What is a meander, its characteristics, formation and types

We start by clarifying what meanders are exactly. We can indicate that the meanders are the curves that describe the rivers as they pass. The rivers that run through the territory tracing this series of curves, of greater or lesser opening, are known as meandering or meandering rivers . Some of the main characteristics of meanders are shown below :

• 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.
• The final deposition of sediments gives rise to the formation of lobes or p oint 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 course 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 the classification of channels by Miall (1977), 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.

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 flow. In the higher speed section, 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 an 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.

Meanders can be of two types: divergent or embedded.

• The divergent meanders originate due to the low slope in floodplains.
• The embedded meanders 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.

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 those of the Mississippi River (United States, USA) are called bayou .

Here are some examples of well-known meanders :

• The El Melero meander , 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 meander of Brian (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 del Río Júcar in Alcalá del Júcar (Albacete), Hoces del Río Cabriel (Cuenca) and Hoces del Río Duratón (Segovia).

Having known all this about what are the meanderings, characteristics, types and details, we encourage you to learn more about freshwater with these other items AgroCorrn on Why are important rivers and lakes, the pollution of lakes and rivers: causes, consequences and how to avoid it and The most polluted rivers in the world .