I-Seiche Waves, i-Inland Lake Tsunami, kanye Nokuwohloka Kwamanzi Okungalindelekile Kwechweba¶

I-seiche (ebizwa ngokuthi saysh) igagasi elimile elizulazula liye emuva naphambili ngaphakathi kwamanzi avalelwe noma avaleke kancane njengechibi Elikhulu, ichibi le-alpine, i-fjord, itheku, noma itheku. Ngokungafani namagagasi omoya avamile aphuka njalo ngemizuzwana emi-5 kuya kwengu-15 futhi aphazamise indawo engaphezulu kuphela, i-seche noma i-tsunami yechibi eliphakathi nezwe ibeka wonke umthamo wamanzi omcengezi ageleza ukusuka ogwini ukuya ogwini njengamanzi kubhavu otshekile. Ishayelwa ukugxuma okungazelelwe kwengcindezi ye-barometric, imigqa ye-squall, derecho imimoya, ukuzamazama komhlaba, noma ama-subaerial rockslide aphahlazeka emachibini ajulile nama-fjords, lokhu kuhlasela kungehlisa izinga lamanzi ezichwebeni ngamamitha angu-2 kuya ku-5 (amafidi angu-6.5 kuya ku-16.5) ngemizuzu, kuveza udaka lwamachibi aguquguqukayo nezibuyayo ezibuyayo. amanzi.

Okulimaza nakakhulu amagagasi ashukumisayo akhihlize umhlaba (megatsunami) ngaphakathi kwamachibi amancane e-alpine, amadamu amadamu, nama-glacial fjords, lapho izigidi zama-cubic metres zamatshe noma iqhwa eliwuqhwishi ziwela emanzini avaleleke bese ziphusha amagagasi agelezayo 10 kuya ku-500+ wamamitha (330+ kufika ku-60 kuya ku-6 izindonga eziphambene nesigodi) 180 imizuzwana. Ngokusho kwe-United States National Oceanic and Atmospheric Administration (NOAA), i-United States Geological Survey (USGS), kanye ne-World Meteorological Organization (WMO), izisulu zifa ngenxa yama-tsunami echibini futhi zibanjwa ngokuyinhloko ngoba zicabanga ukuthi i-tsunami physics ikhona kuphela olwandle oluvulekile, noma ngenxa yokuthi ziphuma emanzini asanda kuvezwa futhi zigeleza amanzi kungazelelwe.

Yenza lokhu manje¶

1. Khipha ama-breakwaters, amachweba, imilomo yemifula, namabhishi amanzi asheshayo akhuphuka noma awe ngokungavamile. Uma ubona ichibi noma ichweba amanzi egeleza ngokushesha, bona i-whirlpool egelezayo esheshayo emnyango wechweba noma umgudu webhuloho, noma uqaphele amanzi ekhasa phezu kwesihlabathi solwandle esomile lapho kungekho siphepho phezulu, shiya ugu ngokushesha. Hamba ubheke ogwini uye endaweni ephakeme okungenani 15 kuya ku-30 ​​amamitha (50 kuya ku-100 amafidi) ngaphezu kwamanzi noma ungene esitezi sesithathu noma ngaphezulu kwesakhiwo sikakhonkolo esiqinisiwe.
2. Shintshela uqonde phezulu odongeni lwesigodi uma uzwa ukuduma kwedwala noma iqhwa echibini eliyi-fjord noma entabeni. Emachibini amancane asezintabeni, emachibini amadamu, namachweba aphakeme (njengase-Norway, Alaska, British Columbia, Patagonia, New Zealand, noma i-European Alps), i-Rockslide eqhuma iqhwa weqa umcengezi100 kuya ku-250 wamakhilomitha ngehora (amamayela angu-60 kuya kwangu-155 ngehora). Uzoba ne-imizuzu engu-1 ukuya kwemi-4* ngaphambi kokuba igagasi lishaye usebe oluphambene. Dedela zonke izinto zokukhempa, ama-kayak, nezinto zokudoba, bese ushesha uqonde phezulu egqumeni eliwumqansa ngemva kwakho okungenani amamitha aqondile angu-*30 kuya kwangu-60 (amafidi angu-100 ukuya kwangu-200)**.
3. Ungaphinde ubuyele osebeni lolwandle, idokhu, noma i-marina ngemva kokuhlehla kwegagasi lokuqala. Ngenxa yokuthi i-seiche iyigagasi elinomsindo elikhalayo elibhampa liye emuva naphambili phakathi kosebe oluphambene lwechibi elivalekile noma itheku, amanzi azoqhubeka ezungeza amahora angu-*4 kuya kwangu-24+**. Ngenxa yokuphazamiseka okwakhayo nokukhuphuka komoya kwesibili noma amaza omcengezi abonisiwe, i- sesithathu, yesine, noma i-seiche oscillation yesihlanu amahora afikayo ngemva kwegagasi lokuqala ngokuvamile made futhi ayashesha kunokuqhuma kokuqala. Hlala endaweni ephakeme kuze kube i-ejensi yakho yesimo sezulu kazwelonke (efana ne-US National Weather Service, Environment and Climate Change Canada, noma i-MeteoSwiss) ikhansela Isexwayiso Sesikhukhula Sase-Lakeshore noma Iseluleko Se-tsunami.
4. Lahla isikebhe sakho emanzini uma ukuhlinzwa kuseduze; yisa umkhumbi wakho emanzini ajulile (>30 kuya ku-50 amamitha / 100 kuya ku-165 amafidi) KUPHELA uma kakade usendleleni ogwini. Ungalokothi ugijime wehlele ezikhumulweni zemikhumbi ezintantayo ngesikhathi sokudlidliza, i-meteotsunami, noma isenzakalo sokuduma kwechweba ukuze ubophe imigqa eyengeziwe noma uhlenge isikebhe sakho. Amashaneli asezikhumulweni zemikhumbi asebenza njengamafaneli acindezelayo lapho isivinini samanzi sifinyelela amakhilomitha angu-15 kuya kwangu-30 ngehora (amafindo angu-8 kuya kwangu-16), anqamula izinqwaba zensimbi, aklebhule amadokhu antantayo ezihlahleni zawo, futhi echoboza noma ubani obanjwe phakathi kwemikhumbi. Uma usuvele uhamba ngesikebhe emanzini avulekile lapho kuzwakala isixwayiso noma iwa liwa, suka ngokushesha ogwini futhi uphume emiseleni emincane uye emanzini ajulile avulekile okungenani 30 kuya ku-50 amamitha (100 kuya ku-165 amafidi) ukujula, ukhomba umnsalo wakho ngqo kugagasi lesikhathi eside elingenayo.
5. Suka ngokuphelele ezindongeni zamatshe, ezindongeni, nasezindongeni eziphambi kwechibi zikakhonkolo AMAHORA 6 NGEMVA kokuthi ulayini we-squall osheshayo noma i-derecho iwele ichibi elikhulu. ENyakatho Melika Enkulu Yamachibi (eLake Michigan, Lake Erie, Lake Superior, Lake Huron, Lake Ontario), Lake Geneva, Lake Garda, kanye neLake Garda, kanye neChibi i-Baikal4 ngemva kokushona kwelanga okudlula amahora angu-1 ukuduma kwezulu sekudlulile**, lapho ilanga libuya futhi ababhukudi noma abadobi babuyela endaweni yokudoba.
6. Shayela abezimo eziphuthumayo endaweni ephakeme uma noma ubani eshanelwe emanzini, futhi ungalokothi ugxumele ngemva kwabo. I-Seiche ibuyisa imisinga (i-backwash) idonsa izisulu phezu kwamatshe agelezayo acwile futhi ibakhiphele emanzini abandayo ajulile ngesivinini esingenakukwazi ukulwa nanoma yimuphi umbhukudi. Shayela inombolo yakho yasendaweni yezimo eziphuthumayo (911 e-United States nase-Canada, 112 ngaphesheya kwe-European Union, 999 e-United Kingdom, noma ubone konke izinombolo eziphuthumayo), jikijela idivayisi yokuntanta eboshiwe noma indandatho yokutakula endaweni eyomile ephakeme, futhi ugcine umkhondo obonakalayo wesisulu kunogada wasogwini noma izikebhe zokuhlenga umlilo.

Isihlahla sesinqumo se-Seiche, i-meteotsunami, nechibi le-wave impulse wave¶

Sebenzisa leli shadi lokugeleza lesinqumo senkundla ukuze uhlukanise phakathi kwe-atmospheric seiche, i-meteotsunami ye-squall-line, i-tsunami yechibi lokuzamazama komhlaba, kanye ne-alpine rockslide impulse wave.

flowchart TD
    Start["Ukuziphatha Okungajwayelekile Kwamanzi Echibini, e-Fjord, Echibini, noma Echwebeni:<br/>Ukuwohloka Kwamanzi Ngokungazelelwe, Ukubhonga Kwamanje, noma Ukuwa KweCliff"] --> TriggerCheck{"Iluphi uphawu oluyisixwayiso noma inhlamvu<br/>osanda kuyibona?"}

    TriggerCheck -->|"1. I-Thunderous Rockslide / Landslide / Glacier Calving<br/>NOMA Ukuzamazama Okunamandla Okuzamazama Eduze Nechibi noma i-Fjord"| ImpulseWave["CATASTROPHIC IMPULSE WAVE / SEISMIC LAKE TSUNAMI<br/>(Isikhathi Sokufika: 30 Amasekhondi ukuya 5 Amaminithi):<br/>1. LAHLA WONKE IGISHI: Ungapakishi amatende, ama-kayak, noma izikhwama<br/>2. I-SPRINT STRAIGHT UPHILL iqondane nogu <br/>3. Khwela okungenani amamitha aqondile angama-30 kuye kwangama-60+ (100 ukuya ku-200+ ft)<br/>4. Uma usesikebheni ngasogwini lolwandle: I-throttle egcwele enkabeni ejulile yomcengezi<br/> bese ukhomba ukhothame uqonde kumagagasi angenayo"]

    TriggerCheck -->|"2. Amanzi Ageleza Ngokungazelele Echwebeni / Ebhishi<br/>Aveza Ama-Mudflats, Amatshe, noma Izikebhe"| TroughArrival["UKUFIKA KWE-WAVE TROUGH (Seiche noma i-Meteotsunami):<br/>1. UNGALOKOTHI uhambe ku-lakebed noma ku-breakwater<br/>2. Memeza izexwayiso kuwo wonke umuntu osezimpahleni nasemabhishi<br/>3. Gijima phakathi nezwe 300 kuya ku-500 m futhi ugibele 10 kuya ku-15 m (33 kuya ku-50 ft)<br/>4. Lindela imitha elingu-1 ukuya ku-4 (3 ukuya ku-13 ft) udonga olukhuphukayo lwamanzi<br/> phakathi kwemizuzu engu-1 ukuya kweyi-10"]

    TriggerCheck -->|"3. Ukuduma Okusheshayo / I-Derecho Iwele Ichibi<br/>Amaminithi angu-30 kuya emahoreni angu-4 adlule (Isibhakabhaka Manje Sicacile)"| PostStormSeiche["POST-STORM METEOTSUNAMI / REFLECTED SEICHE:<br/>1. HLALA UNGANENGE ngokuphelele ezinsikeni zikakhonkolo, izindawo zokunqamula amanzi, nemilomo yemifula<br/>2. Gcina izingane nezilwane ezifuywayo zisuka onqenqemeni lwamanzi<br/>3. Buka ukuguquka kweleveli yamanzi emizuzu emi-5 ukuya kwengama-20<br/>4. Ungaphinde ungene kuma-marina kuze kube yilapho i-oscillation ima (amahora ama-4 kuye kwayi-12+)"]

    TriggerCheck -->|"4. Ifakwe ngaphakathi kwesiteshi sase-Marina / Harbour<br/>Lapho Udlame Lwamanje Nokuguquka Kwamanzi Kuqala"| MarinaAction{"Ingabe usemhlabeni okwamanje<br/>noma usuvele ugibele umkhumbi?"}

    MarinaAction -->|"Ezweni / Edokini"| LeaveBoat["SHIYA ISIKEPE NGOKUSHESHA:<br/>1. Gijima amadokhu antantayo endaweni ephakeme eqinile MANJE<br/>2. Ungalokothi uzame ukulungisa imigqa yokubongela ngesikhathi sokukhuphuka kwechweba<br/>3. Buka imigqa enqamukayo (ingozi ye-whiplash) namadokhi achotshoziwe"]

    MarinaAction -->|"Ngena Emkhunjini Emanzini Avulekile"| DeepWater["IYA KUSEKUJINI AMANZI AVULIWE (>30 kuya ku-50 m / 100 kuya ku-165 ft):<br/>1. UNGAZAMI ukungena emlonyeni omncane wechweba noma umsele<br/>2. Jikela emanzini ajulile avulekile kude namachweba namawa<br/>3. Gada i-VHF Marine Channel 16 kuze kucace"]

Ukuqhathanisa izingozi ezi-5 zemigodi evalekile kanye nezikhukhula zasogwini¶

Abantu abahlala noma abavakashele emachibini, kumadamu, ama-fjords, namatheku bahlangabezana nezinhlobo ezinhlanu ezihlukene zezinhlekelele ezifika kungazelelwe ezingeni lamanzi. Nakuba bobahlanu bangaminza abantu ezinsikeni futhi baphihlize ama-marina, amandla abo okushayela, izikhathi zamagagasi, kanye nezindawo ezidingekayo zokuphuma zihluka kakhulu.

I-physics ye-Seiche ne-Merian's Formula: Kungani amachibi abiyelwe eshelela njengobhavu wokugeza¶

Ukuqonda ukuthi i-seiche yakheka kanjani kuchaza ukuthi kungani amanzi engase anyamalale endaweni engasemanzini yedolobha elilodwa ngenkathi ngesikhathi esifanayo egcwala idolobha eliphesheya kwechibi elifanayo:

1. Ukusetha Umoya, I-Barometric Tilting, kanye Nokukhishwa Kungazelelwe¶

Lapho imimoya enamandla eqinile evela esiphephweni sasebusika, ingaphambili elibandayo, noma i-derecho ivunguza ngobude bechibi elide (njengemimoya esuka eningizimu-ntshonalanga iye enyakatho-mpumalanga ivunguza yehle ngamakhilomitha angu-388 ubude beLake Erie ngaseBuffalo, eNew York), ukungqubuzana komhlaba kudonsa izigidigidi zama-cubic metres ogwini. Ngesikhathi esifanayo, umfutho we-barometric ophezulu ngemuva kwesiphepho uphusha phansi ekugcineni komoya wechibi kuyilapho ukucindezela okuphansi kwe-barometric ngaphambili kudonsa amanzi phezulu ekugcineni kokwehla komoya (njalo \(1\text{ hectopascal/millibar}\) umehluko wokucindezela komoya ushintsha ubude bamanzi ngokuthi \(1\text{ centimeter}\)). - Phakathi nokusethwa komoya okwedlulele kweLake Erie, izinga lamanzi e-Toledo, e-Ohio (engxenyeni esentshonalanga) lehle ngo \(2.1\text{ ukuya }2.4\text{ metres}\) (\(7\text{ kuya }8\text{ feet}\)) ngaphansi kokuvamile, okuveza amakhilomitha odaka omile nokuvala imboni yamandla enyukliya namalahle ngesikhathi esisodwa. \(2.1\umbhalo{ ukuya }2.4\umbhalo{ metres}\) (\(7\text{ to }8\text{ feet}\)) ngaphezu kokuvamile* e-Buffalo, New York (empumalanga ekugcineni), udala ukutsheka okuphelele kwamanzi asuka ekupheleni angu- \(4.5+\text{ meters}\) (\(15+\text{ feet}\)). - I-Slosh Back: Lapho umoya ushona phansi noma ushintsha indlela, amandla adonsela phansi adonsela leyo ntaba yamanzi ihlehle ihlehle phansi ngomthambeka wechibi. Ngenxa yomfutho we-hydrodynamic, amanzi awamane abe isicaba ezingeni elivamile: adlula ukulingana, akhukhule ekugcineni osentshonalanga ngenkathi edonsa indawo esempumalanga, abese ebhampa emuva naphambili ngaphesheya komgodla izinsuku eziningi.

2. Ifomula kaMerian: Ukubikezela Ukuthi ILake Oscillates Lishesha Kangakanani¶

Wonke amachibi avaliwe, ichibi, nechweba linesikhathi esinqunyiwe sokukhala kwemvelo (\(T\), isikhathi esisithathayo somjikelezo owodwa wokuya emuva naphambili) obuswa Ifomula kaMerian yegagasi elimile elinenodi eyodwa (uninodal):

Kuphi: - \(L\) = Ubude bechibi noma isitsha sechweba eduze kwe-eksisi ye-oscillation (ngamamitha) - \(g\) = Ukusheshisa amandla adonsela phansi (\(9.81\text{ m/s}^2\)) - \(h\) = Ukujula okumaphakathi kwamanzi (ngamamitha)

Ngenxa yokuthi i-seiche iyigagasi elithi lamanzi angashoni (okusho ukuthi ubude bayo begagasi bude kakhulu kunokushona kwechibi), isivinini salo (\(c = \sqrt{g \cdot h}\)) sincike ngokuqinile ekujuleni kwamanzi: - Amachibi ajulile, amafushane e-alpine noma amatheku anyakaza ngokushesha okukhulu: IChibi Geneva (\(73\text{ km}\) ubude, \(154\text{ m}\) isilinganiso sokushona) inesikhathi sokuqala sokuzamazama kwe-uninodal 73 amaminithi; I-Lake Tahoe (\(35\text{ km}\) ubude, \(305\text{ m}\) ukujula okumaphakathi) yehlela emuva naphambili ngemizuzu engu-18 ukuya kwengama-21; a \(1\text{-kilometer}\)-long marina basin (\(10\text{ m}\) deep) wehla njalo 3 kuya kumaminithi angu-6. - Amachibi amade, angashoni anyakaza kancane njengamagagasi amakhulu: I-Lake Erie (\(388\text{ km}\) ubude, kodwa kuphela \(19\text{ m}\) [62 feet] ukujula okumaphakathi) inesikhathi sokuzamazama esingokwemvelo esilingana no-14 amahora.

3. I-"Nodal Line" vs. "Antinode" Trap¶

Kumagagasi e-seiche amile, indawo emaphakathi nechibi isebenza njengendawo emile ye-pivot ebizwa ngokuthi nodi (noma i-nodal line), kuyilapho ugu oluphambene lusebenza njenge antinode: - E-Shoreline Antinodes (Emaphethelweni Echibi): Ukuphakama kwamanzi aqondile kuya phansi naphezulu kuya kubukhulu obukhulu (\(2\text{ kuya ku-}5\text{ metre}\)), amabhishi agcwele izikhukhula namadokhi, kuyilapho imisinga evundlile incane kakhulu esiqongweni kanye nomkhombe. - E-Mid-Lake Nodal Line (kanye ne-Narrow Straits njenge-Straits of Mackinac, Messina, noma Euripus): Izinga lamanzi aqondile alishintshi nhlobo, kodwa ivolumu yechibi kufanele igijime iye phezulu iye phambili naphambili ku-node, ikhiqize udlame, ehlehlisa amanzi angaphansi kwamanzi nangaphezulu ageleza amapayipi, ageleze futhi aphume emanzini. ukulawula.

I-Meteotsunamis ne-Proudman Resonance: Igagasi elingamamitha angu-3 lishaya kanjani ngaphansi kwesibhakabhaka esinelanga¶

Ngo-Juni 26, 1954*, umugqa osheshayo wokuduma kwehlobo wawela eningizimu Ichibi laseMichigan usuka enyakatho-ntshonalanga uya eningizimu-mpumalanga. Cishe emahoreni amabili ngemva kokudlula kwesiphepho, lapho isibhakabhaka phezu Chicago, Illinois libalele ngokuphelele futhi izinkulungwane zabantu zazidoba futhi zishiswa nelanga ngasezimpahleni zikakhonkolo e-Montrose Harbour nase-North Avenue Beach, okungazelelwe \(3\text{-meter}\) (\(10\text{-foot}\)) udonga lwamanzi lwashayisa abantu echibini laseChicago, lashona echibini. abantu abangu-8.

Le nhlekelele kube meteotsunami eqalwe ngu-Proudman Resonance: 1. Ukufanisa Isivinini (I-Proudman Resonance, 1929): Njengomugqa we-squall, i-derecho, noma igagasi lomkhathi elidonsela phansi ligijima linqamula ichibi noma ishalofu le-continental elingashoni (njenge Gulf of Mexico noma i-Balearic Sea), umfutho walo we-barometric ngokuzumayo weqa kanye nokuvunguza komoya kusunduza umbhalo omncane ongu-\(5\0\text{}ku-\)1\umbhalo{}kuya ku-\(2{} }4\text{ inch}\)) ingcindezi endaweni yamanzi. Imvamisa, leli gagasi elincane lihamba ngesivinini esihlukile kunesiphepho bese liyashabalala. Nokho, uma isivinini sokuya phambili sesiphepho (\(U\)) sifana nesivinini samagagasi esingokwemvelo samanzi angashoni phansi echibini (\(c = \sqrt{g \cdot h}\)), isiphepho sihlala sikhiyelwe ngqo phezu kwamagagasi anyakazayo, siqhubeke siphosela amandla e-kinetic ku-crest yamagagasi ngaphezu kuka-\(50\umbhalo{{{{kuya ku-\)150}}umbhalo" ukuya ku-\(300} }90\text{ miles}\)) wamanzi avulekile futhi ikhulise ukuphakama kwegagasi ngokuthi \(5\text{ ukuya }15\text{ times}\). - Isibonelo, eningizimu yeLake Michigan lapho ukujula kwamanzi (\(h\)) cishe ku \(55\text{ to }65\text{ meters}\) (\(180\text{ to }215\text{ feet}\)), isivinini semvelo samanzi angashoni ngu-\(c = \sqrt{9.81 \izikhathi ezingu-62} 4/2} **\)87\text{ km/h}$ (\(54\text{ mph}\))**. Noma nini lapho i-derecho yasehlobo noma umugqa we-squall uwela eningizimu yeLake Michigan cishe cishe \(85\text{ ukuya }95\text{ km/h}\) (\(50\text{ to }60\text{ mph}\)), i-Proudman Resonance iyakhiya futhi yakhe i-meteotsunami ebhubhisayo. 2. I-Edge Reflection and Shoaling Amplifier: Ngenhlekelele yase-Chicago yango-1954, isiphepho sasuka e-Chicago salibangisa e-Michigan City, e-Indiana. I-meteotsunami ishaye ugu olugobile oluseningizimu-mpumalanga yeLake Michigan kuqala, yagxuma yasuka ogwini lwase-Indiana njengebhola le-billiard lishaya umcamelo, futhi yahamba ihlehla yanqamula ichibi ukuze ishaye i-Chicago ngemva kwamahora amabili ngaphansi kwesibhakabhaka esicwathile, igibela phezulu eshalofini elingaphansi kwamanzi elingashoni khona lapho ezinsikeni.

Ukudilika komhlaba kanye namagagasi e-glacier-calving: I-500-metres fjord kanye ne-reservoir megatsunami¶

Nakuba ama-tsunami olwandle nokuzamazama kwechibi ngokuvamile kufinyelela ku-\(1\text{kuya }10\text{ meters}\) (\(3\text{ to }33\text{ feet}\)), amagagasi aguquguqukayo angaphansi komhlaba ngaphakathi kwama-fjords amancane, amachibi asezintabeni, namadamu amadamu akhiqiza amaza amakhulu kunawo wonke emlandweni womuntu: - Lituya Bay, Alaska (July 9, 1958): An earthquake loosened \(30\text{ million cubic meters}\) (\(40\text{ million cubic yards}\)) of rock high above Gilbert Inlet; the rockslide plunged into the fjord and pushed an impulse wave \(524\text{ meters}\) (\(1,720\text{ feet}\)) vertically up the opposite mountain ridge, higher than the Empire State Building. - Vajont Dam Reservoir, Italy (October 9, 1963): A \(260\text{-million-cubic-meter}\) landslide slid off Monte Toc into the narrow reservoir lake behind Vajont Dam, displacing the water into a \(250\text{-meter}\) (\(820\text{-foot}\)) wave that overtopped the concrete dam intact and wiped out the valley town of Longarone below, killing nearly 2,000 people in under 7 minutes. - Tafjord (1934, \(62\text{ m}\) wave, 40 dead) and Loen / Lovatnet Lake, Norway (1905 and 1936, \(40\text{ to }74\text{ m}\) waves, 135 dead): Rockslides falling off steep Norwegian fjord and lake cliffs generated waves that obliterated lakeside villages within 2 minutes. - Lake Geneva, Switzerland/France (563 AD Tauredunum Tsunami): A mountain collapse at the Rhône River delta triggered an underwater turbidite slump that sent an \(8\text{ to }13\text{ meter}\) (\(26\text{ to }43\text{ foot}\)) tsunami down the length of Lake Geneva, overtopping the city walls of Geneva 70 minutes later.

4 Mandatory Survival Rules for Campers, Kayakers, and Boaters in Fjords and Alpine Lakes¶

1. Never pitch a tent on a low gravel beach, alluvial fan, or shoreline spit inside a steep fjord or glacial lake. In glaciated valleys (Alaska, British Columbia, Norway, Greenland, Chile/Patagonia, New Zealand), melting permafrost and retreating glaciers leave unstable mountain slopes and hanging ice cliffs (seracs) poised directly above deep water. Always camp on high bedrock benches at least 20 to 30 vertical meters (65 to 100 feet) above the waterline.
2. Keep at least 400 to 800 meters (0.25 to 0.5 miles) away from the face of any tidewater or lake-terminating glacier. When a massive slab of glacier ice calves off into the water, or worse, when an underwater ice foot (submarine calving) detaches from the glacier bed and shoots upward to the surface like a giant cork, it generates a violent steep-faced impulse wave that capsizes kayaks and tour boats in seconds.
3. If you are kayaking or landing on a fjord beach when a rockslide or calving boom echoes across the water:
4. If you are on or within 20 meters of shore: Abandon your kayak on the beach immediately (do not spend 15 seconds tying it up or pulling it above the tide line) and sprint straight up the steep hillside as high as you can climb in the 60 to 120 seconds before impact.
5. If you are paddling in open water more than 100 meters offshore: Turn your bow 90 degrees perpendicular to the oncoming wave crest (pointing straight into the wave), brace low with your paddle ready for a high brace or Eskimo roll, and paddle away from shallow shoals or cliff walls where the wave will break and reflect.

Harbor resonance and marina surge survival for boaters and dock workers¶

When a distant offshore earthquake tsunami (see our tsunamis guide), a continental-shelf meteotsunami, or long-period ocean swell enters a coastal harbor or lake marina, harbor resonance (Helmholtz resonance) turns a seemingly minor water fluctuation into a violent hydraulic shredder inside the basin.

Why Marinas Are the Most Dangerous Place During a Seiche or Tsunami Advisory¶

1. Hydraulic Bottleneck Acceleration: When the water level inside a \(1\text{-square-kilometer}\) harbor drops or rises by \(1.5\text{ meters}\) (\(5\text{ feet}\)) in just 5 minutes, millions of tons of water are forced through a narrow \(50\text{-meter}\)-wide jetty entrance. Water speeds at the harbor mouth and around bridge pilings accelerate to 15 to 35 kilometers per hour (8 to 19 knots), creating standing hydraulic jumps, whirlpools (eddies), and scouring trenches that rip navigation buoys and channel markers out by their concrete anchors.
2. Floating Dock Guide-Pile Topping and Grounding:
3. During the rapid drawdown trough, harbor water drains so low that boats with deep keels (\(1.5\text{ to }3\text{ meters}\)) slam down onto the hard harbor bottom, roll over onto their sides, and flood cleanly over their gunwales when the next wave crest roars back in 3 minutes later.
4. During the rapid surge peak, floating docks can float right off the tops of their vertical steel or wood guide pilings, breaking loose with 50 boats still tied to them and smashing across the harbor like a runaway barge.
5. Lethal Mooring Line Snapback: When a 10-ton boat tied with taut nylon dock lines is suddenly lifted 3 meters or dropped into a trough by a 12-knot harbor current, either the cleat rips out of the fiberglass deck or the nylon line stretches to its breaking point and snaps, whipping back across the dock at over 300 kilometers per hour (185 miles per hour), fast enough to amputate limbs or kill a bystander instantly.

Step-by-Step Boat and Marina Protocol¶

• If you are at home or in the parking lot when a Tsunami Advisory, Meteotsunami Warning, or Severe Seiche Warning is issued: Do NOT drive down to the marina to check on your boat. No boat or insurance deductible is worth being trapped on a collapsing floating dock when the harbor drains and refills.
• If you are already on the dock when water begins surging or draining: Drop everything and walk immediately off the gangway onto solid high ground behind the seawall.
• If you have 2+ hours of advance warning before a distant wave or forecast storm seiche AND authorities permit vessel evacuation:
• Either haul the boat out of the water onto a trailer on high ground, OR pilot the vessel out of the harbor before currents start and hold station in deep open water greater than 30 to 50 meters (100 to 165 feet) deep (for major ocean tsunamis, Coast Guard guidance specifies greater than 55 to 180 meters [30 to 100 fathoms]).
• If leaving a boat moored in a slip before evacuating on foot: double up spring lines and bow/stern lines with maximum slack and chafe guards to allow for a 2-to-3-meter vertical rise and fall (applicable only on fixed piers where slack prevents hanging the boat by its cleats during a low trough).

Regional high-risk zones and local names to recognize worldwide¶

Many regions use local warning terms for seiches and meteotsunamis:

Imibuzo ejwayelekile ukubuzwa¶

Can a real tsunami happen in an inland freshwater lake like Lake Tahoe, Lake Geneva, or the Great Lakes?¶

Yes, inland lakes experience two distinct types of genuine tsunamis that behave identically to ocean tsunamis. First, meteorological tsunamis (meteotsunamis) occur frequently on the North American Great Lakes when fast-moving squall lines or derechos travel at the exact speed of the lake's shallow-water wave, building 1 to 3+ meter (3 to 10+ foot) surging waves that strike hours after the storm passes. Second, tectonic and landslide lake tsunamis occur in deep fault-bounded or alpine lakes such as Lake Tahoe, Lake Geneva, Lake Lucerne, and Norwegian or Alaskan fjords whenever an earthquake ruptures a lake-floor fault or a massive rockslide collapses into the water, generating deadly waves up to 10 to 100+ meters high in minutes.

What is the difference between a seiche and a tsunami?¶

A tsunami is a progressive wave train that radiates outward from a sudden localized displacement of water (such as an earthquake fault rupture, underwater landslide, or atmospheric pressure jump) and travels across open water to strike a shoreline. A seiche is a standing wave in which the entire enclosed or semi-enclosed basin (a lake, reservoir, fjord, or harbor) oscillates back and forth at its natural resonant frequency like water sloshing in a bathtub. Importantly, a tsunami, meteotsunami, or strong wind storm often acts as the initial trigger that sets an enclosed lake or harbor into a multi-hour resonant seiche oscillation.

Why did the water in our lake or harbor suddenly drop by 2 meters (6.5 feet) and expose the muddy bottom?¶

A sudden, rapid drop in water level along a lake beach, river mouth, or harbor occurs for one of two life-threatening reasons: either sustained storm winds or barometric pressure differences have pushed the basin's water toward the opposite shoreline (wind set-up), or the leading trough of a meteotsunami, seiche, or landslide tsunami has just arrived at your shore. In either case, gravity will inevitably pull that displaced mountain of water violently back toward your shoreline, often arriving within 1 to 15 minutes as a fast-moving turbulent bore. Never walk out onto an exposed lakebed or harbor floor; evacuate immediately to high ground.

Why are the third or fourth waves of a lake seiche or meteotsunami often larger than the first wave?¶

Unlike a single breaking wind wave, a seiche or meteotsunami reflects off the solid shorelines of an enclosed lake or V-shaped bay and bounces back and forth across the basin for hours. When a reflected wave traveling back across the lake collides and merges with a second incoming wave train, a secondary squall-line surge, or a narrowing harbor funnel (constructive wave interference and harbor resonance), the combined wave height amplifies dramatically. Always stay off beaches, piers, and marinas for several hours after the first surge until official water-level gauges confirm the oscillations have subsided.

Imithombo ihloliwe¶

• National Oceanic and Atmospheric Administration (NOAA, United States) National Ocean Service and Great Lakes Environmental Research Laboratory (GLERL): What Is a Seiche? What Is a Meteotsunami? Great Lakes Water Level Oscillations, Proudman Resonance Physics, and Real-Time Meteotsunami Detection.
• United States Geological Survey (USGS): Landslide-Generated Impulse Waves and Subaerial Megatsunamis in Fjords, Lakes, and Reservoirs (Lituya Bay 1958, Taan Fiord 2015, and Barry Arm Hazard Assessments).
• National Weather Service (NWS / NOAA, United States): Lakeshore Flood Warning Criteria, Safe Boating During Tsunami/Seiche Advisories, and Reconstruction of the June 26, 1954 Chicago Lake Michigan Meteotsunami.
• World Meteorological Organization (WMO) and Intergovernmental Oceanographic Commission (IOC / UNESCO): Global Guide to Meteotsunamis, Harbor Resonance (Rissaga, Abiki, Šćiga), and Non-Seismic Coastal/Lacustrine Sea Level Hazards.
• Federal Office for the Environment (FOEN, Switzerland) and Norwegian Water Resources and Energy Directorate (NVE): Alpine Lake Tsunamis (Lake Geneva 563 AD, Lake Lucerne) and Norwegian Fjord Rockslide Early Warning Protocols (Åknes / Geirangerfjord).

Iziqondiso ezihlobene¶

• Tsunamis: natural warning signs and high-ground evacuation
• Ukuqubuka kwesiphepho, ama-king tides, nokukhukhula kwamanzi ogwini
• Derechos, straight-line winds, and microburst survival
• Landslides, mudslides, and debris flows
• Ukuhlenga ukuminza kanye nosizo lokuqala lwamanzi