The river-scaling concept (RSC): a basis for ecological assessments

Abstract

The aim of this paper is to discuss the river-scaling concept (RSC) as a basis for ecological assessments. Since river morphology is a result of two major boundary conditions — transport of water and sediments — the size of project areas and the analysis procedure were found to be critical. Restricting the assessment of abiotic and biotic river components and its variability to a certain scale neglects the fact that ecological integrity depends on the process scale of boundary conditions. A newly developed two-step procedure for assessing the ecological integrity at various temporal and spatial scales is presented. During the so-called downscaling phase, abiotic and biotic components are analysed at the regional-continental (only for special questions), catchment-wide, sectional, local, and point scales. Catchment-wide analyses are based on digital elevation models (DEMs) and geographic information systems (GISs). Mass balance analysis, the application of fractals, and self-similarity studies for channel developments gain increasing importance. The application of linear and non-linear theories allows analytical tools to be derived to describe abiotic components like morphodynamics at sectional and local scales. Point scale investigations are based on deterministic models, where input data can be measured directly in nature. As the scale varies dramatically, the results obtained from various analysis tools are significantly different but interdependent. Biotic analysis are also performed at the same scales, so that the interrelations between morphodynamics and habitat quality can be derived at the end of this first phase. In a second phase an upscaling integrates and aggregates the results from the first step in order to yield overall conclusions on ecological integrity.