Journal of Waterway, Port, Coastal, and Ocean Engineering

Reef Balls are hemispherical concrete units, which feature hydrogen ion concentration neutralized concrete and specialized surface textures to promote the growth of marine life. Reef Balls can be arranged in different layouts to form submerged breakwaters, even of significant width. Although structures formed with Reef Balls have been used for the protection of several top-quality sites, no well-established design tool exists for the prediction of wave transmission behind them. In this study, a set of equations were proposed based on the conceptual approach. The expressions were validated by more than 300 experimental data from physical model tests conducted at two different laboratories. The new predictive model showed a number of encouraging properties, such as a high determination index, $R^2$, normality of the residuals, and a constant standard error with respect to the structure layout.

Very long one-way traffic (VLOWT) entrance channels have become bottlenecks for China’s seaports. However, the high costs and complexity of channel expansion make it impractical to expand a typical channel to a two-way traffic channel. Therefore, to improve port performance a ships-passing anchorage (SPAC) is proposed, which provides a temporary mooring for lower-priority ships to wait until other ships traveling in the opposite direction pass beyond the SPAC. To explore the feasibility of building a SPAC and to determine its dimensions, the annual average turnaround time, average waiting time, and average waiting time/average service time ratio were chosen as the performance measures of port service. Then, considering randomness and dynamics in ship operations, a model to simulate ships moving in and out of a harbor through a VLOWT channel with a SPAC was developed, and the port performance was calculated. Finally, the proposed model was applied to a cargo-import port with a VLOWT channel. The results show that a SPAC improves port performance and effectively saves dredging costs, and that the simulation model is an efficient tool to determine proper SPAC design.

In some areas, rivers and canals interweave into a network, making inland waterway transportation feasible. Significant losses will occur if a vulnerable waterway (where vulnerability is defined in terms of susceptibility to interference and difficulty in restoring the initial state) that is vital to a network is blocked. System vulnerabilities combined with hazard factors trigger disasters; therefore, reducing the vulnerability of a network system is a useful means of reducing major losses. In this paper, a model to calculate vulnerability based on inherent characteristics of waterways such as channel connectivity, transportation efficiency, and economic cost is developed. Three influence factors—importance, efficiency contribution, and loss—are used to build a vulnerability assessment model in which the relative vulnerabilities of various waterways can be assessed and the most vulnerable waterway can be found. Using this model, a simple waterway network is tested to identify vulnerable waterways.

This paper presents an alternative implementation of the advancing front method for generating two-dimensional triangular unstructured meshes for finite-element applications. After initializing the front along the boundaries, internal fronts, called pseudoislands, are created inside the domain where a node-spacing function condition is met. When the element creation starts, several disjoint fronts are made active, one for each pseudoisland, and the temporal order of creation of the elements follows a smaller to bigger size sequence in an inside-to-outside propagation of the front. Postprocessing routines are available for enhancing the mesh quality. A test case for an idealized geometry shows the effectiveness of the method with high node-spacing function gradients. Several discretizations of a light detection and ranging (LIDAR) derived digital elevation model are compared for demonstrating the improvement of the new advancing front version with respect to the standard version in real applications. Finally, one of the meshes obtained with pseudoislands is used in a wet and dry tide modeling study, showing a superior resolution of the sharp bathymetric gradients and an improvement on the simulation of the wetting and drying process.

A combination of storm surge and extreme waves may cause overtopping of coastal protection structures such as levees, dikes, and seawalls, resulting in structural damage and flooding behind these structures. High turbulence of the overtopping flow is an important or even critical factor in soil erosion, and may be responsible for the destruction of levees during combined overtopping. The goal of this study was to observe and measure the turbulence on the crest and landside of levees strengthened by high performance turf reinforcement mats (HPTRMs). A full-scale laboratory study of the combined wave and surge overtopping of a levee strengthened with HPTRMs was conducted in a two-dimensional (2D) laboratory wave/flow flume. During a total of 11 trials, the authors recorded and processed three-dimensional (3D) velocity and water depth. They developed a new formula to estimate the average overtopping discharge. This paper presents turbulent fluctuations of the three components of flow velocity on the crest and landside slope, and develops formulas to estimate the turbulent intensity. The study used five methods—the log profile method, three turbulent methods (Reynolds stress; turbulent kinetic energy, $k$; and turbulent kinetic energy, $w^{\prime }$), and the Nadal and Hughes method—for the turbulent shear stress predictions on the levee crest and landside slopes. The new formulas developed show that turbulent shear stresses at the middle of the crest, the end of the crest, and the landside slope are functions of the relative freeboard.

The extreme phenomena induced by climate change have generated new interest in analyses of wave runup on beaches. Extreme runup quantification is essential for coastal management and protection against coastal flooding. Several formulations deduced from empirical studies are available for runup estimation, although scattering is high when applied to practical cases. This paper presents the results of a physical model experiment carried out in the Laboratory for Maritime Experimentation at CEDEX on three sand bed beaches with uniform slopes of $1/20$, $1/30$, and $1/50$. The performance of each formulation is discussed with the aim of choosing the best formulations available for coastal engineering. A new formulation is proposed that accounts for beach slope. Choosing the most extreme beach profile prior to a storm reaching the shore in this formulation provides the required model for risk analysis.