Put Your Money where the benefit is
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ABSTRACT:
| Flooding is New Zealand’s most prevalent and consistently impactful hazard, causing damage and disruption to infrastructure and communities for potentially prolonged periods of time. To tackle this challenge New Zealand needs to be moving towards more resilient, future-proofed communities with the reduction and management of flood risk. An improved understanding of risk allows for better spending and is necessary to inform the most impactful decision-making that develops resilience. As part of the MBiE funded Endeavour Programme, “Mā te haumaru ō ngā puna wai ō Rākaihautū ka ora mō ake tonu: Increasing flood resilience across Aotearoa”, a series of tools and process workflows are being developed to help assess the national exposure to flooding for Aotearoa. As part of the Research Aim 2: Flood Risk to the Built environment mahi, we have developed a workflow to support the delivery of flood risk management interventions to enhance the overall resilience across the motu. Our presentation will share the current status of the programme, the development of the process and through application across a case study area. Using RiskScape, a risk modelling tool developed by GNS and NIWA, we have developed a workflow for the cost-benefit analysis (CBA) of several flood mitigation options. RiskScape is a flexible multi-hazard risk modelling engine capable of calculating the consequences of flooding to people, buildings, infrastructure, the environment and more. These consequences can be input into the cost-benefit analysis process to determine whether an option yields more than it costs. This supports the decision-making process towards the outcome that is most beneficial. This can be on a national, regional, or local scale. Whakatāne was used as the case study for this analysis. Several high-level flood mitigation options were modelled in InfoWorks ICM, using a range of storm recurrence intervals and climate change adjustments to produce hazard layers and test the workflows for the National Flood Mapping work. Building exposure layers were created to represent a progression from the current buildings to a maximum future growth scenario based on the district plan. These different hazard and exposure layers were then input into a trained RiskScape model to produce damage estimates for each case to be used in CBA. CBA is a tool used to assess the costs and benefits of different options for addressing a specific problem, enabling a comparison between the options and a base case which is the future scenario where no action is taken. The CBA process supports the definition of the most acceptable option for the defined problem. The outcome of the CBA needs to be considered with awareness of the associated uncertainty, adaptability, and the results of sensitivity testing. We also discuss how CBA can be expanded to become an MCA (Multi Criteria Analysis), which allows for the social, political, and environmental context to be considered. |