River Valley: What is it, how it is formed and examples

A river valley is a terrestrial relief form characterized by a depression or land basin that has been formed by the erosion of a river or a stream. Generally, it is between two elevations, such as mountains or hills. Depending on the slope, the type of rock, the river flow and the time of action, they can acquire different forms such as in V or U.

We recommend reading this post about river erosion: what is, types, consequences and examples.

The formation of a river valley takes place in different steps:

1. River birth in high areas: To believe a river valley, there must be the presence of a river or stream that has its nascent in mountainous or high altitude areas. From there, water flows with force by a pronounced slope, causing the erosion of the land.
2. Vertical erosion in the upper valley: During the initial stage the current has great energy and erodes mainly down (vertical erosion), carving the river bed through the abrasive action of transported materials. The result is a valley in the form of “V” of steep sides. The course can be straight or adapt to geological structures such as fractures, folds or failures, creating a more tortuous tour.
3. Transition to the Middle Valley: As the river progresses and more tributaries, the flow increases, the slope decreases and the current becomes slower. At this stage, lateral erosion processes (widening of the channel) and sediment deposition are combined. In this way the valley widens and the river begins to form meanders.
4. Development of the lower valley: Upon reaching flatter or flat areas, the gradient is very low and the deposition of sediments on erosion predominates. Thus, meanders become broader and a wide and flat flood plain, product of floods and sediment tank can be formed.

• River bed (or channel): Part of a valley where the water flows. It can be narrow and deep in mountainous areas, or wide and shallow in plains.
• Banks or shores: They make up the side edges of the channel. In some places they can form ravines or steep slopes. You may be interested in this article about the riverbank: what is, flora and fauna.
• Flood plain: Planning that exists on the sides of the river, which is flooded recurrently. It is formed by the deposition of sediments and are characterized by being dynamic environments that house a great wealth of species.
• Meanders: pronounced and winding curves that form the river in its middle and lower course. It is formed when the water decreases the speed during the course of the river and in the alluvial plains when the slope is scarce.
• River terraces: ancient levels of channel that were higher due to erosion or river level changes. They can be seen as steps to the sides of the valley.
• Garrows or throats: When erosion is very intense and vertical, the valley can be transformed into a cannon. For example: the Grand Canyon of Colorado (United States).

Amazonas River Valley

It extends throughout South America through countries such as Brazil, Peru, Colombia and others. It is the world’s largest river valley and contains the largest hydrographic basin on the planet. Throughout its route, the Amazon river flows through a vast tropical plain forming meanders, sand banks and an extensive network of tributaries.

Pilcomayo River Valley

Extensive hydrographic basin shared by Argentina, Bolivia and Paraguay, which is part of the system of the Río de la Plata. The river is born in the foothills of the Cordillera de los Frailes in Bolivia and receives water from numerous tributaries. In its course it crosses the region of the Gran Chaco, characterized by plains, estuaries, lagoons and riverside jungle areas.

Nile Valley

It occupies the final part of the Nile River basin as it passes through Egypt. It is a valley that has an average 19 kilometers wide from Asuán to Cairo and extends to the north as a thin green ribbon on the arid African desert.

Loira Valley

Located in the center-west of France, the Loira River Valley has been generated by the action of the Loira River that flows through an area of low hills and agricultural plains, forming wide meanders and river terraces. This valley has been intensely exploited by agriculture and the construction of castles, which has earned it to be declared a World Heritage by UNESCO.

• Training: A river valley is formed by erosion and sedimentation caused by a river or stream over time. On the contrary, a glacier valley is formed by the movement of a glacier.
• Process: The river models the terrain through erosion processes and deposition of sediments. The glacier acts abrasively on the terrain, carving and wearing the rocks and sediments where it passes. Glaciers also transport large amounts of sediments, creating blackberries and erratic.
• Shape: The river valleys usually have the shape of “V” in its upper section (when the river cuts deeply into a harder terrain) and can become wider and in the shape of a meander -shaped in lower sections while the glaciers valleys have a U -shaped shape due to the deepest and deeper erosion compared to the river valleys.
• Characteristics: The river valleys are common in areas of plains, large valleys, or transition zones, and have a continuous development due to the river water flow. Instead, glacial valleys are typical in high mountain areas or cold latitudes.

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