Impacts to agriculture and critical infrastructure in Argentina after ashfall from the 2011 eruption of the Cordón Caulle volcanic complex: an assessment of published damage and function thresholds

Heather Craig,Gustavo Villarosa,Peter Baxter,Thomas Wilson,Carol Stewart,Valeria Outes

doi:10.1186/s13617-016-0046-1

Abstract

The 2011 Cordon Caulle (Chile) was a large silicic eruption that dispersed ashfall over 75,000 km2 of land in Central Argentina, affecting large parts of the Neuquen, Rio Negro, and Chubut provinces, including the urban areas of Villa la Angostura, Bariloche and Jacobacci. These regions all received damage and disruption to critical infrastructure and agriculture due to the ashfall. We describe these impacts and classify them according to published damage/disruption states (DDS). DDS for infrastructure and agriculture were also assigned to each area using the tephra thickness thresholds suggested by previous studies reported in the volcanological literature. The objective of this study was to evaluate whether the impacts were as expected based on the DDS suggested thresholds, and to determine whether other factors, apart from ashfall thickness, played a part. DDS thresholds based on tephra thickness were a good predictor of the impacts that occurred in the semi-arid steppe area around Jacobacci. This was unexpected as the more severe impacts were related to the challenging environmental conditions (low precipitation levels, high levels of wind erosion) and the daily wind remobilisation of ash that occurred, rather than the ashfall thicknesses received. The temperate region, including Villa la Angostura and Bariloche, performed better than the DDS assigned by ashfall thickness suggested. Despite deposits as thick as 300 mm, full recovery occurred within months of the ashfall event. The DDS scales need to incorporate a wider range of system characteristics, and environmental and vulnerability factors, as we propose here.

Highlights

Volcanic ashfall is commonly the most widespread hazard to occur after an explosive eruption (Dingwell et al, 2011)
Overall, ashfall impacts to infrastructure and agriculture after the 2011 Cordón Caulle Volcanic Complex (CC-VC) eruption were broadly similar to impacts observed elsewhere after comparable ashfall events
Severe wind remobilisation in the semi-arid steppe region meant ashfall thicknesses were much lower, the damage/ disruption states (DDS) observed were often the same as those experienced in areas more proximal to the volcano that received much greater ashfall thicknesses

Summary

Introduction

Volcanic ashfall is commonly the most widespread hazard to occur after an explosive eruption (Dingwell et al, 2011). Ashfall can be highly disruptive and potentially damaging to many sectors of society, including critical infrastructure and agricultural systems, due to its abrasive, corrosive and conductive potential This means that the likely impacts of an ashfall event need to be well understood and planned for in order to minimise disruption and damage (Wilson et al 2012a). 2011 Cordón Caulle eruption The eruption sequence began with a swarm of volcanotectonic earthquakes detected under the volcanic complex on 27 April 2011 (OVDAS-SERNAGEOMIN, 2011) These earthquakes continued to increase in magnitude and frequency until June 4th when the eruption sequence began with a series of Plinian phases (Schipper et al 2013). Prior to 2011, the last eruption from this centre was in May 1960, 38 h after the main shock of a M9.5 earthquake in Valdivia, Chile (Smithsonian 2014)

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