1. Professor, Dept. of Civil and Environmental Engineering, Koszalin Univ. of Technology, Koszalin 75-453, Poland.
2. Assistant Professor, Institute of Hydro-Engineering, Polish Academy of Sciences, Gdańsk 80-328, Poland.
3. General Specialist on Hydroengineering, PGE Renewable Power, Gdańsk 80-809, Poland (corresponding author).