The extreme increase in flood events and flood damage during recent decades makes it obvious that an integrated approach is crucial to flood protection. Many issues, such as technical measures, aerial and spatial management, retrofitting, raising risk awareness etc., have to be incorporated into the complex field of Integrated Flood Management (IFM). The designed EC framework directive for flood risk management underlines the necessity for this comprehensive approach. As far as spatial management is concerned, aspects of water and flood management are often either insufficiently or belatedly included in the planning process. Another problem is that flood and planning issues are not regarded and dealt with on the level of river basins but are subject to administrative boundaries. At the same time, aspects of geodata infrastructure and flood related data and information have to be considered as a crucial interface in a concept for integrated planning. In the context of an EU Interreg IIIb project named FLOWS (www.flows.nu), an interdisciplinary group of the University of Lüneburg, the Technical University of Hamburg-Harburg and the City of Hamburg developed a planning instrument which integrates water management and flood aspects in spatial and city planning on the scale of a river basin, with the aim of reducing flood impacts and at the same time improving the ecological situation. The interfacial requirements on technical and computer-based tools such as Decision Support Systems (DSS) were also considered. The very urban area of the City of Hamburg and rural parts of Lower Saxony in Germany served as project areas. In this scheme, a thorough process and structure analysis was accomplished to investigate data and planning structures, planning processes and cooperation between water management and spatial planning and planning deficits. By means of interviews and workshops with practitioners the planning instrument and the DSS were developed in order to improve implementation on an operational level for working out mid- and long term planning strategies.