The growing wildfire risk at the urban margins

 


By Gavin McCleave, science communications intern

24/3/21

 

Fires on the margins of urban areas in Aotearoa New Zealand have been relatively rare in the past but are becoming more common. Climate change is making the country hotter and drier, and land usage at the rural-urban interface (RUI) is rapidly changing as subdivisions are creating more than 5,000 new semi-rural sections every year. This is increasing the number of people and homes in the RUI, increasing the risk of wildfires starting, and increasing the risk of fires spreading into suburban areas.

This was demonstrated by the Port Hills wildfire in Christchurch in 2017. As described in 2018 research by Scion’s Lisa Langer and Simon Wegner, the nine destroyed homes were lifestyle properties, but the majority of the 450 homes threatened by the wildfire were within the urban fringe and city limits.

Fire mitigation for rural properties is well understood by local government and fire agencies and this knowledge has been passed to rural property owners and communities, but greater focus is now required on communities in the RUI.

The RNC Weather and Wildfire research programme is using new weather modelling technologies and methods to quantify the effects of a hypothetical wildfire breaking out in a subdivision on Mount Iron, near Wānaka.

 

Mt Iron subdivision at Wānaka. Credit: Phyllis, Flickr

The Mount Iron community was chosen because it is a suburban development in progress, and, being in Otago, is at high risk of wildfire as it has highly combustible fuels like mānuka, limited road access and water resources, periodic strong north-westerly winds, and increasingly dry summers. Mount Iron has already been struck by a wildfire, in January 2012.

Effective mitigation strategies to reduce the risk of physical damage to properties include actions by local government planners such as making building consents contingent on using fire-resistant building materials, and minimum site-spacing between buildings and flammable vegetation.

But the social aspects are just as important; for example ensuring affected communities know about the risk of wildfires occurring, how to reduce the likelihood and impact of wildfires, and what to do to save their lives and protect their properties in the event of a wildfire.

Research in 2019 co-authored by Lisa Langer describes wildfire experiences and actions by predominantly Māori residents during the 2011 Karikari Peninsula wildfire, and preparedness before and after the event. Researchers found that experiencing the fire encouraged most residents to become better prepared. Whānau and marae also helped to inform and support residents during and after the wildfire.

The paper provides useful recommendations for improving preparedness for wildfires and encouraging safe fire use in rural communities across New Zealand. The success of this study led to Scion social and kairangahau Māori researchers conducting a study with a hapū in the Hokianga to explore what a resilient hapū would look like and to contribute towards planning with Māori communities to reduce natural hazard risk. The Karikari study also helped shape other Scion-led social fire research on targeted protection against extreme fire. The combined research has helped inform Fire & Emergency New Zealand’s Māori engagement policy and contributed to their work with tangata whenua to build resilience of Māori communities.

 

Impact case study:

Model and tools for decision-making

 


How did Resilience Challenge research have an impact in 2019-2020?

 

Central to our mission to accelerate natural hazard resilience is the development of new models and tools to quantify hazards and impacts in more realistic ways, providing better assessments of resilience options to decision-makers.

Development of new models is iterative, requiring repeated testing and validation, and their application usually comes at the end of an extensive period of development. RNC is driving meaningful enhancements and innovations in this area, building on work in Phase 1, the Natural Hazards Research Platform, and leveraging existing New Zealand tools such as RiskScape and MERIT.

Updated hazard map for Whakapapa skifield. Credit: GNS Science

Earlier this year, Volcano programme research was integrated into updated hazard posters  for Turoa and Whakapapa skifields, as part of a collaboration with the Department of Conservation. Researchers were also commissioned by Ruapehu Alpine Lifts to produce a technical report on potential lahar hazard in the Whakapapa ski area. A new lahar simulation model, calibrated to previous lahars, was used to estimate the lahar footprint and impact for a range of scenarios. Results of the report have been used to develop safety measures for the new Sky Waka gondola.

 

 

Dr Nicky McDonald and colleagues from ME Research produced economic modelling utilising the MERIT (Measuring the Economics of Resilient Infrastructure Tool) capability developed in Phase 1, to assess the economic consequences of fuel outage scenarios following the Auckland-Marsden Point fuel pipeline failure. MERIT was applied to five disruption scenarios, which were then evaluated with and without mitigation options to better understand the impact of disruption and potential value of mitigation actions for New Zealand. The report was prepared for MBIE and findings also contributed to the Board of Inquiry into the 2017 Auckland Fuel Supply Disruption.

As part of our Coastal Flooding project led by Prof Karin Bryan (University of Waikato) and Dr Scott Stephens (NIWA), Dr Shari Gallop and Masters student Akuhata Bailey-Winiata (Te Arawa, Ngāti Tūwharetoa) carried out a summer project to determine the proximity of coastal marae (located within 2km of the coast) to coastal and river waterbodies. They found that 93% of coastal marae are located in the North Island; over 45% of coastal marae are within 200 meters of the coastline; and approximately 70% of coastal marae are located below 20 meters elevation relative to mean sea level. Data will be used as a baseline for determining risk and vulnerability of coastal marae to coastal hazards and sea-level rise. Akuhata’s research was recognised by the New Zealand Coastal Society who awarded him with a Māori and Pacific Island Research Scholarship in July 2020. 

Our Built Environment programme has completed new hazard maps for Bay of Plenty marae (showing fault lines, flooding, geothermal, liquefaction, and tsunami zones) using data from Rotorua City Council and Environment Bay of Plenty. The maps were provided to Te Arawa Lakes Trust collaborators, and are intended to be used to catalyse conversations with marae regarding adaptation and preparedness planning.

Part of our Weather and Wildfire programme involves the modelling of credible ‘what-if’ scenarios. What if the path of ex-Tropical Cyclone Cook (which did much damage in eastern Bay of Plenty in 2017) had been further west and hit our biggest population centre, Auckland? Weather scenario modelling at such fine-grid resolutions is a first for New Zealand, and allows detailed impact modelling to be carried out for a variety of coincident weather, flood, and landslide hazards, building a credible worse-case impact scenario for Auckland and surrounding districts. The early modelling is highlighting the potential for extreme impacts in Auckland, and in other areas well away from Auckland such as the higher elevations of the Kaimai ranges.

 

New modelling shows what could have happened if ex-TC Cook has tracked over Auckland. Credit: Ian Boutle, 2020

The primary goal of our Earthquake-Tsunami programme is to generate synthetic earthquakes using computer models. Big earthquakes and tsunamis (thankfully) don’t happen very often. A downside of this infrequency is that limited information from past earthquakes makes the job of forecasting future earthquakes and tsunamis challenging. One way of getting over these limitations is to generate synthetic earthquakes over millions of years using computer programs.

The team, led by Dr Bill Fry and Prof Andy Nicol, now has a first iteration of a synthetic seismicity model for New Zealand that incorporates all of the faults used for the National Seismic Hazard Model. This is a successful proof of concept. Further, through extended international collaboration, they have produced basic ground motion predictions from this model. This is an exciting and important stepping-stone in a programme of work that aims to improve future earthquake, tsunami and landslide hazard models in New Zealand.

 

This case study was submitted to the Ministry of Business, Innovation and Employment as part of our 2019-2020 annual reporting. 

 

High resolution ex-tropical cyclone modelling

 


What if ex-Tropical Cyclone Cook had hit Auckland?

 

By Dr Richard Turner

Many of the objectives of the Weather and Wildfire programme are highly dependent on creating ultra-high resolution, multi-hazard weather models. Part of the work involves the modelling of credible ‘what-if’ scenarios such as what if the path of ex-Tropical Cyclone Cook (which did much damage on the eastern Bay of Plenty coast) had been further west and hit Auckland.

To do this scenario modelling at such fine grid resolutions has not been done before in New Zealand and it will allow detailed impact modelling to be done for a variety of coincident weather, flood, and landslide hazards – building a credible worse-case impact scenario for Auckland and surrounding districts. 

 

Model images by Ian Boutle, 2020

  
The example plots above are some early results for Auckland, with the centre of ex-Tropical Cyclone Cook clearly evident offshore to the west of Auckland. It is interesting to note the extreme gust speeds in other areas well away from Auckland such as the higher elevations of the Kaimai Ranges – simulated to be well over 250 km/hr. For some more detail on the background to the ex-tropical cyclone modelling project there is an interesting NZ Herald article from January 2020 that is well worth a read.

At a recent workshop, presentations on the weather scenario (cyclones, fire, and winter storm) methodology, weather models, flood models, RiskScape (impact modelling) and data-sharing protocols were provided to interested researchers and modellers (coast, flood, landslide, and i-tool developers) within the Weather and Wildfire programme. For more information on the weather scenario modelling, contact Richard Turner.

 

Student Profile: Sara Harrison

 


Exploring the Data Needs for Impact-based Forecasting and Warning Systems in New Zealand

 

 

 

A bit about me 

 

I’m from Barrie, Ontario, Canada – a mid-sized city north of Toronto, in between the Great Lakes. We’re exposed to

 lots of active weather year-round. We experience white-out conditions from snowstorms in winter, and thunderstorms and the odd tornado in summer. Severe weather has always impacted my life, causing ‘snow-days’ due to rough winter roads, or outdoor soccer game cancellations due to risk of lightning strikes.

With a fascination for natural hazards and a love for reading and creating maps, I decided to study Geography at the University of Waterloo. For my honours thesis, I assessed the post-storm damage surveys conducted in Canada following potentially tornadic events. This sparked an interest in understanding how we could use crowdsourcing for disaster management, which I explored for my Masters of Environmental Studies (MES) degree, at the same university.

After completing my MES, I did some private GIS work but found that I preferred research. Fortunately, I met my current supervisor, Dr. Sally Potter from GNS, at the World Weather and Open Science Conference in Montreal just before starting my MES. We added each other on Facebook and three years later Sally posted a call for scholarship applications for a PhD project that aligned perfectly with my interests. The rest is history! In my spare time I enjoy rock climbing (bouldering), SCUBA diving, and travelling. 

 

My project

 

For my PhD I aim to map out existing and potential impact data sources from severe weather events in New Zealand to support a fairly new kind of warning system: impact-based forecasts and warnings. My guiding research question is: How is impact data currently collected, stored, and shared in New Zealand and how can this impact data support an impact-based forecasting and warning system?

In answering this question, I hope to identify current and potential sources of impact data for impact-based forecasts warnings and other applications like risk/impact modelling, response and recovery efforts, as well as challenges and opportunities in sharing the data and strengthening inter-agency collaborations for enhanced disaster risk reduction in New Zealand.

To do this, I’m interviewing people with expertise in creating, collecting, sharing, and using impact data for a variety of purposes including impact/risk modelling, severe weather warnings, and response. I’m using a grounded theory methodology to identify relationships and interdependencies between components in the impact-based forecasting and warning system and associated data infrastructure. I’m taking a sociotechnical approach so that I can explore both the social aspects of data creation, sharing, and use; along with the technical capabilities, limitations, and opportunities.

My research fits under the RNC2 Weather & Wildfire theme and aims to contribute to three efforts of the theme:

  • to help build national extreme weather hazards and impacts datasets,
  • to increase our understanding of impacts on communities, infrastructure, and economic activity, and
  • to improve the forecasting and warning services in New Zealand so that they provided more meaning to warning recipients.

My supervisors guiding me through this journey are Dr. Sally Potter (GNS), Dr. Raj Prasanna (Joint Centre for Disaster Research, Massey University), Dr. Emma Hudson-Doyle (Joint Centre for Disaster Research, Massey University), and Prof. David Johnston (Joint Centre for Disaster Research, Massey University).

 

 

Next steps

 

The expected outcome is to outline the process of getting impact data from the source (e.g. the public) to the end-users (e.g. Civil Defence groups, the MetService, impact/risk modellers, etc) for impact-based forecasts and warnings. This will help stakeholders understand what is available to them, and how they can access and contribute to it. Within a wider scope, this will support efforts towards meeting the requirements of the Sendai Framework to build a national impacts and losses database, as well as contribute to the implementation of impact-based forecasts and warnings in New Zealand.