FIELD INVESTIGATION OF BEACH PROFILE CHANGES AND THE ANALYSIS USING EMPIRICAL EIGENFUNCTIONS

In order to investigate the response of beach profiles to incident waves, computations by the empirical eigenfunction analysis proposed by Winant et al. are performed. The analysis of the data obtained at Ajigaura Beach over three years from 1976 to 1979 indicates that beach profile changes due to longshore and onshore-offshore sediment transport are separable by the empirical eigenfunction method. The beach profile changes due to longshore sediment transport has a time lag of 12 weeks with respect to the change of wave direction at Ajigaura Beach. It was found theoretically that this time lag was due to the sand waves propagating in the longshore direction. Regarding as onshore-offshore sand transport, the second eigenfunction is associated with the beach changes due to onshore-offshore sand transport caused by the change of wave height.

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FIELD INVESTIGATION OF LONGSHORE TRANSPORT DISTRIBUTION

Coastal Engineering Proceedings ◽

10.9753/icce.v18.98 ◽

1982 ◽

Vol 1 (18) ◽

pp. 98 ◽

Cited By ~ 1

Author(s):

E.P. Berek ◽

R.G. Dean

Keyword(s):

Sediment Transport ◽

Active Contours ◽

Field Investigation ◽

Wave Direction ◽

Change Analysis ◽

Incoming Wave ◽

Longshore Sediment Transport ◽

Longshore Transport ◽

The Cross ◽

Water Depths

Following a change in wave direction, the active contours in an idealized pocket beach respond by rotating such that they approach a perpendicular orientation relative to the incoming wave rays. Assuming that cross-shore sediment transport does not contribute to this contour rotation, and that the contours are in the early stages of this equilibration process, the amount of contour rotation can be interpreted as the cross-shore distribution of the longshore sediment transport. As part of the Nearshore Sediment Transport Study, detailed nearshore profile measurements were conducted at Santa Barbara, California. Twenty-two of these profile lines were located on Leadbetter Beach, which is a quasi-pocket beach. To explore the concept described above, two of the nine intersurvey periods were selected due to their strong indications of wave direction change. Analysis of these data sets yielded two estimates of cross-shore distribution of longshore sediment transport which were compared with those presented by Komar, Fulford and Tsuchiya. Although these three distributions differ significantly, the effect of the tidal variations is to "smear" the differences in the inferred distributions as evident in the contour displacements. It was found that none of the relationships for longshore transport distribution predicted the amount of transport inferred in water depths greater than one meter. It is possible, especially for one of the intersurvey periods that the changes in contour locations were so extreme that substantial crossshore sediment transport was induced and would be interpreted as longshore transport occurring in water depths greater than had actually occurred. The method introduced here should be useful in other field and laboratory programs to investigate the cross-shore distribution of longshore sediment transport.

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SIMULATION OF LONG-TERM SHORELINE CHANGE DRIVEN BY LONGSHORE AND CROSS-SHORE SEDIMENT TRANSPORT

Coastal Engineering Proceedings ◽

10.9753/icce.v36v.sediment.31 ◽

2020 ◽

pp. 31

Author(s):

Yan Ding ◽

Sung-Chan Kim ◽

Richard B. Styles ◽

Rusty L. Permenter

Keyword(s):

Sediment Transport ◽

Shoreline Change ◽

Breaking Wave ◽

Beach Profile ◽

Shoreline Evolution ◽

Longshore Sediment Transport ◽

Wave Energy Flux ◽

Semi Empirical ◽

Evolution Modeling

Driven by wave and current, sediment transport alongshore and cross-shore induces shoreline changes in coasts. Estimated by breaking wave energy flux, longshore sediment transport in littoral zone has been studied for decades. Cross-shore sediment transport can be significant in a gentle-slope beach and a barred coast due to bar migration. Short-term beach profile evolution (typically for a few days or weeks) has been successfully simulated by reconstructing nonlinear wave shape in nearshore zone (e.g. Hsu et al 2006, Fernandez-Mora et al. 2015). However, it is still lack of knowledge on the relationship between cross-shore sediment transport and long-term shoreline evolution. Based on the methodology of beach profile evolution modeling, a semi-empirical closure model is developed for estimating phase-average net cross-shore sediment transport rate induced by waves, currents, and gravity. This model has been implemented into GenCade, the USACE shoreline evolution model.

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Nearshore Waves and Littoral Drift Along a Micro-Tidal Wave-Dominated Coast Having Comparable Wind-Sea and Swell Energy

Journal of Marine Science and Engineering ◽

10.3390/jmse8010055 ◽

2020 ◽

Vol 8 (1) ◽

pp. 55

Author(s):

Jesbin George ◽

V. Sanil Kumar ◽

R. Gowthaman ◽

Jai Singh

Keyword(s):

Sediment Transport ◽

Wave Model ◽

Model Data ◽

Wave Direction ◽

Littoral Drift ◽

Relative Contribution ◽

Wave Parameters ◽

Longshore Sediment Transport ◽

Wind Sea ◽

Small Change

The nearshore wave characteristics and variations in littoral drift (longshore sediment transport; LST) are estimated based on different approaches for four years along the Vengurla coast, with comparable wind-sea and swell energy assessed. The waverider buoy-measured data at 15 m water depth is utilized as the input wave parameters along with the reanalysis model data, and the numerical wave model Delft-3D is used for estimating the nearshore wave parameters. The relative contribution of wind-seas and swells on LST rates are specifically examined. The clear prevalence of west-southwest waves implies the prevalence of south to north longshore sediment transport with net transport varying from 0.19–0.37 × 105 m3/yr. LST is strongly dependent on the breaker angle and a small change in the wave direction substantially alters the LST, and hence reanalysis/model data with coarse resolutions produce large errors (~38%) in the LST estimate. The annual gross LST rate based on integral wave parameters is only 58% considering the wind-seas and swells separately, since the wind-sea energy is comparable to swell energy, and the direction of these two systems differs significantly.

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EXPERIMENTS ON BEACH PROFILE CHANGE WITH A LARGE WAVE FLUME

Coastal Engineering Proceedings ◽

10.9753/icce.v18.85 ◽

1982 ◽

Vol 1 (18) ◽

pp. 85 ◽

Cited By ~ 3

Author(s):

Ryoichi Kajima ◽

Takao Shimizu ◽

Kohki Maruyama ◽

Shozo Saito

Keyword(s):

Simple Model ◽

Transport Rate ◽

Sand Transport ◽

Two Dimensional ◽

Beach Profile ◽

Large Wave ◽

Wave Flume ◽

Grain Sizes ◽

Profile Changes ◽

Profile Change

Two-dimensional beach profile changes were investigated with a newly constructed prototype-scale wave flume. The flume is 205 m long, 3.4 m wide and 6 m deep. Sand of two grain sizes was used in the experiments. Analysis of the results was made through use of the parameter C, introduced by Sunamura and Horikawa (1974) to classify beaches as either erosional and accretionary. Beach profile changes obtained in the flume were similar to those in the prototype (field). Net sand transport rate distributions were classified into five types, two of which do not seem to have been observed in laboratory (smallscale) experiments. A simple model describing the five types was developed for evaluating two-dimensional beach profile changes.

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BEACH PROFILES AT TORREY PINES, CALIFORNIA

Coastal Engineering Proceedings ◽

10.9753/icce.v15.75 ◽

1976 ◽

Vol 1 (15) ◽

pp. 75 ◽

Cited By ~ 2

Author(s):

David G. Aubrey ◽

Douglas L. Inman ◽

Charles E. Nordstrom

Keyword(s):

Sediment Transport ◽

Incident Wave ◽

Wave Energy ◽

Energy Conditions ◽

Beach Profile ◽

High Wave ◽

Wave Characteristics ◽

Spectral Estimates ◽

High Wave Energy ◽

Incident Waves

Beach profiles have been measured at Torrey Pines Beach, California for four years and correlated with tides and accurate spectral estimates of the incident wave field. Characteristic equilibrium beach profiles persist for time spans of up to at least two weeks in response to periods of uniform incident waves. These changes in the beach profiles are primarily due to on-offshore sediment transport which can be related to variations in wave characteristics and tidal phase. The most rapid readjustment of the beach profile occurs during high wave energy conditions coincident with spring tides. Alternatively, the highest berm building is associated with moderate to low waves that coincide with spring tides.

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Estimation of Longshore Sediment Transport Using Video Monitoring Shoreline Data

Journal of Marine Science and Engineering ◽

10.3390/jmse8080572 ◽

2020 ◽

Vol 8 (8) ◽

pp. 572

Author(s):

Jung-Eun Oh ◽

Yeon S. Chang ◽

Weon Mu Jeong ◽

Ki Hyun Kim ◽

Kyong Ho Ryu

Keyword(s):

Sediment Transport ◽

Recovery Process ◽

Video Monitoring ◽

Energy Conditions ◽

Winter Storms ◽

Shoreline Changes ◽

Longshore Sediment Transport ◽

Beach Processes ◽

Line Theory ◽

Incident Waves

Video monitoring systems (VMS) have been used for beach status observation but are not effective for examining detailed beach processes as they only measure changes to the shoreline and backshore. Here, we extracted longshore sediment transport (LST) from VMS in order to investigate long- and short-term littoral processes on a pocket beach. LST estimated by applying one-line theory, wave power, and the oblique angle of incident waves were used to understand shoreline changes caused by severe winter storms. The estimated LST showed good agreement with the shoreline changes because the sediments were trapped at one end of the pocket beach and the alongshore direction of transported sediments was corresponded to the direction of LST. The results also showed that the beach that was severely eroded during storms was also rapidly recovered following the evolution of LST, which indicates that the LST may play a role in the recovery process while the erosion was mainly caused by the cross-shore transport due to storm waves. After the beach was nourished, beach changes became more active, even under lower wave energy conditions, owing to the equilibrium process. The analysis presented in this study could be applied to study inhomogeneous beach processes at other sites.

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Nearshore currents and beach topography, Martinique Beach, Nova Scotia

Canadian Journal of Earth Sciences ◽

10.1139/e77-161 ◽

1977 ◽

Vol 14 (8) ◽

pp. 1906-1915 ◽

Cited By ~ 2

Author(s):

J. R. Keeley

Keyword(s):

Nova Scotia ◽

Theoretical Model ◽

Sediment Transport ◽

Wind Direction ◽

Seasonal Changes ◽

Late Spring ◽

Beach Profile ◽

Storm Waves ◽

Longshore Sediment Transport ◽

Subsequent Disappearance

A series of profiles across Martinique Beach, Nova Scotia, surveyed at monthly intervals between April and October, 1974, showed the formation and subsequent disappearance of large cuspate projections on the beach face. A theoretical model of the distribution of longshore currents on the beach was used to predict the expected positions of convergences and divergences in the longshore sediment transport. The observed projections were found to occur in positions of convergence of waves generated by the southeasterly winds, dominant in the late spring. The disappearance of the cusps was associaled with the seasonal veering of wind direction to the southwest as summer advanced.The size of the seasonal changes in beach profile suggests that the morphology of Martinique Beach is controlled primarily by storm waves.

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