Skaftá: a glacial outburst flood in progress
Within the past 24 hours, the level of the Skaftá river at Sveinstindur has risen. Additionally electrical conductivity readings from the same location have increased.
These observations signify that a glacial outburstflood (jökulhlaup) is in progress. It is likely that the flood originated from the western Skaftá ice cauldron, which last drained in September 2012; however this is unconfirmed until visual observations are made.The discharge of Skaftá at Sveinstindur is presently 370 m³/s.
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 Tungnárjökull, 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 map below shows the area. Flood monitoring at Sveinstindur is marked by a red pointer.
The graph below shows the discharge of river Eldvatn (vhm 328) for the past 17 months. Eldvatn is the main channel for floods in Skaftá. The ongoing outburst flood is small, given that in enormous floods the discharge can amount to 900 m³/s. However, precaution is needed.