Avalanse Irlanda

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O R I G I N A L P A P E R

Avalanche risk assessment for mountain roads: a case

study from Iceland

Maria Wastl Johann Stotter Hannes Kleindienst

Received: 24 November 2008 / Accepted: 23 December 2010 / Published online: 6 January 2011 Springer Science+Business Media B.V. 2011

Abstract This paper presents an assessment of the avalanche hazard potential and the

resulting risks on mountain roads for a 38.7-km-long section of road no 76 (Siglu-

fjararvegur) in northern Iceland following a regional scale approach developed in the

Alps. The assessment of the individual avalanche death risk proved applicable to distin-

guish areas of avalanche hazard with a risk above the accepted level, which should be

given priority in following detailed investigations and the planning of possible protective

measures, from road sections where the avalanche death risk is low and accepted accordingto international practice. The cumulative individual and collective avalanche death risks in

the investigated road section provide a comparable measure for assessing the avalanche

hazard both within the Icelandic public road network and on an international scale. The

case study on road no 76 in northern Iceland shows that a standardised regional scale risk-

based approach is practical to determine, analyse and assess the avalanche hazard situation

on mountain roads in Iceland and guarantees comprehensible, reproducible and compa-

rable results as a basis for a sustainable planning of measures.

Keywords Risk assessment Avalanche hazard Mountain roads Iceland

M. Wastl (&)Department of Geography, Institute for Integrated Natural Sciences, Koblenz University,Universitatsstrae 1, 56070 Koblenz, Germanye-mail: [email protected]

URL: http://www.uni-koblenz-landau.de/koblenz/fb3/ifin/geographie

J. StotterInstitute of Geography, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria

H. KleindienstGRID-IT Gesellschaft fur angewandte Geoinformatik mbH, Technikerstrae 21a,6020 Innsbruck, Austria

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1 Background and aim of the investigation

While the management of avalanche hazards in settlements follows operational stand-

ardised procedures in Iceland (see e.g. Arnalds et al. 2004; Johannesson 2004; Jonasson

et al. 1999; Jonsson 2002; http://www.vedur.is/ofanflod/log/), there are no comparableapproaches for a systematic survey and assessment of the avalanche hazard situation and a

sustainable planning of measures for roads. This investigation presents a regional scale

assessment of the avalanche hazard potential and its related risks on mountain roads for a

case study in northern Iceland.

The total length of the public road network in Iceland is ca. 13,000 km (http://www.

vegagerdin.is/vefur2.nsf/Files/VegskraLysing/$file/Vegaskr%C3%A1_lei%C3%B0arl%C3%

BDsing_01-03-2010.pdf), mostly low-volume roads outside built-up areas. About

10,500 km of these roads are open all year. Substantial parts of the Icelandic public road

network e.g. in central northern Iceland, north-western and eastern Iceland lie in alpine

mountain areas and are affected by avalanches. Though the resulting road maintenancecosts are considerable, there is no general overview of the avalanche hazard situation up to

now. (Fig. 1)

The aim of the investigation is to describe and assess the generalised avalanche hazard

situation and its related risks on roads outside built-up areas following a regional scale

approach.

The approach is calibrated by a detailed investigation into the 38.7-km-long section of

road no 76 (Siglufjararvegur) from Siglufjorur to Straumnes in northern Iceland (Fig. 2).

The results are documented in maps indicating the avalanche hazard potential for specific

road sections, a report with the risk assessment and recommendations and an informationsystem, all together providing a basis for detailed planning.

To guarantee that investigations following the developed approach are feasible and

affordable for all rural roads in Iceland and reduce time-consuming and expensive field-

work to a minimum, the investigation needs to be mainly based on already existing data

most of which are available at the Icelandic Road Administration (Vegagerin), the Ice-

landic Meteorological Office (Veurstofa Islands) and the National Land Survey of Iceland

(Landmlingar Islands).

Fig. 1 Road no 76 in northern Iceland

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http://www.vedur.is/ofanflod/log/http://www.vegagerdin.is/vefur2.nsf/Files/VegskraLysing/$file/Vegaskr%C3%A1_lei%C3%B0arl%C3%BDsing_01-03-2010.pdfhttp://www.vegagerdin.is/vefur2.nsf/Files/VegskraLysing/$file/Vegaskr%C3%A1_lei%C3%B0arl%C3%BDsing_01-03-2010.pdfhttp://www.vegagerdin.is/vefur2.nsf/Files/VegskraLysing/$file/Vegaskr%C3%A1_lei%C3%B0arl%C3%BDsing_01-03-2010.pdfhttp://www.vegagerdin.is/vefur2.nsf/Files/VegskraLysing/$file/Vegaskr%C3%A1_lei%C3%B0arl%C3%BDsing_01-03-2010.pdfhttp://www.vegagerdin.is/vefur2.nsf/Files/VegskraLysing/$file/Vegaskr%C3%A1_lei%C3%B0arl%C3%BDsing_01-03-2010.pdfhttp://www.vegagerdin.is/vefur2.nsf/Files/VegskraLysing/$file/Vegaskr%C3%A1_lei%C3%B0arl%C3%BDsing_01-03-2010.pdfhttp://www.vedur.is/ofanflod/log/


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This paper describes the practical application of a regional scale risk-based avalanche

hazard assessment for mountain roads in Iceland meeting these preconditions.

2 Investigated road section

Road no 76 is classified as a highway and tarred. The mean traffic densities along the

investigated section of the road are between ca. 250 and 370 cars per day in the annual

average, with ca. 400540 cars per day during the summer (June to September) and ca.

150270 cars per day during the winter months (December to March), based on the census

from 2008 (http://www.vegagerdin.is/vefur2.nsf/Files/umferd_thjod_2008_skyrsla/$file/

Umfer%C3%B0_%C3%A1_%C3%BEj%C3%B3%C3%B0vegum_2008.pdf).

Figure 2 shows the investigated section of road no 76. For the assessment of the ava-

lanche hazard situation, it was divided into six subsections (road sections 911941 in the

map).

Fig. 2 Investigated section of road no 76 from Siglufjorur to Straumnes. The orange line marks theboundary of the catchments of the streams crossing the road, the blue dots indicate the meteorologicalstations used in this investigation

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3 Avalanche hazard assessment

3.1 Method

Due to the specifications stated in the objectives (see Sect. 1) and the requirements of theregional scale and the resulting detail in the determination of areas affected by avalanche

hazards, an approach was adopted which had been developed in the Eastern Alps in recent

years (see http://bfw.ac.at/iym/pdf/ziegner.pdf; http://www.tirol.gv.at/fileadmin/www.tirol.

gv.at/themen/umwelt/wald/schutzwald/downloads/endber-kurzfass-06-04-og.pdf). In addi-

tion to the natural hazard zone maps on the planning level with scales C1:10,000, a

preceding regional scale overview level with scales B1:25,000 has been introduced in

Austria, Germany and Italy. This approach aims at increasing the efficiency and effec-

tiveness in natural hazard management by maximising the use of existing data (maps,

reports, scientific investigations, etc.) and reducing time-consuming and expensive field-

work to a minimum. Models which are specially adapted to the requirements of a regionalscale are applied to provide comprehensible, reproducible and comparable results, which

help to assign priorities in the planning of measures.

3.2 Data bases

To guarantee that the developed approach can be applied to all classified roads in Iceland,

the investigation was mainly based on already existing data most of which are available at

the offices of

the Icelandic Road Administration, i.e.(1) digital colour orthophotos with a resolution of 0.5 m and

(2) digital 5 m contour lines

for the areas around the road.

The mosaic of the digital colour orthophotos provides the background for 3D-views of

the investigated road sections and the detailed maps of the results (see Sect. 3.3).

the Icelandic Meteorological Office, i.e.

meteorological data of stations in or close to the investigation area: Sauanesviti

(66

11

0

N, 18

57

0

W, 30 m a.s.l.), Skeisfoss (66

00

0

N, 19

01

0

W, 84 m a.s.l.) andSiglunes (66120N, 18510W, 8 m a.s.l.) (see Fig. 2).

the National Land Survey of Iceland, i.e.

(1) topographic maps Iceland-Island 1:50,000 and

(2) black and white aerial photographs.

Stereo pairs of these aerial photographs provided the basis for mapping potential

starting areas of avalanches above the investigated section of road no 76 before going into

the field (see Sect. 3.3).

Orthophotos of a resolution of 1.0 m were produced from the black and white aerial

photographs by means of the software PCI OrthoEngine.

For this investigation, a digital terrain model (DTM) was produced using ARC-GIS. It is

based on the digitised contour lines (interval 20 m) and geodetic points of the 1:50,000

maps for the whole investigation area and the digital 5-m contour lines provided by the

Icelandic Road Administration for parts of the area along the investigated section of road

no 76. The elevation data of the 5-m contours were used where available. This improved

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DTM provided the basis for modelling the investigated processes, which guarantees a high

quality of the modelling results for the areas around the road.

In addition, these data studies on the general geological background (Gumundsson

et al. 2001; Hafliason 1982) as well as previously made reports on the investigated road

section (Jarfristofa AGVST, BAH Ragjof 1999; Smundsson et al. 2004) wereavailable for this assessment. The latter, however, concentrate on an area of active sagging

and do not provide information on the avalanche hazard situation.

3.3 Applied model

Objective of the modelling part of the investigation was the determination and outline of

areas affected by avalanche processes for the section of road no 76 from Siglufjorur to

Straumnes.

Potential starting areas of avalanches were mapped based on stereo pairs of the aerial

photographs (see Sect. 3.2) for the areas above the road. These maps were checked andcompleted in the field. Areas of active avalanche processes could be identified by damage

to the vegetation, missing sods or eroded patches of soil. In some cases, remains of snow or

debris left by avalanches could be found. Boulders deposited by the avalanches were

mapped as indicators for the extents of the accumulation areas. Additional information on

the run-out distance was provided by ruins of farm buildings which had been destroyed by

an avalanche (Engidalur). The ground-truthed maps were digitised and transferred to a GIS

dataset.

The starting areas were checked and partly expanded by means of a disposition model

using functionalities of geographical information systems. On the regional scale, the mostimportant criterion for the determination of the starting areas is the slope of the terrain.

Potential starting lines of avalanches are defined as the upper boundaries of areas with

slopes between 28 and 50.

The resulting dataset of potential avalanche starting areas was the basis for modelling

the accumulation areas using the model GRID-aval.

The avalanche model GRID-aval (Grid-based Trajectory Avalanche Model) is a two-

dimensional model to calculate the run-out distance of flow avalanches on a regional scale

(see Stotter et al. 2006). It is based on the approach of Lied and Bakkehi ( 1980) and

determines the maximum run-out distance in a topographic-statistical way. The model

describes the run-out distance of an avalanche by means of an angle a which is a functionof the angle between the starting point and the point at which the avalanche track reaches

an angle of 10.

The model calculates the run-out distance of an avalanche starting from a given line

by means of an estimated slope with the angle a. This estimated slope describes the loss

of energy of the avalanche during the flow process. Thus, the difference between the real

slope of the terrain surface and the estimated slope gives the corresponding kinetic

energy, which, in a following step, can be used as input data for the modelling of the

flow paths. The angle a is determined on the basis of a statistical analysis of known

avalanche events.For this assessment, a was derived from the statistical analysis of 45 avalanche events

in Iceland by Johannesson (1998).This investigation gives a mean value for a of 23.62

with a standard deviation of 3.19 (a = 23.62, r = 3.19, n = 45). The minimum value

for a in the Siglufjorur area (n = 7) is 21. On this basis, an estimated slope of 23.62

(mean) and a lower limit of 20.43 (mean minus one standard deviation) were used in

the calculations.

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The avalanche track is determined by means of a vector-orientated model on the basis of

orientation and slope data from the digital terrain model. The influence of topography on

the calculated avalanche tracks is determined by a weighting factor (topoweight). A

topoweight value of 1 stands for a motion close to that of a ball while a very high value

represents the motion characteristics of water. A further model parameter (widening)defines the lateral extension of the avalanche from the calculated tracks. In model calcu-

lations made so far, topoweight values between 5 and 7 and a widening of 0.005 have given

good results. The output of this modelling is a sequence of points in three-dimensional

coordinates.

The modelled avalanche accumulation areas were printed out against the background of

the topographic maps and the colour orthophotos (see Sect. 3.2) and compared with the

extents of the avalanche accumulation areas mapped in the field. These checked and

corrected data provided the basis for assessing the avalanche hazard for the investigated

road section.

Based on the findings in the field and the modelling results, two avalanche hazard levelsare distinguished:

(1) Avalanche hazard level 1 is based on an estimated slope of 23.62, which is the

statistical mean of the analysis of 45 avalanche events in Iceland by Johannesson

(1998).

Areas of avalanche hazard level 1 can be reached by avalanches under unfavourable

conditions.

(2) Avalanche hazard level 2 is based on an estimated slope of 20.43, which is the mean

minus one standard deviation in the analysis by Johannesson (1998), and indicatesareas that can be reached by avalanches under extremely unfavourable conditions

(worst case assumption).

There are, however, no records of avalanches for the investigated road which could

provide empirical evidence for the assumptions on these avalanche hazard levels.

Figure 3 shows an example of the modelled avalanche tracks and the extent of the

accumulation areas, which are the outer boundaries of all cells reached by the avalanche

tracks, for avalanche hazard levels 1 and 2, respectively.

While the validation of run-out distances is not possible due to the limitations of the

available data, the avalanche hazard levels reflect the topographic situation of the affectedroad sections, where the slopes with the avalanche tracks extend down to the coastline (see

Fig. 1). Thus, all modelled avalanche tracks that reach or cross the road cause an avalanche

hazard in these areas irrespective of their exact run-out distances.

3.4 Results

In the investigated part of road no 76 between Siglufjorur and Straumnes, there are 18

areas of avalanche hazard level 1 (see Table 1) and 25 areas of avalanche hazard level 2

(see Table 2).

The areas of avalanche hazard level 1 lie between Siglufjorur and km 13.32, i.e. in

road sections 911, 912 and 921 (see Fig. 2). Altogether, 6.81 km of these northern three

sections can be reached by avalanches under unfavourable conditions (Figs. 4, 5, 6).

Especially, road sections 911 and 912 are almost entirely areas of avalanche hazard level 1

with 14 avalanche tracks, some of which very broad, crossing this part of the road.

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Fig. 3 Modelled avalanche tracks and accumulation areas for avalanche hazard levels 1 (dark blue) and 2(light blue) (Stotter et al. 2006)

Table 1 Areas of avalanchehazard level 1 on road no 76 fromSiglufjorur to Straumnes

The total length of the areas ofavalanche hazard level 1 is6.81 km

No Road km fromSiglufjorur

1 00.39

2 0.881.08

3 1.391.46

4 1.502.00

5 2.082.17

6 3.194.43

7 4.795.03

8 5.095.29

9 5.395.66

10 5.715.73

11 5.887.32

12 7.457.48

13 7.587.99

14 8.539.20

15 9.549.82

16 11.0911.41

17 12.2212.39

18 13.0513.32

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The areas of avalanche hazard level 1 in section 921 are limited to four comparativelyshort parts of the road.

West of km 13.32 the slopes along road no 76 are less steep and less high. There are

steep and high slopes in road section 941 (see Fig. 2). These are, however, so far away

from the road that the modelled accumulation areas for avalanche hazard level 1 of the four

potential avalanches in this section do not reach the road (see Fig. 7).

Table 2 Areas of avalanchehazard level 2 on road no 76 fromSiglufjorur to Straumnes

The total length of the areas ofavalanche hazard level 2 is8.99 km

No Road km fromSiglufjorur

1 00.42

2 0.881.083 1.382.17

4 3.174.54

5 4.695.06

6 5.095.30

7 5.395.66

8 5.715.73

9 5.867.38

10 7.438.03

11 8.529.23

12 9.509.82

13 11.0811.44

14 11.9612.15

15 12.2112.46

16 13.0313.35

17 13.4513.52

18 13.6113.63

19 13.7713.83

20 13.9514.05

21 14.1014.18

22 14.2114.24

23 31.9932.66

24 35.7435.76

25 35.8335.85

Fig. 4 Areas of avalanchehazard for avalanche hazard

levels 1 (dark blue) and 2 (lightblue) in road section 911: km03.2Siglufjorur to thenorthernmost point of road no 76

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The modelled accumulation areas of avalanches for avalanche hazard level 2 are gen-erally larger than those of avalanche hazard level 1. The areas of avalanche hazard level 2

thus usually form a band around the areas of avalanche hazard level 1 (see Fig. 3).

For road sections 911, 912 and 921, this means that 8.28 km of the road can be reached

by avalanches under extremely unfavourable conditions (worst case assumption). While in

road sections 911 and 912 with their extensive areas of avalanche hazard level 1, there are

only small further areas of avalanche hazard level 2, ten additional avalanches reach the

road in section 921 under the conditions of avalanche hazard level 2. The total extent of the

areas of avalanche hazard level 2 in this road section remains however limited.

Three further areas of avalanche hazard level 2 lie in road section 941 (Fig. 7).

4 Risk assessment

The assessment of the avalanche risk for the investigated section of road no 76 is based on

investigations by Wilhelm (1997, 1998, 1999) in the Alps. This approach has been applied

Fig. 5 Areas of avalanche hazard for avalanche hazard levels 1 (dark blue) and 2 (light blue) in roadsection 912: km 3.29.5northernmost point of road no 76 to Skrinavk

Fig. 6 Areas of avalanche hazard for avalanche hazard levels 1 (dark blue) and 2 (light blue) in roadsection 921: km 9.518.7Skrinavk to south of Hraun

Fig. 7 Areas of avalanche hazard (avalanche hazard level 2) in road section 941: km 31.138.7pipe 510to road to Straumnes

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e.g. to high alpine pass roads in Switzerland (Margreth et al. 2003), to mountain roads in

Italy (Zischg et al. 2004, 2005) and Austria (Gufler 2007; Huttenlau 2004) and to roads in

Norway (Kristensen et al. 2003). For the study on road no 76 between Siglufjorur and

Straumnes, it was adapted to comply with the data availability of the regional scale.

According to this approach, there is a distinction between (1) the individual risk and thecollective risk for the society for each area of avalanche hazard and (2) the cumulative

individual and collective risks for the investigated road section.

The individual death risk (1.1), collective death risk (1.2), cumulative individual death

risk (2.1) and cumulative collective death risk (2.2) can be determined by the following

equations:

rind i 1

Ti

gi zivi 24h

k 1:1

rcol i

1

Ti

gi WDT

vi 24h b k 1:

2

rind sum Xn

i1

rind i zi

24hXn

i1

gi

Ti vi k 2:1

rcol sum Xn

i1

rcol i WDT b

24hXn

i1

gi

Ti vi k 2:2

with

rind_i for individual death risk for avalanche hazard area i [1/years],rcol_i for collective death risk for avalanche hazard area i [deaths/year],

rind_sum for cumulative individual death risk for n areas of avalanche hazard [1/

years],

rcol_sum for cumulative collective death risk for n areas of avalanche hazard

[deaths/year],

Ti for mean return period of the avalanche [years],

gi for width of the area of avalanche hazard [km],

zi for number of passages per day,

vi for mean velocity in the investigated road section [km/h],

k for mean death rate in cars involved in avalanches,WDT for average daily winter traffic [cars],

for degree of occupancy [persons/car] and

i = 1, 2,,n areas of avalanche hazard

As the input data required for these equations are only partly available for the inves-

tigated section of road no 76, the following assumptions are made for the risk assessment.

Based on the census from 2008 (http://www.vegagerdin.is/vefur2.nsf/Files/umferd_

thjod_2008_skyrsla/$file/Umfer%C3%B0_%C3%A1_%C3%BEj%C3%B3%C3%B0vegum_

2008.pdf), an average traffic density (WDT) of 270 cars is used for road no 76 between

Siglufjorur and the tunnel (see Fig. 4) during the winter months and a WDT of 150 carsfor the section of the road from the tunnel to Straumnes. The number of passages (zi) is

assumed to be one for the areas of avalanche hazard from the northern end of the tunnel to

Straumnes, and 1.75 between Siglufjorur and the southern end of the tunnel as part of the

cars moving in this section of the road reflect local traffic from Siglufjorur. There are no

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data on the mean velocity (vi) and degree of occupancy () of the cars. For this assessment,

the former is estimated to be 60 km/h and the latter two persons/car.

Data on the death rate in cars hit by avalanches (k) are not available in Iceland.

According to the statistical analyses of avalanche accidents on roads in Switzerland by

Wilhelm (1999), 18% of the people who are hit by avalanches in their cars die. For moreremote areas with unfavourable topographic characteristics in Norway, Kristensen et al.

(2003) assume a death rate of 40% for avalanche accidents due to longer rescue times. On

road no 76, the distance between the settlements of Siglufjorur and Hofsos from where

rescue operations could start is about 60 km. Therefore, long rescue times should not have

a particular effect on the death rate in the investigated section of this road, and a death rate

of 18% as determined by Wilhelm (1999) is used in the assessment of the avalanche risk.

The length of the road sections affected by avalanches (gi) is derived from the modelled

areas of avalanche hazard (see Sect. 3.4).

The most difficult assumption concerns the mean return period (Ti) of the avalanches as

avalanche inventories are not available. Against this background, three groups of returnperiods are distinguished on the basis of the reconstructed areas of avalanche hazard (see

Sect. 3.3):

(1) Avalanches with a long return period (Ti = 100)

These are avalanches which reach the road only under extremely unfavourable condi-

tions as defined for avalanche hazard level 2 (see Sect. 3.3).

(2) Avalanches with a short return period (Ti = 10)

These are avalanches for which the reconstructed areas of avalanche hazard level 1 (seeSect. 3.3) reach far beyond the road and which thus come down to the road even in the case

of relatively small events.

(3) Avalanches with a medium return period (Ti = 30)

These are avalanches for which the reconstructed areas of avalanche hazard level 1 (see

Sect. 3.3) reach only little beyond the road and which thus only seldom come down to the

road.

The assessment of the individual death riskrind_i [1/years] for each area of avalanche

hazard on road no 76 from Siglufjorur to Straumnes identifies three areas of ava-

lanche hazard with an rind_i greater than 1 9 10-5 (orange colouring in Table 3).

These sections should be given priority for following detailed investigations and the

planning of possible protective measures. Twelve areas of avalanche hazard have an

rind_i between 1 9 10-5 and 1 9 10-6 (yellow colouring in Table 3), while in the

rest of the areas of avalanche hazard the rind_i is less than 1 9 10-6.

The results in Table 3 show that both the individual death risk rind_i [1/years] and the

collective death riskrcol_i [deaths/year] are very sensitive to the lengths of the road sections

in the areas of avalanche hazard. In the cases with an rind_i greater than 1 9 10-6 the

modelled areas of avalanche hazard are often very wide and thus affect long sections of the

road. If it is assumed, however, that not all avalanche events reach the maximum possible

extent the result looks different. For an event reaching half of the maximum possible

modelled width the rind_i remains below 1 9 10-5 everywhere in the investigated road

section and exceeds 1 9 10-6 in eleven areas of avalanche hazard altogether.

The cumulative individual death riskrind_sum [1/years] for all areas of avalanche hazard

on road no 76 between Siglufjorur and Straumnes, under the assumptions stated above

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and for the case that no measures of avalanche prevention or control or temporary closing

of the road are taken, is 9.314 9 10-5. The cumulative collective death risk rcol_sum[deaths/year] for the investigated road section is 0.0282, or one avalanche death in

36 years.

Table 3 Individual death risk rind_i [1/years], collective death risk rcol_i [deaths/year], cumulative indi-vidual death riskrind_sum [1/years] and cumulative collective death riskrcol_sum [deaths/year] for road no 76from Siglufjorur to Straumnes with gi for width of the area of avalanche hazard [km], Ti for mean returnperiod of the avalanche [years], zi for number of passages per day, vi for mean velocity in the investigatedroad section [km/h], k for mean death rate in cars involved in avalanches, WDT for average daily winter

traffic [cars] and for degree of occupancy [persons/car]

Road km gi

[km]Ti

[years]zi vi

[km/h] WDT

[cars]

[persons/car]rind_i

[1/years]rcol_i

[deaths/year]0.00-0.39 0.39 10 1.75 60 0.18 270 2 0,00000853 0,00263250

0.39-0.42 0.03 100 1.75 60 0.18 270 2 0,00000007 0,00002025

0.88-1.08 0.20 10 1.75 60 0.18 270 2 0,00000438 0,00135000

1.38-1.39 0.01 100 1.75 60 0.18 270 2 0,00000002 0,00000675

1.39-1.46 0.07 10 1.75 60 0.18 270 2 0,00000153 0,00047250

1.46-1.50 0.04 100 1.75 60 0.18 270 2 0,00000009 0,00002700

1.50-2.00 0.50 10 1.75 60 0.18 270 2 0,00001094 0,00337500

2.00-2.08 0.08 100 1.75 60 0.18 270 2 0,00000018 0,00005400

2.08-2.17 0.09 10 1.75 60 0.18 270 2 0,00000197 0,00060750

3.17-3.19 0.02 100 1 60 0.18 150 2 0,00000003 0,00000750

3.19-4.43 1.24 10 1 60 0.18 150 2 0,00001550 0,00465000

4.43-4.54 0.11 100 1 60 0.18 150 2 0,00000014 0,000041254.69-4.79 0.10 100 1 60 0.18 150 2 0,00000013 0,00003750

4.79-5.03 0.24 10 1 60 0.18 150 2 0,00000300 0,00090000

5.03-5.06 0.03 100 1 60 0.18 150 2 0,00000004 0,00001125

5.09-5.29 0.20 10 1 60 0.18 150 2 0,00000250 0,00075000

5.29-5.30 0.01 100 1 60 0.18 150 2 0,00000001 0,00000375

5.39-5.66 0.27 10 1 60 0.18 150 2 0,00000338 0,00101250

5.71-5.73 0.02 10 1 60 0.18 150 2 0,00000025 0,00007500

5.86-5.88 0.02 100 1 60 0.18 150 2 0,00000003 0,00000750

5.88-7.32 1.44 10 1 60 0.18 150 2 0,00001800 0,00540000

7.32-7.38 0.06 100 1 60 0.18 150 2 0,00000008 0,00002250

7.43-7.45 0.02 100 1 60 0.18 150 2 0,00000003 0,00000750

7.45-7.48 0.03 30 1 60 0.18 150 2 0,00000013 0,00003750

7.48.7.58 0.10 100 1 60 0.18 150 2 0,00000013 0,00003750

7.58-7.99 0.41 10 1 60 0.18 150 2 0,00000513 0,00153750

7.99-8.03 0.04 100 1 60 0.18 150 2 0,00000005 0,00001500

8.52-8.53 0.01 100 1 60 0.18 150 2 0,00000001 0,00000375

8.53-9.20 0.67 10 1 60 0.18 150 2 0,00000838 0,00251250

9.20-9.23 0.03 100 1 60 0.18 150 2 0,00000004 0,00001125

9.50-9.54 0.04 100 1 60 0.18 150 2 0,00000005 0,00001500

9.54-9.82 0.28 10 1 60 0.18 150 2 0,00000350 0,00105000

11.08-11.09 0.01 100 1 60 0.18 150 2 0,00000001 0,00000375

11.09-11.41 0.32 30 1 60 0.18 150 2 0,00000133 0,00040000

11.41-11.44 0.03 100 1 60 0.18 150 2 0,00000004 0,00001125

11.96-12.15 0.19 100 1 60 0.18 150 2 0,00000024 0,00007125

12.21-12.22 0.01 100 1 60 0.18 150 2 0,00000001 0,00000375

12.22-12.39 0.17 30 1 60 0.18 150 2 0,00000071 0,00021250

12.39-12.46 0.07 100 1 60 0.18 150 2 0,00000009 0,00002625

13.03-13.05 0.02 100 1 60 0.18 150 2 0,00000003 0,00000750

13.05-13.32 0.27 30 1 60 0.18 150 2 0,00000113 0,00033750

13.32-13.35 0.03 100 1 60 0.18 150 2 0,00000004 0,00001125

13.45-13.52 0.07 100 1 60 0.18 150 2 0,00000009 0,00002625

13.61-13.63 0.02 100 1 60 0.18 150 2 0,00000003 0,00000750

13.77-13.83 0.06 100 1 60 0.18 150 2 0,00000008 0,0000225013.95-14.05 0.10 100 1 60 0.18 150 2 0,00000013 0,00003750

14.10-14.18 0.08 100 1 60 0.18 150 2 0,00000010 0,00003000

14.21-14.24 0.03 100 1 60 0.18 150 2 0,00000004 0,00001125

31.99-32.66 0.67 100 1 60 0.18 150 2 0,00000084 0,00025125

35.74-35.76 0.02 100 1 60 0.18 150 2 0,00000003 0,00000750

35.83-35.85 0.02 100 1 60 0.18 150 2 0,00000003 0,00000750

rind_sum[1/years]/rcol_sum[deaths/year]

0,00009314

0,02817800

Areas of avalanche hazard with an rind_i greater than 1 9 10-5 are marked in orange, those with an rind_i

between 1 9 10-5 and 1 9 10-6 in yellow

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This cumulative individual death risk is one order of magnitude less than the value

determined for the road over the Fluela Pass in the Swiss Alps for the state without safety

measures by Margreth et al. (2003) (see the comparison of the cumulative individual death

risk and the cumulative collective death risk on road no 76 between Siglufjorur and

Straumnes with those on roads in the Alps in Table 4). It is also comparable to or less thanthe cumulative individual death risks found e.g. by Huttenlau (2004) and Gufler (2007) for

roads in inner Stubai and inner Oetz Valley in Austria, which include the risk reduction by

permanent measures, or by Zischg et al. (2005) for the Sulden road in Italy. The cumulative

collective death risk for the investigated section of road 76 is very low compared to

mountain roads in the Alps.

5 Conclusions

According to Wilhelm (1999), the accepted individual avalanche death risk rind_i [1/years]for the user of a public road is\1 9 10-5. Against this background, the assessment of the

individual death risk for each area of avalanche hazard on road no 76 from Siglufjorur to

Straumnes can be used to distinguish areas of avalanche hazard with a risk level above the

critical value, which should be given priority for following detailed investigations and the

planning of possible protective measures, from road sections where the avalanche death

risk is low and accepted based on international practice (see Table 3). The calculated risks

for the investigated section of road no 76 can further be reduced by measures like tem-

porary closing of parts of the road. This requires, however, a systematic monitoring of the

development of the avalanche hazard situation along the road.The cumulative individual and collective avalanche death risks in the investigated road

section, on the other hand, provide a reproducible and comparable measure for assessing

the avalanche hazard situation and the related risks both within the Icelandic public road

network and on an international scale (see Table 4). In this context, it is interesting to note

that the cumulative individual avalanche death riskrind_sum [1/year] determined for road no

76 between Siglufjorur and Straumnes of 9.314 9 10-5 is equal to the average traffic

mortality rate in Iceland in the last 10 years, i.e. 9 9 10-5 (http://www.us.is/id/4219).

The investigation into the avalanche hazard situation and the related risks on road no 76

between Siglufjorur and Straumnes in northern Iceland shows that a standardised regional

scale risk-based approach is practical to determine, analyse and assess the avalanchehazard situation on mountain roads in Iceland and guarantees comprehensible, reproduc-

ible and comparable results, which help to assign priorities in following detailed investi-

gations and the planning of measures.

For the natural hazard management, the results of this assessment need to be combined

with road data (e.g. current and expected traffic volume for various timescales, road

clearing and maintenance costs for problematic road sections). This allows cost benefit

analyses as a basis for decisions on protective measures. To meet these requirements, an

Internet Road Information System was developed (see Stotter et al. 2006).

In the last decades, Iceland used a lot of money to improve the public road network andthe accessibility of remote communities during the winter (see http://www.

vegagerdin.is/upplysingar-og-utgafa/aaetlanir/vegaaetlun/) often by building tunnels in

road sections with a high avalanche hazard potential (http://www.vegagerdin.is/vegakerfid/

jardgong/jardgvegakerf/; http://www.vegagerdin.is/storframkvaemdir/hedinsfjardargong/;

http://www.vegagerdin.is/storframkvaemdir/oshlidargong/). This was part of a policy to

provide an equally high level of infrastructure in all parts of the country and thus work

Nat Hazards (2011) 56:465480 477

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http://www.us.is/id/4219http://www.vegagerdin.is/upplysingar-og-utgafa/aaetlanir/vegaaetlun/http://www.vegagerdin.is/upplysingar-og-utgafa/aaetlanir/vegaaetlun/http://www.vegagerdin.is/vegakerfid/jardgong/jardgvegakerf/http://www.vegagerdin.is/vegakerfid/jardgong/jardgvegakerf/http://www.vegagerdin.is/storframkvaemdir/hedinsfjardargong/http://www.vegagerdin.is/storframkvaemdir/oshlidargong/http://www.vegagerdin.is/storframkvaemdir/oshlidargong/http://www.vegagerdin.is/storframkvaemdir/hedinsfjardargong/http://www.vegagerdin.is/vegakerfid/jardgong/jardgvegakerf/http://www.vegagerdin.is/vegakerfid/jardgong/jardgvegakerf/http://www.vegagerdin.is/upplysingar-og-utgafa/aaetlanir/vegaaetlun/http://www.vegagerdin.is/upplysingar-og-utgafa/aaetlanir/vegaaetlun/http://www.us.is/id/4219


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against the rural exodus. As a consequence of the current financial crisis in Iceland, public

spending on the road network has been cut back considerably and will be so for theforeseeable future. Against this background, an approach as it is presented in this paper can

become even more important both as a basis for a sustainable planning of measures and for

the communication of risk to the public.

Acknowledgments This paper is based on a study for the Icelandic Road Administration made at thealpsCentre for natural hazard and risk management GmbH in Innsbruck in cooperation with Lnuhonnunconsulting engineers in Reykjavk. We thank the Icelandic Road Administration and the Icelandic Meteo-rological Office for the provision of data and Dr. Halldor G. Petursson at the Icelandic Institute of NaturalHistory in Akureyri for useful information on the investigated road section. We also thank the reviewers fortheir constructive comments on the paper.

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Table 4 Comparison of the cumulative individual death risk rind_sum [1/years] and the cumulative col-lective death risk rcol_sum [deaths/year] on road no 76 between Siglufjorur and Straumnes with valuesdetermined for roads in the Alps

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