Inhaltsangabe:Introduction: The main goal of this thesis is to develop a framework for a Web based Spatial Decision Support System (WSDSS) for supporting the development of river restoration strategies. Due to their free availability, open source/free GIS tools and technology are used to develop this decision support framework supporting a multi-user decision support platform via the web. The integration of latest multi-scale river ecological knowledge is assured by the strong relatedness of this thesis to a project that has been run at the University of Natural Resources and Applied Life Sciences (BOKU) in Vienna between 2005 and 2008 the MIRR project (Model based Instrument for River Restoration). By order of the Austrian Ministry of Life, being responsible for the implementation of the EU-Water Framework Directive, a strategic instrument to identify hydro-morphological restoration measures for running waters to enhance the ecological status of rivers in Austria measured by fish was developed at the Institute of Hydrobiology and Aquatic Ecosystem Management (IHG) at the BOKU based on comprehensive multivariate analyses of fish/pressure relationships using data from Lower Austria. The identification and quantification of the effects of the main relevant pressure types allowed the development of flow charts for guiding restoration activities at multiple scales. Up to now no tool exists allowing an automated evaluation of the effects of different restoration strategies on the ecological status of the so called water bodies, the relevant scale for action and reporting with regard to the EU-WFD. Furthermore existing web based GIS tools related to rivers and the implementation of the EU WFD in Austria and on an EU level do not allow any interaction with the data, and are therefore not well suited for decision support (for example the Water Information system of Austria WISA , or the Water Information System of Europe WISE ). The following parts of the MIRR project conducted under the supervision of the author of this thesis as work package leader, and can be seen as part of this thesis, although mainly content relevant for the development of the WSDSS framework is reproduced here: Literature research and definition of relevant parameters to model fish/pressure relationships on multiple spatial and temporal scales, Investigation and collection of the available GIS datasets in Austria, that might be of relevance for the MIRR project, and matching [...]