Method for Evaluating Vulnerability to Tsunamis of low-to-medium intensity: Application to the French Côte d'Azur

Abstract : Today, the study of tsunami risk has become a recurrent concern for crowded coastal areas, and this is true even for those that normally seem to be the least prone to the phenomenon. In this framework, the BRGM has for the past five years been compiling and managing an historical database devoted to tsunamis that may have affected the shores of France. Concurrently, simulations of tsunamis for plausible major seismic or gravity-driven events have been conducted. These have indicated that the south of France is indeed subject to the risk of a tsunami of low to medium intensity. Between 2009 and 2010, the research project RATCOM has made it possible to establish the principles for assessing vulnerability and calculating damage and human losses for moderate tsunamis. The method thus developed is complementary to those already proposed for tsunamis of larger intensity. Applications of this method using the BRICE (©brgm) simulation tool for risk scenarios reveal that the level of risk has increased quite substantially over just a few decades, even for tsunamis of low to medium intensity (water height less than 1 m). This is essentially due to the exponential growth of urban development along the coastline and to tourist pressure. Although such events will not cause destructions to buildings comparable to those in Indonesia (2004) and Japan (2011), still weak phenomena can be responsible for serious human losses. On the Côte d‟Azur, the potential number of victims is large enough to warrant immediately instating preparatory measures designed to cope with the possibility of such a scenario.