under critical geo-environmental conditions (Carrara et al., 1995; Guzzetti et al., 1999). This makes debris-slide or any form of slope failure to be a predictable geo-hazard (Jones, 1992). Nevertheless, effective role of the geo-factors can change considerably based on the physical and geological condition of an area (Ghosh et. al, 2013).