1. Research Fellow, Norwegian Univ. of Science and Technology, S.P.Andersens veg 5, 7491 Trondheim, Norway (corresponding author).
2. Professor, Norwegian Univ. of Science and Technology, S.P.Andersens veg 5, 7491 Trondheim, Norway.
3. Head Engineer, Norwegian Water Resources and Energy Directorate, Dam Safety Section, Postboks 5091 Majorstua, 0301 Oslo, Norway.