Journal of Waterway, Port, Coastal, and Ocean Engineering

Based upon the Mellin Transformation technique, a probabilistic model of wave forces on cylindrical pile is developed which incorporates the random nature of wave property as well as the uncertainty of force coefficients. The solutions have the advantage that all the moments of the probability distributions can be determined exactly. In addition, the solutions are simple and can accommodate a wide range of distribution functions. Specific types of distribution functions are proposed for the wave properties and the force coefficients. Solutions are then obtained for both the inertia force and the drag force on the basis of these distribution functions. The effect of the randomness of the input parameters and the statistical significance of the resulting wave forces are examined.

Similitude relationships for the physical modeling of coastal dune erosion in movable‐bed models are developed based on consideration of the inertial forces, represented by the turbulent shear stress, and the gravity force in the nearly horizontal direction of the principal flow. This results in a dynamic scaling relationship for a distorted model. By requiring similarity of the dimensionless fall velocity parameter between the prototype and model and combining this criterion with the dynamic scaling, the necessary model distortion is derived. The main difference between these relationships and previous modeling laws is in the hydrological time scaling which is also distorted. The derived similitude relationships were verified by reasonable reproduction of the dune erosion which occurred during a prototype event. The model tests included a time‐dependent storm surge hydrograph and an increasing wave height as the storm progressed. It is concluded that the model verification has been successful in at least one instance where prototype data were available, but further verification is desirable as prototype data become available.

The performance of two single degree‐of‐freedom systems—the heaving vertical circular cylinder and the vertical oscillating water column—are theoretically studied. The systems are optimized by using impedance‐matching at the design frequency. This frequency is that of the peak of the wave energy spectrum in a wind‐generated sea. The results show that the optimized system acts as a strong antenna, attracting significantly more wave power than is incident in its body dimension. As the diameter of the system is increased the draft of the device is decreased. Thus, there is a size limit for each design sea. Furthermore, there is also a lower limit of the diameter of the device operating in restricted waters. Because of the strong antenna effect, relatively small systems can be effectively used, making the optimized wave energy conversion system cost effective.

Sedimentation processes in our nation's waterways and harbors are controlled by a complex array of physical and chemical factors that are known only in general terms. Evaluation of hydrodynamic processes and identification of null points are the most useful methods in predicting shoaling in navigation channels. Physicochemical processes controlling sedimentation are complex interactions of suspended solids and water chemistry which are in the early stages of infancy in respect to our understanding and interpretation. While significant advances in understanding of sediment transport phenomena have occurred in the last several years, much remains to assemble this information into a coherent fabric that allows it to be applied toward reducing maintenance dredging. Maintenance dredging to sustain navigation channels annually involves removal of more than 350 million cubic yards of shoaling materials in our waterways. This paper presents an integrated view of the shoaling processes.

The joint probability method is modified to extend its application to flood level frequency determination for barrier island systems. The method developed accounts for the physical mechanism of barrier overtopping and is more economical than a direct statistical approach. The method involves an investigation of the dependency of hurricane surge at locations at and behind the barrier island chain on central pressure depression as well as the dependency of total stilled water elevation on astronomic tide and hurricane surge. To complete the method, a convolution approach for combining astronomical tide and hurricane surge consistent with overtopping and valid for large tidal ranges is presented.

Small sample size and high sample variability go hand in hand in statistical analyses. In this study, the uncertainties in extrapolations of wave heights from small‐size samples to large return‐intervals are investigated and results are obtained for cases where wave statistics are expressed by the Weibull distribution. A nondimensional error for prediction of rare events corresponding to any required confidence level is derived as a function of the number of years of observations, frequency of observations and wave climatological characteristics. It follows that the number of years of wave measurement necessary to determine an extreme event of high return‐interval within a certain confidence level and accuracy can be established. The study shows that shortterm wave measurements of a few years are not sufficient for engineering accuracy, and can be used only to verify or complement wave height estimation given by other methods such as hindcasting. Wave measurement programs have to be conceived as a long‐term investment and commitment for future generations.

A preliminary appraisal is made of the potential hydraulic forces, particularly pore pressure forces, that may be applied to the toe zones of large exposed breakwaters. In particular the stability of the perched toe zone of the Port Sines breakwater is considered. It is recommended that much more research be applied to such breakwaters, whose main armor does not extend fully down to the sea-bed.

An analysis method is presented to study the shoaling patterns in enclosed or semi-enclosed water bodies. The area of water body below a given depth is plotted as a function of depth. A comparison of two such curves plotted for two different surveys provides information on the depths in which sedimentation is occurring and those depths in which scour is occurring. An example application of the analysis method is made using hydrographic survey data available for Mill Cove on the St. Johns River, Jacksonville Harbor, Florida.

The trajectory of a water particle in an oscillatory wave field has been studied by following the movement of the particle. The particle position at the end of each small time increment is calculated using the Eulerian velocity specifications. The results show the path of water particle is not a closed orbit and the calculated mass-transport velocity is in general agreement with Storkes formula. For the second-order waves, the present results demonstrate a much smaller mass-transport velocity than that predicted by the Storkes formula. In addition, the present study shows that a water particle does not return to the initial depth level at the end of each wave period. Instead, it moves in an oscillatory nature in the direction of wave propagation at a period much longer rate than the water waves.