A Methodology for Consistent Modelling of Natural Hazards Sanabria L.A. and Dhu T. Geoscience Australia, E-Mail: augusto.sanabria@ga.gov.au Keywords: Probabilistic modelling, earthquake, inundation modelling, risk analysis. EXTENDED ABSTRACT The need for a new approach to understand and manage the risk posed by natural hazards in Australia has been acknowledged and emphasised by Australian Commonwealth and State governments. To this effect the Council of Australian Governments (COAG) commissioned a review of natural disaster relief arrangements in June 2001. The results of the review were published in the report Natural Disasters in Australia: Reforming Mitigation, Relief and Recovery released by the Department of Transport and Regional Services (DOTARS) in early February 2004. The report proposes a fundamental shift in focus beyond relief and recovery towards cost- effective, evidence-based disaster mitigation. Consequently, while disaster response and reaction plans remain important, the move is now towards anticipation and mitigation against natural hazards. The report includes twelve reform commitments. Many of these commitments are being implemented through the Disaster Mitigation Australia Package (DMAP), being administered by DOTARS. DOTARS has invited Geoscience Australia (GA) to be a technical advisor and to assist in the implementation of DMAP over the next five years. DOTARS and GA are working together to implement two of the most important reform commitments specified under recommendation 4 of the report. These two reform commitments are: • Develop and implement a five year national program of systematic and rigorous disaster risk assessments. • Establish a nationally consistent system of data collection, research and analysis to ensure a sound knowledge-base on natural disasters and disaster mitigation. In this context GA is developing risk models and innovative approaches to assess the potential losses to Australian communities from a range of sudden impact natural hazards. These models aim to assess the economic and social impacts of natural hazards in a consistent way to allow the direct comparison of risks from different hazards. Currently, GA is developing risk assessment models for earthquakes, inundations, tsunami, cyclones, and synoptic winds. A consistent approach to incorporating uncertainties into risk models for each of these hazards is essential so that risks from different hazards may be compared. This is a particularly difficult task due to the numerical models for various hazards being developed in isolation, e.g. the methodology used in an earthquake risk model can be totally different from the methodology used in a cyclone risk model (one model can be deterministic whilst the other can be probabilistic, for instance) making comparison of results from both models very difficult. This paper aims to highlight and address this issue by identifying the main sources of uncertainty in earthquake and cyclonic inundation models and presenting a generalised approach for modelling natural hazards. 765