1. Hydraulic Design, Caltrans, 1976 E. Charter Way, Stockton, CA 95219.
2. Dept. of Civil and Environmental Engineering, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213.
3. Dept. of Civil and Environmental Engineering, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213 (corresponding author).