Habitat indices for rivers: derivation and applications. (Special Issue: Recent developments in classification, assessment and management strategies for freshwater habitats in Britain and Europe.)

摘要

River Habitat Survey (RHS) is the standard riverine hydromorphology survey in the UK and modified versions have been adopted in several other European Countries. It aims to broadly characterize physical features over 500 m reaches, but in so doing records more than 100 variables, often making interpretation and data analysis challenging. In such instances, synoptic treatment of the data, creating simple indices such as Habitat Modification and Habitat Quality Assessment scores, can prove beneficial. The derivation of seven new indices is described, summarizing nearly half of the variables used by RHS and providing a quantitative overall summary of river reaches. Derived using an objective analysis of the RHS database (cf expert judgement), one index describes bedrock/boulder channels, two indices describe bank and riparian vegetation and a further two describe aspects of sediment transport and deposition. Two distinct types of modification - bank reinforcement and channel re-sectioning - are also quantified. Rigorous testing indicates that the indices are reliable across the complete range of conditions and countries in the UK. The new indices are readily interpreted and while providing a simple overview of a river reach, they are objective and quantitative, lending themselves to a range of management and research applications. They have already been used successfully in quantifying riverine bird habitats and this, along with other applications, is discussed.