Floods, which are among the most dangerous and frequent disasters in the world, are expected to occur more frequently due to climate change. Floods, and flash floods in particular, generate economic, environmental, and social effects. Economic effects include damage to infrastructure, the negative influence upon transportation and communications networks, and an increase in fuel costs, as well as time loss due to traffic delays (congestion) and the necessity of taking alternative routes. It is therefore important to take action both to prevent and to mitigate these effects. In the 21st century there has been a radical change in the approach to the issue of flood protection (as seen in the approach formulated within the 2007 European Floods Directive)—it is no longer believed that there is such a thing as complete protection against floods, but that the damage and loss it inflicts can only be mitigated, and since floods cannot be completely eradicated, societies must learn how to live with them. In the event of a flood, preprepared procedures to counteract and mitigate the effects of the disaster are followed, including the evacuation of people and movable property from affected areas.
Evacuation planning is meant to reduce the number of disaster-related (including flood) fatalities and material losses. Crucially, this type of planning requires a well-defined, optimum evacuation policy for people and households within flood hazard areas. In addition, evacuation modelling is particularly important for authorities, planners, and other experts managing the process of evacuation, as it allows for more effective relocation of evacuees to safety. Modelling can also facilitate the identification of bottlenecks within the transportation system prior to the occurrence of a disaster; that is, it enables us to determine the impact of flood-related road closures, and to comprehend—among other things—the effects a phased evacuation has on traffic load. Furthermore, not only may the ability to model alternative evacuation scenarios lead us to establish appropriate policies, evacuation strategies, and contingency plans, but it might also facilitate better communication and information flow.
Evacuation from flood-hazard areas is a major challenge for the field of flood risk management as well as the fields of traffic engineering and transport planning. This is particularly true when the research has to include not only those journeys directly related to escape from hazardous places, but also their reflexive relationship with the total number of journeys made in the “background” of the evacuation itself.