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Head Of Navigation
The head of navigation is the farthest point above the mouth of a river that can be navigated by ships. Determining the head of navigation can be subjective on many streams, as the point may vary greatly with the size or the draft of the ship being contemplated for navigation and the seasonal water level. On others, it is quite objective, being caused by a waterfall, a low bridge that is not a drawbridge, or a dam without navigation locks. Several rivers in a region may have their heads of navigation along a line called the fall line. Longer rivers such as the River Thames may have several heads of navigation depending on boat size. In the case of the Thames, that includes London Bridge, which historically served as the head of navigation for tall ships; Osney Bridge in Oxford, which has the lowest headroom of any bridge on the Thames that generally restricts navigation to smaller vessels such as narrowboats and cabin cruisers, and the long reach above St John's Lock ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Mouth
A river mouth is where a river flows into a larger body of water, such as another river, a lake/reservoir, a bay/ gulf, a sea, or an ocean. At the river mouth, sediments are often deposited due to the slowing of the current reducing the carrying capacity of the water. The water from a river can enter the receiving body in a variety of different ways. The motion of a river is influenced by the relative density of the river compared to the receiving water, the rotation of the earth, and any ambient motion in the receiving water, such as tides or seiches. If the river water has a higher density than the surface of the receiving water, the river water will plunge below the surface. The river water will then either form an underflow or an interflow within the lake. However, if the river water is lighter than the receiving water, as is typically the case when fresh river water flows into the sea, the river water will float along the surface of the receiving water as an overflow. Al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ships
A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished from boats, based on size, shape, load capacity, and purpose. Ships have supported exploration, trade, warfare, migration, colonization, and science. After the 15th century, new crops that had come from and to the Americas via the European seafarers significantly contributed to world population growth. Ship transport is responsible for the largest portion of world commerce. The word ''ship'' has meant, depending on the era and the context, either just a large vessel or specifically a ship-rigged sailing ship with three or more masts, each of which is square-rigged. As of 2016, there were more than 49,000 merchant ships, totaling almost 1.8 billion dead weight tons. Of these 28% were oil tankers, 43% were bulk carriers, and 13% were c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Draft (hull)
The draft or draught of a ship's hull is the vertical distance between the waterline and the bottom of the hull ( keel). The draught of the vessel is the maximum depth of any part of the vessel, including appendages such as rudders, propellers and drop keels if deployed. Draft determines the minimum depth of water a ship or boat can safely navigate. The related term air draft is the maximum height of any part of the vessel above the water. The more heavily a vessel is loaded, the deeper it sinks into the water, and the greater its draft. After construction, the shipyard creates a table showing how much water the vessel displaces based on its draft and the density of the water (salt or fresh). The draft can also be used to determine the weight of cargo on board by calculating the total displacement of water, accounting for the content of the ship's bunkers, and using Archimedes' principle. The closely related term "trim" is defined as the difference between the forward and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Waterfall
A waterfall is a point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls can be formed in several ways, but the most common method of formation is that a river courses over a top layer of resistant bedrock before falling on to softer rock, which erodes faster, leading to an increasingly high fall. Waterfalls have been studied for their impact on species living in and around them. Humans have had a distinct relationship with waterfalls for years, travelling to see them, exploring and naming them. They can present formidable barriers to navigation along rivers. Waterfalls are religious sites in many cultures. Since the 18th century they have received increased attention as tourist destinations, sources of hydropower, andparticularly since the mid-20th centuryas subjects of research. Definition and terminology A waterfall is general ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Drawbridge
A drawbridge or draw-bridge is a type of moveable bridge typically at the entrance to a castle or tower surrounded by a moat. In some forms of English, including American English, the word ''drawbridge'' commonly refers to all types of moveable bridges, such as bascule bridges, vertical-lift bridges and swing bridges, but this article concerns the narrower historical definition of the term where the bridge is used in a defensive structure. As used in castles or defensive structures, drawbridges provide access across defensive structures when lowered, but can quickly be raised from within to deny entry to an enemy force. Castle drawbridges Medieval castles were usually defended by a ditch or moat, crossed by a wooden bridge. In early castles the bridge might be designed to be destroyed or removed in the event of an attack, but drawbridges became very common. A typical arrangement would have the drawbridge immediately outside a gatehouse, consisting of a wooden deck with one ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canal Lock
A lock is a device used for raising and lowering boats, ships and other watercraft between stretches of water of different levels on river and canal waterways. The distinguishing feature of a lock is a fixed chamber in which the water level can be varied; whereas in a caisson lock, a boat lift, or on a canal inclined plane, it is the chamber itself (usually then called a caisson) that rises and falls. Locks are used to make a river more easily navigable, or to allow a canal to cross land that is not level. Later canals used more and larger locks to allow a more direct route to be taken. Pound lock A ''pound lock'' is most commonly used on canals and rivers today. A pound lock has a chamber with gates at both ends that control the level of water in the pound. In contrast, an earlier design with a single gate was known as a flash lock. Pound locks were first used in China during the Song Dynasty (960–1279 AD), having been pioneered by the Song politician and naval ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fall Line
A fall line (or fall zone) is the area where an upland region and a coastal plain meet and is typically prominent where rivers cross it, with resulting rapids or waterfalls. The uplands are relatively hard crystalline basement rock, and the coastal plain is softer sedimentary rock. A fall line often will recede upstream as the river cuts out the uphill dense material, forming "c"-shaped waterfalls and exposing bedrock shoals. Because of these features, riverboats typically cannot travel any farther inland without portaging, unless locks are built. The rapid change in elevation of the water and resulting energy release make the fall line a good location for water mills, grist mills, and sawmills. Seeking a head of navigation with a ready supply of water power, people have long made settlements where rivers cross a fall line. Geography The slope of fall zones on rivers played a role in settlement patterns. For example, the fall line represents the inland limit of navigation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River Thames
The River Thames ( ), known alternatively in parts as the River Isis, is a river that flows through southern England including London. At , it is the longest river entirely in England and the second-longest in the United Kingdom, after the River Severn. The river rises at Thames Head in Gloucestershire, and flows into the North Sea near Tilbury, Essex and Gravesend, Kent, via the Thames Estuary. From the west it flows through Oxford (where it is sometimes called the Isis), Reading, Henley-on-Thames and Windsor. The Thames also drains the whole of Greater London. In August 2022, the source of the river moved five miles to beyond Somerford Keynes due to the heatwave in July 2022. The lower reaches of the river are called the Tideway, derived from its long tidal reach up to Teddington Lock. Its tidal section includes most of its London stretch and has a rise and fall of . From Oxford to the Estuary the Thames drops by 55 metres. Running through some of the drier ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
London Bridge
Several bridges named London Bridge have spanned the River Thames between the City of London and Southwark, in central London. The current crossing, which opened to traffic in 1973, is a box girder bridge built from concrete and steel. It replaced a 19th-century stone-arched bridge, which in turn superseded a 600-year-old stone-built medieval structure. This was preceded by a succession of timber bridges, the first of which was built by the Roman Empire, Roman founders of London. The current bridge stands at the western end of the Pool of London and is positioned upstream from previous alignments. The approaches to the medieval bridge were marked by the church of St Magnus-the-Martyr on the northern bank and by Southwark Cathedral on the southern shore. Until Putney Bridge opened in 1729, London Bridge was the only road crossing of the Thames downstream of Kingston upon Thames. London Bridge has been depicted in its several forms, in art, literature, and songs, including the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Osney Bridge
Osney Bridge is a road bridge across the River Thames in Oxford, England, built in 1888 to replace a stone bridge which collapsed in 1885. It carries the Botley Road ( A420) from Botley into Oxford. The Thames Path crosses the river on this bridge, just above Osney Lock. The original bridge was probably built by the monks of Osney Abbey, to carry the main road across the millstream of Osney Mill west of the island then known as Osney. By the early 17th century it was a three-arch stone construction. In 1790 the millstream became the main navigation channel of the river, and the bridge had become a serious obstruction to navigation by the mid 19th century. In 1885 the central arch collapsed, leaving massive piers. Proposals to raise Osney Bridge Osney Bridge has the lowest headroom (less than 7 feet 6 inches, or 2.3 metres) of any bridge across the navigable Thames; this limits the size of boats that can travel past it without having to be removed from the water and replaced ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxford
Oxford () is a city in England. It is the county town and only city of Oxfordshire. In 2020, its population was estimated at 151,584. It is north-west of London, south-east of Birmingham and north-east of Bristol. The city is home to the University of Oxford, the List of oldest universities in continuous operation, oldest university in the English-speaking world; it has buildings in every style of Architecture of England, English architecture since late History of Anglo-Saxon England, Anglo-Saxon. Oxford's industries include motor manufacturing, education, publishing, information technology and science. History The history of Oxford in England dates back to its original settlement in the History of Anglo-Saxon England, Saxon period. Originally of strategic significance due to its controlling location on the upper reaches of the River Thames at its junction with the River Cherwell, the town grew in national importance during the early Norman dynasty, Norman period, and in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Narrowboat
A narrowboat is a particular type of canal boat, built to fit the narrow locks of the United Kingdom. The UK's canal system provided a nationwide transport network during the Industrial Revolution, but with the advent of the railways, commercial canal traffic gradually diminished and the last regular long-distance transportation of goods by canal had virtually disappeared by 1970. However, some commercial traffic continued. From the 1970s onward narrowboats were gradually being converted into permanent residences or as holiday lettings. Currently, about 8580 narrowboats are registered as 'permanent homes' on Britain's waterway system and represent a growing alternative community living on semi-permanent moorings or continuously cruising. For any boat to enter a narrow lock, it must be under wide, so most narrowboats are nominally wide. A narrowboat's maximum length is generally , as anything longer will be unable to navigate much of the British canal network, because the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
_by_Claes_Van_Visscher.jpg "Click for more on -> London Bridge")
