Flood

Flood

Overview

A flood is an overflow of an expanse of water that submerges land. The EU Floods directive
Floods directive
DIRECTIVE 2007/60/EC of the European Parliament and of the Council of 23 October 2007 on the assessment and management of flood risks is commonly known as the ‘Floods Directive’....

 defines a flood as a temporary covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

.
Flooding may result from the volume of water within a body of water, such as a river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 or lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries.

While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area.

Floods can also occur in rivers, when flow exceeds the capacity of the river channel, particularly at bends or meanders.
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Timeline

1874   A flood on the Mill River in Massachusetts destroys much of four villages and kills 139 people.

1970   In Vietnam, the worst monsoon to hit the area in six years causes large floods, kills 293, leaves 200,000 homeless and virtually halts the Vietnam War.

1996   Storms provoke severe flooding on the Saguenay River, beginning one of Quebec's costliest natural disasters ever.

2004   Hurricane Jeanne: At least 1,070 in Haiti are reported to have been killed by floods.

 
Encyclopedia

A flood is an overflow of an expanse of water that submerges land. The EU Floods directive
Floods directive
DIRECTIVE 2007/60/EC of the European Parliament and of the Council of 23 October 2007 on the assessment and management of flood risks is commonly known as the ‘Floods Directive’....

 defines a flood as a temporary covering by water of land not normally covered by water. In the sense of "flowing water", the word may also be applied to the inflow of the tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

.
Flooding may result from the volume of water within a body of water, such as a river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 or lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

, which overflows or breaks levees, with the result that some of the water escapes its usual boundaries.

While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, it is not a significant flood unless such escapes of water endanger land areas used by man like a village, city or other inhabited area.

Floods can also occur in rivers, when flow exceeds the capacity of the river channel, particularly at bends or meanders. Floods often cause damage to homes and businesses if they are placed in natural flood plains of rivers. While flood damage can be virtually eliminated by moving away from rivers and other bodies of water, since time out of mind, people have lived and worked by the water to seek sustenance and capitalize on the gains of cheap and easy travel and commerce by being near water. That humans continue to inhabit areas threatened by flood damage is evidence that the perceived value of living near the water exceeds the cost of repeated periodic flooding.

The word "flood" comes from the Old English
Old English language
Old English or Anglo-Saxon is an early form of the English language that was spoken and written by the Anglo-Saxons and their descendants in parts of what are now England and southeastern Scotland between at least the mid-5th century and the mid-12th century...

 flod, 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). Deluge myths are mythical
Mythology
The term mythology can refer either to the study of myths, or to a body or collection of myths. As examples, comparative mythology is the study of connections between myths from different cultures, whereas Greek mythology is the body of myths from ancient Greece...

 stories of a great flood sent by a deity
Deity
A deity is a recognized preternatural or supernatural immortal being, who may be thought of as holy, divine, or sacred, held in high regard, and respected by believers....

 or deities to destroy civilization
Civilization
Civilization is a sometimes controversial term that has been used in several related ways. Primarily, the term has been used to refer to the material and instrumental side of human cultures that are complex in terms of technology, science, and division of labor. Such civilizations are generally...

 as an act of divine retribution
Divine retribution
Divine retribution is supernatural punishment of a person, a group of people, or all humanity by a deity in response to some human action.Many cultures have a story about how a deity exacted punishment on previous inhabitants of their land, causing their doom.An example of divine retribution is the...

, and are featured in the mythology of many culture
Culture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...

s.

Riverine

  • Slow kinds: Runoff from sustained rainfall or rapid snow melt exceeding the capacity of a river's channel. Causes include heavy rains from monsoon
    Monsoon
    Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...

    s, hurricanes and tropical depressions, foreign winds and warm rain affecting snow pack. Unexpected drainage obstructions such as landslide
    Landslide
    A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

    s, ice
    Ice
    Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

    , or debris
    Debris
    Debris is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, or, in geology, large rock fragments left by a melting glacier etc. The singular form of debris is debris...

     can cause slow flooding upstream of the obstruction.
  • Fast kinds: include flash floods resulting from convective precipitation (intense thunderstorm
    Thunderstorm
    A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

    s) or sudden release from an upstream impoundment created behind a dam
    Dam
    A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

    , landslide
    Landslide
    A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

    , or glacier
    Glacier
    A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

    .

Estuarine

  • Commonly caused by a combination of sea tidal surges caused by storm-force winds. A storm surge
    Storm surge
    A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...

    , from either a tropical cyclone
    Tropical cyclone
    A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

     or an extratropical cyclone
    Extratropical cyclone
    Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...

    , falls within this category.

Coastal

  • Caused by severe sea storms, or as a result of another hazard (e.g. tsunami
    Tsunami
    A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...

     or hurricane). A storm surge
    Storm surge
    A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...

    , from either a tropical cyclone
    Tropical cyclone
    A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...

     or an extratropical cyclone
    Extratropical cyclone
    Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...

    , falls within this category.

Catastrophic

  • Caused by a significant and unexpected event e.g. dam
    Dam
    A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

     breakage, or as a result of another hazard (e.g. earthquake
    Earthquake
    An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

     or volcanic eruption).

Muddy

  • A muddy flood
    Muddy flood
    A muddy flood is produced by an accumulation of runoff generated on cropland. Sediments are then detached by runoff and carried as suspended matter or bedload...

     is produced by an accumulation of runoff generated on cropland. Sediments are then detached by runoff and carried as suspended matter or bed load. Muddy runoff is more likely detected when it reaches inhabited areas. Muddy floods are therefore a hill slope process, and confusion with mudflows produced by mass movements should be avoided.

Other

  • Floods can occur if water accumulates across an impermeable surface (e.g. from rainfall) and cannot rapidly dissipate (i.e. gentle orientation or low evaporation).
  • A series of storms moving over the same area.
  • Dam
    Dam
    A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

    -building beaver
    Beaver
    The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...

    s can flood low-lying urban and rural areas, often causing significant damage.

Primary effects

  • Physical damage – Can damage any type of structure, including bridges, cars, buildings, sewerage
    Sewerage
    Sewerage refers to the infrastructure that conveys sewage. It encompasses receiving drains, manholes, pumping stations, storm overflows, screening chambers, etc. of the sanitary sewer...

     systems, roadways, and canal
    Canal
    Canals are man-made channels for water. There are two types of canal:#Waterways: navigable transportation canals used for carrying ships and boats shipping goods and conveying people, further subdivided into two kinds:...

    s.

Secondary effects

  • Water suppliesContamination of water
    Water pollution
    Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....

    . Clean drinking water
    Drinking water
    Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...

     becomes scarce.
  • Diseases – Unhygienic conditions. Spread of water-borne diseases.
  • Crops and food supplies – Shortage of food crops can be caused due to loss of entire harvest. However, lowlands near rivers depend upon river silt deposited by floods in order to add nutrients to the local soil.
  • Trees – Non-tolerant species can die from suffocation.
  • Transport - Transport links destroyed, so hard to get emergency aid to those who need it.

Tertiary/long-term effects


Economic – Economic hardship, due to: temporary decline in tourism, rebuilding costs, food shortage leading to price increase, etc.

Control





In many countries across the world, rivers prone to floods are often carefully managed. Defenses such as levee
Levee
A levee, levée, dike , embankment, floodbank or stopbank is an elongated naturally occurring ridge or artificially constructed fill or wall, which regulates water levels...

s, bunds
Bunding
Bunding, also called a bund wall, is the area within a structure designed to prevent inundation or breaches of various types.-Liquid containment:...

, reservoirs, and weir
Weir
A weir is a small overflow dam used to alter the flow characteristics of a river or stream. In most cases weirs take the form of a barrier across the river that causes water to pool behind the structure , but allows water to flow over the top...

s are used to prevent rivers from bursting their banks. When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are used. Coastal flooding has been addressed in Europe and the Americas with coastal defences
Coastal management
In some jurisdictions the terms sea defense and coastal protection are used to mean, respectively, defense against flooding and erosion...

, such as sea walls, beach nourishment
Beach nourishment
Beach nourishment— also referred to as beach replenishment—describes a process by which sediment lost through longshore drift or erosion is replaced from sources outside of the eroding beach...

, and barrier island
Barrier island
Barrier islands, a coastal landform and a type of barrier system, are relatively narrow strips of sand that parallel the mainland coast. They usually occur in chains, consisting of anything from a few islands to more than a dozen...

s.

Europe


Remembering the misery and destruction caused by the 1910 Great Flood of Paris
1910 Great Flood of Paris
The 1910 Great Flood of Paris was a catastrophe in which the Seine River, carrying winter rains from its tributaries, flooded Paris, France, and several nearby communities....

, the French government built a series of reservoirs called Les Grands Lacs de Seine (or Great Lakes) which helps remove pressure from the Seine
Seine
The Seine is a -long river and an important commercial waterway within the Paris Basin in the north of France. It rises at Saint-Seine near Dijon in northeastern France in the Langres plateau, flowing through Paris and into the English Channel at Le Havre . It is navigable by ocean-going vessels...

 during floods, especially the regular winter flooding.

London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...

 is protected from sea flooding by the Thames Barrier
Thames Barrier
The Thames Barrier is the world's second-largest movable flood barrier and is located downstream of central London. Its purpose is to prevent London from being flooded by exceptionally high tides and storm surges moving up from the sea...

, a huge mechanical barrier across the River Thames
River Thames
The River Thames flows through southern England. It is the longest river entirely in England and the second longest in the United Kingdom. While it is best known because its lower reaches flow through central London, the river flows alongside several other towns and cities, including Oxford,...

, which is raised when the sea water level reaches a certain point.

Venice
Venice
Venice is a city in northern Italy which is renowned for the beauty of its setting, its architecture and its artworks. It is the capital of the Veneto region...

 has a similar arrangement, although it is already unable to cope with very high tides; a new system of variable-height dikes is under construction. The defences of both London and Venice would be rendered inadequate if sea levels were to rise.

The Adige
Adige
The Adige is a river with its source in the Alpine province of South Tyrol near the Italian border with Austria and Switzerland. At in length, it is the second longest river in Italy, after the River Po with ....

 in Northern Italy was provided with an underground canal that allows to drain part of its flow into the Garda Lake (in the Po
Po River
The Po |Ligurian]]: Bodincus or Bodencus) is a river that flows either or – considering the length of the Maira, a right bank tributary – eastward across northern Italy, from a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face...

 drainage basin), thus lessening the risk of estuarine floods. The underground canal has been used twice, in 1966 and 2000.

The largest and most elaborate flood defences
Flood control in the Netherlands
Flood control in the Netherlands is an important issue for the Netherlands as about two thirds of the country is vulnerable to flooding while at the same time the country is among the most densely populated on earth. Natural sand dunes and man made dikes, dams and floodgates provide defense against...

 can be found in the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, where they are referred to as Delta Works
Delta Works
The Delta Works is a series of construction projects in the southwest of the Netherlands to protect a large area of land around the Rhine-Meuse-Scheldt delta from the sea. The works consist of dams, sluices, locks, dikes, levees, and storm surge barriers...

 with the Oosterschelde
Oosterschelde
The Oosterschelde is an estuary in Zeeland, Netherlands, between Schouwen-Duiveland and Tholen on the north and Noord-Beveland and Zuid-Beveland on the south.During the Roman Era it was the major mouth of the Scheldt River. Before the St...

 dam as its crowning achievement. These works were built in response to the North Sea flood of 1953
North Sea flood of 1953
The 1953 North Sea flood was a major flood caused by a heavy storm, that occurred on the night of Saturday 31 January 1953 and morning of 1 February 1953. The floods struck the Netherlands, Belgium, England and Scotland.A combination of a high spring tide and a severe European windstorm caused a...

 of the southwestern part of the Netherlands. The Dutch had already built one of the world's largest dams in the north of the country: the Afsluitdijk
Afsluitdijk
The Afsluitdijk is a major causeway in the Netherlands, constructed between 1927 and 1933 and running from Den Oever on Wieringen in North Holland province, to the village of Zurich in Friesland province, over a length of and a width of 90 m, at an initial height of 7.25 m above sea-level.It is...

 (closing occurred in 1932).

Currently the Saint Petersburg Flood Prevention Facility Complex
Saint Petersburg Dam
The Saint Petersburg Flood Prevention Facility Complex , unofficially the Saint Petersburg Dam, is a complex of dams for flood control near Saint Petersburg, Russia...

 is to be finished by 2008, in Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, to protect Saint Petersburg
Saint Petersburg
Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...

 from storm surge
Storm surge
A storm surge is an offshore rise of water associated with a low pressure weather system, typically tropical cyclones and strong extratropical cyclones. Storm surges are caused primarily by high winds pushing on the ocean's surface. The wind causes the water to pile up higher than the ordinary sea...

s. It also has a main traffic function, as it completes a ring road around Saint Petersburg. Eleven dams extend for 25.4 kilometres and stand eight metres above water level.

In Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

, flooding for over 150 years, has been controlled by various actions of the Vienna Danube regulation
Vienna Danube regulation
The Vienna Danube regulation refers to estensive flood-control engineering along the Danube river in Vienna, Austria during the last 150 years. The first major dams or levees were built during 1870-75. Another major project was constructed during 1972-88, which created the New Danube and Danube...

, with dredging of the main Danube
Danube
The Danube is a river in the Central Europe and the Europe's second longest river after the Volga. It is classified as an international waterway....

 during 1870–75, and creation of the New Danube
New Danube
The New Danube is a side channel on the eastern side of the Danube in Vienna, Austria. It was created to provide flood relief by containing excess water. The Donauinsel , made out of the removed material, separates the new waterway from the main channel of the river...

 from 1972–1988.

In Northern Ireland flood risk management is provided by Rivers Agency
Rivers Agency
The Rivers Agency is an Executive Agency of the Department of Agriculture and Rural Development . It is the statutory drainage and flood defence authority for Northern Ireland. DARD is the competent authority for the implementation of the EU Floods directive and has deligated the day to day...

.

North America


Another elaborate system of floodway defences can be found in the Canadian province of Manitoba
Manitoba
Manitoba is a Canadian prairie province with an area of . The province has over 110,000 lakes and has a largely continental climate because of its flat topography. Agriculture, mostly concentrated in the fertile southern and western parts of the province, is vital to the province's economy; other...

. The Red River
Red River of the North
The Red River is a North American river. Originating at the confluence of the Bois de Sioux and Otter Tail rivers in the United States, it flows northward through the Red River Valley and forms the border between the U.S. states of Minnesota and North Dakota before continuing into Manitoba, Canada...

 flows northward from the United States, passing through the city of Winnipeg
Winnipeg
Winnipeg is the capital and largest city of Manitoba, Canada, and is the primary municipality of the Winnipeg Capital Region, with more than half of Manitoba's population. It is located near the longitudinal centre of North America, at the confluence of the Red and Assiniboine Rivers .The name...

 (where it meets the Assiniboine River
Assiniboine River
The Assiniboine River is a river that runs through the prairies of Western Canada in Saskatchewan and Manitoba. It is a tributary of the Red River. The Assiniboine is a typical meandering river with a single main channel embanked within a flat, shallow valley in some places and a steep valley in...

) and into Lake Winnipeg
Lake Winnipeg
Lake Winnipeg is a large, lake in central North America, in the province of Manitoba, Canada, with its southern tip about north of the city of Winnipeg...

. As is the case with all north-flowing rivers in the temperate zone of the Northern Hemisphere, snowmelt in southern sections may cause river levels to rise before northern sections have had a chance to completely thaw. This can lead to devastating flooding, as occurred in Winnipeg during the spring of 1950. To protect the city from future floods, the Manitoba government undertook the construction of a massive system of diversions, dikes, and floodways (including the Red River Floodway
Red River Floodway
The Red River Floodway is an artificial flood control waterway in Western Canada, first used in 1969. It is a long channel which, during flood periods, takes part of the Red River's flow around the city of Winnipeg, Manitoba to the east and discharges it back into the Red River below the dam at...

 and the Portage Diversion
Portage Diversion
The Portage Diversion is a water control structure on the Assiniboine River in Portage la Prairie, Manitoba, Canada. The project was made as part of a larger attempt to prevent flooding in the Red River Valley...

). The system kept Winnipeg safe during the 1997 flood that devastated many communities upriver from Winnipeg, including Grand Forks, North Dakota
Grand Forks, North Dakota
Grand Forks is the third-largest city in the U.S. state of North Dakota and the county seat of Grand Forks County. According to the 2010 census, the city's population was 52,838, while that of the city and surrounding metropolitan area was 98,461...

 and Ste. Agathe, Manitoba
Ste. Agathe, Manitoba
Ste. Agathe is a primarily francophone community in the Canadian province of Manitoba. It is located along the Red River in the Rural Municipality of Ritchot....

. It also kept Winnipeg safe during the 2009 flood
2009 Red River flood
The 2009 Red River flood along the Red River of the North in North Dakota and Minnesota in the United States and Manitoba in Canada brought record flood levels to the Fargo-Moorhead area. The flood was a result of saturated and frozen ground, Spring snowmelt exacerbated by additional rain and snow...

.

In the U.S., the New Orleans Metropolitan Area
New Orleans metropolitan area
New Orleans–Metairie–Kenner, or the Greater New Orleans Region is a metropolitan area designated by the United States Census encompassing seven parishes in the state of Louisiana, centering on the city of New Orleans...

, 35% of which sits below sea level, is protected by hundreds of miles of levees and flood gates. This system failed catastrophically, in numerous sections, during Hurricane Katrina
Hurricane Katrina
Hurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall...

, in the city proper and in eastern sections of the Metro Area, resulting in the inundation of approximately 50% of the metropolitan area, ranging from a few centimetres to 8.2 metres (a few inches to 27 feet) in coastal communities. In an act of successful flood prevention, the Federal Government of the United States offered to buy out flood-prone properties in the United States in order to prevent repeated disasters after the 1993 flood across the Midwest. Several communities accepted and the government, in partnership with the state, bought 25,000 properties which they converted into wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....

s. These wetlands act as a sponge in storms and in 1995, when the floods returned, the government did not have to expend resources in those areas.:)

Asia


In India, Bangladesh and China, flood diversion
Diversion
Diversion may refer to:*diversion, a detour, especially of an airplane flight due to severe weather or mechanical failure, or of an ambulance from a fully occupied emergency room to one another nearby hospital*diversion, a distraction...

 areas are rural areas that are deliberately flooded in emergencies in order to protect cities.

Many have proposed that loss of vegetation (deforestation
Deforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....

) will lead to a risk increase. With natural forest cover the flood duration should decrease. Reducing the rate of deforestation should improve the incidents and severity of floods.

Africa


In Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

, both the Aswan Dam
Aswan Dam
The Aswan Dam is an embankment dam situated across the Nile River in Aswan, Egypt. Since the 1950s, the name commonly refers to the High Dam, which is larger and newer than the Aswan Low Dam, which was first completed in 1902...

 (1902) and the Aswan High Dam (1976) have controlled various amounts of flooding along the Nile
Nile
The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

 river.

Clean-up safety


Clean-up activities following floods often pose hazards to workers and volunteers involved in the effort. Potential dangers include: water polluted by mixing with and causing overflows from sanitary sewer
Sanitary sewer
A sanitary sewer is a separate underground carriage system specifically for transporting sewage from houses and commercial buildings to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater...

s, electrical hazards
Electric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....

, carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 exposure, musculoskeletal hazards, heat
Hyperthermia
Hyperthermia is an elevated body temperature due to failed thermoregulation. Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate...

 or cold stress
Hypothermia
Hypothermia is a condition in which core temperature drops below the required temperature for normal metabolism and body functions which is defined as . Body temperature is usually maintained near a constant level of through biologic homeostasis or thermoregulation...

, motor vehicle
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...

-related dangers, fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

, drowning
Drowning
Drowning is death from asphyxia due to suffocation caused by water entering the lungs and preventing the absorption of oxygen leading to cerebral hypoxia....

, 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
Goggles
Goggles or safety glasses are forms of protective eyewear that usually enclose or protect the area surrounding the eye in order to prevent particulates, water or chemicals from striking the eyes. They are used in chemistry laboratories and in woodworking. They are often used in snow sports as well,...

, heavy work gloves, life jackets, and watertight boots with steel toes and insoles.

Benefits


There are many disruptive effects of flooding on human settlements and economic activities. However, floods (in particular the more frequent/smaller floods) can also bring many benefits, such as recharging ground water, making soil more fertile and providing nutrients in which it is deficient. Flood waters provide much needed water resources in particular in arid and semi-arid regions where precipitation events can be very unevenly distributed throughout the year. Freshwater floods in particular play an important role in maintaining ecosystems in river corridors and are a key factor in maintaining floodplain biodiversity. Flooding adds a lot of nutrients to lakes and rivers which leads to improved fisheries for a few years, also because of the suitability of a floodplain for spawning (little predation and a lot of nutrients). Fish like the weather fish make use of floods to reach new habitats. Together with fish also birds profit from the boost in production caused by flooding.

Periodic flooding was essential to the well-being of ancient communities along the Tigris-Euphrates Rivers, the Nile
Nile
The Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...

 River, the Indus River, the Ganges and the Yellow River
Yellow River
The Yellow River or Huang He, formerly known as the Hwang Ho, is the second-longest river in China and the sixth-longest in the world at the estimated length of . Originating in the Bayan Har Mountains in Qinghai Province in western China, it flows through nine provinces of China and empties into...

, among others. The viability for hydrological based renewable sources of energy is higher in flood prone regions.

Computer modelling


While flood modelling is a fairly recent practice, attempts to understand and manage the mechanisms at work in floodplains have been made for at least six millennia. The recent development in computational flood modelling has enabled engineers to step away from the tried and tested "hold or break" approach and its tendency to promote overly engineered structures. Various computational flood models have been developed in recent years either 1D models (flood levels measured in the channel) and 2D models (flood depth measured for the extent of the floodplain). HEC-RAS
HEC-RAS
HEC-RAS is a computer program that models the hydraulics of water flow through natural rivers and other channels. The program is one-dimensional, meaning that there is no direct modeling of the hydraulic effect of cross section shape changes, bends, and other two- and three-dimensional aspects of...

, the Hydraulic Engineering Centre model, is currently among the most popular if only because it is available for free. Other models such as TUFLOW combine 1D and 2D components to derive flood depth in the floodplain. So far the focus has been on mapping tidal and fluvial flood events but the 2007 flood events in the UK have shifted the emphasis onto the impact of surface water flooding.

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 |Date
2,500,000–3,700,000 1931 China floods  China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 
1931
900,000–2,000,000 1887 Yellow River (Huang He) flood  China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 
1887
500,000–700,000 1938 Yellow River (Huang He) flood  China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 
1938
231,000 Banqiao Dam
Banqiao Dam
The Banqiao Reservoir Dam is a dam on the River Ru in Zhumadian Prefecture, Henan province, China. It infamously failed in 1975, causing more casualties than any other dam failure in history, and was subsequently rebuilt....

 failure, result of Typhoon Nina
Typhoon Nina (1975)
Super Typhoon Nina was a short-lived but intense super typhoon that caused catastrophic damage and loss of life in China after causing the Banqiao Dam to collapse...

. Approximately 86,000 people died from flooding and another 145,000 died during subsequent disease.
China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 
1975
230,000 Indian Ocean tsunami
2004 Indian Ocean earthquake
The 2004 Indian Ocean earthquake was an undersea megathrust earthquake that occurred at 00:58:53 UTC on Sunday, December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The quake itself is known by the scientific community as the Sumatra-Andaman earthquake...

 
Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

 
2004
145,000 1935 Yangtze river flood  China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 
1935
100,000+ St. Felix's Flood
St. Felix's Flood
The St. Felix's Flood happened on Saturday 5 November 1530, the name day of St. Felix. This day was later known as Evil Saturday . Large parts of Flanders and Zeeland were washed away, including the Verdronken Land van Reimerswaal. According to Audrey M...

, storm surge
Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

 
1530
100,000 Hanoi
Hanoi
Hanoi , is the capital of Vietnam and the country's second largest city. Its population in 2009 was estimated at 2.6 million for urban districts, 6.5 million for the metropolitan jurisdiction. From 1010 until 1802, it was the most important political centre of Vietnam...

 and Red River Delta
Red River Delta
The Red River Delta is the flat plain formed by the Red River and its distributaries joining in the Thai Binh River in northern Vietnam. The delta measuring some 15,000 square km is well protected by a network of dikes. It is an agriculturally rich area and densely populated...

 flood
North Vietnam
North Vietnam
The Democratic Republic of Vietnam , was a communist state that ruled the northern half of Vietnam from 1954 until 1976 following the Geneva Conference and laid claim to all of Vietnam from 1945 to 1954 during the First Indochina War, during which they controlled pockets of territory throughout...

 
1971
100,000 1911 Yangtze river flood  China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 
1911

See also



  • Chicago Flood
    Chicago Flood
    The Chicago Flood occurred on April 13, 1992, when the damaged wall of a utility tunnel beneath the Chicago River opened into a breach which flooded basements and underground facilities throughout the Chicago Loop with an estimated of water.-Cause:...

    , man-made flood under downtown Chicago
  • Disaster preparedness
  • Flood control in the Netherlands
    Flood control in the Netherlands
    Flood control in the Netherlands is an important issue for the Netherlands as about two thirds of the country is vulnerable to flooding while at the same time the country is among the most densely populated on earth. Natural sand dunes and man made dikes, dams and floodgates provide defense against...

  • Flood pulse concept
    Flood pulse concept
    In contrast to previous ecological theories which considered floods to be catastrophic events, the river flood pulse concept argues that the annual flood pulse is the most important aspect and the most biologically productive feature of a river's ecosystem. It is a geomorphological concept that...

  • Flood Risk Assessment
    Flood risk assessment
    A flood risk assessment is an assessment of the risk of flooding, particularly in relation to residential, commercial and industrial land use.-England and Wales:...

  • Floods directive
    Floods directive
    DIRECTIVE 2007/60/EC of the European Parliament and of the Council of 23 October 2007 on the assessment and management of flood risks is commonly known as the ‘Floods Directive’....

  • Floods in Australia
    Floods in Australia
    This is a list of notable recorded floods that have occurred in the country of Australia.-Further reading:* Devin, L.B. and D.L. Purcell Flooding in Australia Canberra : Australian Government Publishing Service ISBN 0644026278 : .-External links:* .* ....

  • Floods in the Netherlands
    Floods in the Netherlands
    This is a chronological list of floods that have occurred in the Netherlands, until 1500 most parts of the Netherlands were in Frisia.*838 December 26: A large part of the northwest of the Netherlands was flooded by a storm. Lack of good dikes was an important cause of this flood disaster...

  • Floods in the United States
    Floods in the United States
    Floods in the United States are generally caused by excessive rainfall, excessive snowmelt, and dam failure. Below is a list of flood events that were of significant impact to the country, between 1901 and 2000.-Heppner Flood – June 1903:...

  • List of floods
  • SMS (hydrology software)
  • Storm tides of the North Sea


External links