A method for the automated extraction of environmental variables to help the classification of rivers in Britain

Abstract

1. A number of systems for assessing river quality or for classifying rivers use data obtained from maps as a means of linking a given stretch of river with a reference site. The embodiment of the reference-state principle within the EC Water Framework Directive means that this trend will accelerate. 2. Historically, data such as the distance to source of river, altitude at source, altitude at site, and local slope have been derived from maps by hand, a process which is time consuming and prone to both random and systematic errors. 3. An automated computer-based extraction procedure has been developed on a GIS system to improve the speed and repeatability of such data collection. This paper describes the processes required to produce reliable data, to ensure quality control and to obtain optimal speed of data extraction. 4. The system has several applications including determination of catchment areas for the EC Water Framework Directive and delineation of reaches to support the development of physical quality objectives for rivers in England and Wales. Copyright © 2002 John Wiley & Sons, Ltd.