Benchmarking habitat quality: observations using River Habitat Survey on near-natural streams and rivers in northern and western Europe

1.Some ecological effects of physically modifying rivers are still unclear, partly due to scale factors, but also because the character of high quality habitat is poorly understood.2.Surveys at 278 sites on 141 near-natural streams and rivers in northern and western Europe were carried out between 1994 and 2009 to benchmark the habitat quality assessment system used for River Habitat Survey (RHS).3.The objectives were to establish if RHS was suitable outside the UK, investigate if 500 m was still valid as the survey length, suggest a benchmarking strategy and recommend improvements to habitat quality assessment protocols.4.Some modifications to RHS are needed to take account of differences in hydrological conditions, land-use and, most importantly, riparian habitat structure found in mainland Europe.5.On average, 82-87% of channel attributes and 87-98% of channel and bank features were recorded within the first of consecutive RHS sites, confirming that 500 m is an effective sample length for characterizing small rivers.6.Stream-flow character appeared to influence the distribution of several in-channel features, with greater diversity and between-site variation associated with rivers of mixed flow-types. To account for local variation and for effective use of survey time, it is recommended that two or more consecutive RHS sites are used for benchmarking purposes.7.A suite of assessment protocols with agreed criteria and analytical rules, linked to specific objectives (e.g. nature conservation, geomorphic condition), is needed to establish the character and habitat quality of rivers in a consistent fashion.8.A multi-discipline benchmarking programme using hydro-ecological regions in Europe would build on existing knowledge and help to improve both the inter-calibration and local application of quality assessment protocols. Data-sharing by hydrologists, river ecologists and fluvial geomorphologists would improve the basis for managing rivers in support of the European Water Framework Directive and Habitats Directive.