Wave Dissipation and Sediment Transport Patterns during Shoreface Nourishment towards Equilibrium

Implementing shoreface nourishment is an effective method to protect sandy beaches. A better understanding of the equilibrium mechanism of shoreface nourishments is necessary for coastal engineering designs and constructions. Two experiments on the beach profile equilibrium of the shoreface nourishment are carried out under mild wave conditions on the reflective and intermediate beach. It is observed that the shoreface nourishment increases local wave height and strengthens wave nonlinearity by its shallow water depth. The most intense wave breaking dissipation has been found on the crest of the shoreface nourishment, and the distribution of wave energy dissipation rate is more uniform on the quasi-equilibrium profile than that on the initial profile. A process-based numerical model is used to reproduce bed profile evolution successfully. On that basis, it is found that onshore bedload transport is the primary cause for the onshore migration of the shoreface nourishment. The magnitude of bedload transport decreases during the evolution of the shoreface nourishment towards equilibrium. The most intense sediment transport rate occurs over the shoreface nourishment or in front of the shoreline, depending on the ’lee effect’ of the nourishment. Furthermore, the effects of incident wave height, wave period, and sea-level rise on the equilibrium profile of the shoreface nourishment under mild wave conditions are analyzed.

Predicting Crenulate Bay Profiles from Wave Fronts: Numerical Experiments and Empirical Formulae

For crenulate-shaped bays, the coastal outline assumes a specific shape related to the predominant waves in the area: it generally consists of a tangential zone downcoast and a curved portion upcoast. Many coastal engineers have attempted to derive an expression of the headland bay shapes that emerge when a full equilibrium is reached (stable or dynamic). However, even though models for static equilibrium bays exist, they are merely of an empirical kind, lacking further insight on relationships between incident wave characteristics and beach shape. In addition, it is commonly believed that shoreline profiles tend to follow wave fronts, but this has been never fully verified. In this paper, we investigate a possible correlation between static equilibrium profiles and wave front shapes. Numerical experiments have been performed using the MIKE 21 Boussinesq Wave module, and the generated wave fronts have been compared to the hyperbolic-tangent equilibrium profile. A thoughtful analysis of results revealed that a single-headland equilibrium profile is merely the wave front translated perpendicularly to the wave direction at the headland tip, without any influence of wave period or in wave direction. A new function called the “wave-front-bay-shape equation” has been obtained, and the application and validation of this formula to the case-study bay of the Bagnoli coast (south-west of Italy) is described in the paper.

Deformations of upper soil slopes of retaining structures and shores with violated reinforced concrete fastening in riverbed reservoirs in Belarus

The conditions of wind waves influence on the ground upper soil slopes of retaining structures and natural shores that are fixed in the form of reinforced concrete fastening with deformations are considered. The results of modeling the regime of intra-water currents and field surveys of artificial water bodies are shown. A criterion for assessing the stability of ground slopes and coastal slopes with reinforced concrete fastening with a broken structure is proposed and the conditions for its applicability are determined. Measures for engineering protection of the reservoir shores are proposed via using a criterion for the stability of fixed slopes Пк. It is assumed that at Пк ≥ 1 the slope profile with fastening plates deformed during operation acquires the contour of the dynamic equilibrium profile adopted for the calculated type of soil as a result of the destruction of the slope by waves.

Numerical Simulation of Scour Depth and Scour Patterns in Front of Vertical-Wall Breakwaters Using OpenFOAM

An advanced coupled numerical model was developed and implemented in the present work, describing the scour patterns and predicting the scour depth in front of vertical-wall breakwaters. It consists of two independent models, a hydrodynamic Computational Fluid Dynamics (CFD) Reynolds Averaged Navier–Stokes (RANS) model developed on the OpenFOAM (version 2.4.0) toolbox (CFD), describing the wave propagation and the associated hydrodynamic field, and a morphodynamic one (sediment transport model), which was developed in FORTRAN by the authors and yields the updated seabed morphology. The method used here is iterative. The hydrodynamic model is applied for any given initial seabed geometry and wave conditions, resulting in the hydrodynamic field of the flow, which is used as input by the second sediment transport model for the seabed morphology evolution. This process is repeated until the equilibrium profile is achieved. Model results are compared satisfactorily with experimental data for both scour patterns and prediction of scour depth.

Metal Removal from Complex Copper Containing Effluents by Waste Biomass of Saccharomyces cerevisiae

Saccharomyces cerevisiae, waste biomass originated from beer fermentation industry, was used to remove metal ions from four copper-containing synthetic effluents: Cu-Fe, Cu-Fe-Ni, Cu-Fe-Zn, and Cu-Fe-Ni-Zn. The characterization of the biomass surface was investigated by Scanning Electron Microscopy and Fourier-transform Infrared Spectroscopy. The adsorption behavior of Saccharomyces cerevisiae for copper, iron, nickel and zinc ions in aqueous solution was studied as a function of pH, initial copper concentration, equilibrium time, and temperature. Langmiur, Freundlich, Temkin and Dubinin-Radushkevich equilibrium models have been assessed to describe the experimental sorption equilibrium profile, while pseudo-first order, pseudo-second order, Elovich and the intra-particle diffusion models were applied to describe experimental kinetics data. Maximum sorption capacities have been calculated by means of Langmuir equilibrium model and mean free sorption energies through the Dubinin-Radushkevich model. Thermodynamic analysis results showed that the adsorption of copper, iron and zinc was spontaneous and endothermic in nature, while of nickel exothermic. Saccharomyces cerevisiae can be successfully applied for complex wastewater treatment.

Beach nourishment versus sea level rise on Florida’s coasts

Beach nourishment and sea level rise will dominate future shoreline changes on Florida’s 665 miles of sandy coast. Shoreline changes from 2020-2100 are projected along this entire coast using equilibrium profile theory that accurately predicted shoreline changes on Florida’s east coast from 1970-2017 (Houston 2019). Projections for 2020- 2100 are made assuming past rates of beach nourishment for the 30-yr period from 1988-2017 will continue and sea level will rise according to recent projections of the Intergovernmental Panel on Climate Change (IPCC) that include the latest knowledge on ice melting in Antarctica (IPCC 2019). Using the beach nourishment and sea level rise data, equilibrium profile theory is then used to predict shoreline change from 2020-2100 for each IPCC sea level rise projection. Beach nourishment is shown to produce shoreline advance seaward on average for all IPCC scenarios for both the entire Florida coast and east coast and for all scenarios except the upper confidence level of the worst scenario for the southwest and Panhandle coasts. Some of the 30 counties on these coasts will require a greater rate of nourishment than in the past to offset sea level rise for some or all of the scenarios, whereas some will offset sea level rise for all scenarios with lower nourishment rates than in the past. The annual beach nourishment volume for which a county has a shortfall or surplus in offsetting sea level rise for each IPCC scenario can be calculated with the information provided and examples are presented. The approach can be used on coasts outside Florida if beach nourishment and sea level rise are expected to dominate future shoreline change.

A Design Parameter for Reef Beach Profiles—A Methodology Applied to Cadiz, Spain

The southwestern coast of Spain is in a tidal zone (mesotidal) which causes the equilibrium profile to be developed in two different sections: the breakage section and the swash section. These two sections give rise to the typical bi-parabolic profile existing in tidal seas. The existence of areas with reefs/rocks which interrupt the normal development of the typical bi-parabolic profile causes different types of beach profiles. The objective of this article is designing an easy methodology for determining new formulations for the design parameters of the equilibrium profile of beaches with reefs in tidal seas. These formulations are applied on 16 profiles to quantify the error between the real profile data and the modelling results. A comparative analysis is extended to the formulations proposed by other authors, from which it is found that better results are obtained with the new formulations.

Deformations Of Fastenings Of Slopes Of Retaining Structures At Technological Purpose Reservoirs

The article presents the data of field, laboratory and theoretical studies, which made it possible to determine that processing, abrasion destruction of natural shores and loose upstream slopes of dams and enclosing structures, takes place on technological water bodies of Belarus - regardless of their economic use - technical, drinking water supply, regulation of runoff, energy, land reclamation, etc. The period of development of the processing process and the formation of the equilibrium profile is divided into a number of time periods (stages). Three stages are distinguished for the conditions of water bodies in Belarus: initial, intense dynamics and attenuation (equilibrium). Based on the data of field surveys of shore protection structures, the current state of various types of fasteners is assessed with the identification of the causes of their destruction and the extent of deformations. It has been established that the most common shore and slope fastenings are fastenings in the form of reinforced concrete monolithic or prefabricated plates. It is determined that the most widespread are the deformations of the fastenings in the form of the disclosure of inter-tile construction, temperature and settlement joints. As a result of opening the joints of the plates, the destruction and washing out of the sand and gravel bed, the formation of hollows and niches in the body of the slope with its subsequent processing, deformation and destruction of the fastening take place. It should be noted that the destruction of the fastening also occurs in stages, and the stages of the destruction of the fastening coincide with the staging of the processing of loose ground slopes. Based on the data of full-scale and experimental laboratory studies, scientifically substantiated criteria for assessing the stability of soil slopes and slopes with fastening by reinforced concrete slabs are proposed, which can be used to predict the state of designed and operated shore protection structures and fastening slopes. An enlarged methodology has been developed for assessing the risks abrasion of coasts and slopes of retaining structures based on the proposed territorial coefficient of abrasion risk, a mathematical factor model of risk based on the fault tree, and also an experimental electronic map of the risks of abrasion for the conditions of water bodies in the Minsk region of Belarus are developed.

A Numerical Model for Offshore Mound Evolution

A numerical model was developed to simulate the evolution of a mound placed in the offshore (i.e., outside the zone of wave breaking), exposed to varying non-breaking waves and water levels. The net sediment transport rate is assumed to be mainly dominated by bed load transport, where wave asymmetry plays an important role. The net transport over a wave cycle is expressed with reference to an equilibrium profile, which ensures model reliability and robustness. In order to validate the model, data collected at two field sites, Cocoa Beach and Perdido Key Beach in Florida, USA, were employed. The numerical results show good agreement with the measured data from the two sites in terms of the profile evolution. It demonstrates that the model has the capability to simulate the evolution of mounds placed in the offshore. In addition, several scenarios with different mound volume and location designs were investigated to indicate potential uses for the model. The results illustrate how the mound evolution is influenced by the volume and location of the mound placement.

Results of engineering geological zoning of Belarus territory by the abrasion risk at water reservoirs in the context of global climate change

The paper shows the reasons for the intensification of risk-forming processes in Belarus caused by "aging" of existing and the arrangement of new water reservoirs. The shores of new reservoirs located in the territory of Belarus, intensively used in the national economy and densely populated, are actively reprocessed by abrasion, leading to the development of abrasion risk. The length of the abrasion coasts has increased by more than 20 km recently, which undoubtedly has an impact on the surrounding areas, causing loss of land and economic facilities. The goal of the work is to update the regional zoning of the country's territory according to abrasive risk, which should be taken into account in the forecast calculations of the sustainable development of regions based on entirely new principles and assumptions. In this work, we used the data of long-term (covering more than 40-year-long period) field observations of the author over the abrasion process and the results of a science-based analysis. We propose (using the failure tree) an abrasion risk development model and indicators characterizing the abrasion risk, taking into account the global climate change and related warming, affecting the dynamics and extent of the process of destruction and deformation of the coast. Based on a theoretical study of the mechanism for forming the dynamic equilibrium profile of abrasion coasts and the equilibrium coastline, a criterion is suggested that characterizes the stability and development of the equilibrium profile of the coastal slope required for zoning the Belarus territory by abrasion risk. Based on the generalization of the observation results for Belarus water reservoirs and the use of the proposed indicators, we performed zoning of the country’s territory by the abrasion risk, which is of practical importance for making management decisions and designating engineering measures to prevent and mitigate risk in water bodies, as well as minimizing their effects.