1. Professor, School of Civil Engineering, Iran Univ. of Science and Technology, Tehran 16846-13114, Iran; Dept. of Land, Air, and Water Resources, Univ. of California, Davis, CA 95616 (corresponding author).
2. Assistant Professor, Dept. of Civil Engineering, Ardabil Univ., Ardabil 56199-11367, Iran.
3. Associate Professor, Dept. of Land, Air, and Water Resources, Univ. of California, Davis, CA 95616.