AEOLIAN EROSION AND GULLY FORMATION IN A HUMID SUBTROPICAL CLIMATE

Aeolian erosion is generally considered to be associated with arid and semi-arid climates, and is the process by which wind effects geomorphology. Less is known about wind erosion in humid climates and therefore this study quantifies soil erosion in a system of gullies that formed on ultisol soils in the Valley and Ridge physiographic province in Washington County, TN, USA. Its purpose is to evaluate the relationship between aeolian processes and the propagation of gullies in humid subtropical environments. A network of 91 erosion pins installed in gully interfluves, sidewalls, and channels were measured weekly from 2012 through 2015. Wind data (average speed, maximum gust, average direction, and direction of high wind speed) were collected using an on-site weather station at five minute intervals, and aggregated to weekly measurement period. Changes in pin length from week to week (response variable) were correlated to wind speed and directional data (explanatory variables), and were found to be positively correlated with erosion in gully interfluves and sidewalls. Due to collinearity between the explanatory variables, Principal Components Analysis (PCA) was used to generate two new orthogonal factors representing wind speed and wind direction. Ordinary Least Squares (OLS) regression models for erosion in interfluves and sidewalls were generated using the two new factors to create a predictive model of gully formation based on aeolian data. OLS regression models successfully explained up to 20% of the variability in the erosion data. Prior research at this site has shown that precipitation and freeze thaw are significant drivers of erosion at gully channels and sidewalls. The present study suggests that aeolian processes are important erosional agents for gully sidewalls and interfluves. Hence, several erosional agents are responsible for gully propagation at different morphologies, and should be considered in future erosion studies in humid climates.