Review Article Integrated catchment assessment of riverine landscape dynamics Peter Molnar*, Paolo Burlando and Wolfgang Ruf Institute of Hydromechanics and Water Resources Management, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland Received: 4 February 2002; revised manuscript accepted: 22 March 2002 Abstract. The traditional approach to study riverine environments focuses on the river reach scale, with streamflow as a steady state driving force. Here, the ac- cent is on the dynamic nature of streamflow. Impacts of the hydrological regime, of floods and streamflow vari- ability, on riverine landscapes are reviewed. To evaluate such impacts, it is necessary to focus on the entire catch- ment in an integrated fashion, so that local changes in river morphology and river habitat can be evaluated in context with upstream catchment processes. A framework for an integrated physically-based catchment modelling system, based on models of hydrology, hydrodynamics, sedimentology and ecology, is presented. The hydrologi- Aquat. Sci. 64 (2002) 129 – 140 1015-1621/02/020129-12 © EAWAG, Dübendorf, 2002 Aquatic Sciences cal element addresses runoff response in a catchment on a continuous basis in time and distributed in space, while the hydrodynamic, sedimentological and ecological ele- ments address the interactions and feedbacks between water, sediment and the ecosystems at the scale of the river corridor. The models are arranged in a nested fashion, with long-term quantification of catchment and river system dynamics as the main objective. A long-term vision of catchment processes is important for the evaluation of potential anthropogenic influences and climate change effects, as well as for the evaluation of river conservation projects. Key words. Hydrological regime; floods; catchment analysis; modelling; riverine landscape. Introduction Streamflow plays a central role in shaping the physical and biological environments of riverine landscapes. Lo- cal disturbances, for instance by flood-induced erosion, redistribution of sediment or accumulation of debris, may lead to severe habitat changes. It is also recognised that periods with low flow or, more generally, streamflow variability are crucial for habitat recovery (e.g., Minshal, 1988; Resh et al., 1988; Poff and Ward, 1989; Poff, 1996). All of these elements constitute the natural hydrological regime as a determining factor for riverine ecosystems (Poff et al., 1997). One of the fundamental challenges in hydrology and ecology is the evaluation of the soil-vegetation-climate interactions and feedbacks as they pertain to ecosystems, at different spatial scales. The natural hydrological regime is a product of such complex interactions on a catchment scale. The onset of changes in the physical en- vironment of rivers is often dictated by these interactions. As a result, local changes in river morphology as well as river habitat are connected with large-scale catchment features such as climate, geology, topography, and catch- ment response in general. This continuity is especially crucial for assessing long-term catchment and ecosystem dynamics, and for investigating the role of heterogeneity * Corresponding author address: ETH Hönggerberg, CH-8093 Zürich, Switzerland; phone: +41-1-6332958; fax: +41-1-6331061; e-mail: molnar@ihw.baug.ethz.ch Published on Web: June 19, 2002