Research - River Condition Assessment
The River Condition Assessment tool was developed to contribute to Defra’s Biodiversity Net Gain methodology.
It uses the MoRPh field survey combined with a desk-based assessment of the geomorphic type of river to assess the current condition of a particular river reach.
Our research included the development and early testing of the RCA tool and subsequent additions to the tool such as the assessment of the hydrological connectivity of the river.
Most recently, we have been researching how the tool may be best applied in specific circumstances. To date we have focused on applying it to canals and navigable rivers, to developing outline river restoration designs as well as monitoring river responses, and to forecasting the likely impact of beaver reintroductions on river condition.
Key Publications #
Gurnell, A.M., Scott, S.J., England, J., Gurnell, D.J., Jeffries, R., Shuker, L., Wharton, G. 2020. Assessing river condition: A multiscale approach designed for operational application in the context of biodiversity net gain. River Research and Applications, 368): 1559-1578, https://doi.org/10.1002/rra.3673
Describes the original RCA method including the calculations used in all stages of generating the RCA outputs.
Gurnell, A.M., Downs, P.J. 2021. The legacy of river channel modification in wadeable, lowland rivers: exploring overdeep rivers in England. Earth Surface Processes and Landforms, 46, 3016–3025. https://doi.org/10.1002/rra.5268.
Describes the analysis used to establish interpretation of the RCAs River Shape index.
Cox, E.J., Gurnell, A.M., Bowes, M.J., Bruen, M., Hogan, S.C., O’Sullivan, J.J., Kelly-Quinn, M.A. 2022. multi-scale analysis and classification of the hydrogeomorphological characteristics of Irish headwater streams. Hydrobiologia, 850: 3391-3418. https://doi.org/10.1007/s10750-022-05013-5.
Explores the RCA River Type classification applied to mountain rivers.
Gurnell, A., Bennett, R., Craddock, S. and Chilton-Wilson, M., 2025. Assessing the Physical Habitat Condition of Navigable Canals and Rivers in England. River Research and Applications,42(1), 262-276. https://doi.org/10.1002/rra.70052
Explores the physical features of canals and navigable rivers as represented by the RCA and establishes the RCA Provisional Condition Score thresholds applied to these watercourses in the RCA.
Cox, E., Gurnell, A., Bowes, M., Bruen, M., Hogan, S., O'Sullivan, J. and Kelly-Quinn, M., 2025. Associating Local-Scale Physical Habitat Assemblages With Reach-Scale Stream Hydrogeomorphological Types in Mountain Headwater Catchments. River Research and Applications. Early view. https://doi.org/10.1002/rra.70080
Validates the expanded RCA River Type classification for mountain rivers (from Cox et al., 2023) and establishes the reach lengths over which these types persist within two small catchments within the Republic of Ireland.
Gurnell, A.M. and Gurnell, J. 2026. A preliminary assessment of the effects of beaver engineering on river condition and its relevance for Biodiversity Net Gain, Journal of Environmental Management, 401. https://doi.org/10.1016/j.jenvman.2026.128818
Establishes where and how the introduction of beavers may lead to an uplift in river condition as assessed by the RCA.