Effects of Landslide Disturbance on Soil and Vegetation in a Steep Landscape in Central Virginia

In the central Appalachian Mountains, landslides and debris flows are major geomorphic agents and natural hazards. A prominent example occurred in 1969, when the remnants of Hurricane Camille triggered over 150 debris flows in Fortune’s Cove, a first-order drainage basin in Nelson County, Virginia. These debris flows stripped colluvium and trees from hollows, yet the landscape responses are incompletely understood. To address this gap, we surveyed three hollows in Fortune’s Cove to determine the geomorphic context for debris flow initiation and to compare soil depth and woody plant communities between areas impacted by historical debris flows and undisturbed reference sites. Soil regeneration was spatially heterogeneous: some disturbed sites showed predominantly exposed bedrock (<2 cm soil) while others had soil profiles >10 cm thick; soils at undisturbed sites were all >80 cm thick. Vegetation surveys showed distinct composition and structure between the disturbed and reference sites: Sweet birch (Betula lenta) and tuliptree (Liriodendron tulipifera) dominated the overstory at disturbed sites, while tuliptree, sassafras (Sassafras albidium), and snags dominated the reference sites. Topographic analysis indicates that for the same slope, the transition between the signatures of hillslope and fluvial erosion processes occurs at much lower drainage areas (10^3 to 10^4 m^2 ) compared to drier, less vegetated areas from other studies (10^5 to 10^6 m^2 ). This case study suggests that debris flows cause persistent changes to soils and forests, which can inform land management practices in the context of precipitation changes in the Appalachian region driven by global climate change.