Abstract: Hydrodynamic characteristics and bed load transport in backwater condition are not well comprehended yet. In particular, problems such as the sediment transport and fluvial process in natural backwater river or reservoir backwater area need to be explained theoretically. In this research, theoretical analysis, field observed data and flume experiment are carried out as follows firstly the differences of bed load transport in different conditions were analyzed, then the non-uniform flow structure in backwater condition was observed through flume experiment, and finally the bed load transport formula suitable for reservoir backwater condition was deduced based on data from field observation and flume experiment by regression analysis. Results reveal that when the backwater index β is beyond 1.3, traditional formulas are no longer suitable to calculate the bed load transport in backwater condition. The proposed bed load transport formula in backwater condition in consideration of bed stress and backwater index could be applied for researching the bed load transport in rivers of Three Gorges Reservoir area.

Key words: backwater condition, bed-load transport, flume experiment, sediment transport rate formula