Geoscience Reference
In-Depth Information
Flood simulation models based on data from prehistoric jökulhlaup were used to
identify peak discharge and temporal and spatial distribution of a possible catastrophic
jökulhlaup fl ooding from the Entujökull catchment down the Markarfl jót (Hólm and
Kjaran, 2005). This populated farming region forms part of the Rangávallasysla mu-
nicipality. The models show that a catastrophic jökulhlaup with a peak discharge of
300,000 m
3
s
−1
would reach its maximum within 2 hr, fl ooding to a depth of up to 15
m, at the uppermost farms in Fljótshlío and up to 10 m in Vestur-Eyjafjöll. However,
many of the farmhouses in these communities are elevated above the fl oodplain. In
contrast, the roads leading up to these farms parallel the Markarfl jót and some sec-
tions of these roads are positioned at similar base heights to the river channel. Dykes
approximately 2 m in height have been constructed to protect the roads but these fl and
mitigation structures were not built to withstand a catastrophic jökulhlaup. Within
3 hr Highway 1 would be inundated and the entire outwash plain surrounding the
Markarfl jót would be fl ooded within 10 hr. With a maximum fl ood depth of up to 2 m,
low lying regions could remain submerged for over 24 hr.
In view of the potential future hazard presented by jökulhlaup, the ICPorganization
developed regional evacuation strategies based on a worst case scenario as described
in the report edited by Guomundsson and Gylfason (2005). This report and consequent
strategies were the culmination of a multidisciplinary investigation into the physi-
cal threat of jökulhlaup produced from a Katla eruption. It did not however, include
research from a societal aspect. Researchers argue that a collaboration between the
physical and social sciences is a key step toward achieving a greater understanding of
the consequences of volcanic hazards (e.g. Johnston et al., 1999). Following the inves-
tigation communication sessions were held with residents from communities located
within the hazard zone in Rangávallasysla: Vestur-Eyjafjöll, Fljótshlíd, Landeyjar, and
Pykkvibær. These consisted of information meetings in 2005 and 2006 regarding the
possibility of a future Katla eruption and the proposed evacuation plan for a jökulhlaup
hazard. During these meetings residents were informed that they could collect an
evacuation and hazard information sign from local police (Figure 2) (K. Porkelsson,
personal communication, 2006).
If an eruption is imminent residents would be notifi ed via a text message to their
mobile phone. If residents do not have a registered mobile phone number a recorded
message would call through to their landline. Upon receiving this message residents
have 30 min to prepare to evacuate. However, if an eruption occurs without precursory
activity, residents will be instructed to evacuate immediately. Before leaving, they are
required to hang the evacuation sign outside their house to indicate that they have left.
Certain residents in each region have volunteered to “sweep” their local area to ensure
their neighbors have left for the evacuation centers (EC) located in Hella, Hvolsvöllur,
and Skógar. In order to reach these centers, some residents must evacuate via the roads
that parallel the Markarfl jót and along Highway 1.
To test the proposed evacuation plan the ICP conducted a full scale evacuation
exercise on March 26, 2006 in Rangávallasysla. Approximately 1,200 residents live
within the hazard zone (K. Porkelsson, personal communication, 2006) and for the
purpose of fully testing the evacuation plan residents were not informed of the timing
of the eruption scenario. Instead residents were instructed to go about their business as
