Hazard mitigation planning is multi-faceted. First, plans should be holistic, considering a number of community goals in addition to risk management. Second, plans should guide development over the long term, and need to consider how the frequency, magnitude and consequences of hazards change over time. To assess future changes, a large number of environmental and anthropogenic factors that affect hazard risk need to be estimated, yet strong uncertainty exists in estimating these factors. Third, implemented plans have a wide social, environmental and economic impact; impacts across these systems need to be assessed. Finally, resources for mitigation are limited; benefits of mitigation need to be clear to make a business case to decision makers and the public. Due to these facets, decision-support systems are invaluable when planning mitigation.

This paper presents an integrated model for mitigation planning. To assess the impact of mitigation options across the wider social, economic and environmental systems, the proposed decision support system (DSS) integrates flood, bushfire, earthquake, and coastal-surge risk models with social, natural and built environment models. The integrated model is used to estimate the values of multiple decision criteria, to enable holistic planning. Criteria estimated by the DSS include hazard, vulnerability, risk, cost-benefit analysis and other social and environmental variables. To understand how these criteria change over the long term, models of climate, demographics and economic change are used. To enable the spatial assessment of the criteria a land-use model is used, which also allows the consideration of spatial planning and land-management mitigation options, in addition to structural and educational measures. Finally, the integrated model is linked with optimisation, which is designed to screen through planning options, and hence discover innovative sets of policy options.