Dam Tunsbergdalsvatn. A dam subjected to waves generated by avalanches, and to extreme floods from a glacier lake

Abstract

The construction of Leirdøla power plant was started in 1975 and will be completed in 1978. The owner is the Norwegian Water Resources and Electricity Board. The power plant is situated in Western Norway, close to Jostedalsbreen, the largest glacier in Norway. A 100 MW Francis aggregate will be installed, designed for Q = 25 m3/s and a head of 450 m (Fig. I). Most of the runoff takes place during the summer. To store the water for the winter season, when the demand for electricity is largest, the natural lake, Tunsbergdalsvatn is being constructed, a 40 m high earth- and rockfill dam, comprising 0.9 million m3. The reservoir is expected to reach peak level in September to November. During winter it will be emptied gradually. During planning, it became evident that the dam would be subjected to the effects of the following special environmental factors: - waves generated by avalanches; - extreme floods from a glacier lake. This paper describes investigations and estimations with regard to the influence of these special environmental factors on the dam design.