INTERACTION OF HYDRAULIC AND GEOTECHNICAL PROCESSES IN CONTROLLING BANK STABILITY
Watershed Physical Processes Research Unit
2009 Annual Report
1a.Objectives (from AD-416)
To improve our understanding of hydraulic and geotechnical processes operating at the bank toe of retreating streambanks and to use this understanding to develop more accurate numerical algorithms for predicting bank-toe erosion, bank stability and width adjustment in alluvial channels. This research will help to develop strategies for watershed management and to evaluate conservation effects where channel processes are important.
1b.Approach (from AD-416)
Conduct field and laboratory experimentation on fluvial entrainment of bank-toe materials which consists of: (A) improved evaluation of shear stress in the near-bank region; (B) improved evaluation of the critical shear stress of in situ and re-worked bank-toe materials; and (C) analysis of the excess shear-stress equation with archived and newly-acquired data to determine the variability and controls of its exponent.
Results of an investigation of the variability of geotechnical properties and their effect on predicting bank stability were further refined and published in a peer-reviewed journal on establishing a probabilistic framework for estimating the upstream-downstream extent of bank failures. The probabilistic framework, using Monte Carlo simulation has been incorporated in the Bank-Stability and Toe-Erosion Model. This provides improved estimates of loadings from bank erosion in channel evolution models by more appropriately quantifying the volume of sediment delivered to the channel by bank failures. Research findings are critical in modeling soil erosion from streambanks and bank-side gullies from these features. Bi-annual meetings were held with project principles and an academic training class in bank-stabilty modeling was held annually.