Two‐dimensional (2D) hydraulic models are widely used as tools for flood hazard mapping and also to support flood risk management. Yet, only few models are capable of using high‐resolution terrain data (raster‐based Digital Terrain Model with 1 m spatial resolution) on a large scale (hundreds of square kilometres and more). Central to the model approach presented in this article is the raster‐based 2D model High Performance Computing version of FloodArea (FloodAreaHPC), which allows for multicore processing, thus being able to model large areas without having to make compromises regarding spatial details. The model has been applied for inundation modelling of rivers, dike breaks, and heavy rainfall runoff (pluvial flooding). For the latter case, the model is coupled with a hydrologic preprocessor data base which provides spatially and temporally variable runoff coefficients based on land use, soil, and slope. The case study presented in this study has an area of 144 km2 and is located close to Dortmund in Western Germany. The modelling results of two heavy rainfall scenarios, presented in analogue and digital flood hazard maps, were used in a Public Relations (PR) campaign to inform the public about pluvial flood risk and possible mitigation measures.

Abstract. The awareness of pluvial (rain-related) flood risk has grown significantly in the past few years but pluvial flooding is not handled with the same intensity throughout Europe. A variety of methods and modelling technologies are used to assess pluvial flood hazard and risk and to develop suggestions for flood mitigation measures. A brief overview of current model approaches is followed by the description of a modelling methodology that has been developed throughout the last 15 years with the focus on processing large scale areas. Experiences from several projects show that only high quality models of whole catchment areas yield results with enough accuracy to gain credibility among stakeholders, planners and the public. As a best practice example shows, the model approach also helps to plan effective decentral flood protection measures. To ensure successful flood risk management, a long-term preservation of flood risk awareness among local authorities and the public is necessary.

No abstract

Abstract. Dike failure events pose severe flood crisis situations on areas in the hinterland of dikes. In recent decades the importance of being prepared for dike breaches has been increasingly recognized. However, the pre-assessment of inundation resulting from dike breaches is possible only based on scenarios, which might not reflect the situation of a real event. This paper presents a setup and workflow that allows to model dike breachinduced inundation operationally, i.e. when an event is imminent or occurring. A comprehensive system setup of an operational modelling unit has been developed and implemented in the frame of a federal project in Saxony-Anhalt, Germany. The modelling unit setup comprises a powerful methodology of flood modelling and elaborated operational guidelines for crisis situations. Nevertheless, it is of fundamental importance that the modelling unit is instated prior to flood events as a permanent system. Moreover the unit needs to be fully integrated in flood crisis management. If these crucial requirements are met, a modelling unit is capable of fundamentally supporting flood management with operational prognoses of adequate quality even in the limited timeframe of crisis situations.