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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #177560
Title: EFFECT OF WOODY VEGETATION ON CRITICAL CONDITIONS FOR STREAMBANK STABILIZATION USING A DETERMINISTIC BANK-STABILITY MODEL

Author
item Simon, Andrew
item Bankhead, Natasha
item Langendoen, Eddy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2005
Publication Date: 9/1/2005
Citation: Simon, A., Pollen, N.L., Langendoen, E.J. 2005. Effect of woody vegetation on critical conditions for streambank stabilization using a deterministic bank-stability model. In: Proceedings of the Sixth International Conference on Geomorphology, September 7-11, 2005, Zaragoza, Spain. p. 326.

Interpretive Summary: Interpretative summary not required - abstract only.

Technical Abstract: The use of riparian buffers has become an increasingly popular means of improving habitat and streambank stability in stream restoration schemes. Research at the National Sedimentation Laboratory on the mechanical and hydrologic effects of riparian vegetation on streambank stability, combined with the development of a deterministic bank-stability model (Simon et al., 1999) has been used to evaluate the controlling forces and processes for quantifying bank stability. Measurements of root distributions and the tensile strength of roots for a range of common riparian species have permitted quantification of the magnitude of increases in shearing resistance due to root reinforcement. Root numbers and area for woody species decrease non-linearly with depth and are virtually absent below 1 m. For young woody species (2-7 years-old), average increases in cohesion due to root reinforcement and averaged over 1 m ranges from 1 to 8 kPa with species such as Eastern sycamore (Plantanus occidentalis) and River birch (Betula nigra) providing the greatest benefits. These are significant values given the moderate cohesive strengths of common alluvial materials. Herbaceous species such as Alamo switch grass (Panicum vircatum 'Alamo') can have rooting depths up to 3 m and contain enough fine roots to provide up to 20 kPa of additional cohesion. Using the Bank-Stability Model, analyses were conducted for streambanks of varying heights, angles and composition under a range of surface-water heights and pore-water pressure scenarios. Results, expressed in terms of the factor of safety (Fs) were used to develop nomographs of critical bank conditions (height and angle) with and without vegetation to (1) evaluate the additional stability provided by root reinforcement of different species, and (2) to calculate the additional height and steepness that could be withstood to maintain stability. Established vegetation can be equivalent to reducing the bank angle by mechanical means by up to 30o.