• flood
    Another word for flood is deluge (pronounced day-LOOJ or DEH-looj).

    Photograph by Didarul Alam Chy, MyShot

    Flood Myths
    Stories about great, Earth-drowning floods are common throughout world cultures. Many stories are remarkably similar: A deity warns a virtuous man about a catastrophic flood. The man builds a large boat, saving himself, his family, animals, and plants from the flood, which destroys the rest of the Earth. Eventually, the man releases two birds to see if they bring back vegetation (which can only grow in soil). A bird returns, and human civilization is saved.

    The most famous version of this flood myth is probably the story of Noah, recorded in the Torah, the Bible, and the Quran. Another version is the Mesopotamian legend of Utnapishtim, recorded in the Legend of Gilgamesh, one of the earliest works of literature, predating the Torah by more than a thousand years. The Maasai legend of Tumbainot, the Altai myth of Nama, and the Hawaiian myth of Nuu are all remarkably similar.

    "The Hero of Haarlem"
    A popular story concerns a young boy from the town of Haarlem, Netherlands, who notices a leak in the town's dike. The Spaarne River is flowing through a tiny hole in the barrier, threatening to flood the town. The young boy plugs the leak with his finger, and stays there all night. Adults find him the next morning and permanently repair the leak. Although first written about by an American (Mary Mapes Dodge, in her book Hans Brinker, or the Silver Skates), the story is from the Netherlands.

    The story has been changed and retold many times. In most versions, the dike is holding back the North Sea, not a river. In some versions of the story, the young boy freezes to death during his all-night stay at the dike.

    Flood as a War Tactic
    In 1937, the Chinese government destroyed the dike at Huayuankou, on the Yellow River, to stop the Japanese invasion. The invasion continued by a different route, but the environmental devastation of the flooding was immense. At least 800,000 people drowned, and more than a million were made homeless. More than a thousand square kilometers of farmland was underwater. Flooding changed the course of the Yellow River to such an extent that its mouth moved dozens of kilometers to the south. Ten years later, the dike at Huayuankou was rebuilt and the Yellow River resumed its previous course.

    Costliest U.S. Floods
    As of July 2011, according to the Federal Emergency Management Association (FEMA):
    Hurricane Katrina (2005)
    $16.2 billion
    Hurricane Ike (2008)
    $2.6 billion
    Hurricane Ivan (2004)
    $1.2 billion
    Tropical Storm Allison (1989)
    $1.1 billion
    Louisiana Flood (1995)
    $585 million

    Toxic Flood
    There are many examples of toxic materials, from pig manure to coal slurry, flooding communities. One of the most unusual was the 2010 rupture of a chemical storage tank at an aluminum factory in Ajka, Hungary. The bright-red sludge was responsible for at least four deaths, as well as the relocation of hundreds of Hungarians. The toxic sludge, which included lead and arsenic, was eventually diluted by the Danube River.

    A flood happens when water overflows or soaks land that is normally dry. There are few places on Earth where people don’t need to be concerned about flooding. Generally, floods take hours or even days to develop, giving residents time to prepare or evacuate. Sometimes, floods develop quickly and with little warning.

    A flood can develop in a many ways. The most common is when rivers or streams overflow their banks. These floods are called riverine floods. Heavy rain, a broken dam or levee, rapid icemelt in the mountains, or even a beaver dam in a vulnerable spot can overwhelm a river and send it spreading over nearby land. The land surrounding a river is called a flood plain.

    Coastal flooding, also called estuarine flooding, happens when a large storm or tsunami causes the sea to rush inland.

    Floods are the second-most widespread natural disaster on Earth, after wildfires. All 50 of the United States are vulnerable to flooding.

    Effects of Floods

    When floodwaters recede, affected areas are often blanketed in silt and mud. This sediment can be full of nutrients, benefiting farmers and agribusinesses in the area. Famously fertile flood plains like the Mississippi River valley in the American Midwest, the Nile River valley in Egypt, and the Fertile Crescent in the Middle East have supported agriculture for thousands of years. Yearly flooding has left millions of tons of nutrient-rich soil behind.

    However, floods have enormous destructive power. When a river overflows its banks or the sea moves inland, many structures are unable to withstand the force of the water. Bridges, houses, trees, and cars can be picked up and carried off. Floods erode soil, taking it from under a building's foundation, causing the building to crack and tumble. Severe flooding in Bangladesh in July 2007 led to more than a million homes being damaged or destroyed.

    Floods can cause even more damage when their waters recede. The water and landscape can be contaminated with hazardous materials, such as sharp debris, pesticides, fuel, and untreated sewage. Potentially dangerous mold can quickly overwhelm water-soaked structures.

    As flood water spreads, it carries disease. Flood victims can be left for weeks without clean water for drinking or hygiene. This can lead to outbreaks of deadly diseases like typhoid, malaria, hepatitis A, and cholera. This happened in 2000, as hundreds of people in Mozambique fled to refugee camps after the Limpopo River flooded their homes. They soon fell ill and died from cholera, which is spread by unsanitary conditions, and malaria, spread by mosquitoes that thrived on the swollen river banks.

    In the United States, floods are responsible for an average of nearly 100 deaths every year, and cause about $7.5 billion in damage.

    China's Yellow River valley has seen some of the world's worst floods in the past 100 years. The 1931 Yellow River flood is one of the most devastating natural disasters ever recorded—almost a million people drowned, and even more were left homeless.

    Natural Causes of Floods

    Floods occur naturally. They are part of the water cycle, and the environment is adapted to flooding. Wetlands along river banks, lakes, and estuaries absorb flood waters. Wetland vegetation, such as trees, grasses, and sedges, slow the speed of flood waters and more evenly distribute their energy. According to the U.S. Environmental Protection Agency (EPA), the wetlands along the Mississippi River once stored at least 60 days of flood water. (Today, Mississippi wetlands store only 12 days of flood water. Most wetlands have been filled or drained.)

    Floods can also devastate an environment. The most vulnerable regions are those that experience frequent floods and those that have not flooded for many years. In the first case, the environment does not have time to recover between floods. In the second case, the environment may not be able to adapt to flood conditions.

    In August 2010, Pakistan experienced some of the worst floods of the century. The annual monsoon, on which Pakistani farmers and consumers rely, was unusually strong. Tons of water drenched the nation. The Indus River burst its banks. Because the river flows almost directly through the narrow country, almost all of Pakistan was affected by flooding.

    Millions of Pakistanis lost their homes, and almost 2,000 died in the floods. The province of Punjab, the country’s agricultural center, was particularly devastated. Rice, wheat, and corn crops were destroyed. The impact of the floods continued long after the monsoon dwindled and the Indus subsided. Pakistanis experienced food shortages, power outages, and loss of infrastructure. Outbreaks of cholera and malaria developed near resettlement camps. Experts estimated that the rebuilding effort would cost up to $15 billion.

    Sometimes, floods are triggered by other natural disasters, such as earthquakes and tsunamis. In January 2011, a major earthquake struck off the coast of Miyagi Prefecture, Japan. The quake triggered a massive tsunami, its crest reaching as high as 40 meters (131 feet). The tsunami crashed more than 10 kilometers (6 miles) inland, flooding homes, businesses, schools, parks, hospitals, and the Fukushima Dai-ichi Nuclear Power Plant. A dam holding a reservoir burst, triggering another flood that destroyed homes.

    Rain that accompanies hurricanes and cyclones can quickly flood coastal areas. The rise in sea level that occurs during these storms is called a storm surge. A storm surge is a type of coastal flood. They can be devastating. The storm surge that accompanied the 1970 Bhola cyclone flooded the low-lying islands of the Ganges Delta in India and Bangladesh. More than 500,000 people were killed, and twice that number were left homeless.

    The strong winds associated with hurricanes and cyclones can also whip up and move huge amounts of water, forcing a storm surge far inland. In 2005, Hurricane Katrina brought huge amounts of wind and rain to the Gulf Coast of the United States. The city of New Orleans, Louisiana, was particularly hard-hit. The storm surge from Hurricane Katrina caused some of the city’s levees to break. Levees protect New Orleans from the Mississippi River. The river rushed in and flooded entire neighborhoods. Hundreds of people drowned, and the storm did more than $100 billion in damage.

    Man-Made Causes of Floods

    Floods can also have man-made sources. Many man-made floods are intentional and controlled.

    Rice farmers, for instance, rely on flooded fields. Rice is a semi-aquatic crop—it grows in water. After rice seedlings are planted, farmers flood their fields, called rice paddies, in about 15 to 25 centimeters (6 to 10 inches) of water. Rice paddies must be carefully engineered to allow controlled flooding. Strong dikes or levees, as well as regulated channels for irrigation, are required.

    Sometimes, engineers flood an area to restore an ecosystem. In 2008, the Grand Canyon was deliberately flooded. Water was released from dams on the Colorado River, which runs through the Grand Canyon. In 20 minutes, enough water was released from a dam at Lake Powell, Utah, to fill up the Empire State Building. Hydrologists, engineers, and environmentalists hoped that flooding the canyon would help redistribute sediment—which had been blocked up by dams—and create sandbars. Sandbars provide a wildlife habitat, often serving as a shallow bridge for animals such as beavers and bighorn sheep to cross from one side of the river to the other.

    Dams control the natural flood plains of lakes and rivers. Hydrologists may intentionally flood areas to prevent damage to the dam or increase the water supply for agriculture, industry, or consumer use.

    Engineers may also intentionally flood areas to prevent the possibility of worse flooding. When heavy rains caused the Souris River to flood in 2011, for example, the water level nearly reached the top of the Alameda Reservoir in Oxbow, Saskatchewan, Canada. Faced with the prospect of catastrophic flooding if the entire dam broke, engineers chose to release huge amounts of water. The reservoir remained intact, but the release contributed to massive floods in both Saskatchewan and the U.S. city of Minot, North Dakota.

    Not all man-made floods are intentional, however. The natural banks of rivers and streams shrink as people develop land nearby. River banks are valuable real estate for housing, businesses, and industry. From Shanghai, China, to San Antonio, Texas, rivers are the sites of busy urban areas. In rural areas, factories use river currents to distribute runoff. To accommodate such development, river banks are paved with hard, non-porous materials. Soils and plants are replaced with concrete and asphalt, which can’t absorb water. An unusual amount of rain can cause these rivers to quickly overrun their concrete banks.

    Australia is conducting an investigation of Brisbane’s development decisions after the Brisbane River overran its banks and flooded the country’s capital in 2011. Streets, downtown business districts, and bridges were destroyed. Water reached the third row of seats in the city’s rugby stadium. The flood waters were high enough (2 meters/6 feet) that bull sharks were spotted swimming up major streets.

    Concrete banks also increase the amount of runoff flowing to nearby bodies of water. This increases the risk of coastal flooding. Venice, Italy, for instance, is frequently flooded as tides from the Adriatic Sea seep into the heavily developed islands on which the city rests.

    Hydrologists, engineers, and city planners constantly work to reduce flood damage. Shrubs and plants create buffers to prevent runoff from seeping into flood plains, urban areas, or other bodies of water. The thick vegetation between a river and a flood plain is called a riparian zone.

    Despite their efforts, people can also radically fail to control floods. The most famous flood in American history, the Johnstown Flood, was a man-made disaster. The tragedy killed 2,209 people and made headlines around the country.

    Johnstown, Pennsylvania, was on a flood plain at the meeting of the Stony Creek and Little Conemaugh rivers. As more people moved to the city, the banks of the rivers were paved and narrowed, causing yearly flooding. Residents were prepared for this. They watched the river and moved their belongings upstairs or onto rooftops as the city flooded.

    However, residents were not prepared for the additional flood from an entire lake. Located in nearby mountains, Lake Conemaugh was a reservoir created by the South Fork Dam. The lake was an exclusive retreat for members of the South Fork Fishing and Hunting Club, which owned the dam. Lake Conemaugh contained 20 million tons of water.

    On May 31, 1889, the dam broke and the water rushed down the river at 64 kilometers per hour (40 miles per hour). Johnstown’s leading industry was steel production, and the flood waters quickly became choked with industrial debris—steel cables, chemical solvents, glass, rail cars. The flood destroyed a wire factory, filling the water with tons of barbed wire. About 80 people died when floating wreckage caught fire.

    Rebuilding Johnstown took years—the bodies of some victims were not found until 20 years later. Although the South Fork Fishing and Hunting Club failed to maintain the dam, members of the club successfully argued that the disaster was an “act of God.”

    Flood Classification

    Disaster experts classify floods according to their likelihood of occurring in a given time period. The most common classifications are a 10-year flood, a 50-year flood, and a 100-year flood. A 100-year flood, for example, is an extremely large, destructive event that would be expected to happen only once every century.

    But this is only an estimate. What “100-year flood” actually means is that there is a 1 percent chance that such a flood could happen in any given year. In recent decades, 100-year floods have occurred more frequently. This may be due to global warming, the current period of climate change.

    The Red River, which flows along the border of North Dakota and Minnesota, chronically floods. Anything over 8.5 meters (28 feet) is considered “flood stage” in the area. In 1997, the river crested at almost 12 meters (40 feet), a record level. In 2009, the record was beaten as the river flooded again, reaching a height of almost 12.5 meters (40.8 feet). The river flooded for 61 days.

    Flash floods can develop within hours of heavy rainfall. Flash floods can be extremely dangerous, instantly turning a babbling brook into a thundering wall of water that sweeps away everything in its path. Most deaths from flooding occur as a result of flash floods. Flash floods do not have a system for classifying their magnitude.

    Deserts are vulnerable to flash floods. Wadis and arroyos are dry river beds that only flow during heavy rains. Wadis can be dangerous during flash floods because they rarely have riparian zones to slow the flood’s energy. The city of Jeddah, Saudi Arabia, developed on the site of several wadis, and floods are frequent after heavy rains. More than 100 people died in flash floods in Jeddah in 2009. The floods developed so quickly that many victims drowned in their cars as streets became submerged.

    Predicting Floods

    Today, hydrologists study past flood patterns to help predict where and when floods will happen in the future. The predictions are only estimates, however. Weather, land, and climate can all change.

    An area’s soil and groundwater provide clues about flooding. Pedologists, or soil scientists, work with hydrologists to determine how much water a region’s earth can absorb. Agricultural soil, for instance, can absorb much more water than sand or bare rock. Groundwater is water already in the earth—in soil, underground reservoirs called aquifers, and even porous rocks. The type of soil and the amount of groundwater tells hydrologists how much more water the earth can absorb.

    Determining the amount of runoff in an area can also provide clues about the possibility of flooding. Runoff happens when there is more water than soil can absorb. Excess water overflows and runs on top of the land. Runoff can come from natural processes, such as icemelt. It can also come from human activity, such as excess irrigation, sewage, and industrial waste. Controlling runoff can help control floods.

    Hydrologists work with meteorologists to evaluate snowfall and snowpack. Melting snow contributes to runoff and increases groundwater levels. When snow melts quickly, the ground may not have time to absorb the water. Snowfall is one of the biggest contributors to flooding, and cannot always be predicted. Rapid snowmelt in the Andes Mountains, for example, creates mudslides and floods that disable railways and bridges. In 2010, snowmelt flooding trapped 4,000 tourists in towns near the remote historic site of Machu Picchu, Peru, for two days.

    Modern technology helps researchers predict floods. Doppler radar, for example, shows scientists where a storm is most severe. Doppler uses motion to detect weather patterns and create computerized images of rainfall. Automated gauges placed in rivers measure the height and speed of river currents, and the amount of rain received. Geographic information system (GIS) maps made with this information help scientists warn people if a river will overrun its banks and flood areas nearby.

    Preventing Floods

    For thousands of years, people have tried to prevent and control floods. Yu the Great, for example, is a legendary figure in Chinese history. Around 2100 BCE, Yu developed a way to control the devastating floods of the Yellow River. Yu studied data from previous Yellow River floods, noting where the flow was the strongest and flood plains were most vulnerable. Instead of damming the river, Yu dredged it—he and a team of engineers made river channels deeper to accommodate more water. Yu also oversaw the construction of numerous irrigation canals, which diverted the flow of the river’s mainstem during times of flooding.

    It’s not always possible to prevent floods, but it is often possible to minimize flood damage. Structures around rivers, lakes, and the sea can contain flood waters. Levees, runoff canals, and reservoirs can stop water from overflowing.

    Levees are usually made of earth. They are built by piling soil, sand, or rocks near a river’s banks. Levees may also be made of blocks of wood, plastic, or metal. They may even be reinforced by concrete. Levees in New Orleans, for example, use compacted earth, wooden beams, iron rebar, steel pilings, and concrete to hold back the mighty Mississippi River.

    Runoff canals are man-made channels. These structures are connected to rivers and direct excess water away from buildings and residences. One of the first canals in North America was constructed in about 200 BCE to control the seasonal flood waters of Lake Okeechobee, Florida. Today, southern Florida is criss-crossed by runoff canals that redirect the flow of the Everglades, the “River of Grass” that runs from Lake Okeechobee to the Atlantic Ocean and Gulf of Mexico. These canals redirect flood water away from urban areas in southern Florida and toward irrigation canals primarily used for fields of sugar cane.

    Natural and man-made reservoirs help prevent flooding. Natural reservoirs are basins where freshwater collects. Man-made reservoirs collect water behind a dam. They can hold more water in times of heavy rainfall. In April 2011, the government of Ethiopia announced plans for a large dam on the Blue Nile River. The Grand Ethiopian Renaissance Dam, which would be the largest dam in Africa, would create a reservoir capable of holding 67 billion cubic meters (2.4 trillion cubic feet) of water. The dam would prevent flooding downstream and provide the nation with hydroelectric energy.

    Conserving wetlands also reduces the impact of floods. Wetlands provide a natural barrier, acting as a giant sponge for storm surges and flood plains. The swamps and bayous of southern Louisiana and Mississippi, for instance, protect inland areas from both coastal and riverine flooding. Wetlands absorb the storm surge from hurricanes that hit the area from the Gulf of Mexico. Wetland riparian zones that line the Mississippi River protect fertile flood plains as the river overflows its banks.

    Many governments mandate that residents of flood-prone areas purchase flood insurance and build flood-resistant structures. Massive efforts to mitigate and redirect floods have resulted in some of the most ambitious engineering efforts ever seen. The Thames Barrier is one of the largest flood-control projects in the world. The Thames Barrier protects the urban area of London, England, from floods from storm surges that rush up the River Thames from the Atlantic Ocean. A series of 10 steel gates span the river near London’s Woolrich district. Each gate can hold back 9,000 tons of water, and disappears into the river when the water is calm.

    Perhaps the most extensive and sophisticated flood-prevention program is the Zuiderzee Works in the Netherlands. The Netherlands is a low-lying nation that is plagued by coastal flooding from the North Sea. Beginning in the 1200s, the Dutch began to erect a series of massive dikes and levees on its coast. In the 1900s, Dutch engineers worked to isolate and dam an entire inlet of the North Sea, the Zuiderzee. The largest part of the Zuiderzee Works is the Afsluitdijk, a 32-kilometer (20-mile) dike that cuts off the Zuiderzee from the North Sea. In addition to protecting the Netherlands from flooding, the Zuiderzee Works has drained parts of the Zuiderzee for development.

  • Term Part of Speech Definition Encyclopedic Entry
    100-year flood Noun

    flood that has a one-percent chance of occurring any year.

    absorb Verb

    to soak up.

    accommodate Verb

    to provide or satisfy.

    act of God Noun

    legal term for a catastrophic event that cannot be foreseen or controlled.

    adapt Verb

    to adjust to new surroundings or a new situation.

    Afsluitdijk Noun

    (32 kilometers/20 miles long, 7 meters/23 feet above sea level) dike in the Netherlands that partly dams the North Sea.

    agribusiness Noun

    the strategy of applying profit-making practices to the operation of farms and ranches.

    agriculture Noun

    the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

    Encyclopedic Entry: agriculture
    ambitious Adjective

    eager to achieve wealth, power, status, or a specific goal.

    aquifer Noun

    an underground layer of rock or earth which holds groundwater.

    Encyclopedic Entry: aquifer
    archaeological site Noun

    place where evidence of the past is being studied by scientists.

    arroyo Noun

    deep channel or canyon, often dry except during flash floods. Also called a wadi.

    asphalt Noun

    chemical compound made of dark, solid rocks and minerals often used in paving roads.

    bank Noun

    a slope of land adjoining a body of water, or a large elevated area of the sea floor.

    barbed wire Noun

    twisted metal with sharpened points, often used for fences.

    bayou Noun

    swampy backwater of a river or lake.

    Encyclopedic Entry: bayou
    benefit Verb

    to be helpful or useful.

    Bhola cyclone Noun

    (1970) storm that caused widespread damage and death in Bangladesh and India.

    brook Noun

    small flow of water, larger than a rill but smaller than a river.

    buffer Noun

    a cushion or shield.

    bull shark Noun

    shark able to survive in freshwater habitats.

    cable Noun

    strong set of cords or wire ropes.

    canal Noun

    artificial waterway.

    catastrophic Adjective

    very bad.

    century Noun

    100 years.

    channel Noun

    waterway between two relatively close land masses.

    Encyclopedic Entry: channel
    cholera Noun

    infectious, sometimes fatal disease that harms the intestines.

    chronic Adjective

    recurring or happening frequently.

    city Noun

    large settlement with a high population density.

    city planner Noun

    person who plans the physical design and zoning of an urban center.

    climate Noun

    all weather conditions for a given location over a period of time.

    Encyclopedic Entry: climate
    climate change Noun

    gradual changes in all the interconnected weather elements on our planet.

    Encyclopedic Entry: climate change
    coastal flooding Noun

    process where a storm or tsunami causes the sea to rush inland, as a storm surge. Also called estuarine flooding.

    Colorado River Noun

    (2,335 kilometers/1,450 miles) river in the western U.S. and Mexico, draining into the Gulf of California.

    concern Verb

    to worry or take an interest in.

    concrete Noun

    hard building material made from mixing cement with rock and water.

    consumer Noun

    person who uses a good or service.

    contaminate Verb

    to poison or make hazardous.

    crest Noun

    the top of a wave.

    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    current Noun

    steady, predictable flow of fluid within a larger body of that fluid.

    Encyclopedic Entry: current
    cyclone Noun

    weather system that rotates around a center of low pressure and includes thunderstorms and rain. Usually, hurricanes refer to cyclones that form over the Atlantic Ocean.

    dam Noun

    structure built across a river or other waterway to control the flow of water.

    debris Noun

    remains of something broken or destroyed; waste, or garbage.

    deliberately Adverb

    on purpose.

    desert Noun

    area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.

    Encyclopedic Entry: desert
    destructive Adjective

    harmful.

    devastate Verb

    to destroy.

    development Noun

    construction or preparation of land for housing, industry, or agriculture.

    dike Noun

    a barrier, usually a natural or artificial wall used to regulate water levels.

    Encyclopedic Entry: dike
    disable Verb

    to weaken or make useless.

    disease Noun

    a harmful condition of a body part or organ.

    dispose Verb

    to throw away or get rid of.

    distribute Verb

    to divide and spread out materials.

    divert Verb

    to direct away from a familiar path.

    domestic animal Noun

    animal that has been tamed for work or to be a pet.

    domesticate Verb

    to tame or adapt for human use.

    Doppler radar Noun

    weather tracking system that reads the direction and speed of moving objects, such as drops of precipitation.

    downstream Noun

    in the direction of a flow, toward its end.

    dredge Verb

    to remove sand, silt, or other material from the bottom of a body of water.

    drench Verb

    to soak or cover with water.

    drywall adjective, noun

    wide, flat board, usually made of plaster or wood pulp, that is often used to construct the interior walls of buildings.

    dwindle Verb

    to shrink.

    earth Noun

    soil or dirt.

    earthquake Noun

    the sudden shaking of Earth's crust caused by the release of energy along fault lines or from volcanic activity.

    economy Noun

    system of production, distribution, and consumption of goods and services.

    ecosystem Noun

    community and interactions of living and nonliving things in an area.

    Encyclopedic Entry: ecosystem
    elaborate Adjective

    complex and detailed.

    elevation Noun

    height above or below sea level.

    Encyclopedic Entry: elevation
    engineer Noun

    person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).

    enormous Adjective

    very large.

    environment Noun

    conditions that surround and influence an organism or community.

    environmentalist Noun

    person who studies or works to protect the Earth's ecosystems.

    Environmental Protection Agency (EPA) Noun

    U.S. government organization whose mission is to "protect human health and the environment."

    erect Verb

    to build or raise.

    erode Verb

    to wear away.

    erosion Noun

    act in which earth is worn away, often by water, wind, or ice.

    Encyclopedic Entry: erosion
    estimate Verb

    to guess based on knowledge of the situation or object.

    estuarine flooding Noun

    process where a storm or tsunami causes the sea to rush inland, as a storm surge. Also called coastal flooding.

    evacuate Verb

    to leave or remove from a dangerous place.

    evaluate Verb

    to decide something's worth.

    Everglades Noun

    vast swampy region flowing south of Lake Okeechobee in Florida.

    excess Noun

    extra or surplus.

    exclusive Adjective

    limited to a few characteristics.

    extensive Adjective

    very large.

    farmer Noun

    person who cultivates land and raises crops.

    fertile Adjective

    able to produce crops or sustain agriculture.

    Fertile Crescent Noun

    region extending from the eastern Mediterranean coast through Southwest Asia to the Persian Gulf.

    flash flood Noun

    sudden, short, and heavy flow of water.

    flood Noun

    overflow of a body of water onto land.

    Encyclopedic Entry: flood
    flood plain Noun

    flat area alongside a stream or river that is subject to flooding.

    Encyclopedic Entry: flood plain
    flood stage Noun

    level at which a river, creek, or other body of water may cause damage to lives, property, or businesses.

    food web Noun

    all related food chains in an ecosystem. Also called a food cycle.

    Encyclopedic Entry: food web
    foundation Noun

    structure on which a building is constructed.

    frequent Adjective

    often.

    freshwater Noun

    water that is not salty.

    fuel Noun

    material that provides power or energy.

    gauge Noun

    measuring device, usually mechanical.

    geographic information system (GIS) Noun

    any system for capturing, storing, checking, and displaying data related to positions on the Earth's surface.

    Encyclopedic Entry: GIS (geographic information system)
    global warming Noun

    increase in the average temperature of the Earth's air and oceans.

    Encyclopedic Entry: global warming
    government Noun

    system or order of a nation, state, or other political unit.

    groundwater Noun

    water found in an aquifer.

    Encyclopedic Entry: groundwater
    habitat Noun

    environment where an organism lives throughout the year or for shorter periods of time.

    Encyclopedic Entry: habitat
    harbor Noun

    part of a body of water deep enough for ships to dock.

    Encyclopedic Entry: harbor
    harvest Noun

    the gathering and collection of crops, including both plants and animals.

    hazard Noun

    danger or risk.

    hepatitis Noun

    disease of the liver.

    herd Noun

    group of animals.

    hurricane Noun

    tropical storm with wind speeds of at least 119 kilometers (74 miles) per hour. Hurricanes are the same thing as typhoons, but usually located in the Atlantic Ocean region.

    Hurricane Katrina Noun

    2005 storm that was one of the deadliest in U.S. history.

    hydroelectric energy Noun

    energy generated by moving water converted to electricity. Also known as hydroelectricity.

    Encyclopedic Entry: hydroelectric energy
    hydrologist Noun

    person who studies the distribution, circulation, and properties of water.

    hygiene Noun

    science and methods of keeping clean and healthy.

    icemelt Noun

    flowing water created by melting ice.

    industry Noun

    activity that produces goods and services.

    infrastructure Noun

    structures and facilities necessary for the functioning of a society, such as roads.

    inland Adjective

    area not near the ocean.

    inlet Noun

    small indentation in a shoreline.

    insurance Noun

    money paid in good health to guarantee financial or physical health if injury or damage occurs.

    intact Adjective

    whole or complete.

    international Adjective

    having to do with more than one country.

    irrigation Noun

    watering land, usually for agriculture, by artificial means.

    Encyclopedic Entry: irrigation
    irrigation canal Noun

    channel dug between a source of water and crops. Also called an irrigation ditch.

    island Noun

    body of land surrounded by water.

    Encyclopedic Entry: island
    isolate Verb

    to set one thing or organism apart from others.

    Johnstown Flood Noun

    (1889, Johnstown, Pennsylvania) disaster caused by the failure of a dam, resulting in more than 2,200 deaths.

    lake Noun

    body of water surrounded by land.

    landscape Noun

    the geographic features of a region.

    Encyclopedic Entry: landscape
    levee Noun

    bank of a river, raised either naturally or constructed by people.

    Encyclopedic Entry: levee
    magnitude Noun

    intensity of an earthquake, represented by numbers on a scale.

    mainstem Noun

    largest river or channel in a watershed or drainage basin.

    malaria Noun

    infectious disease caused by a parasite carried by mosquitoes.

    massive Adjective

    very large or heavy.

    meteorologist Noun

    person who studies patterns and changes in Earth's atmosphere.

    migrate Verb

    to move from one place or activity to another.

    minimize Verb

    to make smaller.

    Mississippi River Noun

    (3,734 kilometers/2,320 miles) river in the central United States.

    mold Noun

    type of fungi that forms on the surface of materials.

    monsoon Noun

    seasonal change in the direction of the prevailing winds of a region. Monsoon usually refers to the winds of the Indian Ocean and South Asia, which often bring heavy rains.

    Encyclopedic Entry: monsoon
    mosquito Noun

    insect capable of piercing the skin and sucking the blood of animals.

    mudslide Noun

    rapid, downhill flow of soil and water. Also called a mudflow.

    natural disaster Noun

    an event occurring naturally that has large-scale effects on the environment and people, such as a volcano, earthquake, or hurricane.

    neighborhood Noun

    an area within a larger city or town where people live and interact with one another.

    Encyclopedic Entry: neighborhood
    non-porous Adjective

    not permeable by a substance such as air or water.

    nonprofit organization Noun

    business that uses surplus funds to pursue its goals, not to make money.

    nutrient Noun

    substance an organism needs for energy, growth, and life.

    Encyclopedic Entry: nutrient
    outbreak Noun

    sudden occurrence or rapid increase.

    overwhelm Verb

    to completely overpower.

    particularly Adverb

    specifically.

    pedologist Noun

    person who studies soil.

    pesticide Noun

    natural or manufactured substance used to kill organisms that threaten agriculture or are undesirable. Pesticides can be fungicides (which kill harmful fungi), insecticides (which kill harmful insects), herbicides (which kill harmful plants), or rodenticides (which kill harmful rodents.)

    piling Noun

    structure, usually made of metal or wood, hammered vertically into the ground to serve as a foundation or wall.

    plague Verb

    to consistently bother, torment, or annoy.

    power plant Noun

    industrial facility for the generation of electric energy.

    predict Verb

    to know the outcome of a situation in advance.

    primarily Adverb

    first or most important.

    prone Adjective

    vulnerable or tending to act in a certain way.

    province Noun

    division of a country larger than a town or county.

    Encyclopedic Entry: province
    radically Adverb

    completely or extremely.

    railway Noun

    stretch of railroad between two points.

    rain Noun

    liquid precipitation.

    Encyclopedic Entry: rain
    rapid Adjective

    very fast.

    real estate Noun

    property and the business of buying, selling, and developing land.

    rebar Noun

    metal bar, usually steel or concrete, used to reinforce concrete structures.

    recede Verb

    to retreat or withdraw.

    redistribute Verb

    to give away an amount of something in a different way.

    reduce Verb

    to lower or lessen.

    refugee camp Noun

    temporary shelters built for immigrants who have fled their homes due to environmental or social conflict.

    remote Adjective

    distant or far away.

    reservoir Noun

    natural or man-made lake.

    Encyclopedic Entry: reservoir
    retreat Verb

    to go back to a familiar or safe place.

    rice paddy Noun

    rice field.

    riparian zone Noun

    area surrounding a river, stream, or other body of flowing water.

    river Noun

    large stream of flowing fresh water.

    Encyclopedic Entry: river
    riverine flood Noun

    process where a river or stream overflows its banks.

    rock Noun

    natural substance composed of solid mineral matter.

    rugby Noun

    team sport similar to soccer, but where players are allowed to carry the ball, block with the hands and arms, and tackle.

    runoff Noun

    overflow of fluid from a farm or industrial factory.

    Encyclopedic Entry: runoff
    sand Noun

    small, loose grains of disintegrated rocks.

    sandbar Noun

    underwater or low-lying mound of sand formed by tides, waves, or currents.

    sedge Noun

    grass-like plant native to wetlands.

    sediment Noun

    solid material transported and deposited by water, ice, and wind.

    Encyclopedic Entry: sediment
    seedling Noun

    young tree or other plant.

    seep Verb

    to slowly flow through a border.

    semi-aquatic Adjective

    needing both a water and land environment to live and reproduce.

    severe Adjective

    harsh.

    sewage Noun

    liquid and solid waste material from homes and businesses.

    sewer Noun

    passageway or holding tank for liquid waste.

    shrub Noun

    type of plant, smaller than a tree but having woody branches.

    silt Noun

    small sediment particles.

    Encyclopedic Entry: silt
    snowfall Noun

    amount of snow at a specific place over a specific period of time.

    snowpack Noun

    layers of snow that naturally build up during snowfalls.

    soil Noun

    top layer of the Earth's surface where plants can grow.

    solvent Noun

    substance that dissolves another substance.

    sophisticated Adjective

    knowledgeable or complex.

    steel Noun

    metal made of the elements iron and carbon.

    storm Noun

    severe weather indicating a disturbed state of the atmosphere resulting from uplifted air.

    storm surge Noun

    abnormal rise in sea level accompanying a hurricane or other intense storm. Also called a storm tide.

    Encyclopedic Entry: storm surge
    stream Noun

    body of flowing fluid.

    submerge Verb

    to put underwater.

    subside Verb

    to return to a lower level.

    subway Noun

    underground railway; a popular form of public transportation in large urban areas.

    sugar cane Noun

    tall grass that is harvested to extract sugar from its sap or juice.

    swamp Noun

    land permanently saturated with water and sometimes covered with it.

    Encyclopedic Entry: swamp
    technology Noun

    the science of using tools and complex machines to make human life easier or more profitable.

    Thames Barrier Noun

    flood-control project that protects London, England, from flooding of the River Thames, made of 10 moveable steel gates.

    tourist Noun

    person who travels for pleasure.

    toxic Adjective

    poisonous.

    trigger Verb

    to cause or begin a chain of events.

    tsunami Noun

    ocean waves triggered by an earthquake, volcano, or other movement of the ocean floor.

    typhoid Noun

    infectious, sometimes fatal disease that harms the intestines. Also called typhoid fever.

    urban area Noun

    developed, densely populated area where most inhabitants have nonagricultural jobs.

    Encyclopedic Entry: urban area
    vegetation Noun

    all the plant life of a specific place.

    village Noun

    small human settlement usually found in a rural setting.

    Encyclopedic Entry: village
    vulnerable Adjective

    capable of being hurt.

    wadi Noun

    deep channel or canyon, often dry except during flash floods. Also called an arroyo.

    wading bird Noun

    bird with long, thin legs adapted for walking and feeding in shallow water.

    water cycle Noun

    movement of water between atmosphere, land, and ocean.

    Encyclopedic Entry: water cycle
    waterway Noun

    body of water that serves as a route for transportation.

    wave Noun

    vibrations (oscillations) around a fixed location, usually involving a transfer of energy from one point to another.

    weather Noun

    state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.

    Encyclopedic Entry: weather
    weathering Noun

    the breaking down or dissolving of the Earth's surface rocks and minerals.

    Encyclopedic Entry: weathering
    weather pattern Noun

    repeating or predictable changes in the Earth's atmosphere, such as winds, precipitation, and temperatures.

    wetland Noun

    area of land covered by shallow water or saturated by water.

    Encyclopedic Entry: wetland
    wildfire Noun

    uncontrolled fire that happens in a rural or sparsely populated area.

    Yu the Great Noun

    (220-2100 BCE) Chinese leader, engineer, and hydrologist.

    Zuiderzee Works Noun

    (Netherlands) series of dams and drainage systems designed to isolate and dam the Zuiderzee, an inlet of the North Sea.

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