Shallow dynamic flows are very important processes in environmental systems, yet they are notoriously difficult to measure. For example, on coral reefs, shallow flows over the reef crest typically range from 0 to 1 m depth and velocity up to 1–2 m s−1including oscillatory motion of waves. To directly measure depth and velocity in this challenging environment, we retrofitted a vertical acoustic Doppler current profiler (ADCP, Teledyne, RDI) designed for streams into a new shallow water acoustic Doppler current profiler system (SW‐ADCP) to expand memory and power limitations and allow for deployment in wave‐dominated environments. We captured variations in shallow reef crest depth and flow over a period of 3 weeks in the reef/lagoon system of Ofu Island, American Samoa. The new SW‐ADCPs recorded water depth and three‐dimensional velocity in 3 cm bins every 3 s. We then used velocity profiles to estimate volumetric flow and drag coefficients and verified these estimates using boundary layer theory. We observe that the mean velocity profile is well approximated by a log‐layer formulation with
Coral reefs are hydrodynamically rough, creating turbulent boundary layers that transport and mix various scalars that impact reef processes and also can be used to monitor reef health. Often reef boundary layer characteristics derived from a single instrument are assumed to accurately represent the study site. This approach relies on two assumptions: first, that the boundary layer is relatively homogeneous across the area of interest, and second, that two instruments displaced in space or with different spatiotemporal resolution would produce similar results when sampling the same flow. We deployed four velocimeters over a 15 × 20 m reef at 10 m depth in the Chagos Archipelago. The site had a 1 m tidal range, and waves were primarily locally generated wind waves with
- Award ID(s):
- 1948189
- NSF-PAR ID:
- 10362635
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Oceans
- Volume:
- 126
- Issue:
- 12
- ISSN:
- 2169-9275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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