Markarfljót outwash plain and Öræfajökull
This webpage is also available in Icelandic.
Introduction
The present project belongs to Gosvá, a national collaborative research programme on the assessment of volcanic hazard risks in Iceland led by the Icelandic Meteorological Office (IMO). The programme's steering committee is composed of representatives from IMO, the Institute of Earth Sciences (IES, University of Iceland), the Department of Civil Protection and Emergency Management of the National Commissioner of the Icelandic Police, the Soil Conservation Service of Iceland, and the Icelandic Road and Coastal Administration.
In the Markarfljót outwash plain, the project can be seen as a continuation of the extensive effort dedicated to the assessment of floods caused by eruptions of Katla (the volcano underlying Mýrdalsjökull) and Eyjafjallajökull performed in the years 2002–2005 (Guðmundsson and Gylfason, 2005). In the Öræfi district, this project is the first attempt to assess together the magnitude and impact of jökulhlaups on the inhabited slopes of Öræfajökull Volcano, situated west and south from the caldera.
Both the magnitude of volcanogenic floods and their impact were investigated in the project. Potential adverse consequences received particular attention, with the present project being the first attempt in Iceland to systematically map flood-damage potential as well as spatio-temporal patterns in population exposure. As regards the magnitude of floods, flood timings and routing, the methodologies set out in previous Katla and Eyjafjallajökull hazard assessments were applied (Guðmundsson and Gylfason, 2005).
The project was funded mainly by the National Avalanche and Landslide Fund, with additional financial contributions from the Icelandic Road and Coastal Administration and the National Power Company.
Published material
Under the link below, each of the chapters can be downloaded or short summaries read.
Due to the importance of international cooperation on volcanic risk research, the main deliverable of the project had to be an English-written publication. An Icelandic summary is in progress where the main outcomes of the project will be made available to the local readership. Release of the Icelandic version is scheduled in March/April 2016.
Downloadable material:
Full text (pdf 23 Mb)
Front matter (pdf 180 Kb)
Chapter I. Volcanogenic floods in Iceland: An exploration of hazards and risks (pdf 1.06 Mb)
Pages 7–16
Emmanuel Pagneux, Sigrún Karlsdóttir, Magnús T. Gudmundsson, Matthew J. Roberts og Víðir Reynisson
The background, goals and methodological framework of the project are introduced, in addition to highlighting the findings of subsequent chapters. The chapter concludes with a series of recommendations, based on the overall conclusions of the project. Chapter 1 is an ideal starting point for a quick overview of the project.
Chapter II. Öræfajökull Volcano: Geology and historical floods (pdf 5.43 Mb)
Pages 17–44
Matthew J. Roberts og Magnús T. Gudmundsson
Short summary
Despite the documented severity and lasting geomorphic imprint of the 1362 and 1727 jökulhlaups from Öræfajökull, there is scant information about the routing and extent of these floods. Using field observations, aerial photographs, and modern-day analogues, the goal of this chapter is to constrain the duration, extent, composition, and maximum discharge of the 1362 and 1727 jökulhlaups. It is proposed that floodwater draining from the caldera region would have broken through the ice surface at ~1,500 m elevation. Consequently, supraglacial outbursts of floodwater would have dominated the onset of both jökulhlaups. Geomorphological evidence suggests that jökulhlaups in 1727 reached 4x104 m3/s at Kotá and that 1362 events had substantially higher discharge. The findings of this chapter provide constraints for estimating the melting potential of Öræfajökull eruptions; they are also pertinent to the simulation of volcanogenic floods from Öræfajökull. Furthermore, insights into flood extent, floodwater composition, and the prevalence of ice blocks provides an empirical basis for the rating of flood hazards in the Öræfi region.
Chapter III. Öræfajökull Volcano: Eruption melting scenarios (pdf 3.33 Mb)
Pages 45–72
Magnús T. Gudmundsson, Þórdís Högnadóttir og Eyjólfur Magnússon
Short summary
The potential for ice melting during eruptions in Öræfajökull is assessed using calorimetric estimates of melting for given eruption rates constrained by empirical data from eruptions and considerations of the efficiency of the melting process. Three main types of scenarios are considered for catchments between Svínafellsjökull in the west to Kvíárjökull in the east: (1) A large caldera eruption; (2) a flank eruption on a radial fissure; and (3) the melting from pyroclastic density currents (PDCs). The onset and propagation times of floods arising from subglacial eruptions in Öræfajökull are estimated as being 15-45 minutes from the onset of eruption until a flood starts propagating down the steep flanks. The discharge of jökulhlaups caused by basaltic flank eruptions is considered to be 3,000-6,000 m3/s, a basaltic fissure eruption within the caldera as <20,000 m3/s, and a major explosive caldera eruption, such as the 1362 CE eruption of Öræfajökull, could result in flooding exceeding 200,000 m3/s. Jökulhlaups arising from PDCs may reach 4,000-17,000 m3/s.
Chapter IV. Öræfajökull Volcano: Numerical simulations of eruption-induced jökulhlaups using the SAMOS flow model (pdf 5.89 Mb)
Pages 73–100
Ásdís Helgadóttir, Emmanuel Pagneux, Matthew J. Roberts, Esther H. Jensen og Eiríkur Gíslason
Short summary
Regions around Öræfajökull Volcano that would be liable to flooding during a subglacial eruption are identified. Jökulhlaups are simulated as instant release waves over the ice surface using the SAMOS 2D avalanche model, using estimates of the magnitude of historical jökulhlaups in the region. Simulations are made for jökulhlaups caused by a caldera eruption, flank eruptions, and pyroclastic density currents. Because of the wide range of likely flow rheologies, three Manning's n values are assessed: 0.05, 0.1, and 0.15 s/m1/3. Results indicate that a large part of the lowland between the rivers Skaftafellsá and Breiðá (350 km2) is susceptible to flooding because of jökulhlaups descending the western and southern slopes of Öræfajökull. Characterised by average flow velocities in excess of 20 m/s on the slopes the volcano, the jökulhlaups are quick to hit the lowlands once floodwater has reached the glacier's surface — in as little as ~5 minutes at peak discharge.
Chapter V. Öræfi district and Markarfljót outwash plain: Rating of flood hazards (pdf 2.35 Mb)
Pages 101–122
Emmanuel Pagneux og Matthew J. Roberts
Short summary
A semi-quantitative, damage-oriented method for the rating of flood hazards in the Markarfljót outwash plain and the Öræfi district is presented. The presence of life-threatening debris and the temperature of floodwater are considered, along with depth of flooding and flow velocities; these factors take into account the unique nature of volcanogenic floods. Flood-hazard zones are designated accordingly. An application of the method to the two study areas indicates a potential for significant direct economic damage and fatalities: due, in particular, to excessive flood depths and flow velocities, jökulhlaups can be lethal to anybody and cause complete destruction or unrepairable damage to dwellings and outbuildings almost anywhere in sectors at risk of flooding. As a first approximation of damage potential of volcanogenic floods in the two areas, the results should be considered carefully by the local and national authorities for planning and emergency evacuation purposes.
Chapter VI. Öræfi district and Markarfljót outwash plain: Spatio-temporal patterns in population exposure to volcanogenic floods (pdf 2.75 Mb)
Pages 123–140
Emmanuel Pagneux
Short summary
A spatio-temporal exploration of population exposure is performed in the Markarfljót outwash plain and in the Öræfi district. An inventory of the populations exposed to floods is made for overnight conditions using daily overnight estimates weighted with road traffic data as an indicator. The main objective of the study is to provide the authorities with a realistic estimate, at different periods of the year and at particular locations within the two studied areas, of the likely number of residents and guests potentially in the path of a flood or those that would be stranded due to flooding. In the Markarfljót outwash plain, the results indicate that more than one thousand lives would be in jeopardy if the largest of the potential floods assessed were to happen without warning and evacuation, with a further 600 people being isolated due to partial destruction of the road network; In Öræfi, up to 130 lives could be lost and 240–250 people isolated.
Chapter VII. Öræfajökull: Evacuation time modelling of areas prone to volcanogenic floods (pdf 2.96 Mb)
Pages 141–164
Emmanuel Pagneux
Short summary
A model of evacuation routes and timing for areas exposed to floods due to eruptive activity of Öræfajökull Volcano is presented. Estimates of evacuation times are made at the onset of a volcanic eruption originating in the caldera or on the flanks of the volcano, and at the onset of pyroclastic density currents. The aim of the study is to provide the authorities with critical baseline estimates for the development of an effective flood evacuation plan. Results of the modelling suggest that areas at risk of flooding are unlikely to be successfully evacuated once an eruption has started: the only safe route for evacuation can be flooded at multiple locations within 20–30 minutes of the onset of a volcanic eruption in the caldera or on the flanks, and within 15–25 minutes at onset of a pyroclastic density current. In optimal weather conditions, a full evacuation cannot be completed in less than 30–35 minutes.
Recommended citation for individual chapters (example):
Roberts, M. J., & Gudmundsson, M. T. (2015). Öræfajökull Volcano: Geology and historical floods. In E. Pagneux, M. T. Gudmundsson, S. Karlsdóttir, & M. J. Roberts (Eds.), Volcanogenic floods in Iceland: An assessment of hazards and risks at Öræfajökull and on the Markarfljót outwash plain (pp. 17–44). Reykjavík: IMO, IES-UI, NCIP-DCPEM.
