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Temporal characteristics of coherent flow structures generated over alluvial sand dunes, Mississippi River, revealed by acoustic doppler current profiling and multibeam echo sounding

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Abstract

This paper investigates the flow in the lee of a large sand dune located at the confluence of the Mississippi and Missouri Rivers, USA. Stationary profiles collected from an anchored boat using an acoustic Doppler current profiler (ADCP) were georeferenced with data from a real-time kinematic differential global positioning system. A multibeam echo sounder was used to map the bathymetry of the confluence and provided a morphological context for the ADCP measurements. The flow in the lee of a low-angle dune shows good correspondence with current conceptual models of flow over dunes. As expected, quadrant 2 events (upwellings of low-momentum fluid) are associated with high backscatter intensity. Turbulent events generated in the lower lee of a dune near the bed are associated with periods of vortex shedding and wake flapping. Remnant coherent structures that advect over the lower lee of the dune in the upper portion of the water column, have mostly dissipated and contribute little to turbulence intensities. The turbulent events that occupy most of the water column in the upper lee of the dune are associated with periods of wake flapping.

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Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Temporal characteristics of coherent flow structures generated over alluvial sand dunes, Mississippi River, revealed by acoustic doppler current profiling and multibeam echo sounding
Year Published 2009
Language English
Publisher CRC Press
Contributing office(s) Office of Surface Water
Description 6 p.
Larger Work Type Conference Paper
Larger Work Title Proceedings of the IAHR Symposium on River Coastal and Estuarine Morphodynamics 2009
Conference Title IAHR Symposium on River Coastal and Estuarine Morphodynamics 2009
Conference Location Santa Fe, Argentina
Conference Date September 21-25 2009
Country United States
Other Geospatial Mississippi River and Missouri River
Online Only (Y/N) N
Additional Online Files (Y/N) N