The hydraulic description of vegetated river channels: the weaknesses of existing formulations and emerging alternatives

Currently, many of the methods used to predict the effect of vegetation on river flow suffer from one or both of the following problems: (1) a strong dependence on parameters that have a poor physical basis and which are only readily determined using empirical means; and (2) a poor conceptual basis, in terms of the way they represent the effects of vegetation on the flow, especially in higher dimensionality numerical models. This limits their contribution to problems that extend beyond basic hydraulic prediction (e.g., of water levels) to ecosystem understanding. In this study, we show how use of coupled biomechanical-hydraulic models may lead to a much-improved representation of a range of open-channel flow processes. Preliminary experiments over hypothetical vegetation canopies are producing very encouraging results and may provide the means for an improved representation of vegetation in higher dimensionality numerical models that may result in a better justification and more reliable identification of the conveyance parameters needed for both flood identification and the characterization of habitat. (C) 2014 Wiley Periodicals, Inc.