Robinson, Daniel R.; (2003) River rehabilitation in urban environments: Morphology and design principles for the pool-riffle sequence. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis addresses practical and conceptual issues associated with the design of riffle-pool bedforms in river rehabilitation schemes. Currently, rehabilitation approaches adopt a 'standard' model of planform and profile predominantly based on alluvial river systems of intermediate to high slope. However, the degree to which this model actually reflects the nature and range of form characteristics evident in natural alluvial channels is in question, as is the transferability of this model to contrasting river environments (particularly those with more utilitarian management requirements). Morphological investigation of a natural alluvial river channel exposes the deficiencies in current bedform identification techniques and highlights the diversity of longitudinal pool-riffle character at the reach and sub-reach scale. Morphological investigation of rehabilitated non-alluvial urban river channels shows that although much of this diversity is not originally replicated, it has to some extent developed over time as bed sediments have been extensively reworked. The pool-riffle bedforms which now exist in these rehabilitated urban channels also exhibit characteristics unlike those identified in the natural alluvial river. These characteristics are, however, similar to those identified in other urban river reaches where the bed has developed without restorative intervention. The reworked rehabilitated morphology therefore represents an 'intermediate' state, reflecting morphological characteristics associated with both natural alluvial as well as those specific to non-alluvial urban river systems. To reduce the extensive reworking of the current simplified natural alluvial river based templates, an integrated approach to urban river rehabilitation is proposed. This strategy reduces current template simplification by including variable form characteristics apparent at the reach and subreach scale in natural river systems, and improves their transferability to engineered urban river channels by incorporating morphological characteristics present in these reaches. An integrated approach would, in theory, be more stable and subject to less sediment reworking than current restorative approaches, and would also provide a more pronounced pool-riffle morphology than that which would develop naturally in non-alluvial urban river channels.

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