Multi-hazard impact assessment of regional rural transport networks for a large eruption of Taranaki Mounga, Aotearoa New Zealand

Volcanic eruptions are complex and can generate multiple hazards, such as ashfall and lahar. Eruptions can significantly impact rural road transport network functionality, disrupting primary production, curtailing access to support services, and isolating communities. We propose a network modelling approach to assess multi-hazard volcanic impacts on rural transport systems. Rural communities in the Taranaki region are highly exposed to volcanic hazards. We apply our model to demonstrate how access between farms, marae (cultural gathering places for Māori) and service towns (with healthcare, fuel, etc.) could be affected during a future eruption of Taranaki Mounga. Across the nine eruptive scenarios assessed, a maximum of 40% of roads (>1500 km) and 45% of bridges (>1500) in the region lost service, with half of these needing significant cleaning and repairs likely to take weeks, or months especially where bridges have been destroyed by lahars. At the conclusion of one large eruption scenario modelled (L1), 12 marae (>25%) and 5,000 farms become isolated, potentially for weeks to months. This highlights a significant issue in volcanic planning globally, where impacts to roading are likely to lead to populations becoming isolated, leaving people unable to evacuate, access essential services or resume social and economic activities.