Daniel Blake (supervised by Tom Wilson), University of Canterbury (EQC funded project 13/U646)
(Journal publications accepted in lieu of final report - referenced below)
Auckland is built on an active volcanic field. During a future volcanic eruption, functional transport networks will be critical for evacuations, as well as for immediate and long-term recovery once direct threats have subsided. Ash is generally the most disruptive and widely dispersed volcanic hazard, potentially impacting road transport networks for months to years. In Auckland ash may originate from both local eruptions and those further afield in the North Island.
Common ash impacts on roads include:
Skid resistance reduction
Road marking coverage
Visual range reduction
Few studies have attempted to quantify these impacts in detail, particularly for ash <10 mm thick. This research involves the conception and implementation of a series of experiments in the Volcanic Ash Testing Laboratory (VAT Lab) at the University of Canterbury to provide quantitative data relating ash characteristics to road transport impact types.
The results, along with empirical evidence and expert advice from staff at transport organisations, are being used to inform models of disruption across Auckland's road network following hypothetical eruptive scenarios. Findings can be used to improve evacuation planning and clean-up strategies, and provide safe operating thresholds and specific travel advice for future ashfall events, increasing transport system resilience.
Transportation networks are critical infrastructure in urban environments. Before, during and following volcanic activity, these networks can incur direct and indirect impacts, which subsequently reduces the Level-of-Service available to transportation end-users. Additionally, reductions in service can arise from management strategies including evacuation zoning, causing additional complications for transportation end-users and operators.
Here, we develop metrics that incorporate Level-of-Service for transportation end-users as the key measure of vulnerability for multi-hazard volcanic impact and risk assessments. A hypothetical eruption scenario recently developed for the Auckland Volcanic Field, New Zealand, is applied to describe potential impacts of a small basaltic eruption on different transportation modes, namely road, rail, and activities at airports and ports. We demonstrate how the new metrics can be applied at specific locations worldwide by considering the geophysical hazard sequence and evacuation zones in this scenario, a process that was strongly informed by consultation with transportation infrastructure providers and emergency management officials. We also discuss the potential implications of modified hazard sequences (e.g. different wind profiles during the scenario, and unrest with no resulting eruption) on transportation vulnerability and population displacement.
The vent area of the eruption scenario used in our study is located north of the Māngere Bridge suburb of Auckland. The volcanic activity in the scenario progresses from seismic unrest, through phreatomagmatic explosions generating pyroclastic surges to a magmatic phase generating a scoria cone and lava flows. We find that most physical damage to transportation networks occurs from pyroclastic surges during the initial stages of the eruption. However, the most extensive service reduction across all networks occurs ~6 days prior to the eruption onset, largely attributed to the implementation of evacuation zones; these disrupt crucial north-south links through the south eastern Auckland isthmus, and at times cause up to ~435,000 residents and many businesses to be displaced. Ash deposition on road and rail following tephra-producing eruptive phases causes widespread Level-of-Service reduction, and some disruption continues for N1 month following the end of the eruption until clean-up and re-entry to most evacuated zones is completed. Different tephra dispersal and deposition patterns can result in substantial variations to Level-of-Service and consequences for transportation management.
Additional complexities may also arise during times of unrest with no eruption, particularly as residents are potentially displaced for longer periods of time due to extended uncertainties on potential vent location. The Level-of-Service metrics developed here effectively highlight the importance of considering transportation end-users when developing volcanic impact and risk assessments. We suggest that the metrics are universally applicable in other urban environments.
References for publications accepted as final report:
Daniel M Blake, Natalia I Deligne, Thomas M Wilson, Jan M Lindsay, Richard Woods - Investigating the consequences of urban volcanism using a scenario approach II: Insights into transportation network damage and functionality-Journal of Volcanology and Geothermal Research Volume 340, 15 June 2017, Pages 92-116 - doi.org/10.1016/j.jvolgeores.2017.04.010
Daniel M Blake, Thomas M Wilson, Carol Stewart - Visibility in airborne volcanic ash: considerations for surface transportation using a laboratory-based method – Journal of Natural Hazards May 2018, Volume 92, Issue 1, pp 381-413 - doi.org/10.1007/s11069-018-3205-3
Daniel Mark Blake, Natalia Irma Deligne, Thomas McDonald Wilson, Grant Wilson - Improving volcanic ash fragility functions through laboratory studies: example of surface transportation networks-Journal of Applied Volcanology Society and Volcanoes (2017)6:16 - doi 10.1186/s.13617-017-0066-5
Daniel M Blake, Thomas M Wilson, Christopher Gomez - Road marking coverage by volcanic ash: an experimental approach-Journal of Environmental Earth Sciences October 2016, 75:1348 – doi.10.1007/s12665-016-6154-8
Daniel M Blake, Thomas M Wilson, Jim W Cole, Natalia I Deligne, Jan M Lindsay - Impact of volcanic ash on road and airfield surface skid resistance-Journal of Sustainability Journal 9(8):1389 - doi: 10.3390/su9081389