AEOLIAN INFLUENCES ON GULLY EROSION IN CLAY-RICH SOILS IN A HUMID SUBTROPICAL CLIMATE OF SOUTHEASTERN USA

Aeolian erosion is a significant but overlooked factor in gully erosion in humid subtropical climates. Prior studies of a gullied hillslope in east Tennessee Ultisols found that up to 10% of the variability in erosion was due to wind. In this study, a six-year soil erosion dataset of weekly in-situ measurements was analyzed to further assess the impact of average and maximum wind speed, average and maximum wind direction, and wind-driven rain on gully erosion. The study also aimed to identify seasonal wind erosion patterns and examine lee and stoss effects on gully sidewalls based on slope aspect and relative wind direction. Erosion pin measurements grouped by gully morphology (channels, interfluves, or sidewalls) revealed the most active areas for erosion and deposition were gully channels, followed by sidewalls, and interfluves. Wind speeds were highest in winter and spring, with a consistent southwesterly wind direction across gully strike. Autocorrelation of erosion data indicated a seasonal pattern for all gully morphologies, with greatest erosion rates in winter and spring; this matched seasonal wind speed autocorrelation patterns. Spearman correlation coefficients for erosion and wind variables indicated maximum wind speed was the most important variable explaining erosion. Ordinary Least Square regression (OLS) models of erosion parameters produced significant regression models with adjusted R² ranging from 0.046 to 0.105 across gully morphologies. Retained variables in OLS models were maximum wind speed and average wind direction for channels and sidewalls, and maximum wind speed and maximum wind direction for interfluves. Stoss and lee effects were not a major process for aeolian erosion at this site. Erosion studies for humid climates emphasize the effects of wind-driven rain, but addition of wind-rain interaction variables to represent this process did not improve regression models. Although small, the significant gully erosion attributed to wind variables in this study shows the importance of aeolian processes as a factor in gully erosion in humid subtropical climates. This finding may be useful in development of mitigation strategies for gully erosion and has potential to improve standard predictive models of gully erosion in humid subtropical climates.