1. Research Associate, Dept. of Civil Engineering, Kobe Univ., 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan.
2. Senior Research Engineer, Environmental Engineering Dept., Kajima Technical Research Institute, 2-19-1, Tobitakyu, Chofu-shi, Tokyo 182-0036, Japan.
3. Professor, Environmental Fluid Mechanics and Hydrology, Dept. of Civil and Environmental Engineering, Stanford Univ., Stanford, CA 94305-4020.