Difference between revisions of "Bar"
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{{Definition|title= | {{Definition|title= | ||
| − | |definition= | + | |definition=Elongated (partially) submerged bed structure with a length typically a few orders of magnitude larger than the water depth (i.e. larger than ripples, dunes or sandwaves). Bars arise from the interaction of the sediment bed with (tidal) currents and waves.}} |
| − | == | + | ==Estuarine bars and spits== |
| − | A | + | Bars in estuaries, tidal lagoons and rivers develop naturally in flow convergence zones, often in relation with channel meandering (for example, point bars in rivers). Estuarine bars also occur where ebb- and flood-dominated [[#Tidal channel|channels]] meet. Bars that partially block the openings to minor streams and lagoons are mainly due to littoral drift; these bars are generally referred to as spits. Bars can raise above the high water level, but they are often intratidal or subtidal. |
| + | |||
| + | ==Swash bars== | ||
| + | A swash bar is a nearly horizontal shore parallel ridge formed on the intertidal beach or on a tidal flat due to the landward transport of sand or gravel by wave uprush (swash). They may be related to onshore moving breaker bars. | ||
| + | |||
| + | ==Breaker bars== | ||
| + | Breaker bars (also called '''[[nearshore sandbars]]''') are elongated submerged embankments of sand or gravel built in the breaker zone due to the action of breaking waves and cross-currents<ref name=”Karsten”>Mangor, Karsten. 2004. “Shoreline Management Guidelines”. DHI Water and Environment, 294pp.</ref>. | ||
*There can be several rows of bars. | *There can be several rows of bars. | ||
| − | *Bars are very mobile formations, which tend to be in | + | *Bars are very mobile formations, which tend to be in unstable equilibrium with the wave climate and tide conditions, which means that they are constantly changing. |
*The overall tendency is that the bars are moving seawards during storm wave conditions and landwards during conditions dominated by smaller waves and swell. | *The overall tendency is that the bars are moving seawards during storm wave conditions and landwards during conditions dominated by smaller waves and swell. | ||
*At intervals there are gaps in the bars formed by the [[rip current]]s. | *At intervals there are gaps in the bars formed by the [[rip current]]s. | ||
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==See also== | ==See also== | ||
| + | :[[Nearshore sandbars]] | ||
:[[Rhythmic shoreline features]] | :[[Rhythmic shoreline features]] | ||
:[[Stability models]] | :[[Stability models]] | ||
Latest revision as of 11:22, 27 March 2021
Definition of :
Elongated (partially) submerged bed structure with a length typically a few orders of magnitude larger than the water depth (i.e. larger than ripples, dunes or sandwaves). Bars arise from the interaction of the sediment bed with (tidal) currents and waves.
This is the common definition for , other definitions can be discussed in the article
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Estuarine bars and spits
Bars in estuaries, tidal lagoons and rivers develop naturally in flow convergence zones, often in relation with channel meandering (for example, point bars in rivers). Estuarine bars also occur where ebb- and flood-dominated channels meet. Bars that partially block the openings to minor streams and lagoons are mainly due to littoral drift; these bars are generally referred to as spits. Bars can raise above the high water level, but they are often intratidal or subtidal.
Swash bars
A swash bar is a nearly horizontal shore parallel ridge formed on the intertidal beach or on a tidal flat due to the landward transport of sand or gravel by wave uprush (swash). They may be related to onshore moving breaker bars.
Breaker bars
Breaker bars (also called nearshore sandbars) are elongated submerged embankments of sand or gravel built in the breaker zone due to the action of breaking waves and cross-currents[1].
- There can be several rows of bars.
- Bars are very mobile formations, which tend to be in unstable equilibrium with the wave climate and tide conditions, which means that they are constantly changing.
- The overall tendency is that the bars are moving seawards during storm wave conditions and landwards during conditions dominated by smaller waves and swell.
- At intervals there are gaps in the bars formed by the rip currents.
See also
References
- ↑ Mangor, Karsten. 2004. “Shoreline Management Guidelines”. DHI Water and Environment, 294pp.
