TOWARD AN IMPROVED EMPIRICAL FORMULA FOR LONGSHORE SAND TRANSPORT

This paper presents results of two field experiments performed using portable traps to obtain point measurements of the longshore sand transport rate in the surf zone. The magnitude of the transport rate per unit width of surf zone is found to depend on the product of the local wave height and mean longshore current speed, but correlation is much improved by including two correction terms, one accounting for local wave energy dissipation and the other for the fluctuation in the longshore current. The field transport rates are also found to be compatible with laboratory rates obtained under combined unidirectional and oscillatory flow. Total transport rates previously reported for this experiment program are revised with recently determined sand trapping efficiencies.

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FIELD EXPERIMENTS ON LONGSHORE SAND TRANSPORT IN THE SURF ZONE

Coastal Engineering Proceedings ◽

10.9753/icce.v18.61 ◽

1982 ◽

Vol 1 (18) ◽

pp. 61 ◽

Cited By ~ 7

Author(s):

Nicholas C. Kraus ◽

Masahiko Isobe ◽

Hajime Igarashi ◽

Tamio O. Sasaki ◽

Kiyoshi Horikawa

Keyword(s):

Current Velocity ◽

Field Experiments ◽

Surf Zone ◽

Transport Rate ◽

Sand Transport ◽

Breaking Wave ◽

Longshore Current ◽

Mixing Depth ◽

Sand Transport Rate ◽

Advection Velocity

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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DISTRIBUTION OF SAND TRANSPORT RATE ACROSS A SURF ZONE

Coastal Engineering Proceedings ◽

10.9753/icce.v16.95 ◽

1978 ◽

Vol 1 (16) ◽

pp. 95 ◽

Cited By ~ 2

Author(s):

Toru Swaragi ◽

Ichiro Deguchi

Keyword(s):

Shear Stress ◽

Sediment Transport ◽

Surf Zone ◽

Transport Rate ◽

Sand Transport ◽

Shear Stresses ◽

Bottom Shear Stress ◽

Longshore Current ◽

Unidirectional Flow ◽

Longshore Sediment Transport

The distributions of longshore and on-offshore sediment transport rates in a surf zone were measured by an apparatus which was able to separately record both components of the sediment transport rate,, The characteristics of their distributions were discussed from the bottom shear stresses which were measured by the shear meter under the same wave conditions as the laboratory experiment of the sediment transport. The maximum bottom shear stress took place at the depth between the breaking depth of waves and the depth where the velocity of the longshore current showed a maximum. On the other hand, the maximum on-offshore and longshore sediment transport rates occured at the depth slightly shallower than the depth where the maximum bottom shear stress took place. What's more, the longshore sediment transport rates were represented by the longshore current velocity and the bottom shear stress generated by waves and the longshore current. However, the distribution of the on-offshore sediment transport rates showed more complicated profile than that of the longshore sediment transport rates because there were no eminent unidirectional flow in the direction normal to the shore line. Therefore, the on-offshore sediment transport rates could not be formulated by the bottom shear stresses.

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Distribution of Sand Transport Rate across a Surf Zone

Coastal Engineering 1978 ◽

10.1061/9780872621909.097 ◽

1978 ◽

Cited By ~ 6

Author(s):

Toru Sawaragi ◽

Ichiro Deguchi

Keyword(s):

Surf Zone ◽

Transport Rate ◽

Sand Transport ◽

Sand Transport Rate

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MODEL TESTS ON LITTORAL SAND TRANSPORT RATE

Coastal Engineering Proceedings ◽

10.9753/icce.v18.80 ◽

1982 ◽

Vol 1 (18) ◽

pp. 80

Author(s):

J.W. Kamphuis ◽

O.F.S.J. Sayao

Keyword(s):

Energy Dissipation ◽

Wave Energy ◽

Dissipation Rate ◽

Field Measurements ◽

Energy Dissipation Rate ◽

Transport Rate ◽

Sand Transport ◽

Similarity Parameter ◽

Wave Energy Dissipation ◽

Mobile Bed

This paper is an analysis of two sets of experimental results on littoral sand transport. A littoral sand transport expression is proposed, relating littoral transport rate to surf similarity parameter and hence to wave energy dissipation rate. The expression indicates that the "constant' in the CERC formula is dependent on the mobile bed beach slope and on the breaker index. The expression is also compared with some of the few published field measurements.

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LABORATORY STUDY ON SAND TRANSPORT OVER RIPPLES DUE TO ASYMMETRIC OSCILLATORY FLOWS

Coastal Engineering Proceedings ◽

10.9753/icce.v20.109 ◽

1986 ◽

Vol 1 (20) ◽

pp. 109 ◽

Cited By ~ 10

Author(s):

Shinji Sato ◽

Kiyoshi Horikawa

Keyword(s):

Laboratory Study ◽

Oscillatory Flow ◽

Transport Rate ◽

Sand Transport ◽

Hydraulic Parameters ◽

Oscillatory Flows ◽

Sand Transport Rate ◽

Bed Forms ◽

Sand Movement

Mechanism of sand movement due to asymmetric oscillatory flows was investigated through experiments. Measurements of bed forms, suspended sand concentration and net sand transport rate were carried out by using an oscillatory flow tunnel. The process of entrainment and suspension of sand above asymmetric ripples was quantitatively described. The geometry of ripples and the net sand transport rate in regular and irregular flows were expressed in terms of hydraulic parameters characterizing the oscillatory flow. Two-dimensionality of ripples was found to be an important factor in the estimation of the net sand transport rate.

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Aeolian Ripple Migration and Associated Creep Transport Rates

Geosciences ◽

10.3390/geosciences9090389 ◽

2019 ◽

Vol 9 (9) ◽

pp. 389 ◽

Cited By ~ 2

Author(s):

Sherman ◽

Zhang ◽

Martin ◽

Ellis ◽

Kok ◽

...

Keyword(s):

Wind Tunnel ◽

Field Experiments ◽

Shear Velocity ◽

Original Data ◽

Sand Transport ◽

Total Transport ◽

Original Field ◽

Ripple Migration ◽

Using Data ◽

And Migration

Wind-formed ripples are distinctive features of many sandy aeolian environments, and their development and migration are basic responses to sand transport via saltation. Using data from the literature and from original field experiments, we presented empirical models linking dimensionless migration rates, urgd (ur is the ripple migration speed, g is the gravity acceleration, and d is the grain diameter) with dimensionless shear velocity, u*/u*t (u* is shear velocity and u*t is fluid threshold shear velocity). Data from previous studies provided 34 usable cases from four wind tunnel experiments and 93 cases from two field experiments. Original data comprising 68 cases were obtained from sites in Ceará, Brazil (26) and California, USA (42), using combinations of sonic anemometry, sand traps, photogrammetry, and laser distance sensors and particle counters. The results supported earlier findings of distinctively different relationships between urgd and u*/u*t for wind tunnel and field data. With our data, we could also estimate the contribution of creep transport associated with ripple migration to total transport rates. We calculated ripple-creep transport for 1 ≤ u*/u*t ≤ 2.5 and found that this accounted for about 3.6% (standard deviation = 2.3%) of total transport.

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Field Experiments on Longshore Sand Transport in the Surf Zone

Coastal Engineering 1982 ◽

10.1061/9780872623736.061 ◽

1982 ◽

Cited By ~ 26

Author(s):

Nicholas C. Kraus ◽

Masahiko Isobe ◽

Hajime Igarashi ◽

Tamio O. Sasaki ◽

Kiyoshi Horikawa

Keyword(s):

Field Experiments ◽

Surf Zone ◽

Sand Transport

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INFLUENCE OF BREAKER TYPE ON SURF ZONE DYNAMICS

Coastal Engineering Proceedings ◽

10.9753/icce.v20.69 ◽

1986 ◽

Vol 1 (20) ◽

pp. 69

Author(s):

A.S. Arcilla ◽

A. Vidaor ◽

J.L. Monso

Keyword(s):

Surf Zone ◽

Laboratory Data ◽

Dynamic State ◽

Large Set ◽

Longshore Current ◽

Stochastic Forcing ◽

Wave Energy Dissipation ◽

The Mean ◽

Definition Of ◽

Empirical Coefficients

Two of the most significant variables for surf zone hydrodynamic analyses are the mean rate of wave energy dissipation, D, and the longshore current velocity, VI . A detailed theoretical model is extremely difficult to establish (definition of bottom and free surface boundaries, stochastic forcing terms, intense turbulent mixing, etc). The type and amount of existing measured values (laboratory and field) also preclude any accurate calibration, particularly for the more complex formulations. The paper, therefore, presents an average (cross-shore) comparison among state-of-the-art models for D and VI. This illustrates the dependence of these variables on the surf zone dynamic state (closely related to the beach stage, (Short, 1978)), characterized by Iribarren's parameter, ir. Well defined relationships with Ir are obtained for these variables. An expansion of the range of validity of certain models is also attained by calibration of their characteristic free parameters as functions of Ir using a large set of field and laboratory data, and by comparing their general expresion with that of (Losada and S.Arcllla, 1985), which does not include any free parameter. Therefore, theoretical laws for D and VI as simple functions of beach, wave and dynamic state parameters are presented, together with an improved estimation of the empirical coefficients appearing in the various models, suitable for prediction in all ranges of Ir, even though data on the collapsing-surging range are scarce and should require further calibration.

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