River bifurcations are critical but poorly understood elements of many
geomorphological systems. They are integral elements of alluvial fans,
braided rivers, fluvial lowland plains, and deltas and control the
partitioning of water and sediment through these systems. Bifurcations
are commonly unstable but their lifespan varies greatly. In braided
rivers bars and channels migrate, split and merge at annual or shorter
timescales, thereby creating and abandoning bifurcations. This behaviour
has been studied mainly by geomorphologists and fluid dynamicists.
Bifurcations also exist during avulsion, the process of a river changing
course on a floodplain or in a delta, which may take 102103 years and
has been studied mainly by sedimentologists. This review synthesizes our
current understanding of bifurcations and brings together insights from
different research communities and different environmental settings. We
consider the causes and initiation of bifurcations and avulsion, the
physical mechanisms controlling bifurcation and avulsion evolution,
mathematical and numerical modelling of these processes, and the
possibility of stable bifurcations. We end the review with some open
questions. Copyright (c) 2012 John Wiley & Sons, Ltd.