• flood plain
    Flood plains usually only flood during the rainy season.

    Photograph by Chris Johns, National Geographic  

    The vast flood plains surrounding the Mississippi and Missouri rivers in the United States are among the most fertile agricultural land in the world. The use of dams, levees, and dikes usually allows people to control the flooding of the rivers.

    However, river management does not always work. Homes, farms, and other businesses in flood plains from Minnesota to Louisiana are threatened by the overflowing of the Mississippi and Missouri rivers.

    A flood plain is an area of land that is prone to flooding. People realize it is prone to flooding because it has flooded in the past due to a river or stream overflowing its banks.

    A flood plain usually is a flat area with areas of higher elevation on both sides. Flood plains can be very small or very large. Small flood plains sometimes are part of a valley. Houses that are built in small flood plains often require more insurance coverage because damage due to flooding is more likely to occur there than in higher elevations.

    Large flood plains can almost take up entire countries. In Vietnam's Mekong River delta, the flood plain of the Hau and Tien rivers covers more than 12,000 square kilometers (7,450 miles).

    Flood plains usually are very fertile agricultural areas. Floods carry sediment rich in nutrients. They spread that sediment to a wide area. Flood plains are flat and have relatively few rocks or other large obstacles that may prevent farming. The flood plains of the Nile River have been Egypt's center of agriculture for thousands of years.

    Floods are usually seasonal and can be predicted months ahead of time. The ability to develop agriculture, the transportation allowed by rivers, and the normally stable flood season make flood plains ideal locations to develop urban areas. The flood plains between the Tigris and Euphrates rivers are home to some of the world's earliest civilizations and first cities, including Ur.

  • Term Part of Speech Definition Encyclopedic Entry
    agriculture Noun

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

    Encyclopedic Entry: agriculture
    bank Noun

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

    city Noun

    large settlement with a high population density.

    civilization Noun

    complex way of life that developed as humans began to develop urban settlements.

    Encyclopedic Entry: civilization
    country Noun

    geographic territory with a distinct name, flag, population, boundaries, and government.

    dam Noun

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

    damage Noun

    harm that reduces usefulness or value.

    develop Verb

    to expand or grow.

    dike Noun

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

    Encyclopedic Entry: dike
    fertile Adjective

    able to produce crops or sustain agriculture.

    flood Verb

    to overflow or cover in water or another liquid.

    flood plain Noun

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

    Encyclopedic Entry: flood plain
    ideal Adjective


    insurance Noun

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

    levee Noun

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

    Encyclopedic Entry: levee
    nutrient Noun

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

    Encyclopedic Entry: nutrient
    obstacle Noun

    something that slows or stops progress.

    predict Verb

    to know the outcome of a situation in advance.

    prone Adjective

    vulnerable or tending to act in a certain way.

    river Noun

    large stream of flowing fresh water.

    Encyclopedic Entry: river
    river management Noun

    the art and science of controlling the flow, path, and power of rivers.

    rock Noun

    natural substance composed of solid mineral matter.

    seasonal Adjective

    likely to change with the seasons.

    sediment Noun

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

    Encyclopedic Entry: sediment
    stream Noun

    body of flowing fluid.

    transportation Noun

    movement of people or goods from one place to another.

    Ur Noun

    one of the earliest cities in the world, established as an urban center on the Euphrates River and the Persian Gulf as early as 3000 BCE.

    urban area Noun

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

    Encyclopedic Entry: urban area
    valley Noun

    depression in the Earth between hills.

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