Journal of Waterway, Port, Coastal, and Ocean Engineering

About 6,300,000 pressure head waves beneath the sea surface were recorded by an array of 26 transducers aligned orthogonally to the coastline of Reggio Calabria, Italy. The data set covered spectra from very narrow unimodal to very broad multimodal and waves from shallow to deep waters. Herein, the quasi-determinism (QD) theory is proven to be very effective in predicting the probability of large-wave heights as well as the period and particle acceleration of these waves both on deep and shallow waters. In addition, the Tayfun model for predicting the probability of large-wave heights is also proven to be highly effective.

The reshaping of temporary rubble mounds such as breakwater cores or reclamation bunds is a concern for maritime contractors. Literature formulas for the prediction of such behavior provide little insight in the influence of the wide stone size gradation of the materials involved. Laboratory tests carried out on model structures built with very wide-graded materials ($D_{85}\text{/}{D}_{15}$ up to 18) showed that increasing the grading reduces the stability of a slope. It was also observed that the steepness of the initial slope has an influence on the reshaping mechanism. Partly based on the Van der Meer formulas for dynamic stability, new formulas that take into account the parameter $D_{85}\text{/}{D}_{15}$ are derived for the estimation of important features of a reshaped slope. The new formulas reflect in a simple mathematical expression the experimental evidence, namely the destabilizing effect of a wider grading and of a steeper initial slope. Thus, they are also suitable to be implemented in new or existing numerical models.

A probabilistic framework is presented for evaluation of hurricane wave and surge risk with particular emphasis on real-time automated estimation for hurricanes approaching landfall. This framework has two fundamental components. The first is the development of a surrogate model for the rapid evaluation of hurricane waves, water levels, and run-up based on a small number of parameters describing each hurricane: hurricane landfall location and heading, central pressure, forward speed, and radius of maximum winds. This surrogate model is developed using a response surface methodology fed by information from hundreds of precomputed, high-resolution Simulating Waves Nearshore (SWAN) + Advanced Circulation Model for Oceanic, Coastal and Estuarine Waters (ADCIRC) and One-Dimensional Boussinesq Model (BOUSS-1D) runs. For a specific set of hurricane parameters (i.e., a specific landfalling hurricane), the surrogate model is able to evaluate the maximum wave height, water level, and run-up during the storm at a cost that is more than seven orders of magnitude less than the high-fidelity models and thus meets time constraints imposed by emergency managers and decision makers. The second component of this framework is a description of the uncertainty in the parameters used to characterize the hurricane through appropriate probability models, which then leads to quantification of hurricane risk in terms of a probabilistic integral. This integral is then efficiently computed using the already established surrogate model by analyzing thousands of different scenarios (based on the aforementioned probabilistic description). This allows the rapid computation of, for example, the storm surge that might be exceeded 10% of the time based on hurricane parameters at 48 h from landfall. Finally, by leveraging the computational simplicity and efficiency of the surrogate model, a simple stand-alone PC-based risk-assessment tool is developed that allows nonexpert end users to take advantage of the full potential of the framework. The proposed framework ultimately facilitates the development of a rapid assessment tool for real-time implementation but requires a considerable upfront computational cost to produce high-fidelity model results. As an illustrative example, implementation of hurricane risk estimation for the Island of Oahu in Hawaii is presented; results demonstrate the versatility of the proposed approach for delivering accurate tools for real-time hurricane risk estimation that have the ability to cross over technology adoption barriers.

This paper describes an investigation of vortex-induced vibrations in a submerged floating tunnel (SFT) system. A theoretical model for coupled tube-cable vibration was developed to evaluate the SFT structural dynamic response to water current. The differential equations of the cable and tube coupled motion were derived using the Hamilton principle, and approximate numerical analyses were carried out to determine the coupling effect between cable transverse vibrations and tube vertical vibrations. The results showed that the maximum amplitudes of the cables were greater than the initial disturbance when self-induced resonance occurred. Self-induced resonance can be caused by the vortex-induced vibration of the cables when the flow velocity reaches a certain value. The change in the tube-specific gravity ratio had little effect on the maximum vibration amplitudes of the tube and cables. The vibrations of the tube and cables were more sensitive to changes in the lift coefficient than to the added mass coefficient or the drag coefficient. The coupling effect of tube-cable vibration should be weaker with smaller cable angles; after careful consideration, a reasonable choice of angle for the cables was determined to be 45°.

The mean and turbulence properties of a turbulent buoyant jet discharged at middepth in a direction opposite to the wave propagation direction are experimentally investigated using particle image velocimetry. Three kinds of effluent jets are employed for examining the effects of buoyancy on the interactions of a horizontal round jet in both the jet’s potential core region and the self-similar region with regular waves. By comparing the buoyant jet in a stagnant ambient environment and a wave field, the experiment demonstrates that the widths of the positive and negative jets increase significantly because of the buoyancy effect and the wave dispersion effect—a clear indication of enhanced jet diffusion. As expected, the turbulence intensity and Reynolds stress of the buoyant jet is also significantly influenced when the jet is acted upon by waves. To quantify this influence, the eddy viscosity is calculated on the basis of the measurements. An examination of the buoyant jet’s energy budget shows that when the jet is under the waves, its mean kinetic energy decreases while its turbulent kinetic energy increases, indicating an increase in turbulence production. By examining the near-field property, it is found that the turbulence production, advection, and dissipation terms of the buoyant jet under waves are greater than those of a buoyant jet in a stagnant environment, owing to the greater interaction between the buoyancy effects and the water waves near the free surface.

Everglades restoration activities may cause changes to temperature and salinity stratification at the Port of the Islands (POI) marina, which could affect its suitability as a cold weather refuge for manatees. To better understand how the Picayune Strand Restoration Project (PSRP) may alter this important resource in Collier County in southwestern Florida, the USGS has developed a three-dimensional hydrodynamic model for the marina and canal system at POI. Empirical data suggest that manatees aggregate at the site during winter because of thermal inversions that provide warmer water near the bottom that appears to only occur in the presence of salinity stratification. To study these phenomena, the environmental fluid dynamics code simulator was used to represent temperature and salinity transport within POI. Boundary inputs were generated using a larger two-dimensional model constructed with the flow and transport in a linked overland-aquifer density-dependent system simulator. Model results for a representative winter period match observed trends in salinity and temperature fluctuations and produce temperature inversions similar to observed values. Modified boundary conditions, representing proposed PSRP alterations, were also tested to examine the possible effect on the salinity stratification and temperature inversion within POI. Results show that during some periods, salinity stratification is reduced resulting in a subsequent reduction in temperature inversion compared with the existing conditions simulation. This may have an effect on POI’s suitability as a passive thermal refuge for manatees and other temperature-sensitive species. Additional testing was completed to determine the important physical relationships affecting POI’s suitability as a refuge.

In Japan, the probability of a Tokai, Tonankai, and Nankai earthquake occurring in the early 21st century is high. Given this likelihood, estimating the resulting tsunami in real time is desirable. This study details an inversion method for real-time tsunami predictions using only observed offshore tsunami data. Numerical experiments demonstrate that (1) the tsunami wave source is estimated fairly well using the inversion method compared with the initial sea surface displacement calculated from the earthquake fault model; (2) the tsunami profiles are predicted with great accuracy at coastal locations of interest; and (3) the profiles are accurately and easily updated using a longer duration of observed tsunami data after an earthquake. This study also investigates techniques to improve the accuracy of the forecasts: screening optimal locations for offshore global positioning system (GPS) buoys, using a longer period of observation data, and decreasing the duration of the tsunami prediction. These techniques illustrate the practical application of this method for tsunami forecasting.

An adaptive hydraulics (AdH) model was applied to lower Knik Arm near the Port of Anchorage, Alaska, to assess its ability to model a macrotidal system with complex hydrodynamics, including the formation and evolution of numerous gyres that are prominent at this site. Lower Knik Arm is an ideal system for this model evaluation because of the large tide range (approximately 10 m at Anchorage) and complex geometry of the system, which results in high velocities and the formation of numerous eddies throughout the study area. One eddy of primary importance is the one generated by Cairn Point, which occurs near the Port of Anchorage. Limitations of previous modeling studies and the availability of recent field data enabled this evaluation. The AdH results were compared with field data (water surface elevations, fluxes, and velocities) collected in August of 2002 and 2006, and favorable comparisons obtained for tidal amplification and eddy generation indicate that AdH reasonably reproduces the complex hydrodynamic conditions in lower Knik Arm. Simulations were also performed to investigate the importance of eddy viscosity specification, frictional specification, and bathymetry on the generation/evolution of eddies present in the system. Upon completion of the model validation, simulations were performed with modified Cairn Point configurations to investigate the impact to the eddy generated at the port. These results illustrate the variation in eddy generation through lengthening, lowering/reducing, or raising Cairn Point.