The contribution of sketch maps combined with numerical simulation in the understanding of coastal flood risk (Mediterranean coast, France)

International audienceCoastal flooding hazards are generally mapped based on historical information and numerical model simulations that reproduce the physics of the processes at the land-sea interface and the flows on land. Our work aims to supplement coastal flooding hazard mapping by combining the results of a numerical simulation with sketch maps of coastal flooding risk created in response to a questionnaire-based survey carried out in Leucate on the French Mediterranean coast. The numerical simulation took into consideration the areas that were flooded in recent storms and considered the flooding risk in case of a 100-year event. Three types of sketch mapping were produced by respondants, covering historical coastal flooding, flood hazard areas, and no-flood hazard areas. From the 493 surveyed people, 55% draw at least one sketch map, with a total of 676 sketch maps collected. Our results show good consistency between the observations, the models and the sketch maps, confirming the value and the complementary nature of the methods. Respondents fairly easily associate coastal flooding risk with the coastal fringe, by integrating historical overtop flood events that can cause breaches in seafront defences, but do not take into account potential overflowing on the lagoon side. The sketch maps were also analysed by considering district of residence. As expected, the results highlight that the people living in the most exposed areas have a better understanding of the hazard than those who are less exposed or who do not live in these areas