1. Assistant Professor, Dept. of Irrigation and Hydraulic Engineering, Alexandria Univ., Alexandria 11432, Egypt.
2. Postdoctoral Fellow, Dept. of Civil and Environmental Engineering, Univ. of South Carolina, 300 Main St., Columbia, SC 29208.
3. Mr. and Mrs. Irwin B. Kahn Professor, Dept. of Civil and Environmental Engineering, Univ. of South Carolina, 300 Main St., Columbia, SC 29208.
4. Professor, Dept. of Civil and Environmental Engineering, Univ. of South Carolina, 300 Main St., Columbia, SC 29208 (corresponding author).