1. Hydrologist, Dept. of Biological and Agricultural Engineering, Texas A&M Univ., 2117 TAMU, 301C Scoates Hall, College Station, TX 77843-2117.
2. Research Professor, Dept. of Civil Engineering, Inha Univ., 100 Inha-ro, Nam-gu, Incheon 402-751, Republic of Korea (corresponding author).