Tidal bore

Last updated

A bore in Morecambe Bay, in the United Kingdom Tidal Bore - geograph.org.uk - 324581.jpg
A bore in Morecambe Bay, in the United Kingdom
Video of the Arnside Bore, in the United Kingdom
The tidal bore in Upper Cook Inlet, in Alaska Turnagain-bore.jpg
The tidal bore in Upper Cook Inlet, in Alaska

A tidal bore, [1] often simply given as bore in context, is a tidal phenomenon in which the leading edge of the incoming tide forms a wave (or waves) of water that travels up a river or narrow bay against the direction of the river or bay's current.

Contents

Description

Bores occur in relatively few locations worldwide, usually in areas with a large tidal range (typically more than 6 meters (20 ft) between high and low tide) and where incoming tides are funneled into a shallow, narrowing river or lake via a broad bay. [2] The funnel-like shape not only increases the tidal range, but it can also decrease the duration of the flood tide, down to a point where the flood appears as a sudden increase in the water level. A tidal bore takes place during the flood tide and never during the ebb tide.

Undular bore and whelps near the mouth of Araguari River in northeastern Brazil. The view is oblique towards the mouth from airplane at approximately 30 m (100 ft) altitude. Undular bore Araguari River-Brazil-USGS-bws00026.jpg
Undular bore and whelps near the mouth of Araguari River in northeastern Brazil. The view is oblique towards the mouth from airplane at approximately 30 m (100 ft) altitude.

A tidal bore may take on various forms, ranging from a single breaking wavefront with a roller – somewhat like a hydraulic jump [4] [5] – to undular bores, comprising a smooth wavefront followed by a train of secondary waves known as whelps. [6] Large bores can be particularly unsafe for shipping but also present opportunities for river surfing. [6]

Two key features of a tidal bore are the intense turbulence and turbulent mixing generated during the bore propagation, as well as its rumbling noise. The visual observations of tidal bores highlight the turbulent nature of the surging waters. The tidal bore induces a strong turbulent mixing in the estuarine zone, and the effects may be felt along considerable distances. The velocity observations indicate a rapid deceleration of the flow associated with the passage of the bore as well as large velocity fluctuations. [7] [8] A tidal bore creates a powerful roar that combines the sounds caused by the turbulence in the bore front and whelps, entrained air bubbles in the bore roller, sediment erosion beneath the bore front and of the banks, scouring of shoals and bars, and impacts on obstacles. The bore rumble is heard far away because its low frequencies can travel over long distances. The low-frequency sound is a characteristic feature of the advancing roller in which the air bubbles entrapped in the large-scale eddies are acoustically active and play the dominant role in the rumble-sound generation. [9]

Etymology

The word bore derives through Old English from the Old Norse word bára, meaning "wave" or "swell."

Effects

Tidal bores can be dangerous. Certain rivers such as the Seine in France, the Petitcodiac River in Canada, and the Colorado River in Mexico to name a few, have had a sinister reputation in association with tidal bores. In China, despite warning signs erected along the banks of the Qiantang River, a number of fatalities occur each year by people who take too much risk with the bore. [2] The tidal bores affect the shipping and navigation in the estuarine zone, for example, in Papua New Guinea (Fly and Bamu Rivers), Malaysia (Benak at Batang Lupar), and India (Hoogly bore).

On the other hand, tidal bore-affected estuaries are rich feeding zones and breeding grounds of several forms of wildlife. [2] The estuarine zones are the spawning and breeding grounds of several native fish species, while the aeration induced by the tidal bore contributes to the abundant growth of many species of fish and shrimps (for example in the Rokan River). The tidal bores also provide opportunity for recreational inland surfing.

Scientific studies

Scientific studies have been carried out at the River Dee [10] in Wales in the United Kingdom, the Garonne [11] [12] [13] [14] [15] and Sélune [16] in France, the Daly River [17] in Australia, and the Qiantang River estuary [18] in China. The force of the tidal bore flow often poses a challenge to scientific measurements, as evidenced by a number of field work incidents in the River Dee, [10] Rio Mearim, Daly River, [17] and Sélune River. [16]

Rivers and bays with tidal bores

Rivers and bays that have been known to exhibit bores include those listed below. [2] [19]

Asia

Australia

Europe

United Kingdom

The Trent Aegir seen from West Stockwith, Nottinghamshire, 20 September 2005 Trent Aegir 2.JPG
The Trent Aegir seen from West Stockwith, Nottinghamshire, 20 September 2005
The Trent Aegir at Gainsborough, Lincolnshire, 20 September 2005 Trent Aegir 3.JPG
The Trent Aegir at Gainsborough, Lincolnshire, 20 September 2005
Tidal bore on the River Ribble River Ribble bore.jpg
Tidal bore on the River Ribble

Belgium

France

The phenomenon is generally named un mascaret in French. [21] but some other local names are preferred. [19]

Papua New Guinea

North America

United States

Tidal bore on the Petitcodiac River Tidal bore.jpg
Tidal bore on the Petitcodiac River
  • The Turnagain Arm of Cook Inlet, Alaska. Up to 2 meters (7 ft) and 20 km/h (12 mph).
  • Historically, the Colorado River had a tidal bore up to 6 feet, that extended 47 miles up river.
  • The Savannah River up to 10 miles (16 km) inland.
  • Small tidal bores, only a few inches in height, have been observed advancing up tidal bayous on the Mississippi Gulf Coast.

Canada

Most rivers draining into the upper Bay of Fundy between Nova Scotia and New Brunswick have tidal bores. Notable ones include:

  • The Petitcodiac River formerly had the highest bore in North America at over 2 metres (6.6 ft) in height, but causeway construction between Moncton and Riverview in the 1960s led to subsequent extensive sedimentation which reduced the bore to little more than a ripple. After considerable political controversy, the causeway gates were opened on April 14, 2010, as part of the Petitcodiac River Restoration Project and the tidal bore began to grow again. [23] The restoration of the bore has been sufficient that in July 2013, professional surfers rode a 1 metre (3.3 ft)-high wave 29 kilometres (18.0 mi) up the Petitcodiac River from Belliveau Village to Moncton to establish a new North American record for continuous surfing.
  • The Shubenacadie River, also off the Bay of Fundy in Nova Scotia. When the tidal bore approaches, completely drained riverbeds are filled. It has claimed the lives of several tourists who were in the riverbeds when the bore came in.[ citation needed ] Tour boat operators offer rafting excursions in the summer.
  • The bore is fastest and highest on some of the smaller rivers that connect to the bay including the River Hebert and Maccan River on the Cumberland Basin, the St. Croix and Kennetcook rivers in the Minas Basin, and the Salmon River in Truro. [24]

Mexico

Historically, there was a tidal bore on the Gulf of California in Mexico at the mouth of the Colorado River. It formed in the estuary about Montague Island and propagated upstream. It was once very strong, but diversions of the river for irrigation have weakened the flow of the river to the point the tidal bore has nearly disappeared.

South America

Lakes with tidal bores

Lakes with an ocean inlet can also exhibit tidal bores.[ citation needed ]

North America

See also

Related Research Articles

Garonne

The Garonne is a river in southwest France and northern Spain. It flows from the central Spanish Pyrenees to the Gironde estuary at the French port of Bordeaux. Its length is 529 km (329 mi), of which 47 km (29 mi) is in Spain ; this extends to 602 km (374 mi) if the Gironde estuary is included. Its basin area is 56,000 km2 (22,000 sq mi), which extends to 84,811 km2 (32,746 sq mi) if the Dordogne, which also flows into the Gironde estuary, is included.

Bay of Fundy Bay on the east coast of North America

The Bay of Fundy is a bay between the Canadian provinces of New Brunswick and Nova Scotia, with a small portion touching the US state of Maine. It has an extremely high tidal range. The name is likely a corruption of the French word Fendu, meaning "split".

Estuary Partially enclosed coastal body of brackish water with river stream flow, and with a free connection to the sea

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.

Hydraulic jump Phenomenon occurring when liquid at high velocity discharges into a zone of lower velocity

A hydraulic jump is a phenomenon in the science of hydraulics which is frequently observed in open channel flow such as rivers and spillways. When liquid at high velocity discharges into a zone of lower velocity, a rather abrupt rise occurs in the liquid surface. The rapidly flowing liquid is abruptly slowed and increases in height, converting some of the flow's initial kinetic energy into an increase in potential energy, with some energy irreversibly lost through turbulence to heat. In an open channel flow, this manifests as the fast flow rapidly slowing and piling up on top of itself similar to how a shockwave forms.

The Pororoca is a tidal bore, with waves up to 4 m (13 ft) high that travel as much as 800 km (500 mi) inland upstream on the Amazon River and adjacent rivers. Its name maybe comes from the indigenous Tupi language, where it could translate into "great roar". It could be also a Portuguese version of the term poroc-poroc, which in an indigenous' language was a way of expressing the act of destroying everything. It could be also a portmanteau of the words poroc and oca (house). It occurs at the mouth of the river where its waters meet the Atlantic Ocean.

Hangzhou Bay funnel-shaped inlet of East China Sea, bordered by the province Zhejiang and the municipality of Shanghai

Hangzhou Bay, or the Bay of Hangzhou, is a funnel-shaped inlet of the East China Sea, bordered by the province of Zhejiang and the municipality of Shanghai, which lies north of the Bay. The Bay extends from the East China Sea to its head at the city of Hangzhou, from which its name is derived.

Yaquina Bay

Yaquina Bay is a coastal estuarine community found in Newport, Oregon, United States. Yaquina Bay is a semi-enclosed body of water, approximately 8 km² (3.2 mi²) in area, with free connection to the Pacific Ocean, but also diluted with freshwater from the Yaquina River land drainage. The Bay is traversed by the Yaquina Bay Bridge. There are three small communities that border the Yaquina River and Bay; Newport, Toledo and Elk City. The Yaquina Bay in Newport is a popular tourist destination along the Pacific Coast Highway. It is also an important estuary for the ecology and economy of the area.

Couesnon

The Couesnon is a river running from the département of Mayenne in north-western France, forming an estuary at Mont Saint-Michel. It is 97.8 km (60.8 mi) long, and its drainage basin is 1,124 km2 (434 sq mi). Its final stretch forms the border between the historical duchies of Normandy and Brittany. Its historically irregular course, alternating between two beds on the north and south of the Mont Saint-Michel but eventually definitely settling to the south bed, inspired the saying "The Couesnon in its madness placed the Mont in Normandy", as the Mont is just to the Norman side of the river's current mouth. However, the administrative boundary separating the two regions does not depend on the course of the river, and is about six kilometers west of the Mont.

Podensac Commune in Nouvelle-Aquitaine, France

Podensac is a commune in the Gironde department. It is located in the famous Bordeaux wine region in Nouvelle-Aquitaine.

River surfing

River surfing is the sport of surfing either standing waves, tidal bores or upstream waves in rivers. Claims for its origins include a 1955 ride of 2.4 km (1.5 mi) along the tidal bore of the River Severn.

Hubert Chanson is a hydraulic engineering and applied fluid mechanics academic. Since 1990 he has worked at the University of Queensland.

Acoustic Doppler velocimetry (ADV) is designed to record instantaneous velocity components at a single-point with a relatively high frequency. Measurements are performed by measuring the velocity of particles in a remote sampling volume based upon the Doppler shift effect.

Tuross River river in New South Wales, Australia

The Tuross River, an open semi-mature wave dominated barrier estuary or perennial stream, is located in the South Coast region of New South Wales, Australia.

A mouth bar is an element of a deltaic system, which refers to typically mid-channel deposition of the sediment transported by the river channel at the river mouth.

Eprapah Creek is a sub-tropical stream located in Redland City close to Brisbane in South East Queensland, Australia.

Dordogne (river)

The Dordogne is a river in south-central and southwest France. It is 483.1 km (300.2 mi) long. The Dordogne and its watershed were designated Biosphere Reserve by UNESCO on July 11 2012.

Environmental flows can be broken down into instream flow, freshwater inflow, and outflow, as shown in the depiction below. Instream flow is the freshwater water flowing in rivers or streams. Freshwater inflow is the freshwater that flows into an estuary. Outflow is the flow from an estuary to the ocean. This article's focus is upon freshwater inflow.

Bec dAmbès

The Bec d'Ambès is the point of confluence of the rivers Garonne and Dordogne, in the Gironde estuary. Situated 15 miles north of Bordeaux, it has an oil refinery which was destroyed by bombing during World War II, but rebuilt after the war. It is in the Ambès commune.

Qiantang River East Chinese river

The Qiantang River or alternatively Tsientang River is a river in East China. An important commercial artery, it runs for 459 kilometers (285 mi) through Zhejiang, passing through the provincial capital Hangzhou before flowing into the East China Sea via Hangzhou Bay south of Shanghai. Its original name, the "Zhe River" or "Zhe Jiang", is the origin of the name of Zhejiang province. The river is also known, along with Hangzhou Bay, for having the world's largest tidal bore, a phenomenon where leading edge of the incoming tide forms a wave of water that travels up a river or narrow bay against the direction of the river or bay's current.

Hapua

Hapua is the Māori term for river-mouth lagoons on mixed sand and gravel (MSG) beaches which form at the river-coast interface where a typically braided, although sometimes meandering, river interacts with a coastal environment that is significantly affected by longshore drift. The lagoons which form on the MSG coastlines are common on the east coast of the South Island of New Zealand and have long been referred to as hapua by the Māori. This classification differentiates hapua from similar lagoons located on the New Zealand coast termed waituna. Hapua are often located on paraglacial coastal areas where there is a low level of coastal development and minimal population density. Hapua form as the river carves out an elongated coast-parallel area, blocked from the sea by a MSG barrier which constantly alters its shape and volume due to longshore drift. Longshore drift continually extends the barrier behind which the hapua forms by transporting sediment along the coast. Hapua are defined as a narrow shore-parallel extensions of the coastal riverbed. They discharge the majority of stored water to the ocean via an ephemeral and highly mobile drainage channel or outlet. The remainder percolates through the MSG barrier due to its high levels of permeability. Hapua systems are driven by a wide range of dynamic processes that are generally classified as fluvial or marine; changes in the balance between these processes as well as the antecedent barrier conditions can cause shifts in the morphology of the hapua, in particular the barrier. New Zealand examples include the Rakaia, Ashburton and Hurunui river-mouths.

References

  1. Sometimes also known as an aegir, eagre, or eygre in the context of specific instances in Britain.
  2. 1 2 3 4 5 Chanson, H. (2011). Tidal Bores, Aegir, Eagre, Mascaret, Pororoca. Theory and Observations. World Scientific, Singapore. ISBN   978-981-4335-41-6.
  3. Figure 5 in: Susan Bartsch-Winkler; David K. Lynch (1988), Catalog of worldwide tidal bore occurrences and characteristics (Circular 1022), U. S. Geological Survey
  4. Chanson, H. (2012). "Momentum considerations in hydraulic jumps and bores". Journal of Irrigation and Drainage Engineering. ASCE. 138 (4): 382–85. doi:10.1061/(ASCE)IR.1943-4774.0000409. ISSN   0372-0187.
  5. Chanson, H. (2009). "Current Knowledge In Hydraulic Jumps And Related Phenomena. A Survey of Experimental Results". European Journal of Mechanics B. 28 (2): 191–210. Bibcode:2009EJMF...28..191C. doi:10.1016/j.euromechflu.2008.06.004. ISSN   0997-7546.
  6. 1 2 3 Chanson, H. (2009). Environmental, Ecological and Cultural Impacts of Tidal Bores, Benaks, Bonos and Burros. Proc. International Workshop on Environmental Hydraulics IWEH09, Theoretical, Experimental and Computational Solutions, Valencia, Spain, 29–30 October Editor P.A. Lopez-Jimenez et al., Invited keynote lecture, 20 pp. (CD-ROM).
  7. Koch, C. and Chanson, H. (2008). "Turbulent Mixing beneath an Undular Bore Front". Journal of Coastal Research. 24 (4): 999–1007. doi:10.2112/06-0688.1. S2CID   130530635.CS1 maint: multiple names: authors list (link)
  8. Koch, C. and Chanson, H. (2009). "Turbulence Measurements in Positive Surges and Bores". Journal of Hydraulic Research. 47 (1): 29–40. doi:10.3826/jhr.2009.2954. S2CID   124743367.CS1 maint: multiple names: authors list (link)
  9. Chanson, H. (2009). "The Rumble Sound Generated by a Tidal Bore Event in the Baie du Mont Saint Michel". Journal of the Acoustical Society of America . 125 (6): 3561–68. Bibcode:2009ASAJ..125.3561C. doi:10.1121/1.3124781. PMID   19507938.
  10. 1 2 Simpson, J.H., Fisher, N.R., and Wiles, P. (2004). "Reynolds Stress and TKE Production in an Estuary with a Tidal Bore". Estuarine, Coastal and Shelf Science . 60 (4): 619–27. Bibcode:2004ECSS...60..619S. doi:10.1016/j.ecss.2004.03.006. during this […] deployment, the [ADCP] instrument was repeatedly buried in sediment after the 1st tidal cycle and had to be dug out of the sediment, with considerable difficulty, at the time of recovery.CS1 maint: multiple names: authors list (link)
  11. Chanson, H., Lubin, P., Simon, B., and Reungoat, D. (2010). Turbulence and Sediment Processes in the Tidal Bore of the Garonne River: First Observations. Hydraulic Model Report No. CH79/10, School of Civil Engineering, The University of Queensland, Brisbane, Australia, 97 pp. ISBN   978-1-74272-010-4.CS1 maint: multiple names: authors list (link)
  12. Simon, B., Lubin, P., Reungoat, D., Chanson, H. (2011). Turbulence Measurements in the Garonne River Tidal Bore: First Observations. Proc. 34th IAHR World Congress, Brisbane, Australia, 26 June–1 July, Engineers Australia Publication, Eric Valentine, Colin Apelt, James Ball, Hubert Chanson, Ron Cox, Rob Ettema, George Kuczera, Martin Lambert, Bruce Melville and Jane Sargison Editors, pp. 1141–48. ISBN   978-0-85825-868-6.CS1 maint: multiple names: authors list (link)
  13. Chanson, H., Reungoat, D., Simon, B., Lubin, P. (2012). "High-Frequency Turbulence and Suspended Sediment Concentration Measurements in the Garonne River Tidal Bore". Estuarine, Coastal and Shelf Science. 95 (2–3): 298–306. Bibcode:2011ECSS...95..298C. CiteSeerX   10.1.1.692.2537 . doi:10.1016/j.ecss.2011.09.012. ISSN   0272-7714.CS1 maint: multiple names: authors list (link)
  14. Reungoat, D., Chanson, H., Caplain, C. (2014). "Sediment Processes and Flow Reversal in the Undular Tidal Bore of the Garonne River (France)". Environmental Fluid Mechanics . 14 (3): 591–616. doi:10.1007/s10652-013-9319-y. ISSN   1567-7419. S2CID   14357850.CS1 maint: multiple names: authors list (link)
  15. Reungoat, D., Chanson, H., Keevil, C. (2014). Turbulence, Sedimentary Processes and Tidal Bore Collision in the Arcins Channel, Garonne River (October 2013). Hydraulic Model Report No. CH94/14, School of Civil Engineering, the University of Queensland, Brisbane, Australia, 145 Pp. ISBN   9781742721033.CS1 maint: multiple names: authors list (link)
  16. 1 2 Mouazé, D., Chanson, H., and Simon, B. (2010). Field Measurements in the Tidal Bore of the Sélune River in the Bay of Mont Saint Michel (September 2010). Hydraulic Model Report No. CH81/10, School of Civil Engineering, The University of Queensland, Brisbane, Australia, 72 pp. ISBN   978-1-74272-021-0. the field study experienced a number of problems and failures. About 40 s after the passage of the bore, the metallic frame started to move. The ADV support failed completely 10 minutes after the tidal bore.CS1 maint: multiple names: authors list (link)
  17. 1 2 Wolanski, E., Williams, D., Spagnol, S., and Chanson, H. (2004). "Undular Tidal Bore Dynamics in the Daly Estuary, Northern Australia". Estuarine, Coastal and Shelf Science. 60 (4): 629–36. Bibcode:2004ECSS...60..629W. doi:10.1016/j.ecss.2004.03.001. About 20 min after the passage of the bore the two aluminium frames at site C were toppled. […] A 3-min-duration patch of macroturbulence was observed. […] This unsteady motion was sufficiently energetic to topple moorings that had survived much higher, quasi-steady currents of 1.8 m/s.CS1 maint: multiple names: authors list (link)
  18. 1 2 Li, Ying; Pan, Dong-Zi; Chanson, Hubert; Pan, Cun-Hong (July 2019). "Real-time characteristics of tidal bore propagation in the Qiantang River Estuary, China, recorded by marine radar" (PDF). Continental Shelf Research. Elsevier. 180: 48–58. doi:10.1016/j.csr.2019.04.012. The Qiantang River tidal bore was recorded at two different geographical locations. Characteristic flow patterns were derived and analysed, including temporal changes over a relatively large-scale area. The experimental results showed that the radar-derived celerity and calculated height of the tidal bore were consistent with visual observations in this estuarine zone.
  19. 1 2 3 4 5 6 7 8 9 10 Chanson, H. (2008). Photographic Observations of Tidal Bores (Mascarets) in France. Hydraulic Model Report No. CH71/08, Univ. of Queensland, Australia, 104 pp. ISBN   978-1-86499-930-3.
  20. Ryan Novitra (February 3, 2017). "Riau to Introduce Bono Wave to International Tourism".
  21. (in French) definition of mascaret
  22. p. 159, Barrie R. Bolton. 2009. The Fly River, Papua New Guinea: Environmental Studies in an Impacted Tropical River System. Elsevier Science. ISBN   978-0444529640.
  23. Petitcodiac River changing faster than expected
  24. Natural History of Nova Scotia Vol. I, Chap. T "Ocean Currents", p. 109
  25. (in English) "Pororoca: surfing the Amazon" indicates that "The record that we could find for surfing the longest distance on the Pororoca was set by Picuruta Salazar, a Brazilian surfer who, in 2003, managed to ride the wave for 37 minutes and travel 12.5 kilometers (7.8 mi)."