1. Professor, Hydrologic Research Laboratory, and J. Amorocho Hydraulics Laboratory, Dept. of Civil and Environmental Engineering, Univ. of California, Davis, CA 95616 (corresponding author).
2. Associate Professor, Dept. of Environmental Engineering, Pukyong National Univ., 608-737, South Korea.
3. Assistant Project Scientist, J. Amorocho Hydraulics Laboratory, Dept. of Civil and Environmental Engineering, Univ. of California, Davis, CA 95616.