Clarification of the criteria used to identify near‐bed flow regimes

SUMMARY 1. Extensive measurements of near‐bed flow velocity were made over a reconstructed section of a cobble‐bed stream using a laser‐Doppler velocimeter. Based on these measurements descriptions of the near‐bed flow structure and flow conditions within benthic habitats are made. 2. The near‐bed flow classification system of Davis & Barmuta (1989) is discussed, and the threshold criteria of the system are shown to be incorrect. The correct criteria are stated and discussed in the context of two‐dimensional uniform bed roughness. 3. The improved classification system is used to classify the laboratory near‐bed flow regime, and this classification is compared to the flow types depicted in near‐bed flow structure diagrams. This comparison highlights the importance of accurately assessing stream‐bed roughness parameters to obtain accurate and useful near‐bed flow classifications. 4. The potential limnological applications of near‐bed flow regime classifications are discussed, with improved benthic invertebrate sampling procedures being given as the likely major benefit.