Characteristics and Controls of Gravel‐bed Riffles: An Analyses of Data From the River‐habitat Survey

Abstract

This paper presents an analysis of data from the UK Environment Agency's River Habitat Survey database relating to bedform type and frequency. Emphasis is given to the gravel-bed riffle which (a) traditionally has been considered to be a fundamental morphological unit diagnostic of river stability, and (b) more recently has become an important design component in channel restoration and rehabilitation schemes. Data were sufficient to support the identification of distinct, catchment-scale controls determining the circumstances under which step-pools and riffles occur, and key local-scale influences upon riffle frequency and spacing. This demonstrates that the database can be used to support a broad geomorphological analysis. Suggestions are made for the interpretation of results obtained from the existing database, and for possible future modifications to enhance its geomorphological value.

Analysis of UK river restoration using broad‐scale data sets

“…Previous studies have examined riffle spacing (Emery et al . ), the influence of geology on river character (Harvey et al . 2008a), flow biotopes (Harvey et al .…”

Towards an ecologically meaningful classification of the flow biotope for river inventory, rehabilitation, design and appraisal purposes

“…Data from the RHS reference database have already been employed to investigate relationships between 'macroscale' variables (such as altitude, slope, distance to source and height of source) and reach-scale habitat features and channel morphologies (Jeffers, 1998;Emery et al, 2004). Additionally, RHS has been modified and applied in other continents to assess relationships between habitat characteristics across different sites (Mistry et al, 2004).…”

“…It does this by linearly transforming the original, correlated variables (p) into a new set of uncorrelated variables ('principal components'), which maximise the original variance (Dunteman, 1989). PCA has already been applied to RHS data in order to produce a broad river typology, which enables the prediction of major habitat features (Jeffers, 1998); in geomorphological applications to explore the characteristics and controls of gravel-bed riffles within England and Wales (Emery et al, 2004); and to characterise the habitat structure of different water bodies in South-West Guyana (Mistry et al, 2004). This form of data reduction allows the frequency matrix of flow biotope and functional habitat occurrence to be summarised and visualised on a single plot, with minimal loss of information.…”

Exploring the interactions between flood defence maintenance works and river habitats: the use of River Habitat Survey data

“…Nine habitat-related variables were extracted from the database in order to calculate five indices of in-stream habitat character and four indices of riparian habitat character (Environment Agency, 2003;Davenport et al, 2004;Emery et al, 2004). Table 1 lists the variables derived from the database and Table 2 describes the calculated indices.…”