Abstract: By using a 2-D sediment mathematical model, influences of riverside relocation of Nanchang reach of Ganjiang River on flow, scouring and silting were computed. Based on the verification of the mathematical model with water surface, velocity distribution in a section, discharge ratios in the bifurcation reach, distribution of scouring and silting by site measured data, damming of flood water level, variation of velocity distribution in a section, and silting in the borrow areas in the reach before and after the relocation work were calculated.