Fluvial Process and landform

Origin of River Stream channels can be created on a newly exposed surface or develop by the expansion of an existing channel network. Their formation depends upon water flowing over a slope becoming sufficiently concentrated for channel incision to occur. Once formed, a channel may grow to form a permanent feature.

Types of Rivers Stream scientist categorize streams based on the balance and timing of the storm water runoff and baseflow components. There are three main categories: Ephemeral streams flow only during or immediately after periods of precipitation. They generally flow less than 30 days out of the year and persist as dry riverbeds throughout most of the year. Intermittent streams flow only during certain times of year. Seasonal flow in an intermittent stream usually last longer than 30 days per year. Perennial streams flow continuously during both wet and dry times. Base flow is generally generated from the movement of ground water into the channel.

Floodplain Morphology

Most rivers, save those in mountains, are flanked by an area of fairly flat land called a floodplain, which is formed from debris deposited when the river is in flood. Small floods that occur frequently cover a part of the floodplain, while rare major floods submerge the entire area. The morphology of floodplains is intimately linked with the form and behaviour of the river channels that shape them. Various processes of deposition, reworking and erosion are involved in the formation and development of floodplains.

Floodplain geomorphic units

Levees; are clearly visible as the raised strips of land running along the channel margins. The height of levees is scaled to the size of the channel and their presence implies a relatively stable channel location. Crevasse splays; Levees can be breached by floodwaters. This may lead to the formation of a crevasse splay, a fan-shaped lobe of sediment deposited when sediment-charged water escapes and flows down the levee. If flow is sufficiently concentrated, a new channel may be cut and deepened by scour. Backswamps;The build-up of sediment in the channel may mean that the channel is at a higher elevation than the surrounding floodplain. When levees are overtopped, water can enter the lower-lying area on the other side of the levee. This may be a depression or a swamp area characterised by wetland vegetation

Flood channels; are relatively straight channels that bypass the main channel. They have a lesser depth than the main channel and are dry for much of the time, only becoming filled with water as the flow approaches bankfull. Floodouts; are associated with dryland channels. They occur where floodwaters leave the main channel and branch out onto the floodplain in a number of distributory channels. Meander scroll bars; In some cases, former point bar deposits can be seen in the surface topography of the floodplain as scroll bars, with each scroll representing a former location of the point bar. The undulating ridge and swale topography that results consists of higher ridges separated by topographic lows called swales. Meander scroll bars can be seen as a series of vegetated ridges on the point-bar deposits