Friday, October 13, 2017

The Stunning Beauty of Braided Rivers

Most rivers flow in one broad channel of water, but some rivers split into lots of small channels that continually split and join each other to give a braided appearance. These are called braided rivers.

Braided rivers are usually wide but shallow. They typically form on fairly steep slopes and carry large amount of coarse-grained sediments. When the river’s flow decreases, these sediments get deposited on the river bed leaving behind small temporary islands of sands that cause the river’s channel to split. Aside from a steep gradient and abundance of sediments, a variable water discharge rate is essential to their formation. Consequently, braided rivers exist near mountainous regions, especially those with glaciers. Braided channels are also found in environments that dramatically decrease channel depth, and hence channel velocity, such as river deltas, alluvial fans and peneplains.

A braided river in Iceland.

The pattern of the braided channels will change over time as the sediment islands get eroded away and deposited in new islands as the speed and amount of water in the river changes.

Rivers with braided channels look stunningly beautiful in satellite images or from airplanes. Here are some of the most beautiful examples of braided rivers.

The Rakaia River in the Canterbury Plains in New Zealand's South Island is a beautiful example of a braided river. It is one of the largest braided rivers in New Zealand. Photo credit: Andrew Cooper/Wikimedia

The Brahmaputra River in Tibet, India and Bangladesh is another classic example. The river originates in Tibet and enters India through the state of Arunachal Pradesh. The river gets intricately braided once it enters the state of Assam where it acquires its common name Brahmaputra. For the next 700 km of its braided course through the valley, it gets mighty big even in the dry season. During rains, its banks are more than 8 km apart.

The Waitaki River is another large braided river in the South Island of New Zealand. It drains the Mackenzie Basin and runs some 110 kilometers south-east to enter the Pacific Ocean between Timaru and Oamaru. Photo credit: Google Earth

The Tagliamento River in north-east Italy is braided as it flows from the Alps to the Adriatic Sea. 

The Waimakariri River in the South Island of New Zealand, is a braided river, about a kilometer wide with many changing channels cutting through the shingle. 

A Landsat image of a braided section of the Congo River. 

The Ob River in western Siberia, Russia, is the world's seventh longest river.
The ParanĂ¡ River in South America. This photograph shows a 29-kilometer stretch of the ParanĂ¡, downstream of the small city of Goya, Argentina.

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