Hazard analysis and estimation of people exposure as contribution to tsunami risk assessment in the West Coast of Sumatra, the South Coast of Java and Bali

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Summary. Th e Indian Ocean Tsunami 2004 dramatically showed the catastrophic consequences when destructive tsunami waves are striking coastal areas. Moreover, it became clear that there is an urgent need for tsunami early warning systems to be set up together with appropriate awareness raising and preparedness activities. In response to this catastrophic event and under the coordination by the UNESCO Intergovernmental Oceanographic Commission the Indian Ocean countries are jointly working on the development, implementation and operation of a tsunami early warning system and the realization of disaster risk assessment and preparedness activities. A crucial component in disaster risk management is the availability of reliable information on the population distribution in the tsunami hazard zones in order to mitigate the impact of natural disasters. Th e mapping of tsunami hazard zones and the estimation of people exposure will help the government to improve the evacuation planning and to decrease the amount of people at risk. Th is paper presents research results developed in the framework of the German-Indonesian Tsunami Early Warning System project focussing on the west coast of Sumatra, the south coast of Java, and Bali. Th e methodology for the determination of the hazard zones is based on a multiscenario approach. For the estimation of the population distribution a method is applied that combines statistical data with land use information in order to disaggregate the census data proportionally. Th is approach provides estimates for day- and night-time population in the hazard zones. Th e hazard and exposure maps are provided for the whole coastal regions and, in more detail, for the study areas Padang, Cilacap and Kuta. Moreover, essential key parameters of this analysis are integrated in the Decision Support System of the Indonesian Tsunami Early Warning Centre.