1. a Iowa Inst. of Hydraulic Research , The University of Iowa , Iowa City, IA, 52242-1585, U.S.A.
2. b Civil Engineering Department , The University of Louisiana at Lafayette , Lafayette, LA, 70504- 2291, U.S.A.
3. c Civil and Environmental Engineering , The University of Iowa , Iowa City, IA, 52242-1585, U.S.A.