RIPEX: Observations of a rip current system
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Authors
MacMahan, Jamie H.
Thornton, Ed B.
Stanton, Timothy P..
Reniers, J.H.M.
Subjects
rip currents
morphodynamics
nearshore
surf zone
transverse bar
circulation
morphodynamics
nearshore
surf zone
transverse bar
circulation
Advisors
Date of Issue
2005
Date
Publisher
Language
Abstract
Rip current kinematics and beach morphodynamics were measured for 44 days at Sand City, Monterey Bay, CA using 15
instruments composed of co-located velocity and pressure sensors, acoustic Doppler current profilers, and kinematic GPS
surveys. The morphology consisted of a low-tide terrace with incised quasi-periodic rip channels, representative of transverse
bars. Offshore (17 m depth) significant wave height and peak period ranged 0.20–3.0 m and 5–20 s. The mean wave direction
was consistently near 08 resulting in rip channel morphology, which evolved in response to the changing wave characteristics.
An inverse relationship between sediment accreting on the transverse bar and eroding in the rip channel was found. The spatial
distribution of sediment is reflected in the background rip current flow field. The mean velocity magnitudes within the rip
channel (transverse bars) increased offshore (onshore) with decreasing tidal elevations and increased with increasing sea-swell
energy. Eulerian averaged flows were predominantly shoreward on the transverse bars and seaward within the rip channel
throughout the experiment, resulting in a persistent cellular circulation, except during low wave energy. The rip current spacing
to the rip channel width was less than or equal to two, which suggests that the rip currents are influenced by each other and that
no two-dimensional bar return flow should be present. The vertical velocity profile on the bar indicated that the flow was
predominantly shoreward. The flow field within the surf zone was depth uniform, except for significant shear occurring near the
surface, owing to Stokes drift. The wave-induced transport hypothesis is evaluated.
Type
Article
Description
The article of record as published may be located at http://dx.doi.org/10.1016/j.margeo.2005.03.019
Series/Report No
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Funder
The Steep Beach Experiment was funded by the Office of Naval Research (ONR), Coastal Sciences Program under contract N0001402WR20188 and data analysis by the National Science Foundation under contract OCE-01366882 and ONR. JM held a National Research Council-NPS Research Associate-ship funded by the National Science Foundation under contract OCE-01366882 and ONR contract N0001402WR20188. Additional funding was provied to JM by the Florida Sea Grant Program. AR held a National Research Council-NPS Research Associateship funded by ONR. Additional funding for AR was provided by the Dutch National Science Foundation, contract DCB.5856.
Format
Citation
Marine Geology, Vol. 218, (2005), pp. 113– 134
Distribution Statement
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.