Flow and Sediment Transport in a Sand Bedded Meander

The boundary shear stress pattern and the superelevation of the water surface in a meander on a small stream are predicted from two simple equations representing a frictionally dominated force balance. This comes about even though inertial forces due to local bed topography delay crossing of the boundary shear stress maximum to a position farther downstream than would otherwise be expected. Measured bedform migration rates reflect the boundary shear stress field, and in this river, bedform crest orientations respond to gradients in the shear stress field by becoming oblique to the general flow direction. When so aligned the bedforms interact with the helical flow in the curved channel and induce a near bottom secondary current which, in the upstream part of the bend, is outward above the crests and inward along the troughs. At the downstream end of the bend this pattern is reversed and significant quantities of sediment are transported along troughs from one point bar to the next. This near bottom flow pa...