River Habitat Quality Assessment (RHS)

Habitat Quality Assessment (HQA) offers an indication of habitat diversity based on natural features found within the river channel and surrounding corridor. Points are awarded for the presence of elements such as point, side, and mid-channel bars, eroding cliffs, large woody debris, waterfalls, backwaters, and floodplain wetlands. Additional points reflect the range of channel substrata, flow types, in-channel vegetation, the presence of bank-side trees, and the extent of natural land use near the river. These are combined to calculate an overall HQA score. Higher HQA scores reflect greater habitat diversity. The types and arrangement of features depend on both natural conditions and human activity within the channel and surrounding land. The River Habitat Survey (RHS) database supports comparisons between sites with similar physical settings, such as gradient or distance from the source, and shared geology. More details are available on the [River Habitat Survey website]. This dataset is part of the Approval for Access (AfA) product AfA434. The River Habitat Survey (RHS) is the Environment Agency’s standard method for collecting data on the physical structure and quality of river habitats across the UK. This dataset includes survey results from 1994 onwards and is a subset of the AfA286 River Habitat Survey. Approximately 19,000 surveys have been completed in England, with most carried out between 1994–1997 and 2006–2008. Surveys continue to be conducted for specific purposes, including assessing habitat availability or in response to the Water Framework Directive. The RHS manual, which details the survey methodology, is available to download from https://www.gov.uk. Surveys conducted before 2003 should not be directly compared with those carried out after that year, due to significant changes in methodology. River names in the dataset may appear in English, Welsh, or Gaelic. The dataset no longer includes data owned by Natural Resources Wales (NRW); users requiring information on rivers in Wales should contact NRW directly. Dimensional data are included to support interpretation of the survey results and should not be used for unrelated purposes. Certain information has been excluded from this dataset by the Environment Agency to ensure compliance with data protection regulations. However, if there is interest in specific sites or surveys, the following types of information may be available upon request: General description of the survey site Name of the surveyor Presence of structures such as weirs, sluices, culverts, outfalls, dams, abstractions, or hydroelectric installations Locations where channel flow is impeded by vegetation or debris Evidence of tipping, landfill, sewage, pollution, or gravel extraction Known data issues users should be aware of: In-stream Channel Vegetation HQA Sub-score: An error in historical calculations affected scores when vegetation was recorded as "present" or "extensive" in Spot-check 11 but not in Spot-checks 1–10 for the same category. This issue has been resolved for all surveys carried out after 12/07/2017. However, previously stored survey data have not been automatically updated. The impact on the HQA score is minimal—usually a difference of only a few points. 1994 Surveys – Submerged Vegetation Entries: For surveys conducted in 1994, submerged vegetation entries are excluded from the HQA score calculation. No fix is in place, and this omission may reduce scores by 1–2 points. HMS Culvert Score Error: A calculation error affects surveys where culverts are recorded in spot-checks and where bank material, bank modification, and channel substrate are not marked as ‘Not Known’ or ‘Not Visible’. In these cases, the database fails to add the expected 50 points per culverted spot-check. This issue can result in more significant discrepancies in scoring. No fix is currently in place.