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Tidal race or tidal rapid is a natural occurrence whereby a fast-moving tide passes through a constriction, resulting in the formation of waves, eddies and hazardous currents. The constriction can be a passage where the sides narrow, for example the Gulf of Corryvreckan and the Saltstraumen maelstrom, or an underwater obstruction (a reef or rising seabed), such as is found at the Portland Race in the United Kingdom.
In extreme cases, such as Skookumchuck Narrows in British Columbia, through which tides can travel at more than 17 knots, very large whirlpools develop, which can be extremely hazardous to navigation.
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of the Earth.
A rip tide, or riptide, is a strong, offshore current that is caused by the tide pulling water through an inlet along a barrier beach, at a lagoon or inland marina where tide water flows steadily out to sea during ebb tide. It is a strong tidal flow of water within estuaries and other enclosed tidal areas. The riptides become the strongest where the flow is constricted. When there is a falling or ebbing tide, the outflow water is strongly flowing through an inlet toward the sea, especially once stabilized by jetties. During these falling and ebbing tides, a riptide can carry a person far offshore. For example, the ebbing tide at Shinnecock Inlet in Southampton, New York, extends more than 300 metres (980 ft) offshore. Because of this, riptides are typically more powerful than rip currents.
The Menai Strait is a narrow stretch of shallow tidal water about 25 km (16 mi) long, which separates the island of Anglesey from the mainland of Wales.
Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.
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 in seas or oceans may be termed maelstroms. Vortex is the proper term for a whirlpool that has a downdraft.
An inlet is an indentation of a shoreline, usually long and narrow, such as a small bay or arm, that often leads to an enclosed body of salt water, such as a sound, bay, lagoon, or marsh.
A tidal bore, often simply given as bore in context, is a tidal phenomenon in which the 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.
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 10 kilometres (6.2 mi) southeast of the town of Bodø. The narrow channel connects the outer Saltfjorden to the large Skjerstad Fjord between the islands of Straumøya and Knaplundsøya. The Saltstraumen Bridge on Norwegian County Road 17 crosses Saltstraumen.
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 pass through Sechelt Rapids. At peak flows, standing waves, whitecaps, and whirlpools form at the rapids even in calm weather. The narrows are also the site of Skookumchuck Narrows Provincial Park.
The Columbia Bar, also frequently called the Columbia River Bar, is a system of bars and shoals at the mouth of the Columbia River spanning the U.S. states of Oregon and Washington. The bar is about 3 miles (5 km) wide and 6 miles (10 km) long.
Sechelt Inlet formerly Seechelt Inlet is one of the principal inlets of the British Columbia Coast. The inlet is significant in that it almost makes an island of what is instead the Sechelt Peninsula, whose isthmus is at the town of Sechelt at the head of the inlet. The isthmus is less than 1.2 km (0.75 mi) in distance. Sechelt Inlet's mouth is at Jervis Inlet, inland from the Malaspina Strait.
Skookumchuck is a Chinook Jargon term that is in common use in British Columbia English and occurs in Pacific Northwest English. Skookum means "strong" or "powerful", and "chuck" means water, so skookumchuck means "rapids" or "whitewater", or fresh, healthy water. It can mean any rapids, but in coastal usage refers to the powerful tidal rapids at the mouths of most of the major coastal inlets.
Seymour Narrows is a 5-kilometre (3.1 mi) section of the Discovery Passage in British Columbia known for strong tidal currents. Discovery Passage lies between Vancouver Island at Menzies Bay, British Columbia and Quadra Island except at its northern end where the eastern shoreline is Sonora Island. The section known as Seymour Narrows begins about 18 km (11 mi) from the south end of Discovery Passage where it enters the Georgia Strait near Campbell River. For most of the length of the narrows, the channel is about 750 metres (820 yd) wide. Through this narrow channel, currents can reach 15 knots.
The Narrows is a strait in New York City separating Brooklyn and Staten Island.
In kayaking, a playspot is a place where there are favorable stationary features on rivers, in particular standing waves, 'holes' and 'stoppers', where water flows back on itself creating a retentive feature, or eddy lines.
Quatsino Sound is a complex of coastal inlets, bays and islands on northwestern Vancouver Island in the Canadian province of British Columbia. It is the northernmost of the five sounds that pierce the west coast of Vancouver Island, the others being Kyuquot Sound, Nootka Sound, Clayoquot Sound, and Barkley Sound.
New Zealand has large ocean energy resources but does not yet generate any power from them. TVNZ reported in 2007 that over 20 wave and tidal power projects are currently under development. However, not a lot of public information is available about these projects. The Aotearoa Wave and Tidal Energy Association was established in 2006 to "promote the uptake of marine energy in New Zealand". According to their 10 February 2008 newsletter, they have 59 members. However, the association doesn't list its members.
Nitinat Lake is a large lake and inlet on the southwestern coast of Vancouver Island, British Columbia, Canada. The lake is about 150 km (93 mi) northwest by road from Victoria, BC's capital on the southern tip of Vancouver Island, and about 60 km (37 mi) southwest by road from the town of Lake Cowichan. The town of Port Alberni is about 80 km (50 mi) by road to the north.
A tidal stream generator, often referred to as a tidal energy converter (TEC), is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy from run of river or tidal estuarine sites. Certain types of these machines function very much like underwater wind turbines, and are thus often referred to as tidal turbines. They were first conceived in the 1970s during the oil crisis.
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 separating the Cotentin from the Channel Islands. The current is intermittent, varying with the tide, and can run up to about 12 knots (22 km/h) during equinoctial tides. The French call it Raz Blanchard. In Norman French it is called L'Raz.