Jökull - 01.01.2021, Page 14

Larsen et al.
Figure 9. The jökulhlaup routes (blue) on October 12, 1918. The darker shade indicates areas flooded in both
phases. The meltwater of the first phase covered a much larger area than that of the second phase, which was
mostly confined to the western part of Mýrdalssandur. The second phase carried much more ice and probably
more sediment. Most of the damage to property (Sveinsson 1919) was caused by the first phase. Jökulhlaup
routes are based on eyewitness descriptions (see main text) and aerial photographs from 1945 and 1946 (Land-
mælingar Íslands). Base map topography is based on ArcticDEM (Porter et al., 2018) and glacier topography
on Lidar data (Jóhannesson et al., 2013). – Leiðir jökulhlaupsins (blátt) 12. október 1918. Hlaupið skiptist í tvo
þætti, dekkri liturinn sýnir svæði sem hlaupið fór um í báðum þáttum. Í fyrri þætti hlaupsins fór bræðsluvatn
um miklu stærra svæði en í þeim síðari sem var að mestu takmarkaður við vesturhluta Mýrdalssands en flutti
með sér miklu meiri ís og gosefni. Mest tjón varð í fyrri þætti hlaupsins (Sveinsson 1919). Hlaupleiðir eru
samkvæmt lýsingum sjónarvotta (sjá megintexta) og loftmyndum frá 1945 og 1946. Landslag skv. ArcticDEM
nema jökulyfirborð sem er skv Lidar mælingum (Porter o.fl., 2018; Tómas Jóhannesson o.fl., 2013).
Northern fork: Another arm of the jökulhlaup flowed
towards east into the rivers Leirá, Hólmsá, Skálm,
Kælirar and Kúðafljót. Noise from this flood could be
heard 1.5–2 hours before it was seen. About 15 km
east of the edge of Kötlujökull a group of farmers
from Álftaver was waiting at a sheep pen on the north
bank of the Skálm river for their farm hands that were
herding sheep to the pen. Between 1 and 1:30 PM the
farmers noticed an unusual humming sound coming
from the west. The sound gradually grew louder and
12 JÖKULL No. 71, 2021