Glacial Outburst Flood Has Begun in Skaftá River

A glacial outburst flood has begun in Skaftá river in South Iceland, the Icelandic Met Office reports. The water level and flow rate in the river began to increase last night and increased electrical conductivity was also measured. Rangers in Hólaskjól also reported smelling sulphur in the area. The National Police Commissioner and Department of Civil Protection have issued an uncertainty phase due to the event.

The last glacial outburst flood in Skaftá occurred two years ago, in September 2021. Floods in Skaftá are sourced from two ice cauldrons beneath Vatnajökull glacier which usually burst one at a time, but it is possible that this flood is sourced by both the western and eastern cauldrons, according to the Met Office. The 2021 glacial outburst flood was sourced by both cauldrons.

Risk of floods and gas poisoning

There are several hazards associated with such natural events. Firstly, flood conditions are expected in Skaftá river over the next two to three days and some flooding of roads near the river is possible. Secondly, hydrogen sulphide is released from the floodwater as it drains from the Vatnajökull ice cap. The gas is particularly potent at the ice margin, where it can reach poisonous levels of concentration. Travellers are advised to stay away from the edges of Skaftárjökull, Tungnaárjökull, and Síðujökull, where floodwater could burst through the surface. Lastly, travellers on Vatnajökull should stay away from the region, as crevasses will develop rapidly around the ice cauldron.

The cauldrons that source the glacial outburst floods in Skaftá drain every two years on average, producing floods of up to 1,500 cubic metres per second.

Skaftá Glacial Outburst Flood to Reach its Peak on Wednesday

A second glacial outburst flood began in the eastern Skaftá ice cauldron under Vatnajökull glacier late Saturday evening, RÚV reports. This flood follows a smaller one that originated in the western Skaftá ice cauldron and is expected to do as much damage to local communities and farmland as the last glacial outburst flood on the Skaftá river in 2018. The Department of Civil Protection is strongly advising that travelers stay away from the area and has raised their emergency response level to Alert Phase.

Floods in Skaftá are sourced from two ice cauldrons, formed due to persistent geothermal activity beneath Vatnajökull. On average, the cauldrons drain every two years, producing floods of up to 1,500 cubic metres per second. When the interval between floods is short, the flood tends to be smaller. The eastern cauldron is responsible for the largest floods. The river has flooded at least 58 times since 1955, with each cauldron usually draining at a two-year interval.

 

Image courtesy of Þuríður Hallgrímsdóttir. Route 1 west of the village of Kirkjubæjarklaustur flooded during the Skaftá glacial outburst flood in 2018

Smaller Flood, Same Damage
Owing to the speed at which the glacial flood began and water level increases in the first twelve hours of the flood, experts believed that the current outburst flood would be as big as the one in 2015, which is the largest such flood on record.

Happily, flood waters have been steadily abating since late Monday evening, leading experts to revise their original predictions. Nevertheless, major and widespread flooding is still a risk in the area. At time of writing, the flow at Eldvatn lake on the Skaftá river was just over 520 m3/s [18,363 ft3/s]. Flooding is expected to reach its peak tomorrow, Wednesday September 8, and waters are expected to continue to flood the region for another day or so after that.

Unfortunately, although the flood itself is expected to be smaller than it was in previous years, experts anticipate that it will do the same level of damage to surrounding settlements and farmland. This is, in part, because recent rains and runoff from the western ice cauldron, which flooded days before, have saturated the ground. As such, flood waters are more likely to spread further than they normally would.

‘We’ll just have to cross our fingers’

Glacial outburst floods are simply an unfortunate but unavoidable part of daily life for people in the area, remarked Skaftá district manager Sandra Brá Jóhannsdóttir in an interview on Tuesday before departing on a Coast Guard surveillance flight to determine what damage the flood has incurred thus far.

Authorities were particularly concerned about the wellbeing of the sheep grazing in the surrounding valleys. Local farmers spent the morning gathering their flocks and moving them to safer pastures in the event that the flood does continue to spread. Thankfully, no significant damage to structures or livestock had been reported at time of writing. “We’ll just have to cross our fingers,” said Sandra Brá. “It’s our hope, first and foremost, that the flooding is at least still at a consistent level and that hopefully, it will start to go down so that there will be less damage that occurred [in the area] in 2018 and 2015.”

The Skaftá glacial outburst flood in 2015 caused damage in the hundreds of millions of ISK (roughly $761,000; €708,000 at the time) and ten farms suffered damage to cultivated land and pasture. In 2018, flood waters covered Route 1, west of Kirkjubæjarklaustur.

See Also: Live Footage of the Skaftá Glacial Outburst Flood

In addition to warning that roadways in the area could quickly become impassable in the coming days, the Department of Civil Defense notes that glacial outburst floods can create hydrogen sulphide pollution, which can cause damage to the mucus membranes in the respitory tract and the eyes. Travelers are strongly advised to stay away from the area, which includes the Skaftárdalur valley near the southern coastal village of Kirkjubærjarklaustur, as well as around the Skaftárjökull, Tungnárjökull, and Síðjökull glaciers.

Larger Flood in Skaftá Imminent as Smaller Flood Subsides

On September 1, a small glacial outburst flood began in Skaftá river from the western Skaftá ice cauldron, which generally produces smaller floods than the eastern one. While the smaller flood is now declining, the Iceland Meteorological Office expects a flood from the eastern cauldron to be starting, which will likely reach the route 1 road along the south coast tonight.

Yesterday, GPS measurements from Vatnajökull glacier showed that the surface of the ice cap over the Eastern-Skaftá cauldron had started to subside. It had dropped by just under 1m [3ft] the 12 hours since the process started but will likely drop by 60-100n [200-330ft] once the cauldron fully drains. That indicates that the glacial meltwater will drain, producing a glacial flood. The last flood from the Eastern-Skaftá cauldron occurred in August 2018.

The latest data suggest that floodwater from the eastern cauldron will reach the hydrological station at Sveinstindur tonight. Based on earlier floods, it will reach its peak just over 30 hours after that. The first signs of the flood are expected to reach lake Eldvatn during the night or early tomorrow morning. Once it does, the river’s flow will steadily increase and likely reach its peak by route 1, late Wednesday night or early Thursday morning.

Initially, the water flows along a 40km [25mi] long tunnel below the glacier and then for 28km [17mi] along Skaftá before it reaches the first hydrological station at Sveinstindur, which will provide data on the increase in water levels. Earlier floods from the Eastern cauldron have reached 3.000 m3/s [105,944 ft3/s] but the last one in 2018 peaked at 2.000 m3/s [70,629 ft3/s]. The current flood from the western cauldron peaked around midnight, September 2 at around 520 m3/s [18,363 ft3/s], and the river currently flows at 412 m3/s [14,549 ft3/s]. Based on experience from earlier floods, the floodwater will reach the first hydrological station today.

Based on the current amount of water in the cauldron, it’s likely that the flood will be of a similar size to the one that occurred in 2018 but water could spread further as last week’s smaller flood has raised the water level in the river.

The Met Office will continue to monitor this event closely.

Possible hazards

Locals and people travelling in the area should be aware of possible hazards and conditions there.

  • In the next few days, Skaftá may overflow roads close to the river.
  • High values of H2S are expected near Skaftárjökull and people are advised to stay at a safe distance from the river and nearby glaciers.
  • Crevasses can form rapidly around the cauldron, so people travelling on Vatnajökull should stay away from the cauldrons and glaciers where floodwater is emerging.

Background information

The Skaftá cauldrons, eastern and western, are located in the western part of the Vatnajökull ice cap where geothermal activity melts the glacier from below and water accumulates beneath them. When the hydrostatic pressure is high enough for the water to lift the ice above it, the cauldron drains, causing a flood. Floods from the eastern cauldron are usually larger than the floods from the western cauldron. This phenomenon was first observed in 1955 and since then 58 floods have occurred. On average floods from each cauldron occur every two years.

The increase in electrical conductivity in the Skaftá river is probably due to steam explosions from the geothermal area beneath the ice cauldron. Steam explosions occur as the geothermal area adjusts to decreased water pressure resulting from the drainage of the cauldron. The explosions increase the amount of dissolved material in the floodwater, which is detectable downstream as conductivity increase in the river.

Glacial Outburst Flood Likely Begun in Skaftá

Electrical conductivity readings from the Skaftá river have increased and water levels by Sveinstindur have increased this morning, signifying that a glacial outburst flood is in progress. It is likely that the flood originated from the western Skaftá ice cauldron which last drained in 2019, although it is not impossible that a flood from the eastern cauldron might follow.

In addition to rising water levels and increased electrical conductivity, the Iceland Meteorological Office has also been notified of sulfuric smell in the area around Skaftá and Hverfisfljót. It is believed that the changes are not due to melting glaciers or rain, but rather that a glacial outburst flood has begun. Data suggests that the flood origin is in the western ice cauldron in the Vatnajökull glacier, which last flooded in September 2019. The western ice cauldron usually produces smaller floods than the eastern one.

The flow of Skaftá by Sveinstindur was around 290 m3/s at noon today but the Met Office doesn’t expect the maximum flow during this flood to surpass 750 m3/s. However, there is a possibility that water drains from the eastern ice cauldron on the heels of the current flood from the western one, as happened in August 2018.

It’s important that everyone who is travelling in the flood area is conscious of the situations that can arise and that travellers are well informed of the situations:

  • Flood conditions are expected in Skaftá over the next two to three days. Some flooding of unpaved roads close to Skaftá is possible.
  • Hydrogen sulphide is released from the floodwater as it drains from the Vatnajökull ice-cap. The gas is particularly potent at the ice margin, where concentrations will reach poisonous levels. Travellers must stay away from the edges of Skaftárjökull, Tungnaárjökull and Síðujökull while the flood occurs.
  • Crevasses will develop rapidly around the ice cauldron, so travellers on Vatnajökull should stay away from the region, including the lower part of Skaftárjökull and Tungnaárjökull, where floodwater could burst through the surface.

Floods in Skaftá are sourced from two ice cauldrons, formed due to persistent geothermal activity beneath Vatnajökull. On average, the cauldrons drain every two years, producing floods of up to 1,500 cubic metres per second. When the interval between floods is short, the flood tends to be smaller. The eastern cauldron is responsible for the largest floods. The river has flooded at least 58 times since 1955, with each cauldron usually draining at a two-year interval.

Skaftá Glacial Flood Ends

The glacial outburst flood that has been taking place along the Skaftá river in South Iceland has mostly ended reports the Icelandic Met Office.

According to an announcement on the Met’s website, “Water discharge in Skaftá is back to normal for this time of year. The Skaftá flood is therefore mostly over.” The announcement emphasizes, however, that both discharge and water height in both the Grenlækur and Tungulækur streams are still high. It’s estimated that these will return to normal levels in a little over a week.

The Icelandic Met Office issued a travel warning about the glacial flood a week ago, and since then, part of Route 1, the Ring Road, had to be closed at Kirkjubæjarklaustur due to rising water levels.

Travelers are reminded to check road conditions at road.is before setting out on their trips.

Route 1 Partially Closed Due to Skaftá Glacial Flood

Route 1, west of Kirkjubæjarklaustur, has been closed due to flooding from the glacial outburst flood in Skaftá river, Vísir reports. The police in South Iceland have reported this, and the Icelandic Met Office issued a general travel advisory on June 3rd.

Ágúst Freyr Bjartmarsson, a foreman at the Icelandic Road and Coastal Administration, said the water is now too deep for cars to pass through, but that it cannot be said for sure when water levels will regress.

A bypass route through Meðallandsvegur is open, which is expected to slow down travellers by around 40 to 60 minutes in total.

The glacial outburst flood has already reached a high point, and it is expected that it will now slowly regress, according to the Icelandic Met Office. The effects of the flood will still be felt in the next days, and it is expected that Skaftá will not experience regular water flow until later in the week.

The fact that both cauldrons of the glacier Skaftárjökull have flooded at the same time is an historical event, as up to this point only one cauldron at a time has activated, Vísir reports.

A sulphur stench has been reported in the region, but the smell can be felt quite far away. The were reports of sulphur in the air in Norway the last time a glacial outburst flood in Skaftá happened, in 2015.

Travellers are advised to visit the website of the Icelandic Road and Coastal Administration for further information, www.road.is, or reach them by telephone in the number 1777.