Measurements on Mýrdalsjökull ice cap, which covers the Katla volcano, south Iceland, indicate that it is probable that a glacial flood may happen in the next few weeks. The event expected is not major, but could temporarily close dirt-roads off Road no. 1 on both sides of the river and cause hydrogen sulphide (H2S) pollution. This is based on survey work by scientists from the Institute of Earth Sciences at the University of Iceland on Mýrdalsjökull. The findings from their research shows that the accumulation of meltwater in the ice-cauldrons in Mýrdalsjökull is close to triggering a glacial outburst flood, that may happen in river Múlakvísl within the next days or weeks. The flood will probably be similar in size to the flood in 2017 but might possibly be bigger and it might even inundate part of Road no. 1 for a period of time.
In recent years there have been yearly floods, glacial outburst floods, in the river Múlakvísl in South Iceland. The river Múlakvísl runs from Kötlujökull, an outlet glacier from the glacier Mýrdalsjökull, and the bridge over the river on Road 1 is 8 km east of the village Vík. These yearly floods have in general coincided with maximal glacial melt or ablation during or just after mid-summer. In 2011 a flood occurred which destroyed the bridge across Múlakvísl on Road 1. In 2017 another sizeable flood occurred which was about half of the 2011 flood in volume and approximately 20% of the 2011 peak discharge. The flood in 2017 did not result in damage to infrastructure. Because of the geothermal origin of some of the floodwater large amounts of hydrogen sulphide gas were released from the floodwater.
Mýrdalsjökull has a large number of ice-cauldrons which are formed when geothermal activity melts the glacial ice. The meltwater collects in the cauldrons and surface meltwater to an extent seeps through the glacier into the water body at the base of the glacier. When enough meltwater has accumulated in the cauldrons this causes a glacial outburst flood.
It should also be noted that a glacial outburst flood from Kötlujökull may also find its way partly into the river Skálm.
Travel service providers operating on or near Mýrdalsjökull have been notified of the situation. They will be informed of how to respond in the event of a flood. Scientists believe that there will be a measurable short term lead-up to the flood which may be measured. For this purpose a GPS measuring device will be deployed in one of the cauldrons on Mýrdalsjökull in the coming days.
At present there is no need for road closures or limitations to traffic. The situation is being monitored closely and appropriate measures will be taken when the need arises.
Hazards associated with glacial outburst floods in Múlakvísl:
- Floodwater can close off the track from Road no. 1 to Kötlujökull which runs along the western flank of the mountain Hafursey.
- Floodwater can flow over road no. 1 and stop traffic or even breach the road.
- Floodwater may close off the road to Þakgil.
- Hydrogen sulphide gas (H2S) can be released in amounts sufficient to harm mucous membranes in people’s eyes and respiratory tract.
- Pay attention to and heed road closures and evacuation instructions.
- Stay away from the vicinity of flooding rivers.
- Stay away from areas where hydrogen sulphide gas may accumulate. These are areas close to the river and low lying areas in the vicinity. Do not stop on the bridges across the rivers Múlakvísl or Skálm. Do not stop within 500 meters of these bridges.