Bed-Slope Amplification of Non-Cohesive Sediment Transport under Supercritical Open-Channel Flow
Keywords:
bed-load sediment transport, supercritical open-channel flow, bed slope, excess shear stress, tilting flumeAbstract
Bed slope and discharge control the capacity of open-channel flow to mobilize sediment, yet their relative effects are often difficult to separate because bed-load transport is intermittent and empirical equations are sensitive to hydraulic context. This study quantifies the effects of bed slope and discharge on non-cohesive sand transport in a controlled tilting flume. Sand with a nominal diameter of 0.6 mm and a specific gravity of 2.71 was tested at bed slopes of 1.5%, 2.0%, and 2.5% under discharges of 252.92 and 391.42 cm³ s⁻¹. Three independent trials were conducted for each treatment combination, and trial means were analyzed using two-factor ANOVA on the logarithmic scale. Sediment transport increased consistently with both slope and discharge. Bed slope produced the stronger effect (p < 0.001; partial η² = 0.794), while discharge was also significant (p = 0.0086; partial η² = 0.450); their interaction was not significant. Excess bed shear stress explained 83.8% of variation among treatment means. Schoklitsch predictions were closer to measurements than the implemented Shields-based estimates, although both generally underestimated transport. The results show that modest slope changes can sharply amplify sediment mobility under supercritical flow.
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