Riparian woody vegetation and riverbanks: An exploration of riparian tree reflection and control of fluvial processes along South River, VA

This dissertation examines the complex interactions between trees and eroding river banks at South River, Virginia, in a series of 3 separate articles and a literature review. The first article assesses riparian tree geometry along a bank stability gradient and reveals that trees reflect bank morphology in both their root-plate undercut and deflection angle (i.e., lean). Exposed tree root analysis, the focus of the literature review and second article, is a biometric technique for the quantification of land surface denudation using exposed root indicators that reflect the timing of exhumation. Erosion estimates from 24 study reaches using the exposed roots of 79 deciduous trees are obtained and compared to those estimated with photogrammetric techniques, a common approach for estimating bank erosion rates. The results of this comparison indicate that exposed root analysis produces erosion rates with equal or greater accuracy than photogrammetric techniques. The ability of riparian trees to control, in addition to reflect, fluvial processes is the focus of the final section. Riparian tree armor, a previously unrecognized controlling mechanism of bank stability, occurs when woody plant tissue protects the bank by acting as a barrier against erosive forces and exerts a relatively small (12%) but significant influence on bank erosion rates. The work presented in this dissertation is novel and the results further the field of fluvial geomorphology, providing valuable information regarding the use of reforestation as a bank stabilization strategy.