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Urban flooding in a street in Morpeth, England, 2008

A flood is an overflow of water (or rarely other fluids) that submerges land that is usually dry.[1] In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant concern in agriculture, civil engineering and public health. Human changes to the environment often increase the intensity and frequency of flooding. Examples for human changes are land use changes such as deforestation and removal of wetlands, changes in waterway course or flood controls such as with levees. Global environmental issues also influence causes of floods, namely climate change which causes an intensification of the water cycle and sea level rise.[2]: 1517  For example, climate change makes extreme weather events more frequent and stronger.[3] This leads to more intense floods and increased flood risk.[4][5]

Natural types of floods include river flooding, groundwater flooding coastal flooding and urban flooding sometimes known as flash flooding. Tidal flooding may include elements of both river and coastal flooding processes in estuary areas. There is also the intentional flooding of land that would otherwise remain dry. This may take place for agricultural, military, or river-management purposes. For example, agricultural flooding may occur in preparing paddy fields for the growing of semi-aquatic rice in many countries.

Flooding may occur as an overflow of water from water bodies, such as a river, lake, sea or ocean. In these cases, the water overtops or breaks levees, resulting in some of that water escaping its usual boundaries.[6] Flooding may also occur due to an accumulation of rainwater on saturated ground. This is called an areal flood. The size of a lake or other body of water naturally varies with seasonal changes in precipitation and snow melt. Those changes in size are however not considered a flood unless they flood property or drown domestic animals.

Floods can also occur in rivers when the flow rate exceeds the capacity of the river channel, particularly at bends or meanders in the waterway. Floods often cause damage to homes and businesses if these buildings are in the natural flood plains of rivers. People could avoid riverine flood damage by moving away from rivers. However, people in many countries have traditionally lived and worked by rivers because the land is usually flat and fertile. Also, the rivers provide easy travel and access to commerce and industry.

Flooding can damage property and also lead to secondary impacts. These include in the short term an increased spread of waterborne diseases and vector-bourne diseases, for example those diseases transmitted by mosquitos. Flooding can also lead to long-term displacement of residents.[7] Floods are an area of study of hydrology and hydraulic engineering.

A large amount of the world's population lives in close proximity to major coastlines,[8] while many major cities and agricultural areas are located near floodplains.[9] There is significant risk for increased coastal and fluvial flooding due to changing climatic conditions.[10]

Types

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View of flooded New Orleans in the aftermath of Hurricane Katrina
Flooding of a creek due to heavy monsoonal rain and high tide in Darwin, Northern Territory, Australia
Flood in Jeddah, covering the King Abdullah Street in Saudi Arabia
Overland flooding near Georgetown, Minnesota, in the Red River Valley of the North

Areal flooding

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In spring time, the floods are quite typical in Ostrobothnia, a flat-lying area in Finland. A flood-surrounded house in Ilmajoki, South Ostrobothnia.

Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can either infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths. Surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, or roofs. Areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience areal flooding during periods when precipitation exceeds evaporation.[11]

River flooding

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Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the world's largest rivers. When overland flow occurs on tilled fields, it can result in a muddy flood where sediments are picked up by run off and carried as suspended matter or bed load. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, or beaver dams.

Slow-rising floods most commonly occur in large rivers with large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, or tropical cyclones. However, large rivers may have rapid flooding events in areas with dry climates, since they may have large basins but small river channels, and rainfall can be very intense in smaller areas of those basins.

In extremely flat areas, such as the Red River Valley of the North in Minnesota, North Dakota, and Manitoba, a type of hybrid river/areal flooding can occur, known locally as "overland flooding". This is different from "overland flow" defined as "surface runoff". The Red River Valley is a former glacial lakebed, created by Lake Agassiz, and over a length of 550 mi (890 km), the river course drops only 236 ft (72 m), for an average slope of about 5 inches per mile (or 8.2 cm per kilometer).[12] In this very large area, spring snowmelt happens at different rates in different places, and if winter snowfall was heavy, a fast snowmelt can push water out of the banks of a tributary river so that it moves overland, to a point further downstream in the river or completely to another streambed. Overland flooding can be devastating because it is unpredictable, it can occur very suddenly with surprising speed, and in such flat land it can run for miles. It is these qualities that set it apart from simple "overland flow".

Rapid flooding events, including flash floods, more often occur on smaller rivers, rivers with steep valleys, rivers that flow for much of their length over impermeable terrain, or normally-dry channels. The cause may be localized convective precipitation (intense thunderstorms) or sudden release from an upstream impoundment created behind a dam, landslide, or glacier. In one instance, a flash flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Without any observed rainfall, the flow rate increased from about 50 to 1,500 cubic feet per second (1.4 to 42 m3/s) in just one minute.[13] Two larger floods occurred at the same site within a week, but no one was at the waterfall on those days. The deadly flood resulted from a thunderstorm over part of the drainage basin, where steep, bare rock slopes are common and the thin soil was already saturated.

Flash floods are the most common flood type in normally-dry channels in arid zones, known as arroyos in the southwest United States and many other names elsewhere. In that setting, the first flood water to arrive is depleted as it wets the sandy stream bed. The leading edge of the flood thus advances more slowly than later and higher flows. As a result, the rising limb of the hydrograph becomes ever quicker as the flood moves downstream, until the flow rate is so great that the depletion by wetting soil becomes insignificant.

Coastal flooding

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Main article: Coastal flooding

Coastal areas may be flooded by storm surges combining with high tides and large wave events at sea, resulting in waves over-topping flood defenses or in severe cases by tsunami or tropical cyclones. A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. A storm surge is "an additional rise of water generated by a storm, over and above the predicted astronomical tides".[14] Due to the effects of climate change (e.g. sea level rise and an increase in extreme weather events) and an increase in the population living in coastal areas, the damage caused by coastal flood events has intensified and more people are being affected.[15]

Flooding in estuaries is commonly caused by a combination of storm surges caused by winds and low barometric pressure and large waves meeting high upstream river flows.

Urban flooding

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This section is an excerpt from Urban flooding.[edit]
Flooding in Porto Alegre of the Lagoa dos Patos in Brazil during May 2024
Urban flooding is the inundation of land or property in cities or other built environment, caused by rainfall or coastal storm surges overwhelming the capacity of drainage systems, such as storm sewers. Urban flooding can occur regardless of whether or not affected communities are located within designated floodplains or near any body of water.[16] It is triggered for example by an overflow of rivers and lakes, flash flooding or snowmelt. During the flood, stormwater or water released from damaged water mains may accumulate on property and in public rights-of-way. It can seep through building walls and floors, or backup into buildings through sewer pipes, cellars, toilets and sinks. There are several types of urban flooding, each with a different cause. City planners distinguish pluvial flooding (flooding caused by heavy rain), fluvial flooding (caused by a nearby river overflowing its banks), or coastal flooding (often caused by storm surges). Urban flooding is a hazard to both the population and infrastructure. Some well known disaster events include the inundations of Nîmes (France) in 1998 and Vaison-la-Romaine (France) in 1992, the flooding of New Orleans (United States) in 2005, and the flooding in Rockhampton, Bundaberg, Brisbane during the 2010–2011 Queensland floods in Australia, the 2022 eastern Australia floods, and more recently the 2024 Rio Grande do Sul floods in Brazil.

Intentional floods

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The intentional flooding of land that would otherwise remain dry may take place for agricultural, military or river-management purposes. This is a form of hydraulic engineering. Agricultural flooding may occur in preparing paddy fields for the growing of semi-aquatic rice in many countries.

Chinese Kuomintang soldiers during the 1938 Yellow River flood

Flooding for river management may occur in the form of diverting flood waters in a river at flood stage upstream from areas that are considered more valuable than the areas that are sacrificed in this way. This may be done ad hoc,[17] or permanently, as in the so-called overlaten (literally "let-overs"), an intentionally lowered segment in Dutch riparian levees, like the Beerse Overlaat in the left levee of the Meuse between the villages of Gassel and Linden, North Brabant.

Military inundation creates an obstacle in the field that is intended to impede the movement of the enemy.[18] This may be done both for offensive and defensive purposes. Furthermore, in so far as the methods used are a form of hydraulic engineering, it may be useful to differentiate between controlled inundations and uncontrolled ones. Examples for controlled inundations include those in the Netherlands under the Dutch Republic and its successor states in that area[19][20] and exemplified in the two Hollandic Water Lines, the Stelling van Amsterdam, the Frisian Water Line, the IJssel Line, the Peel-Raam Line, and the Grebbe line in that country.

To count as controlled, a military inundation has to take the interests of the civilian population into account, by allowing them a timely evacuation, by making the inundation reversible, and by making an attempt to minimize the adverse ecological impact of the inundation. That impact may also be adverse in a hydrogeological sense if the inundation lasts a long time.[21]

Examples for uncontrolled inundations are the second Siege of Leiden[22] during the first part of the Eighty Years' War, the flooding of the Yser plain during the First World War,[23] and the Inundation of Walcheren, and the Inundation of the Wieringermeer during the Second World War).

Causes

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Flood due to Cyclone Hudhud in Visakhapatnam, India
See also: Coastal flooding § Causes

Floods are caused by many factors or a combination of any of these generally prolonged heavy rainfall (locally concentrated or throughout a catchment area), highly accelerated snowmelt, severe winds over water, unusual high tides, tsunamis, or failure of dams, levees, retention ponds, or other structures that retained the water. Flooding can be exacerbated by increased amounts of impervious surface or by other natural hazards such as wildfires, which reduce the supply of vegetation that can absorb rainfall.

During times of rain, some of the water is retained in ponds or soil, some is absorbed by grass and vegetation, some evaporates, and the rest travels over the land as surface runoff. Floods occur when ponds, lakes, riverbeds, soil, and vegetation cannot absorb all the water.

This has been exacerbated by human activities such as draining wetlands that naturally store large amounts of water and building paved surfaces that do not absorb any water.[24] Water then runs off the land in quantities that cannot be carried within stream channels or retained in natural ponds, lakes, and human-made reservoirs. About 30 percent of all precipitation becomes runoff[25] and that amount might be increased by water from melting snow.

Upslope factors

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Flash flood in Ein Avdat, Negev, Israel

River flooding is often caused by heavy rain, sometimes increased by melting snow. A flood that rises rapidly, with little or no warning, is called a flash flood. Flash floods usually result from intense rainfall over a relatively small area, or if the area was already saturated from previous precipitation.

The amount, location, and timing of water reaching a drainage channel from natural precipitation and controlled or uncontrolled reservoir releases determines the flow at downstream locations. Some precipitation evaporates, some slowly percolates through soil, some may be temporarily sequestered as snow or ice, and some may produce rapid runoff from surfaces including rock, pavement, roofs, and saturated or frozen ground. The fraction of incident precipitation promptly reaching a drainage channel has been observed from nil for light rain on dry, level ground to as high as 170 percent for warm rain on accumulated snow.[26]

Most precipitation records are based on a measured depth of water received within a fixed time interval. Frequency of a precipitation threshold of interest may be determined from the number of measurements exceeding that threshold value within the total time period for which observations are available. Individual data points are converted to intensity by dividing each measured depth by the period of time between observations. This intensity will be less than the actual peak intensity if the duration of the rainfall event was less than the fixed time interval for which measurements are reported. Convective precipitation events (thunderstorms) tend to produce shorter duration storm events than orographic precipitation. Duration, intensity, and frequency of rainfall events are important to flood prediction. Short duration precipitation is more significant to flooding within small drainage basins.[27]

The most important upslope factor in determining flood magnitude is the land area of the watershed upstream of the area of interest. Rainfall intensity is the second most important factor for watersheds of less than approximately 30 square miles or 80 square kilometres. The main channel slope is the second most important factor for larger watersheds. Channel slope and rainfall intensity become the third most important factors for small and large watersheds, respectively.[28]

Time of Concentration is the time required for runoff from the most distant point of the upstream drainage area to reach the point of the drainage channel controlling flooding of the area of interest. The time of concentration defines the critical duration of peak rainfall for the area of interest.[29] The critical duration of intense rainfall might be only a few minutes for roof and parking lot drainage structures, while cumulative rainfall over several days would be critical for river basins.

Downslope factors

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Water flowing downhill ultimately encounters downstream conditions slowing movement. The final limitation in coastal flooding lands is often the ocean or some coastal flooding bars which form natural lakes. In flooding low lands, elevation changes such as tidal fluctuations are significant determinants of coastal and estuarine flooding. Less predictable events like tsunamis and storm surges may also cause elevation changes in large bodies of water. Elevation of flowing water is controlled by the geometry of the flow channel and, especially, by depth of channel, speed of flow and amount of sediments in it[28] Flow channel restrictions like bridges and canyons tend to control water elevation above the restriction. The actual control point for any given reach of the drainage may change with changing water elevation, so a closer point may control for lower water levels until a more distant point controls at higher water levels.

Effective flood channel geometry may be changed by growth of vegetation, accumulation of ice or debris, or construction of bridges, buildings, or levees within the flood channel.

Periodic floods occur on many rivers, forming a surrounding region known as the flood plain. Even when rainfall is relatively light, the shorelines of lakes and bays can be flooded by severe winds—such as during hurricanes—that blow water into the shore areas.

Climate change

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High tide flooding is increasing due to sea level rise, land subsidence, and the loss of natural barriers.[30]
Long-term sea level rise occurs in addition to intermittent tidal flooding. NOAA predicts different levels of sea level rise for coastlines within a single country.[31]
This section is an excerpt from Effects of climate change § Floods.[edit]
Due to an increase in heavy rainfall events, floods are likely to become more severe when they do occur.[32]: 1155  The interactions between rainfall and flooding are complex. There are some regions in which flooding is expected to become rarer. This depends on several factors. These include changes in rain and snowmelt, but also soil moisture.[32]: 1156  Climate change leaves soils drier in some areas, so they may absorb rainfall more quickly. This leads to less flooding. Dry soils can also become harder. In this case heavy rainfall runs off into rivers and lakes. This increases risks of flooding.[32]: 1155 

Coincidence

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Extreme flood events often result from coincidence such as unusually intense, warm rainfall melting heavy snow pack, producing channel obstructions from floating ice, and releasing small impoundments like beaver dams.[33] Coincident events may cause extensive flooding to be more frequent than anticipated from simplistic statistical prediction models considering only precipitation runoff flowing within unobstructed drainage channels.[34] Debris modification of channel geometry is common when heavy flows move uprooted woody vegetation and flood-damaged structures and vehicles, including boats and railway equipment. Recent field measurements during the 2010–11 Queensland floods showed that any criterion solely based upon the flow velocity, water depth or specific momentum cannot account for the hazards caused by velocity and water depth fluctuations.[35] These considerations ignore further the risks associated with large debris entrained by the flow motion.[36]

Negative impacts

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Flooded walnut orchards in Butte County after several atmospheric rivers hit California in early 2023

Floods can be a huge destructive power. When water flows, it has the ability to demolish all kinds of buildings and objects, such as bridges, structures, houses, trees, and cars. Economical, social and natural environmental damages are common factors that are impacted by flooding events and the impacts that flooding has on these areas can be catastrophic.[37]

Impacts on infrastructure and societies

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There have been numerous flood incidents around the world which have caused devastating damage to infrastructure, the natural environment and human life.[37]

Floods can have devastating impacts to human societies. Flooding events worldwide are increasing in frequency and severity, leading to increasing costs to societies.[37]

Catastrophic riverine flooding can result from major infrastructure failures, often the collapse of a dam. It can also be caused by drainage channel modification from a landslide, earthquake or volcanic eruption. Examples include outburst floods and lahars. Tsunamis can cause catastrophic coastal flooding, most commonly resulting from undersea earthquakes.

Economic impacts

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The primary effects of flooding include loss of life and damage to buildings and other structures, including bridges, sewerage systems, roadways, and canals. The economic impacts caused by flooding can be severe.[9]

Every year flooding causes countries billions of dollars' worth of damage that threatens the livelihood of individuals.[38] As a result, there is also significant socio-economic threats to vulnerable populations around the world from flooding.[38] For example, in Bangladesh in 2007, a flood was responsible for the destruction of more than one million houses. And yearly in the United States, floods cause over $7 billion in damage.[39]

Mud was deposited in this house by flooding in the 2018 Kerala floods in India. Flooding not only creates water damage, but can also deposit large amounts of sediment.

Flood waters typically inundate farm land, making the land unworkable and preventing crops from being planted or harvested, which can lead to shortages of food both for humans and farm animals. Entire harvests for a country can be lost in extreme flood circumstances. Some tree species may not survive prolonged flooding of their root systems.[40]

Flooding in areas where people live also has significant economic implications for affected neighborhoods. In the United States, industry experts estimate that wet basements can lower property values by 10–25 percent and are cited among the top reasons for not purchasing a home.[41] According to the U.S. Federal Emergency Management Agency (FEMA), almost 40 percent of small businesses never reopen their doors following a flooding disaster.[42] In the United States, insurance is available against flood damage to both homes and businesses.[43]

Economic hardship due to a temporary decline in tourism, rebuilding costs, or food shortages leading to price increases is a common after-effect of severe flooding. The impact on those affected may cause psychological damage to those affected, in particular where deaths, serious injuries and loss of property occur.

Health impacts

[edit]
Coastal flooding in a community in Florida, United States
Flooding after 1991 Bangladesh cyclone, which killed around 140,000 people

Fatalities connected directly to floods are usually caused by drowning; the waters in a flood are very deep and have strong currents.[44] Deaths do not just occur from drowning, deaths are connected with dehydration, heat stroke, heart attack and any other illness that needs medical supplies that cannot be delivered.[44]

Injuries can lead to an excessive amount of morbidity when a flood occurs. Injuries do not just affect those who were directly in the flood: rescue teams and even people delivering supplies can sustain an injury. Injuries can occur before, during and after the flood.[44] During floods accidents occur with falling debris or any of the many fast moving objects in the water. After the flood rescue attempts are when large numbers injuries can occur.[44]

Communicable diseases are increased due to many pathogens and bacteria that are being transported by the water. There are many waterborne diseases such as cholera, hepatitis A, hepatitis E and diarrheal diseases, to mention a few. Gastrointestinal disease and diarrheal diseases are very common due to a lack of clean water during a flood. Clean water supplies are often contaminated when flooding occurs. Hepatitis A and E are common because of the lack of sanitation in the water and in living quarters, depending on where the flood is and how prepared the community is for a flood.[44]

When floods hit, people can lose nearly all their crops, livestock, and food reserves and face starvation.[45]

Floods also frequently damage power transmission and sometimes power generation, which then has knock-on effects caused by the loss of power. This includes loss of drinking water treatment and water supply, which may result in loss of drinking water or severe water contamination. It may also cause the loss of sewage disposal facilities. Lack of clean water combined with human sewage in the flood waters raises the risk of waterborne diseases, which can include typhoid, giardia, cryptosporidium, cholera and many other diseases depending upon the location of the flood.[Merge this list with previous list]

Damage to roads and transport infrastructure may make it difficult to mobilize aid to those affected or to provide emergency health treatment.

Flooding can cause chronically wet houses, leading to the growth of indoor mold and resulting in adverse health effects, particularly respiratory symptoms.[46] Respiratory diseases are common after the disaster has occurred. This depends on the amount of water damage and mold that grows after an incident. Research suggests that there will be an increase of 30–50% in adverse respiratory health outcomes caused by dampness and mold exposure for those living in coastal and wetland areas. Fungal contamination in homes is associated with increased allergic rhinitis and asthma.[47] Vector-borne diseases also increase, due to the residual still water after the floods have settled. The diseases that are vector borne are malaria, dengue, West Nile, and yellow fever.[44] Floods may have a huge impact on victims' psychosocial integrity. People suffer from a wide variety of losses and stress. One of the most treated illnesses in long-term health problems are depression caused by the flood and all the tragedy that flows with one.[44]

Loss of life

[edit]
Main article: List of deadliest floods

Below is a list of the deadliest floods worldwide, showing events with death tolls at or above 100,000 individuals.

Death toll Event Location Year
2,500,000–3,700,000[48] 1931 China floods China 1931
900,000–2,000,000 1887 Yellow River flood China 1887
500,000–700,000 1938 Yellow River flood China 1938
231,000 Banqiao Dam failure, result of Typhoon Nina. Approximately 86,000 people died from flooding and another 145,000 died from subsequent disease. China 1975
230,000 2004 Indian Ocean tsunami Indonesia 2004
145,000 1935 Yangtze river flood China 1935
100,000+ St. Felix's flood, storm surge Netherlands 1530
100,000 Hanoi and Red River Delta flood North Vietnam 1971
100,000 1911 Yangtze river flood China 1911

Positive impacts (benefits)

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Floods (in particular more frequent or smaller floods) can also bring many benefits, such as recharging ground water, making soil more fertile and increasing nutrients in some soils. For this reason, periodic flooding was essential to the well-being of ancient peoples along the Tigris-Euphrates Rivers, the Nile River, the Indus River, the Ganges and the Yellow River among others.

Flood waters provide much needed water resources in arid and semi-arid regions where precipitation can be very unevenly distributed throughout the year and kills pests in the farming land. Freshwater floods particularly play an important role in maintaining ecosystems in river corridors and are a key factor in maintaining floodplain biodiversity.[49] Flooding can spread nutrients to lakes and rivers, which can lead to increased biomass and improved fisheries for a few years.

For some fish species, an inundated floodplain may form a highly suitable location for spawning, with few predators and enhanced levels of nutrients or food.[50] Fish such as the weather fish use floods to reach new habitats. Bird populations may also profit from the boost in food production caused by flooding.[51]

The viability of hydropower, a renewable source of energy, is also higher in flood-prone regions.

Protections against floods and associated hazards

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Flood management

[edit]
A weir was built on the Humber River (Ontario) to prevent a recurrence of a catastrophic flood.
This section is an excerpt from Flood management.[edit]

Flood management or flood control are methods used to reduce or prevent the detrimental effects of flood waters. Flooding can be caused by a mix of both natural processes, such as extreme weather upstream, and human changes to waterbodies and runoff. Flood management methods can be either of the structural type (i.e. flood control) and of the non-structural type. Structural methods hold back floodwaters physically, while non-structural methods do not. Building hard infrastructure to prevent flooding, such as flood walls, is effective at managing flooding. However, it is best practice within landscape engineering to rely more on soft infrastructure and natural systems, such as marshes and flood plains, for handling the increase in water.

Flood management can include flood risk management, which focuses on measures to reduce risk, vulnerability and exposure to flood disasters and providing risk analysis through, for example, flood risk assessment.[52] Flood mitigation is a related but separate concept describing a broader set of strategies taken to reduce flood risk and potential impact while improving resilience against flood events.

As climate change has led to increased flood risk an intensity, flood management is an important part of climate change adaptation and climate resilience.[53][54] For example, to prevent or manage coastal flooding, coastal management practices have to handle natural processes like tides but also sea level rise due to climate change. The prevention and mitigation of flooding can be studied on three levels: on individual properties, small communities, and whole towns or cities.

Flood management examples

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In many countries around the world, waterways prone to floods are often carefully managed. Defenses such as detention basins, levees,[55] bunds, reservoirs, and weirs are used to prevent waterways from overflowing their banks. When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are often used to try to stem flooding. Coastal flooding has been addressed in portions of Europe and the Americas with coastal defenses, such as sea walls, beach nourishment, and barrier islands.

In the riparian zone near rivers and streams, erosion control measures can be taken to try to slow down or reverse the natural forces that cause many waterways to meander over long periods of time. Flood controls, such as dams, can be built and maintained over time to try to reduce the occurrence and severity of floods as well. In the United States, the U.S. Army Corps of Engineers maintains a network of such flood control dams.

In areas prone to urban flooding, one solution is the repair and expansion of human-made sewer systems and stormwater infrastructure. Another strategy is to reduce impervious surfaces in streets, parking lots and buildings through natural drainage channels, porous paving, and wetlands (collectively known as green infrastructure or sustainable urban drainage systems (SUDS)). Areas identified as flood-prone can be converted into parks and playgrounds that can tolerate occasional flooding. Ordinances can be adopted to require developers to retain stormwater on site and require buildings to be elevated, protected by floodwalls and levees, or designed to withstand temporary inundation. Property owners can also invest in solutions themselves, such as re-landscaping their property to take the flow of water away from their building and installing rain barrels, sump pumps, and check valves.

Flood safety planning

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Aftermath of flooding in Colorado, 2013
Flood rescue in Nangarhar, Afghanistan in 2010
Flash flooding caused by heavy rain falling in a short amount of time

In the United States, the National Weather Service gives out the advice "Turn Around, Don't Drown" for floods; that is, it recommends that people get out of the area of a flood, rather than trying to cross it. At the most basic level, the best defense against floods is to seek higher ground for high-value uses while balancing the foreseeable risks with the benefits of occupying flood hazard zones.[56]: 22–23  Critical community-safety facilities, such as hospitals, emergency-operations centers, and police, fire, and rescue services, should be built in areas least at risk of flooding. Structures, such as bridges, that must unavoidably be in flood hazard areas should be designed to withstand flooding. Areas most at risk for flooding could be put to valuable uses that could be abandoned temporarily as people retreat to safer areas when a flood is imminent.

Planning for flood safety involves many aspects of analysis and engineering, including:

  • observation of previous and present flood heights and inundated areas,
  • statistical, hydrologic, and hydraulic model analyses,
  • mapping inundated areas and flood heights for future flood scenarios,
  • long-term land use planning and regulation,
  • engineering design and construction of structures to control or withstand flooding,
  • intermediate-term monitoring, forecasting, and emergency-response planning, and
  • short-term monitoring, warning, and response operations.

Each topic presents distinct yet related questions with varying scope and scale in time, space, and the people involved. Attempts to understand and manage the mechanisms at work in floodplains have been made for at least six millennia.[57][page needed]

In the United States, the Association of State Floodplain Managers works to promote education, policies, and activities that mitigate current and future losses, costs, and human suffering caused by flooding and to protect the natural and beneficial functions of floodplains – all without causing adverse impacts.[58] A portfolio of best practice examples for disaster mitigation in the United States is available from the Federal Emergency Management Agency.[59]

Flood clean-up safety

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Clean-up activities following floods often pose hazards to workers and volunteers involved in the effort. Potential dangers include electrical hazards, carbon monoxide exposure, musculoskeletal hazards, heat or cold stress, motor vehicle-related dangers, fire, drowning, and exposure to hazardous materials. Because flooded disaster sites are unstable, clean-up workers might encounter sharp jagged debris, biological hazards in the flood water, exposed electrical lines, blood or other body fluids, and animal and human remains. In planning for and reacting to flood disasters, managers provide workers with hard hats, goggles, heavy work gloves, life jackets, and watertight boots with steel toes and insoles.[60]

Flood predictions

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Main article: Flood prediction
See also: Urban flooding § Modeling
Flooding near Key West, Florida, United States from Hurricane Wilma's storm surge in October 2005

A series of annual maximum flow rates in a stream reach can be analyzed statistically to estimate the 100-year flood and floods of other recurrence intervals there. Similar estimates from many sites in a hydrologically similar region can be related to measurable characteristics of each drainage basin to allow indirect estimation of flood recurrence intervals for stream reaches without sufficient data for direct analysis.

Physical process models of channel reaches are generally well understood and will calculate the depth and area of inundation for given channel conditions and a specified flow rate, such as for use in floodplain mapping and flood insurance. Conversely, given the observed inundation area of a recent flood and the channel conditions, a model can calculate the flow rate. Applied to various potential channel configurations and flow rates, a reach model can contribute to selecting an optimum design for a modified channel. Various reach models are available as of 2015, either 1D models (flood levels measured in the channel) or 2D models (variable flood depths measured across the extent of a floodplain). HEC-RAS,[61] the Hydraulic Engineering Center model, is among the most popular software, if only because it is available free of charge. Other models such as TUFLOW[62] combine 1D and 2D components to derive flood depths across both river channels and the entire floodplain.

Physical process models of complete drainage basins are even more complex. Although many processes are well understood at a point or for a small area, others are poorly understood at all scales, and process interactions under normal or extreme climatic conditions may be unknown. Basin models typically combine land-surface process components (to estimate how much rainfall or snowmelt reaches a channel) with a series of reach models. For example, a basin model can calculate the runoff hydrograph that might result from a 100-year storm, although the recurrence interval of a storm is rarely equal to that of the associated flood. Basin models are commonly used in flood forecasting and warning, as well as in analysis of the effects of land use change and climate change.

In the United States, an integrated approach to real-time hydrologic computer modelling uses observed data from the U.S. Geological Survey (USGS),[63] various cooperative observing networks,[64] various automated weather sensors, the NOAA National Operational Hydrologic Remote Sensing Center (NOHRSC),[65] various hydroelectric companies, etc. combined with quantitative precipitation forecasts (QPF) of expected rainfall and/or snow melt to generate daily or as-needed hydrologic forecasts.[66] The NWS also cooperates with Environment Canada on hydrologic forecasts that affect both the US and Canada, like in the area of the Saint Lawrence Seaway.

The Global Flood Monitoring System, "GFMS", a computer tool which maps flood conditions worldwide, is available online.[67] Users anywhere in the world can use GFMS to determine when floods may occur in their area. GFMS uses precipitation data from NASA's Earth observing satellites and the Global Precipitation Measurement satellite, "GPM". Rainfall data from GPM is combined with a land surface model that incorporates vegetation cover, soil type, and terrain to determine how much water is soaking into the ground, and how much water is flowing into streamflow.

Users can view statistics for rainfall, streamflow, water depth, and flooding every 3 hours, at each 12-kilometer gridpoint on a global map. Forecasts for these parameters are 5 days into the future. Users can zoom in to see inundation maps (areas estimated to be covered with water) in 1-kilometer resolution.[68]

Flooding in a street of Natal, Rio Grande do Norte, Brazil in April 2013

Anticipating floods before they occur allows for precautions to be taken and people to be warned[69] so that they can be prepared in advance for flooding conditions. For example, farmers can remove animals from low-lying areas and utility services can put in place emergency provisions to re-route services if needed. Emergency services can also make provisions to have enough resources available ahead of time to respond to emergencies as they occur. People can evacuate areas to be flooded.

In order to make the most accurate flood forecasts for waterways, it is best to have a long time-series of historical data that relates stream flows to measured past rainfall events.[70] Coupling this historical information with real-time knowledge about volumetric capacity in catchment areas, such as spare capacity in reservoirs, ground-water levels, and the degree of saturation of area aquifers is also needed in order to make the most accurate flood forecasts.

Radar estimates of rainfall and general weather forecasting techniques are also important components of good flood forecasting. In areas where good quality data is available, the intensity and height of a flood can be predicted with fairly good accuracy and plenty of lead time. The output of a flood forecast is typically a maximum expected water level and the likely time of its arrival at key locations along a waterway,[66] and it also may allow for the computation of the likely statistical return period of a flood. In many developed countries, urban areas at risk of flooding are protected against a 100-year flood – that is a flood that has a probability of around 63% (i.e. 1 − 0.99100, or roughly 1 − 1/e) of occurring in any 100-year period of time.

According to the U.S. National Weather Service (NWS) Northeast River Forecast Center (RFC) in Taunton, Massachusetts, a rule of thumb for flood forecasting in urban areas is that it takes at least 1 inch (25 mm) of rainfall in around an hour's time in order to start significant ponding of water on impermeable surfaces. Many NWS RFCs routinely issue Flash Flood Guidance and Headwater Guidance, which indicate the general amount of rainfall that would need to fall in a short period of time in order to cause flash flooding or flooding on larger water basins.[71]

Flood risk assessment

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Main article: Flood risk assessment

Flood risks can be defined as the risk that floods pose to individuals, property and the natural landscape based on specific hazards and vulnerability. The extent of flood risks can impact the types of mitigation strategies required and implemented.[72]

A large amount of the world's population lives in close proximity to major coastlines,[8] while many major cities and agricultural areas are located near floodplains.[9] There is significant risk for increased coastal and fluvial flooding due to changing climatic conditions.[10]

Examples by country or region

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Society and culture

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People seeking refuge from flood in Java, c. 1865–1876

Myths and religion

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"The Deluge", frontispiece to Gustave Doré's illustrated edition of the Bible
This section is an excerpt from Flood myth.[edit]

A flood myth or a deluge myth is a myth in which a great flood, usually sent by a deity or deities, destroys civilization, often in an act of divine retribution. Parallels are often drawn between the flood waters of these myths and the primeval cosmic ocean which appear in certain creation myths, as the flood waters are described as a measure for the cleansing of humanity, for example in preparation for rebirth. Most flood myths also contain a culture hero, who "represents the human craving for life".[73]

The oldest known narrative of a divinely inititated flood originates from the Sumerian culture in Mesopotamia, among others expressed in the Akkadian Atra-Hasis epic, which dates to the 18th century BCE. Comparable flood narratives appear in many other cultures, including the biblical Genesis flood narrative, manvantara-sandhya in Hinduism, Deucalion in Greek mythology, and in indigenous North American cultures.

Etymology

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The word "flood" comes from the Old English flōd, a word common to Germanic languages (compare German Flut, Dutch vloed from the same root as is seen in flow, float; also compare with Latin fluctus, flumen), meaning "a flowing of water, tide, an overflowing of land by water, a deluge, Noah's Flood; mass of water, river, sea, wave".[74][75] The Old English word flōd comes from the Proto-Germanic floduz (Old Frisian flod, Old Norse floð, Middle Dutch vloet, Dutch vloed, German Flut, and Gothic flodus derives from floduz).[74]

See also

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  • Disaster response – Second phase of the disaster management cycle
  • Diversion dam – Dam that diverts some flow of a river
  • Emergency management – Dealing with all humanitarian aspects of emergencies
  • Flood alert – Weather warning indicating areal flooding has been observed or is imminent
  • Mudflow – Form of mass wasting

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Flood

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from Grokipedia
A flood is an overflowing of onto land that is normally dry, typically resulting from excessive , rapid , or overflow from bodies such as rivers and oceans. Floods are among the most common and widespread natural hazards, driven primarily by meteorological events like intense rainfall or storm surges, as well as hydrological factors including saturated soils and inadequate drainage. They occur in various forms, including flash floods from sudden heavy downpours, riverine floods from prolonged or extreme upstream , and coastal floods from tidal surges or anomalies. Globally, floods contribute significantly to water-related disasters, which have resulted in over 300,000 fatalities and approximately 1.7 trillion USD in economic damages since systematic records began. Empirical data indicate that fluvial and flooding predominate in many regions, with human modifications to landscapes—such as and —exacerbating runoff and vulnerability in some cases, though natural variability in patterns remains the primary causal driver. Notable historical events, like the or in 2005, underscore floods' capacity for widespread destruction, including loss of life, damage, and agricultural disruption, prompting advancements in forecasting, systems, and early warning mechanisms.

Definition and Fundamentals

Hydrological and Physical Definition

A flood is defined as the overflow of onto that is normally dry, resulting from an accumulation of water exceeding the capacity of established drainage channels or storage systems. Hydrologically, this manifests as a rise in within a , , or other beyond its bankfull , where bankfull discharge represents the maximum flow that can be contained within the channel without inundation of adjacent areas. This threshold is determined through gauge measurements of ( relative to a fixed reference point) and discharge (volume of water flowing past a point per unit time, typically in cubic feet or meters per second). Physically, flooding arises from the imbalance between water inflow—driven by precipitation, snowmelt, or upstream releases—and the channel's conveyance capacity, governed by factors such as cross-sectional area, hydraulic radius, slope, and roughness coefficient (e.g., via Manning's equation for open-channel flow: Q=1nAR2/3S1/2Q = \frac{1}{n} A R^{2/3} S^{1/2}, where QQ is discharge, nn is roughness, AA is area, RR is hydraulic radius, and SS is slope). When inflow exceeds this capacity, water spills onto floodplains, with velocity and depth influenced by gravity-driven flow and frictional resistance from terrain and vegetation. Peak discharge, the maximum instantaneous flow rate during an event, quantifies the flood's intensity and potential erosive power. Flood frequency analysis, rooted in statistical , estimates the magnitude of future events using historical discharge records, often expressed in terms of recurrence intervals (e.g., a has a 1% annual exceedance probability). This approach relies on empirical data from gauged sites, extrapolated via methods like log-Pearson Type III distribution, to define design floods for . Physically, the duration and volume of inundation depend on shape—rising limb (increasing discharge), peak, and falling limb—shaped by catchment characteristics such as infiltration rates and antecedent moisture conditions.

Classification by Scale and Magnitude

Floods are classified by magnitude primarily according to their stage height relative to established flood stages at gauging stations, as defined by the U.S. National Weather Service (NWS) and U.S. Geological Survey (USGS). These categories—minor, moderate, and major—reflect increasing levels of inundation, potential damage, and threat to life and property, determined by site-specific criteria based on historical data and local impacts. The action stage precedes flood stage and indicates preparatory measures without actual overflow. Minor flooding involves the lowest level of overflow, typically inundating low-lying areas near streams or rivers, with some disruption to roads, agricultural land, or minor structures but limited evacuations and property damage. Moderate flooding extends inundation to more populated or developed areas, causing significant disruptions such as closures of major roads, damage to homes and businesses, and necessitating widespread evacuations. Major flooding represents the highest category, featuring extensive inundation across broad regions, severe damage to infrastructure like bridges and utilities, prolonged evacuations, and high risk to human life, often exceeding historical records for the site.
CategoryDescription of ImpactsTypical Stage Height Example (varies by site)
Minor FloodingInundation of structures and roads near waterways; minor public threat; some possible but limited.1-3 feet above .
Moderate FloodingWidespread inundation of homes, businesses, and roads; significant evacuations; notable property losses.3-6 feet above .
Major FloodingExtensive flooding of communities; major damage; high threat to life; long-term recovery needed.Over 6 feet above , often record levels.
Scale refers to the spatial extent or hydrological basin size affected, ranging from localized events covering small watersheds (e.g., under 100 km², often flash floods) to basin-wide floods impacting large river systems spanning thousands of square kilometers. Magnitude can also be quantified probabilistically via or recurrence interval, where a "" denotes an event with a 1% annual exceedance probability, based on statistical analysis of peak discharge records; larger magnitudes correspond to rarer events like 500-year or 1,000-year floods. The Dartmouth Flood Observatory (DFO) employs a global magnitude scale from 0 (no flooding) to 10 (catastrophic, exceeding the flood of record by over 500%), integrating satellite-derived inundation area, duration, and discharge data for comparative assessment across sites. This scale facilitates international but relies on , which may underrepresent subsurface or compared to ground-based gauging. For dam-related floods, classifications incorporate potential downstream hazards, with inflow design floods scaled by structure size and failure consequences, such as probable maximum floods for high-hazard dams.

Geological and Prehistoric Floods

Megafloods in Earth History

Megafloods, also known as outburst floods, represent some of the most extreme hydrological events in 's geological record, characterized by peak discharges exceeding 1 million cubic meters per second—orders of magnitude greater than typical modern river flows—and capable of eroding vast landscapes in hours to days. These events primarily resulted from the sudden failure of natural dams, such as ice sheets or tectonic barriers, releasing impounded water volumes equivalent to entire modern inland seas. Evidence derives from paleohydraulic modeling, giant erosional landforms like coulees and scablands, boulder deposits displaced by high-velocity flows, and sedimentary sequences indicating rapid deposition. While megafloods dominate the record due to glacial-interglacial cycles amplifying ice-dam instabilities, older events highlight tectonic controls on basin isolation and refilling. The Zanclean megaflood, occurring approximately 5.33 million years ago at the start of the , stands as the largest documented, involving the Atlantic Ocean's breach of the sill to refill the desiccated Mediterranean Basin after the . This event transferred an estimated 1 million cubic kilometers of water over months to years, with initial peak flows potentially reaching 100 million cubic meters per second, carving submarine channels up to 1 kilometer deep and depositing erosional debris across the seafloor. Seismic profiling and sediment core analysis confirm the flood's erosive power, which incised the seafloor and redistributed evaporites, though debates persist on exact duration and whether it involved a single breach or phased incursions due to sill rates. Causal realism attributes this to tectonic uplift closing the strait around 5.96 million years ago, followed by isostatic rebound and upon reconnection, underscoring ' role in mega-scale hydrology beyond glacial mechanisms. In the , approximately 50,000 to 12,000 years ago, multiple megafloods emanated from ice-dammed lakes in northern hemispheres, driven by Cordilleran and Laurentide ice sheet advances that impounded proglacial waters until hydraulic pressures overcame ice dams. The of southern hosted some of the largest freshwater outbursts, with ice-dammed lakes like Chuja repeatedly draining via mechanisms, producing flows up to 2,500 meters deep and velocities exceeding 50 meters per second along the Katun and Chuja valleys. Geomorphic evidence includes overscoured U-shaped valleys filled with boulder-strewn sediments up to 100 meters thick, dated via optically stimulated luminescence to marine isotope stage 2 (around 25,000–15,000 years ago), indicating dozens of events that reshaped 10,000 square kilometers of terrain. These floods' scale rivals oceanic inflows, with empirical reconstructions from hydraulic simulations showing discharges of 1–5 million cubic meters per second, limited by valley confinement but amplified by sediment-laden hyperconcentrated flows. North America's , occurring between 18,000 and 12,000 years ago, involved repeated drainages of , which held up to 2,500 cubic kilometers of water dammed by the Purcell Trench lobe of the . Each outburst released volumes equivalent to 10% of in days, with peak discharges estimated at 10–17 million cubic meters per second through the , eroding the —a 30,000-square-kilometer tract of anastomosing channels, up to 120 meters high, and 10–15 meters tall spaced 100–200 meters apart. Paleoflow indicators, including erratic boulders weighing hundreds of tons transported 100 kilometers, and slackwater sediments in tributary valleys corroborate dozens to hundreds of events, with glacial isostatic rebound tilting drainages to favor scabland routing over time. Similarly, the singular around 14,500 years ago drained Bonneville—ancestor to the —via spillover at Red Rock Pass, yielding a peak flow of 1.2 million cubic meters per second sustained for weeks, which incised Canyon to depths of 150 meters and deposited gravel bars 20 meters high across 1,000 kilometers downstream. These megafloods empirically demonstrate ice-sheet dynamics' capacity for repeated cataclysms, with landscape inheritance persisting today in arid scablands defying uniformitarian models.

Evidence from Paleohydrology

Paleohydrology reconstructs prehistoric flood events through analysis of sedimentary deposits, erosional landforms, and hydraulic modeling, revealing magnitudes and frequencies far exceeding modern instrumental records in many regions. Slackwater deposits—fine sands and silts accumulated in low-velocity zones during high-magnitude floods—provide direct evidence of paleostage (water surface elevation) and enable discharge estimates via Manning's equation or similar hydraulic reconstructions. These deposits, often interbedded with coarser flood gravels, have been dated using radiocarbon, optically stimulated luminescence, or tephrochronology, extending flood chronologies back thousands to tens of thousands of years. Prominent evidence comes from the in , where megafloods from repeated drainage of —holding up to 2,500 cubic kilometers of water—eroded coulees up to 10 kilometers wide and deposited erratics weighing hundreds of tons. Paleohydrologic reconstructions indicate at least 40 such floods between approximately 19,000 and 13,000 years ago, with peak discharges reaching 10-20 million cubic meters per second, as inferred from boulder bars, giant gravelly current ripples (up to 15 meters high and 100 meters wavelength), and slackwater sediments in tributary valleys. These features, initially proposed by in the 1920s and later corroborated by glacial evidence, demonstrate dynamics driven by ice dam failures rather than uniformitarian . Analogous records exist in the Altay Mountains of , where ice-dammed lake outbursts produced superfloods around 15,000-14,000 years ago, carving braided channels and depositing sediment sheets traceable over 500 kilometers. Discharges here exceeded 1 million cubic meters per second, based on hydraulic modeling of straths and boulder fields, highlighting recurrent cataclysmic flooding at glacial terminations. Globally, paleoflood studies in Mediterranean and Asian rivers, using stacked slackwater sequences, document events with recurrence intervals of centuries to millennia, often surpassing 100-year floods recorded by gauges by factors of 2-5 in magnitude. Such data underscore non-stationarity in flood regimes, influenced by climatic shifts like rather than solely modern anthropogenic factors.

Types of Floods

Riverine and Fluvial Floods

Riverine and fluvial floods, terms often used synonymously, occur when rivers, streams, or creeks overflow their banks, inundating adjacent low-lying floodplains and areas. This type of flooding results from the accumulation of excess water in river channels exceeding their capacity, typically due to prolonged rainfall, rapid snowmelt, or upstream dam releases. The primary mechanism involves hydrological processes in the river basin, where precipitation exceeds soil infiltration and evapotranspiration capacities, leading to surface runoff that converges into tributaries and main stems. River levels rise gradually over hours to weeks, distinguishing fluvial floods from rapid-onset flash floods, though antecedent soil moisture and basin saturation can accelerate the response. Ice jams in colder climates or sediment buildup narrowing channels can exacerbate overflows by restricting flow. These floods often affect extensive areas along meandering rivers with broad floodplains, depositing and nutrients beneficial in agricultural contexts but causing , damage, and elsewhere. Historical examples illustrate their scale: the 1927 flood submerged 27,000 square miles across ten states, displacing 637,000 people and prompting major federal flood control reforms. The 1937 flood inundated , to depths of 30 feet, affecting one million residents and inflicting $500 million in damages equivalent to billions today. In 1993, the Great Flood of the Midwest along the and Rivers impacted nine states, resulting in $15 billion in economic losses and 50 fatalities.

Flash and Pluvial Floods

Flash floods involve the rapid onset of high-velocity water flows in streams, creeks, or normally dry channels due to excessive rainfall runoff, typically developing within six hours of the precipitating event. These events are distinguished by their sudden rise in water levels, often exceeding the absorption capacity of the ground and leading to destructive surges that can carry debris and erode landscapes. Contributing factors include intense, short-duration rainfall concentrated over small watersheds, steep terrain that accelerates runoff, sparse cover, and human modifications such as channelization or that reduce natural attenuation. Pluvial floods, in contrast, arise from extreme rainfall overwhelming surface or subsurface drainage capacities without reliance on overflowing rivers or other water bodies, resulting in widespread or shallow inundation. These floods occur when exceeds infiltration rates into saturated soils or the conveyance limits of urban systems, causing water to accumulate on impervious surfaces like roads and rooftops. In urban environments, flooding is intensified by high proportions of paved and built-up areas—often over 50% imperviousness—that generate rapid, high-volume , compounded by clogged drains, inadequate sizing, and poor maintenance. While events can develop more gradually than flash floods, intense instances overlap, with flash floods representing channelized manifestations of processes in steeper or confined settings. Notable flash flood examples include the March 1-2, 1997, event in , where over 10 inches of rain in 24 hours triggered widespread ing, damaging and across multiple counties. In arid regions, such as the Rapid Creek flood in , , on March 17, 1988, a 6-inch deluge in hours transformed dry gullies into raging torrents, destroying bridges and homes while causing 1 death and $20 million in damages (in 1988 AUD). For flooding, urban cases like those in European cities during summer thunderstorms demonstrate how overwhelmed sewers lead to street submersion; for instance, in July 2021, extreme rain in and —up to 7 inches in hours—caused inundation that contributed to over 200 fatalities, primarily from basement flooding in poorly drained suburbs. These floods pose acute risks due to limited warning time, with flash variants endangering lives through (accounting for over 90% of flood deaths in the U.S.) and types threatening property via , mold, and economic disruption from halted transport.

Coastal and Surge Floods

Coastal flooding involves the temporary inundation of low-lying coastal land by seawater exceeding normal tidal limits, often driven by elevated water levels from multiple sources including storm surges, extreme tides, waves, and seiches. Storm surges represent a dominant form, defined as the abnormal rise in seawater level generated by a storm's winds and low pressure over and above predicted astronomical tides, leading to rapid onshore water movement that can penetrate several kilometers inland depending on topography. These events differ from general flooding by originating directly from oceanic dynamics rather than solely terrestrial runoff, though they may compound with rainfall-induced floods in coastal zones. The physics of storm surge formation primarily involves wind-driven water piling (setup), where sustained onshore winds over a long fetch transfer momentum to the sea surface, creating a sloping mound toward the ; this is augmented by the inverse effect, wherein atmospheric low pressure allows to rise roughly 1 cm per millibar drop due to reduced overlying air weight. Wave action further contributes by breaking and runup on shores, adding to total height, while shallow coastal amplifies surges through funneling effects in bays or estuaries. Coastal configuration, such as narrowing inlets or barriers, can intensify surges via or reflection, with empirical models showing surge heights scaling with storm intensity, forward speed, and angle of approach. Historical examples illustrate surge severity: during on August 29, 2005, surges reached 25 to 28 feet above normal tide levels along the coast, overtopping levees and flooding areas up to 6 miles inland, resulting from the storm's Category 3 and persistent easterly winds. Similarly, the in the generated surges of 10 to 16 feet that inundated low-lying , contributing to over 300,000 deaths through widespread coastal submersion. In contrast, non-surge coastal floods like high-tide or nuisance flooding occur during calm conditions when mean sea levels exceed drainage thresholds, with U.S. coastal sites recording an average increase from 4.4 days per year in 2000 to 7.6 days in 2020, linked to observed sea level rise of about 3.7 mm annually. Such floods disproportionately affect deltas, barrier islands, and urbanized shores, where and development exacerbate ; for instance, surge propagation can reverse river flows, causing backwater effects miles upstream. Empirical tide gauge data confirm surge heights rarely exceed 40 feet globally, limited by physical constraints like saturation, though compound events with amplify total storm tide. relies on accurate via hydrodynamic models incorporating these mechanisms, underscoring the causal primacy of over long-term trends in acute events.

Catastrophic Floods from Dam Failures or Outbursts

Catastrophic floods from failures or outbursts occur when engineered or natural impoundments, such as glacial lakes, suddenly release large volumes of due to structural collapse, overtopping, or breach mechanisms like or foundation instability. These events produce high-velocity flood waves that propagate downstream, often amplified by channel confinement, leading to widespread destruction far beyond typical riverine flooding. Unlike gradual floods, the rapid onset—sometimes within minutes—limits evacuation time and exacerbates human and infrastructural losses, with historical cases demonstrating death tolls in the thousands to hundreds of thousands and economic damages exceeding billions in modern equivalents. The failure in China's Province on August 8, 1975, stands as the deadliest such event, triggered by Typhoon Nina's extreme rainfall exceeding design specifications for the earth-fill dam completed in 1952. Over 60 dams in the system collapsed in a cascade, releasing approximately 492 million cubic meters of water at peak outflows of 78,000 cubic meters per second from Banqiao alone, inundating 12,000 square kilometers and affecting 11 million people. Official reports cited 26,000 deaths from , but independent estimates, accounting for subsequent epidemics and from destroyed crops, range from 171,000 to 230,000 fatalities, highlighting underreporting in state-controlled data. In the United States, the failure near , on May 31, 1889, following heavy rains on an inadequately maintained structure, unleashed 20 million tons of water in a 60-foot-high wave traveling at 40 miles per hour, destroying Johnstown and killing 2,209 people while damaging across 15 miles. Earlier neglect, including insufficient capacity and poor construction materials, contributed to the breach, underscoring risks from aging or substandard dams in populated areas. The failure in on June 5, 1976, exemplifies engineering oversight in a modern context, where seepage through fractured led to internal and sudden of the 305-foot-high earthfill structure just after filling began. The outburst discharged 80 billion gallons at over 1 million cubic feet per second, flooding 300 square miles, killing 11 people, 13,000 , and causing $2 billion in damages (1976 dollars) to homes, farms, and highways downstream. Investigations revealed inadequate geologic assessment and grouting, prompting U.S. regulatory reforms for seepage control. Glacial lake outburst floods (GLOFs), involving natural ice or dam failures often triggered by calving, , or thermal melting, pose ongoing s in mountainous regions, with over 3,000 documented events globally since 850 CE. A notable example is the 1941 GLOF from Lake Palcacocha in Peru's , where a burst after an ice , killing around 5,000 people and destroying ; such events release water volumes up to billions of cubic meters at speeds exceeding 30 meters per second, eroding valleys and depositing massive debris fields. Climate-driven retreat has increased GLOF frequency and exposure, with 15 million people at worldwide, particularly in High Mountain Asia. The Vajont Reservoir disaster in on October 9, 1963, illustrates landslide-induced outbursts, where 260 million cubic meters of rock slid into the Vajont Dam's , generating a 250-meter-high displacement wave that overtopped the intact and swept through the Piave , killing 1,917 people in villages like . Despite the dam structure surviving, the event exposed flaws in geotechnical modeling and during filling, with premonitory creep ignored.

Causes and Triggers

Natural Meteorological and Geological Factors

Excessive from meteorological phenomena constitutes the dominant natural driver of floods, with heavy fall overwhelming soil infiltration capacities and river channels. Intense thunderstorms, particularly slow-moving systems or those exhibiting "" behavior—where multiple storms repeatedly impact the same watershed—can deliver 4-8 inches (100-200 mm) of within hours, precipitating flash floods that rise rapidly in small streams and urban areas. Tropical cyclones, including hurricanes and typhoons, exacerbate this through sustained heavy and wind-driven surges; for example, s—narrow corridors of concentrated moisture—have fueled record floods, such as the 2023 atmospheric river events that dropped up to 10 inches (250 mm) in a day, saturating basins already primed by prior storms. Snowmelt floods arise from the seasonal thawing of accumulated , accelerated by warm temperatures or superimposed rainfall, which increases runoff volumes in river systems. In northern latitudes and mountainous regions, spring melt can elevate river stages by combining with residual winter precipitation; historical data indicate that such events often peak when snow water equivalent exceeds 20-30% above average, as observed in recurring Midwest U.S. floods where limits absorption. Ice jams, formed by freezing river segments breaking under pressure, further amplify upstream ponding and sudden releases. Geological factors contribute through tectonic and volcanic processes that disrupt hydrological equilibrium. Seismic activity from earthquakes can trigger landslides, temporarily damming rivers and leading to outburst floods upon breach; magnitudes above 6.0 often correlate with such secondary flooding in steep terrains. Volcanic eruptions generate lahars—debris-laden floods mixing , , and rock—that propagate downstream at speeds up to 40 mph (64 km/h), as evidenced by post-eruption sediment loads reducing channel conveyance and extending flood durations for years. Glacial outbursts from natural ice-dammed lakes represent another mechanism, releasing pent-up in pulses equivalent to years of discharge. These events underscore causal linkages where geological instability amplifies meteorological inputs into catastrophic inundation.

Human-Induced Contributors

Urbanization significantly exacerbates flood risk by converting permeable natural surfaces into impervious ones, such as asphalt and , which reduce infiltration and increase the speed and volume of during events. This alteration shortens hydrological response times and amplifies peak flows, as evidenced by hydrological models showing that urban expansion in watersheds correlates with higher flood frequencies and magnitudes. Empirical analysis of U.S. basins indicates that each one increase in impervious cover causes a 3.3% rise in annual flood magnitude, with confidence intervals confirming the effect's robustness. Deforestation removes vegetative cover that rainfall and enhances soil infiltration, thereby elevating runoff coefficients and flood peaks in affected catchments. Observational data from forested regions demonstrate that loss of tree cover can increase the probability of large-scale flooding by up to eight-fold, particularly through reduced canopy during intense storms. Historical simulations of medieval and modern land clearance further reveal that widespread amplifies flood event magnitudes by altering basin , though effects are more pronounced for frequent, moderate floods than rare extremes, where natural dominance may mask some impacts. River engineering practices, including channelization and construction, aim to constrain flows but often produce unintended downstream consequences by accelerating water velocities, eroding channels, and limiting attenuation. disconnect rivers from natural storage areas, fostering "flood teleconnections" that redistribute risks spatially, sometimes increasing inundation in adjacent or lower basins during overtopping events. For instance, diversion structures like those on the have redirected peak flows, heightening pressures on unprotected and contributing to amplified flooding elsewhere. Agricultural land-use changes, such as drainage and intensive , compact soils and reduce permeability, thereby boosting runoff from fields during heavy rains. Experimental evidence confirms that converting forests to cropland or elevates catchment discharge compared to undisturbed vegetation, with forest cover mitigating average flows through enhanced and . Inadequate maintenance, including silted channels or poorly managed reservoirs, further compounds these risks by impeding natural drainage and promoting sudden releases during overload.

Climate Variability versus Anthropogenic Change

Natural climate variability, including oscillations such as the El Niño-Southern Oscillation (ENSO), (AMO), and (PDO), has long driven fluctuations in flood occurrence and intensity through alterations in precipitation patterns, storm tracks, and soil moisture conditions. For instance, positive phases of the AMO correlate with increased flood risk in parts of and due to enhanced moisture transport, while La Niña events often amplify winter flooding in the . These modes operate on timescales from years to decades, masking potential long-term trends and explaining much of the observed variability in flood records spanning centuries, as evidenced by paleoflood data from river sediments showing comparable megaflood events during the (circa 950–1250 CE) to those in the . In contrast, anthropogenic climate change, primarily from , is theorized to intensify floods via the Clausius-Clapeyron relation, which predicts a 6–7% increase in atmospheric capacity per degree of warming, potentially leading to heavier events. However, empirical analyses of global and regional flood frequency and magnitude reveal no consistent upward trend attributable to influence. In the United States, normalized flood damage and peak streamflow records from 1932–2023 show no detectable increase linked to warming, with socioeconomic factors like development accounting for rising losses. Similarly, a synthesis of over 8,000 gauging stations worldwide indicates mixed trends, with decreases in flood magnitude in 35% of sites and increases in only 15%, often overshadowed by land-use changes and data inhomogeneities rather than a coherent anthropogenic signal. Attribution studies attempting to quantify influence on specific floods, such as those using event-based modeling, claim enhancements in 64% of analyzed Japanese events from 2010–2013, but these rely on simulations that amplify model uncertainties and fail to robustly separate variability from forcing. The IPCC assesses medium confidence in human-driven increases in heavy precipitation over land (detectable since the mid-20th century), but low confidence in corresponding changes to flood hazards globally, acknowledging that natural variability dominates in many basins and that exposure growth confounds damage interpretations. Critiques highlight that claims of anthropogenic dominance often stem from selective regional data or projections rather than comprehensive observational records, where no global frequency increase is evident through 2020 despite 1.1°C of warming. Projections under RCP scenarios suggest potential flood magnitude increases in 47–74% of watersheds by 2100, but these depend on unverified model physics and ignore adaptive measures or variability's persistence. Overall, while anthropogenic warming may marginally elevate extreme rain risks in vulnerable regions, flood records underscore natural variability's primacy, with human development—not —as the chief escalator of impacts.

Hydrological Processes

Rainfall-Runoff Mechanisms

Rainfall-runoff mechanisms describe the physical processes by which on a catchment transforms into surface or subsurface flow that contributes to and potential flooding. When rainfall occurs, initially infiltrates the , is intercepted by , or is temporarily stored in depressions; excess beyond these capacities generates runoff. The primary pathways include overland flow and subsurface flow, with the former dominating rapid flood responses due to its direct contribution to channel routing. Infiltration-excess overland flow, termed Hortonian overland flow after Robert Horton's 1930s experiments, arises when rainfall intensity exceeds the soil's infiltration capacity, determined by factors such as , , and surface crusting. This mechanism is prevalent in semi-arid regions, steep slopes, or disturbed lands where infiltration rates drop below 10-50 mm/h during intense storms, causing water to pond briefly and then sheet across the surface toward channels. For instance, on clay-rich soils with low permeability, infiltration capacities can limit to under 20 mm/h, promoting widespread runoff even from moderate events. Saturation-excess overland flow, or overland flow, occurs when soil pores become fully saturated—often from rising or prolonged prior wetting—rendering additional rainfall unable to infiltrate, thus spilling over as surface flow. This process typically dominates in humid, low-relief catchments with high antecedent moisture, where only saturated "variable source areas" near contribute runoff, often comprising 5-20% of the basin area during peak events. Unlike infiltration excess, it can generate runoff from any rainfall intensity once saturation thresholds are met, leading to slower but volumetrically significant flood peaks. Key factors modulating these mechanisms include antecedent , which amplifies saturation excess; cover, reducing effective rainfall by 10-30% through and enhancing infiltration via channels; topographic , accelerating overland flow velocity per Manning's equation (v ≈ ()^{1/2}); and , where impervious surfaces like urban pavement eliminate infiltration, converting nearly 100% of rainfall to direct runoff. properties, such as (e.g., sands >100 mm/h vs. clays <1 mm/h), interact with storm duration and intensity—events exceeding 50 mm/h often trigger infiltration excess regardless of prior conditions. These dynamics explain why flash floods from short, intense rains favor Hortonian processes, while prolonged events in wet seasons rely on saturation excess for basin-wide response.

Channel and Basin Dynamics

Drainage basins, defined as the topographic areas from which drains into a specific river system, fundamentally shape flood hydrographs through their morphological and hydrological properties. Basin area determines total runoff volume, with larger basins aggregating contributions from extensive sub-catchments, often leading to prolonged flood durations compared to smaller, flash-prone systems. Steep basin slopes enhance runoff velocity via increased , reducing infiltration time and amplifying peak discharges, as evidenced in analyses of arid watersheds where slope gradients correlate directly with flood magnitude. permeability and antecedent moisture further modulate dynamics: saturated soils exhibit lower infiltration rates, promoting Hortonian overland flow, while unsaturated conditions favor subsurface storage and delayed contributions. influences these processes, with vegetated basins attenuating peaks through interception and , whereas impervious surfaces in urbanized areas accelerate direct runoff, shortening lag times by up to 50% in modified catchments. River channels serve as primary conduits for floodwaters, their dynamics governed by hydraulic geometry relations that link cross-sectional dimensions to discharge. At-a-station hydraulic geometry describes how channel width expands with discharge to the power of approximately 0.2-0.5, depth to 0.3-0.4, and to 0.3-0.5, maintaining continuity of flow under varying regimes. During floods exceeding bankfull capacity—typically 1.5-2 times mean annual discharge—channels experience heightened boundary , inducing scour and lateral migration, which can widen channels by 10-20% in a single event in unconfined alluvial settings. This adjustment enhances conveyance but risks instability, as rapid incision or alters slope and roughness coefficients, influencing Manning's n values from 0.03 in clean channels to 0.1+ with debris. In gravel-bed rivers, flood-induced bedload reorganizes armor layers, temporarily increasing capacity before equilibrium restoration. Interactions between basin-scale inputs and channel responses occur via routing processes, where incoming hydrographs attenuate through storage and along the channel network. The Muskingum routing equation, parameterized by storage coefficients (travel time, often 1-24 hours) and X (weighting factor, 0-0.5), models this by balancing inflow, outflow, and wedge storage, with higher X values indicating -dominated attenuation in meandering channels. Basin-derived propagate downstream with celerity reduced by spilling, where overbank flows engage secondary channels and storage zones, dissipating up to 30-50% of peak energy in wide alluvial valleys. Cross-section geometry plays a pivotal role: narrow, incised channels promote kinematic wave propagation with minimal , while broad foster hydrodynamic via lateral exchange. Empirical studies confirm that channel- connectivity enhances this effect, with fragmented networks leading to higher local peaks due to bypassed storage. These dynamics underscore causal links from basin precipitation partitioning to channel conveyance limits, informing risk where anthropogenic straightening reduces natural .

Impacts and Consequences

Human, Infrastructural, and Economic Losses

Floods inflict severe human losses, including fatalities, injuries, and displacement. Globally, between 1980 and 2009, floods caused an estimated 539,811 deaths and affected over 2.8 billion people. Historical events underscore the scale: the 1931 Yangtze River floods in resulted in 1 to 4 million deaths due to prolonged inundation and subsequent and . In the United States, in 2005 led to 1,833 flood-related fatalities, marking the deadliest such event in modern American history. Death tolls often vary due to challenges in verification, particularly in regions with limited reporting , and flash floods account for a disproportionate share of fatalities relative to their frequency. Injuries and displacement compound these tolls, with floods frequently overwhelming emergency response capacities. For instance, water-related hazards, including floods, accounted for 45% of all reported deaths from disasters between 1970 and 2019, while displacing millions annually through destruction of homes and contamination of water supplies. In the U.S., flash floods have caused hundreds of deaths over the past century, often from vehicle submersion or in urban areas. Infrastructural damage from floods encompasses roads, bridges, utilities, and buildings, leading to widespread service disruptions. Buried like sewers and power lines suffers erosion and contamination, as seen in , which inflicted $5.5 billion in damage to roads, bridges, and other public assets. Floodwaters erode foundations, collapse structures, and overload drainage systems, with failure cascades amplifying impacts—such as power outages triggering failures—in up to 89% of analyzed events. In urban settings, traditional infrastructure exacerbates damage by channeling water rapidly, as evidenced by events causing billions in repairs to highways and substations. Economic losses from floods arise from direct destruction, indirect declines, and recovery expenditures, totaling an annual global average of $388 billion. In 2023, flood-related damages reached $85 billion worldwide, ranking second only to convective storms among weather perils. The U.S. experiences about $5 billion in annual flood damages, with major events like the 1993 Great Flood costing over $45 billion (CPI-adjusted) in agricultural and infrastructural losses. These figures exclude uninsured losses and long-term economic drags, such as reduced business activity and migration, which can extend impacts for years.

Environmental and Ecological Effects

Floods disrupt terrestrial and aquatic ecosystems through physical forces, , and contaminant mobilization. High-velocity floodwaters erode , uproot , and displace or drown , leading to immediate . Floods also affect forests worldwide, causing erosion, dieback, and inundation in tropical and riverine areas. While comprehensive global statistics specifically for floods impacting forests—such as annual occurrences of forest-affected events, flooded forest areas, associated deaths, or economic damages—are unavailable in major databases like EM-DAT, which categorize floods by type and location rather than land cover, general worldwide flood data from EM-DAT indicate 200-300 events annually in recent decades, with average annual deaths of ~5,000-6,000 and economic damages often exceeding $40-100 billion. Examples include the 2022 Pakistan floods affecting forested regions and seasonal inundation in the Amazon. In riparian zones, such erosion can remove up to 30-40% of plant in affected areas, altering composition and suppressing dominant . Aquatic environments suffer from increased and , which smother benthic organisms and reduce light penetration essential for in submerged plants. Suspended sediments degrade , harming and disrupting food webs, while deposited sediments can bury spawning grounds and alter channel morphology. Floods mobilize pollutants from agricultural runoff, urban overflows, and industrial sites, introducing excess nutrients that trigger algal blooms and hypoxic conditions downstream. Biodiversity declines as floods drown terrestrial species, fragment habitats, and facilitate establishment in disturbed soils. In extreme events, such as the 2020 floods in the UK, repeated inundation collapsed ecosystems, reducing and populations reliant on stable floodplains. Marine extensions of flood plumes carry contaminants to coastal zones, stressing coral reefs and mangroves through and chemical exposure. Long-term ecological shifts include nutrient leaching from , which diminishes and vegetation recovery, and altered hydrological regimes that favor flood-tolerant but less diverse species assemblages. In urbanized basins, impervious surfaces amplify these effects, with channel incision and exacerbating downstream loads by factors of 2-10 times pre-development levels. These disruptions cascade through trophic levels, reducing overall resilience to future disturbances.

Positive Ecological and Agricultural Benefits

Periodic flooding in river floodplains deposits sediments laden with nutrients such as , , , and , thereby enhancing and supporting subsequent plant growth. This natural fertilization process reduces the reliance on synthetic inputs in floodplain , as observed in systems where annual inundation replenishes layers. In agricultural contexts, seasonal river flooding enables flood recession farming, where receding waters leave moist, nutrient-enriched soils ideal for crops like or , yielding higher harvests with lower labor and costs compared to rain-fed inland fields. Such practices have sustained productivity in regions of , , and , where river-floodplain interactions historically provided primary food sources without extensive artificial amendments. Ecologically, floods recharge groundwater aquifers by allowing infiltration through permeable floodplain soils, maintaining hydrological balance and supporting baseflow in rivers during dry periods. This process sustains wetlands and riparian ecosystems, filtering pollutants and stabilizing water tables essential for long-term aquifer viability. Floodplains inundated by periodic floods create diverse habitats that bolster , including breeding grounds for , waterfowl, and , while promoting nutrient cycling and sediment exchange. The Flood Pulse Concept describes how predictable seasonal inundations drive productivity in riverine systems, generating habitat mosaics that enhance and resilience. In dynamic floodplains, variable connectivity with river flows fosters heterogeneity, supporting fisheries and terrestrial wildlife adapted to these cycles.

Prediction, Monitoring, and Risk Assessment

Hydrological Forecasting Models

Hydrological forecasting models simulate the transformation of into and potential flooding within catchments, enabling predictions of flood magnitude, timing, and extent. These models integrate meteorological inputs, such as rainfall forecasts from systems, with representations of basin to provide lead times for warnings, typically ranging from hours for flash floods to days for riverine events. Process-based models rely on physical equations describing infiltration, , and routing, while data-driven approaches leverage statistical patterns from historical data. Models are classified by and approach: lumped models aggregate catchment processes into single units for simplicity, suitable for data-scarce areas; semi-distributed and fully distributed models incorporate spatial variability via grid-based or sub-basin divisions, improving resolution for heterogeneous terrains. Deterministic models assume fixed parameter-response relationships, whereas variants account for uncertainty through probabilistic outputs. Rainfall-runoff models form the core, often coupled with hydraulic models solving for inundation mapping. Prominent examples include the Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS), developed by the U.S. of Engineers, which employs conceptual rainfall-runoff methods like the Clark unit hydrograph for event-based simulations and has demonstrated superior peak flow prediction in comparative studies against alternatives. The Soil and Water Assessment Tool (), a semi-distributed model, simulates continuous hydrology in agricultural watersheds by partitioning and sediment transport, though it may underperform HEC-HMS in rapid peak events due to coarser . MIKE models, such as MIKE SHE for integrated surface-subsurface flows and MIKE 11 for one-dimensional river routing, support hydrodynamic coupling for detailed flood propagation, applied in basins like where they integrate with neural networks for enhanced process simulation. The WRF-Hydro system, an open-source framework, excels in prediction by nesting high-resolution routing within weather research and outputs. Recent advancements incorporate to address physical model shortcomings, such as the ML4FF framework combining networks with hydrodynamic simulations for lead times up to 6 hours, achieving accuracies exceeding 90% in validation datasets. Hybrid systems, blending physics-based cores like the National Water Model with AI post-processing, have reported 4-6 fold improvements in over traditional ensembles. However, limitations persist: data scarcity in ungauged basins amplifies parameter uncertainty, with models like HEC-HMS sensitive to calibration errors yielding Nash-Sutcliffe efficiencies below 0.7 in poorly gauged regions; computational intensity hampers real-time deployment for distributed hydrodynamic runs; and assumptions in process representation fail under non-stationary climate conditions, as evidenced by overestimations in extreme events. , via ensemble methods or , remains essential but computationally demanding.

Empirical Risk Evaluation

Empirical flood evaluation quantifies the likelihood and severity of flooding through statistical of historical hydrological , prioritizing observed records over theoretical modeling to derive probabilistic estimates. This approach assumes relative stationarity in flood-generating processes unless evidence indicates otherwise, enabling the calculation of flood magnitudes associated with specific recurrence intervals. For example, the (USGS) employs flood frequency on gauged to estimate peak discharges, using distributions fitted to annual maximum series. A core metric is the return period, defined as the reciprocal of the annual exceedance probability for a given flood magnitude; a thus has a 1% probability of occurrence in any year, independent of prior events under the assumption of independence. Techniques such as the Log-Pearson Type III distribution, recommended in USGS Bulletin 17C guidelines, fit empirical data by estimating parameters from at-site records typically spanning 30–100 years, with regional adjustments for ungaged sites via regression on basin characteristics like drainage area and . These methods have been applied globally; for instance, analysis of U.S. river gauges shows that return periods for extreme floods vary by region, with arid basins exhibiting higher variability due to sporadic intense rainfall. To address limitations of short instrumental records, paleoflood hydrology reconstructs pre-modern flood events from geomorphic evidence, such as slackwater deposits and deposits in canyons, yielding discharge estimates for floods predating gauges by centuries or millennia. In the American Southwest, paleoflood studies on rivers like the Salt and Verde have identified magnitudes exceeding modern 500-year floods, extending frequency curves and reducing uncertainty in tail-risk estimates by incorporating non-stationary paleodata. This empirical extension has informed safety assessments, revealing that reliance solely on recent records underestimates in tectonically active or climatically variable basins. Vulnerability components of are empirically derived using depth-damage functions, which correlate observed inundation depths from past floods with documented economic losses, structural ratios, and human impacts. For urban areas, these curves indicate that damages escalate nonlinearly with depth, often reaching 50–100% of asset value above 1 meter, as evidenced by post-event surveys in and . Overall integrates hazard probability with exposure metrics, such as in floodplains, but empirical evaluations caution against overextrapolation from biased samples, like urban-biased loss records that may inflate perceived trends. Limitations include data scarcity in developing regions and non-stationarity from land-use changes, necessitating validation against independent historical accounts.

Technological Advances Since 2020

Since 2020, (AI) and (ML) have significantly enhanced flood prediction accuracy by integrating with traditional hydrological models. A hybrid AI model developed in 2025 improved flood forecast precision by 4 to 6 times over the U.S. National Water Model, reducing errors in peak flow predictions through and deep neural networks trained on historical data and real-time inputs. Similarly, Google's Flood Hub, leveraging ML algorithms on public datasets, provides up to seven-day advance warnings in over 80 countries, outperforming physics-based models in data-sparse regions by incorporating and gauge . Satellite-based has advanced flood monitoring through (SAR) imagery, enabling all-weather detection of inundation extents. Vision transformers (ViTs) applied to SAR data since 2023 have improved global flood mapping resolution, identifying water-covered areas with over 90% accuracy in post-event analysis, as demonstrated in studies using satellites. Multi-source platforms, integrating optical and data, now support real-time apps for rapid flood delineation, reducing mapping times from days to hours during events like the . Unmanned aerial vehicles (UAVs or drones) and IoT sensor networks have bolstered on-ground by providing high-resolution, localized data. Drone-based systems, deployed since 2022, detect blockages and in real-time, aiding predictive modeling of propagation with sub-meter accuracy. Advanced sensors, including ultrasonic detectors and networks, have been integrated into flood early warning systems (FEWS), enhancing spatial risk visualization through , as reviewed in 2024 analyses of post-2020 deployments in vulnerable basins. These technologies collectively enable probabilistic risk evaluations, with ML-driven models forecasting high-risk zones up to 72 hours ahead based on and ensembles.

Mitigation, Engineering, and Adaptation

Structural Defenses and Infrastructure

Structural flood defenses encompass engineered infrastructure designed to contain, divert, or impound floodwaters, thereby reducing inundation risks to populated and economic areas. These measures, often termed "hard" solutions, include levees, floodwalls, , reservoirs, and movable barriers, which physically alter water flow dynamics to mitigate peak discharges. Such systems have proven effective in numerous instances, as evidenced by the protection of over 36,000 square miles of the alluvial valley through the Mississippi River and Tributaries () Project, authorized in 1928 and comprising levees, floodways, and channel improvements. Levees and embankments form the backbone of many riverine flood control systems, raising riverbanks to confine waters within channels during high flows. The MR&T levees, maintained by the U.S. Army Corps of Engineers, are designed to withstand the "project design flood," equivalent to 125% of the 1927 Great Mississippi Flood's volume, preventing overflows across vast agricultural and urban expanses. Similarly, floodwalls and seawalls provide rigid barriers in urban settings, constructed from to halt tidal or coastal surges; these have been deployed globally, though their permanence limits adaptability to changing hydrological conditions. Dams and reservoirs upstream serve dual purposes of storage and controlled release, attenuating flood peaks by impounding excess runoff. The in , completed in 2006, holds a flood control capacity of 22.15 billion cubic meters, safeguarding the middle and lower basins from catastrophic inundation during monsoonal events. Movable barriers offer operational flexibility; the in , operational since May 1982, spans 520 meters across the river and has been raised 221 times for tidal flood defense as of April 2024, averting potential submersion of 125 square kilometers of central . The Netherlands' Delta Works exemplifies comprehensive estuarine protection, initiated post-1953 North Sea flood that claimed over 1,800 lives. This network of 13 components—including dams, sluices, and storm surge barriers—shortens the coastline by sealing off vulnerable inlets, with construction spanning 1958 to 1997 at a cost of approximately €5 billion (adjusted). Despite successes, structural defenses carry risks of failure from overtopping, erosion, or inadequate design against extreme events. The 2005 Hurricane Katrina breaches of New Orleans-area levees, part of the MR&T system, resulted in widespread flooding due to storm surge overwhelming understrength sections, highlighting vulnerabilities in aging infrastructure and subsidence-prone soils. Regular maintenance and upgrades, such as levee enlargements, are essential, yet these systems can foster development in flood-prone zones, amplifying potential losses upon breach. Recent initiatives integrate structural enhancements with monitoring; for instance, New York City's East Side Coastal Resiliency project, advancing as of 2025, elevates waterfront infrastructure along 4 kilometers of shoreline to counter sea-level rise and storm surges projected by 2050. Overall, while effective in reducing flood probabilities—Thames Barrier operations have prevented billions in damages—their long-term efficacy depends on probabilistic modeling of rare events and adaptation to climatic shifts, underscoring the need for hybrid approaches combining hard defenses with non-structural strategies.

Policy, Planning, and Land-Use Strategies

Non-structural flood mitigation relies heavily on policy frameworks that integrate flood risk into , prioritizing the restriction of development in high-risk areas over reactive engineering solutions. In the United States, the (NFIP), enacted via the National Flood Insurance Act of 1968, conditions federal flood insurance availability on local adoption of management ordinances. These ordinances typically mandate that new construction in the 100-year —defined as areas with a 1% annual chance of flooding—be elevated to or above the base flood elevation (BFE) or that substantial improvements meet equivalent standards, thereby reducing potential damages by preserving storage and conveyance functions. Communities must also enforce prohibitions on fill that raises land above BFE without compensatory storage, as evidenced by model ordinances adopted in states like , where such regulations have been analyzed for their role in directing growth away from flood hazards. Empirical evaluations confirm the effectiveness of these approaches in lowering exposure over time. A study of coastal regions found that land-use regulations implemented post-2000 reduced the prevalence of vulnerable structures, such as residential and commercial buildings, in designated zones by 2018, correlating with fewer high-risk land uses compared to baseline data from 2000. Similarly, setback requirements—mandating buffers from rivers or coasts—enhance resilience by maintaining vegetative cover that slows runoff, with data from U.S. communities showing decreased depths in regulated versus unregulated areas during events. Property acquisition and buyout programs represent another core strategy, converting repeatedly ed parcels to permanent open space; along the , non-structural initiatives initiated in the 1950s have acquired thousands of properties, yielding net savings in avoided damages estimated at multiples of program costs based on post- relocation data. Challenges persist in policy enforcement, often due to local pressures for overriding assessments. Despite NFIP mapping, over 13 million U.S. remain in special areas, with many post-1970s constructions reflecting lax amid growth incentives. Integrated processes, such as those optimizing land-use patterns for flood storage—like prioritizing permeable surfaces and wetlands preservation—have shown simulation-based reductions in peak flows by up to 20-30% in urban case studies from cities, underscoring the causal link between undeveloped floodplains and attenuated inundation. International examples, including process-oriented land policies in emphasizing small-scale retention over large projects, further demonstrate that adaptive can balance with , though success hinges on consistent data-driven updates to maps rather than static regulations.

Historical and Recent Case Studies

The 1953 North Sea Flood prompted a comprehensive response in the , where a on February 1 breached dikes, flooding 340,000 acres, displacing 100,000 people, and causing 1,836 deaths. In response, the Dutch government initiated the project in 1958, constructing 13 major components including dams, sluices, locks, dikes, and storm surge barriers to shorten the coastline by two-thirds and reduce vulnerable dike lengths from 3,000 to 700 kilometers. This adaptive infrastructure, completed in 1997, has proven effective, with no major delta-area floods occurring since, and designs calibrated for storm surges with a 1-in-4,000-year probability, demonstrating successful integration of and . Historical efforts to control the in illustrate persistent engineering challenges due to high silt loads and frequent breaches. Over , dynasties constructed extensive systems, with modern interventions including the 1950s Sanmenxia Dam for sediment trapping and flood storage, yet reduced capacity by 70% within decades, necessitating ongoing and supplemental dikes. The 1931 flood, exacerbated by incomplete maintenance, killed up to 4 million through inundation and subsequent , underscoring how human modifications, including and over-reliance on rigid structures, amplified flood severity rather than mitigating it via adaptive land-use strategies. Subsequent adaptations incorporated multi-reservoir operations and , reducing breach frequency from 10 times more common in the past compared to earlier periods, though empirical indicate 80% of increased flooding stems from anthropogenic factors like channelization. Hurricane Katrina in 2005 exposed vulnerabilities in the U.S. Army Corps of Engineers' levee system around New Orleans, where failures at 50 sites, including scour-induced breaches at the 17th Street and Industrial Canals, flooded 80% of the city and contributed to 1,800 deaths. analyses revealed design flaws such as inadequate I-wall foundations in soft soils and underestimation of surge loads, leading to post-event reinforcements including deeper sheet pile walls, gated structures, and a $14.5 billion system upgrade completed by 2011 that withstood subsequent storms like Isaac in 2012. Lessons emphasized hybrid approaches combining structural hardening with non-structural measures like wetland restoration for natural buffering, though critiques note persistent risks from and sea-level rise, highlighting the limits of engineered defenses without integrated . Recent applications of these principles appear in the Netherlands' ongoing Delta Programme, adapting to climate projections by raising dike heights and incorporating room-for-the-river strategies that widen floodplains for controlled overflow, averting damages during the 2021 Rhine floods. In contrast, the , affecting 33 million amid deficient embankment maintenance, revealed adaptation gaps in developing contexts, where earthen levees failed under intensification, prompting international aid for resilient but underscoring failures in upstream over reactive . These cases affirm that effective mitigation hinges on empirical calibration of designs to local and iterative adjustments, rather than static barriers, with successes correlating to proactive, data-driven investments exceeding reactive expenditures by factors of 3-7 in cost-benefit ratios.

Notable Historical and Recent Events

Pre-20th Century Floods

Floods prior to the inflicted massive casualties and economic losses, especially along silt-laden rivers prone to dike failures and course shifts, with China's accounting for many of the deadliest incidents due to its nickname "China's Sorrow" from recurrent inundations. The , occurring in late September during the , resulted from multiple dike breaches in Province, inundating roughly 50,000 square miles across several provinces and displacing millions while causing and . Estimated fatalities ranged from 900,000 to 2 million, marking it as one of history's most lethal single flood events, exacerbated by inadequate maintenance of levees and the river's heavy sediment load that raised bed levels above surrounding plains. In , the stands out for its scale in the , triggered by an extraordinarily wet winter with continuous storms from October 1861 to January 1862, submerging California's Sacramento and San Joaquin valleys over 250 miles long and up to 30 feet deep in places. This event, affecting , , and parts of Washington as well, destroyed farms, livestock, and infrastructure, prompting the state legislature to temporarily relocate to and leading to long-term shifts in flood management practices, though precise death tolls remain uncertain and likely in the hundreds. The of May 31, 1889, exemplified human-engineered vulnerabilities when the , a poorly maintained above , collapsed after heavy rains, unleashing 20 million tons of water that surged 14 miles downstream at speeds up to 40 mph. The deluge demolished the steel town, killing 2,209 people—including 99 entire families—and leaving 27,000 homeless amid debris fields equivalent to the flow of the . Investigations attributed the failure to structural neglect by the dam's affluent owners, including inadequate spillways and fishing modifications, sparking public outrage and advancements in dam safety regulations.
EventDateLocationEstimated DeathsKey Causes and Impacts
FloodSeptember 1887 (Henan et al.)900,000–2,000,000Dike breaches; 50,000 sq mi flooded, massive .
Winter 1861–1862, USAHundredsProlonged storms; valley inundation up to 30 ft deep.
May 31, 1889, USA2,209Dam failure; town destroyed, spurred engineering reforms.

20th Century Disasters

The 1931 floods in , primarily affecting the and basins, were precipitated by prolonged heavy rainfall exceeding 600 mm in some areas from to , compounded by earlier and inadequate maintenance. These events inundated approximately 52,000 square miles (135,000 square km), displacing up to 80 million people and destroying vast agricultural lands, with death toll estimates ranging from 1 million to 4 million due to , , and disease outbreaks like . The disaster's scale was exacerbated by and population pressures on river systems, leading to widespread collapse in provinces including , , and . The North Sea flood of January 31 to February 1, 1953, resulted from a generating a that peaked at over 5.6 meters above mean , coinciding with a high spring tide and overwhelming coastal defenses in the , , and . It caused approximately 2,500 deaths, including 1,836 in the where dikes failed across 160 km of coastline, flooding 9% of the country's land and displacing 400,000 residents. In the UK, 307 fatalities occurred mainly in eastern , with saltwater contamination ruining farmland and prompting post-event engineering reforms like the . Typhoon Nina's landfall on August 5, 1975, delivered record rainfall of up to 1,060 mm in 24 hours to , overwhelming the and 61 others, leading to catastrophic failures starting August 8. The Banqiao collapse released 492 million cubic meters of water in a wall up to 10 meters high, killing an estimated 85,000 to 240,000 people directly from flooding, with total casualties exceeding 145,000 including subsequent and epidemics; it impacted 11 million residents across 12,000 square km. Design flaws, such as underestimating maximum (the dam was rated for 500-year events but faced a probable 2,000-year ), and communication breakdowns during the delayed evacuations, destroying 6 million homes and 3 million hectares of farmland. Other significant 20th-century floods included the 1937 Ohio River flood , where record crests from January to March rains submerged 1,000 miles of river valley, killing 385 and leaving 1 million homeless across multiple states with damages equivalent to $10 billion in modern terms. , the 1910 Paris flood from Seine River overflow on January 21-28 submerged much of the city to depths of 7 meters, disrupting services for weeks but causing fewer than 100 direct deaths amid improved warnings. These events underscored vulnerabilities in both natural riverine systems and early engineered controls, often amplified by and persistence.

Events from 2000 to 2025

made landfall near New Orleans, Louisiana, on August 29, 2005, leading to catastrophic flooding when storm surges overwhelmed levees and floodwalls, submerging 80% of the city under up to 20 feet of water and causing 1,833 deaths across the , primarily from . The event resulted in approximately $125 billion in damages (adjusted for inflation), displacing over one million people and exposing vulnerabilities in coastal infrastructure and emergency response systems. In July and August 2010, unprecedented monsoon rains triggered the worst flooding in Pakistan's history, affecting 20 million people across five provinces, destroying 1.9 million homes, and inundating 17 million acres of cropland, with a death toll of 1,985. The floods, exacerbated by glacial melt and river overflows in the Indus basin, caused economic losses estimated at $10 billion and led to widespread outbreaks of waterborne diseases. Exceptionally heavy monsoon rainfall from June to August 2018 caused severe flooding in , , the worst in a century, killing 483 people, displacing 1.4 million, and damaging over 50,000 homes and 10,000 kilometers of roads. The disaster, which released 23% more rain than the long-term average due to climate patterns like La Niña, prompted the opening of 73 relief camps and highlighted risks from deforestation and dam management in the . Persistent heavy rains in summer 2020 led to widespread flooding across central and southern , particularly along the River basin, affecting 45.5 million people, causing 142 deaths or missing persons, and resulting in direct economic losses exceeding 100 billion yuan ($14 billion). The floods inundated 37 million hectares of farmland and forced the evacuation of millions, with urban areas like experiencing record water levels not seen since 1954. From July 12-15, 2021, intense prolonged rainfall in Western Europe, particularly Germany and Belgium, produced flash floods that killed at least 243 people—196 in Germany and 39 in Belgium—destroying thousands of homes and causing damages estimated at €46 billion. The event, linked to a stalled atmospheric low-pressure system, overwhelmed rivers like the Ahr, leading to the highest discharge rates in centuries and underscoring gaps in forecasting and early warning systems despite prior investments. Monsoon floods in from June to October 2022, driven by 760% above-average rainfall in province, resulted in over 1,700 deaths, affected 33 million people, and caused $30 billion in damages, submerging one-third of the country and destroying 2 million homes. The catastrophe, intensified by outbursts and , led to a with millions at risk of and , prompting international aid exceeding $3 billion. In the United States, Hurricane Helene in September 2024 caused severe inland flooding in the Appalachians, particularly , killing over 100 people and generating damages exceeding $50 billion, with record river crests in areas unaccustomed to impacts. Early 2025 floods in , linked to heavy rains, added to the tally of deadly events, contributing to heightened awareness of risks in urbanizing watersheds.

Controversies in Flood Attribution and Response

Debates on Climate Change Causality

The scientific community debates the extent to which anthropogenic climate change contributes to flood events, contrasting claims of increased intensity from heavier precipitation with empirical observations showing mixed or absent global trends in flood frequency and magnitude. The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report states high confidence that human-induced warming has intensified heavy precipitation events globally since the mid-20th century, consistent with thermodynamic scaling of about 7% more moisture per degree Celsius of warming, potentially elevating risks of pluvial (rainfall-driven) floods in smaller catchments. However, the same report expresses low confidence in long-term trends for river floods worldwide, noting significant regional variations such as earlier snowmelt-driven floods in cold regions (high confidence) but decreases in areas like the Mediterranean. Empirical analyses of global data reveal no robust increase in peak flood magnitudes or frequencies attributable to anthropogenic forcing. A study of U.S. floods from 1932–2009 found no statistical of rising magnitudes correlating with global mean CO2 concentrations across four regions, attributing variations instead to natural fluctuations and land-use changes. Globally, assessments of 20-, 50-, and 100-year floods indicate increases in temperate zones but decreases in arid, tropical, polar, and cold regions, yielding no net upward trend when aggregated. Hydrological modeling of historical annual maxima further supports stasis or declines in many basins, with future projections under warming scenarios showing amplified variability rather than uniform escalation. Critics, including climatologist Roger Pielke Jr., argue that media and policy narratives over-attribute floods to climate change absent detectable trends in normalized damages or event frequency, which have not risen disproportionately after adjusting for socioeconomic factors like population growth and infrastructure expansion. Natural climate variability, such as El Niño-Southern Oscillation phases, often dominates specific events; for instance, attribution studies of the 2021 European floods found anthropogenic signals inconclusive amid strong natural forcing. Non-climatic drivers exacerbate impacts, including urbanization's impervious surfaces amplifying runoff by up to 10-fold in affected areas and historical precedents of comparable floods predating modern warming, as evidenced by paleoclimate records exceeding instrumental maxima in Europe and Asia. Event attribution techniques, which probabilistically estimate human influence on individual floods via counterfactual modeling, face methodological critiques for high in isolating signals from noise, particularly in regions with sparse gauge networks or confounding land-management practices like wetland drainage. While some studies claim anthropogenic enhancement—for example, making certain European heavy rains 1.2–9 times more likely—these rely on model ensembles that may overestimate extremes relative to observations, and global syntheses show declining flood hazards in large river basins due to hydrological damping. This discord underscores a causal realism prioritizing verifiable detection over projected risks, with skeptics cautioning against distortions from unproven linkages amid biases in academic and media sourcing toward alarmist interpretations.

Critiques of Policy and Media Narratives

Critics argue that media coverage of floods frequently exaggerates the role of anthropogenic , conflating increased economic damages from floods—driven by greater , , and asset values—with rising meteorological intensity or frequency. For instance, normalized flood loss data , adjusted for and , show no significant upward trend in flood disaster losses over the past century, contradicting narratives of unprecedented escalation. Similarly, global analyses indicate that while flood reporting has increased due to better detection and development in vulnerable areas, empirical trends in flood magnitude do not uniformly support claims of climate-driven intensification, with some regions showing stability or declines when accounting for confounding factors like land-use changes. This selective emphasis persists despite acknowledgments in authoritative assessments, such as the IPCC's findings of no detectable global increase in frequency attributable to human-induced warming, highlighting a disconnect between and popularized accounts. Media outlets often fail to contextualize events with local causes, such as inadequate drainage or encroachment, instead framing isolated incidents as harbingers of systemic catastrophe, which can distort public and priorities. Flood policies, particularly subsidized insurance programs, face criticism for creating by underpricing risks, thereby incentivizing development in high-hazard zones. The U.S. (NFIP), established in 1968, has accumulated over $20 billion in debt as of 2023, largely from claims exceeding premiums after events like in 2005, which alone generated $16 billion in payouts. Subsidies, benefiting approximately 20% of policyholders with rates below actuarial full-risk levels, distort market signals and encourage repeated rebuilding in flood-prone areas, with some properties claiming payouts over 30 times. Reform efforts, such as the Biggert-Waters Act of 2012 aiming to phase out subsidies, have stalled due to political resistance from affected constituencies, perpetuating fiscal unsustainability projected to worsen with rising sea levels and storm exposures. Critics contend that such policies prioritize short-term relief over long-term resilience, neglecting alternatives like stricter or private markets that better reflect true hazards. In , analogous subsidies in programs like the UK's Flood Re have drawn similar rebukes for delaying adaptation by shielding property owners from full costs.

Cultural, Religious, and Etymological Dimensions

Flood Myths and Narratives Across Cultures

Flood narratives featuring cataclysmic deluges appear in the mythologies of diverse cultures worldwide, often depicting divine intervention to punish humanity, followed by survival through a favored individual or family and subsequent renewal of life. These stories share motifs such as advance warnings from deities, construction of vessels or shelters, preservation of animals or seeds, and post-flood offerings or repopulation efforts, though variations reflect local geographies and beliefs. Anthropological analyses suggest these tales may stem from memories of real prehistoric floods, such as post-glacial sea-level rises around 12,000–8,000 years ago or regional inundations, rather than a singular global event, with or independent invention explaining parallels. In Mesopotamian tradition, the (circa 2100–1200 BCE) recounts , warned by the god Ea of a flood ordained by to destroy humankind for overpopulation and noise; builds a cube-shaped ark, loads it with animals and family, survives 40 days of storm, and offers sacrifices post-deluge, earning immortality. An earlier version appears in the Atrahasis epic (circa 18th century BCE), emphasizing themes of divine regret over human creation. Archaeological layers of silt at sites like (circa 3500 BCE) and indicate major local floods that may have inspired these accounts. The Biblical account in Genesis 6–9 describes flooding the due to human wickedness, instructing righteous to construct a rectangular ark housing his family and pairs of animals; the deluge lasts 150 days, with waters prevailing for a year before receding, culminating in a covenant symbolized by the rainbow. While similarities to Mesopotamian tales exist—such as ark dimensions, bird releases, and sacrifices—differences include monotheistic causation, moral emphasis on , and global scope, leading some scholars to posit Israelite adaptation during Babylonian ( BCE), though others argue for an independent Hebrew tradition predating influences. Hindu texts like the Shatapatha Brahmana (circa 700–300 BCE) and Matsya Purana narrate Manu Vaivasvata, the progenitor of humanity, alerted by a divine fish (Vishnu's Matsya avatar) to an impending flood; he constructs a boat, ties it to the fish's horn, and preserves the Vedas, seeds of plants, family, and seven sages (Saptarishi) as the waters subside on Mount Himavat's peak. Unlike ark-based survival, the fish guides the vessel through the deluge, underscoring themes of dharma preservation over punishment. Greek mythology, as in Ovid's (1st century CE) drawing from earlier sources like , features , son of , and his wife surviving Zeus's flood—triggered by human impiety exemplified by Lycaon's —by floating in a chest for nine days; upon landing on , they repopulate earth by throwing stones that transform into humans, with Deucalion's becoming men and Pyrrha's women. This narrative echoes Prometheus's role in human creation via clay, paralleling Mesopotamian motifs but emphasizing repopulation mechanics over animal preservation. In Chinese lore, the Great Flood myth centers on (circa 2200–2100 BCE in tradition), tasked by to control rampant inundations ravaging farmlands; unlike deluge survivors, Yu rejects damming (as failed by his father ) and dredges channels, passes his son's birthplace thrice without entering, and demarcates over 13 years, earning the throne and founding the . Geological evidence supports massive flooding in the basin around 1920 BCE from overflow and seismic activity, framing Yu as an engineer-hero rather than a . Other cultures preserve variants, such as Mayan Popol Vuh tales of wooden people destroyed by flood for lacking reverence, or Australian Aboriginal stories of ancestral beings causing inundations during creation epochs, often tied to coastal submersion post-Ice Age. Comparative studies highlight core similarities in over 200 global flood legends—warning, vessel, survivors—but diverge in (punitive vs. natural) and resolution, with empirical data favoring localized historical floods over monocausal origins, critiquing diffusionist models for overlooking independent in isolated regions.

Etymology and Linguistic Evolution

The English word "flood" derives from Old English flōd, denoting "a flowing of water, tide, deluge, or river in flood," with attestations from before 1150. This form traces to Proto-Germanic \flōduz or \floduz, a neuter noun signifying flowing water or inundation. The ultimate root lies in Proto-Indo-European \pleu-, meaning "to flow," which also yields related terms like "flow" and "float" in English, reflecting a semantic core tied to liquid motion rather than exclusively catastrophic overflow. In other Germanic languages, cognates preserve similar connotations: Old High German fluot referred to a stream or flood, while Old Norse flóð indicated tide or deluge, both inheriting the Proto-Germanic sense of water's dynamic surge. These parallels underscore a shared evolution, where the term emphasized natural watercourses prone to swelling, as in riverine or tidal contexts, prior to broader Indo-European divergence around 4500–2500 BCE. Non-Germanic Indo-European branches lack direct equivalents for "flood" as inundation but share the \pleu- root in verbs for flowing, such as plavate ("to swim" or "flow"), indicating the concept's dispersal through migratory expansions without uniform nominal fixation. Linguistically, "flood" evolved conservatively in English: flod retained the and meaning, appearing in texts like the 14th-century for biblical deluges or earthly overflows. By the verb form's emergence before 1500, as in Symonie ("to flood" meaning to inundate), it extended metaphorically to abundance, such as "flood of words" by the 1600s, while the noun core stabilized around submergence of dry land, influenced by hydrological observations rather than mythic reinterpretation. Modern usage, post-1700, incorporates scientific precision in and , distinguishing "flood" from related terms like "inundation" (Latin-derived, emphasizing saturation) or "deluge" (biblical connotation of divine wrath). This trajectory reflects empirical adaptation to documented events, such as the 1530 floods chronicled in period accounts, over speculative etymological shifts.

References

  1. https://www.nssl.noaa.gov/education/svrwx101/floods/
  2. https://www.nesdis.noaa.gov/about/k-12-education/severe-weather/causes-of-floods
  3. https://www.usgs.gov/faqs/what-are-two-types-floods
  4. https://www.sciencedirect.com/science/article/pii/S2590061720300600
  5. https://www.rff.org/publications/explainers/flooding-in-the-united-states-101-causes-trends-and-impacts/
  6. https://www.thezebra.com/resources/research/natural-disaster-statistics/
  7. https://www.usgs.gov/water-science-school/science/floods-things-know
  8. https://www.weather.gov/mrx/flood_and_flash
  9. https://www.weather.gov/aprfc/terminology
  10. https://pubs.usgs.gov/wri/wri95-4289/wri95-4289_text.htm
  11. https://www.txdot.gov/manuals/des/hyd/chapter-4--hydrology/section-15--glossary-of-hydrology-terms.html
  12. https://www.usgs.gov/water-science-school/science/100-year-flood
  13. https://www.usgs.gov/water-science-school/science/floods-and-recurrence-intervals
  14. https://www.weather.gov/lot/hydrology_definitions
  15. https://www.nssl.noaa.gov/education/svrwx101/floods/faq/
  16. https://floodobservatory.colorado.edu/SatelliteGaugingSites/DFOFloodIndexExplanation.pdf
  17. http://www.ontario.ca/page/classification-and-inflow-design-flood-criteria
  18. https://pubs.usgs.gov/circ/2004/circ1254/pdf/circ1254.pdf
  19. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021JF006135
  20. https://www.mbari.org/project/the-zanclean-megaflood-the-largest-flood-in-the-history-of-earth/
  21. https://news.ucsc.edu/2022/02/missoula-megafloods/
  22. https://www.anu.edu.au/news/all-news/study-reveals-salty-secrets-of-mediterranean-megaflood
  23. https://www.nationalgeographic.com/history/article/zanclean-mega-flood-mediterranean-animated-video
  24. https://www.sciencedirect.com/science/article/abs/pii/S0012825219301540
  25. https://www.cambridge.org/core/books/megaflooding-on-earth-and-mars/megaflood-sedimentary-valley-fill-altai-mountains-siberia/5C75F38C16EB4F0E45CE051C8DC9C311
  26. https://www.sciencedirect.com/science/article/abs/pii/S1871101422001479
  27. https://www.usgs.gov/publications/missoula-and-bonneville-floods-a-review-ice-age-megafloods-columbia-river-basin
  28. https://pubs.usgs.gov/pp/0596/report.pdf
  29. https://www.pnas.org/doi/10.1073/pnas.2109502119
  30. https://www.sciencedirect.com/science/article/pii/0022169487901454
  31. http://www.riversimulator.org/Resources/Floods/QuantitativePaleofloodHydrology2020Benito.pdf
  32. https://pubs.geoscienceworld.org/gsa/books/book/275/chapter/3795280/Paleohydrology-and-Sedimentology-of-Lake-Missoula
  33. https://pubs.usgs.gov/of/1983/0671/report.pdf
  34. https://www.science.org/doi/10.1126/science.259.5093.348
  35. https://co.water.usgs.gov/projects/COFloodDB/docs/England_et_al_2010.pdf
  36. https://www.iclr.org/wp-content/uploads/2021/04/ICLR_Flooding_2021.pdf
  37. https://www.undrr.org/understanding-disaster-risk/terminology/hips/mh0604
  38. https://www.dontgoof.org/flood/river-flooding
  39. https://www.intermap.com/risks-of-hazard-blog/three-common-types-of-flood-explained
  40. https://www.nssl.noaa.gov/education/svrwx101/floods/types/
  41. https://www.floodinfo.ie/about_frm/types_and_causes/
  42. https://www.nationalfloodinsurance.org/flood-history/
  43. https://www.weather.gov/lmk/toptenfloodevents
  44. https://www.americanrivers.org/whats-the-biggest-flood-in-history/
  45. https://www.zurich.com/knowledge/topics/flood-and-water-damage/three-common-types-of-flood
  46. https://www.sciencedirect.com/science/article/pii/S2212420923002315
  47. https://descartesunderwriting.com/insights/understanding-global-weather-perils-flood-risk
  48. https://www.weather.gov/lmk/top10flash
  49. https://www.zurich.com/knowledge/topics/flood-and-water-damage/the-threat-from-above
  50. https://www.undrr.org/understanding-disaster-risk/terminology/hips/mh0601
  51. https://www.noaa.gov/storm-surge-overview
  52. https://www.weather.gov/mhx/UnderstandCoastalFlooding
  53. https://scied.ucar.edu/learning-zone/storms/what-causes-storm-surge
  54. https://www.sofarocean.com/posts/what-is-a-storm-surge-and-what-causes-it
  55. https://physicstoday.aip.org/features/modeling-the-physics-of-storm-surges
  56. https://www.weather.gov/lix/katrina_anniversary
  57. https://education.nationalgeographic.org/resource/flood/
  58. https://tidesandcurrents.noaa.gov/publications/NOAA_Technical_Report_NOS_COOPS_073.pdf
  59. https://www.weather.gov/phi/stormsurge
  60. https://vlab.noaa.gov/web/mdl/storm-surge-events
  61. https://repository.oceanbestpractices.org/bitstream/handle/11329/393/wmo_1076_en.pdf?sequence=1&isAllowed=y
  62. https://npdp.stanford.edu/sites/default/files/reports/npdp_dam_failure_summary_compilation_v1_2018.pdf
  63. https://www.sms-tsunami-warning.com/pages/world_deadliest_dam_failures
  64. https://www.britannica.com/event/Typhoon-Nina-Banqiao-dam-failure
  65. https://www.worldatlas.com/articles/the-deadliest-dam-failures-in-history.html
  66. https://ejatlas.org/conflict/baquio-dam-failure-henan-china
  67. https://yaleclimateconnections.org/2025/07/the-deadliest-floods-in-u-s-history/
  68. https://vlab.noaa.gov/web/nws-heritage/-/tragedy-at-teton-1976-dam-break-disaster
  69. https://web.mst.edu/~rogersda/teton_dam/index.htm
  70. https://www.usbr.gov/pn/snakeriver/dams/uppersnake/teton/index.html
  71. https://essd.copernicus.org/articles/15/2983/2023/
  72. https://www.nature.com/articles/s41467-023-36033-x
  73. https://www.antarcticglaciers.org/glaciers-and-climate/glacier-hazards/glacial-lake-outburst-floods/
  74. https://damfailures.org/sites/default/files/wp-pdf/ASDSO-Vajont_Mauney_Graham.pdf
  75. https://www.britannica.com/topic/Vaiont-Dam
  76. https://www.noaa.gov/jetstream/thunderstorms/flood
  77. https://www.usgs.gov/science/science-explorer/natural-hazards
  78. https://www.usgs.gov/observatories/cvo/science/excess-sediment-accumulation-causes-flooding-cascades
  79. https://pubs.usgs.gov/pp/1240b/report.pdf
  80. https://www.usgs.gov/water-science-school/science/impervious-surfaces-and-flooding
  81. https://link.springer.com/article/10.1007/s11069-020-04480-0
  82. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL086480
  83. https://www.unsw.edu.au/newsroom/news/2025/10/Deforestation-eight-fold-increase-flood-event-risk
  84. https://www.sciencedirect.com/science/article/abs/pii/S1040618216308357
  85. https://andrewsforest.oregonstate.edu/pubs/pdf/pub5256.pdf
  86. https://www.nature.com/articles/s44304-024-00002-1
  87. https://www.sciencedaily.com/releases/2016/01/160106114744.htm
  88. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002%252F2017WR020723
  89. https://www.nature.com/articles/d41586-023-03962-y
  90. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021GL097706
  91. https://www.epa.gov/climate-indicators/climate-change-indicators-river-flooding
  92. https://esd.copernicus.org/articles/9/757/2018/
  93. https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-11/
  94. https://rogerpielkejr.[substack](/page/Substack).com/p/unbelievable-us-flood-damage
  95. https://journals.ametsoc.org/view/journals/clim/13/20/1520-0442_2000_013_3625_padfti_2.0.co_2.pdf
  96. https://progearthplanetsci.springeropen.com/articles/10.1186/s40645-021-00431-w
  97. https://www.tandfonline.com/doi/full/10.1080/02626667.2011.621895
  98. https://www.sciencedirect.com/science/article/abs/pii/S0022169423001786
  99. https://rogerpielkejr.substack.com/p/climate-change-is-showing-its-claws
  100. https://hydrology.usu.edu/rrp/pdfs/ch2.pdf
  101. https://www.tucson.ars.ag.gov/unit/publications/PDFfiles/1696.pdf
  102. https://pmc.ncbi.nlm.nih.gov/articles/PMC7433200/
  103. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2014WR016308
  104. https://hydrology.usu.edu/rrp/pdfs/ch3.pdf
  105. https://fiveable.me/hydrology/unit-8/factors-affecting-runoff-generation/study-guide/JSBg8TtHYwKC9HM6
  106. https://blog.datalabs.info/blog/718
  107. https://www2.tulane.edu/~sanelson/eens1110/streams.htm
  108. https://journals.ametsoc.org/view/journals/hydr/24/1/JHM-D-22-0117.1.xml
  109. https://www.nature.com/articles/s41598-020-61533-x
  110. https://pubs.usgs.gov/pp/0252/report.pdf
  111. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GL111789
  112. https://www.sciencedirect.com/science/article/pii/S0169555X24004227
  113. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010WR010375
  114. https://www.sciencedirect.com/science/article/abs/pii/S0895981123001074
  115. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022WR033714
  116. https://extension.sdstate.edu/global-and-us-perspectives-flooding
  117. https://science.howstuffworks.com/nature/natural-disasters/worst-flood-in-history.htm
  118. https://www.ketv.com/article/get-the-facts-deadliest-floods-in-the-us/65321053
  119. https://www.undrr.org/gar/gar2025/hazard-exploration/floods
  120. https://www.frontiersin.org/journals/built-environment/articles/10.3389/fbuil.2024.1357741/full
  121. https://www.sciencedirect.com/science/article/pii/S2590332224001398
  122. https://news.umich.edu/traditional-infrastructure-design-often-makes-extreme-flooding-events-worse/
  123. https://www.statista.com/topics/11261/floods/
  124. https://www.statista.com/statistics/1116782/major-floods-us-economic-cost/
  125. https://floodadvisoryservice.co.uk/the-environmental-impact-of-recurring-floods-on-ecosystems/
  126. https://www.emdat.be/
  127. https://hal.science/hal-05004422v1/file/ENGLISH%2520VERSION%2520Copie%2520de%2520INONDATIONS%2520nondations%2520Saisonnieres%2520rev%2520Ez%25C3%25A9.pdf
  128. https://education.nationalgeographic.org/resource/many-effects-flooding/
  129. https://pubs.usgs.gov/fs/fs07603/
  130. https://www.aquaread.com/blog/how-flooding-affects-water-quality/
  131. https://www.theenvironmentalblog.org/2023/04/the-link-between-flooding-and-biodiversity-loss/
  132. https://www.theguardian.com/environment/2020/apr/01/the-losses-could-be-profound-how-floods-are-wreaking-havoc-on-wildlife-aoe
  133. https://www.sciencedirect.com/science/article/pii/S1470160X23006477
  134. https://pmc.ncbi.nlm.nih.gov/articles/PMC6404734/
  135. https://extension.sdstate.edu/managing-soil-and-soil-fertility-after-flooding
  136. https://www.floodmanagement.info/what-are-the-beneficial-impacts-of-floods/
  137. https://reasonstobecheerful.world/flood-recession-farming-india/
  138. http://www.conservationgateway.org/ConservationPractices/Freshwater/HabitatProtectionandRestoration/Pages/floodofbenefits.aspx
  139. https://water.ca.gov/News/Blog/2022/Aug-22/How-Aquifer-Recharge-Reduces-Flood-Risk
  140. https://www.mywaltonfl.gov/733/Natural-Beneficial-Functions-of-Floodpla
  141. https://www.noaa.gov/sites/default/files/legacy/document/2020/Oct/07354626338.pdf
  142. https://www.mdpi.com/2073-4441/16/13/1763
  143. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019WR025583
  144. https://www.sciencedirect.com/science/article/pii/S2214581819300679
  145. https://www.researchgate.net/figure/Classification-of-models-used-for-Flood-Forecasting-based-on-model-structure-and-type_fig5_321650650
  146. https://www.mdpi.com/2306-5338/10/7/141
  147. https://iwaponline.com/jwcc/article/14/10/3496/97827/Flood-simulation-using-the-hydrological-model-and
  148. https://www.scirp.org/journal/paperinformation?paperid=103729
  149. https://www.researchgate.net/publication/367100278_Comparison_of_SWAT_and_HEC-HMS_model_performance_in_simulating_catchment_runoff
  150. https://www.sciencedirect.com/science/article/abs/pii/S0022169425000125
  151. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2025AV001678
  152. https://www.mdpi.com/2306-5338/12/3/51
  153. https://www.usgs.gov/centers/new-jersey-water-science-center/floods-recurrence-intervals-and-100-year-floods
  154. https://pubs.usgs.gov/tm/04/b05/tm4b5old.pdf
  155. https://serc.carleton.edu/hydromodules/steps/168500.html
  156. https://water.usgs.gov/osw/bulletin17b/dl_flow.pdf
  157. https://streamflow.engr.oregonstate.edu/analysis/floodfreq/
  158. https://pubs.usgs.gov/tm/04/b06/tm4b6.pdf
  159. https://www.hec.usace.army.mil/publications/ResearchDocuments/RD-47.pdf
  160. https://pmc.ncbi.nlm.nih.gov/articles/PMC6108001/
  161. https://onlinelibrary.wiley.com/doi/10.1111/jfr3.12739
  162. https://pubs.usgs.gov/wsp/1580a/report.pdf
  163. https://www.fathom.global/insight/ai-machine-learning-flood-modeling/
  164. https://www.sciencedirect.com/science/article/abs/pii/S002216942501412X
  165. https://www.sciencedirect.com/science/article/pii/S1569843225003486
  166. https://www.mdpi.com/2504-446X/9/3/191
  167. https://pmc.ncbi.nlm.nih.gov/articles/PMC11548130/
  168. https://www.mdpi.com/2076-3417/15/13/7563
  169. https://www.ctc-n.org/technologies/structural-barriers-flooding-dams-dikes-locks-and-leeves
  170. https://utcrops.com/wp-content/uploads/2021/01/Mississippi-River-and-Tribs_V2.pdf
  171. https://trapbag.com/blog/flood-control-methods/
  172. https://www.hydropower.org/blog/flood-control-three-gorges-project
  173. https://www.gov.uk/guidance/the-thames-barrier
  174. https://www.ice.org.uk/news-views-insights/inside-infrastructure/the-past-present-and-future-of-the-thames-barrier
  175. https://www.holland.com/global/tourism/getting-around/interests/land-of-water/delta-works
  176. https://www.wbal.com/when-disaster-strikes-5-of-americas-most-destructive-infrastructure-failures-caught-on-camera
  177. https://www.mvk.usace.army.mil/Missions/Programs-and-Project-Management/Project-Management/Mississippi-River-Levees-Project/
  178. https://stormwater.wef.org/2025/01/manhattan-looks-to-the-future-with-integrated-flood-protection/
  179. https://hazards.colorado.edu/mitigation-matters-report/zoning-for-flood-risk-reduction-in-five-virginia-communities
  180. https://www.mdpi.com/2073-445X/12/8/1631
  181. https://www.mapc.org/planning101/zoning-for-flood-resilience/
  182. https://www.floodmanagement.info/publications/casestudies/cs_usa_mississippi_sum.pdf
  183. https://www.fema.gov/flood-maps
  184. https://www.sciencedirect.com/science/article/abs/pii/S0301479723018133
  185. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021EF002491
  186. https://www.environmentandsociety.org/arcadia/north-sea-flood-1953
  187. https://www.iadc-dredging.com/wp-content/uploads/2017/03/article-from-disaster-to-delta-project-the-storm-flood-of-1953-90-01.pdf
  188. https://www.aveva.com/en/our-industrial-life/type/article/how-the-netherlands-became-the-global-leader-in-flood-defense/
  189. https://www.asianometry.com/p/how-china-dammed-the-yellow-river
  190. https://pmc.ncbi.nlm.nih.gov/articles/PMC3472015/
  191. https://www.scmp.com/news/china/science/article/3211119/chinas-yellow-river-flooded-10-times-more-often-past-millennium-new-study-finds-out-why
  192. https://www.asce.org/publications-and-news/civil-engineering-source/civil-engineering-magazine/article/2015/07/the-lessons-of-katrina
  193. https://www2.tulane.edu/~sanelson/New_Orleans_and_Hurricanes/overviewofleveefailures.pdf
  194. https://news.gatech.edu/news/2025/08/19/twenty-years-after-katrina-how-levee-failures-changed-america
  195. https://english.deltaprogramma.nl/three-topics/flood-risk-management/delta-plan
  196. https://www.nature.com/articles/s41586-022-04917-5
  197. https://www.mdpi.com/2225-1154/12/5/67
  198. https://www.britannica.com/event/Huang-He-floods
  199. https://engines.egr.uh.edu/episode/1626
  200. https://www.evergladesuniversity.edu/blog/worst-disasters-in-us-history/
  201. https://www.nps.gov/jofl/
  202. https://www.history.com/this-day-in-history/may-31/the-johnstown-flood
  203. https://www.history.com/this-day-in-history/august-25/yangtze-river-peaks-in-china
  204. https://journals.ametsoc.org/view/journals/clim/36/18/JCLI-D-22-0771.1.xml
  205. https://study.com/academy/lesson/video/1931-china-floods-facts-causes-aftermath.html
  206. https://www.britannica.com/science/Yangtze-River-floods
  207. https://www.britannica.com/event/North-Sea-flood
  208. https://hazards.colorado.edu/article/the-1953-north-sea-flood-in-the-netherlands-impact-and-aftermath
  209. https://www.bbc.com/news/uk-england-lincolnshire-64414388
  210. https://damsafety.org/reference/dam-failure-case-study-banqiao-dam-china-1975
  211. https://damfailures.org/sites/default/files/wp-pdf/The-Worlds-Most-Catastrophic-Dam-Failures_Banqiao-1.pdf
  212. https://pubs.usgs.gov/fs/2000/0024/report.pdf
  213. https://ourworldindata.org/natural-disasters
  214. https://www.ncei.noaa.gov/access/billions/
  215. https://www.britannica.com/event/Pakistan-Floods-of-2010
  216. https://earthobservatory.nasa.gov/features/PakistanFloods
  217. https://journals.lww.com/wpsy/fulltext/2020/02030/immediate_mental_health_response_to_kerala_floods.7.aspx
  218. https://www.bbc.com/news/world-asia-india-45216671
  219. https://pmc.ncbi.nlm.nih.gov/articles/PMC8454574/
  220. https://give2asia.org/report-china-flood-relief-2020/
  221. https://climate.copernicus.eu/esotc/2021/flooding-july
  222. https://pmc.ncbi.nlm.nih.gov/articles/PMC9772704/
  223. https://www.aljazeera.com/news/longform/2022/9/16/mapping-the-scale-of-destruction-of-the-pakistan-floods
  224. https://www.pbs.org/newshour/show/death-toll-in-pakistan-passes-1110-as-monsoon-floods-reach-historic-levels
  225. https://apnews.com/article/flood-deaths-flash-flooding-weather-408b11abe0389f38c93d8722b9d15dd0
  226. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020GL091824
  227. https://hess.copernicus.org/articles/24/1543/2020/
  228. https://rogerpielkejr.substack.com/p/series-what-the-media-wont-tell-you-3b0
  229. https://esd.copernicus.org/articles/15/225/2024/
  230. https://e360.yale.edu/features/its-not-just-climate-are-we-ignoring-other-causes-of-disasters
  231. https://www.scientificamerican.com/article/when-disaster-strikes-is-climate-change-to-blame/
  232. https://www.bbc.com/news/articles/cn5zx2zx5xvo
  233. https://www.scienceunderattack.com/blog/2019/7/1/no-evidence-that-climate-change-causes-weather-extremes-2-floods-29
  234. https://rogerpielkejr.substack.com/p/disasters-cost-more-than-ever-but
  235. https://rogerpielkejr.substack.com/p/dont-believe-the-hype
  236. https://www.nature.com/articles/s44304-024-00011-0
  237. https://thebreakthrough.org/issues/energy/ipcc-sides-with-roger-pielke-jr
  238. https://www.heritage.org/climate/commentary/twisting-the-truth-extreme-weather-and-the-climate-narrative
  239. https://www.motherjones.com/politics/2023/12/national-flood-insurance-program-debt-mismanagment-fema-private-brokers/
  240. https://chicagopolicyreview.org/2025/02/25/the-national-flood-insurance-program-is-unsustainable-and-regressive/
  241. https://www.cato.org/policy-analysis/national-flood-insurance-program-solving-congresss-samaritans-dilemma
  242. https://www.gao.gov/blog/wave-concerns-facing-national-flood-insurance-program
  243. https://jpia.princeton.edu/news/overcoming-contemporary-reform-failure-national-flood-insurance-program-accelerate-just-climate
  244. https://www.cato.org/regulation/fall-2015/unintended-effects-government-subsidized-weather-insurance
  245. https://www.sciencedirect.com/science/article/abs/pii/S0095069621001170
  246. https://nautil.us/the-real-landscapes-of-the-great-flood-myths-235476/
  247. https://bigthink.com/high-culture/flood-myth-origin/
  248. https://www.thetorah.com/article/the-mesopotamian-origin-of-the-biblical-flood-story
  249. https://ncse.ngo/flood-mesopotamian-archaeological-evidence
  250. https://www.icr.org/content/flood-noah-and-flood-gilgamesh
  251. https://answersingenesis.org/the-flood/flood-legends/myth-flood-myth/
  252. https://www.ancient-origins.net/human-origins-religions/startling-similarity-between-hindu-flood-legend-manu-and-biblical-020318
  253. https://www.pbs.org/independentlens/blog/a-flood-of-myths-and-stories/
  254. https://www.theoi.com/Heros/Deukalion.html
  255. https://answersingenesis.org/the-flood/flood-legends/does-bible-borrow-greek-flood-legend/
  256. https://www.ancient-origins.net/myths-legends/gun-yu-and-chinese-flood-myth-00370
  257. https://thechinaproject.com/2020/08/24/yu-the-great-tamer-of-chinas-greatest-floods/
  258. https://digitalcommons.cedarville.edu/cgi/viewcontent.cgi?article=1200&context=icc_proceedings
  259. https://answersingenesis.org/the-flood/flood-legends/
  260. https://www.etymonline.com/word/flood
  261. https://www.oed.com/dictionary/flood_n
  262. https://www.yourdictionary.com/flood
  263. https://www.merriam-webster.com/dictionary/flood
  264. https://cooljugator.com/etymology/en/flood
  265. https://en.wiktionary.org/wiki/flood
  266. https://www.oed.com/dictionary/flood_v
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