Braiding develops where abundant sediment, variable flow and erodible banks support mobile bars and repeated channel division.
A braided river has several interlinked channels separated by active mid-channel bars. The bars are commonly unvegetated or only sparsely vegetated because they are frequently reworked. Channels split and rejoin around them, rather than simply branching permanently towards the sea.
When sediment supply exceeds local transport capacity, bed material accumulates as bars. Water is diverted around them and erodes new routes. Rising floods can mobilise or reshape the bars; falling flow exposes them and concentrates water into fewer channels. The pattern changes over time.
A high bedload supply, variable discharge, a wide shallow channel and easily eroded banks favour braiding. A fall in gradient can encourage deposition. Weak bank cohesion allows channels to widen and shift; vegetation can stabilise some bars and change the pattern. No single factor produces every braided river.
Slope failures, eroding mountains and tributaries can supply sediment naturally. Deforestation, mining and construction can increase it; dams can reduce downstream supply and alter flood peaks. The response depends on the balance between sediment supply, transport and bank stability, not on sediment volume alone.
Step by step
Supply exceeds transport
Sediment accumulates on the bed.
Bars divide the flow
Water takes different routes around the deposits.
Flow reworks the pattern
Floods, bank erosion and deposition move bars and channels.
Worked example: The Brahmaputra in Assam
NASA imagery shows the Brahmaputra widening and becoming braided as it leaves the Himalayan foothills for flatter terrain. Large sediment inputs and reduced transporting power help explain the bars. The warm, wet lowland receives sediment from a much larger mountain drainage system.
Watch out for this
Every multi-channel river is braided.
Stable vegetated islands may separate long-lived anabranching channels. Braiding specifically involves active bars and frequently changing channels.
Check your understanding
Which combination most strongly favours braiding?
- Very low sediment supply and resistant confined banks.
- No variation in flow and no movable sediment.
- Abundant bed material, variable discharge and erodible banks.