Jökull - 01.12.2006, Blaðsíða 9

Avalanches in coastal towns in Iceland
2001-2002). There are three main evacuation levels
(Magnússon, 1996):
Evacuation level 1: An area where avalanches
have occurred following moderate snow accumula-
tion. The extent of the evacuation area may be smaller
than indicated by the avalanche history, where ex-
treme conditions are included. Frequent evacuation
of homes can be expected.
Evacuation level 2: An area which is predominantly
determined by known avalanches and topographic
conditions that are similar to known avalanche paths.
Avalanche hazard is associated with heavy accumula-
tion of snow. The area will be evacuated during im-
pending weather conditions which are known to im-
pose a serious threat of avalanches.
Evacuation level 3: An area which is considered
threatened by catastrophic avalanches that need not
be included in the known avalanche history, but are
considered possible; meteorological conditions with
extreme snow accumulation and extreme winds. Ar-
eas threatened during extremely rare meteorological
conditions are included.
Evacuation level 2 1/2: In Neskaupstaður, level 3
reaches down to the ocean in an extensive part of the
town. Furthermore, the starting zones of the vari-
ous avalanche paths have similar aspects resulting in
avalanche hazard a large area at the same time. To
be able to evacuate smaller parts of the town, an in-
termediate level between levels 2 and 3 was defined.
Although permanent avalanche protection has
been constructed in some towns, level 3 evacuation
plans are still in effect, as the risk can never be elimi-
nated completely.
Where the hazard is mainly due to wet avalanches
or slush flows, evacuation is usually not predefined,
but partly based on a subjective evaluation of the situ-
ation on each occation.
WEATHER LEADING TO AVALANCHES
IN THE TOWNS AT RISK
A general description of weather related to avalanches
for each town is given in the evacuation plans
(Veðurstofa Íslands, 1997). The weather description is
based on the studies mentioned previously in this pa-
per, as well as unpublished studies relating local con-
ditions and particular weather characteristics. Details
on avalanche paths and weather characteristics prior
to avalanches in individual towns are summarized in
Tables 3–17. The evacuation levels are included to
show the scale of the danger in the zone below the
relevant source area. A short overview is given for
each town.
Ólafsvík
The two known avalanche events in Ólafsvík (Figure
A1) occurred when relatively large amounts of snow
had accumulated during winds from S and SE.
Patreksfjörður
The most severe avalanche hazard in Patreksfjörður
(Figure A2), especially at Vatneyri, seems to be re-
lated to intense snowfall and/or snowdrift in easterly
wind directions, i.e. from 60◦ to 130◦. This is asso-
ciated with frontal zones moving slowly northwards
over the area. Intensive rain and/or melting can cause
serious slush flow danger.
Bíldudalur
During most winters there is not much snow accumu-
lation on the slopes above Bíldudalur (Figure A3). Al-
though rare, avalanche hazard may develop along the
mountainside above the town, during intense snowfall
and persistent westerly winds. Wet avalanches, slush
flows, landslides and water floods are more likely than
dry avalanches. Intensive rain or sudden thawing can
create a severe avalanche danger in Bíldudalur.
Tálknafjörður
The town is mainly threatened by slush and water
flows, caused by intense rain or thawing. Evacua-
tions due to risk from dry avalanches were not consid-
ered necessary and there are only a few recent mapped
avalanches. Predefined evacuation plans are designed
with respect to flooding along two gullies.
Northern part of Vestfirðir: Suðureyri, Flateyri,
Súðavík, Ísafjörður, Hnífsdalur and Bolungarvík
The most severe avalanche hazard in Northern-
Vestfirðir (Figures A4-A8) is related to snowfall with
strong winds from northerly directions, mainly N and
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