LAUSR

Abstract This study investigated bend morphology and dynamic changes of two highly convoluted meandering rivers, the Black River and the White River, in the Upper Yellow River Watershed of the Qinghai-Tibet Plateau (QTP), China. Using remotely sensed data, we characterized channel morphology and lateral changes of 290 meander bends in the two rivers. These bends exhibited extensive development of compound structures with each involving multiple sub-bends. Their migration patterns were dominated by extension, translation, and the combination of both, with the average migration rate higher in bends that changed by translation than that of bends by other modes. These morphological changes led to a longitudinal erosion-to-deposition pattern along the two studied rivers. Our analyses showed that the White River migrated much faster with more frequent cutoffs but fewer compound bends than the Black River, which may be attributed to the greater stream power of the former. We found a similar single-mode relationship between migration rate and bend curvature, commonly reported in previous studies, indicating that the largest migration rate occurred in bends with medium curvatures. This relationship, however, was altered to a quasi-monotonic inverse one when the average migration rates of bends were calculated for each class interval of bend curvatures, suggesting the complexity of bend morphodynamics. In general, the two studied meandering rivers migrated slower than many other meandering rivers worldwide, which allowed their bends to evolve into complex planform structures.