Bagnold described the incipient motion based on the uplift force. Kramer discussed the sediment incipient motion particles based on the apparent particle motion condition. Inspired by Shields’ studies, Dey and Papanicolaou carried out advanced studies to determine the incipient motion under the influence of a steady flow. Shields defined the incipient motion based on the sediment transport rate. The upstream bend’s incipient motion was observed for the mean velocity-to-critical velocity ratio of 0.89, while the downstream bend’s incipient motion occurred for the ratio of 0.78. Moreover, increasing the ratio increased the maximum sedimentary height by 3, 10, 23, 48, 49, and 56 times. Results indicated that the maximum scour depth at the downstream bend increased as a result of changing the mean velocity-to-critical velocity ratio from 0.8 to 0.84, 0.86, 0.89, 0.92, 0.95, and 0.98 by, respectively, 1.5, 2.5, 5, 10, 12, and 26 times.
In addition, the upstream bend’s effect on the downstream bend was investigated. To this end, bed topography variations along the meander and the downstream straight path were addressed for different mean velocity-to-critical velocity ratios.
In this study, different mean velocity-to-critical velocity ratios have been tested at the upstream straight path to determine the meander’s incipient motion. These two 180-degree mild bends are located between two upstream and downstream straight paths. As 180-degree meanders are observed in abundance in nature, a meandering channel with two consecutive 180-degree bends was designed and constructed to investigate bed topography variations.
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