Application and Validation of a GIS Model for Local Tsunami Vulnerability and Mortality Risk Analysis

Abstract:

The 2011 Tōhoku tsunami caused a high number of fatalities and massive destruction. Data collected after the event allow for retrospective analyses. Since 2009, NGI has developed a generic GIS model for local analyses of tsunami vulnerability and mortality risk. The mortality risk convolves the hazard, exposure, and vulnerability. The hazard is represented by the maximum tsunami flow depth (with a corresponding likelihood), the exposure is described by the population density in time and space, while the vulnerability is expressed by the probability of being killed as a function of flow depth and building class. The analysis is further based on high-resolution DEMs.

Normally a certain tsunami scenario with a corresponding return period is applied for vulnerability and mortality risk analysis. Hence, the model was first employed for a tsunami forecast scenario affecting Bridgetown, Barbados, and further developed in a forecast study for the city of Batangas in the Philippines. Subsequently, the model was tested by hindcasting the 2009 South Pacific tsunami in American Samoa. This hindcast was based on post-tsunami information. The GIS model was adapted for optimal use of the available data and successfully estimated the degree of mortality.

For further validation and development, the model was recently applied in the RAPSODI project for hindcasting the 2011 Tōhoku tsunami in Sendai and Ishinomaki. With reasonable choices of building vulnerability, the estimated expected number of fatalities agree well with the reported death toll. The results of the mortality hindcast for the 2011 Tōhoku tsunami substantiate that the GIS model can help to identify high tsunami mortality risk areas, as well as identify the main risk drivers.

The research leading to these results has received funding from CONCERT-Japan Joint Call on Efficient Energy Storage and Distribution/Resilience against Disasters (http://www.concertjapan.eu; project RAPSODI  - Risk Assessment and design of Prevention Structures fOr enhanced tsunami DIsaster resilience http://www.ngi.no/en/Project-pages/RAPSODI/), and from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 603839 (Project ASTARTE - Assessment, STrategy And Risk reduction for Tsunamis in Europe http://www.astarte-project.eu/).