SENAT
Report n° 117 (2007-2008) by M. Roland COURTEAU, Senator (for the parliament office for the evaluation of scientific and technological choices) - Appendix to the minutes of the 7 December 2007 session
Disponible au format Acrobat (21 Moctets)
d) Voluntary experiments with the management of local-tsunami warnings
Throughout this study, your rapporteur has insisted on the fact that it is particularly difficult to predict the impact of local tsunamis: considering the short reaction times, the warning centres hesitate to assume this responsibility, insofar as they run the risk of seeing their messages arrive after the wave has already struck the coast.
During the last session of the ICG/NEAMTWS in Lisbon, the member states agreed that the regional warning centres would only deal with those tsunamis with a reaction time of over 15 minutes. For tsunamis with shorter reaction times, the responsibility for issuing the warning falls to the national centres. Indeed, issuing an effective warning when the reaction time does not exceed 15 minutes requires a much denser network of sensors than that necessary to monitor regional tsunamis, as well as an automated warning system using sirens. This therefore entails a significant investment, which must be related to the frequency of the expected hazard. In addition, the warning's success is not guaranteed and depends more than ever on the correct reaction of the population and therefore on raising the public's awareness of the tsunami risk.
Therefore, it would be unrealistic to want to generalize a local-tsunami warning system to all of France's coasts. However, your rapporteur believes that in certain zones that are exposed to a high local-tsunami risk, and whose local elected officials are well aware of the risk, a warning system suited to local tsunamis could be experimented with.
In metropolitan France, the greater Nice area could be interested in this trial: in this area, the local tsunami hazard represents a real risk, as was demonstrated on 16 April 1979; this zone is particularly vulnerable, considering its dense coastal population all year long, with peaks in the summer; our understanding of the hazard in this zone is good, thanks to the many geophysical studies that have already been carried out on gravitational instabilities in the Marcel Cirque; finally, this region can be considered a model in terms of raising the local government's awareness of the tsunami risk.
Therefore, an experiment could be developed, that brings together in close collaboration various government services (in particular, the civil-protection services), the key scientific bodies studying tsunamis, local governments and harbour authorities, as well as manufacturers to design an effective data-transmission system. If the trial proves successful, the system could be extended to other coastal regions, both in metropolitan France and overseas.
In this regard, your rapporteur would like to point to the project elaborated by the "marine" and "territorial risk and vulnerabilities" competitiveness clusters of the Provence-Alpes-Côte d'Azur region, which seeks to set up a RATCOM ("Tsunami Warning System for the Mediterranean Coasts"). This project's objective is to establish an automated warning system for local tsunamis.
The proposed system is designed around two main functional components:
- A "descending component", which seeks to offer effective and reliable communication means allowing for the transmission of warnings via first a local network, then a mass broadcast.
- A "rising component", which is meant to deliver - based on automatically processed measurements gathered both at sea and on land - a qualified, coordinated tsunami warning bulletin, meant to minimize, in particular, the chance of issuing a false warning. In addition to the processing of this data in real-time, decision-making tools based on prior modelling will have to be created and made available to those bodies responsible for crisis management and intervention.