USING A SPATIALLY DENSE, HIGH ELEVATION RAIN GAUGE NETWORK AND A HYDROLOGIC MODEL TO ENHANCE PREDICTABILITY OF LANDSLIDES IN THE SOUTHERN APPALACHIANS

The Southern Appalachians have historically been prone to devastating landslides, especially debris flows, which damage infrastructure and have caused fatalities. Most of the debris flows in the Southern Appalachian Mountains are induced by heavy rainfall. During these events, the pore water pressure in soils on steep slopes overcomes the shear strength of the soils, causing the slopes to become unstable. Thus the accuracy of spatial-temporal rainfall and the subsurface physics of soil wetting are two key factors needed to capture the dynamics of slope movements. Since 2007, a spatially dense, high elevation rain gauge network has been recording observations in the upper Pigeon River Basin to investigate the 4D distribution of precipitation in the region. The rain gauge observations are used to characterize the spatial-temporal error structure of radar-based Quantitative Precipitation Estimates (QPE) and to improve QPE for hydrological modeling. The objective of this study is to explore the triggering mechanisms of landslide hazards (especially debris flows) induced by heavy rainfall on headwater catchments of the upper Pigeon River in the Southern Appalachians using a 3D coupled surface-groundwater hydrologic model. Specifically, we will focus on the Jonathan Creek Basin in the upper Pigeon River Basin, a vulnerable headwater catchment that experiences frequent debris flows. The relationships between slope stability and soil moisture conditions are characterized for the specific geomorphologic features in the catchment. A deterministic method is proposed for predicting landslide trigger locations based on simulations of three-dimensional soil moisture and analysis of slope stability within the catchments. Preliminary results from the proposed methodology are compared with a survey of landslide locations that have occurred since 2007.