Fallo da presa e evacuación de ondas de inundación catastróficas¶

Un fallo catastrófico dunha presa, unha ruptura de diques ou Glacial Lake Outburst Flood (GLOF) libera millóns e centos de millóns de metros cúbicos de auga embalsada en cuestión de minutos, xerando unha onda de inundación tipo tsunami no interior que percorre vales fluviais enteiros ata o leito rocoso. A diferenza das crecidas de ríos estacionais ordinarias que aumentan centímetro a centímetro ao longo de horas ou días, un encoro roto, o depósito de residuos de minas fallido ou a morrena glacial colapsada libera un muro de auga, barro, pedras, árbores rotas e edificios esmagados 3 a 30 metros (de 10 a 1000 pés por 10 a 1000 pés por hora de viaxe) (12 a 40 millas por hora). Debido a que esta onda de escombros hiperconcentrada ten ata o dobre da densidade da auga lisa e rompe as casas estándar de madeira e ladrillo ao impactar, abrigarse dentro dunha casa ou subirse a un tellado residencial dentro da zona de inundación adoita ser fatal: a supervivencia depende enteiramente da evacuación perpendicular inmediata ata os muros do val por encima da altura máxima do encoro.

Fai isto agora¶

1. Evacue inmediatamente perpendicular á canle do río (directamente pola ladeira do val, nunca río arriba nin augas abaixo). Non perda 5 minutos facendo as maletas, bloqueando as portas ou intentando superar unha onda de inundación ao longo dunha estrada de fondo do val que segue o río. Mire o terreo a ambos os lados do val e sube directamente pola ladeira, o acantilado ou a cresta máis empinada alcanzable nun ángulo de 90 graos lonxe da canle do río ata que esteas polo menos a 15 a 30 metros (de 50 a 100 pés) por riba do fondo do val (ou por riba da túa **zona de inundación da presa local).
2. Vaia a pé inmediatamente se as estradas do val están bloqueadas, bloqueadas por desprendementos de terra ou cruzan pontes. Unha onda de inundación que rompe un encoro ou GLOF viaxa a 20 a 65 quilómetros por hora (de 12 a 40 millas por hora) e destrúe primeiro as pontes fluviais baixas. Se o tráfico deixa de moverse ou se atopa a 5 quilómetros (3 millas) dunha presa, un dique ou unha canle dun val glaciar que fallan, abandone o seu vehículo inmediatamente e suba a pé pola ladeira. Dez minutos de subida rápida colócano de 60 a 100 metros verticais (200 a 330 pés) por riba do leito do río, fóra do alcance de case calquera onda de inundación.
3. Recoñece os 4 sinais de advertencia naturais cando fallan as alertas sen fíos ou as sirenas. Os encoros colapsan e os GLOF ocorren con frecuencia pola noite, durante terremotos ou durante tormentas de choiva extremas que derrumban primeiro as torres móbiles. Evacue inmediatamente a terras elevadas se observa: (a) unha vibración continua e de baixa frecuencia do chan e un ruxido enxordecedor que soa como un tren de mercadorías ou un escuadrón de avións a reacción baixando polo canón; (b) unha caída súbita e antinatural OU un repentino aumento de lama no nivel da auga do río; © un forte cheiro a terra recén triturada, xofre e piñeiros/cedros rotos levado por un súpeto vento frío polo val; ou (d) un terremoto grave ou un desprendemento de rochas río arriba cando vives debaixo dun encoro ou dun lago glaciar.
4. Never drive or walk through moving floodwater or across a bridge over a surging river. Just 15 centimeters (6 inches) of fast-moving water knocks an adult off their feet, and 30 to 60 centimeters (1 to 2 feet) of rushing water floats and sweeps away heavy four-wheel-drive pickup trucks and SUVs. In addition, never cross a bridge when floodwaters are approaching the bridge deck or churning violently around the piers: high-density debris flows and boulders batter bridge pilings out from underneath the asphalt seconds before the roadway collapses.
5. Se vives detrás dun dique de terra que comeza a "ferver a area", filtrar auga lamada ou caer, evacúao antes de que rompa. Antes de que estoupe un dique de terra ou un encoro de terraplén, a auga a alta presión que fai un túnel debaixo ou a través do chan crea fontes burbullantes de auga lamada e area** (** ou ** e ) lado de terras secas. Aínda que a auga clara que se filtra lentamente é común, auga lamada e chea de limo que brota dunha fervención de area ou dunha fenda/sumidoiro visible na coroa do dique significa que a erosión interna está a desgarrar o dique por dentro e pode producirse unha brecha catastrófica a toda profundidade en minutos. Chama ao teu número de emerxencia local (911 nos Estados Unidos e Canadá, 112 en toda a Unión Europea, 999 no Reino Unido ou consulta todas as números de emerxencia) e marcha inmediatamente.
6. Manténgase en terreos altos despois de que pase a primeira onda: seguen ondas secundarias, colapsos de bancos e lodos tóxicos. Os fallos das presas e os GLOF ocorren con frecuencia en multiplicacións xa que a erosión regresiva ensancha a brecha ou os lagos glaciares secundarios e os encoros de deslizamento de terra estalan río arriba. Mesmo despois de que os niveis de auga baixen, mantéñase fóra do fondo do val recén fregado: as paredes dos canóns saturados colapsan rutineiramente nun desprendementos, e os residuos das minas ou o lodo das inundacións industriais adoitan actuar como area movediza atada con metais pesados, cianuro, sumidoiros e liñas de transmisión de alta tensión abatidas.

Dam failure, levee breach, and GLOF survival decision tree¶

Use este diagrama de fluxo de decisión rápida no momento en que reciba unha vixilancia/aviso de presa, detecte ferver a area dun dique ou escoite o ruxir do canón río arriba.

flowchart TD
    Start["Dam Failure Alert, Levee Breach Warning,<br/>Glacial Lake Outburst (GLOF) Siren, OR Upstream Canyon Roar"] --> TimeCheck{"How much lead time do you have before<br/>flood wave arrival?"}

    TimeCheck -->|"IMMINENT BREACH (Seconds to <15 Mins)<br/>Siren wailing, Emergency Alert, or Roar heard"| RunUpSlope["ABANDON BUILDINGS & VEHICLES IF BLOCKED:<br/>Run on foot at 90 degrees PERPENDICULAR to the river channel<br/>Climb straight up the nearest hillside, bluff, or valley wall<br/>Aim for >= 15 to 30 vertical meters (50 to 100 feet) above valley floor"]

    RunUpSlope --> TrappedCheck{"Are you completely surrounded by water<br/>on flat floodplain with zero hills?"}
    TrappedCheck -->|"No: Reached high ground"| StayHigh["Stay on high ground for multiple waves<br/>Do NOT descend to rescue possessions or touch mud"]
    TrappedCheck -->|"Yes: Flat terrain, wave arriving now"| VerticalLastResort["LAST RESORT VERTICAL EVACUATION:<br/>Climb the tallest steel-frame or reinforced concrete building (3+ stories)<br/>Avoid wood-frame houses, mobile homes, and bridges<br/>Bring flotation device; never lock yourself in a closed attic"]

    TimeCheck -->|"EARLY WARNING (30 Mins to Several Hours)<br/>FEMA / Weather Service 'Dam Watch' or Levee Overtopping Forecast"| VehicleEvac["1. Grab Go-Bag, medications, pets, and family immediately<br/>2. Drive UP and OUT of the mapped Dam Inundation Zone<br/>   using highland roads (NEVER drive along river-bottom roads or over low bridges)<br/>3. If traffic jams inside the valley, park off road and hike uphill on foot"]

    VehicleEvac --> LeveeInspect{"Did you spot a 'Sand Boil' or muddy seepage<br/>at the base of a nearby dam or levee?"}
    LeveeInspect -->|"Yes: Muddy water bubbling up"| ReportPiping["CRITICAL PIPING FAILURE IN PROGRESS:<br/>Do NOT try to plug the hole yourself.<br/>Evacuate the floodplain immediately and call 911 / 112 / 999<br/>to report exact GPS location of the muddy sand boil"]
    LeveeInspect -->|"Non"| StayOutZone["Check in with family outside the flood zone<br/>Monitor NOAA Weather Radio / National Emergency Broadcasts"]

Comparing the 4 types of catastrophic impoundment failures¶

Not all dam and barrier failures behave the same way. Concrete arch dams fail almost instantaneously like an exploding water tank, earthen embankment dams erode progressively over 20 to 90 minutes, glacial lakes unleash boulder-filled debris flows down mountain gorges, and mine tailings dams release rivers of suffocating toxic sludge.

Understanding official dam and levee emergency alert levels¶

In the United States (National Weather Service / FEMA / US Army Corps of Engineers), Canada, the United Kingdom (Environment Agency), the European Union, and Himalayan/Andean GLOF monitoring networks, authorities use standardized escalation tiers. Knowing the difference between a Watch and an Emergency Warning tells you whether you have hours or seconds:

1. Dam / Levee Watch (Advisory or Condition B: Potential Failure Developing):
2. What it means: Floodwaters behind a dam or levee are approaching dangerous capacity, auxiliary spillways are discharging at maximum rate, or engineers have discovered a structural defect (such as seepage or minor slumping) that could lead to failure if conditions worsen.
3. What you must do NOW: Pack your emergency Go-Bag, load mobility-limited family members, infants, and pets into your vehicle, move livestock to high pasture, and evacuate the inundation zone early while roads and bridges are still completely dry.
4. Flash Flood Warning for Dam Failure / Levee Breach (Condition A: Imminent or Active Failure):
5. What it means: The dam or levee is actively failing right now or is guaranteed to breach within minutes. Wireless Emergency Alerts (WEA) on mobile phones will sound a loud alarm tone with the header "FLASH FLOOD WARNING: DAM FAILURE" or "EXTREME EMERGENCY: EVACUATE TO HIGH GROUND."
6. What you must do NOW: Drop everything and move to high ground immediately. Do not pack possessions; grab only the people next to you and climb out of the valley floor.
7. High-Volume Spillway Release Warning (Non-Breach Controlled Flood):
8. What it means: To keep an earthen dam from overtopping and collapsing completely during historic rainfall (such as during a hurricane or atmospheric river), dam operators are forced to open the emergency floodgates or auxiliary spillway to release massive volumes of water down the river channel.
9. What you must do NOW: Evacuate all low-lying riverfront homes, campgrounds, and floodplains immediately, as river levels can rise 3 to 10 meters (10 to 33 feet) in a single hour even though the dam itself has not broken.

Flood Wave Arrival Time, Velocity, and Impact Force by Distance Downstream¶

Understanding how a dam-break wave or GLOF transforms as it travels down a canyon helps you estimate how many minutes you have to climb to safety:

How to spot a failing earthen dam or levee: The "Clear vs. Muddy Seepage" rule¶

Millions of people live directly behind earthen flood control levees, canal embankments, farm stock dams, or hydroelectric earthfill dams. If you are inspecting a levee or earthen dam during high water, civil engineers use one simple visual test to distinguish harmless water seepage from a deadly impending breach:

• Clear Water Seeping Slowly = Watch Closely, Low Immediate Breach Risk: When water stands high against an earthen levee for days, the soil becomes saturated and clear water often sweats or trickles slowly out near the bottom toe. If the water is crystal clear and flow rate is steady, the soil skeleton inside the levee is holding firm (engineers often ring a clear seep with a horseshoe collar of sandbags simply to raise the back-pressure head).
• Muddy, Dirty, Silt-Laden Water Gushing or Bubbling = EVACUATE IMMEDIATELY (Active Piping): If the water bubbling out of the ground or flowing out of the back slope of the dam is cloudy, brown, muddy, or piling up a cone of sand and gravel like a miniature volcano (a "sand boil"), the rushing water is actively washing the dirt core out from inside the dam. Hidden beneath your feet, an underground tunnel (pipe) is eating its way backward toward the reservoir. Once that tunnel breaks through to the river side, pressurized reservoir water enlarges the hole in seconds, collapsing the top of the levee and unleashing a full-depth breach. Never walk onto a slumping or boiling levee, never try to plug a gushing muddy boil by throwing dirt into the hole, and call 911 / 112 / 999 while evacuating.

Survival physics when caught in the open or inside a vehicle¶

If you are caught in a valley when a dam breach or GLOF wave arrives and cannot reach the upper valley wall in time:

1. Always choose a steep natural hillside over ANY man-made structure: Even a 10-meter (33-foot) natural rock outcrop or dirt hillside anchored into the earth cannot be knocked down by a flood wave, whereas a 3-story brick building sitting in the middle of the valley floor can have its foundations undermined and collapse into the torrent.
2. If no hillside exists (flat floodplain), choose the right vertical evacuation building:
3. Abandon: Single-story homes, wood-frame houses, mobile homes/caravans, unreinforced brick buildings, metal warehouses, and vehicles.
4. Climb: A multi-story (3+ stories) reinforced poured-concrete or structural steel building (such as a hospital, university building, multi-story concrete parking garage, or modern hotel). Move to the 3^rd floor or higher and stay on the downstream side of the building interior away from windows facing the oncoming wave impact.
5. Never trap yourself inside a closed attic without an axe or roof hatch: If rising water forces you up the stairs of a building, never climb into an enclosed attic unless there is a walk-out window, a roof hatch, or you carry a heavy axe/sledgehammer capable of smashing through wooden roof sheathing and shingles. Hundreds of flood victims have drowned trapped against the underside of their own roof peak.
6. If swept into the water: Do not try to swim against the current or stand up in fast-moving water (putting your feet down in rocky floodwater traps your foot between cobbles while the current pushes your torso forward, folding you underwater: foot entrapment). Roll onto your back with your feet pointing downstream and held high at the surface to fend off boulders and floating timber, angle your body at a 45-degree ferry angle toward the nearest shoreline eddy or hillside, and scramble up the bank the instant you hit slower water on the inside bend of the valley.

Pre-planning: How to read your local Dam Inundation Map and GLOF Hazard Map¶

If you live, work, or camp in a river valley, coastal polder, or alpine canyon, take 10 minutes before an emergency to check your exposure:

1. Look up the National Dam Inventory and Inundation Maps:
2. United States: Search the US Army Corps of Engineers National Inventory of Dams (NID) (nid.sec.usace.army.mil) or your state dam safety portal (such as California DWR Dam Breach Inundation Maps) to view the exact street-by-street Sunny-Day Breach and Flood-Induced Breach inundation polygons and wave arrival times (e.g., "15-minute wave arrival contour" vs. "2-hour arrival contour").
3. United Kingdom & Europe: Check the UK Environment Agency ** Reservoir Flood Maps** (check-for-flooding.service.gov.uk) or national civil protection hydrological portals.
4. Alpine & Mountain Regions (Himalayas, Andes, Alps, Rockies, Alaska, Iceland, New Zealand): Check regional geological survey Glacial Lake Inventory and GLOF Hazard Maps before trekking or camping in glacial river valleys; never pitch a tent on a low gravel bar or river terrace inside a glacial valley, even on a sunny summer night.
5. Identify Two Perpendicular Foot-Evacuation Trails: Walk out your front door and identify the fastest route on foot (via a pedestrian staircase, hillside trail, or steep cross-street) that climbs perpendicularly away from the river to an elevation above the mapped inundation boundary. Practice walking it with your family so everyone can find it in total darkness during a blackout.

Preguntas frecuentes¶

Fontes comprobadas¶

• Federal Emergency Management Agency (FEMA, United States) and United States Army Corps of Engineers (USACE): Federal Guidelines for Dam Safety: Emergency Action Planning for Dam Owners (FEMA P-64), National Inventory of Dams (NID), and Levee Seepage and Sand Boil Field Manual.
• United States Geological Survey (USGS) and National Oceanic and Atmospheric Administration (NOAA / NWS, United States): Debris-Flow, Landslide-Dam Outburst, and Dam-Break Flood Wave Hydraulics and Warning Protocols.
• International Centre for Integrated Mountain Development (ICIMOD), United Nations Office for Disaster Risk Reduction (UNDRR), and World Meteorological Organization (WMO): Early Warning Systems and Evacuation Guidelines for Glacial Lake Outburst Floods (GLOFs) in the Hindu Kush Himalaya, Andes, and European Alps.
• International Commission on Large Dams (ICOLD) and United Nations Environment Programme (UNEP): Global Industry Standard on Tailings Management (GISTM) and emergency evacuation lessons from catastrophic tailings dam liquefaction failures.
• Environment Agency (United Kingdom): Reservoir Flood Maps and Community Emergency Plan Guidance for Dam Inundation Zones.

Guías relacionadas¶

• Flash floods: immediate high-ground survival
• Floods: preparation, evacuation, and safe return
• Landslides, mudslides, and debris flows
• Earthquakes: Drop, Cover, and Hold On
• Car in water: sinking vehicle escape