ABSTRACT: Measurements in a braided river chute and lobe: I Flow pattern, sediment transport and channel change.

CGRG Bibliography of Canadian Geomorphology
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Abstract

The evolution of a new bar lobe below a chute over one week of diurnal meltwater flow was followed in the Sunwapta River, Alberta, Canada. During a week in which water discharge through the reach increased then decreased, a sediment wave passed into and partly along the reach. At first the chute aggraded, then sediment was eroded from the chute and deposited in a prograding lobe to one side of the original bar head between two distributaries. Measurements of velocity, shear stress, and gravel transport rate revealed day-to-day changes in the divergent pattern of flow and sediment transport. The off-center location of the lobe reflected an initial asymmetry in the pattern of flow and sediment transport, but as the lobe grew, the flow and transport gradually switched away to the other distributary. Width-averaged bed load transport rates do not agree well with average rates inferred from bar head deposition or from volumes and spatial patterns of scour and fill; the indirect estimates are considered more reliable than those based on direct sampling for necessarily brief durations. By the end of the study, the new lobe had almost accreted onto the original bar head, supporting the idea that most braid bars are of compound origin.

Bibliography of Canadian Geomorphology