Looking beyond the shores of the United Kingdom: addenda for the application of River Habitat Survey in Southern European rivers

摘要

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.