Aeolian influences on gully erosion in clay-rich soils in a humid subtropical climate, Southeast USA

Abstract

This study evaluates aeolian processes as significant but overlooked factors in runoff-driven gully erosion in humid subtropical climates. A network of 105 erosion pins installed in gully channels, interfluves, and sidewalls on an eroding hillslope in southern Appalachia was monitored weekly (2012–2018); concurrently, meteorological data were collected on site every 5 min. Wind variables were aggregated to weekly periods and statistical analyses (correlation, autocorrelation, Ordinary Least Squares (OLS) regression) were performed to (i) determine impacts of wind and wind-driven rain on gully erosion, (ii) assess seasonal gully erosion patterns relative to wind and wind-driven rain, and (iii) evaluate slope aspect effects on erosion of gully sidewalls. Annual OLS regression models for gully erosion using wind variables had low explanatory power (adjusted R2 = 0.067 (channels) to 0.197 (sidewalls)). The greatest gully erosion activity occurred in winter and spring aligning with periods of highest wind speeds; seasonal erosion and wind patterns were confirmed with autocorrelation. Seasonal OLS regression models had higher explanatory power (adjusted R2 = 0.044 to 0.367), with strongest models in autumn, suggesting seasonal importance of wind-related drivers for gully erosion. Southwesterly prevailing wind direction was normal to the gully axis, suggesting influence of slope aspect; higher erosion rates were recorded in the windward sidewalls but differences were statistically insignificant. Though rainfall and freeze–thaw activity are primary drivers of gully erosion in southern Appalachia, this analysis confirms that seasonal aeolian processes are significant contributors. These results may be used to improve standard predictive models of gully erosion in humid subtropical climates.