An Evaluation of the Spatial Configuration and Temporal Dynamics of Hydraulic River Habitats

The characterisation and assessment of hydromorphological conditions (physical habitat) is a key stage in the evaluation of the ecological status of streams and rivers required by the EU Water Framework Directive. In addition to identifying the presence or absence of habitat types, there is a need to reflect the quasi-discrete nature of hydraulic habitats and assess their spatial distribution (composition and configuration) and temporal dynamics across a range of discharges. However current approaches to physical habitat classification and assessment are limited in this respect. This research aims to develop a quantitative approach to assess spatio-temporal habitat dynamics. High resolution point measurements of depth and streamwise velocity were collected at four discharges in a 56m reach of the River Arrow (Warwickshire, UK). Fuzzy cluster analysis was used to delineate five hydraulic habitats and characterise the transitional zones between them. Spatial metrics, computed using FRAGSTATS, were used to quantify the composition and configuration of the habitat mosaic at each flow. Spatial metrics were compared using multivariate statistics to assess temporal habitat dynamics. Preliminary results indicate that intermediate flows support maximum diversity of habitat composition and configuration