Flow characteristics along the rip current system under low-energy conditions

D. Bowman, D. Arad, D. S. Rosen, E. Kit, R. Goldbery, A. Slavicz

Research output: Contribution to journalArticlepeer-review

Abstract

This paper aims to determine the flow signature of the rip current under low-energy conditions based on current meters at Herzliyya Beach, Israel, on the southeastern Mediterranean shore. Field experiments, conducted under relatively calm wave conditions (Tsig = 3-6 s, Hsig = 0.3-1.1 m), included current and wave monitoring with morphological mapping. Current data were analysed for shore-normal and resultant components and the time series of instantaneous and smoothed velocities provided current and orbital wave velocities. Statistical and spectral processing yielded energy distributions, specific current discharge, and directional data. Velocity and velocity-time asymmetry increased from the feeders to the neck and subsequently slowed down towards the rip head. The directional range of the flow was narrow in channeled feeders and even better concentrated at narrow necks with higher velocities. The flows at the rip head were typically divergent. Systematic spatial change of energy spectra was observed along the rip system: the subharmonic frequency band dominated the feeders and the inner surf embayments and decreased gradually toward the rip neck with a simultaneous gradual increase in incident wave frequency. The infragravity band frequency was minor everywhere. Velocity spectra at oblique bars with sheltered areas differed from spectral changes at transverse bars with an exposed inshore. The velocity at the rip neck was above the threshold for grain movement whereas at the head, it was usually below the threshold. Textural parameters of the beach sand could not be systematically related to the current velocity, i.e., no environmental groupiness was evident along the rip system.

Original languageEnglish
Pages (from-to)149-167
Number of pages19
JournalMarine Geology
Volume82
Issue number3-4
DOIs
StatePublished - Aug 1988
Externally publishedYes

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