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The channels or river beds of a river are the conduit through which water circulates. Its morphology (in terms of sinuosity and braiding or number of internal bars) allows differentiating three types of riverbeds: rectilinear, of type braided or anastomosed and meandering or meandering.
At Ecologista Verde we will focus on the latter type, so if you want to know what meanders are and more details about them, check out this article where we talk about what is a meander, its characteristics, its formation and its types and in which, in addition, some examples of well-known meanders are shown.
What is a meander and its characteristics
We start by clarifying what meanders are exactly. We can indicate that meanders are the curves that describe rivers in its wake. The rivers that run through the territory tracing this series of curves, of greater or lesser opening, are known as meandering or meandering rivers. Below are some of the meander main characteristics:
- They present a very marked sinuosity, by which they are easily distinguishable.
- They usually originate in rivers located on alluvial plains with little slope.
- It has a greater capacity to drag and transport sediments, compared to straight rivers.
- Final sediment deposition results in the formation of lobes o point bars.
- An increase in the flow of the river accentuates the sinuosity of the meanders.
- The dynamic behavior of meanders is the product of the erosive and sedimentary action of fresh waters.
- The route of these meandering rivers is unstable, being able to form a horseshoe or oxbow lake.
- The formation of meanders differs according to the river, as it depends on factors such as flow, current speed and the material composition of the channel. It is also taken into account for its classification: according to Miall's (1977) classification of channels, meandering channels are those with a sinuosity> 1.5 (sinuosity index).
- They increase the length of the river.
- Among the main parts of a meander, we can indicate that the external part, due to greater speed and turbulence, is the erosive zone; while, the internal part is that of sedimentation.
How a meander is formed
After knowing its definition and its characteristics, you may wonder how meanders are formed. Although we have previously indicated that it is a process that depends on various factors, now we will clarify it.
The meanders are formed in alluvial plains, with little slope, due to changes in the water current. In the section of higher speed, the erosive processes are accentuated, so that the water excavates the shore, giving rise to a concave shape of the land; meanwhile, in the part where the water flows more slowly, sedimentation processes predominate.
Knowing what the definition of meander is and how the curves of rivers are formed, now some more questions arise, such as, for example, what is a abandoned meander and what is a meander choke. An increase in the flow of rivers increases the capacity to carry sediments and causes the limits of the meander of a river to blur. In this way, in what is known as narrowing of the meander, the waters follow a more rectilinear course and the accumulation of sediment at the ends that connect the new course with the old meander gives rise to what is known as an abandoned meander.
Meander types
Meanders can be of two types: divergent or embedded.
- The divergent meanders they originate due to the low slope in alluvial plains.
- The embedded meanders They are formed by changes in the base level, so that the water flows in a downward direction, and they are located in narrow and steep valleys. Example: embedded meander of the Duero in Los Infierno.
Known meander names
Depending on their location, meanders are given a specific name. For example, the meanders of the Ebro river in Aragon are known as galachos while, the Del Rio Mississippi (United States, USA) are called bayou.
Here are some well-known meander examples:
- The meander El Melero, located on the eastern limit of the Sierra de Gata, is formed by the Alagón River, as it passes through the Hurdes region (Cáceres).
- In the Matanza-Riachuelo river we find the Brian meander (Buenos Aires, Argentina), which stands out for being the only meander that has remained after the works carried out to rectify the channel of the Riachuelo.
- The meander of the Say or the Old Mother of the Bogotá River, located in Fontibón, was formed from the artificial modification of the old Bogotá riverbed. This meander was declared a Distral Wetland Ecological Park in 2004.
- Hoces of the river Júcar in Alcalá del Júcar (Albacete), Hoces del Río Cabriel (Cuenca) and Hoces del Río Duratón (Segovia).
After having known all this about what meanders are, their characteristics, types and more details, we encourage you to learn more about fresh waters with these other articles by Green Ecologist on Why are rivers and lakes important, Lake Pollution and rivers: causes, consequences and how to avoid it and The most polluted rivers in the world.
If you want to read more articles similar to What is a meander, its characteristics, formation and typesWe recommend that you enter our Nature Curiosities category.
