scholarly journals LONGSHORE CURRENT AND TRANSPORT ACROSS NON-SINGULAR EQUILIBRIUM BEACH PROFILES

1988 ◽  
Vol 1 (21) ◽  
pp. 104
Author(s):  
Kevin R. Bodge
Keyword(s):  
Sediment Transport ◽  
Longshore Current ◽  
Beach Profile ◽  
Infinite Slope ◽  
Profile Shape ◽  
Equilibrium Beach Profile ◽  
Longshore Sediment Transport ◽  
Beach Processes ◽  
Mathematical Expressions ◽  
Equilibrium Profile

The longshore current and longshore sediment transport distributions are described across an equilibrium beach profile comprised of an intersecting planar foreshore and a concave-up profile. Such a profile shape avoids the singularity associated with the infinite-slope at the shoreline described by traditional equilibrium profile forms and allows prediction of beach processes at and above the shoreline. The mathematical expressions which describe the distributions are simplified and can be more readily applied relative to expressions previously presented in the literature. The findings are in general agreement with similar previous analytic studies and indicate that the current and transport maxima are generally located at about the intersection of the planar and concave-up portions of the profile.

scholarly journals LONGSHORE SEDIMENT TRANSPORT ON DEAN BEACH PROFILES

1984 ◽  
Vol 1 (19) ◽  
pp. 101
Author(s):  
William G. McDougal ◽  
Robert T. Hudspeth
Keyword(s):  
Sediment Transport ◽  
Eddy Viscosity ◽  
Viscosity Coefficient ◽  
Strength Parameter ◽  
Longshore Current ◽  
Transport Models ◽  
Longshore Sediment Transport ◽  
Equilibrium Profile ◽  
Eddy Viscosity Coefficient ◽  
Stress Models

Natural beaches exhibit an equilibrium profile that is planar nearshore and non-planar, concave-up offshore. The longshore current on these Dean equilibrium beaches is shown to depend on the location of the intersection between the planar and non-planar profiles and on the dimensionless mixing strength parameter if the eddy viscosity coefficient is linearly dependent on the distance offshore. The effect of the profile intersection on the longshore sediment transport rate is demonstrated for two energetics based sediment transport models; viz. the Bagnold and energetics stress models.

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

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.

scholarly journals Estimation of Longshore Sediment Transport Using Video Monitoring Shoreline Data

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.

Nearshore currents and beach topography, Martinique Beach, Nova Scotia

1977 ◽  
Vol 14 (8) ◽  
pp. 1906-1915 ◽  
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.

scholarly journals In Use of Permeable Groin for Reducing Longshore Sediment Transport at Tanjung Bayang Beach of South Sulawesi

2018 ◽  
Vol 1 (2) ◽  
pp. 70-73 ◽  
Author(s):  
Hasdinar Umar ◽  
Sabaruddin Rahman ◽  
Chairul Paotonan ◽  
Ahmad Yasir Baeda
Keyword(s):  
Sediment Transport ◽  
Coastal Protection ◽  
Breaking Wave ◽  
Longshore Current ◽  
Surrounding Area ◽  
South Sulawesi ◽  
Longshore Sediment Transport ◽  
Reduction Coefficient ◽  
Before And After ◽  
Transport Analysis

Breaking wave near beaches is the main force to generate longshore currents, which moved the sediment at surrounding area. Due to its negative outcome, which are erosion and sedimentation, the need of longshore sediment transport analysis become very important. One of the tools for solving that problem is by using coastal protection structure such as permeable groin. Permeable groin may reduce the rate of longshore sediment transport respectively by changing the level of permeability of the groin itself. The objective of this research was to obtain analytical results of the longshore sediment transport reduction analysis by using permeable groins at Tanjung Bayang Beach of South Sulawesi. Reduction of sediment transport along the beach was analyzed by calculating reduction coefficient, which is the ratio between the longshore current before and after hitting the permeable groins. The result showed that with 40% of permeability, the groin can reduced longshore sediment transport at Tanjung Bayang Beach for almost 50%; from 341.37x103 m3/year to 170.68x103 m3/year.

scholarly journals LONGSHORE SEDIMENT TRANSPORT RATE vs. CROSS - SHORE DISTRIBUTION OF SEDIMENT GRAIN SIZES

1988 ◽  
Vol 1 (21) ◽  
pp. 145
Author(s):  
C.I. Moutzouris
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Transport Rate ◽  
Longshore Current ◽  
Sediment Grain Size ◽  
Grain Sizes ◽  
Sediment Transport Rate ◽  
Power Equation ◽  
Longshore Sediment Transport ◽  
The Cross

Existing models for longshore sediment transport rate computations assume the sediment grain size and grain sizerelated parameters to be uniform in both the cross-shore and longshore directions. Field results from tideless beaches, which are briefly described in the paper, show that the latter change in both directions due to changing wave energylevels. The sensitivity analysis described in the paper shows that both longshore current and transport rate computations are sensitive to the cross-shore changes in grain size.Finally, a modified linearity coefficient for the wave power equation is proposed based upon the cross-shore distributions of grain size as found in nature.

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

1982 ◽  
Vol 1 (18) ◽  
pp. 84
Author(s):  
Hiroshi Hashimoto ◽  
Takaaki Uda
Keyword(s):  
Sediment Transport ◽  
Time Lag ◽  
Field Investigation ◽  
Sand Transport ◽  
Wave Direction ◽  
Beach Profile ◽  
Sand Waves ◽  
Longshore Sediment Transport ◽  
Profile Changes ◽  
Incident Waves

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.

scholarly journals DISTRIBUTION OF SAND TRANSPORT RATE ACROSS A SURF ZONE

1978 ◽  
Vol 1 (16) ◽  
pp. 95 ◽  
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.

Numerical Simulation of Dynamic Shoreline Changes Behind a Detached Breakwater by Using an Equilibrium Formula

2017 ◽  
Author(s):  
Jung Lyul Lee ◽  
John Rong-Chung Hsu
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Shoreline Change ◽  
Beach Profile ◽  
Excellent Performance ◽  
Shoreline Changes ◽  
Shoreline Evolution ◽  
Equilibrium Beach Profile ◽  
Shape Equation ◽  
The One

Salient and tombolo are common features found in the lee of detached breakwaters. The empirical parabolic bay shape equation (PBSE) can be applied when their planform is fully developed, whereas numerical model is required to simulate the dynamic shoreline evolution prior to the planform reaching static equilibrium. This paper reports the excellent performance of PBSE through the comparison with labaratory results and the development of a numerical model for dynamic shoreline change that utilizes the concept of PBSE and equilibrium beach profile. Formulation proposed for sediment transport rate is theoretically compared with that in GENESIS. The governing equation for the combined shoreline response model is based on the one-line beach model, which includes shoreline changes owing to longshore and cross-shore sediment transport. Finally, numerical results reveal, by comparing with an experimental case in the laboratory, that the model is adequate to successively simulating the dynamic evolutions of the shoreline behind a detached breakwater.

scholarly journals Artificial beach as a structure to defend a sea coast from the storm surge impact (based on the example of the eastern Gulf of Finland)

2019 ◽  
Vol 59 (2) ◽  
pp. 292-301
Author(s):  
I. O. Leont’yev
Keyword(s):  
Storm Surge ◽  
Gulf Of Finland ◽  
Total Width ◽  
Beach Profile ◽  
Medium Sand ◽  
Longshore Sediment Transport ◽  
Long Time ◽  
Equilibrium Profile ◽  
Beach Volume ◽  
Sea Coast

The model of artificial beach to protect a sea coast subjected to erosion under impact of significant storm surge is suggested. The beach profile properties are based on the concept of equilibrium profile by Dean. It is shown that the use of coarser sand provides greater total width of beach, but requires greater volume of constructional berm. At the same time, the loss of material due to longshore sediment transport decreases. Application of the model to three segments of eroded coast in Kurortniy region of St. Petersburg (Eastern Gulf of Finland) allows recommend the medium sand 0.3–0.5 mm to construct the artificial beach. In this case, the width of dry beach section would be about 80–140 m, while the volume of constructional berm would be (1.3÷3.2)×102 m3/m depending on sediment deficit in a given coastal segment. In order to minimize the relative loss of material it is suggested to construct the beach of which the length is not less than 1 km. In this case, more than half of initial beach volume would be kept even after 30 years. Modeling of extreme storm impact leads to conclusion that the designed beach profiles are only slightly deformed and able conserve their resource over a long time.

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