  Le Havre agglomeration (CODAH) includes 16 establishments classified Seveso
with high threshold. In the literature, we construct vulnerability maps to help
decision makers assess the risk. Such approaches remain static and do take into
account the population displacement in the estimation of the vulnerability. We
propose a decision making tool based on a dynamic vulnerability map to evaluate
the difficulty of evacuation in the different sectors of CODAH. We use a
Geographic Information system (GIS) to visualize the map which evolves with the
road traffic state through a detection of communities in large graphs
algorithm.
