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.[1] They form white water rapids for two to five days either side of the spring tides.[2]
The falls of Lora are generated when the water level in the Firth of Lorn (i.e. the open sea) drops below the level of the water in Loch Etive as the tide goes out. As the seawater in Loch Etive pours out through the narrow mouth of the loch, it passes over a rocky shelf which causes the rapids to form. As the tide rises again there is a period of slack water when the levels are the same on either side. However, due to the narrow entrance to the Loch, the tide rises more quickly than the water can flow into the Loch. Thus there is still considerable turbulence at high tide caused by flow into the Loch. Thus, unlike most situations where slack water is at high and low tides, in the case of the Falls of Lora slack water occurs when the levels on either side are the same, not when the tidal change is at its least. As a result, the tidal range is much greater on the coast than it is inside the loch. A 3 metres (9.8ft) range at Oban may produce only a 1.3 metres (4.3ft) range at Bonawe on the loch shore.[2]
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.
The River Avon is an English river in the south west of the country. To distinguish it from a number of other rivers of the same name, this river is often also known as the Bristol Avon. The name ‘Avon’ is a cognate of the Welsh word afon, ‘river’.
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. It varies in width from 400 metres (1,300 ft) from Fort Belan to Abermenai Point to 1,100 metres (3,600 ft) from Traeth Gwyllt to Caernarfon Castle. It then narrows to 500 metres (1,600 ft) in the middle reaches and then it broadens again. At Bangor, Garth Pier, it is 900 metres (3,000 ft) wide. It then widens out, and the distance from Puffin Island to Penmaenmawr is about 8 kilometres (5.0 mi).
The Reversing Falls are a series of rapids on the Saint John River located in Saint John, New Brunswick, Canada, where the river runs through a narrow gorge before emptying into the Bay of Fundy.
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, such as is found at the Portland Race in the United Kingdom.
Slack water is a short period in a body of tidal water when the water is completely unstressed, and there is no movement either way in the tidal stream, and which occurs before the direction of the tidal stream reverses. Slack water can be estimated using a tidal atlas or the tidal diamond information on a nautical chart. The time of slack water, particularly in constricted waters, does not occur at high and low water, and in certain areas, such as Primera Angostura, the ebb may run for up to three hours after the water level has started to rise. Similarly, the flood may run for up to three hours after the water has started to fall. In 1884, Thornton Lecky illustrated the phenomenon with an inland basin of infinite size, connected to the sea by a narrow mouth. Since the level of the basin is always at mean sea level, the flood in the mouth starts at half tide, and its velocity is at its greatest at the time of high water, with the strongest ebb occurring conversely at low water.
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.
Loch Etive is a 30 km sea loch in Argyll and Bute, Scotland. It reaches the sea at Connel, 5 km north of Oban. It measures 31.6 km long and from 1.2 km to 1.6 km (1 mi) wide. Its depth varies greatly, up to a maximum of 150 m (490 ft).
Glen Etive is a glen in the Highlands of Scotland. The River Etive rises on the peaks surrounding Rannoch Moor, with several tributary streams coming together at the Kings House Hotel, at the head of Glen Coe. From the Kings House, the Etive flows for about 18 km, reaching the sea loch, Loch Etive. The river and its tributaries are popular with whitewater kayakers and at high water levels it is a test piece of the area and a classic run.
Tidal range is the height difference between high tide and low tide. Tides are the rise and fall of sea levels caused by gravitational forces exerted by the Moon and Sun and the rotation of Earth. Tidal range is not constant but changes depending on the locations of the Moon and Sun.
Connel is a village in Argyll and Bute, Scotland. It is situated on the southern shore of Loch Etive. The Lusragan Burn flows through the village and into the loch.
Taynuilt is a large village in Argyll and Bute, Scotland located at the western entrance to the narrow Pass of Brander.
Connel Bridge is a cantilever bridge that spans Loch Etive at Connel in Scotland. The bridge takes the A828 road across the narrowest part of the loch, at the Falls of Lora. It is a category B listed structure.
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.
The Malibu Rapids forms the entrance to Princess Louisa Inlet and is also connected to the Jervis Inlet. The tidal flow of both inlets pass through this narrow and shallow passage that creates a fast moving and strong tidal rapids during the peak flows. At slack tide, the entrance is virtually flat calm similar to the Skookumchuck Narrows near the entrance of the Jervis Inlet.
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.
A tidal barrage is a dam-like structure used to capture the energy from masses of water moving in and out of a bay or river due to tidal forces.
The River Orchy is a river that passes through the village of Dalmally, Argyll in the West Highlands of Scotland. It rises in the Black Mount Forest, and flows southerly, passing through Loch Tulla and Glen Orchy before reaching Loch Awe. The hills of Beinn Mhic-Mhonaidh, Beinn Udlaidh and Beinn Bhreac-liath are to the north and south; there are falls and islands within the river. Reachable by the A82 road, tourists partake in kayaking, whitewater rafting, and fishing. Recent gold mining exploration has occurred in one of the river's glens just outside the Loch Lomond and The Trossachs National Park.
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.
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