Similarity of laterally separated samples over a sediment starved bed

The establishment of Total Maximum Daily Loads (TMDL) for contaminants entering water bodies requires the development of suitable methods for contaminant measurement. In an effort to assess quantities of suspended-sediment transport, an acoustic device is being developed in a collaborative effort between the University of Mississippi's National Center for Physical Acoustics and the Department of Civil Engineering along with the USDA-ARS National Sedimentation Laboratory with support from the National Science Foundation. The acoustic device will be non-intrusive, automatic, and provide suspended-sediment concentration and particle-size information at many points throughout the flow depth in a short time period. In order to test the new acoustic device, validation against an established measurement method is necessary. Due to the properties of the acoustic technique, this validation cannot be performed by sampling directly beneath the device. Towards this end, a laboratory flume with a sediment-starved bed was used to establish whether laterally separated samples collected simultaneously at like elevations within the flow would have similar concentrations. It was found that the average error, after a constant correction was applied, was 6%. This was deemed acceptable for use in instrument testing. Starved bed results are compared with previously collected data in dune and upper-stage plane bed regimes, demonstrating the profound effect of a mobile bed on the accuracy of suspended-sediment sampling. Copyright ASCE 2004.