Channel Restoration Design for Meandering Rivers

摘要

A framework for channel restoration design is presented that attempts to bridge the divide between reconnaissance level geomorphological designs at one extreme and numerical modeling of hydrodynamics, sediment transport and morphological change at the other. Reestablishing equilibrium between the sediment supply and available transport capacity in the restored reach is the primary objective of the design framework. A geomorphic engineering approach is presented, which recognizes that the river is ultimately the best restorer of its natural morphology and should be allowed to participate in its own recovery. This is accomplished through designing an approximate channel mould, based on the broad dimensions of the river, and then allowing the river itself to develop the intricate cross-sectional detail and intra-reach morphological features to complete the recovery process. Geomorphic engineering provides a practical solution by striking a balance between empirical-statistical and analytical (process-based) methods. The range of techniques that comprise the design approach facilitate a realistic solution to the indeterminacy problem and confidence bands applied to typed' morphological equations provide a mechanism through which natural rivers can be used as realistic analogues for channel restoration design. By accounting for natural systems variability, the design framework is an appropriate platform for generating restoration design solutions that mimic the natural channel morphologies and environmental attributes in undisturbed systems, while meeting multifunctional goals of channel stability and low maintenance commitments. Rather than constructing physical habitats that constitute form without function, geomorphologically, the types and levels of physical habitat diversity that are sustainable in the restored reach are defined by the type of river, the nature of the sediment and flow regimes and the catchment context.