1. a Water Management & Research Center , K-water Institute , Jeonmin-Dong, Yusong-Gu , Daejeon , Korea
2. b School of Civil and Environmental Engineering , Kookmin University , Songbuk-gu , Seoul , Korea
3. c Department of Civil Engineering , Pukyong National University , Yongdang-Dong, Nam-Gu , Busan , Korea Phone: Fax: