Tidal race or tidal rapid is a natural occurrence whereby a fast-moving

tide Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another. Tide tables ...

passes through a constriction, resulting in the formation of

wave In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (re ...

s, eddies and hazardous

currents Currents, Current or The Current may refer to: Science and technology * Current (fluid), the flow of a liquid or a gas ** Air current, a flow of air ** Ocean current, a current in the ocean *** Rip current, a kind of water current ** Current (stre ...

. The constriction can be a passage where the sides narrow, for example the

Gulf of Corryvreckan The Gulf of Corryvreckan (from the Gaelic ''Coire Bhreacain'', meaning 'cauldron of the speckled seas' or 'cauldron of the plaid'), also called the Strait of Corryvreckan, is a narrow strait between the islands of Jura and Scarba, in Argyll and ...

and the

Saltstraumen Saltstraumen is a small strait with one of the strongest tidal currents in the world. It is located in the municipality of Bodø in Nordland county, Norway. It is located about southeast of the town of Bodø. The narrow channel connects the ou ...

maelstrom, or an underwater obstruction (a

reef A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic processes— deposition of sand, wave erosion planing down rock o ...

or rising

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

), such as is found at the Portland Race in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...

. In extreme cases, such as

Skookumchuck Narrows Skookumchuck Narrows is a strait forming the entrance of Sechelt Inlet on British Columbia's Sunshine Coast in Canada. Before broadening into Sechelt Inlet, all of its tidal flow together with that of Salmon Inlet and Narrows Inlet must pa ...

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

, through which tides can travel at more than 17 knots, very large

whirlpool A whirlpool is a body of rotating water produced by opposing currents or a current running into an obstacle. Small whirlpools form when a bath or a sink is draining. More powerful ones formed in seas or oceans may be called maelstroms ( ). ''Vo ...

s develop, which can be extremely hazardous to navigation.

Notable tidal races

Cape Reinga , type =Cape , photo = Cape Reinga, Northland, New Zealand, October 2007.jpg , photo_width = 270px , photo_alt = , photo_caption = , map = New Zealand , map_width = 270px ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

* The Bitches in

Wales Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...

Bitches and Tides
*

Falls of Lora The Falls of Lora is a tidal race which forms at the mouth of Loch Etive when a particularly high tide runs out from the loch. They form white water rapids for two to five days either side of the spring tides.Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...

, United Kingdom * Portland Bill on the

Isle of Portland An isle is an island, land surrounded by water. The term is very common in British English British English (BrE, en-GB, or BE) is, according to Lexico, Oxford Dictionaries, "English language, English as used in Great Britain, as distinct fr ...

, United Kingdom * The Alderney Race (12 knots+) on Alderney * Horizontal Falls in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

, Australia *

Naruto Strait is a strait between Awaji Island and Shikoku in Japan. It connects Harima Nada, the eastern part of the Inland Sea and the Kii Channel. A famous feature of the strait is the Naruto whirlpools. Ōnaruto Bridge, the southern part of the Kobe-A ...

between

Shikoku is the smallest of the four main islands of Japan. It is long and between wide. It has a population of 3.8 million (, 3.1%). It is south of Honshu and northeast of Kyushu. Shikoku's ancient names include ''Iyo-no-futana-shima'' (), '' ...

and Awaji Islands, Japan * Reversing Falls in

Saint John, New Brunswick Saint John is a seaport city of the Atlantic Ocean located on the Bay of Fundy in the province of New Brunswick, Canada. Saint John is the oldest incorporated city in Canada, established by royal charter on May 18, 1785, during the reign of K ...

, Canada

Sources

{{DEFAULTSORT:Tidal Race Tides Whirlpools

Notable tidal races

See also

Sources