Development of a Probabilistic Multi-flood Hazard Approach Considering Uncertainties and Climate Change—Application to the Coastal Flooding of the Havre (France)

Many coastal areas need to be protected from both rain and coastal flooding as their proximity to the sea is a necessity. In the framework of the development of a Probabilistic Flood Hazard Assessment (PFHA) approach, several flood phenomena should be considered to estimate the joint contribution of each of them. Coastal floods are mainly generated by storms that raise the sea level over the tide. In addition, coastal floods may be more severe when a marine submersion is combined with fluvial or pluvial floods. In addition, global warming has a direct effect on flood phenomena. It can induce a strong rise in sea level and a marked evolution of the characteristics of storms and more extreme coastal floods will occur more frequently. The combination of the flooding phenomena and their dependence is also likely to change as a result of climate change. This work aims to develop a new probabilistic approach taking into account the outcome of the combined action of several flood phenomena. The epistemic and random uncertainties, as well as the impact of climate change, are also considered and integrated through the theory of belief functions. The proposed PFHA approach is applied to the city of Le Havre, a French city located on the Channel coast which is likely to be flooded by rain and sea level.