A cost-effective approach for linking habitats, flow types and species requirements

This paper explains the background to concepts of instream physical habitat incorporated in River Habitat Surveys. Two independent research threads—physical biotopes and functional habitats—are described representing, respectively, ‘top down’ and ‘bottom up’ attempts to describe the use of instream physical environment by biota. 2. Physical biotopes are observed in the field by identification of surface flow types, each of which has been proved as distinctive by hydraulic study; these have been incorporated in River Habitat Surveys. Functional habitats have been derived from invertebrate sampling and statistical analysis. 3. Reconciling the two approaches is now an urgent research requirement so that RHS databases can be used predictively and the quality of habitat evaluated as the basis of rehabilitation and restoration. 4. The current practical uses of the two approaches are described.