Abstract Trap sediment by reservoirs has been effective in protecting the Lower Yellow River (LYR) but it can hard be sustainable. After reviewing the nature of sediment and siltation, the effect of coarse sediment ( d > 0.08–0.1 mm) (CS) on LYR siltation is studied. It is basically proved that the CS was apt to aggregate in special reach in the upmost fluctuating backwater of reservoirs due to the effect of hydraulic sorting; persistent dredging here in a fixed dredging basin (FDB) can remove most CS and prevent it from entering the LYR. It is thus possible to ease or to cease LYR siltation. Removing CS has also proved to be able to save reservoir capacity ( Zhou et al., 2010 ). Therefore, previously projected temporary trapping storages as the Xiaolangdi reservoir (XLDR) immediately upstream of LYR can be adjusted with new role to screen CS. The LYR can be protected without needing more dams.