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- Title
A test of the ADV-based Reynolds flux method for in situ estimation of sediment settling velocity in a muddy estuary.
- Authors
Cartwright, Grace; Friedrichs, Carl; Smith, S.
- Abstract
Under conditions common in muddy coastal and estuarine environments, acoustic Doppler velocimeters (ADVs) can serve to estimate sediment settling velocity ( w) by assuming a balance between upward turbulent Reynolds flux and downward gravitational settling. Advantages of this method include simple instrument deployment, lack of flow disturbance, and relative insensitivity to biofouling and water column stratification. Although this method is being used with increasing frequency in coastal and estuarine environments, to date it has received little direct ground truthing. This study compared in situ estimates of w inferred by a 5-MHz ADV to independent in situ observations from a high-definition video settling column over the course of a flood tide in the bottom boundary layer of the York River estuary, Virginia, USA. The ADV-based measurements were found to agree with those of the settling column when the current speed at about 40 cm above the bed was greater than about 20 cm/s. This corresponded to periods when the estimated magnitude of the settling term in the suspended sediment continuity equation was four or more times larger than the time rate of change of concentration. For ADV observations restricted to these conditions, ADV-based estimates of w (mean 0.48±0.04 mm/s) were highly consistent with those observed by the settling column (mean 0.45±0.02 mm/s). However, the ADV-based method for estimating w was sensitive to the prescribed concentration of the non-settling washload, C. In an objective operational definition, C can be set equal to the lowest suspended solids concentration observed around slack water.
- Subjects
ACOUSTIC Doppler current profiler; VELOCIMETERS; REYNOLDS number; SEDIMENT sampling; ESTUARIES; SUSPENDED solids
- Publication
Geo-Marine Letters, 2013, Vol 33, Issue 6, p477
- ISSN
0276-0460
- Publication type
Article
- DOI
10.1007/s00367-013-0340-4