Search

In‐situ observations of hydrodynamics and suspended sediment concentrations (SSCs) were conducted on an abandoned lobe in the northern part of the modern Yellow River Delta, China. The SSC record at the site is found to be the superposition of a general trend (fast increase and slow decrease cycle) caused by storm waves (SubSSC1) and relatively smaller fluctuations caused by tidal currents (SubSSC2). Physically, this indicates that storm waves eroded the bottom sediments while tidal currents then re‐suspended and advected the suspended sediments in the study area. To further obtain the suspended sediment transport parameters, first, SubSSC1 is modeled with significant wave height which incorporates a "memory curve" to consider the remaining impacts of historical waves. It is detected that waves in the past 75 hr still influence the present SSC which is reasonable because 75 hr is roughly the typical duration of a normal storm. Second, SubSSC2 is modeled with tidal excursion and trigonometric functions with measured periodicities. Finally, some sediment transport parameters, for example, the background SSC, the horizontal SSC gradient, the tidal constituents that advect it, and their relative time lags are optimized from the best fits of the measured and modeled SSC time series. The proposed framework for model construction and parameter optimization can be extended to other sea areas for inferring sediment transport parameters from field SSC time series at a specific station. Plain Language Summary: The evolution of our coastal zone fundamentally depends on the transport volume and direction of sediment, and understanding them is very beneficial for our coastal engineering construction and long‐term planning. Conducting in situ observations on‐site is one of the most reliable methods, but its observation cost is expensive. Therefore, we hope to extract as much information as possible from as few observation points as possible. This article successfully extracted the above information from the observation data of a station. First, we analyzed the data to preliminarily clarify that the suspended sediment in the area mainly comes from local erosion resuspension and advection transport from other regions. Furthermore, we conducted data modeling (i.e., constructed mathematical expressions of suspended sediment components from different sources, but with undetermined coefficients). Finally, we adjusted the model parameters to approximate the measured results, determined the undetermined coefficients, and explained the practical significance of the undetermined coefficients in physics. The analysis method we proposed can be extended to other sea areas. Key Points: Storm wave‐induced suspended sediment concentration (SSC) variation is modeled with a "memory curve" of wave heightTidally‐induced SSC variation is modeled with tidal excursion and trigonometric functionsSediment transport parameters are estimated from the optimal matching of measured and modeled SSC time series [ABSTRACT FROM AUTHOR]

Shorelines face growing threats due to climate change and diminishing sand supply. Coastal headlands, common rocky features along coastlines, are crucial in shaping hydrodynamics and sediment transport. Yet, the influence of future climate conditions, including sea‐level rise (SLR) and intensified storm energy on complex shorelines with headlands has remained relatively unexplored. In this study, we model changes in hydrodynamics and headland bypassing under different SLR and higher storm wave scenarios. Our findings reveal the formation of circulation cells on both sides of a headland, where wave energy converges around the headland zone. Future climate conditions result in larger storm waves on the beach. However, SLR enhances nearshore currents through a landward shifting of the circulation cells, while higher storm waves intensify offshore flow currents due to the seaward movement of the cells. This effect, in turn, increases the potential for headland sediment bypassing. Plain Language Summary: Coastal headlands, prominent rocky features along open coastlines, play a crucial role in protecting nearby beaches from strong waves and erosion. They also affect how sand is exchanged between different beaches. We use a model to explore how future climate conditions including sea‐level rise (SLR) and larger storm waves influence coastal waves, littoral currents, and the transport of sand around headlands. Our findings reveal that headlands converge wave energy forming circulation flow cells. SLR results in stronger nearshore currents, driven by the landward movement of the rotating flow cells. In contrast, larger storm waves can move the rotating flow cells seaward, thereby increasing offshore current strength and the potential for sand transport around the headland. Understanding how coastal waves, flow and sediment transport change under future climate conditions will help determine coastal resilience. Key Points: The formation of circulation cells and wave energy convergence around headlands during storms reduce bottom shear stress at the beachSea‐level rise increases wave heights, currents, and bed shear stress in the nearshore because of landward shifting of the circulation cellsHigher storm waves expand the surf zone, shift circulation cells seaward, and enhance potential headland sediment bypassing [ABSTRACT FROM AUTHOR]

A high-level coastal boulder field at Whalers Way, southern Eyre Peninsula, South Australia, occurs at elevations of 20–30 m above present sea-level on a gently seaward-sloping, karst-weathered calcrete-capped structural bench, formed on the Upper Pleistocene Bridgewater Formation and underlying Carnot Gneisses (Archean–Paleoproterozoic Sleaford Complex). More than 1000 ex situ boulders, cobbles and pebbles of gneiss and mafic igneous rocks, as well as fragments of calcrete, occur within the boulder field and cover an area >6000 m2. All the crystalline rock clasts are derived locally from bedrock outcrops along the adjacent coastline, where metasedimentary granulite-facies of the Carnot Gneisses crop out along shore platforms and their backing cliffs, close to present sea-level. The boulder field is younger than Marine Isotope Sub-Stage 5a (MIS 5a; ca 80 ka) based on amino acid racemisation 'whole-rock' analyses of calcarenite of the Bridgewater Formation, which forms the calcrete bench on which the boulder field rests. The boulder field wraps around the western extremity of cliff-top dunes dated at 18–17 ka by optically stimulated luminescence, implying that the boulder deposit post-dates the formation of the cliff-top dunes. Given that the clasts in the boulder field show minimal weathering rinds, sea-level during the Last Glacial Maximum was some 125 m lower than present and that between 80 and 7 ka ago, sea-level never attained present levels within the region, emplacement of the boulder field by a high-energy wave event in the Holocene highstand, following the 7000 years BP culmination of post-Glacial sea-level rise, is suggested. Storm waves, rather than a tsunami, most likely explain the emplacement of the boulder field. Amino acid racemisation and optically stimulated luminescence dating suggest a Holocene age younger than 7000 years for a high-level (20–30 m above present sea-level) coastal boulder field at Whalers Way, Eyre Peninsula, southern Australia. Gravity-influenced sedimentation, tectonic uplift and glacial action (relict Permian or Cretaceous glacigene sediment) fail to explain the origin of the enigmatic boulder deposit. The boulder deposit formed by storm waves, rather than a tsunami origin, following the 7000 year BP culmination of post-Glacial sea-level rise and onset of the Holocene sea-level highstand. [ABSTRACT FROM AUTHOR]

Coastal wetlands such as salt marshes and mangroves provide important protection against stormy waves. Accurate assessments of wetlands' capacity in wave attenuation are required to safely utilize their protection services. Recent studies have shown that tidal currents have a significant impact on wetlands' wave attenuation capacity, but such impact has been rarely considered in numerical models, which may lead to overestimation of wave attenuation in wetlands. This study modified the SWAN (Simulating Waves Nearshore) model to account for the effect of accompanying currents on vegetation-induced wave dissipation. Furthermore, this model was extended to include automatically derived vegetation drag coefficients, spatially varying vegetation height, and Doppler Effect in combined current-wave flows. Model evaluation against an analytical model and flume data shows that the modified model can accurately simulate wave height change in combined current-wave flows. Subsequently, we applied the new model to a mangrove wetland on Hailing Island in China with a special focus on the effect of currents on wave dissipation. It is found that the currents can either increase or decrease wave attenuation depending on the ratio of current velocity to the amplitude of the horizontal wave orbital velocity, which is in good agreement with field observations. Lastly, we used Hailing Island site as an example to simulate wave attenuation by vegetation under hypothetical storm surge conditions. Model results indicate that when currents are 0.08–0.15 m/s and the incident wave height is 0.75–0.90 m, wetlands' wave attenuation capacity can be reduced by nearly 10% compared with pure wave conditions, which provides implications for critical design conditions for coastal safety. The obtained results and the developed model are valuable for the design and implementation of wetland-based coastal defense. The code of the developed model has been made open source, in the hope to assist further research and coastal management. [ABSTRACT FROM AUTHOR]

Current effects on waves (CEW) are among the most intricate physical processes in wave evolution. In this study, we used a coupled wave-tide-circulation model for the Northwest Atlantic to investigate current effects on storm waves during Hurricane Igor in 2010. Validated with extensive buoy and altimeter data, the inclusion of CEW in the model significantly improves the accuracy in simulating significant wave heights (H s) by up to 21.3% for a wave buoy. Storm waves experience significant temporal and spatial modulation by multi-scale currents. Storm-driven currents have the most pronounced impact to the right of the storm track, which typically align with wave propagation and reduce H s by up to 12.1%. The subsequent near-inertial oscillations induce temporal fluctuations of wave convergence and divergence at near-inertial frequencies, which also occurs in regions with strong tidal currents but at tidal frequencies. Furthermore, storm waves are modulated by the Gulf Stream, Labrador Current and associated mesoscale eddies. Overall, these multi-scales yield strong effects on storm waves (H s > 3.0 m), significantly modulating H s (−25.2%–+55.4%) and mean wave periods (−14.9%–+15.7%). The mean wave energy power shows more significant modulation by multi-scale currents, reflecting the combined effects of changing wave states and current-induced transport of wave energy. CEW are governed by the interactive dynamic and kinematic effects. The relative wind effect is the primary mechanism for lower storm waves by reducing energy input to waves and influences downstream wave states. Among kinematic effects, current-induced wave refraction typically plays a dominant role in redistributing wave energy. This study systematically quantified the modulation of storm waves by multi-scale currents and revealed the underlying mechanisms, providing a comprehensive understanding of extreme wave states under coupled ocean dynamics. • Temporal and spatial modulation of significant wave heights by multi-scale currents from −25.2% to 55.4% during Igor. • Reduction in storm waves mainly due to relative wind effect and wave convergence/divergence by current-induced refraction. • Reduction in intense wave energy power by up to 19.0% due to changing wave energy and Doppler-shifted group velocity. [ABSTRACT FROM AUTHOR]

Delta bathymetry, seismic data and near-surface sediment sampling on modern deltas with significant wave, tidal or marine current influence betray a double clinoform architecture with a bridging subaqueous platform. Much of the muddy portion of river-sediment discharge that reaches the coastline bypasses the mouth bar/shoreline clinoform and is deposited, eroded, re-suspended and stored in the distant subaqueous portion of deltas. The sediment stored on the prograding slope of the subaqueous delta is predominantly muddy and heterolithic sediment gravity flows, a diagnostic feature of the prograding and rapidly accumulating subaqueous delta. The subaqueous delta sometimes becomes markedly skewed offshore to run parallel to the shoreline, a routing often aided by shelf currents. Early marine researchers tackled the problem of how sediment from the river reaches so far out (commonly 100 km) on the shelf; they showed that negatively and positively buoyant river plumes, and reworked delta front/shoreface sediments are dispersed out onto the subaqueous delta, greatly assisted by the action of waves, tides and especially friction-reducing fluid mud on the seabed of the subaqueous platform. Documentation of the growth of modern subaqueous deltas has contributed to recent progress in understanding mud dispersal on shelves. Equivalent understanding of ancient deltas, however, has lagged behind. A limited dataset of ancient, double-clinoform deltas has nevertheless strengthened our understanding of how lithology and facies change across the subaqueous deltas. The ancient examples, particularly in well-resolved seismic data as on the Indus Delta and New Jersey shelf, show that the subaqueous delta clinoforms can be distinguished clearly from the mouth bar/delta front or shoreline clinoforms. However, architectural reconstruction from outcrop or well-log data is less simple. The diagnostic two-tier architecture of ancient double-clinoform successions (often eye-catching where the upper sandy shoreline deposits sit abruptly atop the underlying muddy subaqueous delta deposits) is frequently delineated by a continuous or discontinuous erosion surface that vertically separates the two tiers. This is the subaqueous platform surface of sediment bypass onto the subaqueous delta clinoform. Most bypassed sediment accumulates on the gentle foreset and flattening bottomset of the subaqueous delta to produce a 10s of m-thick, upward-coarsening muddy to heterolithic succession with tell-tale thin interbeds of rippled, graded and wavy-laminated tempestite and gravity-flow 'event' beds. The subaqueous platform is composed of variably thick mudstone and sandstone beds. The upper tier (ca. 5-15 m-thick) above the subaqueous platform is commonly sand-prone, but may also be muddy, and represents the delta-plain to shoreline clinoform. Additional features that help identify the compound delta are (1) rapid termination of the shoreline deposits, then fronted only by the subaqueous delta, (2) very low angle of downlap of the muddy subaqueous delta strata onto the shelf, and (3) accumulation of minimally bioturbated fluid-mud beds on the inner subaqueous platform, often causing the subaqueous delta succession to have a fine-grained capping, below the erosion surface. A key aspect of the present work is to show how unbioturbated fluid mud units, thin sand beds, muddy sediment gravity flows and bioturbated muds are variably distributed across the subaqueous delta. • Most modern deltas have subaerial and subaqueous delta parts, i.e., a bathymetric double clinoform. • River sediment discharge, especially the finer fraction, reaches the subaqueous delta aided by tides, waves and fluid muds. • Processes involved in grain-size partitioning to subaqueous deltas demonstrate why they are mud-prone. • Subaqueous deltas show tide to wave domination fairway changes, but sometimes the opposite. • Lack of double clinoform recognition can lead to shoreline placement and classification errors. [ABSTRACT FROM AUTHOR]

Coastal erosion caused by extreme storms can reduce the value of beaches. Under the scenario of climate change, the storm intensity may increase and the resulting severe erosion can lead to disastrous damages on the beaches. Therefore, it is crucial to find appropriate measures and adaptation plans to conserve the beach from storm attacks. In this study, numerical models were applied to analyze the dune erosion in Boggil Beach, Korea, occurred by Typhoon Tapah in September 2019. Two models were used as Telemac-2D was run in larger domains for producing forcing conditions. XBeach was then applied to simulate the 2019 dune erosion after validation using observational data from a post-event field experiment performed in 2020. The model results showed reasonable agreement with the observational data except for the overestimation of erosion that was likely caused by characteristic pattern of sediment that was a mixture of sand and gravel and the accuracy of model results decreased due to the existence of gravel. The results also confirmed the locality of erosional damage by which the dune erosion was severest in the southern part of the beach. This locality was caused because the water depth was steeper in this area, which kept the wave energy in this area higher than that in the northern part. The uneven distribution of depth was induced by natural and anthropogenic causes. Three cases of model tests were performed to determine an appropriate measure to preserve the beach from future storm attacks – two were to place a submerged breakwater (SB), and one to place a submerged groin(SG). Although the SBs could directly protect the shore from erosion in the lee of the SBs, they could cause additional erosions at unexpected seabed areas. Although the SG was not the best in protecting the beach from the dune erosion, it could minimize the side effect. This measure was also environmentally friendly by keeping the sediments within the coastal cell around the SG so that the beach maintenance could be feasible through replenishment. In addition, the SG could also save the initial cost by reducing its size, and would be more effective, if the recovery process considered, because the SBs would disturb the onshore sediment motions under milder wave conditions. The results of this study can be applied for decision-making to establish future adaptation plans from storm impacts in Bonggil Beach.

This study explores the spatial distribution and the driving mechanisms of the wave‐induced cross‐shore flow within the shoreface and surf zone of a dissipative beach. Unpublished results from a field campaign carried out in early 2021 under storm wave conditions are presented and compared with the predictions from a state‐of‐the‐art phase‐averaged three‐dimensional circulation modeling system based on the vortex force formalism. Under storm wave conditions, the cross‐shore flow is dominated by a strong seaward‐directed current in the lower part of the water column. The largest current velocities of this return current are located in the surf zone, where the dissipation by depth‐induced breaking is most intense, but offshore‐directed velocities up to 0.25 m/s are observed as far as 4 km from the shoreline (≃12 m‐depth). Numerical experiments further highlight the key control exerted by non‐conservative wave forces and wave‐enhanced mixing on the cross‐shore flow across a transition zone, where depth‐induced breaking, whitecapping, and bottom friction all significantly contribute to the wave energy dissipation. Under storm conditions, this transition zone extended almost 6 km offshore and the cross‐shore Lagrangian circulation shows a strong seaward‐directed jet in the lower part of the water column, whose intensity progressively decreases offshore. In contrast, the surf zone edge appears clearly delimited under fair weather conditions and the seaward‐directed current is weakened by a near bottom shoreward‐directed current associated with wave bottom streaming in the shoaling region, such that the clockwise Lagrangian overturning circulation is constrained by an additional anti‐clockwise overturning cell at the surf zone edge. Plain Language Summary: As waves propagate toward the shore fluid parcels experience a net transport in the direction of wave propagation. This onshore mass transport is compensated by a near bed return flow, which dynamics remain poorly understood. This study combines measurements from a field campaign carried out in early 2021 in front of a gentle sloping beach and numerical modeling to explore the spatial distribution and the driving mechanisms of this wave‐induced cross‐shore flow. Both observations and model results show that the largest current velocities of this return current are located very close to the shoreline, where the wave breaking is the most intense, but values up to 0.25 m/s are observed as far as 4 km from the shoreline under storm conditions. Numerical experiments further highlight the key control exerted by the wave forces and the wave‐enhanced mixing, which induce very contrasted circulation patterns under fair weather or storm conditions and strongly constrain the vertical structure of the cross shore flow. Key Points: Field experiment at a dissipative beach with 6 m Hm0 at breaking and undertows reaching 0.25 m/s as far as 4 km from the shorelineAccurate reproduction of the cross‐shore hydrodynamics using a phase‐averaged 3D circulation modelWave dissipation by breaking locally increases seaward‐directed flows by over 100% compared to the surface Stokes drift velocity [ABSTRACT FROM AUTHOR]

Storm waves transport and sort coarse gravel along coasts. This fundamental process is important under changing sea‐levels and increased storm frequency and intensity. However, limited information on intra‐storm clast motion restricts theory development for coastal gravel sorting and coastal management of longshore transport. Here, we use smart boulders equipped with loggers recording underwater, real‐time, intra‐storm clast motion, and measured longshore displacement of varied‐mass marked boulders during storms. We utilize the unique setting of the Dead Sea shores where rapidly falling water levels allow isolating boulder transport during individual storms. Guided by these observations, we develop a new model quantifying the critical wave height for a certain clast mass mobilization. Then, we obtain an expression for the longshore clast displacement under the fluid‐induced pressure impulse of a given wave. Finally, we formulate the sorting enforced by wave‐height distributions during a storm, demonstrating how sorting is a direct manifestation of regional hydroclimatology. Plain Language Summary: Beaches connect terrestrial and marine environments, frequently near large population centers. Sea‐level rise and increased storm intensities threaten this environment, causing enhanced coastal erosion and damage to cities and infrastructure, along with loss of coastal tourism. We combine real‐time measurements of clast movement during a storm with a newly‐developed theoretical model. This allows predicting longshore sediment transport and determine critical wave heights for mobilization and alongshore movement of various clast sizes under a distribution of wave heights. The outcome is a quantitative, process‐based tool for coarse‐gravel motion and beach evolution, a key for coastal management. We show how the wave‐induced pressure force and impulse exerted on clasts dictates the longshore clast motion and sorting, and how sorting is a direct manifestation of regional hydroclimatology. Key Points: Storm waves sort clasts according to mass along the shores of the Dead Sea; clast motion is traced by marked and smart bouldersA newly developed model predicts the critical wave height for motion initiation and the total longshore transport of cobbles‐bouldersCoastal sorting is a direct manifestation of regional hydroclimatology, derived by hydrodynamic pressure‐induced impulse exerted on clasts [ABSTRACT FROM AUTHOR]

Featured Application: The video monitoring system used in this study can be applied for monitoring coastal processes of erosion and recovery and thus can be useful in designing beach protection/prevention plans for damage by storm waves. Once a beach is eroded by storm waves, it is generally recovered under milder wave conditions. To prevent or reduce damage, it is therefore important to understand the characteristics of the site-specific recovery process. Here, we present the results, based on a data set from a video monitoring system and wave measurements, of the recovery process in a pocketed beach located inside a bay where the shoreline retreated harshly (~12 m, on average, of beach width) during Typhoon TAPAH (T1917) in September 2019. It took about 1.5 years for the beach to be recovered to the level before the typhoon. During this period, the erosion and accretion were repeated, with the pattern highly related to the wave power ( P w ); most of the erosion occurred when P w became greater than 30 kWatt/m, whereas the accretion prevailed when P w was no greater than 10 kWatt/m. The recovery pattern showed discrepancies between different parts of the beach. The erosion during storm events was most severe in the southern part, whereas the northern shoreline did not significantly change even during TAPAH (T1917). In contrast, the recovery process occurred almost equally at all locations. This discrepancy in the erosion/accretion process was likely due to human intervention, as a shadow zone was formed in the northern end due to the breakwaters, causing disequilibrium in the sediment transport gradient along the shore. The results in this study could be applied in designing the protection plans from severe wave attacks by effectively estimating the size of coastal structures and by correctly arranging the horizontal placement of such interventions or beach nourishment. Although the application of these results should be confined to this specific site, the method using wave energy parameters as criteria can be considered in other areas with similar environments, for future planning of beach protection. [ABSTRACT FROM AUTHOR]

Existing hydrodynamic flow transport equations for coastal boulder transport are useful for estimating post-event the characteristics of extreme storm waves and tsunamis. However, the effect of suspended sediment concentration (SSC) on seawater density is normally ignored. This is unrealistic given that turbulent runup flows easily entrain available fine sediment. Proper consideration of SSC can be encouraged by including a mixed-fluid density coefficient (Cρ) as a multiplier for clear-seawater density, where elevated sediment content can be assumed and estimated. Minimum flow velocities required for boulder transport are shown to reduce as sediment concentrations increase. [ABSTRACT FROM AUTHOR]

Tsunamis and storm surges are among several hazards threatening the Atlantic coast of Morocco. During the last two decades, sedimentological deposits left by these events, in the form of fine-grained sediments (washover) and boulders, have been studied along the Moroccan shores to determine the return period of these events and how they fluctuate in terms of intensity. The present work investigates two new boulder fields located along the Safi coast. Field surveys were accomplished in the two areas to collect the position/elevation and dimensions of 164 boulders using a GPS/DGPS and a traditional meter, respectively. The field data was combined with hydrodynamic equations to estimate the minimum velocity and storm/tsunami wave height to move the measured boulders. In site 1, the boulders are situated on a rocky intertidal platform, while in the second, they are on the top of a cliff. For both sites, the size of the boulders ranges from 0.6 to 5.60 m, 0.54 to 3.6 m, and 0.27 to 1.5 m on the major (a), medium (b), and minor (c) axes, respectively. They reach a volume of up to 25.20 m3 and a weight of 55.44 t. The maximum distance and elevation recorded are around 41.77 m and 13 m, respectively. According to hydrodynamic equations, the coastal platform boulders (site 1) can be moved by tsunami waves with heights between 0.10 and 0.59 m, and storm waves from 0.42 to 2.37 m. To be displaced, the cliff-top boulders (site 2) need tsunami and storm waves with at least 5.91 and 8.64 m, respectively. The results from the field surveys and hydrodynamic equations suggest that both tsunami and storm waves can move the boulders in site 1. For the cliff top-boulders, the data favours tsunamis as a source for this deposit. • Platform and cliff-top boulders are present along the Safi coast. • The blocs reach a volume of up to 25.20 m3 and a weight of up to 55.44 t. • Boulders were moved by extreme wave events before 1954 CE. [ABSTRACT FROM AUTHOR]

Once a beach is eroded by storm waves, it is generally recovered under milder wave conditions. To prevent or reduce damage, it is therefore important to understand the characteristics of the site-specific recovery process. Here, we present the results, based on a data set from a video monitoring system and wave measurements, of the recovery process in a pocketed beach located inside a bay where the shoreline retreated harshly (~12 m, on average, of beach width) during Typhoon TAPAH (T1917) in September 2019. It took about 1.5 years for the beach to be recovered to the level before the typhoon. During this period, the erosion and accretion were repeated, with the pattern highly related to the wave power (Pw); most of the erosion occurred when Pw became greater than 30 kWatt/m, whereas the accretion prevailed when Pw was no greater than 10 kWatt/m. The recovery pattern showed discrepancies between different parts of the beach. The erosion during storm events was most severe in the southern part, whereas the northern shoreline did not significantly change even during TAPAH (T1917). In contrast, the recovery process occurred almost equally at all locations. This discrepancy in the erosion/accretion process was likely due to human intervention, as a shadow zone was formed in the northern end due to the breakwaters, causing disequilibrium in the sediment transport gradient along the shore. The results in this study could be applied in designing the protection plans from severe wave attacks by effectively estimating the size of coastal structures and by correctly arranging the horizontal placement of such interventions or beach nourishment. Although the application of these results should be confined to this specific site, the method using wave energy parameters as criteria can be considered in other areas with similar environments, for future planning of beach protection.

The knowledge of wave energy propagation in the shallow water allow us to understand the functioning of marine ecosystems and to give answers about several costal phenomena. In the Algerian coast, the waves are omnipresent with an energy that is stripped under different physical forms. The classification of areas with high hydrodynamic energy potential requires a large data flow, concerning the physical hydrodynamic parameters produced by this energy. In this study we have developed a numerical code based on various mathematical theories and equations describing the physical state of the wave, including the formulas of MUNK, Coastal Engineering Research Center, 'CERC' and of the French Central Hydraulics Laboratory, 'LCHF', based on the output data of the SWAN model. This code allowed us to measure several wave’s physical parameters sufficiently well in order to understand and quantify the energies transmitted along the coast. A spatial analysis of the obtained results allowed us to classify seven coastal stations with an average wave energy exceeding 20 kW/m in the stormy days.

Coastal boulder deposits (CBD), transported by waves at elevations above sea level and substantial distances inland, are markers for marine incursions. Whether they are tsunami or storm deposits can be difficult to determine, but this is of critical importance because of the role that CBD play in coastal hazard analysis. Equations from seminal work by Nott (1997), here referred to as the Nott Approach, are commonly employed to calculate nominal wave heights from boulder masses as a means to discriminate between emplacement mechanisms. Systematic review shows that this approach is based on assumptions that are not securely founded and that direct relationships cannot be established between boulder measurements and wave heights. A test using an unprecedented dataset of boulders moved by storm waves (with associated sea-state data) shows a lack of agreement between calculations and actual wave heights. The equations return unrealistically large heights, many of which greatly exceed sea states occurring during the boulder-moving storms. This underscores the finding that Nott-Approach wave-height calculations are unreliable. The result is general, because although the field data come from one region (the Aran Islands, Ireland), they represent a wide range of boulder masses and topographic settings and present a valid test of hydrodynamic equations. This analysis demonstrates that Nott Approach equations are incapable of distinguishing storm waves from tsunami transport and that wave heights hindcast from boulder masses are not meaningful. Current hydrodynamic understanding does not permit reliable computation of wave height from boulder measurements. A combination of field, numerical, and experimental approaches is required to quantify relationships between wave power and mass transport onshore. Many CBD interpreted as tsunami deposits based on Nott-Approach analysis may in fact have been emplaced during storms and should therefore be re-evaluated. This is especially important for CBD that have been incorporated into long-term coastal risk assessments, which are compromised if the CBD are misinterpreted. CBD dynamics can be better determined from a combination of detailed field measurements, modeling, and experiments. A clearer understanding of emplacement mechanisms will result in more reliable hazard analysis.

This paper shows simulations of high waves over different bathymetries to collect statistical information, particularly kurtosis and crest exceedance, that quantifies the occurrence of exceptionally extreme waves. This knowledge is especially pertinent for the design and operation of marine structures, safe ship trafficking, and mooring strategies for ships near the coast. Taking advantage of the flexibility to perform numerical simulations with HAWASSI software, with the aim of investigating the physical and statistical properties for these cases, this paper investigates the change in wave statistics related to changes in depth, breaking and differences between long- and short-crested waves. Three different types of bathymetry are considered: run-up to the coast with slope 1/20, waves over a shoal, and deep open-water waves. Simulations show good agreement in the examined cases compared with the available experimental data and simulations. Then predictive simulations for cases with a higher significant wave height illustrate the changes that may occur during storm events.

The objective of this paper is to characterize the pattern and behavior of incident highest energy waves that reach the coast of Espírito Santo (ES), Brazil. Buoy data and shallow water wave simulations were used to identify this pattern. It was found that the waves of greater energy occur due to the approach of cyclonic systems that generate stormy conditions from the southwest. However, the coastline is almost entirely protected from these waves. The slight inflection of the swell waves to the south or southeast exposes different segments of the coast in the face of storms. In addition, the stable conditions associated with the action of the South Atlantic Subtropical Anticyclone generate the greatest energy for the coastline when the winds reach near gale (Beaufort 7). Finally, it is concluded that the greatest swell captured by reanalysis models or oceanic buoys occur from the southeast to the southwest quadrant (bad weather). However, the analysis of waves in the near shore zone reveals that the high wind conditions of “good weather” are the ones that direct the highest wave energy to the beach stations. Coastal defense projects should consider specific beach site wave information in order to succeed. [ABSTRACT FROM AUTHOR]

The numerical modeling of wind and sea waves with the WAVEWATCH III discrete spectral model is used to analyze their frequency in the range of hazardous values in the Sea of Japan and the Sea of Okhotsk in 1979-2018. It is found that, in most cases, these events are caused by the passage of tropical cyclones. Some long-term trends are revealed in the frequency of hazardous phenomena (wind and sea waves) and tropical cyclones passing over the Far Eastern seas. The relation between the passage of tropical cyclones and the atmospheric circulation features over some parts of the region is found. [ABSTRACT FROM AUTHOR]

The Żonqor coastline, southeast Malta, displays an exceptional range of geomorphic signatures of extreme coastal events. This paper brings together evidence acquired from a field survey, analysis of time-sequential imagery, and hydrodynamic modelling to investigate the histories of boulder groups identified by their intrinsic and contextual characteristics. Clear differences are revealed between the distribution of boulders recently moved and those of considerable age. Tracking the movement of boulders since 1957 confirms that storms of surprisingly frequent interval are capable of complex boulder movements, including lifting of megaclasts. Scrutiny of the ancient boulders, including weathering features and fascinating landward-facing (reverse) imbrication, cautiously suggests tsunami as the agent for their emplacement. A novel method is developed for depicting the velocity decay profiles of hypothetical waves, which overcomes some of the limitations of the Nott approach. Applied here, the wave run-up context further sets the ancient movers apart from their recent mover companions. The combined evidence implies a palimpsestic landscape where storm waves are regular geomorphic agents that add to and rework the distribution of boulders close to the shoreline, but over long time periods the landscape becomes reset by tsunami—a concept that is of value to agencies in Malta responsible for coastal safety, planning and management.

The 450-m long spit that extends westward from the northwest corner of Isla San Luis Gonzaga is one of the largest and most complex constructions of unconsolidated cobbles and boulders found anywhere in Mexico’s Gulf of California. The material source derives from episodic but intense storm erosion along the island’s andesitic cliff face with steep northern exposures. A well-defined marine terrace from the late Pleistocene cuts across the same corner of the island and provides a marker for the subsequent development of the spit that post-dates tectonic-eustatic adjustments. A total of 660 individual andesite clasts from seven transects across the spit were measured for analyses of change in shape and size. These data are pertinent to the application of mathematical formulas elaborated after Nott (2003) and subsequent refinements to estimate individual wave heights necessary for lift from parent sea cliffs and subsequent traction. Although the ratio of boulders to clasts diminishes from the proximal to distal end of the structure, relatively large boulders populate all transects and the average wave height required for the release of joint-bound blocks at the rocky shore amounts to 5 m. Based on the region’s historical record of hurricanes, such storms tend to decrease in intensity as they migrate northward through the Gulf of California’s 1100-km length. However, the size and complexity of the San Luis Gonzaga spit suggests that a multitude of extreme storm events impacted the island in the upper gulf area through the Holocene time, yielding a possible average growth rate between 7 and 8 m/century over the last 10,000 years. In anticipation of future storms, a system to track the movement of sample boulders should be emplaced on the San Luis Gonzaga spit and similar localities with major coastal boulder deposits.

Video monitoring systems (VMS) have been used for beach status observation but are not effective for examining detailed beach processes as they only measure changes to the shoreline and backshore. Here, we extracted longshore sediment transport (LST) from VMS in order to investigate long- and short-term littoral processes on a pocket beach. LST estimated by applying one-line theory, wave power, and the oblique angle of incident waves were used to understand shoreline changes caused by severe winter storms. The estimated LST showed good agreement with the shoreline changes because the sediments were trapped at one end of the pocket beach and the alongshore direction of transported sediments was corresponded to the direction of LST. The results also showed that the beach that was severely eroded during storms was also rapidly recovered following the evolution of LST, which indicates that the LST may play a role in the recovery process while the erosion was mainly caused by the cross-shore transport due to storm waves. After the beach was nourished, beach changes became more active, even under lower wave energy conditions, owing to the equilibrium process. The analysis presented in this study could be applied to study inhomogeneous beach processes at other sites.

This study is concerned with large boulders located along exposed shorelines in higher latitudes, which have become dislocated onshore by winter storms and have moved against gravity. To identify the transportation processes that these boulders have undergone in detail, their direct investigation during storm wave conditions is necessary, or at least near time inspections after extraordinary wave events. As both methods are rare, a wide range of questions and contradictions with regards to the processes that have acted on these boulders, remains. Despite a lack of applicable methods as for fine sediments, the depositional environment and processes of boulder movement can be determined from geomorphologic evidence in the landscape itself. Examples are presented in this paper. To progress understanding of boulders in rocky coastal environments, qualitative and quantitative data are acquired during a near time inspection following extreme storms in winter 2013/14 with special focus on an extraordinary boulder site near Doolin at the entrance to Galway Bay (central west coast of Ireland). The comparison of these data to previously published research on coastal boulder movement results in agreements and discrepancies (e.g. on boulder forms and mode of transport, difference in wave and bore transport) which are discussed. [ABSTRACT FROM AUTHOR]

Boulders are frequently dislodged from rock platforms, transported and deposited along coastal zones by high-magnitude storm waves or tsunamis. Their size and shape are often controlled by the thickness of bedding planes as well as by high-angle to bedding fracture network. We investigate these processes along two coastal areas of Favignana Island by integrating geological data for 81 boulders, 49 rupture surfaces (called sockets ) and fracture orientation and spacing with four radiocarbon dates, numerical hydrodynamic analysis, and hindcast numerical simulation data. Boulders are scattered along the carbonate platform as isolated blocks or in small groups, which form, as a whole, a discontinuous berm. Underwater surveys also highlight free boulders with sharp edges and sockets carved out in the rock platform. Boulders are composed of ruditic- to arenitic-size clastic carbonates. Their size ranges from 0.6 to 3.7 m, 0.55 to 2.4 m, and 0.2 to 1 m on the major (A), medium (B), and minor (C) axes, respectively. The highest value of mass estimation is 12.5 t. Almost all of boulders and sockets are characterized by a tabular or bladed shape. The comparisons between a) the fractures spacing and the length of A- and B-axes, and b) the frequency peaks of C-axis with the recurrent thickness of beds measured along the coastal zone demonstrate the litho-structural control in the size and shape of joint-bounded boulders. These comparisons, together with the similarity between the shapes of the boulders and those of the sockets as well as between the lithology of boulders and the areas surrounding the sockets, suggest that blocks originate by detachment from the platform edge. Thus, the most common pre-transport setting is the joint-bounded scenario. Hydrodynamic equations estimate that the storm wave heights necessary to initiate the transport of blocks diverge from ~ 2 m to ~ 8 m for joint-bounded boulders and from few tens of centimeters up to ~ 11 m for submerged boulders. The comparison between the wave heights at the breaking point of the coastal zones with the results of hydrodynamic equations shows that waves approaching the coastline are able to transport all surveyed boulders. Our data suggest that boulders have been transported by several storm events, even in very recent times. [ABSTRACT FROM AUTHOR]

Before-and-after photos of supratidal coastal boulder deposits (CBD) in the west of Ireland show that storms in the winter of 2013–2014 transported boulders at elevations up to 29 m above high water, and at inland distances up to 222 m. Among the clasts transported are eighteen weighing more than 50 t, six of which exceed 100 t. The largest boulder moved during those storms weighs a fairly astonishing 620 t. The boulders moved in these recent storms provide pinning points for mapping storm-wave energies on coasts: their topographic positions mark elevations and distances inland reached by wave energies sufficient to dislocate those specific masses. Taken together, the CBD data reveal general relationships that shed light on storm-wave hydrodynamics. These include a robust correlation (inverse exponential) between maximum boulder mass transported and emplacement height above high water: the greater the elevation, the smaller the maximum boulder size, with a dependency exponent of about -0.2 times the elevation (in metres). There is a similar relationship, although with a much smaller rate-of-change (exponent -0.02), between boulder mass and distance inland, which holds from the shoreline in to about 120 m. Coastal steepness (calculated as the ratio of elevation to inland distance) seems to exert the strongest control, with an inverse power-law relationship between maximum boulder mass and slope ratio: the more gentle the topography, the larger the moved boulders. Quantifying CBD dynamics helps us understand the transmission of wave energies inshore during high-energy storm events. The transported boulders documented here are larger than many of those interpreted to have been moved by tsunami in other locations, which means that boulder size alone cannot be used as a criterion for distinguishing between tsunami and storm emplacement of CBD. The biggest blocks—up to 620 t—are new maxima for boulder mass transported by storm waves. We predict, however, that this record will not last long: the 2013–2014 storms were strong but not extreme, and there are larger boulders in these deposits that didn't move on this occasion. Bigger storms will surely move larger clasts, and clasts at greater distances from the shoreline. These measurements and relationships emphasise the extreme power of storm waves impacting exposed coastlines, and require us to rethink the upper limits of storm wave energy at coasts. [ABSTRACT FROM AUTHOR]

Large boulder accumulations have been observed on various coasts bordering the Mediterranean and have been associated with extreme wave events such as powerful storms or tsunamis. This study provides an in-depth analysis of 430 boulder deposits, located along a 3.5 km stretch of rocky coast situated on the SE of the Maltese Islands. It includes a geomorphometric analysis of the observed boulders and use of numerical modelling to estimate wave height required to initiate boulder movement. Comparisons of aerial imagery over a period of 46 years have made it possible to identify boulder movement that could only be attributed to storm waves, given that no local tsunamigenic event has been recorded over this time period. Positioned in the central Mediterranean, the Maltese Islands are exposed to potential tsunamis generated by seismic activity associated with the Malta Escarpment, and the Calabrian and Hellenic arcs. Although imprints from historic tsunami impact cannot be excluded, results indicate that the area is exposed to strong storm waves that are capable of displacing some of the very large boulders observed on site. [ABSTRACT FROM AUTHOR]

This paper reports the post-disaster survey results of storm surge and waves due to Super Typhoon Meranti (local name: Ferdie), along the coastline of the province of Batanes, Philippines. The survey was conducted by a joint survey team of the University of Tokyo and University of the Philippines from 9 to 12 October 2016, about one month after the disaster. Water levels in the inundated area or runup heights were measured at 37 locations along the coast of the islands of Batan and Sabtang by interviewing local residents and by examining wave runup evidences remaining along the coast. Obtained runup and inundation levels showed significant variations along the coast of islands and higher levels were found on the coast facing north. Especially at Ivana, a small coastal community located at the southwestern tip of the island of Batan, the coast was covered by a convex-shaped fringing reef and observed inundation heights were locally concentrated behind the peak of the convex-shaped reef. [ABSTRACT FROM AUTHOR]

Recent research on short-term topographic change in the Yangtze Estuary channel under storm surge conditions is briefly summarized. The mild-slope, Boussinesq and action balance equations are compared and analyzed. The action balance equation, SWAN, was used as a wave numerical model to forecast strong storm waves in the Yangtze Estuary. The spherical coordinate system and source terms used in the equation are described in this paper. The significant wave height and the wave orbital motion velocity near the bottom of the channel during 20 m/s winds in the EES direction were simulated, and the model was calibrated with observation data of winds and waves generated by Tropical Cyclone 9912. The distribution of critical velocity for incipient motion along the bottom was computed according to the threshold velocity formula for bottom sediment. The mechanism of rapid deposition is analyzed based on the difference between the root-mean-square value of the near-bottom wave orbital motion velocity and the bottom critical tractive velocity. The results show that a large amount of bottom sediments from Hengsha Shoal and Jiuduan Shoal are lifted into the water body when 20 m/s wind is blowing in the EES direction. Some of the sediments may enter the channel with the cross-channel current, causing serious rapid deposition. Finally, the tendency of the storm to induce rapid deposition in the Yangtze Estuary channel zone is analyzed.

Integrated assessment of possible soil degradation under cyclic loading caused by storm waves includes the analysis of hydrological data; the calculation of anticipated parameters of storm-wave amplitude-frequency spectrum and the corresponding shear forces; strength prediction based on experiments performed using the calculated wave parameters and loads; and the final analysis of soil behavior with regard to the time distribution of waves with different heights during the accepted storm activity period. The soil foundation stability was estimated for a site in the North Caspian shelf. [ABSTRACT FROM AUTHOR]

Sitting on the shore platform at Ben Buckler, the north-east headland of Bondi Beach, Sydney, is a large isolated boulder, weighing around 235 tons. In this article I analyse geomorphological explanations for, and historical representations of, the boulder, locally known as the Big Rock. Explanations for and representations of Bondi's Big Rock typically appear in discussions and debates about changes to the New South Wales coast and the impact of storm waves and tsunami. Geomorphologists date the Big Rock from a storm in July 1912 and have identified a range of wave sizes and forms to explain its presence. Yet, neither their explanations nor evidence have convinced a number of local residents who claim the rock existed before the 1912 storm. Bondi's Big Rock is thus a valuable reminder that geomorphological features are not fully formed subjects. Rather, they must be defined and contextualised in inordinately complex processes of explanation and representation that ultimately are always interpretations. [ABSTRACT FROM AUTHOR]

Cao, H.; Chen, Y.; Tian, Y., and Feng, W., 2016. Field investigation into wave attenuation in the mangrove environment of the South China Sea coast. Coastal mangroves form the land-sea interface and face an increasingly aggressive threat from ocean waves as a result of sea-level rise. This study investigates the buffering effect of mangroves on the coast of Leizhou Bay in the South China Sea under two different climates (normal windy weather and storm). By doing this, we aim to establish the exact wave damping rate due to the presence of mangroves and to study the wave and spectral characteristics of wave energy in the vegetated area. Wave gauges are mounted along a cross-shore transect to monitor the wave conditions during particular time periods. From the data analysis, we found that the recorded maximum significant wave height is 22.3 cm at the outermost station and remarkable wave damping was experienced within the mangrove troops of 100 meters. To evaluate the wave dissipation on the mudflat, an empirical expression is proposed on the basis of the field data. In this way, the net vegetation-induced wave dissipation is quantified separately. The spectral analysis of wave energy shows the modalities of frequency-dependent wave energy dissipation under different weather conditions. From the results, we conclude that the wave height was strictly subjected to the concurrent water depth even under the storm condition. The relative water depth (to the wave height) determined wave generation or dissipation on the mudflat. Despite the existence of dissipation by the mudflat, wave energy was majorly attenuated by the mangrove system. The wind growth of wave energy is of great significance when studying the spectral characteristics of wave energy during storm conditions. [ABSTRACT FROM AUTHOR]

The results ofnumerical simulation of storm waves near the northeastern coast ofthe Black Sea using different wind forcing (CFSR reanalysis, GFS forecast, and WRF reanalysis and forecast) are presented. The wave modeling is based on the SWAN spectral wave model and the high-resolution unstructured grid for the Tsemes Bay. The quality estimates of wave simulation results for various wind forcing are provided by comparing the model results with the instrumental data on wind waves in the Tsemes Bay. It is shown that the forecast of the maximum wave height for some storms using the WRF wind forcing is more accurate than that based on the GFS forcing. [ABSTRACT FROM AUTHOR]

An intertidal rocky platform tucked in behind a rocky headland on open-ocean Gibson Beach, near Raglan, supports an agglomeration of cobble- to large-boulder-sized clasts of Cenozoic sandstone and limestone. Rather than exhibiting just point contacts, many larger clasts are tightly interlocked and fitted with their neighbours and/or the underlying platform bedrock. Clast interface geometry relates to the strength contrast between adjacent rock types, linked to their calcite (cement) content. The end-product is an armoured, highly stable framework of boulder clasts resembling a giant three-dimensional jigsaw puzzle. While the direct impact of breaking waves likely plays a role in in situ jostling of boulders, we speculate that mechanical abrasion and fitting between larger clasts may also be promoted and maintained by in situ microvibration of the boulders as a consequence of wave-induced microseismic shaking within the cliff-backed rocky platform and headland, especially during major storm wave assault from the southwest. [ABSTRACT FROM PUBLISHER]

Coastal geomorphic processes associated with high-energy storm events are difficult to estimate over recent geological history, though their frequency and magnitude are important to assess in order to understand present-day coastal vulnerability. Studying ancient coastal boulder deposits can shed light on the previous physical conditions necessary for their deposition. In this study, we estimated the physical processes required to move reef-derived coral boulders on the east coast of Ko Samui, a rapidly developing tourist island off eastern peninsular Thailand. The position and dimensions of 97 coral boulders (weight: mean 2.9 t, max. 12.7 t; transport distance: max. 125 m) were measured at two sites and dated using uranium/thorium methods. Flow velocities of 2.3–8.6 m/s were required to transport the measured boulders, with individuals deposited up to 4.7 m above mean sea level. Age-dating suggests that events capable of the highest flow velocities occurred around AD 1600 and AD 1750. These were probably driven by tropical cyclones (typhoons). Boulder transport by events of similar magnitude has not been detected within the last 250 years. The non-occurrence of similar events in living memory has implications for hazard perceptions at this important tourist destination. However, there is also evidence of substantial Holocene sea-level changes in the Gulf of Thailand, as observed at nearby Ko Phaluai. This potentially offers a challenge for the interpretation of older boulders dating from the mid-Holocene, as sea level may have been more than 2 m higher than present. Thus, studies using coral boulders as a proxy for past storm-wave conditions must consider the broader sea-level history, and are probably best limited to the period post-2000 BP in the Gulf of Thailand. [ABSTRACT FROM AUTHOR]

Copyright of Revista Tamoios is the property of Editora da Universidade do Estado do Rio de Janeiro (EdUERJ) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coastal barriers are ubiquitous globally and provide a vital protective role to valuable landforms, habitats and communities located to landward. They are, however, vulnerable to extreme water levels and storm wave impacts. A detailed record of sub-annual to annual; decadal; and centennial rates of shoreline retreat in frontages characterized by both high (> 3 m) and low (< 1 m) dunes is established for a barrier island on the UK east coast. For four storms (2006-2013) we match still water levels and peak significant wave heights against shoreline change at high levels of spatial densification. The results suggest that, at least in the short-term, shoreline retreat, of typically 5-8 m, is primarily driven by individual events, separated by varying periods of barrier stasis. Over decadal timescales, significant inter-decadal changes can be seen in both barrier onshore retreat rates and in barrier extension rates alongshore. Whilst the alongshore variability in barrier migration seen in the short-term remains at the decadal scale, shoreline change at the centennial stage shows little alongshore variability between a region of barrier retreat (at 1.15 m a−1) and one of barrier extension. A data-mining approach, synchronizing all the variables that drive shoreline change (still water level, timing of high spring tides and peak significant wave heights), is an essential requirement for validating models that predict future shoreline responses under changing sea level and storminess. © 2016 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Stephenson, W.J. and Abazović, A. 2016. Measuring Coastal Boulder Movement Under Waves Using Tri-Axial Accelerometers. 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. 607-611. Coconut Creek (Florida), ISSN 0749-0208. Boulder entrainment under tsunami or storm wave conditions has been a topic of interest among coastal geomorphologists for the last 25 years. Efforts have been directed to understanding the dynamic conditions under which boulder entrainment occurs and in particular the energy levels required to move boulders of specific sizes. Recent focus on storm waves has highlighted the complexity of the process and that more energetic tsunami waves are not always needed to move larger boulders. Consequently attempts have been made to develop better empirical equations to predict wave height or flow velocity and differentiate between storm waves and tsunami. However, data collection methods are restricted to hindcasting flow conditions based on boulder size, the chosen empirical equations and assumptions regarding historical storm or tsunami events. Significant advances could be made using real time entrainment data of boulder movement alongside flow conditions. This is particularly true if movement type, e.g. suspension, rolling or sliding can be distinguished. This paper demonstrates the use of small and inexpensive tri-axial accelerometers manufactured by Gulf Coast Data Concepts. The accelerometers were placed in PVC water tight housing then located in holes cored into boulders and deployed in conjunction with wave pressure transducers on the shore platform. Movement of 4 boulders were observed by logging real-time accelerations during a 5 day deployment. Preliminary data demonstrated that boulders rolled and moved up to 3 m in a westerly direction, while wave heights were less than 0.7 m, demonstrating of the viability of this technique. [ABSTRACT FROM AUTHOR]

Extensive beaches located near the Mexico-USA border play an important role in the economy of the city of Playas de Rosarito, Mexico. Intense beach erosion occurred during the winter 1998 as a result of a very energetic wave regime associated to ENSO-El Niño event, in combination with high water levels. The severity of these conditions caused flooding and destruction of several houses on the beach. Recreational and protection capabilities of the beach were severely diminished. Profile comparison showed that maximum volume of sand removed from the subaerial beach was 66.9x10-3 m3/m/day with an average recession of 2.3 m/day. The maximum shoreward displacement along the study period was 66 m. The profile height was up to 3.5 m lower than the initial profile, so a long period of mild wave conditions is needed to restore the initial profile height. The role played by the highly mobile gravel deposit along the northern portion of the study area need to be assessed.

In the winter, in the East Sea (ES), storm waves due to moving developed lows are frequently reported and cause extensive coastal disasters. During October 2006, there were extensive damages along the east Korean coast due to high storm waves induced by winter storms passing over the ES. This paper investigates the performance of a wave model, WAVEWATCH III, for the rough sea conditions in October 2006 with respect to the wind input and dissipation terms because the wave-breaking dissipation is the least known source term, which acts as a tuning knob for the closure of the action balance equation. Three package-like wind input-dissipation parameterizations, the WAM3 type (WAM-equiv), Tolman and Chalikov terms (TC96), and WAM4 type and its variant (WAM4+), are used experimentally for their performances under the same wind forcing obtained from atmospheric modelling with WRF. Overall, all experiments illustrate good accordance with observed wave characteristics. Among them, the WAM4+ results exhibit the best performance based on the Taylor diagram and index of agreement. In terms of dissipation behaviour, the TC96 results depict high energy losses at high frequency over 0.25 Hz, whereas the WAM-equiv runs display less dissipation at the same frequency. The WAM4+ results lie between those of the WAM-equiv and TC96. [ABSTRACT FROM AUTHOR]

ABSTRACT Few studies of wave processes on shore platforms have addressed the hydrodynamic thresholds that control wave transformation and energy dissipation, especially under storm conditions. We present results of a field experiment conducted during a storm on a sub-horizontal shore platform on the east coast of Auckland, New Zealand. Small (<0.5 m) locally generated waves typically occur at the field site, whereas during the experiment the offshore wave height reached 2.3 m. Our results illustrate the important control that platform morphology has on wave characteristics. At the seaward edge of the platform a scarp abruptly descends beneath low tide level. Wave height immediately seaward of the platform was controlled by the incident conditions, but near the cliff toe wave height on the platform was independent of incident conditions. Results show that a depth threshold at the seaward platform edge > 2.5 times the gravity wave height (0.05-0.33 Hz) is necessary for waves to propagate onto the platform without breaking. On the platform surface the wave height is a direct function of water depth, with limiting maximum wave height to water depth ratios of 0.55 and 0.78 at the centre of the platform and cliff toe, respectively. A relative 'platform edge submergence' (water depth/water height ratio) threshold of 1.1 is identified, below which infragravity (<0.05 Hz) wave energy dominates the platform energy spectra, and above which gravity waves are dominant. Infragravity wave height transformation across the platform is governed by the relative platform edge submergence. Finally, the paper describes the first observations of wave setup on a shore platform. During the peak of the storm, wave setup on the platform at low tide (0.21 m) is consistent with measurements from planar sandy beaches, but at higher tidal stages the ratio between incident wave height and maximum setup was lower than expected. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Cliff-top storm deposits (CTSDs) occur south of Morgan Bay, South Africa at elevations varying from ±55- to 63m. These occur as a ±10m-wide horizontal fringe of shell breccia mixed into a very thin (>15cm) sandy soil on the cliff top platform. Visually it is evident that the shell breccia is of various ages. Comparisons with proven wave breccia from this area indicate the same source. We suggest that this breccia was deposited as fall-out from wave and wind-borne plumes produced by wave bores striking the cliff base. These bores would likely have been produced by waves at least ~40m in height. Alternative interpretations, such as a perched marine desposit or tsunamiite are rejected in favour of CTSDs produced by multiple large wave events. [ABSTRACT FROM AUTHOR]

Functional data analysis (FDA) is a set of tools developed to perform statistical analysis on data having a functional form. In our case we consider the one-dimensional wave surface profiles registered during a North-Sea storm as functional data. The data is split into 20 min intervals within which an individual wave is defined as the profile between two consecutive downcrossings. After registration of these individual waves to the interval [0, 1], the mean wave profile for the entire 20 min interval is obtained along with the first two derivatives of this mean profile. We analyze the shape of these mean waves and their derivatives and show how they change as a function of the significant wave height, which is a measure of the severity of the sea for the corresponding time interval. We also look at the evolution of the energy, as represented by the phase diagram, as a function of significant wave height. The results show the asymmetry in vertical and horizontal scales for real data. Comparison with a Gaussian wave simulation model calculated from the actual wave spectra shows important differences in symmetry and shape of the average wave and seem to indicate that the greatest difference in the distribution of energy during the wave cycle lies in the second and fourth quarters of the wave period. FDA can be applied to derive information on the individual and average wave profiles and also provide an understanding of the variation in energy throughout the wave phase. [ABSTRACT FROM AUTHOR]

This study investigates interactions between waves, water levels and currents at the mouth of the second largest estuary in Europe (the Tagus Estuary, Portugal) under storm waves, combining field observations and a three-dimensional fully coupled wave-current modelling system. Tidal-induced water depth variations substantially modulate waves over the ebb shoal. During energetic conditions, low tide levels promote depth-limited wave breaking and energy transfer towards higher harmonics (triad interactions), which reduces wave heights and periods. Furthermore, for a given water level, tidal currents also influence wave propagation and drive strong modulations over shallow regions characterized by cross-channel current gradients. Flood currents change the mean wave direction by about 10–15° and tend to focus the wave energy flux towards coastal regions of the southern margin compared to a run without currents (20 to 30% increase of wave heights), while ebb currents reduce the wave heights. In addition, model results suggest that the saturation level associated with wave and current conditions at shallow locations may be close to the threshold where waves start to dissipate by whitecapping. At the peak of the storm, waves become a main driver of the circulation at the mouth scale, even in the 45-m deep main channel. Wave breaking acceleration over the ebb-shoal locally increases flood currents by 50 to 300% and reduces ebb currents by 20 to 50%. • Wave-current interactions at a large estuary mouth are analysed under storm waves. • Refraction of waves by currents explains up to 30% of the modulation of wave heights. • Wave-breaking acceleration is a major driver of the circulation at the mouth scale. [ABSTRACT FROM AUTHOR]