Large rivers have been selected as one of the satellite topics both within WP3 and WP4, because of their particular features which could not be analysed in the case study catchments framework. Large rivers are considered rivers with a catchment larger than 10,000 km2 and > 100 m3/s. This encompasses rivers such as the Danube, Rhine, Rhône, Ebro, Vistula but also major tributaries such as the Sava, Narew, and Main rivers. Most fulfil major socio-economic functions, which will remain strongly modified and thus direct the options for rehabilitation. Because of their multifunctional use, large rivers can often only be partially rehabilitated or mitigated to achieve Good Ecological Potential according to the Water Framework Directive. This report addresses both hydrological modifications and restoration (rehabilitation, mitigation) following a DPSIR approach for six case studies that are spread across Europe
An increasing number of rivers have been restored over the past few decades but only a small number of these projects have been monitored, and hence, the knowledge on the effect of river restoration on biota is limited. Nevertheless, monitoring results of several projects are available in peer-reviewed scientific literature and have been compiled in recent research projects. The objective was to evaluate the effect of hydromorphological restoration on biota based on these existing data. Specific objectives were to quantify restoration success, to identify catchment, river reach, and project characteristics which influence (either constrain or enhance) the effect of restoration, and to derive recommendations for river management. The study is complemented by a satellite topic on urban river restoration.