Anabranches

Anabranches are a pattern in river systems where the main channel divides into two or more separate channels that flow around an intervening landform and later rejoin downstream. The resulting reach contains a network of channels separated by mid-channel islands or stabilized floodplain areas. This contrasts with braided channels, which consist of many short, constantly shifting channels that interchange frequently around mobile sediment bars.

Morphology and dynamics: In anabranching reaches, the split channels remain distinct for a substantial distance before reconverging. The presence of mid-channel islands, vegetated banks, and a broad floodplain is common. The distribution of flow among the branches can vary with discharge and season, influencing sediment deposition, bank growth, and channel migration along the reach.

Formation and drivers: Anabranching develops where the river encounter a relatively wide, low-gradient floodplain and where bank materials and vegetation promote channel stability. Sediment supply, bedrock or architectural constraints, and hydrological regimes all contribute. Human activities such as river training, levee construction, or modification of floodplains can also create or enhance anabranching patterns.

Hydrology and sediment: Water splits between branches, altering velocity, sediment transport, and deposition patterns in each channel. Islands and floodplain areas often accumulate sediment and organic matter, affecting habitat structure and nutrient dynamics.

Ecology and management: Anabranching landscapes support diverse habitats, including wetlands, forests, and aquatic ecosystems. They influence flood conveyance, fish passage, and nutrient cycling. Restoration and management efforts consider channel connectivity, floodplain integrity, and the stability of individual branches to maintain ecological values and flood risk goals.