1. Division of Urban and Environmental Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan
2. Department of Civil Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
3. Water Examination Laboratory, Hanshin Water Supply Authority, 5-11-1 Tano, Amagasaki 661-0951, Japan
4. Centre for River Basin Environmental Research, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan