Bank Stability Algorithm for Numerical Modeling of Channel Width Adjustment

摘要

Existing numerical models of river channel morphology are seriously limited intheir application by their inability to account for bank erosion and changing channel width. Recent research has, however, now led to the development of a physically-based numerical model of river channel widening, in which changing channel width is accounted for by coupling fluvial bank erosion and mass-wasting algorithms with flow and sediment transport models (Darby, 1994; Darby and Thorne, In Review). Verification studies indicate that this new model is capable of predicting channel adjustments well, qualitatively, but widening rates are seriously underpredicted by the new model (Darby et al., In Review). This deficiency has focused attention on the predictive ability of versions of the Osman and Thome (1988) mass-wasting algorithm further developed by Darby (1994) and currently employed in the Darby-Thorne numerical model. In particular, the Osman-Thome-Darby analysis constrains the failure plane to pass through the toe of the bank, excluding the possibility of simulating secondary, upper bank failures. The Osman-Thorne-Darby analysis also excludes pore water pressure and hydrostatic confining pressure effects. These deficiencies have been addressed conceptually by Simon et al. (1991), but this approach was developed only for banks of simple geometry, and does not account for the effects of pore and confining pressures on the development of the incipient failure plane. In contrast, the Osman-Thorne-Darby analysis utilizes a more complete, physically-based approach in predicting failure plane angle, and the approach is also based on a bank profile characteristic of natural eroding riverbanks. (KAR) P. 2.