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Tidal Bore

Last updated date: 16th Apr 2024
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River Bore

A tidal bore, also known as the bore is a tidal phenomenon in which the highest incoming tides form a wave (or waves) of water that travels up a river or confined bay against the path of the river or bay’s current.  The word “bore”  is derived through Old English from the Old Norse word Bara meaning “ wave” or “swell”.

A bore occurs in some places worldwide, generally in areas with larger tidal range and where incoming tides are passed into a shallow narrowing of a river of the lake through a broad bay. 

The funnel-like shape not only increases the tidal range but also decreases the duration of the flood tide where the flood appears as an immediate increase in a water level. A tidal bore always occurs during the flood tide and never occurs during an ebb tide. 

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Qiantang River Tidal Bore

Qiantang River tidal bore, also known as the silver dragon tidal bore, is the world’s largest tidal bore. It is a river in east china and runs from Hangzhou bay on China’s eastern coast. The Qiantang River tidal bore is a famous scenic spot of the Qiantang River.

Generally around  August 15, the Lunar calendar is the best time to observe the silver dragon tidal bores. Driving this time, this largest tidal bore can be several meters. Before the sea tide appeared, a white ting dot appeared in the distance, which transformed into a silver thread in a blink of an eye. Later, the white line rolled to the sea as it was accompanied by waves of dull thunder. 

In ancient Hangzhou, Phoenix mountain, the Jianggan area was the best place to watch the Qiantang River tidal bore. Due to the transformation of geographical location from the Ming dynasty, Haining, Hanguan was the first resort to observe the silver dragon tidal bore,  so it was also called "Haining Tidal Bore".

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Petitcodiac River Tidal Bore

The Petitcodiac River tidal bore - retrograde wave moving upstream over the downstream wavers. It occurs twice a day and comes from the world’s largest tide in the Bay of fundy. The first European mention of the Petitcodiac river tidal bore by the British Lieutenant Colonel George Scott on 17 November 1758.

The Petitcodiac River tidal bore ranges from 1 to 2 m (3.3 - 6.6 ft) in height, with a speed from 5 to 15 km/h. Peter Fisher in 1825, observed that the noise of the bore is heard at a great distance, and animals instantly take to the highland and manifest visible signs of terror if near it. Before the causeway, the value of the Petitcodiac river tidal bore was compared with the tidal bores of Qiantang, Hooghly, and Amazon river. The bore reached heights from about 5 to 75 cm after the causeway was built.

Bay of Fundy Tidal Bore

The Bay of Fundy tidal bore is the bay found between the Canadian province or territories of New Brunswick and Nova Scotia, with a small part touching the US state of Maine. The bay of fundy tidal bore has an extremely high tidal range. The name is derived from the French word Fendu meaning “split”.

The tidal range in the Bay of Fundyis around 16 m ( 52 ft). Some tides are higher than others, depending on the position of the moon, the sun, and other atmospheric conditions. Tides in the Bay of Fundy are semi-annual, meaning they have two highs and two lows on each day with about 6 hours and 13 minutes between each high and low tides.

As per the Guinness Book of World records, the World’s highest tides are found in the Bay of Fundy, where the mean spring range in the Minas basin is 14.5 meters (47.6 feet). The largest tide on record in the Bay was 21.6 meters ( 70.9 ft) in 1869.

Pororoca Surfing 

The Pororoca is a tidal bore, with waves up to 4 m (13 ft) high that travels as much as 800 km ( 500 mi) inland upstream on the Amazon river and other adjacent rivers. The word “ porocca” is driven from the indigenous tulip language where it could translate into “great roar”. The Pororoca tidal bores occur at the mouth of the river where its water meets the Atlantic ocean.

The Pororoca river waves have become popular with surfers. However, pororoca surfing is especially dangerous as water contains a significant amount of debris from the shores of the river ( often entire trees) along with the dangerous fauna.

Did You Know?

  • Tidal bore can occur every day, like the tidal bore of the Batang River in Malaysia, known as benak.

  • Tidal bore, like the porocca, occurs during spring tides.

  • The bore is the fastest and highest in some of the small rivers like Salmon River in Truro, the St. Croix and Kennetcook river in the Minas Basin, and the Maccan river and River Hebert in the Cumberland basin.

  • The second highest tides in the World is Severn Estuary-after the Bay of Fundy in Canada and the highest in Europe.

  • There are around 60 tidal bores around the Globe.

  • The World's highest tidal bore occurs along the Qiantang River in Hangzhou,China, where tides reach upto 30 feet and travel at upto 40 kilometers per hour.

FAQs on Tidal Bore

Q1. What are the Benefits of Tidal Bores?

Ans. Some of the benefits of the tidal bore are as follows:

  • Tidal bore surfing promotes ecotourism.

  • Tidal bores prevent water stagnation at the rivers and wash away debris at the side of the river bank. Hence, it has a role to frequently destroy breeding grounds for vectors like mosquitoes.

  • Tidal bore intense bore formation has the power to crush material, stir, and mix organic matters, create excellent aeration and wash nutrients upstream from the sea towards the deep inland.

Q2. What are the Effects of the Tidal Bore?

Ans. The effects of tidal bore include:

  • The tidal bore is known to destroy ships and docks along the river banks.

  • Loss of life in place is common with massive destructive tidal bores.

  • Soil erosion is common along with the areas of tidal bores. Trees are seen uprooted by the tidal bores.

  • Tidal bores affect the shipping and navigation in an estuarine zone.

Q3. What are the Best Tidal Bores for Surfing?

Ans. The Best Tidal Bores for Surfing are:

  • The Bono (Kampar River, Samata)

  • The Porocca (The Amazon, Brazil)

  • Seven Dragon (Qiantang River, China)

  • Bay of Fundy (Qiantang River)

  • The Severn Bore (The Severn River, Bristol)

  • Turnagain Arm (Turnagain Arm, Alaska)

  • The Baan (Hooghly River, Kolkata, India)