Distributary
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A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel, a phenomenon known as river bifurcation. A distributary is effectively the opposite of a tributary, which is a stream that flows towards and into another stream or river. Distributaries are often found where a stream approaches a lake or an ocean; as such, they are a common feature of river deltas. They can also occur inland, on alluvial fans, or where a tributary stream bifurcates as it nears its confluence with a larger stream. In some cases, a minor distributary can divert so much water from the main channel that it can later become the main route.
Rhine–Meuse–Scheldt delta, with the flow from right to left, showing several streams branching off from their main streams
Satellite image of part of the Rhine–Meuse–Scheldt delta
A seasonal distributary of the Kaveri River on the Kaveri delta, near Nannilam, India
Delta of Papua New Guinea's Fly River
River bifurcation
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River bifurcation occurs when a river flowing in a single channel separates into two or more separate streams which then continue downstream. Some rivers form complex networks of distributaries, typically in their deltas. If the streams eventually merge again or empty into the same body of water, then the bifurcation forms a river island.
Bifurcation in Hövelhof, Germany
River deltas, such as the pictured delta of the Salween River in Myanmar, often show bifurcations. The water flows in from the lower section of the image and passes on both sides of the large island in the center.