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1 September 2005 Evaluation of Longshore Transport Equations with OBS Sensors, Streamer Traps, and Fluorescent Tracer
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Measurements of longshore sediment transport rate were conducted on a reflective to intermediate sandy beach during energetic sea breeze activity. The suspended load transport was obtained with optical backscatter sensors, current meters, and streamer traps, whereas the total load rate was measured with fluorescent sand tracer. The streamer trap measurements revealed an exponential vertical distribution of the suspended sediment flux, with the degree of vertical mixing decreasing in the onshore direction. A continuous time series of longshore suspended sediment flux across the surf zone was obtained by combining streamer trap measurements with data collected with surf zone instruments. Comparison of the suspended longshore flux with the total longshore flux derived from the dispersal of fluorescent tracer indicated that the relative contribution of suspended load to total load was ca. 35%. The movement of sand tracer further demonstrated that nearshore sediments were transported obliquely across the surf zone, challenging our conventional view of dividing nearshore sediment transport into cross-shore and longshore components. Sand tracer was found to move onshore as well as offshore, indicating a bi-directional sediment exchange between outer surf zone and swash zone. Equations from previous studies predicted the suspended longshore transport rate rather well, but underestimated the total longshore transport rate by a factor of two. The Kamphuis formula underestimated both suspended and total longshore transport rates.

Aafke Tonk and Gerhard Masselink "Evaluation of Longshore Transport Equations with OBS Sensors, Streamer Traps, and Fluorescent Tracer," Journal of Coastal Research 2005(215), 915-931, (1 September 2005).
Accepted: 28 July 2004; Published: 1 September 2005

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