Field Experiments on Longshore Sand Transport in the Surf Zone

Abstract

Eight fluorescent sand tracer experiments were performed in energetic surf zones on natural beaches and on beaches near structures to measure the short-term longshore sand transport rate. Tracer of up to four distinct colors was injected on a line crossing the surf zone to investigate the on-offshore distributions of the longshore sand adveetion velocity and transport rate. The tracer advection velocity, v , and the depth of mixing into the bed, b, were determined from large numbers of cores taken in situ throughout the sampling area. The sand advection velocity and mixing depth were not constant across the surf zone, but usually exhibited a maximum either toward the shoreline or toward the breaker line, or in both regions. The local breaking wave height, H. , and horizontal current velocity in the surf zone (yielding an average longshore current velocity V) were also measured. The data were interpreted with simple dimensional arguments to give the following results: b = 0.027 H,, v = 0.011 V, and the volumetric transport rate Q = 0.024 H V. Agreement was also found between the measured total longshore sand transport rate and a predictive expression due to Bagnold involving the breaking wave power and average longshore current velocity. Although the results appear reasonable and consistent, a problem remains concerning the apparent decrease in tracer advection speed alongshore recorded in most experiments at the longer sampling times.

Sand spit rhythmic development: A potential record of wave climate variations? Arçay Spit, western coast of France

“…The empirical coefficient for the CERC (1984) and the Kaczmarek formulae were tuned in order to obtain the best predictions at the three locations within the cross-shore profile. A value of K = 0.4 was retained for the CERC formula, which is included in the 0.21-0.9 range found in literature (Kraus et al, 1982;Kamphuis, 1991;Michel, 1997;Ciavola et al, 1997;US Army Corps of Engineers, 1998;Balouin et al, 2005). The K v coefficient for the Kaczmarek et al (2005) formula, which influences the magnitude of longshore current, was set to 2.5 using field data of Bertin et al (2007).…”

Tracer studies on the updrift margin of a complex inlet system

“…This method has been widely used for the application of tracer techniques to determine longshore transport (e.g., Komar and Inman, 1970;Kraus et al, 1982;Madsen, 1987;Ciavola et al, 1997Ciavola et al, , 1998. Some variations to the method described by Ciavola et al (1998) were required to facilitate its applicability to the updrift margin of an inlet.…”

“…The mixing depth is the thickness of the moving layer where grains of sediment are subjected to vertical and lateral movements by wave action and by the superimposed longshore current (Kraus, 1985). For this study, the mixing depth for each corer sample (Z oi ) was calculated according to the methodology proposed by Kraus et al (1982) and Kraus (1985) as the interval within beach cores where 80% of the FT was found. An average cross-shore profile of sand mixing depth was obtained by calculating the mean mixing depth for the samples located at the same cross-shore position along the beach.…”

“…Sediment tracer studies have been widely used for the study of sediment transport on straight beaches (i.e., Komar and Inman, 1970;Komar, 1977;Kraus, 1985;Kraus et al, 1982;Michel, 1997;Ciavola et al, 1997;1998). As a consequence, some empirical formulae have been developed to calculate longshore transport (i.e., C.E.R.C., 1984; Kamphuis et al, 1986).…”

The use of particle tracking in sediment transport studies: a review

“…The historical literature is dominated by sand tracking studies, with examples of use on sandy shorefaces (Komar & Inman 1970;Knoth & Nummeda 1977;Komar 1977;Kraus 1981Kraus , 1985Kraus et al 1982;Galvin 1987;Stepanian et al 2001;Michel 1997;Ciavola et al 1997a, b;1998;Levoy et al 1997Levoy et al , 1998Wong et al 1998;Munoz-Perez et al 1999), in tidal inlets (Balouin et al 2003;Vila Concejo et al 2004), in submarine canyon systems (see Ingle 1966;Dingier & Anima 1982;Tanaka et al 1998), in the shallow sub-tidal (Foster et al 1996;Johnson 2005) and wavedominated coastal environment (Beck et al 1991;McComb & Black 2005), and in harbours (e.g. Ferreira et al 2002) and in rivers (e.g.…”