1. Research Specialist, Water Resources Research Division, Water Resources and Environment Research Dept., Korea Institute of Construction Technology, 2311 Daewha-Dong, Ilsan-Gu, Goyang-Si, Gyeonggi-Do 411-712, Korea (corresponding author).
2. Associate Professor, Dept. of Civil and Earth Resources Engineering, Kyoto Univ., Kyoto 615-8540, Japan.
3. Professor, Dept. of Civil and Earth Resources Engineering, Kyoto Univ., Kyoto 615-8540, Japan.
4. Lecturer, Dept. of Civil and Earth Resources Engineering, Kyoto Univ., Kyoto 615-8540, Japan.