HouSui - Flood Control Measures Model Study Bründlbach (Graz) Strategies for an Integral Urban Drainage Management

In recent years, floodings in urban areas due to intensive stormwater events occurred more often and caused damages in industrial and residential areas, as well as on public goods. The aim of the project HouSui is to highlight possible causes and approaches for floodings in urban areas. On the one hand, the chief causes for floodings in urban areas are the systematic exploitation of rural infiltration grounds and on the other hand, the increasing surface sealing during the last decades within urban areas. In connection with climatic changes there is an accumulation of floodings in urban areas estimated. This raises, however, more and more the question for the right handling of these issues for municipal drainage management utilities, both for rural and urban areas. The enquiry, assessment and minimisation of flood risks in urban areas is a com-bined assignment for drainage management utilities on the county level as well as the municipal level. Furthermore, the municipal drainage management utilities have to align their assignments with other municipal infrastructure departments, such as the department of land use planning and urban development, wastewater discharge and road maintenance. The assignment of urban flood risk management has to be seen as a cross-linked one from all the departments involved. A cross-linked consideration offers the possi-bility to tie single measures (e.g. the on the spot infiltration of not contaminated rain-water according to the Austrian ÖWAV Regelblatt 35) in a way, which allows dis-covering and using synergetic effects. Detention, infiltration and the proper discharge of surface water in case of intensive stormwater events in rural and urban catchment basins are the main aims of water management in urban areas. The project HouSui wants to carve out strategies for an integral urban drainage management. The interactions between the surface run-off and the run-off in the sewer system are quite complex, thats why HouSui attempts linking 2D-surface model with a hydrodynamic sewer model. Single measures as well as synergetic packages of measures cannot only be mapped but also analysed concerning e.g. their impacts on the catchment basin and sensitivity. The aim of the modelling is to highlight the flow paths of rainwater in case of intensive stormwater events on surface and in the sewer system. There are various aspects that have to be considered for the assessment of meas-ures, such as regulatory framework (e.g. the Directive 2000/60/EC establishing a framework for Community action in the field of water policy, the Directive 2007/60/EC on the assessment and management of flood risks, the RIWA-T), technical guidelines (e.g. the EN 752, the ÖWAV Regelblatt 35, the ÖWAV Regelblatt 11), economical, ecological and sociological requirements. The main achievement of the project HouSui, where various packages of measures are pointed out, will be a compendium with recommended procedures entitled strategies for an integral urban drainage management valuable for all departments involved in the construction, duty and maintenance of any kind of urban infrastructure.