Notwithstanding the large number of studies on bedforms such as dunes and antidunes, performing quantitative predictions of bedform type and geometry remains an open problem. Here we present the results of laboratory experiments specifically designed to study how sediment supply and caliber may impact equilibrium bedform type and geometry in the upper regime. Experiments were performed in a sediment feed flume with flow rates varying between 8 l/s and 15 l/s, sand supply rates varying between 0.6 kg/min and 16 kg/min, uniform and non-uniform sediment grain sizes with geometric mean diameter varying between 0.22 mm and 0.87 mm. The experimental data and the comparison with datasets available in the literature revealed that the ratio of the volume transport of sediment to the volume transport of water Q_s/Q_w plays a prime control in the equilibrium bed configuration. The equilibrium bed configuration transitions from washed-out dunes (lower regime), to downstream migrating antidunes (upper regime) for Q_s/Q_w between 0.0003 and 0.0007. For values of Q_s/Q_w greater than those typical of downstream migrating antidunes, the bedform wavelength increases with Q_s/Q_w. At these high values of Q_s/Q_w equilibrium bed configurations with fine sand are characterized by upstream migrating antidunes or cyclic steps, and significant suspended load. In experiments with coarse sand, equilibrium is characterized by plane bed with bedload transport in sheet flow mode. Standing waves form at the transition between downstream migrating antidunes and bed configurations with upstream migrating bedforms. 

The data were collected from a unidirectional laboratory flume where a constant flow and sediment supply rate were used upstream and a constant water level was imposed at the downstream end of the flume. After running the experiment for a while and making sure that the experiment reached a mobile bed equilibrium i.e., the bed slope and the water surface slope don't change over time, the measurement started. The bed and water surface elevations were measured by reading a ruler every 20 cm and the velocity profiles were measured by UVP. For Experiments 5-10 where the suspended sediment volume was significant enough to measure, a rack of siphons was used to measure the suspended sediment concentration at the end of the measurement reach. Pictures and videos were also taken during the experiments after the equilibrium condition was obtained.

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