Abstract
Abstract. An evaluation of rock slide tsunami hazard is applied to all Norwegian lakes larger than 0.1 km2 based on their topographical setting. The analysis results in a topographic rock slide potential score that indicates the relative hazard in each lake. Even though the score value each lake receives should be interpreted with caution, the distribution of score values shows that we are able to make a clear distinction between lakes with a high vs. lakes with a low hazard. The results also show a clustering of threatened lakes in parts of Western Norway as well as some locations in Northern Norway. This makes the results useful as a tool for focusing further studies on regions or specific lakes that received high scores. The results also show how the method may be used for more detailed analysis of a given lake (or fjord). Maps can be produced that may serve as a guide when carrying out field campaigns or when designing scenarios for numerical simulations of tsunamis in the lake. It should be emphasised that the rock slide potential reported for each lake is based on the topographical setting alone and hence, does not represent the actual probability of rock slides into the lakes. For a given area, more detailed investigations of the geology, triggering factors and frequency of previous rock slide events should be carried out before definite statements about the actual hazard can be made.
Highlights
Rock slides and rock falls are relatively frequent in Norway. Furseth (2006) has recorded almost 800 such events over the last 500 years causing the loss of the approximately 500 lives
The final result of the analysis is a list of all lakes with the sum of probabilities within their catchment area. This sum can be looked upon as a topographic rock slide potential for the lake as it summarizes the probability of slides initiated www.nat-hazards-earth-syst-sci.net/9/353/2009/
The vast majority of the lakes (90%) received a score lower than 1% of the maximum score, and about 63% received less than 0.1% of the maximum. This skewed distribution of scores indicates that the topographic rock slide potential is negligible for a large portion of the lakes
Summary
Rock slides and rock falls are relatively frequent in Norway. Furseth (2006) has recorded almost 800 such events over the last 500 years causing the loss of the approximately 500 lives. The goal of hazard evaluation for sliding processes is to quantify the probability of occurrence of a potentially damaging event within a given area and a given period of time. Carrara et al, 1991; Guzzetti and Reichenbach, 1994) This requires that relevant data exist over the whole study area. In addition the statistical model will usually result only in the probability of a mapping unit being stable or not, with no explicit separation between release and run out area; it may be difficult to evaluate the hazard to a given spatial feature (e.g. a building, road or a lake) unless it lies within the potentially unstable mapping unit
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