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1. This paper examines the influence of channel morphology and hydraulics on the occurrence and diversity of ‘functional habitats’ (also called ‘meso‐habitats’) in semi‐natural and physically degraded rivers. 2. The depths and velocities at which each functional habitat is most likely to be found are described using ‘occurrence matrices’. In most cases, each habitat was associated with distinct depth‐velocity conditions. 3. The relationship between habitat occurrence, diversity and river degradation was examined. The deviation of a site from its predicted natural summer wetted width was used as an index of physical degradation. Habitat diversity (measured as the Shannon index) was low for sites that were wider than expected for natural conditions. This was independent of the type of physical perturbation causing the width deviation. 4. Two main types of physical perturbation were identified in the degraded river: over‐widening and ponding. Over‐widened sites were shallow, slow and dominated by silt and emergent macrophyte habitats. Ponded sites were deep, slow and dominated by floating‐leaved macrophyte and macroalgal habitats. 5. River reaches of uniform depth had low habitat diversity compared with reaches containing both shallow and deep areas. 6. It is recommended that objective assessment of the type and extent of physical degradation, prior to restoration, should be made by measurement of depth, velocity, width and functional habitat distribution. Changes in channel morphology should then be designed to create the necessary range of depths and widths, and therefore velocities and habitat types, deemed desirable for that river site. Habitats that are over‐dominant or rare can be identified and the ‘occurrence matrices’ used to inform decisions about the change in physical conditions needed to enhance or suppress that habitat. 7. The approach is a cost‐effective way to link ecology with morphology and hydrology in river channel rehabilitation. Copyright © 1999 John Wiley & Sons, Ltd.

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River Habitat Survey (RHS) is a system which records and quantifies the physical and vegetational structure of river channels and their immediate floodplains. In the United Kingdom, where it has been applied since the 1990s, it has brought an understanding of state of rivers nationally and has proved to be a useful part of scientific investigation. It is now obvious that such a method should be applied more widely, especially in the European context, where river data is lacking for many countries and there is a need for a standard, internationally comparable method. In this paper an extension to the basic survey method is presented, with the aim of improving the detail and quality of data collected for highly dynamic, braided rivers, more common in the rest of Europe, particularly the south, than in the UK itself. The changes to the survey form included the recording of secondary flow and substrate types for each transect, in addition to the usual recording of primary types. Where more than one wetted channel was present data were collected for both the main and secondary channels. These were common in the areas studied, for instance in autumn 2000 secondary channels were found at 9 out of 11 sites in northern Italy and 4 out of 11 sites in the south. Additionally, the results showed that with the recording of both primary and secondary flow types for each transect the average number of flow types found per site was increased by between 1 - 2.2. For substrate types the average increase per site was close to 1. Certain flow types, in particular ‘chute’ and ‘no perceptible’, and substrate types, for example ‘sand’, tended to be under-represented by the basic survey method. The relevance and implications of these results are discussed with respect to the southern European situation and the point is made that the detail required from RHS depends on the original motivation for choosing to apply it. Where it is part of a detailed biological or ecological study the extra information provided by the extended form presented here is potentially useful

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The AQEM Project aims to develop a Europe-wide system for monitoring the ecological quality of rivers using macroinvertebrates, to