Journal of Waterway, Port, Coastal, and Ocean Engineering

The present paper describes the measurement of regular wave reflection. Three methods involving the use of two and three fixed probes are described and developed so as to provide explicit solutions for the incident wave height, reflection coefficient, and the phase of the reflected wave train. Extensions of the methods to the case of oblique wave reflection are described. A comparison is made of the range of application and accuracy of the methods. A method involving a least‐squares fit to measurements from three fixed probes is found to be the most accurate, whereas a method involving three height measurements is found to be generally unsuitable except under certain conditions. For methods involving the use of three probes, recommendations are made for the relative probe spacing so as to avoid conditions at which the methods fail or become inaccurate.

The stability of a cubic armored breakwater head and trunk under monochromatic wave trains is experimentally studied. For the head there is a sector, roughly of 60°, where the unit stability is minimum. The stability function values (similar to Hudson's number) are 1.3‐three times higher there than those obtained from biodimensional tested sections. Head shape, at least for the cases tested, does not exert significant influence on the head stability. Trunk sections tested under long crested waves with a standing longitudinal wave height variation (here called quasi‐three‐dimensional [3D] tests) are less stable than two‐dimensional (2D) tested sections. Furthermore, trunk and head sections show a different behavior as the damage grows; the radio of initiation of damage wave height to destruction wave heights is much lower for head than for trunk sections. Head sections are more brittle than trunk sections. Additionally, exploration was carried out into standing longitudinal variation of wave height along the breakwater induced by different factors, such as the reflexion of the scattered waves on the lateral boundaries. Data from prototype failures that have occurred in Spain suggest that these wave patterns are worthy of further research.

Development of information regarding the hydraulic characteristics of tidal inlets plays an important part in evaluating the safety of navigation and inlet stability. The assembled information is also useful since the design of navigation improvements must be directed towards the goal of reducing the volume of maintenance dredging and improving the navigation safety. Extensive data sets obtained from aerial photography over the past 30 years by the U.S. Corps of Engineers were used to study the relationship between hydraulic variables and its stability. This research concentrated on developing relationships between selected inlet characteristics, inlet width and inlet length, and inlet stability for 51 U.S. tidal inlets.

When hopper dredges are used in fast‐moving waters relatively far from a dredged‐material disposal site, dredging managers must decide whether to dispose of the material by either hauling the material to a disposal site or resus‐pending the material. Hauling the material to a disposal site decreases the time available for dredging and consequently increases the total time required to dredge a given volume. Disposal of the dredged material by resuspension increases the time available for dredging at the site, but may increase the amount of dredging required downstream. This paper examines the trade‐off between these two strategies using a simple time‐and‐motion model.

A model based on the analytical solution of an advective‐diffusion equation is developed to describe the turbidity plume induced by the operation of a bucket dredge. The model applies to the portion of the plume beyond the initial mixing zone where the separate patches of suspended sediments have coalesced into a continuous plume. It predicts the vertical average suspended sediment concentration within the plume as a function of the source strength of suspended sediment, the characteristics of the ambient flow field and the effective particle settling velocity. Four sets of field data from previous studies are compared with the model. It is shown that the model describes the qualitative feature of prototype data and that the calibrated model parameters agree with independent observations.

This paper describes a study of alongshore sediment transport rate based on three‐dimensional hydraulic model experiments performed with regular and irregular waves. Deep‐water wave conditions, wave heights through the surf zone, wave‐breaking angles, longshore current velocity distribution, and the bed‐load and suspended‐load sediment transport distributions are measured simultaneously to form a coherent data set. An expression is developed linking sediment transport rate to wave steepness, beach slope, relative grain size, and breaking angle. The expression compares well with published field data.

This article explores the issue of drag-force approximation through the examination of dimensionless spectral wave-force ratios. These dimensionless ratios were developed in an attempt to clarify when third-order approximations to the spectral drag force could be expected to significantly contribute to the predicted wave force. They represent ratios of the spectral wave force per unit length for rigid cylindrical elements. It was found that for low period values, those around the natural period of fixed offshore platforms, the magnitude of the third-order correction to the drag-force spectrum can be a significant percent of the first-order approximation. At higher periods, those in the range of deepwater or compliant platforms, the drag force dominates the total wave force and the magnitude of the third-order force contribution is significant. This finding is consistent with studies addressing the analysis of offshore platforms presented in the current open literature. Finally, changing the Keulegan-Carpenter number strongly influences the magnitude and the location of the low-period peak associated with the third-order drag-force term. Thus, for high $N_K{}_C$ and low $H_s$, the third-order drag force could become an important consideration in wave-force computations.