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Subject: search.filters.subject.Volcanic ashfall

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    Including dynamics in a network-based stochastic multihazard model: A virtual testbed for volcanic ashfall and flood risk assessment
    (Elsevier B.V., 2025-12) Bebbington M; Dunant A; Harte D; Mead S; Whitehead M
    Network models have been previously proposed for spatial cascades of natural hazard events. These have generally not taken time into account, with the cascade of events effectively assumed to occur instantaneously. This study introduces a dynamic, network-based stochastic model developed as a virtual testbed to simulate complex multihazard interactions between multiple temporal processes, often occurring on different time scales. Since state of the art physical models generally involve heavy computation, the use of computationally simple probability distributions to describe the dynamics and interaction of the hazard events enables a larger number of model simulations, promoting greater robustness of model forecasts. The network modelling approach aims to allow the identification of key elements of the system that are most vulnerable, develop risk mitigation strategies, and examine restoration plans. We exemplify our methodology by investigating impacts of volcanic ashfall on river flow dynamics in the Rangitaiki and Tarawera river systems in New Zealand, simulating hydrological processes over a 365-day period with a volcanic eruption. Our results demonstrate how testbeds can be use to explore “what-if” cascading impacts scenarios, by providing a flexible, computationally efficient framework, offering crucial support for Disaster Risk Management (DRM) in volcanic regions.
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    A new volcanic multi-hazard impact model for water supply systems: Application at Taranaki Mounga, Aotearoa New Zealand
    (Elsevier B.V., 2024-12-24) Porter H; Wilson TM; Weir A; Stewart C; Craig HM; Wild AJ; Paulik R; Fairclough R; Buzzella M
    Water supply systems provide an essential service for society and are highly vulnerable to damage and disruption during volcanic eruptions. Impacts sustained by water supply systems during volcanic eruptions have resulted in prolonged and repeated supply outages. Previous approaches to assessing volcanic impacts to water supply systems have been relatively simplistic, based on hazard intensity thresholds, and only considering direct damage. There is a need for water supply risk assessment approaches informed by vulnerability models that consider the pivotal role of system design and indirect impacts; such as supply and demand fluctuations, personnel shortages, and disruptions to interdependent infrastructure networks. We present a whole-of-system volcanic vulnerability model and impact assessment framework for water supply systems that can be used to estimate system-wide impacts during future volcanic eruptions. This model is developed in collaboration with volcanic risk researchers and water supply engineers in Aotearoa New Zealand and applied to a case study in the Taranaki region for a long-duration and multi-hazard eruption scenario from the active stratovolcano Taranaki Mounga. The model provides an assessment of the functionality of water supply systems affected directly and indirectly by the scenario eruption, interdependent critical infrastructure services, and associated emergency management actions (e.g., evacuations). This scenario, and its modelled impacts, allows practitioners to explore potential mitigation and emergency response options. This framework can be applied in other volcanic contexts to assess impacts on water supplies from future eruptions, highlight key systemic vulnerabilities, and provide a basis for the prioritisation and implementation of risk management strategies.
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    Agriculture and forestry impact assessment for tephra fall hazard: fragility function development and New Zealand scenario application
    (Volcanica, 2021-12-31) Craig HM; Wilson TM; Magill C; Stewart C; Wild AJ
    Developing approaches to assess the impact of tephra fall on agricultural and forestry systems is essential for informing effective disaster risk management strategies. Fragility functions are commonly used as the vulnerability model within a loss assessment framework and represent the relationship between a given hazard intensity measure (HIM; e.g. tephra thickness) and the probability of impacts occurring. Impacts are represented using an impact state (IS), which categorises qualitative and quantitative statements into a numeric scale. This study presents IS schemes for pastoral, horticultural, and forestry systems, and a suite of fragility functions estimating the probability of each IS occurring for 13 sub-sectors. Temporal vulnerability is accounted for by a ‘temporality/seasonality coefficient,’ and a ‘fluoride toxicity coefficient’ is included to incorporate the increased vulnerability of pastoral farms when tephra is high in leachable fluoride. The fragility functions are then used to demonstrate a deterministic impact assessment with current New Zealand exposure.