Scour of Sand Beaches in Front of Seawalls

Herbich, John B.; Ko, Stephen C.

doi:10.1061/9780872620131.040

Cited by 7 publications

(8 citation statements)

References 2 publications

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“…In laboratory experiments, Herbich, Murphy & Van Weele (1965) have shown that near a reflecting seawall bars can form at the spacing of half the incident wavelength. Analysing the boundary layer above a rigid bed for moderate surface wavelengths, Carter, Liu & Mei (1973) have found that the wave-induced drift current forms circulating cells when the reflection coefficient exceeds 0.414.…”

Section: Introductionmentioning

confidence: 99%

Formation of sand bars under surface waves

Mei

2000

J. Fluid Mech.

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A quantitative theory is described for the formation mechanism of sand bars under surface water waves. By assuming that the slopes of waves and bars are comparably gentle and sediment motion is dominated by the bedload, an approximate evolution equation for bar height is derived. The wave field and the boundary layer structure above the wavy bed are worked out to the accuracy needed for solving this evolution equation. It is shown that the evolution of sand bars is a process of forced diffusion. This is unlike that for sand ripples which is governed by an instability. The forcing is directly caused by the non-uniformity of the wave envelope, hence of the wave-induced bottom shear stress associated with wave reflection, while the effective diffusivity is the consequence of gravity and modified by the local bed stress. During the slow formation, bars and waves affect each other through the Bragg scattering mechanism, which consists of two concurrent processes: energy transfer between waves propagating in opposite directions and change of their wavelengths. Both effects are found to be controlled locally by the position of bar crests relative to wave nodes. Comparison with available laboratory experiments is discussed and theoretical examples are studied to help understand the coupled evolution of bars and waves in the field.

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Section: Introductionmentioning

confidence: 99%

Formation of sand bars under surface waves

Mei

2000

J. Fluid Mech.

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“…According to the literature, magnitude of the undertow is reduced in the presence of partially standing waves [9,14]. A model was presented to estimate the distribution of undertow in the surf zone for arbitrary beach topography by Okayasu et al [15] in which the horizontal and vertical distribution of undertow is given through a set of semi-empirical equations.…”

Section: Theoretical Developments 21 Hydrodynamicsmentioning

confidence: 99%

Investigation of the safety of seawalls against scouring

Neshaei

Ghanbarpour

2013

Safety and Security Engineering V

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Scouring phenomena is one of the most important issues in Coastal Engineering. Constructing protective structures such as seawalls on the shoreline can cause scouring and the estimation of scouring depth in front of such structures is one of the important problems in the design of their foundations. In this paper, based on experimental data, the beach level changes and potential of scouring at different locations in front of the constructed seawalls and in the case of a natural coast without protective structures are estimated and compared, which can be useful in coastal engineering studies and design and management of coastal defense projects. The results predicted by the model are compared with the experimental data indicating the good accuracy of the proposed model. The results obtained from the present work clearly indicate that the construction of seawalls at the shoreline results in a reduction of the associated seaward sediment transport and bed profile evolution but increases the local scouring depth which may cause damage to such structures. Incorporating the nonlinear effect of wave and wave current interaction into the proposed model has resulted in an improvement in the prediction of sediment transport, bed level changes and scouring depth in front of seawalls. This, in turn, results in a more effective design of seawalls to increase their safety against scouring.

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“…Wave height is the most significant variable to the depth of scour (39 and 41). Other important parameters are the position of the wall in the profile, the beach slope, the wave length, characteristics of beach material (41) and longshore current velocities.…”

Section: Grain Size Analyses Of Sand From Beachmentioning

confidence: 99%

Some Comments on Coastal Engineering

O’Brien

1972

Int. Conf. Coastal. Eng.

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The Canadian Organizing Committee, the Vancouver Executive Committee and the National Research Council of Canada have done a superb job in planning this conference and in carrying out the enormous amount of detail necessary for its realization. On behalf of the Coastal Engineering Research Council, the other participating organizations, and all of the attendees I thank most heartily all who participated in this work. I am personally most grateful to those representatives of the Canadian Committee who made the final selection of papers. I should explain at this point that a small papers Committee is appointed for each of these conferences to review the summaries submitted by the authors - but this screening is intended only to appraise their appropriateness for a coastal engineering audience - and to eliminate those few papers which are promotional "blurbs". It has not been a technical review such as is made for "refereed" technical and scientific journals. The number of papers submitted for this Conference passing this simple review far exceeded the reasonable limits of the program - and for a brief period the Papers Committee faced the new and distasteful task of selection among papers acceptable under past standards. However, the problem was handled by the Canadian Committee - applying a formula which seemed equitable and reasonable. I trust that those affected concur in this judgment.

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Scour of Sand Beaches in Front of Seawalls

Cited by 7 publications

References 2 publications

Formation of sand bars under surface waves

Formation of sand bars under surface waves

Investigation of the safety of seawalls against scouring

Some Comments on Coastal Engineering

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