Point bar in the context of "Towheads"

Play Trivia Questions online!

or

Skip to study material about Point bar in the context of "Towheads"

Ad spacer

⭐ Core Definition: Point bar

A point bar is a depositional feature made of alluvium that accumulates on the inside bend of streams and rivers below the slip-off slope. Point bars are found in abundance in mature or meandering streams. They are crescent-shaped and located on the inside of a stream bend, being very similar to, though often smaller than, towheads, or river islands.

Point bars are composed of sediment that is well sorted and typically reflects the overall capacity of the stream. They also have a very gentle slope and an elevation very close to water level. Since they are low-lying, they are often overtaken by floods and can accumulate driftwood and other debris during times of high water levels. Due to their near flat topography and the fact that the water speed is slow in the shallows of the point bar they are popular rest stops for boaters and rafters. However, camping on a point bar can be dangerous as a flash flood that raises the stream level by as little as a few inches (centimetres) can overwhelm a campsite in moments.

↓ Menu

>>>PUT SHARE BUTTONS HERE<<<
In this Dossier

Point bar in the context of Meander

A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank (cut bank or river cliff) and deposits sediments on an inner, convex bank which is typically a point bar. The result of this coupled erosion and sedimentation is the formation of a sinuous course as the channel migrates back and forth across the axis of a floodplain.

The zone within which a meandering stream periodically shifts its channel is known as a meander belt. It typically ranges from 15 to 18 times the width of the channel. Over time, meanders migrate downstream, sometimes in such a short time as to create civil engineering challenges for local municipalities attempting to maintain stable roads and bridges.

↑ Return to Menu

Point bar in the context of Cut bank

A cut bank, also known as a river cliff or river-cut cliff, is the outside bank of a curve (meander) in a water channel (stream), which is continually undergoing erosion. Cut banks are found in abundance along mature or meandering streams, they are located opposite the slip-off slope on the inside of the stream meander. They are shaped much like a small cliff, and are formed as the stream collides with the river bank. It is the opposite of a point bar, which is an area of deposition of material eroded upstream in a cut bank.

Typically, cut banks are steep and may be nearly vertical. Often, particularly during periods of high rainfall and higher-than average water levels, trees and poorly placed buildings can fall into the stream due to mass wasting events. Given enough time, the combination of erosion along cut banks and deposition along point bars can lead to the formation of an oxbow lake.

↑ Return to Menu

Point bar in the context of Jezero (crater)

Jezero (ICAO: JZRO) is a crater on Mars in the Syrtis Major quadrangle, about 45.0 km (28.0 mi) in diameter. Thought to have once been flooded with water, the crater contains a fan-delta deposit rich in clays. The lake in the crater was present when valley networks were forming on Mars. Besides having a delta, the crater shows point bars and inverted channels. From a study of the delta and channels, it was concluded that the lake inside the crater probably formed during a period in which there was continual surface runoff.

In 2007, following the discovery of its ancient lake, the crater was named after Jezero, Bosnia and Herzegovina, one of several eponymous towns in the country. In some Slavic languages, the word jezero means 'lake'.

↑ Return to Menu

Point bar in the context of River channel migration

River channel migration is the geomorphological process that involves the lateral migration of an alluvial river channel across its floodplain. This process is mainly driven by the combination of bank erosion of and point bar deposition over time. When referring to river channel migration, it is typically in reference to meandering streams. In braided streams, channel change is driven by sediment transport.

It has been proposed that lateral migration is a particularly dominant erosive process in savanna landscapes.

↑ Return to Menu