Spatial and temporal distribution of fluvio-morphological processes on a meander point bar during a flood event

摘要

Morphological changes and hydraulic parameters are analyzed over a meander point bar along a sand-bedded river. Morphological changes caused by a flood are mapped using terrestrial and mobile laser scanners. The flow characteristics are simulated over the duration of the flood, which inundated the point bar completely. The spatial distribution of depth-averaged flow velocity, direction, and stream power at two different discharges is analyzed, in addition, the temporal variation of flow velocity, depth, and stream power on the point bar is resolved over the whole inundated period. The changes in discharge control the transverse shift of the high velocity core, which, in turn, has a major impact on the changes over the point bar. For example, a minor decrease in discharge may lead to a notable decrease in flow velocity on the point bar margin, enabling filling. Deposition occurs mainly during the recession of the flood, and thus, the duration of moderate discharges greatly influences accretion. The size of the supplied sediment also influences the filling over the bar head. Erosion mainly takes place during high discharges. A rapid decrease in discharge inhibits chute filling. The latest flood event seems to influence more the erosional compared to depositional processes.