Sediment supply plays an important role in the river morphology. However, the specific impact of sediment supply on river morphology is still not obvious. According to the concept of hydrograph boundary layer (HBL), upstream river bed change caused by imbalance of sediment supply to the capacity is able to propagate only limited length, and will have no effect on the river bed beyond such short length. This study has performed a two-dimensional morphodynamic calculation to test the concept of HBL, which has been proposed under 1-dimensional simulation, meaning that the concept of HBL is still valid for plane change of river morphology. In this study, unsteady flow with equilibrium or constant sediment supply has been employed in straight channel without deformable bank to simulate alternate bar morphodynamics. Wavelet analysis has been used to quantify the properties of the alternate bars at the downstream reach. The results indicate that under the condition with HBL, the characteristics of the alternate bars is slightly different from the case without HBL. The results suggest that the case of HBL may have created additional complexity that still affect the formation of the alternate bars beyond the HBL.

alternate bars; sediment transport; sediment supply; hydrograph boundary layer; gravel-bed rivers; numerical simulation