Introduction Chemical accidents triggered by natural hazards (known as Natechs) are relatively rare. Nonetheless, several studies indicate that the frequency of Natech accidents is increasing. Moreover, the industrial sector is often unprepared for these joint natural and technological or Natech events mainly because of the lack of guidelines on how to apply Natech regulations and the lack of information on the dynamics of Natechs. This article describes research works to improve the understanding of the physical and organizational vulnerability of industrial facilities exposed to natural hazards (particularly tsunamis and floods). Method The work is based on a posteriori (in Japan and France) and a priori analysis of the industrial as well as the local governments’ emergency management to the Natech accidents during the Great East Japan earthquake and tsunami (GEJET) and during severe flooding events in France. Survey questionnaires in Japan and France are applied to chemical facilities, to government agencies, and to citizens in France and Japan. Secondly, all of these data have been used to construct various models (systemic model, functional representation, and risk models) at the scale of the industrial site territory. These models help to represent the impact of the flood events on the facilities and more precisely on the equipment directly or indirectly involved in the development and management of a technological accident (using fault trees). Results The interviews, field visits and mail survey to affected facilities have provided detailed information about losses and damage, chemical accidents and oil spills triggered by the earthquake and tsunami, the vulnerability of the facilities, the performance of safety and mitigation measures, the accident consequences, and the overall emergency response actions. 6 equipment families or subsystems directly or indirectly involved in a Natech accident have been identified. An analysis (using systemic and functionnal models) of each 6 sub-systems of the industrial installation was done in order to find how they can be impacted by flood. The final result of this work involves the development of generic accident scenarios and fault trees for flood related Natechs for each subsystem. These fault trees are then used for the development of two decision aid tools : a flood-induced Natech vulnerability assessment tool an assessment tool for the performance of industrial hazardous materials release emergency operations plans during a flood Natech event These two tools are currently being tested on industrial sites in France.