Pluvial flooding: hazard mapping and derivation of impact indicators

Abstract

Climate change is likely to cause a change in frequency and intensity of convective thunderstorms and associated heavy precipitation. Typical consequences of such events are a rapid generation of surface runoff with high flow velocities in hilly and mountainous areas as well as the unexpected and abrupt occurrence of inundation in areas currently not known as flood-prone. The mapping of such pluvial flash flood events is still a developing field especially with regard to the post-processing of raw hydrodynamic model output data. Moreover, challenges include the derivation of indicators needed for quantification and visualisation of the impact dynamics on elements at risk such as buildings and infrastructures. This is important to support the understanding of vulnerabilities including uncertainties as well as to ensure a targeted interpretation of possible consequences and planning of mitigation measures. We present a three-step approach which includes (i) the calculation of surface runoff dynamics with a 2D hydrodynamic model, (ii) the derivation of impact indicators based on the modelling results as well as (iii) the presentation and mapping of key indicators in innovative hazard maps and diagrams.