The next time you are on a floodplain remember that unique alluvial soils that form there provide many beneficial values to society: agricultural production, pollutant trapping, and preserving evidence of our own human history.
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Notify me of new comments via email. Notify me of new posts via email. Skip to content Alluvial soils are soils deposited by surface water. In , a dam located in the Rocky Mountain National Park broke. The resulting million gallons of water deposited boulders, gravel and a mixture of sand, silt and clay in a fan shape. Fertile alluvial soil in central Pennsylvania tape in centimeters. This floodplain soil is formed from erosion of prime farmland in the watershed, which transfers nutrients to the floodplain.
The loamy upper material effectively holds water in the plant root zone and the rounded gravelly base below 90 cm allows for drainage of excess water from the root zone. Photo by M. Ricker Sometimes moving eroded soil and nutrients from one area to another can be good. When it overflows its banks, it deposits the eroded material and causes flood plains to be formed.
The deposited material makes the land fertile. Plainsare formed by the alluvial deposits of the river which increases the fertility of the soil. Rivers carry along with them eroded material like fine soil and sediments. Why are the alluvial plains a good place for agriculture?
Plains in many areas are important for agriculture because where the soils were deposited as sediments they may be deep and fertile, and the flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for livestock. What is Alluvia? Plural alluviums alluvia Sand, silt, clay, gravel, or other matter deposited by flowing water, as in a riverbed, floodplain, delta, or alluvial fan. Alluvium is generally considered a young deposit in terms of geologic time.
What is delta plain? A delta plain is a low-elevation floodplain formed at the mouth of a river. A delta plain is one type of low-lying coastal plain, formed where a river empties into the sea or, rarely, into a freshwater body, as in the case of the Selenga Delta, Figure 1a. What does alluvial? In the Arctic , where the ground is frozen, plains are called tundra.
Despite the cold, many plants survive here, including shrubs and moss. Plain Formation Plains form in many different ways. Some plains form as ice and water erodes, or wears away, the dirt and rock on higher land. Water and ice carry the bits of dirt, rock, and other material, called sediment , down hillsides to be deposited elsewhere. As layer upon layer of this sediment is laid down, plains form. Volcanic activity can also form plains. Lava plains form when lava pushes up from below ground and flows across the land.
The earth in a lava plain is often much darker than the surrounding soil. The dark earth is a result of the lava, mostly a dark-colored mineral called basalt , broken down into tiny particles over millions of years. The movement of rivers sometimes forms plains. Many rivers run through valleys. As rivers move from side to side, they gradually erode the valley , creating broad plains.
As a river floods, it overflows its bank. The flood carries mud , sand , and other sediment out over the land. After the water withdraws, the sediment remains. If a river floods repeatedly, over time this sediment will build up into a flood plain. Flood plains are often rich in nutrients and create fertile farmland. Alluvial plains form at the base of mountains.
Water carrying sediment flows downhill until it hits flat land. There, it spreads out, depositing the sediment in the shape of a fan. The Huang He River in China has created an alluvial plain that covers about , square kilometers , square miles. Because much of the sediment the Huang He carries is yellowish in color, it is also called the Yellow River.
Many rivers deposit their sediment in the ocean. As the sediment builds up, it might eventually rise above sea level , forming a coastal plain. These broad underwater plains slope gently down beneath the water. Abyssal plains are found at the bottom of the ocean. The rest have been converted into farmland. Image of the Day Land.
Flooding in early affected communities along the length of the Mississippi River; here is the view near Arkansas City. Persistent rains and saturated soils across the watershed swelled the river to its banks and occasionally onto floodplains. Persistent heavy rains in the first two months of have swelled rivers from Missouri to the Gulf of Mexico.
EO Explorer.
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