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Seiche

A seiche is a standing wave in an enclosed or partially enclosed body of water, such as a lake, bay, or harbor, where the water oscillates rhythmically with large vertical displacements at the ends of the basin and minimal movement at the central node.^[1] These oscillations arise from the interference of waves traveling in opposite directions, resulting in periodic rises and falls of water levels that can persist for minutes to hours or even days, depending on the basin's dimensions and the forcing mechanism.^[2] Seiches are primarily triggered by external forces that displace water from its equilibrium, including strong winds and rapid changes in atmospheric pressure that push water toward one end of the basin, followed by sloshing upon cessation of the force.^[1] Seismic activity from distant earthquakes can also generate seiches through the passage of surface waves, creating standing oscillations in inland water bodies without direct tectonic displacement of the seafloor.^[3] Other triggers include tsunamis, storm surges, or atmospheric gravity waves, with the resonant frequency of the seiche determined by the basin's length, depth, and geometry—typically following a period of approximately twice the time for a wave to traverse the basin length.^[2] Notable examples illustrate the potential hazards of seiches; in 1844, a wind-driven seiche on Lake Erie produced waves up to 7 meters (22 feet) high, resulting in 78 fatalities from flooding and structural damage.^[1] Seismic seiches from the 1964 Alaska earthquake (magnitude 9.2) were recorded across North America and as far as Australia, with amplitudes reaching 1.8 meters in U.S. Gulf Coast reservoirs and lakes.^[3] In coastal settings, harbor seiches like Japan's abiki or Spain's rissaga can amplify to over 3 meters due to resonance, posing risks to navigation and infrastructure through strong currents and sudden water level changes.^[2] While often benign, seiches differ from tsunamis by their confinement to enclosed basins and longer periods (typically over 3 hours in large lakes), though they can mimic tidal effects in the Great Lakes with cycles of 4–7 hours.^[1]

Fundamentals

Definition

A seiche is a standing wave in an enclosed or partially enclosed body of water, where the water level oscillates rhythmically between the basin's ends, with nodes of minimal motion typically occurring in the middle.^[1]^[4] This oscillation arises from the water's displacement and subsequent return toward equilibrium, forming a resonant pattern akin to the sloshing of liquid in a container.^[5] The phenomenon is characterized by its stationary nature, with the wave energy trapped within the basin rather than propagating outward.^[6] The term "seiche" was first scientifically established by Swiss hydrologist François-Alphonse Forel in 1890, based on his pioneering observations of the effect in Lake Geneva, Switzerland.^[7]^[8] Forel's work formalized the description of these oscillations, distinguishing them as a distinct hydrodynamic process.^[9] Seiches differ fundamentally from tides, which are global-scale, astronomically driven fluctuations with periods typically ranging from hours to days, whereas seiches have shorter, basin-specific periods often lasting minutes to hours and remain confined to local water bodies.^[10] They also contrast with tsunamis, which are far-traveling, progressive waves generated by massive oceanic displacements and capable of crossing entire ocean basins, unlike the localized, non-propagating standing waves of seiches.^[3] Gravity serves as the primary restoring force, pulling the displaced water surface back toward its equilibrium level to sustain the oscillation.^[11]

Physical Characteristics

Seiches exhibit a characteristic sloshing motion in enclosed or semi-enclosed basins, resembling the vibration of a taut string, where water levels oscillate back and forth across the basin. In the fundamental mode, this standing wave pattern features antinodes—points of maximum vertical displacement—at the basin's ends and a central node where the water surface remains stationary.^[12] Higher harmonic modes introduce additional nodes and antinodes within the basin, allowing for more complex oscillation patterns, such as quarter-wavelength distributions in harbors.^[2] The periods of seiches span a wide range, typically from a few minutes in small harbors to several hours in large lakes, governed by the basin's length, width, and depth.^[2] For instance, periods of around 18.6 minutes occur in Malokurilsk Bay, while larger systems like Lake Geneva exhibit oscillations lasting about 74 minutes (uninodal mode).^[12]^[13] Amplitudes generally vary from centimeters in calm conditions to several meters during strong events, with rare extremes surpassing 3 meters, as observed in Nagasaki Bay.^[2] Over time, seiches experience damping primarily through bottom friction in closed basins and energy radiation via the entrance in harbors, leading to gradual amplitude decay after the initial excitation.^[12] However, when resonantly driven by persistent external forces, such as atmospheric pressure waves, these oscillations can maintain significant amplitudes for hours or even days.^[2]

Causes and Generation

Meteorological Triggers

Meteorological triggers represent the primary natural initiators of seiches, driven by atmospheric forces that displace water in enclosed or semi-enclosed basins, leading to oscillatory responses. These phenomena arise from interactions between weather systems and water bodies, where sustained or abrupt atmospheric disturbances generate initial water level anomalies that evolve into standing waves. Unlike geological triggers, meteorological causes are frequent and widespread, occurring in lakes, harbors, and coastal areas globally.^[1] Strong winds are a dominant meteorological trigger, exerting direct shear stress on the water surface to pile up water against one end of a basin. When the wind abruptly ceases or reverses—often due to passing storm fronts—the displaced water mass sloshes back, initiating oscillations that can persist for hours or days. For instance, prevailing winds from a consistent direction build water levels gradually, with cessation allowing the potential energy to convert into wave motion, as observed in coastal simulations where wind speeds of around 4-5 m/s align with diurnal cycles to excite basin modes. This mechanism is particularly effective in elongated basins like lakes or bays, where wind alignment with the principal axis amplifies the effect.^[1]^[14]^[15] Rapid changes in atmospheric pressure, such as those from squall lines, thunderstorms, or the passage of low- or high-pressure systems, create horizontal pressure gradients that force water level displacements via the inverse barometer effect. These gradients induce immediate sea surface anomalies, with pressure drops of 2-5 hPa over minutes to hours sufficient to generate initial surges that resonate within the basin. Storm passages, for example, produce semidiurnal pressure variations that correlate with seiche amplitudes, enhancing oscillations through direct forcing.^[1]^[14]^[15] Meteotsunamis, a subset of meteorological disturbances, occur when atmospheric gravity waves—propagated by convective cells or fronts—transfer energy to the ocean, generating propagating waves that excite seiche-like oscillations upon reaching resonant basins. These waves, with periods of 10-200 minutes and speeds matching long ocean waves (via Proudman resonance), amplify through shelf and harbor resonances, producing seiche amplitudes up to several meters. Such events link atmospheric convection directly to basin-scale standing waves, distinct from wind or pressure alone. Basin geometry can briefly amplify these resonances, matching disturbance periods to natural modes for sustained energy input.^[16]^[17]^[18]

Seismic and Tsunamic Triggers

Seismic seiches occur when earthquake-generated waves propagate through enclosed or semi-enclosed bodies of water, such as lakes, reservoirs, bays, or harbors, causing abrupt vertical and horizontal displacements that initiate standing wave oscillations. These motions arise primarily from the passage of seismic surface waves, which tilt or slosh the water column, exciting resonant modes if the wave periods align with the basin's natural frequencies. Unlike gradual meteorological forcings, seismic triggers produce immediate, high-amplitude responses that can last from minutes to hours, depending on damping factors like friction and basin geometry.^[3]^[4]^[19] A notable example is the 2011 Tohoku earthquake in Japan, which generated seismic waves that traveled across the globe and triggered seiches in western Norwegian fjords, with oscillations beginning approximately 30 minutes after the event and persisting for several hours at trough-to-peak amplitudes of 1.0–1.5 m. Such distant triggering demonstrates the efficiency of long-period Rayleigh waves in exciting seiches far from the epicenter, as observed in multiple basins worldwide during major seismic events.^[19]^[3] Tsunamis can also excite resonant seiches upon entering semi-enclosed areas like bays or fjords, where the incoming long-period waves interact with the basin's boundaries to amplify standing oscillations. This resonance occurs when the tsunami's dominant period matches the natural seiche period of the enclosure, leading to prolonged water level fluctuations that extend the hazard duration beyond the initial wave arrival. In coastal engineering assessments, these combined effects are critical for evaluating risks in harbors, as the seiche can sustain flooding or structural stresses even after the tsunami's primary energy dissipates.^[20]^[21] For instance, modeling of tsunami propagation into the Marquesas Islands' semi-enclosed lagoons has shown how incident waves with periods around 10-20 minutes can sustain seiches for hours, with amplification factors exceeding 2-3 times the incoming amplitude due to Helmholtz resonance modes.^[21] Landslides and iceberg calving in fjords represent another key non-meteorological trigger, where rapid mass displacements generate impulse-like surges that evolve into sustained seiches as the water oscillates against the confining topography. These events often link to climate-driven processes, such as glacial retreat destabilizing slopes, producing initial tsunamigenic waves that resonate within the narrow basin. In such cases, the seiche can persist for days, with low-frequency modes dominating due to the elongated fjord geometry.^[22]^[23] A prominent recent example is the 2023 rockslide in East Greenland's Dickson Fjord, triggered by climate-induced melting of a mountaintop glacier, which collapsed and generated a mega-tsunami with run-up heights over 200 meters; the ensuing seiche oscillated for nine days, producing detectable global seismic signals from the water's repetitive sloshing. Similarly, iceberg calving events in Greenland fjords have been observed to excite seiches detectable via seismometers, as the sudden buoyancy changes induce fjord-wide tilting and wave modes.^[22]^[24]^[23] While wind-driven setups are generally the most common seiche initiators, seismic and tsunamic triggers stand out for their capacity to generate abrupt, high-energy oscillations with minimal warning.^[3]

Mathematical Modeling

Resonance and Period Calculations

Resonance in seiches occurs when the period of an external driving force aligns with the natural oscillation period of the water body, resulting in amplified standing wave amplitudes that can significantly exceed those of non-resonant conditions.^[25] This amplification arises because the basin acts as a resonator, where constructive interference builds energy over multiple wave cycles.^[25] Such resonance is particularly relevant in enclosed or semi-enclosed basins, where meteorological or seismic forcing can excite these natural modes.^[26] The natural periods of seiches are estimated using Merian's formula, derived from the shallow-water wave approximation for a closed rectangular basin of length L and uniform depth h.^[26] For the fundamental mode (first harmonic), the period T is given by

T = \frac{2L}{\sqrt{gh}},

where g is the acceleration due to gravity (approximately 9.81 m/s²).^[26] This formula represents the time for a gravity wave to travel the basin length twice, reflecting off both ends to form a standing wave with antinodes at the boundaries and a node in the center.^[26] Higher-order modes involve additional nodes within the basin, leading to shorter periods. For these modes in rectangular basins, the period T_n is

T_n = \frac{2L}{n \sqrt{gh}},

where n = 1, 2, 3, \dots .^[26] Odd modes (n = 1, 3, 5, ...) are antisymmetric about the basin center, while even modes (n = 2, 4, ...) are symmetric; uniform forcing such as steady wind typically excites odd modes preferentially. The fundamental (n=1) has the longest period and progressively higher modes feature more internal nodes and faster decay due to friction.^[25] Resonance at these higher periods requires forcing frequencies that match accordingly, though the fundamental mode often dominates in practice due to lower damping.^[26]

Wave Dynamics Equations

The dynamics of seiches in a closed basin of uniform depth h and length L are described by the linearized one-dimensional shallow water wave equation for the free surface elevation \eta(x, t):

\frac{\partial^2 \eta}{\partial t^2} = g h \frac{\partial^2 \eta}{\partial x^2},

where g is the acceleration due to gravity.^[27] This equation arises from the linearized shallow water equations, combining continuity and momentum balance under the assumptions of small-amplitude waves, hydrostatic pressure, and negligible friction.^[27]^[12] For a closed basin, the boundary conditions require zero horizontal velocity at the ends: u(0, t) = 0 and u(L, t) = 0 for all t, which implies \partial \eta / \partial x = 0 at x=0 and x=L.^[12] These conditions yield standing wave solutions obtained via separation of variables, giving normal modes of the form \eta_n(x, t) = \cos\left(\frac{n \pi x}{L}\right) \cos(\omega_n t + \phi_n), where n = 1, 2, \dots is the mode number, \omega_n = \frac{n \pi}{L} \sqrt{g h} is the angular frequency, and \phi_n is a phase. The general solution is a linear superposition of these modes:

\eta(x, t) = \sum_{n=1}^{\infty} A_n \cos(\omega_n t + \phi_n) \cos\left(\frac{n \pi x}{L}\right),

with coefficients A_n and \phi_n determined by initial conditions.^[12] In basins with variable depth, the wave equation incorporates a depth-dependent coefficient, complicating analytical solutions and often necessitating numerical methods or approximations, such as those expanding the elevation in series of orthogonal functions. For large basins where the Rossby radius of deformation is comparable to the basin scale, the Coriolis force modifies the dynamics, transforming longitudinal seiches into rotating Kelvin waves that propagate along the boundaries in the direction of planetary rotation, with amplitudes decaying exponentially away from the coast.^[28]

Occurrences by Environment

In Lakes and Reservoirs

Seiches are particularly prevalent in the Great Lakes, where the enclosed nature of these large freshwater bodies facilitates standing wave oscillations. Lake Erie, the shallowest and most elongated of the Great Lakes, experiences frequent seiches due to its east-west orientation and susceptibility to persistent winds. The fundamental seiche mode in Lake Erie has a period of approximately 14 hours, corresponding to the basin's length of about 388 km and average depth of 19 m, while higher-order modes can have periods around 6 to 9 hours. Amplitudes typically range from a few centimeters to 1-2 m during moderate events, though extreme cases have reached up to 4-5 m, leading to significant water level fluctuations at opposite shores.^[29]^[30]^[31]^[32] In reservoirs, seiches often arise from wind-driven setups or operational activities such as rapid changes in flow through dams or gates, which can destabilize the water surface and initiate oscillations. These man-made basins, generally smaller than natural lakes, exhibit shorter seiche periods—typically ranging from minutes to a few hours—due to their reduced dimensions and depths. For instance, in reservoirs with adjustable dams, sudden releases or inflows can generate flow-induced seiches with periods on the order of 10-30 minutes, amplifying risks to dam stability if not managed. Wind remains a primary trigger, piling water against the upstream face and causing resonant rocking.^[33]^[34]^[26] Recent observations indicate an increasing frequency of seiche events in Lake Erie, attributed to more intense wind storms and thunderstorms linked to broader climate patterns, including warmer atmospheric conditions that enhance storm development. Studies suggest that climate-driven changes, such as reduced ice cover and stronger westerly winds, have contributed to a rise in extreme seiche occurrences, with events now happening roughly every 1-2 years compared to less frequent historical records. This trend underscores the vulnerability of enclosed freshwater systems to meteorological shifts.^[35]^[36]^[37]

In Seas, Bays, and Harbors

Seiches in seas, bays, and harbors occur in saline coastal environments where open-ocean influences, including tides, play a significant role in their generation and amplification. Unlike enclosed freshwater bodies, these coastal seiches often resonate with incoming tidal waves, leading to prolonged oscillations that can synchronize with semi-diurnal tidal cycles of approximately 12 hours. This tidal coupling enhances the persistence and intensity of seiches, particularly in elongated basins where the geometry favors standing wave formation.^[38] In the Adriatic Sea, bay seiches exhibit periods that align closely with semi-diurnal tides, resulting in resonant amplification of sea-level variations. Observational data from multiple stations indicate high quality factors (Q-factors) for these tides, confirming their resonant nature and potential to sustain seiches over extended durations. Similarly, in the Baltic Sea, seiches in coastal bays interact with tidal forcing, though diurnal components predominate; local resonances in sub-basins can still couple with semi-diurnal periods around 12 hours, contributing to oscillatory sea-level changes. These bay-scale seiches are driven by atmospheric pressure gradients or wind setups that match the basin's natural frequencies.^[38] Harbor resonances represent a specialized form of seiche in confined coastal inlets, where incoming long waves excite the harbor's eigenmodes, often leading to dramatic amplifications. A notable example is the 1979 "abiki" event in Nagasaki Bay, Japan, triggered by a meteotsunami from an atmospheric pressure disturbance; water levels reached amplitudes of 2.78 meters at Matsugae quay, with periods of 30 to 40 minutes, causing three fatalities and significant damage to port infrastructure. Such harbor seiches highlight the vulnerability of narrow entrances to external wave forcing.^[39] Seiches in these environments frequently interact with storm surges, where the surge acts as an initial impulse that excites resonant oscillations, thereby amplifying coastal flooding beyond the surge's direct effects. This superposition can prolong high-water events, exacerbating inundation in low-lying areas and complicating flood forecasting. In deeper seas, brief interactions with internal layers may modulate surface seiches, though surface dynamics dominate in most bay and harbor cases.

Internal and Underwater Seiches

Internal and underwater seiches, distinct from surface oscillations, manifest as standing waves along density interfaces within stratified water bodies, primarily at the thermocline—where temperature gradients create density differences—or the pycnocline, where salinity variations dominate.^[40] These phenomena arise in thermally or haloclinically stratified lakes and seas due to wind-driven momentum that displaces the interface, leading to oscillatory motions sustained by the basin's geometry.^[41] Unlike surface seiches, internal modes exhibit longer periods, often several hours to days, because the effective gravitational acceleration is reduced by the density contrast across the interface, resulting in slower wave propagation speeds.^[40] Detection of these subsurface oscillations typically relies on high-resolution temperature sensors, such as thermistor chains, which capture periodic fluctuations in isotherm depths and confirm the presence of internal wave activity.^[42] In field studies, these instruments reveal seiche amplitudes of several meters at the thermocline, persisting for days after wind events.^[43] Internal seiches significantly influence vertical mixing by generating shear at density boundaries, which promotes diapycnal transport and erodes stratification without fully disrupting it.^[44] This process enhances the upward flux of nutrients from hypolimnetic or deeper layers, supporting epilimnetic primary production and altering biogeochemical cycles in both lakes and marginal seas.^[45] For instance, in large stratified lakes, seiche-induced boundary mixing can supply phosphorus and other limiting nutrients to surface waters, boosting algal blooms and overall productivity.^[44] In the Great Lakes, internal seiches affect ecological dynamics, including fish behavior; in Hamilton Harbour of Lake Ontario, approximately 100 such events over three months correlated with walleye (Sander vitreus) vertical migrations, as fish adjusted depths to avoid hypoxic zones below the oxycline shifted by thermocline oscillations.^[41] This forced displacement influences foraging and spawning patterns, potentially impacting population distributions in oxygen-limited environments.^[41] Similarly, in semi-enclosed seas like Gullmar Fjord, internal seiches drive basin-wide mixing, facilitating nutrient redistribution across pycnoclines and sustaining plankton communities.^[46]

In Caves and Confined Spaces

Seiches in caves and highly confined spaces occur as standing waves in enclosed water bodies, often triggered by distant seismic activity that propagates pressure waves through the ground, causing the water surface to oscillate. These events are outliers compared to open-water seiches, as the limited volume and geometry amplify responses to subtle disturbances while restricting energy dissipation.^[3] A well-documented case is the 2022 seiche in Devils Hole, a geothermal pool within a limestone cavern in Nevada's Amargosa Desert, part of a karst aquifer system. On September 19, 2022, a magnitude 7.6 earthquake centered in Michoacán, Mexico—over 2,400 kilometers away—induced waves reaching amplitudes of approximately 1.2 meters (4 feet) in the pool, beginning just five minutes after the initial rupture. The disturbance, captured by remote video surveillance installed by the National Park Service, stirred bottom sediments and dislodged algae from the walls, temporarily altering the habitat for the endangered Devils Hole pupfish without causing fatalities. This observation underscores the heightened sensitivity of such isolated karst features to teleseismic waves.^[47] In broader karst systems, confined underground reservoirs can exhibit similar resonant oscillations when seismic or barometric pressure changes force water levels to fluctuate, mimicking seiche dynamics in the narrow conduits and chambers. Flooded underground mines, with their water-filled shafts and tunnels forming enclosed pools, likewise support these resonances, as seismic surface waves induce sloshing comparable to that in small ponds or reservoirs.^[3] Detecting and quantifying seiches in these environments is complicated by their inaccessibility, necessitating reliance on pre-deployed instruments such as submersible pressure gauges, hydrophones, or cameras, which must withstand harsh conditions without direct human intervention. Remote monitoring in Devils Hole, for instance, relies on fixed surveillance to capture transient events that would otherwise go unobserved.^[47]

Historical and Notable Events

Early Scientific Observations

The phenomenon of seiches, standing waves in enclosed bodies of water, was noted in various European lakes during the 19th century, with reports describing rhythmic oscillations that could reach destructive amplitudes. One of the earliest and most devastating examples occurred on October 18, 1844, in Lake Erie near Buffalo, New York, where strong winds generated a seiche with a height of approximately 22 feet (6.7 meters), breaching a 14-foot seawall and flooding the harbor area, resulting in the deaths of 78 people and the destruction of numerous ships, homes, and wharves.^[1] Such events highlighted the potential hazards of these oscillations, though they were initially attributed to sudden storms rather than resonant wave dynamics. Systematic scientific study began with the work of Swiss hydrologist François-Alphonse Forel, who conducted the first detailed observations of seiches in Lake Geneva (Lac Léman) starting in 1869 and published his initial report in 1873.^[48] Forel's extensive measurements over subsequent years, documented in his monumental three-volume monograph Le Léman (1892–1904), established the oscillatory nature of these waves and their dependence on basin geometry.^[48] In 1890, Forel formally adopted and promoted the local Swiss-French term "seiche" to describe the phenomenon, drawing from earlier anecdotal accounts in the region dating back to the 18th century.^[48] In the early 20th century, Scottish mathematician George Chrystal advanced the understanding of seiches through precise measurements during the Scottish Lake Survey (1906–1908), focusing on lakes such as Loch Earn and Loch Voil. His barometric and limnographic recordings confirmed periodicities ranging from minutes to hours, correlating them with basin lengths and depths via hydrodynamical theory, thus providing empirical validation for resonant modes in elongated European lakes. These efforts laid the groundwork for later mathematical models, though modern extensions have refined the calculations for irregular geometries.

Modern and Extreme Examples

One notable modern seiche event occurred in Nagasaki Bay, Japan, on March 31, 1979, where atmospheric pressure disturbances from a passing cold front generated intense oscillations known as the Abiki phenomenon. The seiche reached a maximum wave height of approximately 5 meters, with water-level displacements up to 2.78 meters recorded at tide stations, persisting for several hours and resulting in three fatalities due to sudden flooding in coastal areas.^[49] This event highlighted the vulnerability of narrow bays to resonant atmospheric forcing, amplifying wave amplitudes through harbor resonance. In September 2023, a massive rockslide in Dickson Fjord, East Greenland, triggered a megatsunami that evolved into a prolonged seiche, demonstrating the global detectability of such oscillations. On September 16, a 25 million cubic meter rock-ice avalanche plunged into the fjord from a height of 1,200 meters, generating initial tsunami waves with run-ups exceeding 200 meters on nearby slopes and propagating up to 72 kilometers away. The subsequent seiche stabilized at an amplitude of 7.4 meters with a period of about 87 seconds, decaying slowly over more than nine days and producing a persistent very-long-period seismic signal at 10.88 millihertz that was recorded worldwide by seismic networks.^[22] This landslide-induced seiche underscored how geological triggers can sustain basin-wide resonances in remote Arctic environments, with vibrations ringing Earth's surface for an extended duration. A hybrid meteotsunami-seiche event affected Lake Superior on June 21, 2025, driven by a powerful low-pressure storm system that traversed the Great Lakes region. The storm induced rapid water level fluctuations, with a meteotsunami causing an initial surge followed by a seiche that altered levels by nearly 4 feet (1.2 meters) over 2.5 hours at monitoring stations like Point Iroquois in Whitefish Bay; oscillations persisted for several days. These changes disrupted maritime operations, forcing numerous cargo ships to remain offshore to prevent groundings in shallow harbors such as Duluth, where level swings reached 1.5 feet and complicated docking maneuvers.^[50] This incident illustrated the compounding effects of atmospheric pressure gradients and wind setup in large freshwater bodies, leading to practical challenges for regional shipping.

Impacts

Environmental and Ecological Effects

Seiches play a significant role in enhancing vertical mixing within lakes, promoting the upwelling of nutrient-rich hypolimnetic waters to the surface layer. This process supplies essential nutrients such as phosphorus and nitrogen to the epilimnion, particularly in nearshore areas where seiche-induced turbulence is most intense. As a result, primary productivity increases, leading to higher phytoplankton biomass and supporting greater plankton populations.^[51] In stratified lakes, this nutrient flux can stimulate algal growth and alter food web dynamics, benefiting herbivorous zooplankton but potentially exacerbating eutrophic conditions.^[52] The ecological impacts extend to fish communities, where seiche-driven upwelling can introduce hypoxic or anoxic waters from deeper layers into shallower habitats. In Lake Kinneret (Sea of Galilee), wind-forced internal seiches have caused upwelling of oxygen-depleted hypolimnetic water, resulting in mass fish mortalities when dissolved oxygen levels drop below 2 mg/L, particularly affecting sensitive species like Mirogrex terraesanctae near the western shore.^[53] Internal seiches, oscillating along thermoclines, further influence fish vertical migrations by disrupting thermal gradients and forcing behavioral adjustments to avoid low-oxygen zones. Seiches also contribute to shoreline erosion and sediment redistribution, reshaping lake bathymetry and benthic habitats. In eastern Lake Erie, seiche oscillations increase bottom shear stress in the surf zone, enhancing offshore transport of suspended sediments and leading to net beach erosion volumes of approximately 760 m³ over extended periods along affected shorelines.^[54] This redistribution can smother benthic organisms and alter substrate composition, impacting invertebrate communities and the base of aquatic food chains.^[55] Climate change amplifies these effects by intensifying storm activity and reducing ice cover, which increases the frequency and magnitude of seiches in large lakes. In the Great Lakes, projected rises in storm intensity are expected to heighten seiche occurrences, potentially worsening nutrient cycling and hypoxic risks. For instance, in Lake Erie, more frequent seiches could enhance vertical mixing of phosphorus-laden sediments, prolonging bottom hypoxia episodes and threatening fish populations in the central basin.^[56]^[57]^[58]

Human, Economic, and Infrastructural Consequences

Seiches pose significant risks to human populations through sudden flooding in coastal and lakeside communities, often leading to property damage and threats to life. In the northern Adriatic Sea, seiche oscillations contribute substantially to extreme sea levels, exacerbating flooding in Venice where they form a key part of the dynamics, with contributions up to 49% of total extreme heights observed at stations like Rovinj during major events.^[59] The 1966 Venice flood, amplified by seiche dynamics, reached 194 cm and inundated much of the city for 22 hours, causing extensive damage to historic buildings, artworks, and infrastructure, marking it as the most disastrous event in the city's history.^[59] Similarly, the 2019 event, with seiches contributing to a peak of 187 cm, flooded approximately 85% of Venice for about 50 hours, resulting in substantial property losses to cultural heritage sites like St. Mark's Basilica and commercial areas.^[60] These incidents highlight how seiches test protective barriers and overwhelm urban infrastructure, leading to evacuations and long-term structural repairs.^[60] Shipping and port operations face hazards from seiche-induced currents and fluctuating water levels, which can ground vessels or disrupt navigation. In harbors, seiches generate strong reversible currents at entrances, causing moored ships to oscillate violently and endangering maritime traffic.^[10] During the June 21, 2025, seiche on Lake Superior, triggered by a low-pressure system, water levels fluctuated by nearly 4 feet in 2.5 hours, creating hazardous currents in Duluth Harbor that hindered boaters from entering via the shipping canal and prompted warnings from dispatchers.^[61] This event forced many ships to remain offshore to avoid risks, illustrating broader port disruptions where rapid level changes strand vessels on exposed bottoms or cause collisions.^[50] A notable historical example is the 1844 Buffalo seiche on Lake Erie, which generated destructive waves leading to 78 fatalities among dock workers and sailors.^[62] Economically, seiches drive costs through shoreline erosion and disruptions to maritime activities, with damages escalating due to climate change amplifying event frequency. On Lake Erie, seiches cause rapid, intense erosion that undermines properties and infrastructure, as seen in the April 1998 event where 10-14 foot waves destroyed 10 houses and damaged over 200 in Ottawa County, Ohio, incurring $3.7 million in losses.^[63] Cumulative regional impacts include nearly $975 million in building losses and $8.56 million in business interruptions from seiche-related flooding.^[63] In the Great Lakes, reduced ice cover and increased storm intensity from climate change are projected to heighten seiche frequency and severity, potentially doubling economic burdens on coastal economies through heightened erosion and activity disruptions.^[62]

Mitigation and Engineering

Design Principles for Protection

Design principles for protecting against seiches emphasize integrating the natural oscillation periods of water bodies into structural planning to prevent resonance, which can amplify wave heights and lead to structural failure or flooding. In dam and reservoir design, engineers calculate the fundamental seiche period—typically determined by basin length and water depth—using simplified formulas derived from shallow-water wave theory, ensuring that the reservoir's geometry avoids alignment with dominant forcing periods from winds, earthquakes, or landslides. This resonance avoidance is critical, as matching periods can increase wave amplitudes by factors of 2 to 5, potentially overtopping dams; for instance, U.S. Bureau of Reclamation guidelines recommend evaluating overtopping risks from seiche waves during seismic assessments to inform embankment stability, as seiche waves can cause reservoir sloshing leading to potential failure.^[64] Similarly, in harbor design, seiche periods are predicted through basin geometry analysis to modify entrance widths or depths, reducing amplification of incoming long waves that could damage moored vessels or quays.^[65] Breakwaters and baffles serve as primary damping mechanisms to dissipate seiche energy in enclosed or semi-enclosed water bodies like reservoirs and harbors. In reservoirs, vertical or horizontal baffles installed along the basin's length disrupt wave propagation and increase frictional losses, reducing oscillation amplitudes by up to 70% for fundamental modes, as demonstrated in studies of rectangular tank hydrodynamics under oscillatory forcing.^[66] These structures, often constructed from concrete or perforated plates, are positioned to target specific resonant modes without significantly impeding water flow or operations. For harbors, detached or floating breakwaters positioned at entrances absorb and scatter long-period waves, with their effectiveness enhanced by porous designs that promote viscous damping; such configurations can reduce wave heights by altering reflection coefficients.^[67] Wave equations, such as the linearized shallow-water model, are briefly referenced in simulations to optimize baffle and breakwater placements for targeted energy dissipation. Flood barriers must account for seiche amplification to safeguard low-lying coastal areas, incorporating dynamic elevation predictions into gate operations. The MOSE (Modulo Sperimentale Elettromeccanico) system in Venice, Italy, exemplifies this by deploying mobile gates at lagoon inlets to isolate the basin during high-water events, including those exacerbated by Adriatic seiches triggered by storm surges or bora winds, which can elevate levels by 20-50 cm through resonant oscillations.^[68]^[69] Designed to rise with predicted surges up to 3 meters, the barriers prevent seiche propagation into the lagoon, maintaining operational thresholds below 110 cm above mean sea level to protect infrastructure. This approach integrates real-time monitoring of seiche periods—ranging from 2 to 20 hours in the Adriatic—to time gate deployments, ensuring minimal ecological disruption while providing robust flood defense.

Recent Advances and Strategies

Recent advances in seiche mitigation have leveraged advanced numerical modeling to better predict and counteract coupled seiche-storm surge dynamics in coastal areas. The integrally coupled ADCIRC-SWAN model, which combines the ADvanced CIRCULATION (ADCIRC) model for water levels and currents with the Simulating WAves Nearshore (SWAN) model for wave propagation, has been instrumental in simulating these interactions for enhanced coastal protection. In a 2022 study on eastern Lake Erie, this model quantified seiche contributions to beach erosion (approximately 1.5% along a 2 km shoreline) and flooding in the Buffalo River, demonstrating its utility in informing the design of resilient structures like breakwaters and seawalls that withstand compound events.^[55] Further refinements, such as those exploring compound flooding from seiches and river flows, have improved mitigation strategies by reducing prediction errors in water level fluctuations and wave impacts.^[55] Hybrid defenses incorporating vegetation with traditional seawalls have emerged as a promising strategy for attenuating waves in confined bay environments. A 2025 modeling study using the XBeach non-hydrostatic framework analyzed 256 design scenarios at a New Jersey coastal site (Absecon Island), revealing that integrating vegetation (with densities exceeding 6,000 stems/m²) significantly reduces wave runup and overtopping on seawalls, particularly for wave powers below 80 kW/m. Optimal configurations, balancing seawall height (0.8–1.29 m) and vegetated area (over 30 m²), achieved up to 95% robustness against extreme waves (significant heights up to 4.6 m), offering cost-effective protection in bays.^[70] These nature-based hybrids enhance overall system performance while minimizing environmental disruption compared to hard structures alone.^[70] Research from 2021 to 2025 has also explored the potential of harvesting energy from persistent seiches in channels and embayments, transforming a hazard into a renewable resource through numerical simulations. A 2022 in-house model based on high-order shallow water equations (WENO-ADER) and unsteady Reynolds-averaged Navier-Stokes (URANS) assessed seiche energy in river bank lateral embayments under varying discharges (0.009–0.13 m²/s) and Froude numbers (0.48–0.58), identifying optimal conditions where cross-flow resonant seiches concentrate energy for efficient capture. The simulations, validated with less than 4% error in period predictions, highlighted seiches as a viable low-impact hydropower source for local or grid applications, though multi-modal wave periodicities pose challenges for device design.^[71] This approach not only mitigates seiche risks but also supports sustainable energy strategies in dynamic water bodies.^[71] International standards, such as Eurocode 8, incorporate seiche effects in seismic design for hydraulic structures, recommending dynamic analysis for reservoirs to assess sloshing loads. As of 2025, advances in machine learning for real-time seiche forecasting, integrated with IoT sensors, enable predictive mitigation in harbors and lakes, improving response times during meteorological triggers.^[72]^[73]

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