QUANTIFYING GULLY EROSION IN WEST TENNESSEE USING HIGH RESOLUTION LIDAR DATA

This research demonstrates the use of Light Detection and Ranging (LIDAR) for detailed measurement of volume change and erosional and depositional processes within a small gully and assessing the impact of digital elevation model (DEM) resolution on these measurements. The study site is an active gully in Meeman-Shelby Forest State Park in Tennessee, USA. DEMs were derived from an airborne LIDAR survey and multiple terrestrial LIDAR scans. DEM differences were used to quantify gross volumes of erosion and deposition within the gully over a three year period and a 49 day period. Analysis of the airborne LIDAR point cloud indicated that approximately 10,000 m³ of material eroded from the bluff since the gully was formed between 1969 and 1973. A total volume of 615.8 m³ of material was discharged from the gully between January 2012 (the airborne LIDAR survey) and December 2014 (the first terrestrial LIDAR survey). The surveys using the terrestrial laser scanner generated two 2 cm DEMs representing the gully terrain change during a short period of 49 days between December 2014 and February 2015. The comparison of these two DEMs indicates an estimated 2.1 m³ of material was imported into the gully with 11.5 m³ of gross erosion and 13.6 m³ of gross deposition. The DEM scale analysis indicates that turning points exist in the trends of erosion and deposition estimates at 0.18 m and 0.28 m resolutions, respectively. These turning points represent the resolutions at which the accuracy of erosion and deposition measurements begin to deteriorate and are revealed by examining the strength of linear fits to data points on either side of the turning point. The analyses described in this thesis offer insight into the benefits and challenges of using LIDAR to study gully morphology and serve as a starting point for continuously monitoring of gully development processes taking place within the pool gully at very fine scales.