The Use of Vegetation in Bioengineered Streambanks: Shear Stress Resistance of Vegetal Treatments

Installed and naturally colonizing vegetation performs a critical role in the long-term stability of bioengineered streambanks, especially when biodegradable erosion control fabrics are used for initial surface erosion protection. However, data on the limits of vegetal reinforcement are not well understood, particularly in regard to natural channels. Summaries from related studies on the shear stress resistance of grass-lined channels conducted in the last 50 years are presented. Although few studies consider sufficient factors necessary for direct application to current bioengineered streambank design, these data provide conservative guidelines to determine limits of vegetal streambank treatments. Vegetal resistance to shear depends on factors such as stem density, plant stem height, uniformity of plant cover, plant rooting habits, and soil erodability. Recommendations for future research include the need to obtain performance data on constructed bioengineered treatments and the associated vegetal resistance of native herbaceous and woody plant species commonly used in streambank bioengineering.