Submitted to: Journal of Hydraulic Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2015
Publication Date: 5/13/2016
Publication URL: http://handle.nal.usda.gov/10113/62742
Citation: Rigby Jr, J.R., Wren, D.G., Kuhnle, R.A. 2016. Passive acoustic monitoring of bed load for fluvial applications. Journal of Hydraulic Engineering. doi: 10.1061/(ASCE)HY.1943-7900.0001122.
Interpretive Summary: The transport of sediment along the bed of streams is a key component of total sediment load and very difficult to measure reliably. Passive acoustic methods for measuring bed load were first tried in the 1930s but development of the method has proceeded slowly despite promising qualitative results. Advances in the fundamental understanding of the acoustics of bed load in ocean and estuarine settings has reignited research into the use of passive acoustics for measuring bed load in rivers. We review the existing knowledge of sound generation by underwater sediments moving along the bed and suggest avenues for advancement in the field.
Technical Abstract: The sediment transported as bed load in streams and rivers is notoriously difficult to monitor cheaply and accurately. Passive acoustic methods are relatively simple, inexpensive, and provide spatial integration along with high temporal resolution. In 1963 work began on monitoring emissions from particle-on-particle collisions termed sediment-generated noise (SGN). Until the late 20th century, investigations tended to be qualitative and demonstrated the promise of the method. Beginning in the 1980s, efforts were focused on fundamental physical processes in marine settings. More recent research has renewed the emphasis on fluvial settings, but a number of outstanding questions remain. In particular far less attention has been given to the acoustic physical environment of fluvial applications compared with marine settings. This paper reviews the development of SGN as a quantitative bed load monitoring technique. Key differences in the acoustics of the fluvial and marine settings are highlighted, such as the waveguide effects and boundary interactions in rivers, and next steps for the development of SGN techniques are suggested.