Journal of Waterway, Port, Coastal, and Ocean Engineering

The major features of tidal basins, such as tidal flats, tidal channels, intertidal areas, and tidal prisms, can be formulated through empirical relations based on field observations. Although empirical relations can explain some morphological patterns, they may not be applicable to all conditions. In some areas and geophysical conditions, empirical relations are not comprehensive and have limited validity because of the lack of observation data. Because of recent advances in the development of numerical models, long-term morphological process-based models are now able to simulate the morphological behavior of tidal basins. This study involved observation of tidal basin morphology. A numerical lab was established for the Musa Tidal Basin (MTB) to guarantee the authenticity of the modeling under various conditions. The aim was to evaluate the effects of morphological parameters on tidal basin equilibrium. Statistical methods were used to investigate the effects of parameters and their interactions with enough accuracy to provide a quantitative explanation of the effects of the parameters and to avoid qualitative justification. The simulations of the MTB applied a range of major parameters, including cohesive material amounts, available sediment volume, and sediment size and composition. Because computation time is a considerable challenge in long-term models, scenarios were designed to optimize the number of runs needed to assess the morphology according to parameter values and to reduce computational cost. Responses were then analyzed to define the comprehensive effects of those parameters on the simulated morphological equilibrium. The method thus involved a combination of realistic and deterministic approaches. Application of this methodology led to improved long-term results in different conditions, as confirmed by a comparison of the output and measured data.

As a result of damage from the 2010 Chile and 2011 Japanese teletsunamis, tsunami risk to small craft marinas along the West Coast of the United States has become an important concern. This paper outlines an assessment tool that can be used to quantify the tsunami damage potential in small craft harbors. The methodology is based on the demand and capacity of a floating dock system and uses a Monte Carlo framework to address the uncertainty of input parameters. Detailed numerical modeling and damage calibration data from recent tsunamis are used to benchmark the approach. Results are provided as fragility curves and give a quantitative assessment of survivability. This tool yields an indication as to the survivability and/or failure of a floating dock system of vessels and floating components/piles subject to tsunami events. The objective of the presented effort is to quickly evaluate whether a floating dock is likely to survive or be destroyed by a particular tsunami scenario.

Coastal vegetation is capable of mitigating tsunami damage. Yet, the complex tsunami dynamics induced by spatial variability of onshore vegetation are not well understood at present. Laboratory and numerical investigations were conducted to study the impact of patchy vegetation on tsunami dynamics. Roughness patches composed of various cylinder numbers and spacings represented different bulk vegetative conditions in the experiments, and a Boussinesq model was applied to extend the range of the experiments. Analysis revealed that roughness patches reduced the maximum momentum flux by up to 80% over most areas, whereas within-patch roughness variation induced uncertainty on hydrodynamics adjacent to the seaward patches. Dimensional analysis revealed a logarithmic relation between the area protected from extreme momentum flux and the total roughness area. These findings demonstrate that patchy vegetation, with appropriate configuration, can be as effective as a continuous forest belt in mitigating tsunami hazards.

Advancement of technology has improved the efficiency of marine trading activities through use of vessels equipped with twin propellers instead of a single propeller. The progression from a single propeller to twin propellers will certainly increase occurrences of scour unless protection measures are studied and designed accordingly. An experiment to model a ship’s twin-propeller wash was conducted on a flat noncohesive soil bed for observation of scour. The asymptotic scour profile was defined in the following four stages: (1) initial, (2) developing, (3) merging, and (4) asymptotic. An equation is proposed to relate the densimetric Froude number, clearance ratio, and reference time scale to the predicted maximum scour depth and area. The predicted equations were found to be highly correlated with the observed parameters.

Vortex-induced vibration (VIV) of an elastically mounted rigid circular cylinder in an oscillatory flow is investigated by three-dimensional direct numerical simulations (DNS). The cylinder is allowed to vibrate only in the cross-flow direction. The main aim of the study is to investigate the correlation between the vibration, the lift coefficient, and the vortex shedding flow. The three-dimensional Navier-Stokes equations are solved using the Petrov-Galerkin finite-element method for predicting flow, and the equation of motion is solved for predicting the vibration of the cylinder. Simulations are carried out with a Reynolds number ($R$) of 500, Keulegan-Carpenter (KC) numbers of 10 and 20, and reduced velocities (V_r) in the range of 2–16. The dominant frequencies of the displacement and lift coefficient synchronize for both KC values when V_r is small. For KC = 10, the frequencies of the vibration and the lift coefficient deviate from each other at large V_r values. The cylinder vibrates at a frequency that is a multiple of the oscillatory flow frequency and is close to the natural frequency measured in water. For KC = 20, where the lift coefficient has multiple frequencies, the intermittent change of the vibration frequencies is observed at large reduced velocities. The number of vortices shed from the cylinder is increased by the vibration of the cylinder compared with the case of a stationary cylinder. Extra vortices are shed from the cylinder after flow reversal, and they do not significantly affect the overall vortex flow pattern because they are very weak.

This study addresses the dynamics and navigability of fluid mud by considering the implementation of a nautical-bottom approach using a combination of several measurement techniques. The Port of Santos (Brazil) was used as the study area. In situ measurements were obtained using acoustic equipment, and direct observations were made through density profiles. Sediment sampling was also performed for grain size and rheological testing. The acoustic data indicated the presence of fluid mud in the inner portion of the canal. In this region, high spatial variability was found, where the fluid mud layer thickness ranged from a few centimeters to nearly 1 m, depending on the sand content. In addition, differences of up to 1 m were observed during the tidal cycle. The rheological tests revealed an increase in the yield stress toward the inner portions of the port. Coupling the density profiles with the rheological data allowed the estimation of a potential draft increase of up to nearly 1.5 m, depending on the location, nautical depth criterion, and tide condition.

Submerged berms are an increasingly used coastal defense structure for beach nourishment because of their eco-friendly nature. A beach-nourishment project that included sand placement on the beach and in the nearshore area as a submerged berm was carried out in the winter of 2010 on West Beach in Qinhuangdao, China. West Beach is a low-energy beach characterized by small wave heights, a small tidal range, and low tidal-flow velocities. An analysis of the postnourishment beach profile evolution was conducted based on beach profile surveys from 2011 to 2014. The analysis showed that the most active parts of the profiles were the berm and the submerged berm, whereas the remaining parts of the profiles remained relatively stable. The cross-shore profiles of the submerged berm evolved significantly from roughly symmetrical shapes to asymmetrical shapes, which can be explained by applying the concept of equilibrium wave-energy dissipation per unit of water to a low-energy beach with a submerged berm. Empirical orthogonal function analysis was conducted on the beach profile surveys, which confirmed the features of the background-berms pattern gained from the evolution analysis. The first three eigenfunctions corresponded to the mean beach profile, the volume changes of the berm and the submerged berm, and the change in the submerged berm from roughly symmetrical to asymmetrical in shape, respectively. Finally, a new equilibrium beach profile (EBP) form was developed to represent low-energy sandy beaches with submerged berms. The findings in this paper contribute to the understanding of cross-shore beach morphodynamics and can provide a reference for beach nourishment under similar conditions.

The risk of flooding in coastal zones is expected to increase due to sea level rise and economic development. In larger bays, estuaries, and coastal waterways, storm surge barriers can be constructed to temporarily close off these systems during storm surges to provide coastal flood protection. Worldwide, 18 storm surge barriers have been constructed thus far, but they are increasingly being considered as a future solution for other coastal locations. This study provides a systematic overview of existing storm surge barriers. It analyzes information about the main functions of each barrier, the type of gates used, and the associated costs. It also shows that functional requirements determine the design and layout of the barrier. The main design challenges are discussed. The study results may be of use in future planning and preliminary storm surge barrier design.

Experimental investigations were carried out to assess the wave reflection characteristics of slotted vertical barriers with an impermeable rear wall. This study was carried out to investigate whether these barriers can be used instead of sloped rubble mounds, which occupy a significant area in ports/harbors/marinas, for wave energy dissipation. Thirty-seven different wave barriers (1 vertical wall, 6 different sloped breakwaters, and 30 slotted vertical barriers with porosity in the range of 10–50% and 1–6 slotted barriers) were tested in random wave fields of the JONSWAP spectra in different combinations of significant wave heights and peak periods. For relatively long waves (water depth/wavelength ratio of d/L_p > 0.2), the performances of many combinations of slotted vertical barriers were much better than those of the conventional sloped rubble-mound breakwaters. The results of this study show that by increasing the number of porous walls from one to six, it is possible to reduce the value of the reflection coefficient from 0.9 to 0.3, especially for a d/L_p greater than 0.2. Also, the results show that for a d/L_p less than 0.2, increasing the number of porous walls did not significantly reduce wave reflection. Overall, these results suggest that slotted barriers can be a good alternative to sloped rubble breakwaters for ports, harbors, and marinas, especially in places where good-quality stones are expensive. In addition, this solution helps increase the effective use of space inside the harbor better than do sloped rubble-mound structures.