Journal of Waterway, Port, Coastal, and Ocean Engineering

In this study, a more general directional spreading function is developed that allows for asymmetric directional distributions. For multidirectional random waves that approach the shore obliquely over a planar slope, we demonstrate that directional asymmetry is generated due to wave refraction. The asymmetry created by refraction increases with the offshore peak wave direction. The present spreading function is compared to a preexisting symmetric spreading function and is shown to better capture changes in the directional distribution that occur in a refracting, random wave field. Finally, the new asymmetric spreading function is compared to a long time series of wave directional spectra measured at a nearshore field site. The results demonstrate that refraction-induced asymmetry is common in the nearshore and the asymmetric spreading function gives an improved analytic representation of the overall directional distribution as compared to the symmetric function.

We investigate the ability of a 1D fully nonlinear Boussinesq model including breaking to reproduce surf zone waves in terms of wave height and nonlinear intraphase properties such as asymmetry and skewness. An alternative approach for wave-breaking parameterization including roller effects through diffusive-type terms on both, the mass conservation and momentum equations is developed and validated on regular wave and solitary wave experiments as an attempt to improve wave height and left-right asymmetry estimates. The new approach is able to reproduce wave height decay, and intraphase nonlinear properties within the entire surf zone of spilling breakers without requiring temporal evolution of model parameters.

This paper deals with three coastal applications of a 1D model system to represent the nearshore currents. In these applications, comparisons are made with the predictions from 2D and 3D models and field data. The system evaluated is the ISSM (the Interface for SWAN and Surf Models), which was developed as an attempt to develop a simple and reliable coastal circulation model. The nearshore circulation model SHORECIRC was considered as a reference. It is a quasi-3D model that uses REFDIF as wave driver, and combines a numerical solution for the depth-integrated 2D horizontal momentum balance equations with an analytical solution for the 3D current profiles. Three case studies were considered for comparing the models. The first is a plane beach treated as a 1D problem. The other two applications are 2D problems. The first application had mild bottom contours, while the second was characterized by strong bathymetric irregularities. Comparisons are performed between the results of the two models and with the in situ measurements. It was found that, when the angle between the direction of the wave advance and the normal to the shoreline was less than 15°, the 1D surf models can be used with confidence in coastal applications. For larger angles and more complex bathymetric conditions, 2D and 3D models are required.

Airborne bathymetric lidar surveys taken in Florida before and after the severe 2004 and 2005 hurricane seasons show infilling of seventeen dredged nearshore borrow pits. During these seasons, groups of pits captured volumes that were the equivalent of up to four years of net longshore transport, even though only one of the seventeen pits studied was inside the presumed depth of closure. Unsurprisingly, dimensionless infilling increased strongly with the ratio of wave height to pit depth. For open coast pits with large alongshore lengths, cross-shore infilling appeared to dominate over longshore infilling but both processes may be of comparable importance in shorter pits. Infilling of three borrow pits adjacent to ebb shoals was found to be considerably larger than on open coasts. Bathymetric changes in borrow pits occurred at greater depths than on nearby undisturbed profiles. Crude estimates of the long term infilling rates from tropical cyclones indicate that annual infilling volumes may be equivalent to more than one quarter of the expected net longshore transport at some locations. However, the episodic nature of hurricanes means that infilling events will be highly irregular.

A comprehensive experimental program has been carried out in order to assess the characteristics like reflection and transmission coefficients of slotted wave screens formed with a series of horizontally placed circular elements. To assess the effect of partial submergence, four different relative depths of submergence $\left(d_s/h\right)$ 0.25, 0.50, 0.75, and 1.0, where $h=\text{water}$ depth, and $d_s=\text{depth}$ of submergence of the wave screen were tested. The wave screens were subjected to regular waves of normal angle of incidence. Further, the pressures exerted on the individual elements of the wave screen and the chamber oscillations in the case of double screen model are discussed in this paper. The peak pressures on the screen are found to reduce with a decrease in its relative depth of submergence. Empirical equations for the prediction of reflection and transmission coefficients as a function of wave steepness, relative water depth, and depth of submergence of the screen for single and double screens are proposed. Such equations for the pressures on the screens are also reported in this paper.

A key design element in coastal structures is the crest elevation which protects against damages due to overflowing and overtopping. In order to avoid overflowing, the design crest elevation should be above the extreme flood level, which is usually composed of tides and storm surges but could also include tsunami, El Niño, and other climatologic and geologic effects. The extreme flood level may be determined with the annual maxima, simple addition, or joint probability methods (JPM). These methods have various limitations in terms of the amount of required data, the representation of factors contributing to sea level fluctuations, the ability to assess the joint probability of these factors, and the degree of data independence required. To minimize overtopping, the design crest elevation should be above the extreme sea level which is evaluated considering wave runup and the extreme flood level. Wave runup estimates are based on selected extreme flood levels and the extreme wave climate, data for which are often dependent. A modification of the JPM, the direct JPM (DJPM), is developed for estimating extreme flood and sea levels. This method may be applied to consider any number of dependent contributing factors. Data for the City of Richmond, B.C., Canada, are used to demonstrate the DJPM. The DJPM provides an estimate of the extreme flood level for Richmond that is within the same range as those obtained using traditional estimation methods. The results indicate a large difference between extreme flood and sea level estimates. The sea levels at Richmond are also increasing due to climate and tectonic effects. A hybrid direct joint probability-simple addition method is applied to consider these effects.