1. Prof., Dept. of Civ. Engrg. and Hydrotech Res. Inst., Nat. Taiwan Univ., Taipei 10617, Taiwan (corresponding author). E-mail: dlyoung@ hy.ntu.edu.tw
2. Grad. Student, Dept. of Civ. Engrg. and Hydrotech Res. Inst., Nat. Taiwan Univ., Taipei 10617, Taiwan.
3. Sr. Res. Fellow, Dept. of Civ. Engrg. and Hydrotech Res. Inst., Nat. Taiwan Univ., Taipei 10617, Taiwan.