What type of sediment covers a floodplain

Initially during a flood, as more water enters the river or stream, the height of the water rises. Once the volume of water exceeds what the river channel is capable of carrying, it spills out onto the floodplain and the rate at which the waters rise increases much more slowly because any additional volume of water spreads out into the much larger capacity provided by the floodplain.

Floodwaters move much more slowly on floodplains and so very extensive floodplains can act something like a reservoir that temporarily stores water, slowly releasing it back to the river as the flood recedes. Additionally, by slowing the speed of floodwaters, floodplains are also able to reduce the impact of erosion downstream.

The shape, size, and composition of any floodplain will determine how effective it is at storing and slowing floodwaters, and any encroachments that impact those factors may reduce the effectiveness of flood storage in an individual floodplain and may have cascading impacts downstream. The primary threat facing floodplains is development or encroachments into the natural floodplain.

In general floodplains are delineated and managed based on the volume of water or the size or likelihood of a storm that they can handle i. While efforts have been made to tailor floodplain management in such a way as to reduce the impacts of flooding on the built environment, far too often this designation does not take full account of the entirety of a natural floodplain, instead focusing only on areas where water moves rapidly during flooding events.

An extension of development within the floodplain is the desire to channelize or control how a river moves as a means of protecting built infrastructure within the floodplain. The proliferation of levies, berms, dams, and other means of restricting the natural movement of a river has dramatically changed the hydrology of many river systems and disconnected waterways from their natural floodplains, resulting in loss of habitat and the natural flood reduction benefits that those natural systems provide.

Most of this floodplain, approximately 25 million acres 10 million hectares , occurs adjacent to the lower Mississippi, which meanders in great loops. Natural levees, oxbow lakes, and marshes mark this area. The Mississippi River is one of the most heavily engineered natural features in the United States. The character of its floodplain has changed to accommodate agriculture and urban development. Ninety percent of the floodplain lies behind levees, many of which have been artificially created.

Twenty-eight locks and dams were constructed on the upper Mississippi River to allow the passage of ships. As a result, much of the river's floodplain fails to receive its revitalizing seasonal floods. Extensive water pollution has also affected the river and its floodplain. The Nile River is the longest river in the world. It runs approximately 4, miles 6, kilometers from the Luvironza River in Burundi in central Africa to the Mediterranean Sea on the northeast coast of Egypt.

Part of the upper Mississippi River cutting through sandstone. The river's floodplain encompasses more than 30 million acres and mostly occurs adjacent to the lower Mississippi. It flows toward the Mediterranean, draining about 1,, square miles 2,, square kilometers of land, which is about one-tenth of the area of the African continent.

In ancient times, the Nile River flooded annually, caused by rains in central Africa and melting snow and rains in the Ethiopian highlands. The river was at its lowest point in May, but from June to August it rose rapidly, carrying great quantities of silt in its waters that flowed out over the river's floodplain. The flood was at its highest point in mid-September. By October the waters began to recede, leaving pools of water in backswamps. After the water was absorbed by the soil, the ancient Egyptians planted their crops in the fertile floodplain.

In the Egyptian government completed construction of the Aswan High Dam on the Nile just south of the city of Aswan, ending the annual floods on the river.

The dam, which formed the artificial Lake Nasser behind it, helps provide hydroelectric power and water for irrigation projects. It has also prevented silt from being carried further downstream, trapping 98 percent of the river's rich sediments. Since then, farmers along the Nile have been forced to use large amounts of chemical fertilizers, which have washed into the river, contaminating it and other.

The Pantanal, which covers more than 77, square miles in Brazil, is considered one of Earth's richest ecosystems. It is a landscape of swamps, seasonally flooded grasslands and woodlands, and different types of forest. Because the river does not bring new sediment to areas downstream, soil erosion has become an additional problem.

The Pantanal pronounced pen-te—NAL; Portuguese for "swamp" is a land area covering approximately 77, square miles , square kilometers. Lying mostly in west-central Brazil, the Pantanal also reaches into eastern Bolivia and northeastern Paraguay.

During the wet season, from November to April, this vast floodplain of the Paraguay River and its tributaries becomes partially submerged.

Average annual rainfall in this area measures between 39 and 55 inches and centimeters. The slope of the land is very slight, and the rivers and streams cannot carry the excess amount of water. The floodplain is swamped by a flood that takes six months to travel the length of the Pantanal from north to south. Areas of the floodplain are alternately flooded, then left dry with only a few spots of water remaining.

The Pantanal is considered one of Earth's richest ecosystems an ecosystem is a system formed by the interaction of a community of plants, animals, and microorganisms with their environment. This mixture helps the Pantanal house the highest concentration of wildlife in both North and South America. Approximately species of birds inhabit the area. It is also one of the last refuges for many threatened South American mammals, including jaguars, pumas, manned wolves, giant otters, giant anteaters, giant armadillos, and marsh deer.

Bridge, John S. Malden, MA: Blackwell, Geological Survey. Toggle navigation. Photo by: Torsten Dietrich. Floodplain: Words to Know Alluvium: A general term for sediment rock debris such as gravel, sand, silt, and clay deposited by running water.

Backswamp: The lower, poorly drained area of a floodplain that retains water. Erosion: The gradual wearing away of Earth surfaces through the action of wind and water.

Levee natural : A low ridge or mound along a stream bank, formed by deposits left when floodwater slows down on leaving the channel. Meander: A bend or loop in a stream's course. Oxbow lake: A crescent-shaped body of water formed from a single loop that was cut off from a meandering stream.

Silt: Fine earthy particles that are smaller than sand and carried by moving water and deposited as a sediment. Terrace: The exposed portion of a former floodplain that stands like a flat bench above the outer edges of the new floodplain. Yazoo stream: A small stream that enters a floodplain and flows alongside a larger stream or river for quite a distance before eventually flowing into the larger waterway.

What Is a year Flood? Web Sites "Basics of Flooding. Also read article about Floodplain from Wikipedia. User Contributions: 1. Dear writer, Keep up the good work. Nice article, I really enjoyed. In reference to Pantanal, I learned so much abiut the area and I wish to visit there as soon the Carnival in Salvador bahia finishes. Can you tell HOW floodplains are created? Please show a diagram of it using steps.

This can be really helpful. Overall, I love all the information about science you give out. Pretty cool. A lot of cool Information. I'm taking biology and it helps me a lot. Awesome sauce. Comment about this article, ask questions, or add new information about this topic: Name:. E-mail: Show my email publicly. Human Verification:. Public Comment: characters. Living in a floodplain has advantages, such as access to a river and rich soil, but the risk of flooding is a disadvantage.

Identify three methods of flood control. Three methods of flood control include forest and soil conservation, dams, and artificial levees. Describe the life cycle of a lake. Along the Paraguay River in west-central Brazil and parts of Bolivia and Paraguay lies the Pantanal, a floodplain of more than 77, square miles. The Pantanal is considered one of the richest ecosystems in the world, created by the annual flooding of the land. Flood protection — Floodplains provide a buffer space between a river and inhabited areas at risk of flood.

Maintaining water quality — Floodplains can act as a filter for nutrients and impurities. They can also reduce the amount of sediment in underground water sources.

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