Climate change impacts on flood hazard using ensemble modelling approach

Assessing flood hazard in climate changes depends critically on the scenarios and projections of climate change used. The evolution of the scenarios has been followed throughout a case study of the Aarhus river catchment. The aim is to evaluate both atmospheric and hydrological variable changes in the upstream catchment and to combine it with an investigation on the impacts on flooding in the downstream part, while taking sea level rise into consideration. All of the analyses are carried out using ensembles of projections produced by Global Climate Models (GCM) for scenarios A1B, A2 and B1 in projection horizons 2050 and 2100 and Regional Climate Models (RCM) for scenario A1B in 2100. The case study results establish a clear relationship between climate changes and increased flood hazard. There is a considerable agreement among the projections that with climate changes heavy precipitation events will be more intense and will appear more often. For obtaining discharge results, an integrated catchment modelling is being used, which also allowed us to study the climate change impacts on recharge to the groundwater table. The flood frequency analysis shows a trend towards increasing the intensity of the flooding events in the future. The combined flooding effects from climate changes and sea level rise are presented spatially in flood hazard maps that show a significant escalation of the flood hazard with sea level rise