Deep Water Wave Height Research Articles

Foredune erosion, overtopping and destruction in 2022 at Bengello Beach, southeastern Australia

Abstract The beach–foredune system at Bengello Beach has been monitored monthly to bimonthly at four profiles (P1–P4) since 1972 and documented the building of a foredune. This paper addresses the remarkable changes which occurred in 2022 as storm waves overtopped and trimmed this foredune at all profiles, then later removed this entire feature at two of the profiles (P3, P4) but not the others (P1, P2). Wave parameters for these storm events, measured by deepwater and nearshore wave buoys, enable a comparison of storm characteristics and resulting beach–foredune impact. During the storm event which destroyed the foredune, nearshore wave height exceeded deepwater wave height, in contrast with other storms that year. The beach–foredune lost 78 m3/m in 2022 and the notable 1974 storms that impacted this coastline resulted in 95 m3/m volume loss. During 2023, beach recovery has occurred, but not rebuilt the foredune. It had persisted for ~40 years enduring many other severe storm events, and the coastal protection afforded by the dune system has been compromised. This highlights the need to consider dune morphology in assessments of erosion hazard and inundation risk along similar coastlines.

NATIONAL ASSESSMENT OF HURRICANE-INDUCED COASTAL EROSION HAZARDS IN PUERTO RICO

Storms are one of the main causes of coastal erosion, causing substantial property and infrastructure losses in coastal communities. Coastal erosion is particularly damaging in underrepresented communities that are unable to meet building and zoning regulations due to limited resources [Lam, 2014]. The United States Geological Survey (USGS) has developed a probabilistic assessment of hurricane-induced coastal erosion for sandy coastlines along the eastern United States and the Gulf of Mexico. However, the current USGS product incorporates an empirical equation with inputs of beach slope and deep-water wave height and period [Stockdon, 2006] to predict the wave runup. Though this is appropriate for open coast sandy beaches, it is not valid for the rocky and reef lined coasts of Puerto Rico due to their complex bathymetries, steep slopes, and large bottom roughness. To expand this tool to Puerto Rico, the USGS has created 1-dimensional XBeach [Roelvink, 2009] models around the island.

Prediction of breaking wave height by using artificial neural network-based approach

This study applies artificial neural network-based methodology to predict the breaker height (Hb). 1120 data samples from 53 experiments covering a wide range of seabed slopes are used to examine 36 existing models and artificial neural network (ANN) models. The results indicate that the developed models are more reliable than existing models not only in overall cases but also in any slope range (horizontal, gentle, intermediate, and steep slope). Especially for ANN model 1, root-mean-square-relative error reduces 3.2%–5.9% in comparison with the three best existing formulas in general. Additionally, there is more than 90% of calculated data that differ from measured data by less than 20% as using ANN model 1, this result is better than all existing formulas. In case of classification according to surf similarity wave, ANN model 1 is also better at estimating breaking wave height for both spilling and plunging types. The sensitivity analyses for seabed slope, water depth, and deep-water wavelength with various models are also carried out. The effect of slope, breaker depth, deep-water wavelength, and deep-water wave height on Hb is quite similar to existing models. Based on the outstanding results, ANN model 1 is acceptable and highly recommended to apply in estimation of breaker height.

Storm Wave Characteristics during Typhoons Maysak and Haishen on the East and South Coasts of Korea

Seo, S.-C.; Kim, H.-J.; Hwang, T., and Lee, W.-D., 2023. Storm wave characteristics during Typhoons Maysak and Haishen on the east and south coasts of Korea. Journal of Coastal Research, 39(1), 129–142. Charlotte (North Carolina), ISSN 0749-0208. Typhoons Maysak and Haishen, the ninth and tenth typhoons of 2020, ravaged the Korean Peninsula within an interval of only 4 to 5 days. In the vicinity of the peninsula, these two typhoons exhibited unusual northward movement paths as they made landfall on the south coast of Korea and exited off the east coast. The storm waves caused by these typhoons damaged a number of structures along the east and south coasts, particularly by overtopping and flooding. In this study, storm waves were estimated by applying the wind fields caused by Typhoons Maysak and Haishen in the third-generation wave model Simulation WAves Nearshore (SWAN), and results were verified through a comparison with wave observation data. The storm wave characteristics were analyzed mainly based on the east and south coasts, which were damaged by high waves that accompanied the typhoons. In addition, the deep-water design wave specifications around the Korean Peninsula revised in 2019 were compared with the storm waves that occurred during Typhoons Maysak and Haishen as calculated by the SWAN model. Consequently, during the onslaughts of Typhoons Maysak and Haishen, storm waves corresponding to more than 90% of the deep-water design wave heights for the 50 year return period were estimated at grid points on the East Sea and Ulleungdo Island of Korea.

A deep water and nearshore wave height calibration of the ECOWAVES hindcasting database

Significant wave height (SWH) in shallow waters is assessed by generating two wave hindcasts; the first uses ERA-Interim wind fields and the second one from ERA5 to quantify the improvement of the ERA5 surface winds on the SWH representativeness, both in deep and shallow waters along the Chilean coastline. Additionally, wind field predictions from the Global Forecast System (GFS) were used to assess the representativeness of shallow waters. Oceanographic buoys were used to validate SWH in deep waters, while Acoustic Doppler Current Profiler (ADCPs) was equipped to measure waves in shallow waters. Energy spectrums coupling Wavewatch III and Simulating Waves Nearshore (SWAN) models were transferred to evaluate the performance of shallow water simulations. In general, the SWH from both wave hindcasts showed good performance. Nonetheless, those forced by ERA5 presented a better qualitative comparison of sea state temporal variability, which increased the correlation coefficients (>0.9), coefficients of determination (>0.8), and minor errors (RMSE, MAE, and BIAS) compared to oceanographic buoys and ADCPs. Additionally, in simulations forced by GFS, the temporal variability of the waves in shallow waters was successfully reproduced. Nevertheless, an increase in the RMSE, MAE, and BIAS error was statistically verified compared to ERA-Interim and ERA 5.

Estimation of Wave-Breaking Index by Learning Nonlinear Relation Using Multilayer Neural Network

Estimating wave-breaking indexes such as wave height and water depth is essential to understanding the location and scale of the breaking wave. Therefore, numerous wave-flume laboratory experiments have been conducted to develop empirical wave-breaking formulas. However, the nonlinearity between the parameters has not been fully incorporated into the empirical equations. Thus, this study proposes a multilayer neural network utilizing the nonlinear activation function and backpropagation to extract nonlinear relationships. Existing laboratory experiment data for the monochromatic regular wave are used to train the proposed network. Specifically, the bottom slope, deep-water wave height and wave period are plugged in as the input values that simultaneously estimate the breaking-wave height and wave-breaking location. Typical empirical equations employ deep-water wave height and length as input variables to predict the breaking-wave height and water depth. A newly proposed model directly utilizes breaking-wave height and water depth without nondimensionalization. Thus, the applicability can be significantly improved. The estimated wave-breaking index is statistically verified using the bias, root-mean-square errors, and Pearson correlation coefficient. The performance of the proposed model is better than existing breaking-wave-index formulas as well as having robust applicability to laboratory experiment conditions, such as wave condition, bottom slope, and experimental scale.

Sediment textural characteristics and spatial variability of embayed sandy beaches in the west Guangdong

The grain size analysis has been widely used to characterize or distinguish sedimentary environments, identify transport patterns and infer sediment transport directions. However, what valuable information can sediment grain size analysis provide within the modern morphodynamic framework? This paper studied the structural characteristics and spatial variability of intertidal sediments for twelve embayed sandy beaches in the west Guangdong and attempted to answer this question. The results indicated that these beaches were mainly composed of fine- or medium-grained, moderately-well sorted, nearly symmetrical and mesokurtic intertidal sediments. It was found that the cumulative probability curve was not necessarily an effective method to distinguish longshore dynamic environments, and the bivariate scatter plots between grain size parameters cannot differentiate between the upper and lower intertidal sedimentary environments. The mean sizes of the intertidal sediments were significantly correlated with the intertidal gradients, but not significantly correlated with the deep-water wave heights. The mean sizes from the upper intertidal sediments were found to be an important indicator for most of the embayed sandy beaches, reflecting the longshore variation of modern hydrodynamics. In addition, it was highlighted for the role of sediment source and various past processes, which largely determined the basic characteristics of the studied beach sediments.

Study of groin structures effectiveness for against abrasion in Padang Beach

This study was conducted to evaluating the performance of existing coastal protection structure to restrain the rate of erosion as a result of the influence of hydrodynamics process. Condition that reviewed was in form of distance shoreline as simulation results to initial reference line before. STWAVE module used to determine wave height at near shore as transformation of deep water wave height that determined before from SMB method. One Line Model was conducted to get shoreline change in each time step calculation. Model consists of two conditions, with the absence of coastal structures and with structure respectively. The simulation result show that potential erosion occurs at Batang Arau river mouth with no protection structure. Large erosion predicted around 59.04 meters from the shoreline position early. With coastal protection, model result obtained sedimentation of 7.33 meters coastline from its initial position. This occurs at a distance of 475 meters from the boundary domain. Modeling results also showed erosion is 18.39 meters at a distance of 250 m from the boundary domain. This is likely due to the limited modelling conditions that without reviewing of littoral transport direction that occurred in perpendicular to the coast. Result study show that the presence of a groins in Padang coasts looks already quite effective to maintain the shoreline of the littoral transport direction, however the installation of groins seemingly did not give significant meaning in the addition of the coastline.

Simulating wave runup on an intermediate–reflective beach using a wave-resolving and a wave-averaged version of XBeach

The prediction of wave runup, as well as its components, time-averaged setup and the time-varying swash, is a key element of coastal storm hazard assessments, as wave runup controls the transitions between morphodynamic response types such as dune erosion and overwash, and the potential for flooding by wave overtopping. While theoretically able to simulate the dominant low-frequency swash, previous studies using the infragravity-wave–resolving model XBeach (XBSB) have shown an underestimation of the observed swash variance and wave runup, which was in part related to the absence of incident-band swash motions in the model. Here, we use an incident-band wave-resolving, non-hydrostatic version of the XBeach model (XBNH) to simulate wave runup observed during the SandyDuck '97 experiment on an intermediate–reflective sandy beach. The results show that the XBNH model describes wave runup and the individual setup and swash components well. We subsequently examine differences in wave runup prediction between the XBSB and XBNH models and find that the XBNH model is a better predictor of wave runup than XBSB for this beach, which is due to better predictions of both the incident-band and infragravity-band swash. For a range of beach states from reflective to dissipative it is shown that incident-band swash is underestimated by XBSB relative to XBNH, in particular for reflective conditions. Infragravity-band swash is shown to be lower in XBSB than XBNH for most conditions, including dissipative conditions for which the mean difference is 16% of the deep water wave height. The difference in infragravity-band swash in XBNH relative to XBSB is shown to mainly be the result of processes occurring outside the swash zone, but approximately 15% of the difference is caused by explicitly resolving incident-band wave motions within the swash zone, such as swash-swash interactions, which inherently cannot be simulated by wave-averaged models.

Predicting site-specific storm wave run-up

Storm wave run-up causes beach erosion, wave overtopping, and street flooding. Extreme runup estimates may be improved, relative to predictions from general empirical formulae with default parameter values, by using historical storm waves and eroded profiles in numerical runup simulations. A climatology of storm wave run-up at Imperial Beach, California is developed using the numerical model SWASH, and over a decade of hindcast spectral waves and observed depth profiles. For use in a local flood warning system, the relationship between incident wave energy spectra E(f) and SWASH-modeled shoreline water levels is approximated with the numerically simple integrated power law approximation (IPA). Broad and multi-peaked E(f) are accommodated by characterizing wave forcing with frequency-weighted integrals of E(f). This integral approach improves runup estimates compared to the more commonly used bulk parameterization using deep water wave height H_0 and deep water wavelength L_0 Hunt (Trans Am Soc Civ Eng 126(4):542–570, 1961) and Stockdon et al. (Coast Eng 53(7):573–588, 2006. https://doi.org/10.1016/j.coastaleng.2005.12.005). Scaling of energy and frequency contributions in IPA, determined by searching parameter space for the best fit to SWASH, show an H_0L_0 scaling is near optimal. IPA performance is tested with LiDAR observations of storm run-up, which reached 2.5 m above the offshore water level, overtopped backshore riprap, and eroded the foreshore beach slope. Driven with estimates from a regional wave model and observed beta _f, the IPA reproduced observed run-up with <30% error. However, errors in model physics, depth profile, and incoming wave predictions partially cancelled. IPA (or alternative empirical forms) can be calibrated (using SWASH or similar) for sites where historical waves and eroded bathymetry are available.

Overtopping Metrics and Coastal Safety: A Case of Study from the Catalan Coast

Design criteria for coastal defenses exposed to wave overtopping are usually assessed by mean overtopping discharges and maximum individual overtopping volumes. However, it is often difficult to give clear and precise limits of tolerable overtopping for all kinds of layouts. A few studies analyzed the relationship between wave overtopping flows and hazard levels for people on sea dikes, confirming that one single value of admissible mean discharge or individual overtopping volume is not a sufficient indicator of the hazard, but detailed characterization of flow velocities and depths is required. This work presents the results of an experimental campaign aiming at analyzing the validity of the safety limits and design criteria for overtopping discharge applied to an urbanized stretch of the Catalan coast, exposed to significant overtopping events every stormy season. The work compares different safety criteria for pedestrians. The results prove that the safety of pedestrians on a sea dike can be still guaranteed, even for overtopping volumes larger than 1,000 L/m. Sea storms characterized by deep-water wave height between 3.6 and 4.5 m lead to overtopping flow depth values larger than 1 m and flow velocities up to 20 m/s. However, pedestrian hazard is proved to be linked to the combination of overtopping flow velocity and flow depth rather than to single maximum values of one of these parameters. The use of stability curves to assess people’s stability under overtopping waves is therefore advised.

New procedure for determining equivalent deep-water wave height and design wave heights under irregular wave conditions

Many coastal engineering designs utilize empirical formulas containing the Equivalent Deep-water Wave Height (EDWH), which is normally given a priori. However, no studies have explicitly discussed a method for determining the EDWH and the resulting design wave heights (DEWH) under irregular wave conditions. Unfortunately, it has been the case in many design practices that the EDWH is incorrectly estimated by dividing the Shallow-water Wave Height (SWH) at the structural position with its corresponding shoaling coefficient of regular wave. The present study reexamines the relationship between the Shallow-water Wave Height (SWH) at the structural position and its corresponding EDWH. Then, a new procedure is proposed to facilitate the correct estimation of EDWH. In this procedure, the EDWH and DEWH are determined differently according to the wave propagation model used to estimate the SWH. For this, Goda's original method for nonlinear irregular wave deformation is extended to produce values for linear shoaling. Finally, exemplary calculations are performed to assess the possible errors caused by a misuse of the wave height calculation procedure. The relative errors with respect to the correct values could exceed 20%, potentially leading to a significant under-design of coastal or harbor structures in some cases.

Forecasting Sudden High Waves on the Coasts of East/Japan Sea

Oh, J.; Kim, I.-C.; Suh, K.-D., and Kim, S., 2019. Forecasting sudden high waves on the coasts of East/Japan Sea. In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 96-100. Coconut Creek (Florida), ISSN 0749-0208.During the recent decade, marine accidents and property damage due to high waves have frequently occurred on the coasts of East/Japan Sea, especially during the winter season. One of the major characteristics of the waves is its suddenness associated with rapid development of high waves from a calm state of sea. In 2016, Kim, Oh, and Suh named these waves ‘sudden high waves’ and proposed a criterion for sudden high waves by comparing the wave measurement data and the record of marine accidents and property damage on the east coast of the Korean Peninsula. Their intensity parameter of sudden high waves was proposed in terms of local wave height and wavelength. The criterion for sudden high waves is proposed as To enhance its generality, in this study, a similar analysis is made in terms of deepwater wave height and wavelength. It is also shown that the parameter can be forecasted if accurate wave forecast data is available. To show this, the spatio-temporal variation of the parameter is calculated using the wave hindcast data, and the wave measurement data and the record of damage are examined during the period when the parameter exceeds the criterion on the coasts.

Storm Waves at the Shoreline: When and Where Are Infragravity Waves Important?

Infragravity waves (frequency, f = 0.005–0.05 Hz) are known to dominate hydrodynamic and sediment transport processes close to the shoreline on low-sloping sandy beaches, especially when incident waves are large. However, in storm wave conditions, how their importance varies on different beach types, and with different mixes of swell and wind-waves is largely unknown. Here, a new dataset, comprising shoreline video observations from five contrasting sites (one low-sloping sandy beach, two steep gravel beaches, and two compound/mixed sand and gravel beaches), under storm wave conditions (deep water wave height, H0 up to 6.6 m, and peak period, Tp up to 18.2 s), was used to assess: how the importance and dominance of infragravity waves varies at the shoreline? In this previously unstudied combination of wave and morphological conditions, significant infragravity swash heights (Sig) at the shoreline in excess of 0.5 m were consistently observed on all five contrasting beaches. The largest infragravity swash heights were observed on a steep gravel beach, followed by the low-sloping sandy beach, and lowest on the compound/mixed sites. Due to contrasting short wave breaking and dissipation processes, infragravity frequencies were observed to be most dominant over gravity frequencies on the low-sloping sandy beach, occasionally dominant on the gravel beaches, and rarely dominant on the compound/mixed beaches. Existing empirical predictive relationships were shown to parameterize Sig skillfully on the sand and gravel beaches separately. Deep water wave power was found to accurately predict Sig on both the sand and gravel beaches, demonstrating that, under storm wave conditions, the wave heights and periods are the main drivers of infragravity oscillations at the shoreline, with the beach morphology playing a secondary role. The exception to this was the compound/mixed beach sites where shoreline infragravity energy remained low.

Laboratory investigation of the breaking wave characteristics over a barrier reef under the effect of current

ABSTRACT Recent field studies have increasingly recognized the importance of tides in dominating the coral reef hydrodynamics. Aside from the tidal level, it is also important to evaluate the effect of tidal current on wave breaking over coral reefs. In this study, a series of laboratory experiments were performed in a wave-current flume in the presence of both flooding and ebbing tides. Experimental results are reported for a variety of combined wave-current conditions based on an idealized barrier reef model. Results analyses show that the relative reef-flat submergence (the ratio of reef-flat submergence to deep-water wave height) is a key parameter to characterize such breaking-wave characteristics as the breaker type, the breaking location, the surfzone width, and the breaker depth index. The influences of the current flowrate on the breaking location, the surfzone width, and the breaker height index appear to be significant within our tested ranges. Empirical formulas to predict these characteristics in the existing literature are also improved to account for the current effect.

The Tsunami Threat to Sydney Harbour, Australia: Modelling potential and historic events

Tsunami modelling of potential and historic events in Australia’s Sydney Harbour quantifies the potentially damaging impacts of an earthquake generated tsunami. As a drowned river valley estuary exposed to distant source zones, these impacts are predominantly high current speeds (>2 m/s), wave amplification and rapid changes in water level. Significant land inundation only occurs for scenarios modelled with the largest waves (9.0 MW source). The degree of exposure to the open ocean and the geomorphology of locations within the Harbour determine the relative level of these impacts. Narrow, shallow channels, even those sheltered from the open ocean, create a bottleneck effect and experience the highest relative current speeds as well as elevated water levels. The largest maximum water levels (>8 m) occur in exposed, funnel-shaped bays and wave amplification is greatest at locations exposed to the open ocean: >7 times deep water wave heights for 9.0 MW source waves. Upstream attenuation rates of runup and maximum water level show a linear correlation with wave height parameters at the 100 m depth contour and may provide some predictive capabilities for potential tsunami impacts at analogous locations. In the event of a tsunami in Sydney Harbour, impacts may threaten marine traffic and infrastructure.

Extreme coastal erosion enhanced by anomalous extratropical storm wave direction

Extratropical cyclones (ETCs) are the primary driver of large-scale episodic beach erosion along coastlines in temperate regions. However, key drivers of the magnitude and regional variability in rapid morphological changes caused by ETCs at the coast remain poorly understood. Here we analyze an unprecedented dataset of high-resolution regional-scale morphological response to an ETC that impacted southeast Australia, and evaluate the new observations within the context of an existing long-term coastal monitoring program. This ETC was characterized by moderate intensity (for this regional setting) deepwater wave heights, but an anomalous wave direction approximately 45 degrees more counter-clockwise than average. The magnitude of measured beach volume change was the largest in four decades at the long-term monitoring site and, at the regional scale, commensurate with that observed due to extreme North Atlantic hurricanes. Spatial variability in morphological response across the study region was predominantly controlled by alongshore gradients in storm wave energy flux and local coastline alignment relative to storm wave direction. We attribute the severity of coastal erosion observed due to this ETC primarily to its anomalous wave direction, and call for greater research on the impacts of changing storm wave directionality in addition to projected future changes in wave heights.

A new parameterisation for runup on gravel beaches

Video derived runup statistics from ten separate deployments at six field sites have been used to develop a new parameterisation for the prediction of runup of runup on gravel beaches. These data were collected over a 2-year period under energetic storm conditions with significant wave heights of Hs=1–8m from gravel beaches and barriers composed of fine gravel (D50=2mm) to large pebbles (D50=160mm). An additional data set was generated using the numerical model XBeach-G, developed specifically for gravel beaches, and this synthetic dataset was used to further explore the role of hydrodynamic and morphological parameters on wave runup. A runup equation was developed using the synthetic data set and validated using the field data. The four parameters in this equation are, in decreasing order of importance, significant deep water wave height (Hs), spectral mean period (Tm−1,0), beach slope (tanβ) and grain size (D50). The new gravel beach runup equation was found to fit the synthetic data set and the field data extremely well (r2=0.97 and 0.89, respectively) and the new equation performs significantly better than existing runup equations, even those specifically developed for gravel beaches.

Artificial neural network based breakwater damage estimation considering tidal level variation

A new approach to damage estimation of breakwater armor blocks was developed by incorporating a wave height prediction artificial neural network (ANN) into a Monte Carlo simulation (MCS). The ANN was used to predict the wave height in front of a breakwater, with both the deep water wave heights and tidal level being input to the ANN. The waves predicted by the ANN were comparable to those from a wave transform analysis. Using an ANN in wave prediction makes it possible to very simply and quickly obtain numerous waves near the breakwater. Eventually, the analysis time for the expected damage can be reduced. In addition, the effect of the tidal level on the expected damage was revealed by numerical examples. In these numerical examples, it was found that the tidal variation should be taken into account when estimating the expected breakwater damage.

Approximation of bivariate probability density of individual wave steepness and height with copulas

The bivariate probability density of individual wave steepness and height is fitted with theoretical bivariate densities in the form of copulas. Copula functions approximate only the relation of the dependency between both random variables and marginal densities can be modeled separately. In this study the primary problem is finding a copula function which could faithfully represent the dependency relation between deep water wave height and steepness, so modeling marginal probability densities is a secondary question. A short description of the formulation of copula functions is given, and five different copula functions used in this study are described. These functions have been fit to wave data measured in an offshore basin and comparison with the empirical distribution allowed some conclusions about the adequacy of the various models.