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 in Hydro-Engineering, PGE Renewable Power, ul. Cebertowicza 9/29, Gdańsk 80-809, Poland (corresponding author).