Braided river

The channels and braid bars are usually highly mobile, with the river layout often changing significantly during flood events. Channels move sideways via differential velocity: On the outside of a curve, deeper, swift water picks up sediment (usually gravel or larger stones), which is re-deposited in slow-moving water on the inside of a bend.

The braided channels may flow within an area defined by relatively stable banks or may occupy an entire valley floor. The Rakaia river in Canterbury, New Zealand has cut a channel 100 metres deep into the surrounding plains.

Conditions which promote braided channel formation are:

• An abundant supply of sediment
• Rapid and frequent variations in water discharge
• Erodable banks

Extensive braided river systems are found in only a few regions world-wide:

• Alaska
• Canada
• New Zealand - South Island
• the Himalayas

All the above regions contain young, eroding mountains.