Flood

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For other uses, see Flood (disambiguation). Flood_sentence_0

A flood is an overflow of water that submerges land that is usually dry. Flood_sentence_1

In the sense of "flowing water", the word may also be applied to the inflow of the tide. Flood_sentence_2

Floods are an area of study of the discipline hydrology and are of significant concern in agriculture, civil engineering and public health. Flood_sentence_3

Human changes to the environment often increase the intensity and frequency of flooding, for example land use changes such as deforestation and removal of wetlands, changes in waterway course such as with levees, and larger environmental issues such as climate change and sea level rise. Flood_sentence_4

Floods are considered second only to wildfires as the most common natural disaster on Earth. Flood_sentence_5

Flooding may occur as an overflow of water from water bodies, such as a river, lake, or ocean, in which the water overtops or breaks levees, resulting in some of that water escaping its usual boundaries, or it may occur due to an accumulation of rainwater on saturated ground in an areal flood. Flood_sentence_6

While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, these changes in size are unlikely to be considered significant unless they flood property or drown domestic animals. Flood_sentence_7

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. Flood_sentence_8

Floods often cause damage to homes and businesses if they are in the natural flood plains of rivers. Flood_sentence_9

While riverine flood damage can be eliminated by moving away from rivers and other bodies of water, people have traditionally lived and worked by rivers because the land is usually flat and fertile and because rivers provide easy travel and access to commerce and industry. Flood_sentence_10

Etymology Flood_section_0

The word "flood" comes from the Old English 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). Flood_sentence_11

Principal types Flood_section_1

Areal Flood_section_2

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. Flood_sentence_12

The excess accumulates in place, sometimes to hazardous depths. Flood_sentence_13

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. Flood_sentence_14

Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, or roofs. Flood_sentence_15

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. Flood_sentence_16

Endorheic basins may experience areal flooding during periods when precipitation exceeds evaporation. Flood_sentence_17

Riverine (Channel) Flood_section_3

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. Flood_sentence_18

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. Flood_sentence_19

Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, or beaver dams. Flood_sentence_20

Slow-rising floods most commonly occur in large rivers with large catchment areas. Flood_sentence_21

The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, or tropical cyclones. Flood_sentence_22

However, large rivers may have rapid flooding events in areas with dry climate, since they may have large basins but small river channels and rainfall can be very intense in smaller areas of those basins. Flood_sentence_23

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. Flood_sentence_24

The cause may be localized convective precipitation (intense thunderstorms) or sudden release from an upstream impoundment created behind a dam, landslide, or glacier. Flood_sentence_25

In one instance, a flash flood killed eight people enjoying the water on a Sunday afternoon at a popular waterfall in a narrow canyon. Flood_sentence_26

Without any observed rainfall, the flow rate increased from about 50 to 1,500 cubic feet per second (1.4 to 42 m/s) in just one minute. Flood_sentence_27

Two larger floods occurred at the same site within a week, but no one was at the waterfall on those days. Flood_sentence_28

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. Flood_sentence_29

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. Flood_sentence_30

In that setting, the first flood water to arrive is depleted as it wets the sandy stream bed. Flood_sentence_31

The leading edge of the flood thus advances more slowly than later and higher flows. Flood_sentence_32

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. Flood_sentence_33

Estuarine and coastal Flood_section_4

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. Flood_sentence_34

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. Flood_sentence_35

A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. Flood_sentence_36

Research from the NHC (National Hurricane Center) explains: "Storm surge is an additional rise of water generated by a storm, over and above the predicted astronomical tides. Flood_sentence_37

Storm surge should not be confused with storm tide, which is defined as the water level rise due to the combination of storm surge and the astronomical tide. Flood_sentence_38

This rise in water level can cause extreme flooding in coastal areas particularly when storm surge coincides with spring tide, resulting in storm tides reaching up to 20 feet or more in some cases." Flood_sentence_39

Urban flooding Flood_section_5

Urban flooding is the inundation of land or property in a built environment, particularly in more densely populated areas, caused by rainfall overwhelming the capacity of drainage systems, such as storm sewers. Flood_sentence_40

Although sometimes triggered by events such as flash flooding or snowmelt, urban flooding is a condition, characterized by its repetitive and systemic impacts on communities, that can happen regardless of whether or not affected communities are located within designated floodplains or near any body of water. Flood_sentence_41

Aside from potential overflow of rivers and lakes, snowmelt, stormwater or water released from damaged water mains may accumulate on property and in public rights-of-way, seep through building walls and floors, or backup into buildings through sewer pipes, toilets and sinks. Flood_sentence_42

In urban areas, flood effects can be exacerbated by existing paved streets and roads, which increase the speed of flowing water. Flood_sentence_43

Impervious surfaces prevent rainfall from infiltrating into the ground, thereby causing a higher surface run-off that may be in excess of local drainage capacity. Flood_sentence_44

The flood flow in urbanized areas constitutes a hazard to both the population and infrastructure. Flood_sentence_45

Some recent catastrophes include the inundations of Nîmes (France) in 1998 and Vaison-la-Romaine (France) in 1992, the flooding of New Orleans (USA) in 2005, and the flooding in Rockhampton, Bundaberg, Brisbane during the 2010–2011 summer in Queensland (Australia). Flood_sentence_46

Flood flows in urban environments have been studied relatively recently despite many centuries of flood events. Flood_sentence_47

Some recent research has considered the criteria for safe evacuation of individuals in flooded areas. Flood_sentence_48

Catastrophic Flood_section_6

Catastrophic riverine flooding is usually associated with major infrastructure failures such as the collapse of a dam, but they may also be caused by drainage channel modification from a landslide, earthquake or volcanic eruption. Flood_sentence_49

Examples include outburst floods and lahars. Flood_sentence_50

Tsunamis can cause catastrophic coastal flooding, most commonly resulting from undersea earthquakes. Flood_sentence_51

Causes Flood_section_7

Upslope factors Flood_section_8

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. Flood_sentence_52

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. Flood_sentence_53

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. Flood_sentence_54

Most precipitation records are based on a measured depth of water received within a fixed time interval. Flood_sentence_55

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. Flood_sentence_56

Individual data points are converted to intensity by dividing each measured depth by the period of time between observations. Flood_sentence_57

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. Flood_sentence_58

Convective precipitation events (thunderstorms) tend to produce shorter duration storm events than orographic precipitation. Flood_sentence_59

Duration, intensity, and frequency of rainfall events are important to flood prediction. Flood_sentence_60

Short duration precipitation is more significant to flooding within small drainage basins. Flood_sentence_61

The most important upslope factor in determining flood magnitude is the land area of the watershed upstream of the area of interest. Flood_sentence_62

Rainfall intensity is the second most important factor for watersheds of less than approximately 30 square miles or 80 square kilometres. Flood_sentence_63

The main channel slope is the second most important factor for larger watersheds. Flood_sentence_64

Channel slope and rainfall intensity become the third most important factors for small and large watersheds, respectively. Flood_sentence_65

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. Flood_sentence_66

The time of concentration defines the critical duration of peak rainfall for the area of interest. Flood_sentence_67

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. Flood_sentence_68

Downslope factors Flood_section_9

Water flowing downhill ultimately encounters downstream conditions slowing movement. Flood_sentence_69

The final limitation in coastal flooding lands is often the ocean or some coastal flooding bars which form natural lakes. Flood_sentence_70

In flooding low lands, elevation changes such as tidal fluctuations are significant determinants of coastal and estuarine flooding. Flood_sentence_71

Less predictable events like tsunamis and storm surges may also cause elevation changes in large bodies of water. Flood_sentence_72

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 Flow channel restrictions like bridges and canyons tend to control water elevation above the restriction. Flood_sentence_73

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. Flood_sentence_74

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. Flood_sentence_75

Coincidence Flood_section_10

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. Flood_sentence_76

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. Flood_sentence_77

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. Flood_sentence_78

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. Flood_sentence_79

These considerations ignore further the risks associated with large debris entrained by the flow motion. Flood_sentence_80

Some researchers have mentioned the storage effect in urban areas with transportation corridors created by cut and fill. Flood_sentence_81

Culverted fills may be converted to impoundments if the culverts become blocked by debris, and flow may be diverted along streets. Flood_sentence_82

Several studies have looked into the flow patterns and redistribution in streets during storm events and the implication on flood modelling. Flood_sentence_83

Effects Flood_section_11

Primary effects Flood_section_12

The primary effects of flooding include loss of life and damage to buildings and other structures, including bridges, sewerage systems, roadways, and canals. Flood_sentence_84

Floods also frequently damage power transmission and sometimes power generation, which then has knock-on effects caused by the loss of power. Flood_sentence_85

This includes loss of drinking water treatment and water supply, which may result in loss of drinking water or severe water contamination. Flood_sentence_86

It may also cause the loss of sewage disposal facilities. Flood_sentence_87

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. Flood_sentence_88

"This happened in 2000, as hundreds of people in Mozambique fled to refugee camps after the Limpopo River flooded their homes. Flood_sentence_89

They soon fell ill and died from cholera, which is spread by unsanitary conditions, and malaria, spread by mosquitoes that thrived on the swollen river banks." Flood_sentence_90

Damage to roads and transport infrastructure may make it difficult to mobilize aid to those affected or to provide emergency health treatment. Flood_sentence_91

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. Flood_sentence_92

Entire harvests for a country can be lost in extreme flood circumstances. Flood_sentence_93

Some tree species may not survive prolonged flooding of their root systems. Flood_sentence_94

Secondary and long-term effects Flood_section_13

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. Flood_sentence_95

The impact on those affected may cause psychological damage to those affected, in particular where deaths, serious injuries and loss of property occur. Flood_sentence_96

Urban flooding can cause chronically wet houses, leading to the growth of indoor mold and resulting in adverse health effects, particularly respiratory symptoms. Flood_sentence_97

Urban flooding also has significant economic implications for affected neighborhoods. Flood_sentence_98

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. Flood_sentence_99

According to the U.S. Federal Emergency Management Agency (FEMA), almost 40 percent of small businesses never reopen their doors following a flooding disaster. Flood_sentence_100

In the United States, insurance is available against flood damage to both homes and businesses. Flood_sentence_101

Floods can also be a huge destructive power. Flood_sentence_102

When water flows, it has the ability to demolish all kinds of buildings and objects, such as bridges, structures, houses, trees, cars... For example, in Bangladesh in 2007, a flood was responsible for the destruction of more than one million houses. Flood_sentence_103

And yearly in the United States, floods cause over $7 billion in damage. Flood_sentence_104

Benefits Flood_section_14

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. Flood_sentence_105

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. Flood_sentence_106

Freshwater floods particularly play an important role in maintaining ecosystems in river corridors and are a key factor in maintaining floodplain biodiversity. Flood_sentence_107

Flooding can spread nutrients to lakes and rivers, which can lead to increased biomass and improved fisheries for a few years. Flood_sentence_108

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. Flood_sentence_109

Fish, such as the weather fish, make use of floods in order to reach new habitats. Flood_sentence_110

Bird populations may also profit from the boost in food production caused by flooding. Flood_sentence_111

Periodic flooding was essential to the well-being of ancient communities along the Tigris-Euphrates Rivers, the Nile River, the Indus River, the Ganges and the Yellow River among others. Flood_sentence_112

The viability of hydropower, a renewable source of energy, is also higher in flood prone regions. Flood_sentence_113

Flood safety planning Flood_section_15

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. Flood_sentence_114

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. Flood_sentence_115

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. Flood_sentence_116

Structures, such as bridges, that must unavoidably be in flood hazard areas should be designed to withstand flooding. Flood_sentence_117

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. Flood_sentence_118

Planning for flood safety involves many aspects of analysis and engineering, including: Flood_sentence_119

Flood_unordered_list_0

  • observation of previous and present flood heights and inundated areas,Flood_item_0_0
  • statistical, hydrologic, and hydraulic model analyses,Flood_item_0_1
  • mapping inundated areas and flood heights for future flood scenarios,Flood_item_0_2
  • long-term land use planning and regulation,Flood_item_0_3
  • engineering design and construction of structures to control or withstand flooding,Flood_item_0_4
  • intermediate-term monitoring, forecasting, and emergency-response planning, andFlood_item_0_5
  • short-term monitoring, warning, and response operations.Flood_item_0_6

Each topic presents distinct yet related questions with varying scope and scale in time, space, and the people involved. Flood_sentence_120

Attempts to understand and manage the mechanisms at work in floodplains have been made for at least six millennia. Flood_sentence_121

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. Flood_sentence_122

A portfolio of best practice examples for disaster mitigation in the United States is available from the Federal Emergency Management Agency. Flood_sentence_123

Control Flood_section_16

Main article: Flood control Flood_sentence_124

In many countries around the world, waterways prone to floods are often carefully managed. Flood_sentence_125

Defenses such as detention basins, levees, bunds, reservoirs, and weirs are used to prevent waterways from overflowing their banks. Flood_sentence_126

When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are often used to try to stem flooding. Flood_sentence_127

Coastal flooding has been addressed in portions of Europe and the Americas with coastal defenses, such as sea walls, beach nourishment, and barrier islands. Flood_sentence_128

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_sentence_129

Flood controls, such as dams, can be built and maintained over time to try to reduce the occurrence and severity of floods as well. Flood_sentence_130

In the United States, the U.S. Flood_sentence_131 Army Corps of Engineers maintains a network of such flood control dams. Flood_sentence_132

In areas prone to urban flooding, one solution is the repair and expansion of man-made sewer systems and stormwater infrastructure. Flood_sentence_133

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)). Flood_sentence_134

Areas identified as flood-prone can be converted into parks and playgrounds that can tolerate occasional flooding. Flood_sentence_135

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. Flood_sentence_136

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_sentence_137

In some areas, the presence of certain species (such as beavers) can be beneficial for flood control reasons. Flood_sentence_138

Beavers build and maintain beaver dams which will reduce the height of flood waves moving down the river (during periods of heavy rains), and will reduce or eliminate damage to human structures, at the cost of minor flooding near the dams (often on farmland). Flood_sentence_139

Besides this, they also boost wildlife populations and filter pollutants (manure, fertilisers, slurry).. UK's minister Rebecca Plow stated that in the future the beavers could be considered a "public good" and landowners would be payed to have them on their land. Flood_sentence_140

Analysis of flood information Flood_section_17

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. Flood_sentence_141

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. Flood_sentence_142

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. Flood_sentence_143

Conversely, given the observed inundation area of a recent flood and the channel conditions, a model can calculate the flow rate. Flood_sentence_144

Applied to various potential channel configurations and flow rates, a reach model can contribute to selecting an optimum design for a modified channel. Flood_sentence_145

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). Flood_sentence_146

HEC-RAS, the Hydraulic Engineering Center model, is among the most popular software, if only because it is available free of charge. Flood_sentence_147

Other models such as TUFLOW combine 1D and 2D components to derive flood depths across both river channels and the entire floodplain. Flood_sentence_148

Physical process models of complete drainage basins are even more complex. Flood_sentence_149

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. Flood_sentence_150

Basin models typically combine land-surface process components (to estimate how much rainfall or snowmelt reaches a channel) with a series of reach models. Flood_sentence_151

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. Flood_sentence_152

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. Flood_sentence_153

Flood forecasting Flood_section_18

Main articles: Flood forecasting and flood warning Flood_sentence_154

Anticipating floods before they occur allows for precautions to be taken and people to be warned so that they can be prepared in advance for flooding conditions. Flood_sentence_155

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. Flood_sentence_156

Emergency services can also make provisions to have enough resources available ahead of time to respond to emergencies as they occur. Flood_sentence_157

People can evacuate areas to be flooded. Flood_sentence_158

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. Flood_sentence_159

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. Flood_sentence_160

Radar estimates of rainfall and general weather forecasting techniques are also important components of good flood forecasting. Flood_sentence_161

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. Flood_sentence_162

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, and it also may allow for the computation of the likely statistical return period of a flood. Flood_sentence_163

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% of occurring in any 100-year period of time. Flood_sentence_164

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. Flood_sentence_165

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. Flood_sentence_166

In the United States, an integrated approach to real-time hydrologic computer modelling utilizes observed data from the U.S. Flood_sentence_167 Geological Survey (USGS), various cooperative observing networks, various automated weather sensors, the NOAA National Operational Hydrologic Remote Sensing Center (NOHRSC), 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. Flood_sentence_168

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. Flood_sentence_169

The Global Flood Monitoring System, "GFMS," a computer tool which maps flood conditions worldwide, is available . Flood_sentence_170

Users anywhere in the world can use GFMS to determine when floods may occur in their area. Flood_sentence_171

GFMS uses precipitation data from NASA's Earth observing satellites and the Global Precipitation Measurement satellite, "GPM." Flood_sentence_172

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. Flood_sentence_173

Users can view statistics for rainfall, streamflow, water depth, and flooding every 3 hours, at each 12 kilometer gridpoint on a global map. Flood_sentence_174

Forecasts for these parameters are 5 days into the future. Flood_sentence_175

Users can zoom in to see inundation maps (areas estimated to be covered with water) in 1 kilometer resolution. Flood_sentence_176

Deadliest floods Flood_section_19

Main article: List of deadliest floods Flood_sentence_177

Below is a list of the deadliest floods worldwide, showing events with death tolls at or above 100,000 individuals. Flood_sentence_178

Flood_table_general_0

Death tollFlood_header_cell_0_0_0 EventFlood_header_cell_0_0_1 LocationFlood_header_cell_0_0_2 YearFlood_header_cell_0_0_3
2,500,000–3,700,000Flood_cell_0_1_0 1931 China floodsFlood_cell_0_1_1 ChinaFlood_cell_0_1_2 1931Flood_cell_0_1_3
900,000–2,000,000Flood_cell_0_2_0 1887 Yellow River floodFlood_cell_0_2_1 ChinaFlood_cell_0_2_2 1887Flood_cell_0_2_3
500,000–700,000Flood_cell_0_3_0 1938 Yellow River floodFlood_cell_0_3_1 ChinaFlood_cell_0_3_2 1938Flood_cell_0_3_3
231,000Flood_cell_0_4_0 Banqiao Dam failure, result of Typhoon Nina. Approximately 86,000 people died from flooding and another 145,000 died during subsequent disease.Flood_cell_0_4_1 ChinaFlood_cell_0_4_2 1975Flood_cell_0_4_3
230,000Flood_cell_0_5_0 2004 Indian Ocean tsunamiFlood_cell_0_5_1 IndonesiaFlood_cell_0_5_2 2004Flood_cell_0_5_3
145,000Flood_cell_0_6_0 1935 Yangtze river floodFlood_cell_0_6_1 ChinaFlood_cell_0_6_2 1935Flood_cell_0_6_3
100,000+Flood_cell_0_7_0 St. Felix's flood, storm surgeFlood_cell_0_7_1 NetherlandsFlood_cell_0_7_2 1530Flood_cell_0_7_3
100,000Flood_cell_0_8_0 Hanoi and Red River Delta floodFlood_cell_0_8_1 North VietnamFlood_cell_0_8_2 1971Flood_cell_0_8_3
100,000Flood_cell_0_9_0 1911 Yangtze river floodFlood_cell_0_9_1 ChinaFlood_cell_0_9_2 1911Flood_cell_0_9_3

In myth and religion Flood_section_20

Flood myths (great, civilization-destroying floods) are widespread in many cultures. Flood_sentence_179

Flood events in the form of divine retribution have also been described in religious texts. Flood_sentence_180

As a prime example, the Genesis flood narrative plays a prominent role in Judaism, Christianity and Islam. Flood_sentence_181

See also Flood_section_21

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Flood.