Braided river

Viewed from above, a braided river has a network of branching and rejoining channels separated by bars. These mid-channel sediment deposits may be submerged, exposed as gravel or sand bars, or, when stabilized by vegetation, develop into islands. Channels can shift around the bars, creating the interwoven pattern that gives the river its name. A braided pattern describes the plan view of a river reach and is distinct from a single sinuous meandering channel.

Sediment that a river can no longer transport is deposited in the channel. Coarser material may form the nucleus of a bar; as flow slows, finer sediment can accumulate and the bar may grow. Water is diverted around it into flanking channels, which can deepen and erode their banks. With falling water levels, bars become exposed; later high flows may submerge them, erode or enlarge them, or redirect flow. Readily erodible banks and a substantial bedload encourage channel shifts, while discharge variability can influence deposition, erosion and vegetation establishment.

Braided channels commonly change during and after floods, when large flows can move sediment and divert water among channels. Bar formation and destruction are not necessarily evidence that a river carries an anomalously excessive total sediment load: channel pattern reflects the interaction of discharge, sediment load, slope, channel dimensions and the material forming the bed and banks. Braiding is one possible way a river system adjusts to these conditions, rather than a pattern determined by a single factor.

Braided channels occur in many settings, including rivers fed by mountain or glacial sediment and rivers with highly variable flows. Their shifting channels and bars create heterogeneous river habitats, but they can also make crossings and infrastructure near the channel more difficult to maintain. The term should be applied to an observable multichannel pattern, not assumed solely from a river's sediment supply or flood regime.