A GIS method for assessment of rock slide tsunami hazard in Norwegian lakes and reservoirs

An evaluation of rock slide tsunami hazard is applied to all Norwegian lakes larger than 0.1 km(2) 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.