Assessing tsunami vulnerability, an example from Herakleio, Crete

Recent tsunami have caused massive loss of life, destruction of coastal infrastructures and disruption to economic activity. To date, tsunami hazard studies have concentrated on determining the frequency and magnitude of events and in the production of simplistic flood maps. In general, such maps appear to have assumed a uniform vulnerability of population, infrastructure and business. In reality however, a complex set of factors interact to produce a pattern of vulnerability that varies spatially and temporally. A new vulnerability assessment approach is described, that incorporates multiple factors (e. g. parameters relating to the natural and built environments and socio-demographics) that contribute to tsunami vulnerability. The new methodology is applied on a coastal segment in Greece and, in particular, in Crete, west of the city of Herakleio. The results are presented within a Geographic Information System (GIS). The application of GIS ensures the approach is novel for tsunami studies, since it permits interrogation of the primary database by several different end-users. For example, the GIS may be used: (1) to determine immediate post-tsunami disaster response needs by the emergency services; (2) to pre-plan tsunami mitigation measures by disaster planners; (3) as a tool for local planning by the municipal authorities or; (4) as a basis for catastrophe modelling by insurance companies. We show that population density varies markedly with the time of the year and that 30% of buildings within the inundation zone are only single story thus increasing the vulnerability of their occupants. Within the high inundation depth zone, 11% of buildings are identified as in need of reinforcement and this figure rises to 50% within the medium inundation depth zone. 10% of businesses are located within the high inundation depth zone and these may need to consider their level of insurance cover to protect against primary building damage, contents loss and business interruption losses.