Braid bar
Encyclopedia
Braid Bars, or mid-channel bars, are landforms in a river
that begin to form when the discharge
is low and the river is forced to take the route of less resistance by means of flowing in locations of lowest elevation. Over time, the river begins to erode the outer edges of the bar, causing it to become a higher elevation than the surrounding areas. The water level decreases even more as the river laterally erodes the less cohesive bank material resulting in a widening of the river and a further exposure of the braid bar. As the discharge increases, material may deposit about the braid bar since it is an area in the river of low velocity due to its increased elevation than the surrounding areas. During times of extremely high flow, the bars may become covered; only to resurface when the flow decreases. Most braid bars do not remain stable or in one location. However, vegetation succession on braid bars can increase the stability of the landform. They are commonly composed of sand
or gravel
and typically occur in braided rivers
. A braid bar is a perfect place for a picnic
during levels of low-discharge.
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
that begin to form when the discharge
Discharge (hydrology)
In hydrology, discharge is the volume rate of water flow, including any suspended solids , dissolved chemical species and/or biologic material , which is transported through a given cross-sectional area...
is low and the river is forced to take the route of less resistance by means of flowing in locations of lowest elevation. Over time, the river begins to erode the outer edges of the bar, causing it to become a higher elevation than the surrounding areas. The water level decreases even more as the river laterally erodes the less cohesive bank material resulting in a widening of the river and a further exposure of the braid bar. As the discharge increases, material may deposit about the braid bar since it is an area in the river of low velocity due to its increased elevation than the surrounding areas. During times of extremely high flow, the bars may become covered; only to resurface when the flow decreases. Most braid bars do not remain stable or in one location. However, vegetation succession on braid bars can increase the stability of the landform. They are commonly composed of sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
or gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
and typically occur in braided rivers
Braided river
A braided river is one of a number of channel types and has a channel that consists of a network of small channels separated by small and often temporary islands called braid bars or, in British usage, aits or eyots. Braided streams occur in rivers with high slope and/or large sediment load...
. A braid bar is a perfect place for a picnic
Picnic
In contemporary usage, a picnic can be defined simply as a pleasure excursion at which a meal is eaten outdoors , ideally taking place in a beautiful landscape such as a park, beside a lake or with an interesting view and possibly at a public event such as before an open air theatre performance,...
during levels of low-discharge.