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flood (in hydrology)

flood, inundation of land by the rise and overflow of a body of water. Floods occur most commonly when water from heavy rainfall, from melting ice and snow, or from a combination of these exceeds the carrying capacity of the river system, lake, or the like into which it runs. Usually the combined flow of several water-swollen tributaries causes flooding along a river bank or shoreline. Accounts of floods that destroyed nearly all life are found in the mythology of many peoples (see Deluge). Not all floods are destructive, however. The annual floodwaters of the Nile and some other larger rivers historically deposited fertile soil along the surrounding floodplain, which is used extensively for agriculture. The damming of the Nile and other rivers in modern times, however, often has greatly reduced this deposition.

Flood Characteristics and Control

The rise and fall of the water level in a river is called the flood wave. Its highest point, or crest, travels progressively downstream. In the upstream portions of a river the flood crest passes quickly. Further downstream the greater volume of water causes slower passage of the flood crest, resulting in floods of longer duration. In many regions, annual floods follow the thaws and rains of spring; flooding also may occur because of thawing ice jamming narrower and shallower parts of a river. In the Arctic regions, especially in the basins of northward flowing rivers, the floods are caused by the thawing of the southern portion of the basin before the ice blocking the lower course of the river melts. Less predictable are floods resulting from ocean waves, called storm surges, pushed onshore by an advancing hurricane, and from sudden torrential flows, called flash floods, following a brief, intense rainstorm or the bursting of a natural or constructed dam or levee. In addition to the duration and quantity of rainfall, the nature of the soil (permeability; state of saturation) of an area affects the frequency of floods.

Generally, flood control measures along a river are attempted at both its headwaters and its low-lying floodplains. Runoff can be detained in the headwaters by planting ground cover on the slopes, building terraces to increase soil infiltration and prevent soil erosion, and building small check dams or retaining ponds to reduce the flow of water. Flood control on the lower floodplains involves building levees to contain the flow and straightening or dredging the channel to improve flow characteristics. Concern over the affects of channelization on rivers in floodplains has led to the development of flood-control approaches that attempt to combine the way floodplains naturally handle floodwaters with traditional methods that restrict those waters greater spread. Such an approach might involve increasing the distance of levees from a river's channel along with the creation of wetlands to absorb floodwaters. Among the chief flood-control projects in the United States are the flood control works along the Mississippi River, the installations of the Tennessee Valley Authority, the Glen Canyon and Hoover dams on the Colorado River, and the systems of dams in the Columbia River basin (including Grand Coulee Dam) and in the Missouri River basin.

Notable Floods

A flood of the Tiber was recorded in 413 BC Records of floods on the Danube date from AD 1000. In China some of the world's most disastrous floods have been caused by the unstable Huang He (Yellow River). The river, which flows at or above the level of the bordering land, is contained in part by levees; however, because its channel has gradually become filled with deposited sediment, any appreciable increase in its volume causes the river to overflow and flood the surrounding area. The Netherlands, dependent on its dikes for protection from inundation, has suffered many disastrous floods from the sea and the Rhine and Meuse rivers. In 1970, 1985, and 1991, hundreds of thousands of people in Bangladesh were killed when the combination of high tides and a tropical cyclone (see hurricane) storm surge caused widespread flooding of the low-lying delta of the Ganges and Brahmaputra rivers.

In the United States the Johnstown, Pa., flood of 1889, in which thousands of lives were lost, was caused by the breaking of an earth dam above the city. Even greater loss of life occurred (1900) in Galveston, Tex., when tide and storm surges engulfed the city after a hurricane. The hurricanes of 1938 on the New England and Long Island coasts and Hurricane Donna in 1960 along the Atlantic coast from Florida to the Long Island Sound were also followed by storm surges. In June, 1972, extremely heavy rainfall associated with a tropical storm inundated the basins of the Chemung and Susquehanna rivers of New York and Pennsylvania, causing severely damaging floods in Corning and Elmira, N.Y., and Wilkes-Barre and Harrisburg, Pa. In July, 1979, Hurricane Claudette deposited a U.S. record of 43 in. (109 cm) of rain in Alvin, Tex., in 24 hours. Hurricane Katrina in Aug., 2005, led to extensive and devastating storm-surge flooding along the Louisiana and Mississippi coasts, and the failure of several levees in the New Orleans area resulted in hundreds of deaths. The worst floods in the United States from river overflow were in 1913 on the Miami River (a tributary of the Ohio), in 1927, 1937, 1973, and 2011 on the Mississippi River and some of its tributaries, in 1935–36 on several New England rivers, and in 1993 on the Missouri, Mississippi, and some of their tributaries.

Bibliography

See P. Briggs, Rampage (1973); C. Clark, Flood (1982).

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flood

flood / fləd/ • n. 1. an overflowing of a large amount of water beyond its normal confines, esp. over what is normally dry land: in a thousand miles the flood destroyed every bridge | people uprooted by drought or flood | [as adj.] a flood barrier. ∎  (the Flood) the biblical flood brought by God upon the earth because of the wickedness of the human race (Gen. 6 ff.). ∎  the inflow of the tide. ∎ poetic/lit. a river, stream, or sea. 2. an outpouring of tears or emotion: Rose burst into such a flood of tears and sobs as I had never seen. ∎  a very large quantity of people or things that appear or need to be dealt with: a constant flood of callers. 3. short for floodlight. • v. 1. [tr.] cover or submerge (a place or area) with water: the dam burst, flooding a small town watching her father flood their backyard skating rink | [as n.] (flooding) a serious risk of flooding. ∎  [intr.] become covered or submerged in this way: part of the vessel flooded | fig. Sarah's eyes flooded with tears. ∎  (usu. be flooded out) drive someone out of their home or business with a flood: most of the families who have been flooded out will receive compensation. ∎  (of a river or sea) become swollen and overflow (its banks): the river flooded its banks | [intr.] the river will flood if it gets much worse. ∎  overfill the carburetor of (an engine) with fuel, causing the engine to fail to start. 2. [intr.] arrive in overwhelming amounts or quantities: congratulatory messages flooded in his old fears came flooding back. ∎  [tr.] overwhelm or swamp with large amounts or quantities: our switchboard was flooded with calls. ∎  [tr.] fill or suffuse completely: she flooded the room with light. PHRASES: be in (full) flood (of a river) be swollen and overflowing its banks. ∎  (be in full flood) fig. (of a person or action) have gained momentum; be at the height of activity: discussion was already in full flood and refused to be dammed.

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Floods

Floods

Floods are among the most powerful and devastating of natural events. Long after the water has subsided, people remember and talk about the loss and destruction. Moreover, the scale of devastation is often so great as to convince people that the flooding is the work of supernatural beings.

Small wonder, then, that flood myths occur in cultures around the world. One of the most common tells of a great flood that occurred in the distant past. The biblical story of Noah and the ark he built to save certain people and animals from the flood is just one version of a much older myth from Mesopotamia* . Similar stories appear wherever people have experienced floods.

Some scholars believe that memories of real disasters, such as the violent and unpredictable floods that occurred along Mesopotamia's Tigris and Euphrates Rivers, underlie mythological accounts of catastrophic rains and inundations. These stories give meaning and purpose to events in the natural world. In myths, floods become part of a cycle of destruction and rebirth.


Flood Themes

Mythological floods are not local. They take place on a cosmic scale, generally covering the whole world. Though the direct cause of the rising waters may be heavy rainfall, gods or other supernatural beings are responsible. Often the flood is sent as punishment for the wrongdoings of humankind.

supernatural related to forces beyond the norma! world; magical or miraculous

inundation floodwaters that cover the land

cosmic large or universal in scale; having to do with the universe

ritual ceremony that follows a set pattern

In some traditions, a flood reproduces the original mythological conditions of creationthe formless, empty expanse out of which the world was created. The inundation not only destroys the old world but also sets the stage for a brand new one. In myths in which the flood was sent to punish people for their sins, the new world that follows the flood is purified. The religious ritual of baptism reenacts the flood myth on an individual level. The baptismal water is believed to wash away sins, allowing people to be reborn in a purified state. In India, Hindus bathe in the sacred Ganges River to purify themselves. According to many myths of the great flood, a few virtuous individuals survived the inundation, perhaps with the help or advice of a friendly deity. Those survivors repopulated the world, becoming the parents of the present human race. In this way, flood myths are often myths of human origins as well.


Flood Myths

Although the details of the stories differ, flood myths from around the world have many similarities. The themes of punishment, survival, and rebirth or renewal occur frequently.

deity god or goddess

Ancient Near East. The basic flood myth of the ancient Near East, in which the flood was sent as a divine punishment, originated among the Sumerian cities in southern Mesopotamia. Over a period of several thousand years, the Babylonians, the Hebrews, and other civilizations developed their own versions.

* See Names and Places at the end of this volume for further information.

The Sumerian myth tells how the human race, which the gods had created to do their work, became so numerous and noisy that the god Enlil sent a flood to destroy it. However, another god, Enki, wanted to save King Ziusudra (King Atrahasis in some versions). Forbidden by Enlil to warn the king, Enki spoke to the king's reed house. The king overheard the warning, built a boat, and saved his family and a collection of animals.

The Babylonian version of the flood myth appears in the Epic of Gilgamesh. In this account, the survivor is a man called Utnapishtim. Warned of the flood by a dream in which he heard a god whispering to his reed house, Utnapishtim built a boat, took aboard his family and a selection of craftspeople and animals, and rode out a terrible storm that raged for six days and six nights. Finally the boat landed on a mountaintop, the only land above the flood. Utnapishtim and his wife become immortal as a reward for following the advice of the god in the dream.

The Hebrew version of the story, told in the book of Genesis in the Bible, places greater emphasis on the sinfulness of humankind. The flood was not a cruel whim or mistake of the gods but a deliberate punishment. Like Utnapishtim, Noah was a good man who received a warning and instructions to build a boat. He and his family, and two of every sort of living thing, survived the flood and landed upon the peak of Mount Ararat.


Egypt. The Egyptian flood myth begins with the sun god Ra, who feared that people were going to overthrow him. He sent the goddess Hathor, who was his eye, to punish the people. But she killed so many that their blood, flowing into the Nile River and the ocean, caused a flood. Hathor greedily drank the bloody water. Feeling that things had gone too far, Ra ordered slaves to make a lake of beer, dyed red to look like blood. Hathor drank the beer, became very drunk, and failed to finish the task of wiping out humanity. The survivors of her bloodbath started the human race anew.


Ancient Greece. The Greek flood myth says that Zeus, father of the gods, sent a mighty inundation to destroy the human race. Some versions say that Zeus was angry at the Titan Prometheus* for stealing the gift of fire from the gods and giving it to people. Others say that the flood was punishment for human sinfulness. Prometheus warned his son Deucalion to escape the flood by building a boat. Deucalion and his wife survived, and when the flood waters retreated, they were the only humans left on earth. The couple began the race of people who inhabit the world today. The story of the flood, along with many other Greek myths, appears in the Metamorphoses * by the Roman poet Ovid.

immortal able to live forever

Titan one of a family of giants who ruled the earth until overthrown by the Greek gods of Olympus

China. For thousands of years, the Chinese people have suffered from the flooding of the two great rivers that flow through their land, the Chang Jiang (Yangtze) and the Huang He (Yellow) Rivers. Taming the rivers was one of the chief goals of early Chinese civilization. The story of Yu, one of several Chinese flood myths, celebrates a victory in the long struggle against floods.

In the myth, a man named Gun tried for nine years to dam the destructive waters that covered the land. Because he failed, the supreme god executed him. Gun's son, Yu, took up the task of taming the waters. Instead of building a dam, he decided to drain away the floodwaters through channels. A winged dragon flew in front of him, marking with his tail where Yu should dig the channels. Yu worked for many years, too busy even to see his family. In the end, however, he tamed the rivers, making the land along them suitable for farming. As his reward, Yu became emperor of China.


India. The flood legend of India begins with a creator god named Manu washing himself with water from a jar. A fish in the jar asked for Manu's protection and promised to save him from a great flood that would occur in the future. Manu raised the fish until it was one of the largest fish in the world, and then he released it into the sea. The fish told Manu what year the flood would come and advised him to build a ship. Manu built the ship, and when the flood came, the fish towed it to a mountaintop. Manu alone survived the flood. The fish is generally identified as one form of the god Vishnu* .


Native America. In many Native American myths, floods occur as punishment for human misdeeds. The Chiricahua Apache maintain that the Great Spirit sent a flood to drown the whole earth because people did not worship him. According to the Navajo, a series of floods forced the people to emerge from deep in the earth through several higher worlds. The final flood was caused by Water Monster, who became angry when Coyote stole his child. This flood, which drove the people to the surface of the present world, ended when Coyote returned the Water Monster's baby. The Cheyenne say that the gods use floodwaters to control people's movements.

Floods also have positive powers. In myths of the Arikara and Caddo people, floods wipe out evil giants and make the world safe for humans. Several Indian mythologies in Mexico and the American West tell of cycles of destruction in which one whole world creation was destroyed by flood, while others ended in fire, ice, wind, or other disasters. The Aztecs believed that the first age of creation ended in a flood. In the Mayan creation story, a flood washes away the wooden people made by the gods in an early attempt to create human beings.


Australia. Several groups among the Aborigines, the native people of Australia, believe that a vast flood swept away a previous society. Perhaps these myths grew out of conditions at the end of the last Ice Age, when sea levels rose and coastal regions flooded.

The Thunder God and the Gourd

The Yao people of southern China have a myth that tells how the thunder god caused a great flood. A man captured the god to stop the rains, but the god convinced the man's son and daughter to set him free, and the flooding resumed. The man built a boat and floated to heaven to ask the other gods to help. They were too helpful. The water god drained the flood away so rapidly that the boat crashed to earth, killing the man. His children, meanwhile, were the only survivors of the flood. They floated on the water in a large gourd that grew from a tooth the thunder god had given them. They became the parents of a new human race.

One group of Aborigines says that their ancestral heroes, the Wandjina, caused the flood and then re-created society in its present form. Another version of the myth tells that a huge half-human


* See Names and Places at the end of this volume for further information.

snake called Yurlunggur brought on the flood to punish two sisters for sexual misbehavior, that is, for breaking tribal rules concerning proper partners. Yurlunggur swallowed the sisters, but after the floodwaters withdrew, he spat them out and allowed them to start a new society.

See also Creation Stories; Gilgamesh; Manu; Noah; Utnapishtim; Wandjina; Yu.

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Flood

Flood

a large body of water; a great flow or stream of any fluid; any great overwhelming quantity.

Examples: flood of banknotes; of eloquence, 1599; of fire, 1711; of joy, 1719; of laughter, 1611; of lava; of golden light, 1680; of mutiny, 1710; of silver, 1894; of tears, 1589; of unbelief and carelessness, 1833; of visitors, 1607; of water; of fiery words, 1877.

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flood

flood sb. OE. flōd, corr. to OS. flōd (Du. vloed). OHG. fluot (G. flut). ON. flóð, Goth. flōdus :- Gmc. *flōðuz, -am, f. *flō- :- IE. *plō- (as in Gr. plṓin swim).

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Flood

Flood. Deluge described in Genesis 6. 1–9. 18. For the flood of Manu in India, see PRALAYA.

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Flood (in the Bible)

Flood, in the Bible: see Deluge.

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flood

floodblood, bud, crud, cud, dud, flood, Judd, mud, rudd, scud, spud, stud, sudd, thud •redbud • lifeblood •stick-in-the-mud

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FLOOD

FLOOD (flʌd) (USA) fleet observation of oceanographic data

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Flood

FLOOD

A cataclysmic event narrated in Gen 6:59:19. The account is the theological center of the genesis account of prehistory in chaps. 1 11 (see primeval age in the bible). God was heartbroken because human wickedness and violence had corrupted his good creation, and He determined to destroy all created things; but after finding noah to be righteous, God decided to preserve Noah and his family. God then had Noah preserve specimens of all living creatures so as to be able to populate a renewed creation in a new world order. The Genesis account is a composite of ancient Israelite traditions and reflects the influence of flood stories from other Near Eastern peoples (see gilgamesh epic). Several New Testament authors refer to the Genesis story in exhortations to watchfulness and to faith.

Terminology. Various Old Testament writers vividly describe both the well-known frequent flash floods and ordinary seasonal flooding using common Hebrew words, but for the Genesis flood the authors reserved the word mabbûl, using the term 12 times. Outside Genesis, the word occurs only in Ps 29:10. There YHWH is described as enthroned above the mabbûl, a reference to the waters above the dome described in Gen 1:7 (see also Gen 7:11). The Deuterocanonical book of Sirach (44:17) and the Dead Sea Scrolls' Genesis Apocryphon (12:10) refer to the Genesis flood using mabbûl. The Septuagint translators used the Greek word κατακλυσμός where the Hebrew had mabbûl, and also in Sir 40:10; 44:1718, and 4 Macc 15:31 in references to the Genesis flood. But in other places, the translators used κατακλυσμός for ordinary generic floods (Ps 32 [31]:6; Nah 1:8; Sir 21:13; 4 Macc 15:32). In the New Testament κατακλυσμός always refers to the Genesis flood (Matt 24:3839; Luke 17:27; 2 Pet 2:5).

Literary Character of Gen 6:59:19. For more than two centuries scholars have recognized the presence of distinguishable sources in the Pentateuch. In the Genesis flood account at least two distinct sources were woven together, often referred to as the yahwist source (Y) and the priestly source (P). The older J segments use YHWH ("Lord" or "Yahweh") as God's name and depict God in more anthropomorphic terms. For example, in 6:6, the Lord's heart grieved; in 7:16b, the Lord shut Noah and those with him in the ark, and in 8:21, the Lord smelled the pleasing aroma of Noah's sacrifice. The P source uses the common Hebrew word elōhîm ("God") for the deity and favors genealogies, precise numbers and dates. Examples in the Flood narrative include the repeated emphasis on Noah and his sons as the ancestors of all humanity, the precise dimensions of the ark in 6:15, and the exact dates on which the flood began and ended in 7:11 and 8:13. P also favors the themes of blessing and covenant reflected in 9:3, 7 and 6:18; 9:817. The presence of these sources in the flood narrative becomes evident in multiple doublets and inconsistencies. In 6:22 Noah does all that "God" (P) commanded, and in 7:5 Noah does all that the "Lord" (J) commanded. In the P source, God commands Noah to preserve one male-female pair of every living creature (6:1920; 7:1516). In J, the Lord calls for seven pairs of clean animals and birds, but single pairs of those that are unclean (7:23). In J the destruction is a consequence of rainfall (7:4,12), while in P it comes when the fountains of the great deep burst and the windows of the heavens are opened (7:11). In P the flood continues for more than a year (7:11,24; 8:3,5,1314), while in J it is 40 days and 40 nights (7:4,6,10,12). When J elements are extracted from the account, the P components form a complete and consistent narrative. While the earlier J tradition was substantially preserved in the blending of the traditions, gaps between some components suggest that parts may have been omitted, for example, the instructions to build the ark.

The doublets and differences in the sources were skillfully woven into a unified narrative with an extended palistrophe, a narrative device that divides a story in two, so that many events and details in the first half of the account mirror or parallel details and events in the second half. The Lord's decision to destroy creation in 6:58 (J), announced by God to Noah in 6:11 (P) finds a parallel in the Lord's decision to never again destroy creation in 8:2122 (J), announced to Noah in 9:817 (P). The names of Noah's three sons at 6:10 are repeated at 9:1819. God's promised covenant with Noah and his family in 6:18 is fulfilled at 9:917. The Lord's command for Noah and the animals to enter the ark in 7:1, followed by the account of Noah and the animals entering the ark in 7:78 is paralleled by God's command that Noah and the animals leave the ark in 8:1617, followed by an account of their exiting the ark in 8:1819. The waters swell and lift the ark, covering the mountains in 7:1820. The waters recede, the mountains appear, and the ark comes to rest in 8:35. Only Noah and those with him in the ark were left in 7:23, and God remembered Noah and all the wild animals and all the domestic animals that were with him in the ark in 8:1. The elaborate structure contributes to the narrative flow, with everything centered on God's remembrance of Noah in 8:1.

Significance. The main character of the composite biblical account is God. Noah, described as perfectly obedient (6:22; 7:5), does not even speak. The reason for the flood is the grief in the Lord's heart because humans' hearts were inclined continually and only toward evil (6:56) and because human sin had spoiled what had been God's "very good" creation (6:1113, see Gen 1:31). After the flood, when the Lord recognizes that the flood has not changed the inclination of human hearts toward evil, He decides to never repeat the destruction (8:21). Prior to the flood, increasingly pervasive human sin brings curses upon the ground (3:17; 4:11) and the ultimate curse, the flood itself. In the renewed created order after the flood, God's new response to human sin is blessing and covenant (9:117). To counter violence, bloodshed, and vengeance, Noah and his offspring, acting with God's authority, are made accountable for preserving all life, animal and human. In God's new order, humanity is charged with limiting vengeance and keeping lawlessness from spoiling the new creation. The story of Noah and his sons that follows the flood account (9:1829) illustrates this new order. God is not even present as a character. Noah, speaking for the first and only time, curses Ham and Ham's descendant Canaan for their sin. Noah blesses Shem and Japheth for their righteous behavior.

The use of the Hebrew word mabbûl in the Genesis flood account and in Ps 29:10, along with the reference to the fountains of the great deep and the windows of the heavens in 7:11 and 8:2, suggests that the P tradition understood the flood as a near return to the formless chaotic void of the P account of creation in Gen 1:2. The "wind" (rûa.) with which God stops the flood in 8:1 is the same "wind" (rûa. ) of God that hovered over the waters of the great deep in 1:2; but the renewed world after the flood populated by the people and animals God saved with Noah in the ark is far different from the ordered and sevenfold good creation of Genesis 1. The original harmony between humans and nature and among humans themselves has been altered. Now animals will fear and dread human dominion (9:2). Because the original abundance of nourishing trees and vegetation is no more, humans are permitted to kill and eat animals for food (9:3), and because the potential for murder remains, God ordains societal punishment of murderers so that desire for revenge will not again degenerate into limitless lawlessness (9:6).

This P tradition of understanding supplements and develops themes present in the earlier J tradition. In J's flood account, "rain water," was the instrument of destruction of all living things (7:4); in J's creation account, it was acknowledged as essential for life (2:59). Sin, initiated by the first man and woman's disobedience (3:17), becomes increasingly pervasive in J's accounts of Cain's murder of his brother (4:116), Lamech's polygamy and ruthless vengeance (4:1924), and the use of status and power to exploit and abuse the weak and defenseless (6:14). Each story illustrates a growing alienation between the Lord and humanity, between human and human, and between humanity and nature. In the J account, what would seem to be advances in civilization are progressive movements away from the Lord and the Lord's intended order (4:2022) until the Lord regrets having made anything (5:7). For J, the Lord's new direction after the flood comes when the Lord smells the pleasing odor from Noah's sacrifice (8:2022). Sacrificial worship is the remedy for human hearts' continued inclination toward evil. Noah's sacrifice of some of every clean animal and bird explains why in J it was necessary for Noah to bring more than one pair of each clean creature onto the ark. In the J tradition, covenant and blessing come into the picture in the Lord's call to Abram in Gen 12:13, while for P, sacrificial worship does not come until God gives Moses instructions for the conduct of the sacrificial cult beginning at Exodus chapter 35.

In the New Testament, in Matt 24:3739 and Luke 17:2627, Jesus likened the coming of the kingdom of God to the coming of the flood that caught Noah's contemporaries unaware. Jesus' followers are called to constant vigilance so as to be prepared when the Son of Man appears. The author of 2 Peter includes the flood among examples of instances where God punished human sinfulness (2:4). Then in 3:37, the author offers the destruction by the flood as proof that the judgement is coming and will actually occur. The author of 1 Pet 3:2021 refers to the ark, whose inhabitants were saved through water, as prefiguring baptism that saves from sin. The author of the Epistle to the Hebrews presents Noah as an example of faith who, warned by God about the unfor-seen coming destruction, obeyed the warning, and became heir to the righteousness that comes in accord with faith (Heb 11:7).

Other Flood Traditions. While flood traditions were widespread among many ancient civilizations, three from Mesopotamia are of special interest in relation to the Genesis account: Atrahasis, Gilgamesh Tablet XI, and Ziusundra (J. B. Pritchard, ed. Ancient Near Eastern Texts, pp. 4244, 9397, 1046). The accounts of the dimensions for the ark in Genesis and for the ship in the Akkadian Gilgamesh story illustrate the nature of the many parallels in the narratives. In Genesis, P describes the ark as 450 feet long, 75 feet wide, and 45 feet high (a biblical cubit = 1.5 feet). It had three decks, a pitched roof, and a door in its side (6:1516). In Gilgamesh, the ship is a cube, 180 feet to each side. There are six decks, seven levels, and a sectioned floor plan (Ancient Near Eastern Texts p. 93).

The many such parallels in these accounts with the Genesis flood story do not suggest direct literary dependence. The manifold differences between details in these accounts and those of Genesis, especially in their depiction of the deities and their motives and their interpretation of events, make these accounts significant to understanding and interpreting the Genesis account. An example is the Genesis account of the Lord's smelling of the pleasing odor of Noah's sacrifice (8:21). In Gilgamesh, "The gods smelled the savor, The gods smelled the sweet savor, The gods crowded like flies about the sacrificer" (Ancient Near Eastern Texts p. 95).

Historical and Scientific Issues. The composite character of the Biblical account and the variations in details within the Mesopotamian accounts suggest that no one of these is an account of a particular historical flood. Floods were common in ancient Mesopotamia, and occasionally devastated whole cities; but no scientific, geological, or historical evidence even suggests that at one time a single flood totally wiped out all of civilization in ancient Mesopotamia, let alone the whole world. That marine fossils are commonly found in mountainous areas throughout the world is the result of geological uplifts. Periodically, news accounts appear about wood that is claimed to be from the ark, recovered on modern Mt. Ararat in Turkey. Carbon 14 tests consistently show that the wood is from the current era, about 1600 years old. The wood is thought to come from the ruins of an ancient monastery that served as a pilgrims' hostel.

The various flood accounts from Mesopotamia suggest that experiences with devastating local floods helped human imaginations to construct accounts of an even worse flood in the distant past that did almost destroy humanity. The accounts reflect the helplessness that humans experience in the face of raging flood waters capable of devastating entire cities. The accounts similarly reflect belief that such natural phenomena were expressions of divine power and will, brought on out of spite or irritation or capriciousness. Because some humans survived each local flood, in each account some humans survive, sometimes due to chance, and other times to the intervention of a sympathetic divine power.

The ancient authors of the Genesis flood story wove their Israelite traditions around one such devastating flood to create a compelling story about their God and His relationship with humanity. The scientific or historical accuracy of the biblical narrative, measured by modern human standards, is irrelevant to the accounts' abiding theological significance.

Bibliography: w. brueggemann, Genesis (Atlanta, 1982). a.f. campbell and m.a. o'brien, Sources of the Pentateuch: Texts, Introductions, Annotations (Minneapolis, 1993). n. cohn, Noah's Flood: The Genesis Story in Western Thought (New Haven, 1996). a. dundes, ed., The Flood Myth. (Berkeley, 1988). w.g. lambert and a.r. millard, Atra-Hasīs: The Babylonian Story of the Flood (Winona Lake, IN, 1999). j. b. pritchard, Ancient Near Eastern Texts Relating to the Old Testament (Princeton 1955). j.w. rogerson, Genesis 111 (Sheffield, 1991). g. j. wenham, Genesis 115 (Waco, TX, 1987). c. westermann, Genesis 111 (Minneapolis, 1984).

[j. e. jensen]

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Flood

Flood

Coastal floods
River floods and flash floods
Historically significant floods
Recent devastating floods
Flooding and climate change
For More Information

A flood is the overflow of water onto normally dry land. Flooding results when the water level rises and overflows the banks of a river or some other low-lying channel, or when high ocean waters wash over the coast. Floods occur frequently in some parts of the world. While for some areas flooding spells disaster, for other areas yearly flooding is necessary to sustain crops.

Floods kill more people than any other weather phenomenon. Flash floods, which are sudden, intense, localized floods, are especially deadly. Worldwide, 40 percent of all deaths from natural disasters are due to floods.

There are two main types of floods: coastal floods and river floods.

Coastal floods

Coastal floods are floods that occur along the coasts of lakes and oceans. This type of flooding is of great concern in many countries because of the high population density along their coastlines. In the United States, for example, almost two-thirds of the U.S. population lives in states along the three major coasts—38 percent along the Atlantic Ocean, 16 percent along the Pacific Ocean coast, and 12 percent along the Gulf of Mexico. According to the National Oceanic and Atmospheric Administration, 53 percent of the U.S. population (153 million people) live in one of the 673 counties bordering the Great Lakes, the Atlantic, the Pacific, or the Gulf of Mexico.

There are two main causes of coastal flooding: high waters and the subsidence, or lowering, of coastal lands.

Hurricanes and tsunamis

Most coastal flooding is produced by high waters associated with hurricanes. As a hurricane crosses over land, it produces a storm surge. A storm surge is a several-foot-high wall of water that results in the flooding of 40 to 100 miles (65 to 160 kilometers) of coastline.

Large waves can also cause flooding. The most common type of waves, those driven by the wind, are called wind waves. The largest wind waves are generated by large, stationary storm systems. Wind waves tend to be largest in the open ocean and diminish in height as they approach land. Large wind waves have the greatest potential for flooding when accompanied by high tide.

WORDS TO KNOW

coastal flood:
an overflow of water onto a coastal area caused by a storm surge, strong winds, or tsunami.
flash flood:
a sudden rush of water in a low-lying area brought on by heavy rain or a dam break; flash floods can occur when the ground is so saturated with water that no more can soak in, or in desert regions where hard rocky soil is unable to absorb or hold water.
flood:
an overflow of water on land that is normally dry.
precipitation:
water in any form, such as rain, snow, ice pellets, or hail, that falls to Earth's surface.
river flood:
a flood caused when a river spills over its banks.
sinkhole:
a natural, steep depression in a land surface caused by collapse of a cavern roof.
stationary front:
a boundary between two air masses at different temperatures which are not moving or are moving slowly.
storm surge:
an abnormal rise of the sea over and above normal tides and due to strong winds and low pressure accompanying a storm or hurricane.
subsidence:
a gradual sinking of the land surface relative to its previous level.
thunderstorm:
a storm resulting from strong rising air currents; characterized by heavy rain or hail along with thunder and lightning.
tornado:
a violent windstorm characterized by a twisting, funnel-shaped cloud.
tsunami:
a huge ocean wave that can travel at speeds up to 600 mph (965 kph) for hundreds of miles over open ocean before it hits land; caused by an earthquake, underwater volcanic eruption, or underwater landslide.
wind wave:
a wave caused by the action of wind on the water surface.

The largest waves, however, are generated not by the wind but by submarine earthquakes, landslides, and volcanic eruptions. Waves produced by these forces are called tsunamis (tsoo-NAH-meez). Tsunamis start out small and grow larger as they near land. They travel at speeds of up to 600 mph (965 kph). It is typical for a tsunami to measure 60 to 100 feet (18 to 30 meters) in height by the time it reaches the shore.

Tsunamis occur most often in the Pacific Ocean. Several tsunamis have affected Alaska and Hawaii. In 1958, a tsunami over 200 feet (60 meters) in height, generated by a minor earthquake and resultant rock fall into the sea, crashed into Lituya Bay, Alaska. It destroyed great tracts of forest land as far as 1,700 feet (520 meters) above sea level. In December 2004, the deadliest tsunami in recorded history occured not in the Pacific, but in the Indian Ocean. A powerful earthquake triggered a series of tsunamis in Indonesia, Malaysia, and Thailand, killing nearly a quarter million people. Because tsunamis are not common in the Indian Ocean, there was little advance warning for the people of southeast Asia.

On the shelves: The Epic of Gilgamesh

The Epic of Gilgamesh is a four-thousand-year-old story about a king from the region that is now Iraq. The story includes a controversial episode concerning a great flood that some historians and theologians say compares to the worldwide flood mentioned in the Bible.

Subsidence

Subsidence is the lowering of land in coastal areas. Subsidence may be caused by the gradual settling of subterranean rocks or sediments or by the removal of ground water by excessive pumping. Subsidence may also be rapid. For example, if the roof of a cave collapses, the result is a large depression called a sinkhole. Whatever the cause, subsidence in coastal areas makes them more susceptible to flooding.

River floods and flash floods

The banks of rivers and streams overflow due to many causes, including excessive rain, the springtime melting of snow, and blockage of water flow by ice. The failure of a dam or aqueduct is another source of flooding. The primary cause of flooding in large rivers is prolonged heavy precipitation over a large area. Large rivers such as the Mississippi, the Ohio, and the Missouri sometimes flood due to precipitation covering hundreds of square miles. In some areas, flooding occurs nearly every spring when the winter snow melts.

The most dangerous form of river flood is a flash flood. Flash floods are the number one weather-related killer in the United States. Throughout the 1980s, each year flash floods killed an average of 110 people and were responsible for an average of $3 billion in property damage. In the first half of the 1990s, the number of deaths due to flash floods rose to an annual average of 140.

A flash flood can be caused by persistent, torrential rain that falls from a slow-moving or stationary severe thunderstorm, which is itself a result of strong, rising air currents and characterized by thunder and lightning. A flash flood may also be caused by the failure of a dam or levee. A dam is a structure that controls the rate of water flow while a levee is a structure built to prevent water from overflowing the banks of a river.

Flash floods rise and recede much more quickly than other types of river floods. They are the most dangerous because they come on so fast that people are often unable to reach higher ground in advance of the floodwaters. A series of flash floods in the streams that feed into a large river may result in the flooding of the large river.

Watch this: River Voices: A Portrait of an American River Community

In this 2002 documentary, written and directed by Nathan Lorentz, survivors recall both the devastation and the outpouring of community strength caused by the great 1937 Ohio River flood in Portsmouth, Ohio.

Flash floods can be caused by thunderstorms that are either slow-moving or stationary. The reason for their lack of movement is that the high-altitude winds that drive weather systems winds are nearly calm. These storms unleash large quantities of rain over a single area. Thunderstorms that move more quickly spread their rain across larger areas and typically don't produce flash floods.

Weather report: Flash flood alerts and safety procedures

A flash flood watch means that heavy rains may cause flash flooding within the designated area. This is the time to prepare to evacuate to higher ground.

A flash flood warning means that a flash flood has been reported and is imminent for the designated area. In some areas, a warning signal sounds when waters reach critical levels. When a warning is issued, it is imperative to move to safe ground immediately. You may only have seconds or minutes before waters become dangerously high.

If you live in an area that's prone to flash flooding, it's wise to take the following precautions:

  • Learn the evacuation routes to higher ground.
  • Keep your car's gas tank filled.
  • Put together a supply kit for your home containing first aid materials, a battery-powered flashlight, a battery-powered radio, extra batteries, rubber boots, rubber gloves, nonperishable food, a nonelectric can opener, and bottled water.
  • Install check valves in your home's sewer traps to prevent flood water from backing up and coming in through your drains.
  • Once a flash flood watch has been issued, fill your bathtub and large containers with water for drinking and cooking in case your local water source becomes contaminated.

If you encounter a flash flood, the most important thing to remember is to avoid the water. If you are driving, turn around and go the other way. If you are on foot, climb to higher ground. Do not try to walk, swim, or drive through flood water. The water is moving rapidly and carries dangerous debris. You can be knocked over by as little as 6 inches of rushing water. Deeper water can have an undertow that drags you beneath the surface.

If you are in a car during a storm, watch for flooding where the road dips down, under bridges, and in low areas. These are the places that fill with water first. If you see a flooded area, turn the vehicle around and go the other way. Be especially careful at night, when the beginnings of flash floods are harder to recognize.

If your car stalls or becomes blocked, abandon the car and seek higher ground. A car will float away in just 2 feet of water. Then it is at the mercy of the current, which may carry it into deeper water or overturn it in a ditch. Sixty percent of people who die in flash floods are either in a car or are attempting to leave a car that has been stranded in high water.

A flash flood happens when the amount of rainfall exceeds the capacity of the ground to absorb it. In that case, the rainwater runs over the surface, rather than sinking into the ground. The water flows to the lowest point, which is generally a river, stream, or storm sewer. If the quantity of water is greater than the capacity of the drainage channel, the channel overflows within a few minutes and a flash flood occurs.

As the banks overflow, water rushes forward at speeds of up to 20 mph (35 kph). It takes the form of a sediment-laden wall that can surge as high as 30 feet (10 meters). The floodwaters are capable of dislodging large objects weighing several tons, such as boulders, cars, and even locomotives. These objects may be carried several miles downstream. Flash floods are also known to tear out bridges in their path.

Flash floods are more common in mountainous areas. Rain runs down mountainsides and becomes concentrated in canyons and valleys. Arid and urban regions are also prone to flash floods, since very little rain can soak into hard desert surfaces or concrete. Most cities have storm sewer systems that direct water underground to nearby rivers. If the storm sewers become clogged or overwhelmed by the volume of water, the streets quickly become flooded.

Flash flooding may also result from rains associated with a hurricane, a break in a dam or levee, or the springtime melting of large quantities of snow and ice. Flooding may even be caused by a small amount of rain that falls on a blanket of snow. If the ground beneath the snow is frozen, the melting snow and rain will not soak into the ground, but will run off and drain into a river. The likelihood of flooding is increased if ice blocks water from flowing in the river.

Historically significant floods

In 1889, a dam break in Johnstown, Pennsylvania, resulted in the worst flash flood in the history of the United States. A wall of water 36 to 40 feet (11 to 12 meters) tall overwhelmed the town, killing over 2,200 people. A second flash flood hit Johnstown in 1977, in which seventy-seven people lost their lives.

The Great Mississippi River Flood of 1927 caused widespread damage over a large area, extending from southern Illinois to the Gulf of Mexico. Flooding began after a year of above-normal precipitation. Water levels along the Mississippi, and rivers flowing into the Mississippi, were already high when 9 inches (22 centimeters) of rain fell on southern Missouri and most of Arkansas in April.

Did you know? Floods and the spread of disease

Cholera, dysentery, and typhoid are diseases that typically spread during floods, when sewage treatment systems become overloaded and drinking water supplies become contaminated. An abundance of standing water also promotes the breeding of mosquitoes, which may carry malaria, dengue fever, yellow fever, and encephalitis (pronounced en-cef-a-LIE-tis).

In 1982, flooding in Ecuador, Bolivia, Colombia, Peru, India, and Sri Lanka resulted in epidemics of malaria. In early 1998, a malaria outbreak hit Peru because of flooding. In the Piura region of northwest Peru, home to 1.5 million people, there were some thirty thousand cases of the disease.

Beginning in April, the river flooded over hundreds of square miles. Levees failed in more than 120 places on the Mississippi and its tributaries. Over twenty-six thousand square miles (seven thousand square kilometers) were flooded

across seven states. Six hundred thousand people were forced from their homes and, despite advance warnings, 246 people were killed.

In the summer of 1993, excessive rains caused what is called "The Great Flood of 1993," one of the largest floods in the history of the United States. Water overflowed the banks of the Mississippi and Missouri Rivers, inundating 16,000 square miles (41,000 square kilometers) of land in Iowa, Illinois, Minnesota, Missouri, Wisconsin, South Dakota, Nebraska, and Kansas. The Mississippi River swelled to over 7 miles (11 kilometers) wide in some places. Fifty-six small towns along the river were completely submerged in water.

The flooding was preceded by heavy snowfalls throughout the Midwest in December 1992. The snow melted in March, and then 16 inches (41 centimeters) of rain fell in the upper Mississippi Valley in April. The rains continued through July. In mid-June, a stationary front, which is a slow-moving boundary between two air masses at different temperatures, formed across the upper Midwest and began producing daily thunderstorms.

The water reached record heights at many points along the Mississippi River and more than 60 percent of levees on the river were destroyed. Forty-eight people died. There was $6.5 billion in crop damage, out of a total property damage of $15-20 billion. Eighty-five thousand people were evacuated from their homes. Forty-five thousand homes were damaged or destroyed and 404 counties were declared disaster areas. Counties that are designated "federal disaster areas" are eligible to receive federal disaster aid including low-interest loans.

Extreme weather: Killer flash floods

One of the most destructive flash floods in recent history occurred in Colorado's Big Thompson Canyon, in the mountains west of Denver, in July 1976. Ten to twelve inches (25 to 30 centimeters) of rain, over half the yearly average rainfall for that location, caused the overflow of the river running through the narrow canyon floor. A wall of water 20 feet (6 meters) high rushed forward, killing at least 139 people. More than 400 houses were destroyed, many roads were washed away, and 197 vehicles were lost in the flood. Approximately one thousand people were rescued by helicopter.

In June 1990, a flash flood occurred in Shady-side, Ohio, when 4 inches (10 centimeters) of rain fell in less than two hours. The resultant 30-foot (9-meter) wall of water killed twenty-six people and caused around $7 million in damages.

Cheyenne, Wyoming, was beset by a flash flood in August 1985, after 6 inches (15 centimeters) of rain fell in three hours. The streets were filled with more than 6 feet (about 2 meters) of water. The flood caused the deaths of twelve people and more than $65 million in damage.

Another of the worst floods in U.S. history ravaged parts of the Midwest and Southeast in March 1997. The disaster was touched off when a series of severe thunderstorms and tornadoes, violent funnel-shaped windstorms, swept through Arkansas, Tennessee, and Mississippi and killed at least twenty-five people. Flash floods and gusting winds killed thirty-six more people in Kentucky, Ohio, West Virginia, and Tennessee, bringing the death toll to sixty-one.

Due to the tornadoes, eleven counties in Arkansas were declared federal disaster areas. Due to floods, sixteen counties in Ohio and sixty-three counties in Kentucky were also declared federal disaster areas.

During the floods, occasional heavy rains continued to fall throughout the region, accompanied by melting snow. On a single day, March 1, nearly a foot of rain fell on north-central Kentucky, southern Ohio, and West Virginia. New rainfall records were set in Louisville, Kentucky, on that day. Two days later, up to 9 more inches (23 centimeters) of rain fell on the same area.

Watch this: The Johnstown Flood

Using archival film and photographs, this documentary recreates the story of the Johnstown flood of 1889. The South Fork Dam burst due to very heavy rains and poor maintenance, sending a wall of water and debris downstream to flood the industrial city of Johnstown, Pennsylvania. The film, written and directed by Charles Guggenheim and released in 1989, won an Academy Award for best documentary, short subject.

As a result, flooding occurred along the Ohio, Missouri, and Mississippi Rivers, as well as on numerous tributaries. Rivers throughout Kentucky rose to record levels. Many river towns in Ohio, Kentucky, Tennessee, and West Virginia were swamped. Thousands of people from

flooded river towns were left homeless. The estimated flood damage in Kentucky was $232 million and in Ohio, $40 million.

China's Joy; China's Sorrow

Somewhere between nine hundred thousand and two million five hundred thousand people living in the crowded river valleys perished during the 1887–88 flooding of China's Huàng Hè (Yellow River). This flood was, by far, the most devastating in recorded history.

The Yellow River, nicknamed "China's Sorrow," is one of the world's most flood-prone rivers. Records show that there have been around 1,500 floods on the Huàng Hè over the last 3,500 years, many of which killed large numbers of people.

According to reports by CNN news on March 7, 1997, Falmouth was one of the hardest-hit areas. The town was built on the banks of the Licking River, a tributary of the Ohio River. When Falmouth residents were allowed to return and survey the damage, they saw extensive damage to their homes and businesses. Houses were moved from their foundations, their walls warped and roofs collapsed. The National Guard had plowed the streets, but a thick layer of brown, gooey mud coated everything else. The Cincinnati Enquirer reported on March 2, 1997, on a helicopter flight taken by Kentucky State Police Trooper Jan Wuchner over Falmouth. Wuchner was stunned. His report was short and to the point: "There is no Falmouth."

Recent devastating floods

In July 2006, news media reported that floods in North Korea caused at least hundreds and maybe even thousands of deaths and left many more people homeless. Since North Korea is a closed country that tightly controls information, exact figures on losses of life and property are hard to determine. But the United Nations Food Agency reported sixty thousand homeless, seven thousand homes destroyed or damaged, and almost forty thousand acres (sixteen thousand hectares) of farmland washed away. One indication of the size of the disaster is that the government of North Korea cancelled the Arirang Festival of dance and mass gymnastics, which is a major tourist attraction and a key source of income for the nation. North Korea also closed its border to tourists from China, another major source of income.

Did you know? Dams for flood control

The construction of river dams is a common method of storing water and lessening the impact of drought. Dams are also used in flood control. A dam is a barrier that blocks a river and controls the flow of water. When a river is dammed, the water backs up in the area behind the dam, creating an artificial lake or reservoir (pronounced REH-zer-vwar). Pipes carry the water from the reservoir to factories, homes, and farms. This ready supply of water is especially useful during times of drought. By the year 2000, there were more than sixty thousand dams in use worldwide.

Large dams, defined as those that are more than 492 feet (150 meters) high, or holding back more than 19.6 million cubic yards (15 million cubic meters) of water, have a significant impact on the surrounding community and environment. When a dam is constructed in a valley, it floods the area upstream, putting homes, farmland, and even whole villages underwater. In the process, it displaces the people who inhabit the area. Dams also disrupt a river's natural cycle of flooding. When a river floods a valley, it deposits a layer of silt that enriches the soil. After the river is dammed, the fertile soil is lost. (The soil upstream is buried beneath the reservoir, and the soil downstream remains exposed but becomes less fertile over time.) Dams also disrupt the balance of the river ecosystem, destroying the habitat of birds, fish, and other animals, as well as many species of plants.

China also suffered disastrous floods from at least eight typhoons during the storm season of 2006. On August 10, 2006, Typhoon Saomai struck China's southeast coast with winds of 170 mph (270 kph). It was the most powerful typhoon to hit China in fifty years. The storm sank over one thousand ships and destroyed or damaged at least fifty thousand houses. More than 1.6 million people fled their homes to avoid the storm and at least 399,999 acres (122,000 hectares) were flooded. Saomai was the second major typhoon to strike China that same month. The government reported that prior to Saomai, economic losses in China already exceeded $9.4 billion.

India has also suffered severe flooding. In 2005, the Indian state of Maharashtra, which includes Mumbai (formerly Bombay), experienced floods that caused the deaths of at least one thousand people. The flooding was caused by the eighth heaviest rainfall ever recorded within a twenty-four-hour period. Then, during July 25 and 26, 2006, 37.2 inches (944 mm) of rain fell. Heavy rains continued over the next few days and forced the closing of schools in Mumbai and surrounding areas.

Later that summer, widespread flooding due to the summer monsoon (seasonal rains caused by shifts in prevailing winds) displaced at least 4.5 million people in the states of Orissa and Gujarat. Rajasthan also suffered unusually heavy flooding due to monsoon rains, with over eight hundred thousand people affected and tens of thousands displaced.

Flooding and climate change

In any given week, a river flood or other flood is certain to be happening somewhere in the world. However, in recent years floods seem to be getting more severe. According to the World Meteorological Organization, floods affected 1.5 billion people in the last decade of the twentieth century alone.

Floods in popular music

There have been many songs written about great floods. Some of the songs have become classics of popular music. The song by Randy Newman, "Louisiana 1927," is a heavily sarcastic and fictional account of the government's response to the Great Mississippi River Flood of 1927. It has been recorded many times by different performers. "Requiem" is a song by Eliza Gilkyson that she composed in response to the floods from the Indian Ocean tsunami of 2004. Both of these songs were played often on many radio stations after the floods in New Orleans and other parts of the Gulf Coast caused by Hurricane Katrina.

After the flood waters that devastated the Gulf Coast in 2005 receded, many other performers and songwriters performed or composed songs in response to the tragedy. An unprecedented number of New Orleans tribute records and benefit concerts appeared, with pop stars such as Norah Jones, Prince, and the Dixie Chicks, among others, trying to help. Many of New Orleans's musicians and songwriters have also composed responses to the storm. Allen Toussaint teamed with Elvis Costello to create The River In Reverse. New Orleans native Dr. John's jazz offering was Sippiana Hericane. It included the heart-wrenching song and plea "Clean Water."

While climate researchers and other scientists have not come to universal agreement on whether there is a direct link between short-term extreme weather and long-term climate change, many of the weather patterns observed are similar to those predicted by models of climate change. For example, the landmark Second Assessment Report (AR2) published in 1995 by the United Nations Intergovernmental Panel on Climate Change (IPCC), predicted that global warming would leave southern China drenched with more rains, while the north and west of the country would suffer worsening droughts. This is very similar to the observed pattern, with droughts in the northern provinces and floods in the south.

Extreme weather: The Grand Forks flood of 1997

In April 1997 entire towns were submerged in floodwaters when the Red River, which runs between North Dakota and Minnesota, overflowed its banks. The floods took seven lives in North Dakota and four in Minnesota. In North Dakota about ninety thousand head of livestock died. Property damages throughout the Red River Valley (the areas of North Dakota and Minnesota along the banks of the Red River) totaled $3 billion. Most of the destruction occurred in Grand Forks, North Dakota, 90 percent of which was flooded.

Floods for the region had been predicted as early as February because of the several heavy snowstorms that took place that winter. In North Dakota, houses were buried up to their roofs in snow. In March the snow began to melt and, as predicted, the rivers overflowed.

In any case, the main cause of loss of life and damage to property due to flooding is the tendency of humans to build homes and other structures near water. For thousands of years, humans have depended on rivers for food, for transportation, for reliable sources of drinking water, and for water used in agriculture. Similarly, the oceans have long been an important food source. While many people do need to live and work near the water, the continued building of homes and recreational housing in flood-prone areas will only make the problems of damage and loss of life more difficult to control.

[See AlsoClimate Change and Global Warming; Human Influences on Weather and Climate; Hurricane; Local Winds; Thunderstorm; Tsunami; Weather: An Introduction ]

For More Information

BOOKS

Drohan, Michele Ingber. Floods. New York: Rosen Publishing and PowerKids Press, 1999.

Miller, E. Willard and Ruby M. Miller. Natural Disaster: Floods. Santa Barbara, CA: ABC-Clio, 2000.

Waterlow, Julia. Violent Earth: Flood. New York: Hodder Children's Books, 1994.

WEB SITES

"Flood." Federal Emergency Management Agency. 〈http://www.fema.gov/hazard/flood/index.shtm〉 (accessed March 8, 2007).

"Flood Safety." National Weather Service Flood Safety. 〈http://www.floodsafety.noaa.gov/〉 (accessed March 9, 2007).

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Floods

Floods

Floods can be defined as an overflow or downpour of water accumulating in an area where water is normally absent. Floods usually occur within a short period of time due to the soil's inability to absorb the water fast enough. According to the United States Geological Survey, floods were the natural disaster that caused the highest number of deaths and the most property damage in the United States during the twentieth century. Of all the natural disasters, floods are the most common and occur in the most places, with the only exception being fire. Flooding results in heavy currents that have the capacity to loosen structures and collapse foundations, destroying even the toughest of buildings.

The most common type of flood is the regional flood. Regional floods typically occur during the winter and spring months when the snow melts too rapidly or an excessive amount of water falls too quickly during spring rains or thunderstorms. Additionally, regional floods can result from tropical storms or hurricanes occurring along the coast or even far inland due to drastic changes in weather patterns. Floods can occur with no warning, but often occur over a period of days. If cold temperatures keep the ground frozen or the ground is already immersed with water, the water will run off into rivers . However, all too quickly the water rises above the banks of the rivers and flows onto dry land. Other types of floods include flash floods, ice-jam floods, storm-surge floods, damfailure floods, and debris, landslide , and mudflow floods.

Regional floods across the U.S. that have occurred since 1990, include the Trinity, Arkansas, and Red Rivers in Texas, Arkansas, and Oklahoma in April of 1990, each caused by recurring thunderstorms. The number of reported deaths was 17 and the approximate cost of damage was one billion dollars. In January of 1993, the Gila, Salt, and Santa Cruz Rivers in Arizona flooded due to persistent winter precipitation , causing 400 million dollars in damages with the number of deaths unknown. From May through September of 1993, the Mississippi River Basin in the central U.S. flooded due to excessive rainfall, causing 48 deaths and 20 billion dollars in damages. In May 1995, flooding occurred in the south central U.S. from recurring thunderstorms causing 32 deaths and over five billion dollars in damages. Winter storms in California killed 27 people and caused three billion dollars in damages between January and May of 1995. Torrential rains and snowmelt caused flooding in the Pacific Northwest and western Montana in February of 1996 and again between December 1996, through January 1997. This caused nine deaths and one billion dollars in damages and 36 deaths and over two billion dollars in damages, respectively. The Ohio River and its tributaries flooded in March of 1997, causing more than 50 deaths and 500 million dollars in damages from a slow-moving frontal system. Snow melting caused the Red River of the North in North Dakota and Minnesota to flood between April and May of 1997, causing eight deaths and two billion dollars in damages. In September 1999, Hurricane Floyd destroyed eastern North Carolina, causing 42 deaths and six billion dollars in damages.

Flooding does not always prove destructive. Occasionally, floods can be beneficial, leaving soil laden with minerals and organic matter from the debris carried by the flood. Annual flooding of the Nile River enabled agriculture to be the foundation for Egyptian civilization. At the same time each year, the Nile River would flood, providing enough water to the soil to make lands fertile. With little rainfall, the Egyptians were dependent on the annual flooding to sustain their agriculture. Accordingly, Egypt's soil containing minerals and organic debris was a result of river sediment brought by the yearly floods.

See also Debris flow; Mud flow; Sedimentation

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Floods

Floods

Introduction

Climate is an important influence of floods. A winter thaw or rainy spring can send amounts of water into a river that are greater than the capacity of the water-course. The excess water has to go somewhere, and the result can be flooding of adjacent land. The vast majority of scientists have come to accept the reality of global warming—the warming of the atmosphere due to human activities. One consequence of the world's changing climate may be increased rainfall and flooding.

Historical Background and Scientific Foundations

For thousands of years, people have settled in low-lying land next to rivers, lakes, or other watercourses. Although the fertile soil is ideal for growing crops, the land is vulnerable to flooding. In 2007, flooding remained the most damaging of all natural disasters. One-third of all the natural disasters occurring around the world each year are floods, and more than 50% of disaster-related deaths are due to floods.

In the wake of Hurricane Katrina in August 2005, for example, nearly every levee in the downtown region of New Orleans, Louisiana, was breached, and the resulting flooding turned 80% of the city into a lake. The hurricane- and flood-related damage in New Orleans topped $80 billion; more than 1,000 people died. Over the entire affected Gulf Coast region, the death toll exceeded 2,200 and damage approached $130 billion. As of early 2008, the region had yet to fully recover.

The devastation of Hurricane Katrina is an example of flooding caused by a storm surge, where strong winds push water onto shore. In the case of Hurricane Katrina, the storm surge was huge; in one documented example, waves that struck a Gulfport, Mississippi, hotel were approximately 10 ft (3 m) high, even though the hotel was 250 yd (230 m) from the shoreline and 19 ft (6 m) above sea level. Calculations revealed that the surging waves were 28 ft (8.5 m) high when they came ashore.

Much smaller flood surges are still capable of causing a great deal of damage. Anyone who has tried to wade into the ocean surf and who has been thrown off balance by waves less than a 1 ft (.3 m) tall can attest to the power packed by a wave. In a flood, waves that are several feet tall can wash away an average-sized car. Powerful floods that last hours or days can throw houses off their foundations.

Other floods are caused by heavy rainfall or a sudden snowmelt, which inundates a watercourse with a greater volume of water than the watercourse can handle. Also, the soil that borders the river, stream, or lake becomes saturated with water. This is especially true for clay-rich soil or soil that has been compacted. When this happens, any additional water cannot be absorbed by the soil, and it flows into the watercourse.

A watercourse with a shoreline that is rocky or close to a parking lot (where the water-absorbing soil has been replaced by asphalt) is more prone to flooding than, for example, one with a forested shoreline capable of absorbing water.

Floods can occur in a fairly predictable pattern. A historic example is the Nile river, which, before the construction of dams to control water flow, tended to flood with the increase of rain in the spring. This type of flooding tends to be less destructive because those living near the river anticipate it. In addition, the nutrients that are washed onto the land by the flood are left when the flood waters recede, making the land very fertile for growing crops.

Floods that occur with no warning are known as flash floods. These floods typically occur when a large amount of rain falls in a short time, such as in a monsoon. The sudden appearance of the excessive amount of water in a small watercourse can create a wall of water that rushes downstream. Just as quickly, the water level can return to normal. In July 2007, for example, a series of flash floods caused by heavy seasonal rains ravaged eight states in the African country of Sudan, killing more than 100 people

Undersea earthquakes release a great deal of energy, which pushes the surrounding ocean water outward from the origin of the earthquake. The result is a ripple effect, similar to the ripples created when a rock is dropped into a pond. The series of waves is called a tsunami. Moving at hundreds of miles per hour, the waves can devastate coastal regions. On December 26, 2004, a magnitude 9.0 earthquake off the coast of Sumatra spawned a series of waves that obliterated coastal villages in Sri Lanka, Thailand, Myanmar, India, and elsewhere. More than 155,000 people were killed in Sri Lanka alone.

Impacts and Issues

The flash floods experienced in Sudan in the summer of 2007 have affected 21 other African nations including Uganda, Ethiopia, Democratic Republic of the Congo, and Ghana, displacing more than 700,000 people and killing at least 300 people as of October 2007. At the same time, regions of the United Kingdom were affected by severe floods triggered by June rains of 5.5 in (14 cm), more than double the historic average for the month. Some regions of Britain experienced the most monthly rainfall ever recorded.

Hurricane Katrina was one of the 28 tropical and subtropical storms, and one of the 15 hurricanes that occurred during the 2005 hurricane season. As of late 2007, the 2005 season stood as the most active Atlantic hurricane season ever recorded.

These examples may have their origin in the changing global climate, which the majority of scientists agree is influenced, if not determined, by the warming of the atmosphere. This warming trend, which has been evident since the middle of the nineteenth century, and which coincides with the increased industrialization in developed countries, is popularly known as global warming. Altered air currents in the changing atmosphere can affect weather patterns, with some regions having more rainfall and other regions experiencing drought.

A pair of 2002 studies published in Nature highlighted the influence of climate on the occurrence of floods. The studies assessed data from all over the globe on the occurrence of 100-year-floods—those that are so severe that they are predicted to occur very rarely—and on 19 climate models. They revealed an increased frequency of major floods since the mid-twentieth century, and related the increase to global warming.

The World Water Council, a think-tank of water users and suppliers concerned with water-related social and economic issues, has predicted that by 2025 about half of Earth's population will live in areas that will be at increased risk of severe storms and other extreme weather. One consequence could be increased frequency of floods.

WORDS TO KNOW

CLIMATE MODEL: A quantitative way of representing the interactions of the atmosphere, oceans, land surface, and ice. Models can range from relatively simple to quite comprehensive.

MONSOON: An annual shift in the direction of the prevailing wind that brings on a rainy season and affects large parts of Asia and Africa.

STORM SURGE: Local, temporary rise in sea level (above what would be expected due to tidal variation alone) as the result of winds and low pressures associated with a large storm system. Storm surges can cause coastal flooding, if severe.

TSUNAMI: Ocean wave caused by a large displacement of mass under the surface of the water, such as an earthquake or volcanic eruption.

Computer models have been used for decades to help understand weather patterns and predict the weather. Daily weather forecasts rely on computer projections along with the monitoring of data. Similarly, flood modeling software exists. Information on the size, shape, and topography of the area that drains into the particular watercourse; the types of soil present in the area; typical weather patterns; and land use are used to better understand how changing parameters affect the potential for flooding. Such models help scientists better understand how climate changes in the real world affect flooding.

See Also Erosion; Forests and Deforestation; Hurricanes; Rainfall.

BIBLIOGRAPHY

Books

DiMento, Joseph, and Pamela M. Doughman. Climate Change: What It Means for Us, Our Children, and Our Grandchildren. Boston: MIT Press, 2007.

Hulme, Mike. Nature's Revenge?: Hurricanes, Floods and Climate Change. New York: Hodder & Stoughton, 2003.

Morgan, William W. The Biblical Flood: Global Warming & Bush's Harvest. Charleston: Book Surge Publishing, 2007.

Periodicals

Milly, P. C. D., R. T. Wetherald, K. A. Dunne, and T. L. Delworth. “Increasing Risk of Great Floods in a Changing Climate.” Nature 415 (2002): 514–517.

Palmer, T. N., and J. Raäisaänen. “Quantifying the Risk of Extreme Seasonal Precipitation Events in a Changing Climate.” Nature 415 (2002): 512–514.

Web Sites

“Causes of Flooding.” Environment Canada. < http://www.ec.gc.ca/water/en/manage/floodgen/e_cause.htm> (accessed October 31, 2007).

“In Depth: Forces of Nature—Flooding.” Canadian Broad casting Corporation (CBC), June 20, 2005. < http://www.cbc.ca/news/background/forcesofnature/flooding.html> (accessed October 31, 2007).

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Floods

Floods

Theme Overview

Floods are among the most powerful and devastating of natural events. Long after the water has gone, people remember and talk about the loss and destruction. Sometimes, the scale of devastation is great enough to convince people that the flooding is the work of supernatural beings.

It is no surprise that flood myths occur in cultures around the world. One of the most common tells of a great flood that occurred in the distant past. The biblical story of Noah (pronounced NOH-uh) and the ark (a boat) he built to save certain people and animals from the flood is just one version of a much older myth from Mesopotamia. Similar stories appear wherever people have experienced floods.

Major Myths

Although the details of the stories differ, flood myths from around the world have many similarities. The themes of punishment, survival, and rebirth or renewal occur frequently.

Ancient Near East The basic flood myth of the ancient Near East, in which the flood was sent as a divine punishment, originated among the Sumerian cities in southern Mesopotamia. Over a period of several thousand years, the Babylonians, the Hebrews, and other civilizations developed their own versions.

The Sumerian myth tells how the human race, which the gods had created to do their work, became so numerous and noisy that the god Enlil (pronounced EN-lil) sent a flood to destroy it. However, another god, Enki (pronounced EN-kee), wanted to save King Ziusudra (pronounced zee-oo-SOO-druh). Forbidden by Enlil to warn the king, Enki spoke to the king's reed house. The king overheard the warning, built a boat, and saved his family and a collection of animals.

The Babylonian version of the flood myth appears in the Epic of Gilgamesh. In this account, the survivor is a man called Utnapishtim (pronounced oot-nuh-PISH-tim). Warned of the flood by a dream in which he heard a god whispering to his reed house, Utnapishtim built a boat, took aboard his family and a selection of craftspeople and animals, and rode out a terrible storm that raged for six days and six nights. Finally the boat landed on a mountaintop, the only land above the flood. Utnapishtim and his wife became immortal, or able to live forever, as a reward for following the advice of the god in the dream.

The Hebrew version of the story, told in the book of Genesis in the Bible, places greater emphasis on the sinfulness of humankind. The flood was not a cruel whim or mistake of the gods but a deliberate punishment. Like Utnapishtim, Noah was a good man who received a warning and instructions to build a boat. He and his family, and two of every sort of living thing, survived the flood and landed upon the peak of Mount Ararat.

Egypt The Egyptian flood myth begins with the sun god Ra (pronounced RAH), who feared that people were going to overthrow him. He sent the goddess Hathor (pronounced HATH-or), who was his eye, to punish the people. But she killed so many that their blood, flowing into the Nile River and the ocean, caused a flood. Hathor greedily drank the bloody water. Feeling that things had gone too far, Ra ordered slaves to make a lake of beer, dyed red to look like blood. Hathor drank the beer, became very drunk, and failed to finish the task of wiping out humanity. The survivors of her bloodbath started the human race anew.

Ancient Greece The Greek flood myth says that Zeus (pronounced ZOOS), father of the gods, sent a mighty inundation to destroy the human race. Some versions say that Zeus was angry at the Titan Prometheus (pronounced pruh-MEE-thee-uhs) for stealing fire from the gods and giving it to people. Others say that the flood was punishment for human sinfulness. Prometheus warned his son Deucalion (pronounced doo-KAY-lee-uhn) to escape the flood by building a boat. Deucalion and his wife survived, and when the flood waters retreated, they were the only humans left on earth. The couple began the race of people who inhabit the world today. The story of the flood, along with many other Greek myths, appears in the Metamorphoses by the Roman poet Ovid.

China For thousands of years, the Chinese people have suffered from the flooding of the two great rivers that flow through their land, the Chang Jiang (Yangtze) and the Huang He (Yellow) Rivers. Taming the rivers was one of the chief goals of early Chinese civilization. The story of Yu, one of several Chinese flood myths, celebrates a victory in the long struggle against floods.

In the myth, a man named Gun tried for nine years to dam the destructive waters that covered the land. Because he failed, the supreme god executed him. Gun's son, Yu, took up the task of taming the waters. Instead of building a dam, he decided to drain away the floodwaters through channels. A winged dragon flew in front of him, marking with his tail where Yu should dig the channels. Yu worked for many years, too busy even to see his family. In the end, however, he tamed the rivers, making the land along them suitable for farming. As his reward, Yu became emperor of China.

The Yao people of southern China have a myth that tells how the thunder god caused a great flood. A man captured the god to stop the rains, but the god convinced the man's son and daughter to set him free, and the flooding resumed. The man built a boat and floated to heaven to ask the other gods to help. They were too helpful. The water god drained the flood away so rapidly that the boat crashed to earth, killing the man. His children, meanwhile, were the only survivors of the flood. They floated on the water in a large gourd that grew from a tooth the thunder god had given them. They became the parents of a new human race.

India The flood legend of India begins with a creator god named Manu (pronounced MAN-oo) washing himself with water from a jar. A fish in the jar asked for Manu's protection and promised to save him from a great flood that would occur in the future. Manu raised the fish until it was one of the largest fish in the world, and then he released it into the sea. The fish told Manu what year the flood would come and advised him to build a ship. Manu built the ship, and when the flood came, the fish towed it to a mountaintop. Manu alone survived the flood. The fish is generally identified as one form of the god Vishnu (VISH-noo).

North and Central America In many American Indian myths, floods occur as punishment for human misdeeds. The Chiricahua Apache maintain that the Great Spirit sent a flood to drown the whole earth because people did not worship him. According to the Navajo, a series of floods forced the people to emerge from deep in the earth through several higher worlds. The final flood was caused by Water Monster, who became angry when Coyote stole his child. This flood, which drove the people to the surface of the present world, ended when Coyote returned the Water Monster's baby. The Cheyenne say that the gods use floodwaters to control people's movements.

Floods also have positive powers. In myths of the Arikara and Caddo people, floods wipe out evil giants and make the world safe for humans. Several Indian mythologies in Mexico and the American West tell of cycles of destruction in which one whole world creation was destroyed by flood, while others ended in fire, ice, wind, or other disasters. The Aztecs believed that the first age of creation ended in a flood. In the Mayan creation story, a flood washed away the wooden people made by the gods in an early attempt to create human beings.

Australia Several groups among the Aborigines, the native people of Australia, believe that a vast flood swept away a previous society. Perhaps these myths grew out of conditions at the end of the last Ice Age, when sea levels rose, and coastal regions flooded.

The Lost Continent of Atlantis

The ancient Greek philosopher Plato mentioned in his writings a highly advanced civilization that existed around 9000 bce that was swallowed by the sea in one disastrous day of earthquakes and flooding: it was called Atlantis. Whether or not Atlantis ever actually existed has been the subject of debate ever since, as geographers, adventurers, and historians through the centuries have proposed different possible locations of the lost civilization and different theories about how it met its end. Many cultures have similar “lost civilization” legends that describe privileged, wise people who are suddenly destroyed—often by a flood.

One group of Aborigines says that their ancestral heroes , the Wandjina (pronounced wand-JIN-uh), caused the flood and then recreated society in its present form. Another version of the myth tells that a huge half-human snake called Yurlunggur (pronounced YUR-lun-gur) brought on the flood to punish two sisters for sexual misbehavior, that is, for breaking tribal rules concerning proper partners. Yurlunggur swallowed the sisters, but after the floodwaters withdrew, he spat them out and allowed them to start a new society.

Floods in Context

Some scholars believe that memories of real disasters, such as the violent and unpredictable floods that occurred along Mesopotamia's Tigris and Euphrates Rivers, underlie mythological accounts of catastrophic rains and floods. These stories give meaning and purpose to events in the natural world. In myths, floods become part of a cycle of destruction and rebirth.

Mythological floods are not local. They take place on a grand scale, generally covering the whole world. Though the direct cause of the rising waters may be heavy rainfall, gods or other supernatural beings are responsible. Often the flood is sent as punishment for the wrongdoings of humankind.

In some traditions, a flood reproduces the original mythological conditions of creation—the formless, empty expanse out of which the world was created. The flood not only destroys the old world but also sets the stage for a brand new one. In myths in which the flood was sent to punish people for their sins, the new world that follows the flood is purified. The religious ritual of baptism reenacts the flood myth on an individual level. The baptismal water is believed to wash away sins, allowing people to be reborn in a purified state. In India, Hindus bathe in the sacred Ganges River to purify themselves.

According to many myths about great floods, a few virtuous individuals survive the deluge, perhaps with the help or advice of a friendly deity (god). Those survivors repopulate the world, becoming the parents of the present human race. In this way, flood myths are often myths of human origins as well.

Floods in Art, Literature, and Everyday Life

Of all the floods in mythology, the flood described in the Bible has inspired more artists than any other. Images of Noah and the biblical deluge can be found throughout European and American art, with famous examples by Michelangelo, Gustave Doré, Jacopo Bassano, and Edward Hicks. Mythological floods have even appeared on film; the Disney animated film Fantasia 2000 contains a sequence re-telling the myth of Noah with Donald Duck filling the role, while the 2007 comedy Evan Almighty casts Steve Carell as a modern-day version of Noah.

Read, Write, Think, Discuss

When Hurricane Katrina struck the United States Gulf Coast on August 29, 2005, it caused massive flooding. Hundreds were killed as the world watched in helpless horror. Soon after, dozens of religious and political leaders claimed the disaster was proof that God was punishing the United States. Some pointed the finger at the “wickedness” of the city of New Orleans, which was particularly hard-hit. Others said American policy in the Middle East had caused the divine punishment. What do you think of these ideas? Why do some people see natural disasters as a sort of divine punishment?

SEE ALSO Creation Stories; Gilgamesh; Manu; Noah

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Floods

Floods

Introduction

A flood is any unusual, temporary submergence of some area of land. Flooding can be caused by intense rainfalls or snowmelts that swell rivers and streams, the breaching of dams or dikes, temporary rises in sea level during hurricanes, or any combination of such factors. For example, a fast spring thaw combined with a heavy rainstorm can send amounts of water into a river that are greater than the capacity of the watercourse. The excess water has to go somewhere, and the result can be flooding of adjacent land.

Floods can destroy property and endanger lives. Over 520 million people are affected by floods every year, with about 25,000 killed. In 2004, the United Nations University forecast that the number of people vulnerable to catastrophic flooding was likely to increase from about 1 billion in the early 2000s to over two billion by 2050 due to the effects of global climate change and other human activities, such as deforestation and increasing settlement of flood-prone areas. Even attempts to control flooding, such as the extensive reengineering of the Mississippi River in the United States, can increase the chances of catastrophic floods.

However, flooding is also a natural and beneficial process in many ecosystems. For example, the fertile soils in many floodplains (low-lying, flood-prone areas of land adjacent to a river) are created by periodic flooding, which delivers soil particles from upstream and spreads them over the land. The Nile River valley is a prime example of fertility created by seasonal flooding—flooding prevented, since 1970, by the Aswan High Dam.

Historical Background and Scientific Foundations

For thousands of years, people have settled in low-lying land next to oceans, rivers, lakes, or other watercourses. Although the fertile soil in these areas is ideal for growing crops, such land is vulnerable to flooding. Flooding remains the most damaging of all natural disasters. About a third of all the natural disasters occurring around the world each year are floods, and more than 50% of disaster-related deaths are due to floods.

In the wake of Hurricane Katrina in August 2005, for example, nearly every levee (raised-earth water barrier) in the downtown region of New Orleans, Louisiana, was breached, and the resulting flooding turned 80% of the city into a lake. The hurricane- and flood-related damage in New Orleans topped $80 billion and more than 1,000 people died. Over the entire affected Gulf Coast region, the death toll exceeded 2,200 and damage approached $130 billion. As of 2008, the region had yet to fully recover.

The devastation of Hurricane Katrina is an example of flooding caused by a storm surge, where strong winds push water onto shore. In the case of Hurricane Katrina, the storm surge was huge; in one documented example, waves that struck a Gulfport, Mississippi, hotel were approximately 10 ft (3 m) high, even though the hotel was 250 yd (230 m) from the shoreline and 19 ft (6 m) above sea level. Calculations revealed that the surging waves were 28 ft (8.5 m) high when they came ashore.

Much smaller flood surges are still capable of causing a great deal of damage. Anyone who has tried to wade into the ocean surf and who has been thrown off balance by waves less than a one ft (0.3 m) tall can attest to the power packed by a wave. In a flood, waves that are several feet tall can wash away an average-sized car. Powerful floods that last hours or days can shove houses off their foundations.

Other floods are caused by heavy rainfall or a sudden snowmelt, which inundates a watercourse with a greater volume of water than the watercourse can handle. Also, the soil that borders the river, stream, or lake becomes saturated with water. This is especially true for clay-rich soil or soil that has been compacted. When this happens, any additional water cannot be absorbed by the soil, and it flows into the watercourse.

A watercourse with a shoreline that is rocky or close to a parking lot (where the water-absorbing soil has been replaced by asphalt) is more prone to flooding than, for example, one with a forested shoreline capable of absorbing water.

Floods can occur in a fairly predictable pattern. A historic example is the Nile River, which, before the construction of dams to control water flow, tended to flood with the increase of rain in the spring. This type of flooding tends to be less destructive because those living near the river anticipate it. In addition, the nutrients that are washed onto the land by the flood are left when the flood waters recede, making the land very fertile for growing crops.

Floods that occur with no warning are known as flash floods. These floods typically occur when a large amount of rain falls in a short time, such as in a monsoon. The sudden appearance of the excessive amount of water in a small watercourse can create a wall of water that rushes downstream. Just as quickly, the water level can return to normal. In July 2007, for example, a series of flash floods caused by heavy seasonal rains ravaged eight states in the African country of Sudan, killing more than 100 people

Undersea earthquakes release a great deal of energy, which pushes the surrounding ocean water outward from the origin of the earthquake. The result is a ripple effect, similar to the ripples created when a rock is dropped into a pond. The series of waves is called a tsunami. Moving at hundreds of miles per hour, the waves can devastate coastal regions. On December 26, 2004, a magnitude 9.0 earthquake off the coast of Sumatra spawned a series of waves that obliterated coastal villages in Sri Lanka, Thailand, Myanmar, India, and elsewhere. More than 155,000 people were killed inSri Lanka alone.

Impacts and Issues

The flash floods experienced in Sudan in the summer of 2007 affected 21 other African nations including Uganda, Ethiopia, Democratic Republic of the Congo, and Ghana, displacing more than 700,000 people and killing at least 300 people. At the same time, regions of the United Kingdom were affected by severe floods triggered by June rains of 5.5 in (14 cm), more than double the historic average for the month. Some regions of Britain experienced the most monthly rainfall ever recorded.

Hurricane Katrina was one of the 28 tropical and subtropical storms, and one of the 15 hurricanes, that

WORDS TO KNOW

CLIMATE MODEL: A quantitative method of simulating the interactions of the atmosphere, oceans, land surface, and ice. Models can range from relatively simple to quite comprehensive.

MONSOON: An annual shift in the direction of the prevailing wind that brings on a rainy season and affects large parts of Asia and Africa.

STORM SURGE: Rise of the sea at a coastline due to the effect of storm winds.

TSUNAMI: A series of ocean waves that result because of an undersea disturbance such as an earthquake.

occurred during the 2005 hurricane season. As of late 2007, the 2005 season stood as the most active Atlantic hurricane season ever recorded.

Extreme weather events such as these, with attendant flooding, are likely to be made more common by global climate change. Global climate change is the result of several centuries of human burning of fossil fuels and destruction of forests. These activities have added carbon dioxide (CO2) and other gases to Earth’s atmosphere in large quantities, causing it to retain more heat and warming the average global climate. This warming has had many effects on rainfall, snowfall, sea level, and other aspects of the environment. More drought and more flooding are both predicted results of global climate change, as rainfall in many areas becomes, on average, less frequent but more intense.

A pair of 2002 studies published in Nature highlighted the influence of climate on the occurrence of floods. The studies assessed data from all over the globe on the occurrence of 100-year-floods—those that are so severe that they are predicted to occur very rarely—and on 19 climate models. They revealed an increased frequency of major floods since the mid-twentieth century, and related the increase to global warming.

The World Water Council, a think-tank of water users and suppliers concerned with water-related social and economic issues, has predicted that by 2025 about half of Earth’s population will live in areas that will be at increased risk of severe storms and other extreme weather. One consequence could be increased frequency of floods.

Computer models have been used for decades to help understand weather patterns and predict the weather. Daily weather forecasts rely on computer projections along with the monitoring of data. Similarly, flood-modeling software exists. Information on the size, shape, and topography of the area that drains into the

particular watercourse; the types of soil present in the area; typical weather patterns; and land use are used to better understand how changing parameters affect the potential for flooding. Such models help scientists better understand how climate changes in the real world affect flooding.

See Also Climate Change; Drainage Basins; Global Warming; Hurricanes: Katrina Environmental Impacts; Rivers and Waterways; Runoff

BIBLIOGRAPHY

Books

DiMento, Joseph, and Pamela M. Doughman. Climate Change: What It Means for Us, Our Children, and Our Grandchildren. Boston: MIT Press, 2007.

Hulme, Mike. Nature’s Revenge?: Hurricanes, Floods and Climate Change. New York: Hodder, 2003.

Periodicals

Milly, P.C.D., R.T. Wetherald, K.A. Dunne, and T.L. Delworth. “Increasing Risk of Great Floods in a Changing Climate.” Nature 15 (2002): 514–517.

Palmer, T.N., and J. Räisanen. “Quantifying the Risk of Extreme Seasonal Precipitation Events in a Changing Climate.” Nature 415 (2002): 512-514.

Web Sites

Canadian Broadcasting Corporation. “In Depth: Forces of Nature—Flooding.” June 20, 2005. http://www.cbc.ca/news/background/forcesofnature/flooding.html (accessed March 24, 2008).

Environment Canada. “Causes of Flooding.” 2004. http://www.ec.gc.ca/water/en/manage/floodgen/e_cause.htm (accessed March 24, 2008).

United Nations University. “Two Billion People Vulnerable to Floods by 2050.” June 13, 2004. http://www.unu.edu/news/ehs/floods.doc (accessed March 24, 2008).

Brian D. Hoyle

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