Levees can also be built or strengthened artificially. Artificial levees are often constructed by stacking dirt, sand, or pebbles on a flat, cleared area. Levees can also be formed of wood, plastic, or metal blocks in areas where the flow of a river is high. The most famous example of an artificial levee is the Mississippi River Gulf Outlet (MRGO), which was constructed to reduce flooding along the Gulf Coast of Louisiana. The outlet cuts through a barrier island and allows water to drain away from the mainland United States into the Gulf of Mexico.
Artificial levees can have adverse effects on the surrounding environment. They can destroy the fish habitat that existed before they were built and prevent natural floodwater flows. Artificially raised bogs or marshlands can become new sites for development because they are not affected by fire or natural disasters.
The placement of artificial levees can have important consequences for future flooding events. If an area already suffers from flooding then adding more levees will not help prevent damage or loss of life. However, if the land is relatively dry then building levees could cause problems for people who live there or for farmers who need free drainage space.
Artificial levees can also protect human settlements from floods. If you live near a large city then it may be protected by a federal agency such as the US Army Corps of Engineers or a state agency.
Levees are normally parallel to the river's flow, therefore they can assist direct the river's flow. The stacks create low areas that protect homes and businesses from flooding.
Artificial levees can be good alternatives to natural levees when you want to build something on top of the land or use the land for some other purpose than just being flooded. However, artificial levees can also do more harm than good if they cross-connect with other parts of the flood control system or are not maintained properly. Natural levees can only cause damage if they fail completely. This means that they are less likely to cause damage compared to an equivalent size of stack built entirely out of earth.
Natural levees can be made out of anything that can be moved, such as trees, brush, dirt, or concrete. They work by reducing the velocity of the water flowing past them. As the water slows down, its pressure decreases which allows it to seep through small gaps in between the objects that make up the levee. This process is called "flooding" and it helps to keep buildings safe from flooding. Without these protective barriers, entire cities would be destroyed by floods every time there is heavy rain or snowmelt.
Levees are often constructed of earth. Natural water movement pushes silt to the side, forming a natural levee. River banks are frequently somewhat raised above the river bottom. Levees are formed by the banks, which are comprised of sand, silt, and other materials pushed aside by the rushing water. The height of the bank determines how high the water can rise before it starts spilling over the top.
Human-made levees can be made of anything that will hold back water, such as concrete or metal. In some cases, they replace the function of natural levees. Human-made levees help protect land that would otherwise be flooded by allowing for more controlled flooding. They also provide better protection against large floods than the surrounding land might have without them.
Natural and human-made levees work together to protect towns and cities across the world from rising waters. Without these protective measures, many more people would be forced to move away from their homes every time there is a flood. This phenomenon is called "flooding-induced migration."
Flooding-induced migration is a problem not only in developing countries, but in industrialized nations as well. For example, neighborhoods near major highways are likely to be damaged by storms and need reconstruction or repair. As part of this process, old houses in these areas may be demolished and new ones built instead.
Levee Varieties Natural or man-made levees can exist. When silt settles on the river bank, it raises the level of the land around the river, forming a natural levee. Where there is no soil accumulation, people may build levees to protect villages or farmland from flooding. Levees can also be used as defense measures by armies or police forces when protecting settlements or urban areas.
The word "levee" comes from old French and Latin words meaning "hill" or "raised area." In North America, levees usually refer to earthen barriers built along rivers, lakes, and coastal inlets to prevent erosion and flood damage. The United States Army Corps of Engineers (USACE) conducts more than 10,000 civil works projects annually to maintain and improve navigability through construction of dams, locks, and other structures. It also performs environmental services such as flood control, water supply, and wildlife habitat creation. The USACE has nearly 30,000 employees dedicated to its work.
There are three main types of levees: earth-filled, masonry, and composite.
Earth-filled or natural levees are formed by the action of sediment settling into depressions in the riverbank. They can range in height from a few feet to over 100 feet.
Levee Development Natural levees are embankments formed by river sediments deposited during floods. This not only raised river banks, but also protected them from erosion by water currents. Levees were first used in the Middle East around 8500 BC, and eventually spread to Europe and North America.
People built levees for several reasons. They could be used to protect fields or settlements, help control flooding, or as a form of urban planning. Levees were commonly constructed with local materials available on site, such as earth, sand, and gravel. Sometimes they included large stones that could not be moved easily. In some cases, they were made from wood or metal.
In the Middle East, levees were used to protect fields from floodwaters and provide land for farming. They often consisted of a low wall of packed dirt or stone. These helped hold back the water while allowing crops to grow. Levees were also used within cities to prevent flooding. As cities grew larger, it was impossible for everyone to leave when a storm approached, so people needed ways to protect themselves. Levees provided this protection by blocking off streets when storms hit, reducing damage to buildings.
In Europe, levees were used for similar purposes to those in the Middle East. However, they were usually made out of timber instead.
Some levees regulate the flow of water for farmers and their surrounding fields, while others protect towns from increasing river levels. A dam, like a levee, can be either natural or man-made. They are also used to build reservoirs for drinking water and to regulate water for hydroelectric power generation.
Natural dams can be found in rivers without any human intervention. These are often made of rock barriers that prevent the water from flowing too fast or too slow. Some examples of natural dams include the Great Smoky Mountains National Park in North Carolina and Virginia, the Niagara Falls, and the Colorado River near Grand Canyon National Park.
Man-made dams consist of structures built across streams or rivers with the intention of storing or regulating water for use for irrigation, hydropower generation, or other purposes. Dam construction has been an important factor in the development of agriculture and cities across the world. Today, billions of dollars are spent annually on new dams.
Dams have many negative effects on the environment. They can destroy habitats for fish and other aquatic life by preventing them from reaching certain areas of river or lake bed. This can also affect larger animals such as birds and mammals because they are unable to find adequate food or shelter elsewhere. Dams can also cause extinction if they cause large scale flooding which destroys all available land habitat. Finally, dams can lead to conflict between humans and wildlife.