Journal of Waterway, Port, Coastal, and Ocean Engineering

The last mile of rivers often represents an option worth considering for the development of ports. This is particularly true in coastal areas that are densely developed. The simplest form of a port canal, i.e., boats moored along the banks, is an attractive option for the low investment required and the often acceptable residual wave motion. Some of the major rivers have thousands of boats moored along their banks. The effect of these floaters on the river levels during floods must be taken into account. The authors present a methodology based on the computation of the forces on a single boat or an array of boats that yields a quantification of the effect on the river levels. It essentially provides an iterative procedure for computing the value of the resistance coefficient to be used in hydraulic analysis. Theoretical predictions are satisfactorily confirmed by ad hoc experimental investigation.

This paper effectively summarizes dolos stability results for a slope of 1:1.5 that were obtained from the same flume at the Council for Scientific and Industrial Research (CSIR) laboratory in Stellenbosch, South Africa, over a period of more than 10 years. The initial CSIR investigation into dolos stability was conducted with regular waves and included the effect of packing density, concrete density, storm duration, and waist-to-height ratio. Subsequent investigations into the effect of wave period, armor slope, and waist-to-height ratio were conducted with irregular waves yielding 316 data points. These data formed the basis of the present dolos stability formulas. For establishing the effect of packing density, 286 regular wave results were used. The analysis included the establishment of a relationship between packing density and ultimate displacement just prior to failure. An optimum packing density can be estimated by using this approach together with the change in displacements as a function of packing density. The effect of concrete density on stability as previously established in the same flume was included in the formulas, as was the effect of storm duration. Final stability formulas were compared with those of other researchers for dolosse, tetrapods, cubes, and Accropode (SOGREAH, Echirolles, France).

This study presents the results of an experimental research program dealing with spatial debris motion on a horizontal apron depicting a typical harbor wharf. Accordingly, scaled-down 6.1-m (20-ft) shipping containers were equipped with a novel yet nonintrusive real-time tracking system and motion sensors. The instrumentation allowed for the spatiotemporal tracking of debris specimens moving across the apron while entrained by an incoming tsunami-like broken bore. The system proved its capabilities and accuracy; this was particularly challenging since this was the first time the system was used in water. The experiments involved using various numbers of shipping containers that were either arranged in one layer or stacked in two layers. In addition, the effect of different numbers of container rows was also investigated to study the influence of the overall container count and placement with respect to their longitudinal displacement and dispersion (spreading) across the apron. Linear relationships were derived for both parameters, suggesting potential guidelines for future design efforts and disaster risk reduction and mitigation.

An analysis of tidal current variability is performed over seasonal scales for an 11-year record of estuarine currents at two locations in Tampa Bay, Florida. From 2002 to 2012, bimonthly harmonic analyses were performed on current observations collected near the entrance to Old Tampa Bay and at the Sunshine Skyway Bridge. The resultant tidal constituents and nontidal residual were then correlated with other parameters to determine potential physical forcing. Comparison with local wind data suggests that the land-sea breeze cycle can have significant impact on diurnal tidal current flow. Periods of strong land-sea breeze are found to have up to a 30% increase in K₁ amplitude compared with periods of weak land-sea breeze. Subtidal weather-scale wind forcing with periods from 2 to 7 days demonstrates a strong correlation with nontidal residual flow, likely resulting from both direct wind forcing as well as the modification of along-estuary water-level gradients. Additionally, the M₂ constituent correlates with changes in freshwater discharge and inversely correlated with wind variance. The depth-averaged M₂ current amplitude can increase by more than 10 cm/s during periods of high discharge, representing a roughly 25% increase in the amplitude. The seasonal variability observed significantly impacts the accuracy of tidal current predictions for marine navigation and other uses. Predictions of peak flood or ebb currents can vary by more than 40 cm/s, depending on when observations are collected and when predictions are made.

To determine the drag coefficients of geocontainers dumped from an angle-adjustable bevel installed on the side of a ship, an investigation was conducted. First, the settling equation and formulas for the geocontainer were deduced. Second, a screening experiment was conducted to determine the optimal factor groups with proper settling regularity from a combination of factors, that is, the dimension and filling ratio of the geocontainer, the bevel angle, and the sliding distance. Third, trajectories of the geocontainers were obtained from a regularity experiment under flow conditions with different water depths and flow velocities based on the optimal factor groups. According to the regularity experiment, geocontainers are more likely to rotate in conditions of deep water and high flow velocity, which cause an increase in the horizontal settling distance error. Fourth, a computational model to determine the drag coefficients of the geocontainers was proposed according to results of the experiment. Last, drag coefficients of the optimal factor groups were calculated according to the proposed computational model (C_Dx = 0.3–4.27; C_Dz = 0.84–2.53).

Dredged sediments have been extensively used in various parts of the world for applications related to various infrastructural developmental activities, such as land reclamation, building construction, beach replenishment, habitat restoration, and so on. The vicinity of the megacities to the water bodies and shortage of naturally available raw materials for the developmental activities is mostly responsible for such a paradigm shift from the conventional application of natural resources (soils and rock mass). However, utilization of dredged sediments has largely been constrained because of their heterogeneity and also because most of the earlier studies were site specific; hence, these findings cannot be generalized. This calls for a critical analysis of the outcome of the existing studies related to the application of such sediments based on their comprehensive characterization, in infrastructure development, policies adopted in this context, challenges in terms of handling and disposal, and potential of these sediments to contaminate the ecosystem. As highlighted in this paper, such a critical review of the literature would be mandatory for framing the guidelines in establishing the beneficial usages of the dredged sediments as an artificial resource.

Dike embankments are usually protected using a revetment structure or a grass cover. On German sea dikes, marsh clay (North Sea) and glacial marl or bolder clay (Baltic Sea) are used mainly as erosion-resistant cover materials. The marl is usually covered with a thin soil layer if grass needs to be established. In recent years, more and more institutions have shown an interest in the use of fine-grained dredged materials, sometimes rich in organic matter, as a replacement for the standard materials. In Europe, dredged materials are legally considered as waste once they are taken out of the water body, although only a small proportion is contaminated. The embankments of dikes and levees are subject to heavy attack by water forces; thus, replacement materials need to be able to withstand these forces. Therefore, overflowing tests with turbulent, supercritical flow conditions were performed to analyze the erosion resistance of dredged materials on a full-scale dike embankment. The tests, which were based on a recent standard, show promising results, supporting different studies that state a grass cover is much more stable than usually assumed in embankment design and that the used dredged materials allow a particularly erosion-resistant grass cover to grow. The test method, however, also shows its limitations in investigating slope failure other than surface soil detachment.

To understand the hydrodynamic responses of a bridge tower, which consists of a large round-ended caisson foundation and a diamond-type superstructure, a model experiment at a 1:150 scale was conducted in a laboratory flume. The model was designed to be an elastic structure, which would simulate the dynamic properties of a freestanding bridge tower. Regular waves and the combined action of waves and currents were used as loads in the experiment. The horizontal base shear forces of the foundation and the dynamic responses of displacement and acceleration on the superstructure were measured and analyzed. It is found that the wave current–induced base shear force is approximately equal to the sum of the corresponding wave-induced and current-induced base shear forces. The vibrations of the superstructure are irregular and consist of free vibration at a natural frequency and forced vibration at a wave frequency. The vibration responses driven by the wave currents are slightly larger than those driven by the waves alone, indicating that a forward current does not observably amplify the dynamic responses of the bridge tower.

A mathematical model previously developed based on a tide-averaged approach was extended to evaluate the temporal evolution of dredging-induced turbidity plumes in the far field under oscillatory tidal currents. The transient term ($\partial c/\partial t$) was retained in the governing advection-diffusion equation to predict the temporal evolution of the turbidity plume. An oscillatory tidal current velocity [$u(t)=V+U_0\hspace{0.17em}\text{sin}\hspace{0.17em}(\omega t)$] was assumed in the model formulation to represent the oscillatory tidal current. After being verified against benchmark simulations, the present model was used to simulate the diffusion of the turbidity plume, in particular its approach to quasi-steady state [i.e., when the suspended sediment concentration (SSC) exhibits periodic variation as a response to oscillatory tidal currents] as well as the SSC level at quasi-steady state. Sensitivity analyses were further performed to assess how key dimensionless modeling parameters—namely, the residual-to-oscillatory velocity ratio ($\nu$), Li and Kozlowski’s parameter ($\lambda$), the longitudinal-to-transverse diffusion coefficient ratio ($\alpha$), and the ratio of tide to settling time scale ($\phi$)—affect the model predictions. The model predicts distinctively different turbidity plume behaviors under mean and oscillatory tidal currents, which highlights the significance of incorporating the effects of tidal oscillation to model dredging-induced turbidity plumes in the far field more realistically.