Journal of Waterway, Port, Coastal, and Ocean Engineering

An experimental study has been undertaken within the U.K. Coastal Research Facility (CRF), located at HR Wallingford Ltd. Detailed measurements were made to examine the on–off shore spreading of a solute, mostly inside the surf zone, for shore normal waves combined with a longshore current. The results show that the on–off shore mixing is significantly increased by almost 70 times, when compared to current-only conditions. A theoretical advection–dispersion mixing mechanism has been postulated. Using suitable estimates for the turbulent diffusion and on–off shore wave-induced velocity, a theoretical approximation to the overall mixing within the surf zone can be obtained. This theoretical analysis suggests that the on–off shore mixing in the surf zone is proportional to $H_b^{3∕2}$ , where $H_b$ is the breaker wave height. It is demonstrated that within the surf zone, the on–off shore mixing is dominated by the effects of the on–off shore velocity. Some previous experimental studies to determine the magnitude of the mixing within the surf zone have been performed. However, the mechanisms responsible for generating the mixing were neither fully investigated nor reported. The previous studies, together with the results obtained from the CRF, are compared to estimates for the theoretical description of mixing developed within this present study. A good agreement exists.

The present study is concerned with the numerical simulation of free-surface wave flows around surface-piercing cylindrical structures using an unstructured grid-based unsteady Reynolds-averaged Navier–Stokes method. The volume of fluid method is implemented with a highly accurate scheme for flux evaluation on cell faces. The computational results are validated against existing experimental data that involve free-surface waves around surface-piercing structures, spilling breaking waves, bubbly free-surface in separated regions, and interaction between free-surface waves and underlying viscous flow. The validation results suggest that the present computational approach provides a tool that is flexible and accurate enough to capture the fundamental characteristics of flow physics associated with the unsteady free-surface wave flows around surface-piercing cylindrical structures.

Equilibrium models for beach morphology can be a useful engineering tool. In practice, conditions are rarely such that true equilibrium is reached or maintained. Nevertheless, equilibrium models have been used successfully in coastal studies, and extended in their application to describe quasi-equilibrium situations where, for example, wave conditions are relatively persistent over considerable periods of time. This paper describes a simple but efficient statistical method to estimate the mean and variance of crenuate shaped bays from the (long term or static) equilibrium according to the measured wave directions. The technique relies on the concept of ensemble averaging. The theoretical development is carried out by considering a sequence of problems of successive generality. Analytical solutions are first tested against results from a numerical Monte Carlo simulation which demonstrates the importance of the shape of the wave direction distribution in defining the variability of the beach position. The analytical solutions are then applied to the embayed beach at Christchurch Bay on the south coast of the United Kingdom. Hindcast wave conditions and a set of beach profile measurements covering a period of approximately $10\text{years}$ are used. Comparisons are limited to three points along the embayment, at which there are sufficient measurements to calculate a variance. Nevertheless, extremely good agreement is found (to within $\sim 10\%$ ) between predicted and measured sample variances of shoreline position.

Dredged harbor mud is being increasingly used as backfilling and construction material in harbor development or reorganization to gain financial and operative advantages compared to disposal or ex situ treatment of the often contaminated material. However, the suitability of such soft organic sediments as construction material is unclear. This study presents geotechnical parameters for describing the one-dimensional consolidation based on large-scale long-term and standard oedometer tests using organic harbor mud from the Osthafen (East Harbor) reorganization project in Bremerhaven, Germany. Determined compression indices $C_c$ are in the range of peat, whereas the water permeabilities resemble those of clay. The coefficients of consolidation $cv$ vary between ${10}^{-9}$ and ${10}^{-8}{\mathrm{m}}^2∕\mathrm{s}$ and large coefficients of secondary compression $C_{\alpha }$ between 0.065 and 0.14 are observed. Differences in parameters from large-scale and standard tests can be explained by volume and time effects likely linked to biogeochemical degredation of organic carbon and the resulting methane degassing. A curve fit based on the Levenberg–Marquardt nonlinear least-squares optimization method confirmed the applicability of the Terzaghi theory in combination with a creep term.

Bridge decks in Escambia Bay were damaged during the storm surge of Hurricane Ivan in 2004. In this study, a numerical wave-load model based on the incompressible Reynolds averaged Navier–Stokes equations and $k\text{-}\epsilon$ equations has been used to investigate dynamic wave forces exerted on the bridge deck. The volume of fluid method is adopted in the model to describe dynamic free surface, which is capable of simulating complex discontinuous free surface during wave breaking and wave-deck interactions. The model was satisfactorily tested against experimental data of uplift wave forces on horizontal plates. The validated model was applied to investigate wave forces acting on the bridge deck in Escambia Bay in the case of Hurricane Ivan. The time history of wave profiles, turbulent velocity fields, and dynamic uplift and horizontal forces acting on the full-scale bridge deck were simulated and analyzed. Results indicate that, during the storm surge event of Hurricane Ivan, the maximum uplifting wave forces were larger than the weight of the simply supported bridge deck, causing direct damage to the deck. Wave forces on three different deck elevations are discussed. Comparisons of numerical modeling results to maximum wave forces obtained from empirical equations are provided as references for coastal hazard assessment and bridge design.

The quantification and monitoring of sediment dynamics in estuaries has received plenty of attention in recent years due to both economic and environmental interests. Numerical models have been widely applied for predicting the morphodynamic evolution of these areas. However, the degree of uncertainty of these models is often very high due to the lack of measurements necessary for a complete model calibration and validation. In this paper, different methods have been integrated to overcome these limitations. The hydrodynamics and suspended sediment transport in the IJzer estuary were estimated by means of field data and with the use of a two-dimensional hydrodynamic model coupled to a morphodynamic model. Tidal pumping was recognized as the main driving mechanism of sediments inside the estuary. Erosion-deposition areas calculated with the numerical model were compared to the locations and volumes of dredged material. Model results and measurements were generally in good agreement. Additional support for the morphodynamic model results came from airborne hyperspectral images acquired in 2001 and 2005.