In the current scientific discussion high loads of fine sediments are considered one of the most important causes of river ecosystem degradation worldwide (e.g. US EPA, 2007; Zhao et al., 2011). Especially in intensively used catchment areas changes in the sediment household must be regarded as a factor that prevents the achievement of the objectives of the European Water Framework Directive (WFD). Therefore, two comprehensive studies were carried out in Upper Austria to get a wider understanding of the causes of siltation, the current status, the effects and possible improvement measures.