Understanding the blind spots in the warning process during NaTech events: lessons from the Blayais Nuclear Power Plant Flood in France (1999)

In a context of increasing industrialization, population growth in hazard-prone areas and intensification of hazard triggers, integrating NaTech risks into crisis management planning and warning processes has become more and more essential. This paper examines lessons learned from Hurricane Martin, which struck France on December 27, 1999 - causing the flooding of the Blayais Nuclear Power Plant (NPP) on the Gironde estuary. By focusing on the alert process and the coordination among actors, the study examines lessons learned beyond the dominant emphasis on technical and procedural solutions. It reconstructs the alert timeline, information flows, and decision-making chain based on reports from prefectural services, nuclear technical reports, and post-event press articles, in order to produce a "consolidated feedback". The study shows that vulnerability arises not only from physical impacts on infrastructure but also from fragmented communication and coordination, as each actor followed its own institutional logic and corrective procedures. This fragmentation highlights dilemmas related to alerts that could have arisen, such as conflicting instructions between sheltering (to limit radiological exposure) and evacuation (due to flooding). Finally, this near-miss accident demonstrates the need for preparatory lessons-learned frameworks that capture how risk is progressively built through signal interpretation, uncertainty management, governance arrangements, and alert practices in complex NaTech crises.

Keywords: warning, NaTech, experience feedback, nuclear, flood, storm.