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Vulnerability models

Vulnerability provides the connection to translate hazard intensity into consequences for assets.

In the NVM, vulnerability models describe how exposed assets are expected to respond when affected by volcanic hazards. For buildings, this response may be expressed as damage states, probabilities of reaching those states, repair costs, or loss ratios.

Buildings

The current NVM implementation focuses on New Zealand buildings exposed to volcanic ashfall. The 2026 technical report develops New Zealand-specific vulnerability models for representative building typologies using structured expert elicitation.

These vulnerability models support estimates of:

  • Probability of reaching defined building damage states
  • Expected repair costs
  • Building component contributions to loss
  • Uncertainty in damage and loss estimates

Expert judgement was calibrated and aggregated using Cooke's Classical Model. This provides a formal way to combine expert estimates while accounting for uncertainty and expert performance on calibration questions.

Fragility functions

Fragility functions estimate the probability that a building reaches or exceeds a specified damage state for a given hazard intensity. In the ashfall component, these functions link ashfall intensity to likely building damage.

Vulnerability and loss

Vulnerability relationships translate physical damage into financial consequences. In the NVM ashfall component, damage estimates are connected to repair costs and loss metrics so that results can be interpreted in terms of risk to the built environment.

Infrastructure

Infrastructure vulnerability is not yet part of the current national ashfall building loss implementation. Future versions of the NVM may include transport, power, water, telecommunications, and other lifeline infrastructure as exposure and vulnerability data become available.

Agriculture

Agricultural impacts are outside the current ashfall building damage implementation. Future extensions may include primary production, rural land use, and sector-specific disruption where suitable vulnerability models and exposure datasets are available.

Life safety

Life safety is not currently modelled as a direct NVM output. The present implementation focuses on building damage and financial loss from volcanic ashfall. Life safety considerations may require different exposure data, occupancy assumptions, warning and evacuation assumptions, and vulnerability models.