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Breaking wave
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Plunging breaker
Large wave breaking
In fluid dynamics and nautical terminology, a breaking wave or breaker is a wave with enough energy to "break" at its peak, reaching a critical level at which linear energy transforms into wave turbulence energy with a distinct forward curve. At this point, simple physical models that describe wave dynamics often become invalid, particularly those that assume linear behaviour.
The most generally familiar sort of breaking wave is the breaking of water surface waves on a coastline. Wave breaking generally occurs where the amplitude reaches the point that the crest of the wave actually overturns. Certain other effects in fluid dynamics have also been termed "breaking waves", partly by analogy with water surface waves. In meteorology, atmospheric gravity waves are said to break when the wave produces regions where the potential temperature decreases with height, leading to energy dissipation through convective instability; likewise, Rossby waves are said to break[1] when the potential vorticity gradient is overturned. Wave breaking also occurs in plasmas,[2] when the particle velocities exceed the wave's phase speed. Another application in plasma physics is plasma expansion into a vacuum, in which the process of wave breaking and the subsequent development of a fast ion peak is described by the Sack-Schamel equation.
A reef or spot of shallow water such as a shoal against which waves break may also be known as a breaker.[citation needed]
Types
[edit]
Breaking of water surface waves may occur anywhere that the amplitude is sufficient, including in mid-ocean. However, it is particularly common on beaches, because wave heights are amplified in the region of shallower water because the group velocity is lower there .
There are four basic types of breaking water waves. They are spilling, plunging, collapsing, and surging.[3]
Spilling breakers
[edit]When the ocean floor has a gradual slope, the wave will steepen until the crest becomes unstable, resulting in turbulent whitewater spilling down the face of the wave. This continues as the wave approaches the shore, and the wave's energy is slowly dissipated in the whitewater. Because of this, spilling waves break for a longer time than other waves, and create a relatively gentle wave. Onshore wind conditions make spillers more likely.
Plunging breakers
[edit]A plunging wave occurs when the ocean floor is steep or has sudden depth changes, such as from a reef or sandbar. The crest of the wave becomes much steeper than a spilling wave, becomes vertical, then curls over and drops onto the trough of the wave, releasing most of its energy at once in a relatively violent impact. A plunging wave breaks with more energy than a significantly larger spilling wave. The wave can trap and compress the air under the lip, which creates the "crashing" sound associated with waves. With large waves, this crash can be felt by beachgoers on land. Offshore wind conditions can make plungers more likely.
If a plunging wave is not parallel to the beach (or the ocean floor), the section of the wave which reaches shallow water will break first, and the breaking section (or curl) will move laterally across the face of the wave as the wave continues. This is the "tube" that is so highly sought after by surfers (also called a "barrel", a "pit", and "the greenroom", among other terms). The surfer tries to stay near or under the crashing lip, often trying to stay as "deep" in the tube as possible while still being able to shoot forward and exit the barrel before it closes. A plunging wave that is parallel to the beach can break along its whole length at once, rendering it unrideable and dangerous. Surfers refer to these waves as "closed out".
Collapsing
[edit]Collapsing waves are a cross between plunging and surging, in which the crest never fully breaks, yet the bottom face of the wave gets steeper and collapses, resulting in foam.
Surging
[edit]Surging breakers originate from long period, low steepness waves and/or steep beach profiles. The outcome is the rapid movement of the base of the wave up the swash slope and the disappearance of the wave crest. The front face and crest of the wave remain relatively smooth with little foam or bubbles, resulting in a very narrow surf zone, or no breaking waves at all. The short, sharp burst of wave energy means that the swash/backwash cycle completes before the arrival of the next wave, leading to a low value of Kemp's phase difference (< 0.5). Surging waves are typical of reflective beach states. On steeper beaches, the energy of the wave can be reflected by the bottom back into the ocean, causing standing waves.
Physics
[edit]
Spilling breaker
Plunging breaker
Collapsing breaker
Surging breaker
Different breaking-wave types, drawn after photos from a lab experiment, can be associated with the value of the Iribarren number.
As ocean surface waves enter shallow water, the water particle velocities begin to move faster relative to the speed of the waveform. As a result, the waveform becomes unstable and the crest of the wave overturns, which is known as the wave breaking process.[4] During breaking, a deformation (usually a bulge) forms at the wave crest, either leading side of which is known as the "toe".[clarification needed] Parasitic capillary waves are formed, with short wavelengths. Those above the "toe" tend to have much longer wavelengths. This theory is anything but perfect,[clarification needed] however, as it is linear. There have been a couple non-linear theories of motion (regarding waves). One put forth uses a perturbation method to expand the description all the way to the third order, and better solutions have been found since then. As for wave deformation, methods much like the boundary integral method and the Boussinesq model have been created.
It has been found that high-frequency detail present in a breaking wave plays a part in crest deformation and destabilization. The same theory expands on this, stating that the valleys of the capillary waves create a source for vorticity. It is said that surface tension (and viscosity) are significant for waves up to about 7 cm (3 in) in wavelength.[5]
These models are flawed, however, as they can't take into account what happens to the water after the wave breaks. Post-break eddy forms and the turbulence created via the breaking is mostly un-researched. Understandably, it might be difficult to glean predictable results from the ocean.[citation needed]
After the tip of the wave overturns and the jet collapses, it creates a very coherent and defined horizontal vortex. The plunging breakers create secondary eddies down the face of the wave. Small horizontal random eddies that form on the sides of the wave suggest that, perhaps, prior to breaking, the water's velocity is more or less two dimensional. This becomes three dimensional upon breaking.[citation needed]
The main vortex along the front of the wave diffuses rapidly into the interior of the wave after breaking, as the eddies on the surface become more viscous. Advection and molecular diffusion play a part in stretching the vortex and redistributing the vorticity, as well as the formation turbulence cascades. The energy of the large vortices are, by this method, transferred to much smaller isotropic vortices.
Experiments have been conducted to deduce the evolution of turbulence after break, both in deep water and on a beach.
A theoretical limit on the steepness of non-breaking waves in finite depth is given by the Miche criterion, derived by French engineer Robert Miche in 1944.[6][7][8]
See also
[edit]- Iribarren number – Dimensionless parameter
- Wave turbulence – Set of nonlinear waves deviated far from thermal equilibrium
References
[edit]- ^ "AGU – American Geophysical Union". AGU.
- ^ Arkhipenko, V.I.; Gusakov, E.Z.; Pisarev, V.A.; Simonchik, L.V. (June 2002). Dynamics of the Plasma Wave Breaking Phenomena (PDF). 29th EPS Conference on Plasma Phys. and Contr. Fusion. Montreux, Switzerland. Archived from the original (PDF) on 28 September 2011. Retrieved 5 November 2022.
- ^ Sarpkaya, Turgut; Isaacson, Michael (1981). Mechanics of wave forces on offshore structures. Van Nostrand Reinhold. p. 277. ISBN 978-0-442-25402-5.
- ^ Chase, Jonathan (March 2025). "Quantifying statistical characteristics of breaking waves in an idealized fringing reef environment: experiment and non-hydrostatic XBeach simulation". International Journal of Ocean and Coastal Engineering. 6 (1n04). doi:10.1142/S2529807025500010.
- ^ Lighthill, M. J. (1978). Waves in fluids. Cambridge University Press. pp. 223–225 & 232–235. ISBN 0-521-29233-6. OCLC 2966533.
- ^ Miche, M. (1944), "Mouvements ondulatoires de la mer en profondeur constante ou décroissante. Forme limite de la houle lors de son déferlement. Application aux digues maritimes." [Wave motions of the sea in constant or decreasing depth: limiting form of the wave at breaking. Application to maritime structures.], Annales des Ponts et Chaussées (in French), 114 (1): 25–78
- ^ Holthuijsen, L.H. (2007), Waves in Oceanic and Coastal Waters, Cambridge University Press, p. 242, ISBN 978-1139462525
- ^ Goda, Y. (2010), Random Seas and Design of Maritime Structures (3rd ed.), World Scientific, p. 213, ISBN 978-9814282406
External links
[edit]
Wikimedia Commons has media related to Breaking water waves.
- Oceans and margins, Earth Science Australia
- Super Slow Motion Laboratory Wave Breaking: Side View. on YouTube
- Super Slow Motion Laboratory Wave Breaking: Underwater View of Turbulence. on YouTube
Breaking wave
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Overview
Definition
A breaking wave occurs in surface gravity waves, which are oscillations at the air-water interface where gravity serves as the primary restoring force.[5] These waves become breakers when their height exceeds a critical threshold relative to the wavelength, causing the crest to become unstable and overturn or collapse under the combined effects of gravity and fluid dynamics.[6] This instability typically develops as the wave front steepens to a vertical or overhanging profile, marking the onset of breaking.[7] Key characteristics of a breaking wave include the rapid onset of instability at the wave front, often resulting in the formation of a turbulent bore or whitecap as the crest spills or plunges forward.[3] This process transitions the wave from coherent, progressive motion—where energy propagates with the wave—to dissipative turbulence, where kinetic energy is converted into heat and mixing.[8] The systematic study of breaking waves began with George Gabriel Stokes in 1880, who analyzed the limiting configuration of waves and highlighted the critical role of steepness in deep water conditions.[9] Stokes determined that breaking initiates when the ratio of wave height to wavelength surpasses approximately (or ), beyond which the wave profile cannot maintain stability without fracturing.[3]Significance
Breaking waves play a crucial role in oceanographic processes by driving turbulent mixing in the upper ocean layers, which facilitates the vertical transport of heat, momentum, and dissolved substances. This mixing enhances nutrient upwelling from deeper waters to the sunlit surface, supporting primary productivity in marine ecosystems and influencing global biogeochemical cycles.[10] Additionally, the turbulence generated by breaking waves promotes air-sea gas exchange, particularly for sparingly soluble gases like CO₂ and O₂, by increasing the air-water interface area through bubble entrainment and surface renewal.[11] These interactions contribute to climate regulation by modulating the ocean's capacity to absorb atmospheric CO₂ and distribute heat, thereby affecting global temperature patterns and ocean circulation.[12] In environmental contexts, breaking waves are the primary mechanism behind whitecapping during storms, where intense wave action fractures the sea surface and ejects sea spray into the atmosphere. This process generates marine aerosols that influence cloud formation, radiative forcing, and atmospheric chemistry, with shoreline breaking particularly enhancing aerosol emissions near coastal zones.[13] The resulting sea spray aerosols can travel far inland, impacting regional air quality and weather patterns.[11] From a human perspective, breaking waves are essential to coastal dynamics, where they drive sediment transport through undertows and longshore currents, shaping beach morphology and influencing erosion or accretion patterns over seasonal and storm timescales.[14] They also form the foundation of surfing, providing the predictable, energy-rich curls that define the sport and support coastal tourism economies.[2] Furthermore, the kinetic energy released during breaking is harnessed in wave energy converters, such as shoreline devices that capture hydraulic pressure from crashing waves to generate electricity, offering a renewable resource with potential to power thousands of households.[15] Quantitatively, breaking waves dissipate a substantial portion of the energy transferred from wind to the ocean surface, with global estimates indicating that they account for over 50% of the approximately 57 TW of annual wind energy input to waves, primarily through deep-water breaking processes totaling around 33 TW.[16]Formation
Wave Evolution Leading to Breaking
As ocean waves propagate from deep water toward the shore, they undergo shoaling, a process where decreasing water depth causes the waves to slow down, their wavelength to shorten, and their height to increase in order to conserve energy flux. This transformation begins when the water depth becomes less than half the wavelength (i.e., ), marking the transition from deep-water to intermediate-water conditions where the seabed begins to influence wave motion.[17][18] In typical coastal settings, this leads to a progressive buildup of wave amplitude over distances of several kilometers, with the wave period remaining relatively constant.[19] Once in shallower water, nonlinear effects dominate the wave evolution, causing the wave profile to steepen as the higher-velocity crests advance faster than the troughs due to nonlinear effects, where the phase speed depends on wave amplitude. This asymmetry arises because particle velocities under the crest exceed those under the trough, resulting in a forward-leaning wave front that becomes increasingly unstable.[20] Studies of nonlinear shallow-water waves confirm that this steepening is exacerbated in regions where the Ursell number (a measure of nonlinearity) exceeds unity, promoting higher harmonics and further distortion of the wave shape.[21] External factors such as wind forcing, ocean currents, and bathymetric variations significantly modulate this evolution by amplifying wave instability. Offshore winds can enhance wave growth through momentum transfer, accelerating the onset of steepening, while opposing currents may increase effective wave height by altering relative propagation speeds.[22] Bathymetry, including reefs or sandbars, induces rapid depth changes that intensify shoaling and nonlinear interactions, often leading to localized wave focusing and heightened breaking potential.[23] The overall timeline of wave evolution spans from generation in deep water, where fetch-limited growth under wind action establishes initial wave fields, to nearshore transformation. In deep water (d > L/2), waves propagate linearly with minimal distortion over hundreds of kilometers; upon entering the coastal zone (typically within 5-10 km of shore), shoaling and nonlinearity drive rapid changes over 1-5 km, culminating in conditions ripe for breaking.[24] This progression is observed in field measurements across various coastal environments, highlighting the interplay of these processes in setting the stage for wave collapse.[25]Breaking Criteria
Breaking waves initiate when specific quantitative thresholds in wave parameters relative to water depth are exceeded, marking the transition from stable propagation to instability. A primary steepness criterion, derived from Stokes wave theory, predicts breaking when the ratio of wave height to wavelength surpasses 0.14 in deep water conditions, where the water depth is much greater than half the wavelength.[26] In shallower water, Miche's criterion extends this limit as , where is the wave number and is the water depth; this approximates to in very shallow conditions, indicating depth-induced breaking when the wave height approaches 89% of the local depth.[26] This threshold arises from the condition where orbital velocities at the wave crest equal the phase speed, leading to instability.[26] Depth-limited breaking further constrains the maximum sustainable wave height, with empirical observations confirming at the breakpoint, where is the breaker height and is the local water depth.[27] This limit, originally proposed by McCowan for solitary waves, has been widely adopted for periodic waves in shallow water, providing a practical bound for coastal engineering predictions; slight variations exist, such as 0.75 in some early formulations, but 0.78 aligns with theoretical solitary wave stability analyses.[27] Updated models incorporate nonlinearity via the Ursell number , where indicates the cnoidal wave regime, characterized by strong nonlinearity that enhances wave steepening and increases the potential for breaking in intermediate to shallow depths, transitioning from linear to nonlinear regimes.[28] The seabed slope also modulates breaking thresholds, influencing the dominant breaker type without altering the core steepness or depth limits. On gentler slopes (ratios of 1:50 to 1:100), spilling breakers predominate as waves gradually destabilize, while steeper slopes (>1:10) promote plunging breakers through rapid height growth.[29] This dependence is captured by the surf similarity parameter , where is the slope angle, with favoring spilling and favoring plunging, though detailed type classifications are addressed elsewhere.[29]Types
Spilling Breakers
Spilling breakers are characterized by a progressive dissipation of wave energy, where the crest spills forward gradually over the wave face, generating a foamy, turbulent front as the top portion of the wave moves faster than the underlying water.[30] This type of breaking produces a long, white-water zone along the advancing front, with the instability developing slowly across the crest rather than abruptly.[3] Visually, spilling breakers appear as a gentle crumbling or spilling of the wave top, often extending over a significant distance offshore, and are most commonly observed on beaches with gentle slopes, typically less than 1:50 (or gradients around 0.02 or flatter).[31] These breakers form in intermediate to shallow water depths where wave steepness increases gradually due to shoaling, allowing the instability to spread laterally along the crest length without a sudden collapse.[32] The process begins with the formation of small-scale capillary waves on the leeward side of the wave toe, leading to a bore-like structure that evolves into widespread spilling as the wave height grows proportionally to the decreasing depth.[33] This gradual buildup contrasts with more explosive breaking on steeper slopes, such as plunging breakers, where the curl forms more rapidly. The energy release in spilling breakers is slow and distributed across the surf zone, involving minimal vertical plunge and primarily horizontal spilling that dissipates momentum through turbulence and foam production.[29] This distributed mechanism results in lower peak energy dissipation rates compared to other breaker types, making spilling common in wind-driven seas or long-period swells approaching sandy, dissipative beaches.[34] Examples include prevalent conditions on gently sloping sandy shores during moderate swells, such as those observed on dissipative beaches in regions like Hawaii's north shore under non-extreme wave conditions.[30]Plunging Breakers
Plunging breakers are characterized by the wave crest curling over the front face, forming a distinctive tube or barrel that plunges forward and collapses onto the trough, often entraining air into a cavity beneath the overturning sheet.[35] This dramatic motion creates a forceful cascade of water, producing explosive white foam and sometimes geysers upon impact, making them visually striking and highly sought after in surfing for their tubular rides.[30] These breakers typically form on beaches with moderate bottom slopes, ranging from approximately 1:50 to 1:20, where shoaling causes rapid wave steepening.[36] The overturning occurs when the horizontal particle velocity at the crest exceeds the wave's phase speed, leading to instability and the forward pitching of the crest.[37] Energy dissipation in plunging breakers is intense and localized, primarily through turbulence generated by the impacting jet, which breaks down the organized wave energy into chaotic motion.[38] This process often produces strong undertows as water is drawn back seaward beneath the breaking front, contributing to the formation of rip currents in the surf zone.[39] Prominent examples include the waves at Pipeline Beach (also known as Banzai Pipeline) in Hawaii, where plunging breakers curl over shallow coral reefs during large swells, creating hazardous yet iconic tubes.[40] Similarly, Jeffreys Bay in South Africa features world-class plunging waves on its moderately sloped point breaks during peak southern ocean swells.[41]Collapsing Breakers
Collapsing breakers represent an intermediate form of wave breaking, positioned between plunging and surging types, where the wave crest collapses vertically onto the trough without developing a pronounced forward-curling tube. This results in a shock-like failure of the wave front, producing a sudden vertical surge of water that impacts the underlying wave surface and generates localized turbulence. Unlike spilling breakers, which dissipate energy gradually with significant foam production, collapsing breakers exhibit less aeration but a more abrupt collapse than surging waves, often manifesting as a near-vertical drop of the crest mass.[31][30] These breakers typically form on moderately steep beach slopes ranging from 1:20 to 1:10, where increasing wave steepness and bottom friction lead to instability in the wave front, causing it to topple downward rather than curl or spill progressively. This transitional regime arises in environments where the surf similarity parameter indicates intermediate conditions, bridging the dynamics of gentler spilling and steeper plunging waves. The relation to beach slope aligns with established breaking criteria, influencing the precise location and intensity of the collapse.[42][43] The energy release during a collapsing breaker involves moderate turbulence generated by the falling crest, which entrains air and creates a hydraulic jump-like structure that rapidly dissipates kinetic energy into heat and mixing. This process is common in transitional beach profiles, where the interplay of wave height and bottom topography promotes such vertical collapses over gradual dissipation. Observations of collapsing breakers are prevalent on gravel or mixed-sand beaches, which often feature these intermediate slopes and variable sediment mobility.[44][45][46]Surging Breakers
Surging breakers occur when waves approach the shoreline and surge forward as a nearly intact bore, with the wave front steepening but without developing significant crest instability or overturning. The wave runs up the beach rapidly, often forming a wall of water that withdraws seaward without forming a turbulent whitewater curl or jet. This type is visually distinct, appearing as a smooth, rushing advance and retreat rather than a chaotic break, and is most common on very steep beach slopes greater than 1:10, where the seabed slope β exceeds 0.1.[47][48] These breakers form in reflective coastal environments with very shallow water depths near the shore, allowing the wave base to advance quickly and the crest to remain stable enough for reformation on the backwash. They typically develop from long-period swells incident on steep foreshores, where the surf similarity parameter ξ > 2, indicating a dominance of beach slope over wave steepness that prevents full energy release through turbulence. Minimal energy loss occurs per wave cycle, as the wave does not fully dissipate upon reaching the shore but instead reflects a significant portion of its energy seaward.[47][49] Energy dissipation in surging breakers is low compared to other types, primarily occurring through bottom friction during the swash and backwash on the beach face, which allows the wave form to be preserved longer across multiple cycles. Unlike more dissipative breakers such as spilling or plunging, surging waves maintain much of their structure, leading to high reflection coefficients that can exceed 0.8 in these conditions.[49][50] Surging breakers are typical on rocky or steep shingle beaches during calm to moderate conditions, such as the rocky shores of Westcombe Beach in South Devon, UK, or the steep, boulder-strewn coasts of New England like those around Acadia National Park in Maine.[34]Physics
Hydrodynamics of the Breaking Process
The hydrodynamics of the breaking process in surface waves involves complex fluid instabilities that transition from nearly irrotational flow to highly rotational and turbulent regimes. At the onset of breaking, flow instability manifests as the generation of vorticity and shear layers at the wave crest, primarily due to the nonlinear steepening of the wave profile. This leads to wave overturning, where the crest curls forward as the fluid particles at the surface begin to move faster than the underlying wave propagation. In inviscid models based on the Euler equations, breaking initiates when the horizontal fluid particle velocity at the crest exceeds the wave phase speed, marking the kinematic criterion for instability.[51][52] A related dynamic criterion, proposed by Phillips (1985), states that breaking occurs when the downward acceleration of fluid particles at the crest exceeds gravitational acceleration.[53] As breaking progresses, turbulence generation becomes dominant, characterized by the formation of a turbulent breaking bore and the development of a surface roller. In plunging breakers, the overturning crest forms a forward-propagating jet that impinges on the preceding water surface, creating intense shear and vorticity concentrations. Velocity fields in this region exhibit peak speeds in the jet reaching up to 2-3 times the phase speed, driving rapid mixing and energy transfer to smaller scales. The roller dynamics involve organized vortical structures that evolve into broadband turbulence, with coherent eddies contributing to the overall flow reversal beneath the crest.[54][52][55] Air entrainment accompanies this turbulent breaking, injecting bubbles into the water column and forming a foamy whitecap with significant void fractions up to 50% near the surface. Bubbles are primarily entrained at the jet impact in plunging breakers or along the spilling toe in milder breaks, leading to a subsurface plume. Models such as Thorpe's scale describe the bubble size distribution, where the mean radius of entrained bubbles typically ranges from 1-2 mm, influencing gas exchange and dissipation rates, with larger bubbles rising quickly and smaller ones persisting deeper due to turbulence.[56][57][58] Laboratory flume experiments, often employing particle image velocimetry (PIV) for detailed velocity mapping, highlight three-dimensional instabilities during breaking that are underrepresented in two-dimensional theories. These studies reveal oblique wave crests and spanwise variations in the roller, leading to asymmetric vorticity distribution and enhanced turbulence not fully captured by depth-integrated or planar models. In contrast, field observations indicate greater variability due to wind and bathymetry effects, but confirm the core mechanisms observed in controlled settings.[59][60][61]Energy Dissipation and Wave Transformation
When a wave breaks, a significant portion of its energy is dissipated through turbulence and mixing in the upper ocean layers. The dissipation rate ε_b for breaking waves is approximated by the formula where ρ is the water density, g is gravitational acceleration, f is the wave frequency, B is an empirical coefficient (typically around 1), and p_b(H) is the probability density function of breaking wave heights. This parameterization, derived from empirical models of surf zone energetics, captures the average rate of energy loss per unit area during the breaking process. For monochromatic waves, it simplifies to a form proportional to ρ g H^3 f / (16 π).[62] Following the initial break, the wave transforms into a turbulent bore that propagates shoreward, with the bore height typically reducing by 20-50% over one wavelength due to ongoing frictional and turbulent dissipation within the surf zone. This decay is more pronounced on steeper slopes, where plunging breakers lead to faster energy loss, compared to spilling breakers on gentler slopes that exhibit gradual height reduction. The resulting bore maintains a sawtooth profile, contributing to further energy transformation as it interacts with the bottom boundary layer.[29] Wave breaking also alters the frequency spectrum of the wave field by preferentially dissipating energy at high frequencies, where steeper wave components are more susceptible to instability and breakage. This selective removal leads to a broadening of the overall spectrum, reducing peakiness and limiting the development of swell in fetch-limited conditions, such as near coastal generation areas. In contrast, lower-frequency energy persists longer, influencing long-range propagation patterns.[63] Estimates of global breaking wave dissipation are obtained through in-situ measurements with wave buoys, which capture local turbulence and height decay, and satellite altimetry, which provides broad-scale observations of significant wave height and breaking probability. These techniques yield an average global dissipation rate of approximately 68 TW, representing a key sink in the ocean energy budget and highlighting the role of breaking in modulating air-sea interactions.[64]Impacts and Applications
Environmental Effects
Breaking waves play a pivotal role in coastal erosion by mobilizing and transporting sediment along shorelines through longshore currents generated in the surf zone. Globally, these processes redistribute an estimated 10 to 20 billion tonnes of clastic sediment annually from continental sources to coastal systems, with breaking waves responsible for the majority of littoral transport.[65] Plunging breakers, in particular, exert concentrated hydraulic forces on cliff bases, accelerating retreat rates in soft-rock coasts to 0.01–1 m per year by undercutting and removing talus debris.[66] This erosion contributes to habitat loss and infrastructure threats, as seen in regions with intermediate beach profiles where plunging waves dominate.[67] The turbulence from breaking waves profoundly affects intertidal habitats, disrupting communities of algae and invertebrates while simultaneously enhancing environmental conditions in some ways. High-energy breakers scour the substrate, dislodging sessile organisms like mussels and snails, which significantly disrupts populations in exposed zones during storms.[68] Conversely, wave-induced mixing enhances nutrient uptake by macroalgae through reduction of the diffusive boundary layer around fronds, improving competitive advantages for productive species in the low intertidal.[69] These dual effects lead to zonation patterns, with resilient, wave-adapted communities dominating areas of frequent breaking, while scour limits diversity in fragile assemblages.[70] During hurricanes, breaking waves amplify storm surges by contributing wave setup and runup, elevating water levels by 0.6–1.2 m through radiation stress gradients in the nearshore.[71] In Hurricane Katrina (2005), this wave-breaking contribution was significant, adding to the overall surge that reached over 8 m in parts of the Mississippi coast and exacerbating inland flooding across 230 km of shoreline.[72] Such amplification transforms moderate surges into catastrophic events, with onshore momentum from plunging and collapsing breakers pushing water farther inland.[73] Over long timescales, breaking wave types influence beach morphology and coastal evolution. Spilling breakers on dissipative beaches, characterized by gentle slopes, promote gradual sediment deposition in the swash zone, building berms that act as natural buffers against erosion.[74] In contrast, surging breakers on reflective beaches maintain steep profiles by reflecting wave energy with minimal dissipation, preserving linear foreshores and cusps through high runup and limited offshore transport.[75] These dynamics sustain equilibrium forms, with spilling enhancing accretion on wide, low-gradient shores and surging reinforcing narrow, coarse-sediment fronts.[76]Human Uses and Engineering
Breaking waves play a central role in human recreation, particularly surfing, where plunging breakers are prized for their formation of tubular sections that allow riders to experience the "barrel" or tube ride. These breakers, characterized by a curling crest that plunges forward, provide the dynamic conditions ideal for advanced maneuvers, contrasting with gentler spilling breakers suited to beginners.[77] Surfing originated as a cultural practice among Polynesians, with the activity deeply embedded in Hawaiian society as he'e nalu (wave sliding) and first documented by European explorers in the late 1700s during Captain James Cook's voyages.[78] By the 20th century, surfing evolved into a global sport, with modern competitions like those organized by the World Surf League (WSL) held at venues renowned for specific breaker characteristics, such as Pipeline in Hawaii for plunging waves.[79] The global surfing industry, encompassing tourism, equipment, and events, supports an economic value exceeding $68 billion in surfing tourism alone as of 2025, driving coastal economies through lessons, apparel, and travel.[80] Safety in surfing relies on forecasting breaker types, with lifeguards using environmental assessments—including wave steepness and beach slope—to predict hazardous conditions like plunging breakers that increase rip current risks and spinal injuries.[81][82] In renewable energy applications, breaking waves offer a harnessable resource through technologies like oscillating water columns (OWCs), which capture the pneumatic energy from wave-induced air compression in a chamber. These devices convert the oscillatory motion near the breaker zone into electricity via turbines, with prototypes demonstrating viability in nearshore environments. For instance, the Oceanlinx greenWAVE OWC prototype, deployed off Australia, was rated at 1 MW but achieved peak outputs around 321 kW under optimal conditions, highlighting the potential for scaling to contribute to coastal power grids.[83][84] OWCs are particularly effective in locations with consistent spilling or plunging breakers, as the breaking process amplifies air flow, though challenges like biofouling and storm survivability persist in commercial deployment.[85] Coastal engineering leverages breaking waves for protection by designing structures that promote energy-dissipating breaker types, such as breakwaters and groins, to mitigate erosion and flooding. Breakwaters, often constructed as rubble-mound or submerged barriers, induce spilling-like dissipation by reducing wave height and steepness, significantly dissipating incoming energy before it reaches the shore.[86][87] Groins, perpendicular to the shoreline, trap sediment and alter wave patterns to favor spilling breakers on adjacent beaches, stabilizing coastlines in areas prone to longshore drift. Numerical models like SWAN (Simulating WAves Nearshore) are essential for predicting breaker locations and types, simulating wave propagation, shoaling, and breaking to optimize structure placement and performance.[88][89] These interventions balance protection with environmental considerations, ensuring long-term resilience against sea-level rise and intensified storms.References
- https://www.coastalwiki.org/wiki/Wave_breaking
- https://www.coastalwiki.org/wiki/Breaker_index
- https://www.coastalwiki.org/wiki/Gravel_Beaches
- https://www.coastalwiki.org/wiki/Surf_similarity_parameter
- https://www.coastalwiki.org/wiki/Shoreface_profile
- https://www.coastalwiki.org/wiki/Modelling_coastal_hydrodynamics