DOI: 10.15482/usda.adc/25328815
title: Data from: The effects of three repeated unsteady flow hydrographs on sand bed topography and sediment transport in a laboratory flume

description: This is the dataset that was used to make the figures for the publication entitled "The effects of three repeated unsteady flow hydrographs on sand bed topography and sediment transport in a laboratory flume"The citation for the publication is: Wren, D. G., McAlpin, T. O., Langendoen, E. J. and Kuhnle, R. A. The effects of three repeated unsteady flow hydrographs on sand bed topography and sediment transport in a laboratory flume. Journal of Hydraulic Engineering. Accepted 10/31/2024.How the dataset was generated: Experiments were conducted at the USDA-ARS National Sedimentation Laboratory in a 30-meters long x 1.22-meters wide x 0.61-meter-deep flume channel with a frequency-controlled pump motor and adjustable slope. The sand for the bed was purchased from a local source and had a median particle size of 0.43 mm. The bed load transport rate was measured by a Sedflux system that operated at 1 Hz (Hertz, cycles per second) using two drums suspended from load cells over 1.2 meters wide by 0.57 meters long sediment trap that was 28.5 meters from the channel origin. The mass of sand accumulated in the drums was recorded continuously, and the drums were dumped after the mass of sediment reached 30 kilograms. After leaving the drums, the sand particles were circulated through a 0.152-meter diameter pipeline and re-entered the flume at the upstream end. Material that bypassed the trap entered the main return pipe and was sampled from the center of the return pipe just downstream of the pump impellor using a 10.6-millimeter diameter sampling nozzle. Flow velocity into the nozzle was matched to the mean return line flow velocity to avoid biasing the concentration measurements. Discharge in the sampling line was checked by measuring the mass of water accumulated over time. Sediment-laden water was passed through a 0.062 mm sieve that retained sand particles and allowed the water to return to the flume channel. The mean sediment concentration from the physical samples was used to calculate the load that bypassed the Sedflux system. Bed surface elevations were measured acoustically at a rate of 10 Hertz using 32 transducers with an acoustic frequency of 5-million cycles per second, fired sequentially. The transducers were spaced at 3.7-centimeter intervals in a PVC bar with a blunt face and narrow trailing edge to minimize flow separation and drag. The transducers were held at a constant distance from the bottom of the flume and were always in contact with the water surface. The range data measured in the experiments was subtracted from the measured distance to the flume bottom to result in bed elevations. The working section of the flume, which took 3.85 minutes to scan, extended from 7.7 meters to 22.7 meters from the origin at the flume headbox. Position data recorded along with the acoustic range data was used to assign streamwise positions relative to the flume origin.Why the dataset was generated: Relative to the research into sediment transport in unsteady flows for gravel and gravel/sand mixtures, less research has focused on sand-bedded channels and the evolution of sand bedforms in response to changing flows. Even less research has combined sand load with detailed topographic measurements to arrive at a comprehensive picture of the adjustment processes for topography and transport rate caused by unsteady flow conditions. Additional research is needed to provide the data necessary for investigating relationships between unsteady flow rates, sediment transport, and bed topography. The dataset expands on previous research into sediment transport and bed topography in unsteady flows by having detailed, real-time measurements of bed topography over the width of a 15-m section of a laboratory flume, continuous measurements of sediment transport rate throughout the experiments, and continuous measurements of water-surface slope at 10 points along the test section. These measurements allowed for interactions between changing flow rates, bed topography, water surface slope, and sediment transport to be evaluated before, during, and after the flow hydrographs. The results include detailed analysis of data collected during non-symmetric flow of three repeated hydrographs of 1-, 2-, 3-, 4-, 5-, and 6-hour duration over a sand bed in a laboratory flume at the USDA-ARS National Sedimentation Laboratory.Data resources: Each file contains the data used to generate the figure corresponding to the figure number in the filename for the publication referenced at the beginning of this description.Figure_1.csvFigure_3.csvFigure_4.csvFigure_5.csvFigure _6.csvFigure_7.csvFigure_8.csvFigure_9.csvFigure_10A.csvFigure_10B.csvFigure_11.csvFigure_12.csvFigure_13.csvFigure_14.csv