An overview of the need for avalanche protection measures in Iceland. Report prepared for the Icelandic Ministry for the Environment and local authorities in towns threatened by avalanches

Tómas Jóhannesson, Karstein Lied, Stefan Margreth, Frode Sandersen
VÍ-R96004-ÚR03; November 1996

Summary

Preliminary proposals for avalanche protection measures for 8 communities in Iceland are described and the cost of the measures is estimated. These communities include the largest densely populated avalanche prone areas in the country. The cost of the protection measures is compared to the value of buildings and infrastructure in the respective areas which are threatened by avalanches. The total cost of all the proposed defense structures is about 7000 million IKR. The estimated total value of buildings and infrastructure in the areas is usually several times higher than the estimated cost of the protection measures.

Potential cost of direct avalanche defenses of individual buildings in areas, where explicit defense proposals are not made in this report, may be expected to exceed several hundred million IKR. Furthermore, the cost of avalanche protection measures in communities, which were not explicitly considered in this overview, and the cost of slush and debris flow protection measures, which were only briefly considered in the overview, needs to be considered. This cost may also be expected to exceed several hundred million IKR. The cost of permanent evacuation of buildings in avalanche hazard areas, where avalanche protection measures are not practical, will depend on future regulation about the purchasing of property in hazard areas by the government. This cost is difficult to estimate, but it may also possibly exceed several hundred million IKR. When all this is taken into consideration, the result is that the total cost of avalanche protection measures, including purchasing of buildings in avalanche hazard areas, may be estimated to be on the order of 9000 million IKR. There is an uncertainty in the cost estimate due to the uncertain extent of avalanche hazard areas and due to uncertain design assumptions for the proposed defense structures. There is also considerable uncertainty in the cost estimate due to the additional protection measures in areas which were not explicitly considered in the report. This uncertainty is difficult to quantify, but it reasonable to assume that the total cost of protection measures will be in the range 7000 to 14000 million IKR.

The avalanche hazard in the different areas is indicated with a risk index which is based on the frequency and magnitude of avalanches, on one hand, and on the number of people in the endangered areas, on the other hand. More than half of the total cost of the proposed protection measures is in areas where the risk index indicates the highest avalanche risk.

Direct economic loss due to avalanches in towns in Iceland in the 22 year period between 1974 and 1995, together with the cost of purchasing buildings and the construction cost of defense structures, is about 3800 million IKR. This includes the cost associated with the relocation of Súđavík, the purchasing of houses in Hnífsdalur and the estimated cost of defense structures for Flateyri, which are under construction. The loss does not include damage due to avalanches in rural areas (\fIe.g.\fP farm buildings, power and telephone lines and ski lifts), which is substantial, but may be assumed to be much smaller than the estimated total loss in major avalanche accidents in and near towns.

A total of 52 people have been killed by avalanches in buildings, at work sites or within towns during the same period. If the death of a person in an avalanche accident is included in the economic loss in a similar way as in a recent study of the economic loss due to traffic accidents in Iceland (100 million IKR per fatal accident), the total cost of avalanche accidents in Iceland in the last 22 years is similar to the total cost of avalanche protection measures which are described in this report.

It is necessary to initiate research of the avalanche conditions in Iceland in order to improve the observational basis for the design of protection measures. The most important research areas in this respect are hazard mapping, regular monitoring of the distribution of snow in the starting zones of avalanches, research of the effectivity of dams and breaking mounds, measurements of the physical properties of snow in Iceland with special regard to design assumptions for supporting structures and investigation of the utility of snow fences under Icelandic conditions.

It must be stressed that continuous monitoring of avalanche danger must be performed in the future in all areas where there is avalanche danger. Conditions for the construction of avalanche protection measures are sometimes difficult due to lack of space for dams or uncertainty about the location of the most important starting zones for the construction of supporting structures. In such circumstances, the construction of the defense structures must be combined with the monitoring of the avalanche conditions and a readiness to execute an appropriate evacuation plan in extreme situations. Even when the conditions for the construction of the protection measures are good, one must also monitor avalanche conditions carefully in order to be able to see whether unforeseen conditions are developing so that appropriate measures can then be taken to insure the safety of the community.