Longshore Transport Evaluations at a Detached Breakwater

Bruno, Richard O.; Dean, Robert G.; Gable, Christopher G.

doi:10.9753/icce.v17.86

Cited by 11 publications

(12 citation statements)

References 3 publications

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“…Most of the reliable field data forming the basis of empirical longshore transport prediction formulas were obtained with sand tracers (Schoonees and Theron 1993). Long-term impoundment measurements [e.g., Bruno and Gable (1976), Bruno et al (1980), Dean et al (1982), and Dean (1989)] tend to confirm the order of magnitude of the transport rate found with tracers. Compared with results obtained with sand tracers, most measurements made by short-term impoundment and the streamer sediment trap have given transport rates one-tenth to one-fourth those found in long-term impoundment and with tracers.…”

Section: Introductionmentioning

confidence: 99%

Longshore Sediment Transport Rate Measured by Short-Term Impoundment

Wang

Kraus

1999

J. Waterway, Port, Coastal, Ocean Eng.

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The total longshore sediment transport rate in the surf zone was measured at a temporary groin installed at Indian Rocks Beach, west central Florida. Approximate mass balance between updrift accumulation and downdrift erosion, which served as an indicator of reliability, was obtained in four of the six runs, which were subjected to further analysis. Magnitudes of three of the four transport rates were considerably lower than predictions by the Coastal Engineering Research Center formula calculated based on contemporaneous measurements of the breaking waves. Error analysis indicated that the determination of the longshore wave-energy flux factor carried a 22-48% maximum uncertainty, and the measured volume-change rate carried a 22-43% uncertainty. The combined uncertainties produce a 40-90% maximum uncertainty in determination of the empirical transport coefficient K appearing in the Coastal Engineering Research Center formula. Comparable or greater uncertainty in K-values probably exists in the total database available for calibrating predictive formulas. The range in values of K in these measurements cannot be explained by measurement error or uncertainty. Therefore, it is concluded that K is not a constant and that other factors may enter, such as breaker type, turbulence intensity, and threshold for sediment transport.

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Section: Introductionmentioning

confidence: 99%

Longshore Sediment Transport Rate Measured by Short-Term Impoundment

Wang

Kraus

1999

J. Waterway, Port, Coastal, Ocean Eng.

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“…This may be due to the strict procedure used in defining the depth of mixing. In contrast, based on results of a trapping experiment, Bruno et al (1980), in a comparison using the CERC formula, report transport coefficients larger than those of Komar and Inman. We believe that a higher value is at least partially explained by the fact that sand caught by the trap includes a contribution from the longshore transport occurring outside the breaker line, and possible entrapment of onshore transport by the detached breakwater (Sasaki, 1975).…”

Section: Orrri 82 Simentioning

confidence: 79%

“…Only a limited number of field measurements of the longshore sand transport rate have been attempted. For example, Bruno et al (1980) discuss 56 field data points. Most of these measurements may be rejected for violating certain criteria or because of experimental uncertainties (Greer and Madsen, 1978;Bruno et al, ibid).…”

Section: Introductionmentioning

confidence: 99%

Field Experiments on Longshore Sand Transport in the Surf Zone

Kraus¹,

Isobe²,

Igarashi³

et al. 1982

Int. Conf. Coastal. Eng.

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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.

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“…These parameters are used to estimate the longshore sediment transport (LST), which is required to ascertaining the sediment budget of the region. The LST rate was estimated using Walton's equation (Walton and Bruno, 1989),…”

Section: Methodsmentioning

confidence: 99%