Thermal impacts of basaltic lava flows to buried infrastructure: workflow to determine the hazard

Abstract

Lava flows can cause substantial physical damage to elements of the built environment. Often, lava flow impacts are assumed to be binary, i.e. cause complete damage if the lava flow and asset are in contact, or no damage if there is no direct contact. According to this paradigm, buried infrastructure would not be expected to sustain damage if a lava flow traverses the ground above. However, infrastructure managers ("stakeholders") have expressed concern about potential lava flow damage to such assets. We present a workflow to assess the thermal hazard posed by lava flows to buried infrastructure. This workflow can be applied in a pre-defined scenario. The first step in this workflow is to select an appropriate lava flow model(s) and simulate the lava flow's dimensions, or to measure an in situ lava flow's dimensions. Next, stakeholders and the modellers collaborate to identify where the lava flow traverses buried network(s) of interest as well as the thermal operating conditions of these networks. Alternatively, instead of direct collaboration, this step could be done by overlaying the flow's areal footprint on local infrastructure maps, and finding standard and maximum thermal operating conditions in the literature. After, the temperature of the lava flow at the intersection point(s) is modelled or extracted from the results of the first step. Fourth, the lava flow-substrate heat transfer is calculated. Finally, the heat transfer results are simplified based on the pre-identified thermal operating conditions. We illustrate how this workflow can be applied in an Auckland Volcanic Field (New Zealand) case study. Our case study demonstrates considerable heat is transferred from the hypothetical lava flow into the ground and that maximum operating temperatures for electric cables are exceeded within 1 week of the lava flow front's arrival at the location of interest. An exceedance of maximum operating temperatures suggests that lava flows could cause thermal damage to buried infrastructure, although mitigation measures may be possible.

Using paleomagnetism to determine the heating effect of lava flows on underlying substrates

“…Altogether, these results demonstrate that substantial heat is being transferred from the lava flow into the ground below despite any insulation afforded by any potentially solidified layer of lava contacting the substrate below. Therefore, when modeling the heat transfer in lava flows such as in Patrick [2004] and Tsang et al [2020], the ground needs to be included as a heat sink.…”

“…The extent of substrate heating depends not only on the thermal properties, including initial temperature, of both substrate and lava, but also on other characteristics of the lava flow, such as its thickness, flow rate, and particularly the duration of the event [e.g. Reilly 1958;Rumpf et al 2013;Tsang et al 2020]. While other properties of the substrate, such as its water saturation, and the ambient environment, such as the air temperature, affect the extent of heating, they appear to be less influential [Tsang et al 2019].…”

“…palynomorphs) [Baker et al 2015]. Understanding the depth and temperature to which heat from the lava flow extends into adjacent substrates is also important for mitigating volcanic hazards as buried infrastructure such as water pipes and electrical cables are susceptible to high temperatures [Tsang et al 2020]. Heat from lava flows can also sterilize adjacent soils creating an ecological "dead zone" within the heated area [Blong 1984;Rumpf 2014;Baker et al 2015].…”

Lava flow hazard map of Piton de la Fournaise volcano 

“…1b). For example, the eruption of April 1977, which was the first Hors Enclos eruption since 1800, caused evacuation of Piton Sainte-Rose, entirely burnt or damaged parts of 26 buildings (including houses, a church, the police station, and a gas station), and buried part of the Sainte-Rose municipality (Kieffer et al, 1977;Vaxelaire, 2012). A second Hors Enclos eruption in March 1986 caused around EUR 400 000 of damage to houses, household contents, agriculture, roads, and utilities in the municipality of Saint-Philippe (Bertile, 1987;Morin, 2012).…”

Lava flow hazard map of Piton de la Fournaise volcano

“…This includes agricultural practices, urban planning, road network planning, assignment of protected areas, park-use planning, implementation of trail networks and installation of subterranean and above ground electric, sewage and gas networks; as well as targeting of potential zones where repair and replacement will be necessary (e.g. Tsang et al, 2020). Nonetheless, although, we argue that this hazard map is trustworthy in the long term, it may not be adapted for the short term, i.e., the next few years, over small spatial scales, i.e., hundreds of meters.…”