Channel changes and invertebrate faunas below Nant-Y-Môch Dam, River Rheidol, Wales, UK: 35 years on

Greenwood, M.T., Gurnell, Angela M., Bickerton, Melanie A. and Petts, Geoffrey E. (1999) Channel changes and invertebrate faunas below Nant-Y-Môch Dam, River Rheidol, Wales, UK: 35 years on. Regulated Rivers: Research & Management, 15 (1-3). pp. 99-112. ISSN 0886-9375

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River regulation initiates a succession of changes within lotic ecosystems driven by the adjustment of channel form to the imposed flow and sediment transport regimes. One typical sequence of channel changes involves channel adjustment to reduced flows. This temporal succession of channel changes is also found as a spatial sequence of channel forms, in different stages of adjustment during the relaxation period. This paper describes channel changes within a short reach of the River Rheidol, Wales, which was regulated in 1961. The ecological implications of channel change are assessed by examination of the benthic macroinvertebrate communities. Survey data from 1996 are compared with data from the early 1980s. A model of ecological change is presented comprising two main stages: (i) an accommodation phase, during which flows are accommodated within the pre-existing channel form and (ii) an adjusting phase, the period of channel change. Thirty-five years after dam closure, most of the River Rheidol is experiencing an accommodation response and changes of the macroinvertebrate community are related to stable flows and local siltation in the pre-regulation channel. Channel change is limited to a 200 m reach below a tributary confluence, i.e. below a sediment source. In terms of the number of taxa, more were found in the regulated river than in unregulated sites and the greatest number occurred in the short reach that was in a late stage of channel change.

Item Type: Article
Subjects: University of Westminster > Science and Technology > Life Sciences, School of (No longer in use)
Depositing User: Miss Nina Watts
Date Deposited: 12 Feb 2009 10:02
Last Modified: 22 Dec 2009 09:53

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