Terminology of the

subenvironments of a river

Fluvial Environments

Meandering rivers.- based on the recognition of point bars from their distinctive vertical profile

Sediments in meandering rivers may be gravel-, sand- or silt-dominated.

The lateral accretion of the point bar is the most distinctive feature of meandering-river deposits, but some bars in braided rivers also exhibit lateral accretion.

Braided river is characterized by a wide active valley with several or many component channels of varying sinuosity

The main sediment load may be sand or gravel

Individual channels undergo rapid migration, switches in position and

abandonment

The deposits of braided rives are typically composed of an assemblage of crossbedded fragments of bar deposits, exhibiting accretion directions oriented in almost any direction, the most common

being downstream and oblique to channel orientation.

Anastomosed rivers occur in areas of active vertical aggradation, such as coastal systems during a time of rapidly rising sea level, and in the case of inland systems where a river valley is

backfilling behind a constriction

Many channels of variable sinuosity occur

They are relatively stable in position, showing little or no evidence of the

lateral migration common to the meandering and braided styles

Broad floodplains occur between the channels

These may be wetlands, peat swamps or desiccated flats, depending on the climate

Straight rivers occur in areas of very low slope, such as near base level. As such, they are most common as the distributaries of certain deltas.

Although the river itself may be nearly straight,

there is typically a slightly sinuous deep channel, and long, narrow bars, called

alternate bars, accumulate along the banks inside the meanders defined by this

channel.