All urban drainage networks are designed to manage a maximum rainfall. This situation implies an accepted flood risk for any greater rainfall event. This risk is often underestimated as factors such as city growth and climate change are ignored. But even major structural changes cannot guarantee that urban drainage networks would cope with all future rain events. Thus, being able to forecast urban flooding in real time is one of the main issues of integrated flood risk management. Runoff and hydraulic models can be essential elements of flood forecast systems, as an active part of the system or as studying tools. This paper gives an overview of current available options for pluvial flood modelling in urban areas, from basic estimations with a one-dimensional urban drainage model to detailed flood process representation with one dimensional–two dimensional hydrodynamic coupled models. Each type of modelling solution is described with pros and cons regarding urban flood analysis. The paper then elaborates on real-time flood forecast systems and the influence of their main components. A classification of real-time urban flood systems is given based on the use of urban models, i.e. empirical scenarios, pre-simulated scenarios and real-time simulations. A review of existing operational systems is done using this classification.

Global flood management is a major issue for most cities which have to deal with worsening factors such as climate change and fast urban growth. Computer models have been used to model and understand urban flooding on a local scale in cities (25–50 km²). It has been practically impossible to model bigger cities in one go in sufficiently high resolution due to the heavy computations involved. The present paper describes a new modelling approach for urban flooding which allows modelling on large city scale (1000 km²) while keeping sufficient resolution, e.g. 5 m or 10 m grid. The multicell approach is applied for the city of Beijing for July 21st, 2012 flood event. Model results are compared to testimonials from the 2012 event. Comparison to traditional 2D urban flood computations shows that the multicell approach is much faster than standard detailed models while keeping a suitable level of precision.

Natural hazards, floods especially nowadays stand as the most frequent one posing huge damages to urban environment and urban communities. The need to reshape existing urban systems and make them able to accept a certain level of disturbance becomes important. Knowing that urban systems have dynamic characteristic and that the changes are visible on daily level regarding new technologies brings a different light to evaluation of flood vulnerability and flood resilience. New trends and more sophisticated assets are not designed to accept disturbance of natural hazards, at least not all of them. This puts evaluation of flood resilience and flood vulnerability as one of focal factors in process of reshaping build environment, reducing vulnerability, preparing urban communities to accept flooding and to create flood friendly environment. Introduction of a new concept to stakeholders stand as a challenge for flood professionals. A developed tool enables evaluation of flood resilience index for whole urban system. Beside the build environment, stakeholders need education and organization. Proposed presentation enables better communication with the key stakeholders. This paper focuses on analysis of urban systems in Europe and in Asia. The method is a research outcome obtained within projects CORFU and PEARL (www.corfu7.eu; http://www.pearl-fp7.eu/). The research focuses also on examination of present flood management strategies and their effectiveness in decreasing flood damage and evaluation of flood resilience

The modelling of extreme hydrological events often suffers from a lack of available data. Physically based models are the best available modelling option in such situations, as they can in principle provide answers about the behaviour of ungauged catchments provided that the geometry and the forcings are known with sufficient accuracy. The need for calibration is therefore limited. In some situations, calibration (seen as adjusting the model parameters so that they fit the calculation as closely to the measurements as possible) is impossible. This paper presents such a situation. The MIKE SHE physically based hydrological model is used to model a flash flood over a medium-sized catchment of the Mediterranean Alps (2820 km²). An examination of a number of modelling alternatives shows that the main factor of uncertainty in the model response is the model structure (what are the dominant processes). The second most important factor is the accuracy with which the catchment geometry is represented in the model. The model results exhibit very little sensitivity to the model parameters, and therefore calibration of these parameters is found to be useless.