Influences of Hardwood Riparian Vegetation on Stream Channel Geometry in Eastern Forested Environments

Abstract

Riparian vegetation has been recognized as a controlling factor of stream channel morphology, but specific influences on bed topography and planform geometry are yet to be fully clarified. This project explores the influence of riparian vegetation on channel geometry in alluvial streams of different sizes. Field data suggest that the presence of hardwood vegetation modulates channel width, bed topography and planform geometry in low-order streams. In larger channels, rootwads have less influence on planform curvature, but create patchy variations in bed topography that amplify relief of curvature-dominated bedforms. Stream table experiments illustrate that greater values of relief and thalweg forcing are generated by larger riparian obstructions. Experiments regarding the downstream spacing of trees also reveal that specific spacing frequencies can amplify or disrupt bedform creation, suggesting that resonance between alternate-bar dynamics and forest density may generate increased bedform variation.