Journal of Waterway, Port, Coastal, and Ocean Engineering

Improved stability formulas for rubble‐mound breakwaters are developed. These formulas for the design of the required weight of the armor units in the cover layer reflect the complex phenomena and take into account the most important parameters affecting the stability. The influence of the wave climate, the difference between the angle of repose and the slope angle, the density of the block material and the fluid, and the permeability of the underlayers are involved. The weight of the armor units under no‐damage conditions is in this way determined. The method may be a contribution to a better understanding and explanation of why some rock‐fill breakwaters have recently failed.

The longshore sediment transport along the coast is investigated by use of detailed sediment transport models in the surf zone. Combined with a detailed description of the wave height and longshore current distribution in the surf‐zone, the littoral drift along the coast is calculated and presented in dimensionless diagrams for coasts with constant slope. The paper further analyzes the transverse distribution of the longshore sediment transport on a coast with bars. The last case is compared with field measurements.

A predictive model of hurricane wind waves is based on the radiative transfer equation and a directional frequency spectrum description of the sea state throughout the solution field. Propagation, refraction and shoaling are accommodated by ray kinematics. The physical processes contributing to wave growth, interaction, and decay are represented by state‐of‐the‐art descriptions. The numerical algorithm is a fractional step method, combining the method of characteristics for a propagation step with a local analytical solution for a forcing step. Predictions under steady, uniform wind conditions are consistent with a simpler parametric model based on the JONSWAP data. The predictive potential of the model for hurricane wind waves is confirmed by comparison with field data from Australia's North West Shelf.

A collision of a large floating ice feature—ice island, iceberg, or multiyear ice floe—with a massive gravity‐type offshore structure in the transition zone of the northern arctic seas during the open water period presents an important engineering problem. In many cases, the ice load developed during the impact affects the design and governs the overall stability of the structure. Though the problem has been recently addressed in a few publications, where it was considered from both deterministic and probabilistic viewpoints, it is still far from being solved. The main objective of this paper is to provide criteria to assess the ice load developing during the impact. No aspect related to the probability of occurrence of the collision is addressed herein. The theory is based on a fundamental classical approach and provides simple criteria for assessment of kinetic energy of the ice feature, the extent of indentation of the structure into the ice, and the global ice load generated by the impact. All results are presented in a closed analytical form convenient for practical engineering applications.

An integral‐equation method is used to investigate the three‐dimensional hydrodynamic interactions between two barges freely floating in waves. The results show that end effects are important even when the barges are displaced longitudinally by a ship‐length. Furthermore, the motions of the leeward barge can sometimes significantly exceed those of the seaward vessel. An analysis of possible practical applications of the method, together with the limitations of the underlying theory, is presented.

The economics of using coastal structures to retain sand on a beach in conjunction with beach nourishment is presented. As the cost of suitable beach sand increases it becomes more economical to include structures in a project if those structures increase the residence time of the sand on the beach. Expenditures that can be justified to provide structures depend on how long the structures extend the sand's residence time and on the prevailing interest rate. Results are presented graphically for perpetual nourishment projects for the case of a constant erosion rate (a constant rate of sea‐level rise). A correction factor to consider finite lifetime projects is also presented. For the, case where the rate of sea‐level rise continues to increase (as has been projected by several recent studies) perpetual nourishment becomes impossible since the time between successive renourishments decreases. However, nourishment projects with finite lifetimes can be evaluated to establish justifiable structure costs.

Jacket‐type offshore structures could be deployed in increasingly deeper waters by optimizing their dynamic characteristics. Decreased wave drag area, platform mass and increased structural stiffness are the key characteristics. Jacket geometries should also be selected so that fabrication, transportation and installation costs could be minimized.

The directional spectrum of short-crested waves in a model tank can be readily obtained from the spatial covariance function of the surface elevation. A convenient method to measure this function is based on a deployment of a set of conventional wave gauges mounted on a straight beam oriented sequentially in a number of directions. The measurements are thus obtained in a system of polar coordinates. An analysis method is presented here which remains in the polar domain. It is more accurate and cheaper than the conventional cartesian analysis.

This study is related to the propagation of normally incident water waves past a submarine trench with a rectangular cross-section. The primary objective is to investigate the kinematics of the flow within and near the trench with the motivation for the work being the aging of dredged navigation channels. The effects of the wavelength and the channel geometry are apparent on the reflection and transmission characteristics of the trench relative to that in the incident progressive wave. There appears to be a sensitivity of the trench kinematics to the wavelength which may be similar to resonance in a rectangular basin.

Transmitting lateral boundary conditions are derived for application to unidirectional wave trains in the parabolic equation method. A form of the condition is derived which is numerically exact for situations where Snell's law holds, and solutions for shoaling and refraction preserve the exact solution of the governing equation.