Journal of Waterway, Port, Coastal, and Ocean Engineering

The working features of innovative coastal defense structures that can dissipate the energy of incoming waves by the action of large-scale bottom unevennesses (rigid blades covering the lower half of the water depth) were investigated by means of a laboratory experimental campaign. The goal of the study was to characterize the ability of the structures to efficiently reduce the wave height with a minimal change in the mean water superelevations. Similar wave height reductions were achieved for both vertical and inclined blades; their efficiency was slightly superior to that of traditional submerged rubble-mound breakwaters of the same cross-shore extension. For the incident waves examined, very low mean water elevations were observed inshore of the structures, with the inclined blades producing the smallest values. These results suggest that the structures analyzed here could represent an alternative to submerged rubble-mound breakwaters from a hydrodynamic point of view to protect coastlines prone to erosion with minimal risk of dangerous rip currents.

A novel modeling approach was used to investigate the residence times of Oyster Cove, an artificial canal system connected to adjacent water bodies by unidirectional and bidirectional flow structures. A field program was carried out to evaluate and quantify the exchange of water through the system of flow structures and to gain an understanding of the mixing dynamics within the artificial canal. Results from the field program were also used to validate a three-dimensional circulation model and a flushing model used to quantify the existing residence time of the canal system. Finally, the model was used to compare several hypothetical design alternatives, to identify the effect on the canal’s residence time, by changing the positions of the flow structures and using different combinations of structures. The comparison showed the significant improvements in residence times that could be achieved.

Rising sea levels and increased sea storminess have resulted in higher frequency of wave overtopping and greater magnitude of hydrodynamic action on coastal defenses. The situation has been exacerbated for reinforced concrete coastal structures due to the seawater induced corrosion of reinforcing steel in concrete which reduces the load carrying capacity of the structure. This combined effect has posed higher risk to the public and necessitated a thorough assessment for coastal structures. The present paper introduces a time-dependent reliability method to predict the risk of failures due to the increased wave overtopping and reduced structural capacity, and some basic applications to illustrate its use. A stochastic process is proposed to model the time variant and random nature of severe waves. Also proposed is a structural deterioration model to allow for seawater induced steel corrosion in concrete. It is found in the example that the rising sea levels and increased sea storminess reduce the safety and serviceability of coastal defenses. The method presented in the paper can provide useful information for structural engineers, operators, and asset managers in developing a risk-informed and cost-effective management scheme for coastal defenses. The timely maintenance of coastal defenses has the potential to prolong their safe service life.

An efficient nonhydrostatic model with the embedded Boussinesq-type like equations at the free surface is presented to simulate surface waves from shallow to deep water. The new free-surface treatment yields an accurate expression of vertical distribution of nonhydrostatic pressure. This approach is free of the irrotational flow assumption. Two locations of reference velocities obtained through interpolations of nonhydrostatic velocities are used to optimize frequency dispersion for a wide range of wave conditions. Accuracy and efficiency of the model is critically tested against analytical solutions and experimental data. Overall, the present nonhydrostatic model using a small number of vertical layers (i.e., 2–4) is capable of resolving dispersive wave motions with various effects.

The purpose of this technical note is to present a new formula to compute the incipient breaking wave properties based on a simplified solution of the wave energy flux conservation equation combined with Snell’s law. The execution time and calculated results of the new formula were compared with those of the iterative method which is commonly used in coastal engineering calculations, including in shoreline response modeling. The new formula could be used instead of the iterative method to save calculation time for application in coastal engineering.