Abstract
Multiple catchment controls contribute to the geomorphic functioning of river systems at the reach-level, yet only a limited number are usually considered by river scientists and managers. This study uses multiple morphometric, geological, climatic and anthropogenic catchment characteristics to produce a single national typology of catchment controls in England and Wales. Self-organising maps, a machine learning technique, are used to reduce the complexity of the GIS-derived characteristics to classify 4485 Water Framework Directive waterbodies into seven types. The waterbody typology is mapped across England and Wales, primarily reflecting an upland to lowland gradient in catchment controls and secondarily reflecting the heterogeneity of the catchment landscape. The seven waterbody types are evaluated using reach-level physical habitat indices (including measures of sediment size, flow, channel modification and diversity) extracted from River Habitat Survey data. Significant differences are found between each of the waterbody types for most habitat indices suggesting that the GIS-derived typology has functional application for reach-level habitats. This waterbody typology derived from catchment controls is a valuable tool for understanding catchment influences on physical habitats. It should prove useful for rapid assessment of catchment controls for river management, especially where regulatory compliance is based on reach-level monitoring.
Highlights
Geomorphic functioning of rivers is nested within a hierarchy of levels, each with progressively broader extents from subreach (103 m) [1]
Hierarchical clustering was applied to the self-organising maps (SOMs) output to identify typology classes
Seven clusters were selected based on the Davies–Bouldin index, a statistical measure of clustering quality, and because seven clusters sufficiently captured the complexity of catchment characteristics that influenced river functioning whilst remaining interpretable
Summary
Geomorphic functioning of rivers is nested within a hierarchy of levels, each with progressively broader extents from subreach (103 m) [1]. This paper develops a typology of catchment controls that influence river reaches, within subunits of catchments referred to as waterbodies. Has been adopted by river scientists and mangers. This has led to the widespread acceptance that knowledge of multidisciplinary, multiparameter controls that influence process must be incorporated within catchment management [6,7,8,9]. Multiple controls are not frequently fully integrated within management because gradients of anthropogenic land use are often superimposed onto the underlying properties of the natural landscape, making natural features of the catchment that influence river function more difficult to identify [10]. Multiple catchment controls are considered by some previous river typologies designed for river management, for example, using catchment controls such
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