Effects of Pore-Water Pressures and Riparian Vegetation on Bank-Material Strength and Streambank Stability

Principal Investigator: Dr. Andrew Simon

Problem:

Bank erosion by mass failure is a major contributor to suspended-sediment loads and an important means of channel adjustment in disturbed streams. Pore-water pressure and the mechanical and hydrologic effects of riparian vegetation play important roles controlling bank-material strength and streambank stability. The combined effects of pore-water pressure and riparian vegetation have not been properly accounted for in predictive models of bank stability and channel widening.

Objective:

Research is aimed at quantifying the beneficial and disadvantageous effects of both mechanical and hydrologic effects of vegetation on bank strength and stability. Results will be used to improve the Bank-Stability Model developed by Simon et al. (2000).

Description of Work:

Pore-water pressures are monitored with tensiometers, pressure transducers and a data logger in a composite, unstable streambank on Goodwin Creek. These data are supported with data on surface-water stage to quantify streamflow erosional forces. Root-reinforcement (mechanical) effects are to be tested for common riparian species using a tensile-strength tester in pits dug alongside trees. The hydrologic effects of various species are tested in instrumented soil monoliths having saplings that were planted in 2000.

Benefit:

Results will provide improved understanding of the effects of pore-water pressure and riparian vegetation on bank-material strength and stability. Results can then be incorporated into improved models of streambank stability.