Meanders: arise, disappear, channel and restore
Rivers sometimes wind their way through the landscape in a very capricious way and never run straight to the sea. Of course, from the higher source of a river, the landscape never slopes exactly evenly to the sea. The result is that a river always tries to find a lower point. The more erratic the landscape (due to height differences), the more curvy the river is. In addition, rivers are able to break down and carry material such as clay, sand and rocks. The material taken along is deposited in another location, which also partly determines the course of the river and especially the formation of so-called meanders.
Meander and descent name
A meander is a bend in a river that is generally part of a number of bends that occur in a river both to the left and to the right. The name meander comes from a four hundred kilometers long, strongly winding river formerly called Maeander and currently called Büyük Menderes, which flows at Miletus in southwestern Turkey.
Creation and disappearance of a meander
A meander does not arise overnight, but through a lengthy natural process. Because the water continues to flow through the river, such a process never stops.
Creation of meander
A meander may have arisen because the water in the outer bend (along the stoeever) flows faster and thus washes away soil. That soil is then deposited again on the other side of the river at the inner bend (along the sliding bank).
If this process continues for a long time, the curve will get bigger and bigger. The result is of course that the river becomes longer.
The beginning and the end touch
As the loop that is formed grows, there is a chance that the beginning and end of the loop will eventually touch. There is a chance that the river will continue straight ahead again and leave the loop left or right.
Several possibilities in the loop
In that loop a small lake in the shape of a horseshoe often forms, making it a horseshoe lake. Sometimes a dead arm or cold remains. A chill is a gully. Another possibility is that an island will be created between the meander and the new course of the river by a cut-off.
Example of a dry meander
An example of a partially dry meander and an island can be found in the hamlet of Diffelen near the municipality of Hardenberg in the province of Overijssel.
Effects of fast and slow flowing water
According to calculations, the ratio between the actual distance traveled by a river and the distance between the source and the sea is approximately 3: 1. However, this ratio is also strongly dependent on the course of the river. In a fast-flowing river, the water flows for miles in a fairly straight line. Examples of this are the Maas and the Rhine. When the water flows less quickly, it finds its way from one lowest point in a landscape to another. In this way a ribbon of meanders is created. An example of such a meander river is the Overijsselse Vecht.
Influence of flowing water on the landscape
Rivers greatly influence the landscape they flow through. Running water can carry sand, clay and even gravel, as well as deposit material that crumbles from the banks elsewhere. The carrying capacity of water is strong enough to carry those materials. The effects of this are clearly visible in the Dutch river landscape. The flowing water has created basin soils and banks of banks. Bowl soils are low-lying areas in the river area that are often flooded in winter. The soil of basin soils consists of heavy river clay. Levees are heights along a river that have been created by the deposition of material carried along by the river. The hills of South Limburg were largely created by rivers and streams because these have dug deep valleys and hills have been formed by deposition.
Channeling and restoring meanders
Over the centuries, many meanders have disappeared because rivers have been channeled. Channeling is the straightening of a watercourse with many bends (meanders) so that parts of it resemble a canal. By channeling a river, the water flows faster and too much water can cause nuisance. Partly for that reason and to prevent drought because the water drains away too quickly, rivers are sometimes restored to their original watercourse, which is also called hermeander. Nature lovers are also in favor of restoring meanders and returning the river to its previous course, as in the Dynamisch Beekdal: Meander Kasteel Heeswijk project.