Volcanic Ashfall: What Damage Could Be Caused After An Eruption? New Research To Assist Authorities And Communities

Hundreds of thousands of North Island homes could be covered in ashfall following a volcanic eruption, and assessing the damage could take months.

New research funded by the Natural Hazards Commission will enable authorities to quickly assess the damage from volcanic ashfall during and after an eruption to better respond to the needs of each community.

“A volcanic eruption could affect thousands of buildings around the North Island, and we need a New Zealand model that provides us with a quick assessment of the scale of the damage,” says Dr Josh Hayes, Natural Hazard and Risk scientist at GNS, who led this research.

The research project aims to fill a gap between the existing internationally developed models and local New Zealand post-eruption data collection.

“We have not had any major ashfall since Mt Ruapehu erupted in 1995 and 1996, and that didn’t cause that much damage, so our understanding of the effects is highly informed by overseas experiences,” says Dr Hayes.

The GNS scientist explains that physically assessing ashfall damage is time-consuming, particularly widespread ashfall events, so creating a damage forecasting model is hugely beneficial for authorities and communities to concentrate resources.

“We will use existing overseas damage forecasting models, but will calibrate those models with specific New Zealand data rapidly following an eruption” says Hayes.

He says a rapid modelling tool that can be constantly adjusted with fresh data will be particularly critical if a volcano enters a prolonged eruptive episode with ongoing ashfall events.

NHC Head of Research Dr Natalie Balfour says the GNS project is a great extension of the continuous investment NHC makes into volcanic hazard research.

“Over the past years, NHC has funded projects that have provided valuable insights into how New Zealand homes stand up to different amounts of ash on their roof, as well as predicting where the ash will travel by using MetService weather forecasting,” says Dr Balfour.

Dr Hayes says his project builds on the findings from previous NHC-funded research.

“Knowing where the ash will travel and forecasting the amount of ashfall loading that accumulates on roofs in different areas will be the key metric when we assess the damage to buildings from volcanic ash.”

The new model will use scientific data, engineering reports and satellite images, but also crowd-sourced data, like social media, to build a comprehensive picture after an eruption.

“Naturally the reliability of information varies across different sources, so our methodology will factor in the reliability of different post-event data,” says Dr Hayes who adds that this innovative approach will optimise the use of limited data post-event to ensure the most accurate damage assessment.

The collaborative team, consisting of GNS, University of Canterbury, and Nanyang Technological University (Singapore), is currently creating scenarios and developing the modelling approach, and the two-year project is expected to complete the new modelling tool by the end of 2025.

About the Natural Hazards Commission Toka Tū Ake

• The Natural Hazards Commission Toka Tū Ake exists to help New Zealanders prepare for and recover from the impact of natural hazards. We invest in natural hazard research and education to help communities to reduce their risks, and we provide natural hazard insurance cover for damage to insured homes and some residential land from a range of natural hazards.
• Our name changed from Earthquake Commission (EQC) in July this year with the introduction of our new governing legislation, the Natural Hazards Insurance Act. Our new name reflects that our scope extends beyond earthquakes to deliver insurance and expertise for a range of natural hazards, including volcanic eruptions, hydrothermal activity, tsunamis, land slips. NHCover also covers some damage to residential land from storms and floods. Toka Tū Ake means the foundation from which we stand strong, together.
• We invite you to refer to us as Natural Hazards Commission Toka Tū Ake at first reference, and NHC Toka Tū Ake or NHC thereafter.
• You can read more about our annual investment in research and resilience through regular updates on our news page or through our annual highlights report.

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