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SUMMARY
Ice-dammed lakes at Kjölur and
catastrophic floods in the Hvítá
river, Southern Iceland
by
Haukur Tómasson
National Energy Authority
Grensásvegur 9
IS-108 REYKJAVÍK
Iceland
The author describes the geomorphologica!
evidence for catastrophic floods occuring near
the end of the last glaciation in the basin of
the Hvítá river in Southem Iceland. Shore-
lines from glacially dammed lakes are on
Kjölur, the upper reaches of the Hvítá basin.
These two features are connected in a fairly
detailed picture of altemating accumulation
up to 30 km3 of water, and release of this
water in enormous floods, the biggest one
with a peak flow over 300 000 m3/s.
Water escaped from the ice-dammed lake
at Kjölur over 3 different passes. The first
pass led the water towards Blanda in Northem
Iceland, the second over Bláfellsháls to Hvítá
and the third along the present course of Hvítá.
The third flood channel carried the real
catastrophic floods but the others also carried
substantial floods and created obvious erosion
phenomena. The catastrophic flood channels
covered an area many hundreds of km square,
with erosion phenomena most obvious, but
exstensive deposition also occurred in the low
gradient areas of the flood channel. The most
spectacular erosional feature is the Gullfoss
canyon, which was largely eroded in these
floods. This happened a few hundred years
after the so-called Búði stage, the last major
advance of the ice-age glaciers in Iceland.
These events tie together the finiglacial
history of ice retreat in Southern and Northern
Iceland.
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