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Lee, S.-Y.; Kim, D.-H.; Kim, D.-S.; Kim, H.-J.; Jeong, Y.-H.; Hong, S.-J., and Lee, H.-Y., 2021. Applicability of disaster scale criteria for swell-like waves based on wave overtopping predictions. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 226–230. Coconut Creek (Florida), ISSN 0749-0208. In this study, a wave overtopping prediction system was established for 10 major ports adjacent to 10 testbeds in South Korea, and a qualitative assessment of the system's reproducibility was performed through field surveys. The system estimates the probability of wave overtopping hazards, which is required for responding to disasters caused by swell-like waves. Wave overtopping prediction requires information on artificial structures in the major ports near the testbeds, swell-like wave predictions, and wave overtopping rate calculations. The threshold for defining wave overtopping hazards that can affect the hinterland, facilities, and residents in coastal areas was set to 0.01 m3/s/m, in accordance with EurOtop standards (Pullen et al., 2018) and the Korean Ministry of Oceans and Fisheries. The results of this study can be used to facilitate decision-making by providing qualitative estimations of wave overtopping hazards at various levels. By comparing the results to standard values, the risk of swell-like waves in testbeds along the East Sea coast can be determined. The proposed system can be used to avoid casualties and property damage in the event of a wave-overtopping disaster.

Coastal managers worldwide must prepare for changes in annual wave overtopping events due to climate change and sea-level rise. Research often assesses overtopping discharges by extreme events at a sea wall crest, typically using data from physical models or empirical rules based on scaled experiments. Here, we analyse a unique 1-year field dataset of coastal wave overtopping, from SW England, to determine the number of individual waves, regardless of their size, overtopping two locations across a coastal structure. The coastal conditions causing the most frequent overtopping differ from those driving it landward, complicating hazard communications for multiuse infrastructure. These data are the first field observations covering a year of tide, wave and wind conditions that cause overtopping of a vertical sea wall. Storms have a minimal (<2%) contribution to the number of tides associated with overtopping and the prevailing wave direction was not that associated with most overtopping events. Overtopping histograms identify the variability in the most likely time of overtopping relative to high tide for different wave categories across the structure. Sea-level rise, beach lowering and climate change will influence the annual number of waves overtopping in future. Change will be a complex balance between overtopping by different wave categories due to their likelihood of coincidence with water levels that do not cause depth-limitation over the foreshore or (partial-)reflection off the structure. It is possible the number of waves overtopping will reduce at the crest of a sea wall, while more of those overtopping waves will travel further inland.

The safety of pedestrians on a breakwater structure or seawall is significantly influenced by two essential factors: the wave overtopping flow velocity (OFV) and the overtopping layer thickness (OLT). The main issue, however, is that most studies have predominantly focused on impermeable structures rather than composite breakwaters. This study conducted 55 physical experiments to investigate the OFV and OLT on a composite breakwater. The non-intrusive bubble image velocimetry (BIV) technique was employed to measure the OFV and OLT, as well as the plunging distance on the rear side of the structure. Empirical equations with two sets of dimensionless variables, the wave steepness and relative crest freeboard, were proposed as predictors. The results show that these two dimensionless variables perform well for both OFV and OLT estimation. The comparison between the proposed empirical equation and the available empirical equation in the literature is also presented. Finally, the proposed empirical equations were used to estimate the maximum instantaneous wave overtopping discharge and plunging distance. The findings of this research offer insights into the physical mechanisms of wave overtopping, providing an initial exploration into the design of composite breakwaters.

The development of wave energy devices is growing in recent years. One type of device is the overtopping wave energy converter (OWEC), for which the knowledge of the wave overtopping rates is a basic and crucial aspect in their design. In particular, the most interesting range to study is for OWECs with steep slopes to vertical walls, and with very small freeboards and zero freeboards where the overtopping rate is maximized, and which can be generalized as steep low-crested structures. Recently, wave overtopping prediction formulae have been published for this type of structures, although their accuracy has not been fully assessed, as the overtopping data available in this range is scarce. We performed a critical analysis of the overtopping prediction formulae for steep low-crested structures and the validation of the accuracy of these formulae, based on new overtopping data for steep low-crested structures obtained at Ghent University. This paper summarizes the existing knowledge about average wave overtopping, describes the physical model tests performed, analyses the results and compares them to existing prediction formulae. The new dataset extends the wave overtopping data towards vertical walls and zero freeboard structures. In general, the new dataset validated the more recent overtopping formulae focused on steep slopes with small freeboards, although the formulae are underpredicting the average overtopping rates for very small and zero relative crest freeboards.

The present work employs the so-called Evolutionary Polynomial Regression (EPR) algorithm to build up a formula for the assessment of mean wave overtopping discharge for smooth sea dikes and vertical walls. EPR is a data-mining tool that combines and integrates numerical regression and genetic programming. This technique is here employed to dig into the relationship between the mean discharge and main hydraulic and structural parameters that characterize the problem under study. The parameters are chosen based on the existing and most used semi-empirical formulas for wave overtopping assessment. Besides the structural freeboard or local wave height, the unified models highlight the importance of local water depth and wave period in combination with foreshore slope and dike slope on the overtopping phenomena, which are combined in a unique parameter that is defined either as equivalent or imaginary slope. The obtained models aim to represent a trade-off between accuracy and parsimony. The final formula is simple but can be employed for a preliminary assessment of overtopping rates, covering the full range of dike slopes, from mild to vertical walls, and of water depths from the shoreline to deep water, including structures with emergent toes.

Adibhusana, M.N. and Ryu, Y., 2023. Image-based measurement method of overtopping flow velocity and layer thickness in irregular wave conditions. In: Lee, J.L.; Lee, H.; Min, B.I.; Chang, J.-I.; Cho, G.T.; Yoon, J.-S., and Lee, J. (eds.), Multidisciplinary Approaches to Coastal and Marine Management. Journal of Coastal Research, Special Issue No. 116, pp. 41-45. Charlotte (North Carolina), ISSN 0749-0208. Maximum overtopping flow velocity and layer thickness are the primary wave overtopping parameters when the safety of pedestrians, vehicles, or the stability of the lee side of the coastal defense structure is considered. These parameters require a study with respect to either individual waves or statistical estimations during the design process. Especially for irregular waves, many wave components make measurements difficult in addition to the nature of high turbulence and aeration of individual overtopping flows. This study applied the use of digital images to the measurements of wave overtopping flows from a set of irregular waves. Because a set of irregular waves require a long experimentation time and an image velocimetry like the Particle Image Velocimetry (PIV) needs image frame controls with very short time difference, the application of high-speed camera has not been well successful. In this study, a mosaic set of high-speed cameras to cover the overtopping flow field were installed and synchronized by being connected to an external trigger to control the measurement system and to secure the number of parameters per second enough for analysis. The experiments were carried out in a two-dimensional wave flume. A composite breakwater was used as the coastal structure model and irregular waves and following overtopping waves were generated. The captured images were processed to obtain the overtopping flow velocity and layer thickness. Unlike the point measurement method where the measurement data represent only a single location, using the image-based measurements gives the velocity and layer thickness in spatial and temporal variation in all individual wave overtopping. The velocity maps and layer thickness of the irregular waves by the image measurements were provided with more information rather than point measurements.

Kim, Y.T.; Shin, S.W.; Choi, J.W., and Lee, J.I., 2016. Effects of oblique waves on overtopping for vertical walls. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 1357 - 1361. Coconut Creek (Florida), ISSN 0749-0208. In determination of the crest height of a vertical structure against attacking of obliquely incident waves, most of existing studies have suggested to use the overtopping reduction factor due to incident angles. However, they have not considered the amplification of wave heights and the spatial distribution of wave overtopping. In this study, a spatial distribution of wave overtopping along a vertical structure is experimentally investigated and also the wave overtopping reduction factors (γ) for incident wave angle is suggested. When the incident angle becomes larger, the wave overtopping reduction factor decreases almost linearly. EurOtop (2007) suggested the constant γ for β>45°, however the decreasing γ was calculated from this study.

Leone, E.; Francone, A.; Paglialunga, A.; Ciardulli, F.; Aloisi, A., and Tomasicchio, G.R., 2024. Overtopping assessment of a rubble mound breakwater with innovative armor units: a physical and numerical study. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 804-808. Charlotte (North Carolina), ISSN 0749-0208. Rubble-mound breakwaters are essential for coastal defense, protecting ports and mitigating erosion. During storms, water overflow can cause circulating currents in protected zones. Integrating innovative armor units that efficiently dissipate energy is key in reducing wave overtopping. An experimental investigation has been conducted on a scaled model of a rubble-mound breakwater with innovative armor units at the EUMER (EUropean Maritime Environmental Research) laboratory, University of Salento, Italy. The model replicated a defense structure in the Arabian Gulf, protecting an artificial island. A critical section prone to overtopping has been built at a 1:15 model scale. The investigation analyzed the performance of the armor units in terms of wave overtopping under operational and extreme conditions, considering the Gulf's wave characteristics. To enhance reliability, the physical model investigation has been complemented by a numerical study. Numerical simulations have been performed using the OpenFoam C++ libraries and the IHFOAM multiphase flow solver. The VARANS equations solved the two-phase flow within the breakwater's porous media. To close the system of equations describing the turbulent flow, the k-ω SST turbulence model has been selected, due to the good trade-off between cost and accuracy. The VOF method has been applied to track the free surface elevation over time. The numerical simulations showed strong agreement with experimental observations, demonstrating IHFOAM as a reliable tool to predict wave overtopping phenomena.

Lim, H. S., Hong, S., Park, J. H., Choi, Y. and Choi, H., 2024. Development of coastal disaster simulation system using marine digital twin technology. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 981-985. Charlotte (North Carolina), ISSN 0749-0208. In recent years, rising sea levels due to global warming and climate change, as well as an increase in high waves and swells caused by typhoons or strong winds, have raised concerns about coastal disasters such as wave overtopping and coastal erosion along the coasts of the Korean Peninsula. Recently, marine ICT convergence technology has been developed that replicates the real world (physical world) identically in virtual space and predicts the simulation results using a digital twin integrated with an artificial intelligence system. The Coastal Disaster Simulation System (CDSS), based on a geospatial digital twin cloud web 3D GIS system, has been developed to predict coastal disasters such as typhoons, storm surges, high waves, wave overtopping, flooding and beach erosion using real-time monitoring data and numerically predicted results. The CDSS performs scientific analyses such as typhoon track analysis, damage analysis to coastal facilities within the storm induced hazard radius, storm surge damage area analysis, overtopping discharge analysis, inundation area analysis and coastal erosion analysis. To determine the area and depth of flooding or inundation caused by typhoon storm surges or overtopping discharges, this system uses the Eurotop Overtopping Manual (2018) to calculate the wave overtopping volume and performs an analysis based on the relative elevation of the coastal terrain at that time. This system is expected to contribute to the prevention of coastal disaster and support the establishment of a coastal disaster prevention decision-making system.

Aquino, C.J.P. and De Leon, M.P., 2024. Preliminary investigation on the effects of sea-level rise on the wave overtopping performance and armour stability of an existing breakwater. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 210-214. Charlotte (North Carolina), ISSN 0749-0208. The Sixth Assessment Report (AR6) published by the Intergovernmental Panel on Climate Change (IPCC) presented a new set of sea-level rise projections. In the Philippines, the sea level trend ranges from 1.28 to 13.13 mm/year considering long-term observations of 19 years or beyond. Because of these alarming projections, the effects of sea level rise may exceed the initial design expectations of our coastal infrastructures. This study aims to determine the impact of sea level rise on the wave overtopping performance and armour stability of an existing breakwater located at the Manila South Harbor, Manila Bay, Philippines. The main parts of the methodology include extensive data collection from global and local credible sources, hydrodynamic (numerical) modelling using MIKE 21 Coupled Hydrodynamic and Spectral Wave model, application of sea level rise projections to the resulting water levels, and evaluation of the existing breakwater through empirical calculations. The results of the wave modelling revealed that a maximum storm surge level of 1.13m (referenced from MSL) is expected. This would result to a maximum design water level of 2.85m MLLW for SSP5-8.5(LC) sea level rise scenario. A maximum overtopping of roughly 1684.36 l/s/m was calculated. This excessive overtopping was primary due to the existing low crest level of +3.0m MLLW. For armour stability, only three breakwater sections (Sta 0+400, Sta0+600, and Sta0+630) were not able to satisfy the criteria. An increase of 50.70% rock armour weight is required to satisfy the design criteria under the most critical sea level scenario of SSP5-8.5 (LC).