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, engineering, and related fields, a wave is a propagating dynamic disturbance (change from List of types of equilibrium, equilibrium) of one or more quantities. ''Periodic waves'' oscillate repeatedly about an equilibrium ...

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 (hy ...

. The constriction can be a passage where the sides narrow, for example the Gulf of Corryvreckan and the

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

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 component, abiotic (non-living) processes such as deposition (geol ...

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 Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

. In extreme cases, such as Skookumchuck Narrows in

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

, through which tides can travel at more than 17

knots A knot is a fastening in rope or interwoven lines. Knot or knots may also refer to: Other common meanings * Knot (unit), of speed * Knot (wood), a timber imperfection Arts, entertainment, and media Films * ''Knots'' (film), a 2004 film * ''Kn ...

(31.484 km/h), 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 Cape Reinga / Te Rerenga Wairua (; sometimes spelled Rēinga, ) is the northwestern most tip of the Aupōuri Peninsula, at the northern end of the North Island of New Zealand. Cape Reinga is more than 100 km north of the nearest small town ...

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

* Skookumchuck Narrows in

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

* The Bitches in

Wales Wales ( ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by the Irish Sea to the north and west, England to the England–Wales border, east, the Bristol Channel to the south, and the Celtic ...

Bitches and Tides
* Falls of Lora in

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

, United Kingdom * Portland Bill on the

Isle of Portland The Isle of Portland is a tied island, long by wide, in the English Channel. The southern tip, Portland Bill, lies south of the resort of Weymouth, Dorset, Weymouth, forming the southernmost point of the county of Dorset, England. A barrier ...

, United Kingdom * The

Alderney Race The Alderney Race is a strait that runs between Alderney and Cap de la Hague, a cape at the northwestern tip of the Cotentin Peninsula in Normandy. A strong current runs through the race north of the Passage de la Déroute, a treacherous passage s ...

(12 knots+) between

Alderney Alderney ( ; ; ) is the northernmost of the inhabited Channel Islands. It is part of the Bailiwick of Guernsey, a British Crown Dependencies, Crown dependency. It is long and wide. The island's area is , making it the third-largest isla ...

and

La Hague La Hague () is a commune in the department of Manche, northwestern France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Gui ...

Normandy Normandy (; or ) is a geographical and cultural region in northwestern Europe, roughly coextensive with the historical Duchy of Normandy. Normandy comprises Normandy (administrative region), mainland Normandy (a part of France) and insular N ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

* The Raz de Sein in western

Brittany Brittany ( ) is a peninsula, historical country and cultural area in the north-west of modern France, covering the western part of what was known as Armorica in Roman Gaul. It became an Kingdom of Brittany, independent kingdom and then a Duch ...

, France * The Fromveur Passage in western Brittany, France * Horizontal Falls in

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

* Naruto Strait between

Shikoku is the smallest of the List of islands of Japan#Main islands, four main islands of Japan. It is long and between at its widest. It has a population of 3.8 million, the least populated of Japan's four main islands. It is south of Honshu ...

and Awaji Islands,

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

* Reversing Falls in

Saint John, New Brunswick Saint John () is a port#seaport, seaport city located on the Bay of Fundy in the province of New Brunswick, Canada. It is Canada's oldest Municipal corporation, incorporated city, established by royal charter on May 18, 1785, during the reign ...

, Canada

Sources

{{DEFAULTSORT:Tidal Race Tides Whirlpools

Notable tidal races

See also

Sources