Misplaced Pages

#705294

104-605: The Oxford-Burcot Commission was the first commission concerned with the management of the River Thames , appointed by an act of Parliament , the Thames Commission of Sewers Act 1605 ( 3 Jas. 1 . c. 14) to make the stretch of river from Burcot to Oxford navigable . The commission took responsibility for the management of the River Thames between Oxford and Burcot . It consisted of 18 members, including

208-740: A flash lock . Pound locks were first used in China during the Song dynasty (960–1279 CE), having been pioneered by the Song politician and naval engineer Qiao Weiyue in 984. They replaced earlier double slipways that had caused trouble and are mentioned by the Chinese polymath Shen Kuo (1031–1095) in his book Dream Pool Essays (published in 1088), and fully described in the Chinese historical text Song Shi (compiled in 1345): The distance between

312-404: 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. 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

416-528: A broad canal for more than one boat to be in a staircase at the same time, but managing this without waste of water requires expertise. On English canals, a staircase of more than two chambers is usually staffed: the lockkeepers at Bingley (looking after both the "5-rise" and the "3-rise") ensure that there are no untoward events and that boats are moved through as speedily and efficiently as possible. Such expertise permits miracles of boat balletics: boats travelling in opposite directions can pass each other halfway up

520-426: A flight of locks is simply a series of locks in close-enough proximity to be identified as a single group. For many reasons, a flight of locks is preferable to the same number of locks spread more widely: crews are put ashore and picked up once, rather than multiple times; transition involves a concentrated burst of effort, rather than a continually interrupted journey; a lock keeper may be stationed to help crews through

624-594: A large part of south-eastern and a small part of western England; the river is fed by at least 50 named tributaries . The river contains over 80 islands . With its waters varying from freshwater to almost seawater, the Thames supports a variety of wildlife and has a number of adjoining Sites of Special Scientific Interest , with the largest being in the North Kent Marshes and covering 20.4 sq mi (5,289 ha). According to Mallory and Adams,

728-480: A lock is simple. For instance, if a boat travelling downstream finds the lock already full of water: If the lock were empty, the boat would have had to wait 5 to 10 minutes while the lock was filled. For a boat travelling upstream, the process is reversed; the boat enters the empty lock, and then the chamber is filled by opening a valve that allows water to enter the chamber from the upper level. The whole operation will usually take between 10 and 20 minutes, depending on

832-537: A lock, and the position of the forward edge of the cill is usually marked on the lock side by a white line. The edge of the cill is usually curved, protruding less in the center than at the edges. In some locks, there is a piece of oak about 9 in (23 cm) thick which protects the solid part of the lock cill. On the Oxford Canal it is called a babbie; on the Grand Union Canal it is referred to as

936-508: A network of creeks. Lying below sea level, it is prone to flooding at exceptional tides, but has nevertheless been inhabited since Roman times. The usually quoted source of the Thames is at Thames Head (at grid reference ST980994 ). This is about 1.5 mi (2.4 km) north of the village of Kemble in southern Gloucestershire , near the town of Cirencester , in the Cotswolds . However, Seven Springs near Cheltenham , where

1040-609: A representative each from Oxford city and from the University . However its work was irregular and by 1611 it had ceased altogether. A second strengthened act of Parliament in 1624, the Thames Navigation Act 1623 ( 21 Jas. 1 . c. 32), allowed for the appointment of eight commissioners of sewers . This was also known as the Oxford-Burcot Commission . It had the power to tax Oxford city and

1144-480: A staircase lock can be used as an emergency dry dock). To avoid these mishaps, it is usual to have the whole staircase empty before starting to descend, or full before starting to ascend, apart from the initial chamber. One striking difference in using a staircase of either type (compared with a single lock, or a flight) is the best sequence for letting boats through. In a single lock (or a flight with room for boats to pass) boats should ideally alternate in direction. In

SECTION 10

#1732764805706

1248-404: A staircase, however, it is quicker for a boat to follow a previous one going in the same direction. Partly for this reason staircase locks such as Grindley Brook, Foxton, Watford and Bratch are supervised by lockkeepers, at least during the main cruising season, they normally try to alternate as many boats up, followed by down as there are chambers in the flight. As with a flight, it is possible on

1352-639: A summer venue for organised swimming, which is prohibited on safety grounds in a stretch centred on Central London . After the river took its present-day course, many of the banks of the Thames Estuary and the Thames Valley in London were partly covered in marshland , as was the adjoining Lower Lea Valley . Streams and rivers like the River Lea , Tyburn Brook and Bollo Brook drained into

1456-400: A tunnel, which when descending does not become visible until the chamber is nearly empty. A pound is the level stretch of water between two locks (also known as a reach ). The cill , also spelled sill , is a narrow horizontal ledge protruding a short way into the chamber from below the upper gates. Allowing the rear of the boat to "hang" on the cill is the main danger when descending

1560-471: Is a landmark on the Boat Race course, while Glover's Island forms the centre of a view from Richmond Hill . Islands of historical interest include Magna Carta Island at Runnymede , Fry's Island at Reading, and Pharaoh's Island near Shepperton. In more recent times Platts Eyot at Hampton was the place where Motor Torpedo Boats (MTB)s were built, Tagg's Island near Molesey was associated with

1664-426: Is a normal top gate, and the intermediate gates are all as tall as the bottom gate). As there is no intermediate pound, a chamber can only be filled by emptying the one above, or emptied by filling the one below: thus the whole staircase has to be full of water (except for the bottom chamber) before a boat starts to ascend, or empty (except for the top chamber) before a boat starts to descend. In an "apparent" staircase

1768-402: Is an important water source, especially in the drier months, so maintaining its quality and quantity is extremely important. Groundwater is vulnerable to surface pollution, especially in highly urbanised areas. Brooks, canals and rivers, within an area of 3,842 sq mi (9,951 km ), combine to form 38 main tributaries feeding the Thames between its source and Teddington Lock . This

1872-649: Is believed that Tamesubugus' name was derived from that of the river. Tamese was referred to as a place, not a river in the Ravenna Cosmography ( c.  AD 700 ). The river's name has always been pronounced with a simple t /t/ ; the Middle English spelling was typically Temese and the Brittonic form Tamesis . A similar spelling from 1210, "Tamisiam" (the accusative case of "Tamisia"; see Kingston upon Thames § Early history ),

1976-604: Is formed for much of its length for shipping and supplies: through the Port of London for international trade, internally along its length and by its connection to the British canal system. The river's position has put it at the centre of many events in British history, leading to it being described by John Burns as "liquid history". Two broad canals link the river to other rivers: the Kennet and Avon Canal ( Reading to Bath ) and

2080-697: Is found in Magna Carta . The Thames through Oxford is sometimes called the Isis . Historically, and especially in Victorian times, gazetteers and cartographers insisted that the entire river was correctly named the Isis from its source down to Dorchester on Thames and that only from this point, where the river meets the Thame and becomes the "Thame-isis" (supposedly subsequently abbreviated to Thames) should it be so called. Ordnance Survey maps still label

2184-443: Is only a staircase if successive lock chambers share a gate (i.e. do not have separate top and bottom gates with a pound between them). Most flights are not staircases, because each chamber is a separate lock (with its own upper and lower gates), there is a navigable pound (however short) between each pair of locks, and the locks are operated in the conventional way. However, some flights include (or consist entirely of) staircases. On

SECTION 20

#1732764805706

2288-452: Is responsible for managing the flow of water to help prevent and mitigate flooding, and providing for navigation: the volume and speed of water downstream is managed by adjusting the sluices at each of the weirs and, at peak high water, levels are generally dissipated over preferred flood plains adjacent to the river. Occasionally, flooding of inhabited areas is unavoidable and the agency issues flood warnings. Due to stiff penalties applicable on

2392-948: Is shared by many other river names in Britain, such as the River Tamar at the border of Devon and Cornwall , several rivers named Tame in the Midlands and North Yorkshire , the Tavy on Dartmoor , the Team of the North East, the Teifi and Teme of Wales , the Teviot in the Scottish Borders and a Thames tributary, the Thame . Kenneth H. Jackson proposed that the name of

2496-558: Is sometimes called the Isis), Reading , Henley-on-Thames and Windsor . The Thames also drains the whole of Greater London . 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 23 ft (7 m). From Oxford to the estuary, the Thames drops by 55 metres (180 ft). Running through some of

2600-523: Is the change in water-level in the lock. The two deepest locks on the English canal system are Bath deep lock on the Kennet and Avon Canal and Tuel Lane Lock on the Rochdale Canal , which both have a rise of nearly 20 feet (6.1 m). Both locks are amalgamations of two separate locks, which were combined when the canals were restored to accommodate changes in road crossings. By comparison,

2704-404: Is the usual tidal limit ; however, high spring tides can raise the head water level in the reach above Teddington and can occasionally reverse the river flow for a short time. In these circumstances, tidal effects can be observed upstream to the next lock beside Molesey weir , which is visible from the towpath and bridge beside Hampton Court Palace . Before Teddington Lock was built in 1810–12,

2808-799: The River Isis , is a river that flows through southern England including London . At 215 miles (346 km), 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

2912-811: The Berwyn Mountains in North Wales . About 450,000 years ago, in the most extreme Ice Age of the Pleistocene , the Anglian , the furthest southern extent of the ice sheet reached Hornchurch in east London, the Vale of St Albans, and the Finchley Gap . It dammed the river in Hertfordshire , resulting in the formation of large ice lakes, which eventually burst their banks and caused

3016-881: The Bollène lock on the River Rhône has a fall of at least 23 m (75 ft), the Leerstetten, Eckersmühlen and Hilpoltstein locks on the Rhine–Main–Danube Canal have a fall of 24.67 m (80.9 ft), each and the Oskemen Lock on the Irtysh River in Kazakhstan has a drop of 42 m (138 ft). The natural extension of the flash lock , or staunch, was to provide an upper gate (or pair of gates) to form an intermediate "pound" which

3120-541: The British Geological Survey from the banks of the tidal River Thames contain geochemical information and fossils which provide a 10,000-year record of sea-level change. Combined, this and other studies suggest that the Thames sea-level has risen more than 30 m during the Holocene at a rate of around 5–6 mm per year from 10,000 to 6,000 years ago. The rise of sea level dramatically reduced when

3224-570: The Churn (which feeds into the Thames near Cricklade ) rises, is also sometimes quoted as the Thames' source, as this location is farthest from the mouth and adds some 14 mi (23 km) to the river's length. At Seven Springs above the source is a stone with the Latin hexameter inscription "Hic tuus o Tamesine pater septemgeminus fons", which means "Here, O Father Thames, [is] your sevenfold source". The springs at Seven Springs flow throughout

Oxford-Burcot Commission - Misplaced Pages Continue

3328-476: The Grand Union . Operation of a staircase is more involved than a flight. Inexperienced boaters may find operating staircase locks difficult. The key worries (apart from simply being paralysed with indecision) are either sending down more water than the lower chambers can cope with (flooding the towpath, or sending a wave along the canal) or completely emptying an intermediate chamber (although this shows that

3432-684: The Grand Union Canal (London to the Midlands). The Grand Union effectively bypassed the earlier, narrow and winding Oxford Canal which remains open as a popular scenic recreational route. Three further cross-basin canals are disused but are in various stages of reconstruction: the Thames and Severn Canal (via Stroud ), which operated until 1927 (to the west coast of England), the Wey and Arun Canal to Littlehampton , which operated until 1871 (to

3536-613: The Milan canal system sponsored by Francesco Sforza ) between 1452 and 1458. In Ancient Egypt, the river-locks was probably part of the Canal of the Pharaohs : Ptolemy II is credited by some for being the first to solve the problem of keeping the Nile free of salt water when his engineers invented the lock around 274/273 BC. All pound locks have three elements: The principle of operating

3640-489: The River Lea can be considered another boundary. Most of the local riverside was also marshland. The land was drained and became farmland; it was built on after the Industrial Revolution . Canvey Island in southern Essex (area 18.45 km , 7.12 sq mi; population 40,000 ) was once marshy, but is now a fully reclaimed island in the Thames estuary, separated from the mainland of south Essex by

3744-662: The Royal Academy , London , in 1785. They are now on show at the River and Rowing Museum in Henley). Richard Coates suggests that while the river was as a whole called the Thames, part of it, where it was too wide to ford, was called * (p)lowonida . This gave the name to a settlement on its banks, which became known as Londinium , from the Indo-European roots * pleu- "flow" and * -nedi "river" meaning something like

3848-598: The Song dynasty (960–1279 CE). The Songshi or History of the Song Dynasty, volume 307, biography 66, records how Qiao Weiyue, a high-ranking tax administrator, was frustrated at the frequent losses incurred when his grain barges were wrecked on the West River near Huai'an in Jiangsu . The soldiers at one double slipway, he discovered, had plotted with bandits to wreck heavy imperial barges so that they could steal

3952-504: The Thames Barrier , which protects central London from flooding by storm surges . Below the barrier, the river passes Woolwich , Thamesmead , Dagenham , Erith , Purfleet , Dartford , West Thurrock , Northfleet , Tilbury and Gravesend before entering the Thames Estuary near Southend-on-Sea . The sea level in the Thames estuary is rising and the rate of rise is increasing. Sediment cores up to 10 m deep collected by

4056-400: The Thames and Isis Navigation Act 1750 ( 24 Geo. 2 . c. 8). This commission had similar powers but covered the entire length of the River Thames down to Staines . This article about an organisation in England is a stub . You can help Misplaced Pages by expanding it . River Thames The River Thames ( / t ɛ m z / TEMZ ), known alternatively in parts as

4160-549: The Thanetian stage of the late Palaeocene epoch. Until around 500,000 years ago, the Thames flowed on its existing course through what is now Oxfordshire , before turning to the north-east through Hertfordshire and East Anglia and reaching the North Sea near present-day Ipswich . At this time the river-system headwaters lay in the English West Midlands and may, at times, have received drainage from

4264-689: The Carrapatelo and Valeira locks on the Douro river in Portugal, which are 279 feet (85 m) long and 39 feet (12 m) wide, have maximum lifts of 115 and 108 feet (35 and 33 m) respectively. The two Ardnacrusha locks near Limerick on the Shannon navigation in Ireland have a rise of 100 feet (30 m). The upper chamber rises 60 feet (18 m) and is connected to the lower chamber by

Oxford-Burcot Commission - Misplaced Pages Continue

4368-466: The Chesapeake and Ohio Canal, the lockkeepers were required to remove the windlasses from all lock paddles at night, to prevent unauthorized use. A swell was caused by opening suddenly the paddle valves in the lock gates, or when emptying a lock. To help boats traveling downstream exit a lock, the locksman would sometimes open the paddles to create a swell, which would help "flush" the boat out of

4472-567: The Grand Union (Leicester) Canal, the Watford flight consists of a four-chamber staircase and three separate locks; and the Foxton flight consists entirely of two adjacent 5-chamber staircases. Where a very steep gradient has to be climbed, a lock staircase is used. There are two types of staircase, "real" and "apparent". A "real" staircase can be thought of as a "compressed" flight, where

4576-736: The North Sea, and the Thames Barrier was built in the 1980s to protect London from this risk. The Nore is the sandbank that marks the mouth of the Thames Estuary , where the outflow from the Thames meets the North Sea . It is roughly halfway between Havengore Creek in Essex and Warden Point on the Isle of Sheppey in Kent. Until 1964 it marked the seaward limit of the Port of London Authority. As

4680-489: The River Thames on the Tideway include the rivers Crane , Brent , Wandle , Ravensbourne (the final part of which is called Deptford Creek ), Lea (the final part of which is called Bow Creek ), Roding (Barking Creek), Darent and Ingrebourne . In London, the water is slightly brackish with sea salt, being a mix of sea and fresh water. This part of the river is managed by the Port of London Authority . The flood threat here comes from high tides and strong winds from

4784-416: The Thames Estuary), the river is subject to tidal activity from the North Sea . Before the lock was installed, the river was tidal as far as Staines, about 16 mi (26 km) upstream. London, capital of Roman Britain , was established on two hills, now known as Cornhill and Ludgate Hill . These provided a firm base for a trading centre at the lowest possible point on the Thames. A river crossing

4888-470: The Thames as "River Thames or Isis" down to Dorchester. Since the early 20th century this distinction has been lost in common usage outside of Oxford, and some historians suggest the name Isis is nothing more than a truncation of Tamesis , the Latin name for the Thames. Sculptures titled Tamesis and Isis by Anne Seymour Damer are located on the bridge at Henley-on-Thames , Oxfordshire (the original terracotta and plaster models were exhibited at

4992-439: The Thames is not Indo-European (and of unknown meaning), while Peter Kitson suggested that it is Indo-European but originated before the Britons and has a name indicating "muddiness" from a root *tā- , 'melt'. Early variants of the name include: Indirect evidence for the antiquity of the name "Thames" is provided by a Roman potsherd found at Oxford, bearing the inscription Tamesubugus fecit (Tamesubugus made [this]). It

5096-511: The Thames, from Middle English Temese , is derived from the Brittonic name for the river, Tamesas (from * tamēssa ), recorded in Latin as Tamesis and yielding modern Welsh Tafwys "Thames". The name element Tam may have meant "dark" and can be compared to other cognates such as Russian темно ( Proto-Slavic * tĭmĭnŭ ), Lithuanian tamsi "dark", Latvian tumsa "darkness", Sanskrit tamas and Welsh tywyll "darkness" and Middle Irish teimen "dark grey". The origin

5200-420: The advent of canals in Britain. The sides of the turf-lock are sloping so, when full, the lock is quite wide. Consequently, this type of lock needs more water to operate than vertical-sided brick- or stone-walled locks. On British canals and waterways most turf-sided locks have been subsequently rebuilt in brick or stone, and so only a few good examples survive, such as at Garston Lock , and Monkey Marsh Lock , on

5304-426: The boat entered the lock. Pulling on the rope slowed the boat, due to the friction of the rope against the post. A rope 2 + 1 ⁄ 2 inches (6.4 cm) in diameter and about 60 feet (18 meters) long was typically used on the Erie Canal to snub a boat in a lock. One incident, which took place in June 1873 on the Chesapeake and Ohio Canal, involved the boat the Henry C. Flagg and its drunk captain. That boat

SECTION 50

#1732764805706

5408-405: The bottom cill at all but the higher tides – the new bottom chamber rises just far enough to get the boat over the original lock cill. In China, the recently completed Three Gorges Dam includes a double five-step staircase for large ships, and a ship lift for vessels of less than 3000 metric tons. Examples of "apparent" staircases are Foxton Locks and Watford Locks on the Leicester Branch of

5512-406: The canal would cause frequent interruptions of the heavy road traffic. It can be emptied by pumping – but as this uses a lot of electricity the method used when water supplies are adequate is to drain the lock to a nearby burn . In 2016 the Kieldrecht Lock in the Port of Antwerp in Belgium took over the title of the world's largest lock from the Berendrecht Lock in the same port and still has

5616-423: The case of the Colne ), and man-made distributaries such as the Longford River . Three canals intersect this stretch: the Oxford Canal , Kennet and Avon Canal and Wey Navigation . Its longest artificial secondary channel (cut), the Jubilee River , was built between Maidenhead and Windsor for flood relief and completed in 2002. The non-tidal section of the river is managed by the Environment Agency , which

5720-424: The chambers so that some water from the emptying chamber helps to fill the other. This facility has long been withdrawn on the English canals, although the disused paddle gear can sometimes be seen, as at Hillmorton on the Oxford Canal . Elsewhere they are still in use; a pair of twinned locks was opened in 2014 on the Dortmund–Ems Canal near Münster , Germany. The once-famous staircase at Lockport, New York ,

5824-505: The chambers still have common gates, but the water does not pass directly from one chamber to the next, going instead via side ponds. This means it is not necessary to ensure that the flight is full or empty before starting. Examples of famous "real" staircases in England are Bingley and Grindley Brook . Two-rise staircases are more common: Snakeholme Lock and Struncheon Hill Lock on the Driffield Navigation were converted to staircase locks after low water levels hindered navigation over

5928-404: The chance of a boat finding a lock set in its favour. There can also be water savings: the locks may be of different sizes, so that a small boat does not need to empty a large lock; or each lock may be able to act as a side pond (water-saving basin) for the other. In this latter case, the word used is usually "twinned": here indicating the possibility of saving water by synchronising the operation of

6032-443: The cill bumper. Some canal operation authorities, primarily in the United States and Canada, call the ledge a miter sill (mitre sill in Canada). Gates are the watertight doors which seal off the chamber from the upper and lower pounds. Each end of the chamber is equipped with a gate, or pair of half-gates, traditionally made of oak or elm but now usually made of steel ). The most common arrangement, usually called miter gates ,

6136-416: The concept has been suggested in a number of cases, the only example in the world of a drop lock that has actually been constructed is at Dalmuir on the Forth and Clyde Canal in Scotland. This lock, of the single-chamber type, was incorporated during the restoration of the canal, to allow the replacement of a swing bridge (on a busy A road) by a fixed bridge, and so answer criticisms that the restoration of

6240-423: The confluence, the overall length of the Thames measured from Seven Springs, at 229 mi (369 km), is greater than the Severn's length of 220 mi (350 km). Thus, the "Churn/Thames" river may be regarded as the longest natural river in the United Kingdom. The stream from Seven Springs is joined at Coberley by a longer tributary which could further increase the length of the Thames, with its source in

6344-468: The drier parts of mainland Britain and heavily abstracted for drinking water, the Thames' discharge is low considering its length and breadth: the Severn has a discharge almost twice as large on average despite having a smaller drainage basin . In Scotland , the Tay achieves more than double the Thames' average discharge from a drainage basin that is 60% smaller. Along its course are 45 navigation locks with accompanying weirs . Its catchment area covers

SECTION 60

#1732764805706

6448-425: The flight quickly; and where water is in short supply, a single pump can recycle water to the top of the whole flight. The need for a flight may be determined purely by the lie of the land, but it is possible to group locks purposely into flights by using cuttings or embankments to "postpone" the height change. Examples: Caen Hill locks, Devizes . "Flight" is not synonymous with "Staircase" (see below). A set of locks

6552-412: The flowing river or the wide flowing unfordable river. The river gives its name to three informal areas: the Thames Valley , a region of England around the river between Oxford and West London; the Thames Gateway ; and the greatly overlapping Thames Estuary around the tidal Thames to the east of London and including the waterway itself. Thames Valley Police is a formal body that takes its name from

6656-458: The form of the now-disused Écluse des Lorraines , connecting the Canal latéral à la Loire with the River Allier . A drop lock can consist of two conventional lock chambers leading to a sump pound, or a single long chamber incorporating the sump – although the term properly applies only to the second case. As the pounds at either end of the structure are at the same height, the lock can only be emptied either by allowing water to run to waste from

6760-533: The grounds of the National Star College at Ullenwood . The Thames flows through or alongside Ashton Keynes , Cricklade , Lechlade , Oxford , Abingdon-on-Thames , Wallingford , Goring-on-Thames and Streatley (at the Goring Gap ), Pangbourne and Whitchurch-on-Thames , Reading , Wargrave , Henley-on-Thames , Marlow , Maidenhead , Windsor and Eton , Staines-upon-Thames and Egham , Chertsey , Shepperton , Weybridge , Sunbury-on-Thames , Walton-on-Thames , Molesey and Thames Ditton . The river

6864-404: The ice melt nearly concluded over the past 4,000 years. Since the beginning of the 20th century, rates of sea level rise range from 1.22 mm per year to 2.14 mm per year. The Thames River Basin District, including the Medway catchment, covers an area of 6,229 sq mi (16,130 km ). The entire river basin is a mixture of urban and rural, with rural landscape predominating in

6968-416: The impresario Fred Karno and Eel Pie Island at Twickenham was the birthplace of the South East's R&B music scene. Westminster Abbey and the Palace of Westminster (commonly known today as the Houses of Parliament ) were built on Thorney Island , which used to be an eyot . Researchers have identified the River Thames as a discrete drainage line flowing as early as 58 million years ago, in

7072-414: The intermediate pounds have disappeared, and the upper gate of one lock is also the lower gate of the one above it. However, it is incorrect to use the terms staircase and flight interchangeably: because of the absence of intermediate pounds, operating a staircase is very different from operating a flight. It can be more useful to think of a staircase as a single lock with intermediate levels (the top gate

7176-403: The lock gates could be replaced and the boat removed from the lock. To economise, especially where good stone would be prohibitively expensive or difficult to obtain, composite locks were made, i.e. they were constructed using rubble or inferior stone, dressing the inside walls of the lock with wood, so as not to abrade the boats. This was done, for instance, on the Chesapeake and Ohio Canal with

7280-403: The lock. A boatsman might ask for a back swell, that is, to open and shut the paddles a few times to create some waves, to help him get off the bank where he was stuck. If boats ran aground (from being overloaded) they sometimes asked passing crews to tell the upstream lock to give them an extra heavy swell, which consisted of opening all the paddles on the lock gate, creating a surge that affected

7384-561: The locks near the Paw Paw Tunnel . and also the Chenango Canal On large modern canals, especially very large ones such as ship canals , the gates and paddles are too large to be hand operated, and are operated by hydraulic or electrical equipment. On the Caledonian Canal the lock gates were operated by man-powered capstans , one connected by chains to open the gate and another to draw it closed. By 1968 these had been replaced by hydraulic power acting through steel rams. The construction of locks (or weirs and dams) on rivers obstructs

7488-688: The new canal was low. This resulted in a sequential pair of locks, with gates pointing in opposite directions: one example was at Hall Green near Kidsgrove , where the southern terminus of the Macclesfield Canal joined the Hall Green Branch of the earlier Trent and Mersey Canal . The four gate stop lock near Kings Norton Junction, between the Stratford-upon-Avon Canal and the Worcester and Birmingham Canal

7592-426: The non-tidal river, which is a drinking water source before treatment, sanitary sewer overflow from the many sewage treatment plants covering the upper Thames basin should be rare in the non-tidal Thames. However, storm sewage overflows are still common in almost all the main tributaries of the Thames despite claims by Thames Water to the contrary. Below Teddington Lock (about 55 mi or 89 km upstream of

7696-528: The passage of fish. Some fish such as lampreys, trout and salmon go upstream to spawn. Measures such as a fish ladder are often taken to counteract this. Navigation locks have also potential to be operated as fishways to provide increased access for a range of biota. Locks can be built side by side on the same waterway. This is variously called doubling , pairing , or twinning . The Panama Canal has three sets of double locks. Doubling gives advantages in speed, avoiding hold-ups at busy times and increasing

7800-637: The river passes Pimlico and Vauxhall , and then forms one of the principal axes of the city, from the Palace of Westminster to the Tower of London . At this point, it historically formed the southern boundary of the medieval city, with Southwark , on the opposite bank, then being part of Surrey . Beyond central London, the river passes Bermondsey , Wapping , Shadwell , Limehouse , Rotherhithe , Millwall , Deptford , Greenwich , Cubitt Town , Blackwall , New Charlton and Silvertown , before flowing through

7904-480: The river to divert onto its present course through the area of present-day London. The ice lobe which stopped at present-day Finchley deposited about 14 metres of boulder clay there. Its torrent of meltwater gushed through the Finchley Gap and south towards the new course of the Thames, and proceeded to carve out the Brent Valley in the process. Lock (water navigation) Locks are used to make

8008-439: The river was tidal at peak spring tides as far as Staines upon Thames . In descending order, non-related tributaries of the non-tidal Thames, with river status, are the Churn , Leach , Cole , Ray , Coln , Windrush , Evenlode , Cherwell , Ock , Thame , Pang , Kennet , Loddon , Colne , Wey and Mole . In addition, there are occasional backwaters and artificial cuts that form islands, distributaries (most numerous in

8112-596: The river, covering three counties . In non-administrative use, the river's name is used in those of Thames Valley University , Thames Water , Thames Television , publishing company Thames & Hudson , Thameslink (north–south rail service passing through central London ) and South Thames College . An example of its use in the names of historic entities is the Thames Ironworks and Shipbuilding Company . Marks of human activity, in some cases dating back to Pre-Roman Britain , are visible at various points along

8216-456: The river, while some islands, e.g. Thorney Island , formed over the ages. The northern tip of the ancient parish of Lambeth , for example, was marshland known as Lambeth Marshe , but it was drained in the 18th century; the street names Lower Marsh and Upper Marsh preserve a memory. Until the middle of the Victorian era, malaria was commonplace beside the River Thames, even in London, and

8320-519: The river. These include a variety of structures connected with use of the river, such as navigations, bridges and watermills , as well as prehistoric burial mounds . The lower Thames in the Roman era was a shallow waterway winding through marshes. But centuries of human intervention have transformed it into a deep tidal canal flowing between 200 miles of solid walls; these defend a floodplain where 1.5 million people work and live. A major maritime route

8424-611: The sandbank was a major hazard for shipping coming in and out of London, in 1732 it received the world's first lightship . This became a major landmark, and was used as an assembly point for shipping. Today it is marked by Sea Reach No. 1 Buoy. The River Thames contains over 80 islands ranging from the large estuarial marshlands of the Isle of Sheppey and Canvey Island to small tree-covered islets like Rose Isle in Oxfordshire and Headpile Eyot in Berkshire. They are found all

8528-469: The size of the lock and whether the water in the lock was originally set at the boat's level. Boaters approaching a lock are usually pleased to meet another boat coming towards them, because this boat will have just exited the lock on their level and therefore set the lock in their favour – saving about 5 to 10 minutes. However, this is not true for staircase locks, where it is quicker for boats to go through in convoy, and it also uses less water. The rise

8632-541: The south coast), and the Wilts & Berks Canal . Rowing and sailing clubs are common along the Thames, which is navigable to such vessels. Kayaking and canoeing also take place. Major annual events include the Henley Royal Regatta and the Boat Race , while the Thames has been used during two Summer Olympic Games : 1908 ( rowing ) and 1948 ( rowing and canoeing ). Safe headwaters and reaches are

8736-407: The spilled grain. In 984 Qiao installed a pair of sluice-gates two hundred and fifty feet apart, the entire structure roofed over like a building. By siting two staunch gates so close to one another, Qiao had created a short stretch of canal, effectively a pound-lock, filled from the canal above by raising individual wooden baulks in the top gate and emptied into the canal below by lowering baulks in

8840-411: The staircase by moving sideways around each other; or at peak times, one can have all the chambers full simultaneously with boats travelling in the same direction. When variable conditions meant that a higher water level in the new canal could not be guaranteed, then the older company would also build a stop lock (under its own control, with gates pointing towards its own canal) which could be closed when

8944-413: The sump to a lower stream or drain, or (less wastefully) by pumping water back up to the canal. Particularly in the two-chamber type, there would be a need for a bypass culvert, to allow water to move along the interrupted pound and so supply locks further down the canal. In the case of the single-chamber type, this can be achieved by keeping the lock full and leaving the gates open while not in use. While

9048-493: The title for largest volume. In 2022 the IJmuiden sea lock serving the Port of Amsterdam became the world's largest lock by surface area. The lock is 500 m (1,600 ft) long, 70 m (230 ft) wide and has sliding lock gates creating a usable depth of 18 m (59 ft). The size of locks cannot be compared without considering the difference in water level that they are designed to operate under. For example,

9152-400: The top gate and raising ones in the lower. A turf-sided lock is an early form of canal lock design that uses earth banks to form the lock chamber, subsequently attracting grasses and other vegetation, instead of the now more familiar and widespread brick, stone, or concrete lock wall constructions. This early lock design was most often used on river navigations in the early 18th century before

9256-462: The two locks was rather more than 50 paces, and the whole space was covered with a great roof like a shed. The gates were 'hanging gates'; when they were closed the water accumulated like a tide until the required level was reached, and then when the time came it was allowed to flow out. The water level could differ by 4 or 5 feet (1.2 or 1.5 m) at each lock and in the Grand Canal the level

9360-466: The university, to clean the river and to install locks and weirs . Iffley Lock , Sandford Lock and a lock on the Swift Ditch near the present Abingdon Lock were built in 1631. However, its work was slow and costly and the first barge did not reach Oxford until 1635. Consequently Thames Navigation Commissioners were appointed in 1751 by a further act of Parliament under King George II ,

9464-416: The water on the pound above sometimes causing boats to run aground. In addition, it raised the water level on the pound below, causing some boats to strike bridges or get stuck. On horse-drawn and mule-drawn canals, snubbing posts were used to slow or stop a boat in the lock. A 200-ton boat moving at a few miles an hour could destroy the lock gate. To prevent this, a rope was wound around the snubbing post as

9568-705: The way from Fiddler's Island in Oxfordshire to the Isle of Sheppey in Kent. Some of the largest inland islands, for example Formosa Island near Cookham and Andersey Island at Abingdon, were created naturally when the course of the river divided into separate streams. In the Oxford area the river splits into several streams across the floodplain ( Seacourt Stream , Castle Mill Stream , Bulstake Stream and others), creating several islands ( Fiddler's Island , Osney and others). Desborough Island , Ham Island at Old Windsor and Penton Hook Island were artificially created by lock cuts and navigation channels. Chiswick Eyot

9672-412: The western part. The area is among the driest in the United Kingdom. Water resources consist of groundwater from aquifers and water taken from the Thames and its tributaries, much of it stored in large bank-side reservoirs . The Thames itself provides two-thirds of London's drinking water, while groundwater supplies about 40 per cent of public water supplies in the overall catchment area. Groundwater

9776-512: The whole pound below. On the Erie Canal, some loaded boats needed a swell to get out of the lock. Particularly lumber boats, being top heavy, would list to one side and get stuck in the lock, and needed a swell to get them out. Some lockkeepers would give a swell to anyone to help them on the way, but some would ask for money for the swell. The Erie Canal management did not like swelling for two reasons. First, it used too much water lowering

9880-580: The year, while those at Thames Head are seasonal (a winterbourne ). With a length of 215 mi (346 km), the Thames is the longest river entirely in England. (The longest river in the United Kingdom, the Severn , flows partly in Wales .) However, as the River Churn, sourced at Seven Springs, is 14 mi (23 km) longer than the section of the Thames from its traditional source at Thames Head to

9984-463: Was all that need be emptied when a boat passed through. This type of lock, called a pound lock was known in Imperial China and ancient Europe and was used by Greek engineers in the Canal of the Pharaohs under Ptolemy II (284 to 246 BC), when engineers solved the problem of overcoming the difference in height through canal locks . Pound locks were first used in medieval China during

10088-422: Was already leaking; the crew, having partially pumped the water out, entered Lock 74, moving in front of another boat. Because they failed to snub the boat, it crashed into and knocked out the downstream gates. The outrush of water from the lock caused the upstream gates to slam shut, breaking them also, and sending a cascade of water over the boat, sinking it. This suspended navigation on the canal for 48 hours until

10192-416: Was also a doubled set of locks. Five twinned locks allowed east- and west-bound boats to climb or descend the 60 feet (18 m) Niagara Escarpment , a considerable engineering feat in the nineteenth century. While Lockport today has two large steel locks, half of the old twin stair acts as an emergency spillway and can still be seen, with the original lock gates having been restored in early 2016. Loosely,

10296-479: Was built at the site of London Bridge . London Bridge is now used as the basis for published tide tables giving the times of high tide . High tide reaches Putney about 30 minutes later than London Bridge, and Teddington about an hour later. The tidal stretch of the river is known as "the Tideway ". Tide tables are published by the Port of London Authority and are available online. Times of high and low tides are also posted on Twitter. The principal tributaries of

10400-463: Was frequently lethal. Some cases continued to occur into the early 20th century. Draining of the marshes helped with its eradication, but the causes are complex and unclear. The East End of London , also known simply as the East End , was the area of London east of the medieval walled City of London and north of the River Thames, although it is not defined by universally accepted formal boundaries;

10504-412: Was invented by Leonardo da Vinci sometime around the late 15th century. On the old Erie Canal , there was a danger of injury when operating the paddles: water, on reaching a certain position, would push the paddles with a force which could tear the windlass (or handle) out of one's hands, or if one was standing in the wrong place, could knock one into the canal, leading to injuries and drownings. On

10608-456: Was raised in this way by 138 feet (42 m). In medieval Europe a sort of pound lock was built in 1373 at Vreeswijk , Netherlands. This pound lock serviced many ships at once in a large basin . Yet the first true pound lock was built in 1396 at Damme near Bruges , Belgium. The Italian Bertola da Novate (c. 1410–1475) constructed 18 pound locks on the Naviglio di Bereguardo (part of

10712-606: Was replaced in 1914 by a pair of guillotine lock gates which stopped the water flow regardless of which canal was higher. These gates have been permanently open since nationalisation. The best known example of a round lock is the Agde Round Lock on the Canal du Midi in France. This serves as a lock on the main line of the canal and allows access to the Hérault River . A second French round lock can be found in

10816-617: Was subject to minor redefining and widening of the main channel around Oxford, Abingdon and Marlow before 1850, when further cuts to ease navigation reduced distances further. Molesey faces Hampton , and in Greater London the Thames passes Hampton Court Palace , Surbiton , Kingston upon Thames , Teddington , Twickenham , Richmond (with a famous view of the Thames from Richmond Hill), Syon House , Kew , Brentford , Chiswick , Barnes , Hammersmith , Fulham , Putney , Wandsworth , Battersea and Chelsea . In central London ,

#705294