Bank stability analysis for regime models of vegetated gravel bed rivers

Abstract

AbstractA new bank stability analysis procedure is developed for use in rational regime models predicting reach average channel dimensions. The performance of a regime model using this new bank stability formulation is compared against that for a model using the modified friction angle approach proposed by Millar and Quick (1993). The bank stability assessment is based on a conceptual model that more closely represents conditions found in gravel bed rivers with vegetated floodplains: the primary effect of vegetation is its contribution to a stable upper bank, the position of which is determined by erosion of unvegetated bed material at the toe of the bank. The vertical height of the upper bank is estimated using a simple slab failure model and assigning an effective cohesion to the vegetation‐reinforced soil. The geometry of the lower slope and the width of the channel are determined iteratively using the regime approach described by Eaton et al. (2004). A comparison of the predicted stream channel widths for stable gravel bed channels classified according to riparian vegetation type (Hey and Thorne, 1986) showed that this new formulation increases model accuracy, especially for the more densely vegetated channel types. Since the strength parameters used in the model can be estimated from the observed bank geometry, the potential for applying and testing rational regime models in the field has been significantly improved. Copyright © 2006 John Wiley & Sons, Ltd.