Abstract
Rip currents are an integral component of intermediate beaches as described by the WRIGHT and SHORT (1984) model, but their morphologic character and behaviour at various states has yet to be suitably quantified. This study utilises field measurements encompassing an almost complete cycle of low-energy beach state evolution to describe morphometric approaches for quantifying rip current behaviour. First, a subjective analyses of the relative planimetric areal extent of rip feeder, rip-neck and non-rip (bar) components showed that active rip areas (AR) were never greater than 50% of the total system area (AT) with AR decreasing from 40-45% during the longshore bar-trough (LBT) state to less than 20% during the low tide terrace (LTT) state. Second, the concept of overfit and underfit rip currents (SHORT, 1985) is examined by describing topographically confined and unconfined flow conditions through the use of the Rip Fit Parameter; RF = (M-O)/Ar, where M = morphologic cross-sectional rip channel area; O = overbank cross-sectional rip area, and Ar = total cross-sectional rip area. In general, low-energy rips are unconfined at high tide for all intermediate states and are confined when RF > 0.5 during transverse bar-rip and low-tide terrace conditions at low-tide. Confined rips are also associated with maximum rip flow velocities and can be related to planimetric rip area. Both morphometric approaches provide new and useful quantification of intermediate beach state rip current morphology during accretionary conditions.
Published Version
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