期刊
CONTINENTAL SHELF RESEARCH
卷 30, 期 9, 页码 1149-1165出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.csr.2010.03.005
关键词
Rip current; Macro-tidal; Surf zone; Intermediate beach; Drifters; Cell circulation
类别
资金
- Peninsular Research Institute for Marine Renewable Energy (PRIMaRE)
- ONR [N0001409WR20221, N0001409WR20222]
- NSF [OCE 0728324]
- U of Delaware
- [HEIF2/RNLI]
- Natural Environment Research Council [NE/H004262/1] Funding Source: researchfish
- NERC [NE/H004262/1] Funding Source: UKRI
A field experiment was conducted on a high energy macro-tidal beach (Perranporth, UK) to examine rip current dynamics over a low-tide transverse bar/rip system in response to changing tide and wave conditions. Hydrodynamic data were collected using an array of in situ acoustic doppler current meters and pressure transducers, as well as 12 GPS-tracked Lagrangian surf zone drifters. Inter-tidal and sub-tidal morphology were measured through RTK-GPS and echo-sounder surveys. Data were collected for eight consecutive days (15 tides) over a spring-neap tidal cycle with tidal ranges of 4-6.5 m and offshore significant wave heights of 1-2 m and peak periods of 5-12 s. The hypothesis that rip current dynamics in a macro-tidal setting are controlled by the combination of variations in wave dissipation and morphological flow constriction, modulated by changes in tidal elevation was tested. During the measurement period, rip circulation was characterised by a large rotational surf zone eddy 0(200 m) extending offshore from the inner-surf zone to the seaward face of the inter-tidal transverse bar. During high- and mid-tide, water depth over the bars was too deep to allow wave breaking, and a strong longshore current dominated the surf zone. As the water depth decreased towards low-tide, wave breaking was concentrated over the bar crests initiating the rotational rip current eddy. Peak rip flow speeds of 1.3 m s(-1) were recorded around low-tide when the joint effects of dissipation and morphological constriction were maximised. At low tide, dissipation over the bar crests was reduced by partial bar-emergence and observations suggested that rip flows were maintained by morphological constriction and the side-drainage of water from the transverse bars. (C) 2010 Elsevier Ltd. All rights reserved.
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