1. Professor, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO.
2. Professor, School of Civil and Environmental Engineering, Yonsei Univ., Seoul 120-749, Korea.
3. Postdoctoral Fellow, Dept. of Civil and Environmental Engineering, Colorado State Univ., Fort Collins, CO (corresponding author).
4. Professor, Institute of Hydromechanics and Water Resources Management, ETH, Zurich, Switzerland.