1. Graduate Student, Dept. of Civil, Architectural, and Environmental Engineering, Missouri Univ. of Science and Technology, Rolla, MO 65409.
2. Senior Researcher, Dam and Watershed Maintenance Dept., K-water, 200 Sintanjin-Ro, Daedeok-Gu, Daejeon 306-711, Republic of Korea.
3. Associate Professor, Dept. of Soil and Water Conservation, National Chung Hsing Univ., Taichung 402, Taiwan.
4. Associate Professor, Dept. of Civil Engineering, National Taiwan Univ., Taipei 10617, Taiwan (corresponding author).