A flash lock is a type of lock for river or canal transport.
Contents
Early locks were designed with a single gate, known as a flash lock or staunch lock. The earliest European references to what were clearly flash locks were in Roman times. [3]
A flash lock is a type of lock for river or canal transport.
Early locks were designed with a single gate, known as a flash lock or staunch lock. The earliest European references to what were clearly flash locks were in Roman times. [3]
In England the "gate" was similar to a temporary needle dam: a set of boards, called paddles, supported against the current by upright timbers called rymers which normally kept the level of water above it to navigable levels. Boats moving downstream would wait above the lock until the paddles (and their rymers) [4] were removed, which would allow a "flash" of water to pass through, carrying the boats with it. Boats moving upstream would be winched or towed through the lock with the paddles removed. Considerable skill was involved both in removing the paddles in a timely manner and navigating the boat through the lock. Flash locks of this type have been documented since at least 1295 C.E. [5]
Flash locks were commonly built into small dams or weirs where a head of water was used for powering a mill. The lock allowed boats to pass the weir while still allowing the mill to operate when the gate was closed. However it could take up to a day or even more to restore the water levels after a boat had passed, so their use was unpopular with the millers.
As navigation increased in importance, improvements were made to the basic design, and they came to be known by various names according to where they were located. Thus on the Thames they were called navigation weirs, on the East Anglian rivers they were called staunches, those on the River Avon, Warwickshire were called water gates, and in a number of instances they were called half locks. On the River Nene and some of the tributaries of the River Great Ouse, a design using a guillotine gate in a wooden frame was used from the early seventeenth century onwards. The gate was opened by operating a large spoked wheel, connected by chains to a toothed drum. [6]
The pound lock holds water between two gates, and is considerably easier to navigate. Pound locks have been built in China since 983, in the Netherlands from 1065 and in Britain from the 1560s. Nevertheless, a few flash locks remained after the introduction of pound locks. Flash locks on the Nene continued to be used until they were replaced in a programme of modernisation, which included building new locks, carried out between 1936 and 1941. The last flash lock on the Thames was Hart's Lock (also known as Eaton Lock), [4] which lasted until 1937, while on the Lower Avon, the structure of Cropthorne Water Gate lasted until the reopening of the river to navigation in 1961, although it had not been used for navigation for many years before that. Although slightly different in concept, Thames Lock at Weybridge on the Wey Navigation had an additional single gate some 100 yards (91 m) below the lock, which when closed raises the water level above it, allowing boats which would normally foul the cill to work through the lock. It continued in use until 1969, to enable grain barges to use the lock, and although grain traffic stopped in that year, it recommenced in 1981, when the gate was again used. [7] The gate is still used at the lock-keeper's discretion for boats which have a draught exceeding 1.75 feet (0.53 m). [8]
The weirs which are the remnants of flash locks can still be seen on the River Thames though they are not used any more for navigation as regular pound locks were introduced in the eighteenth and nineteenth centuries and the last flash lock removed in 1937. [4] [5] The Environment Agency is now involved in a programme of replacing these, [9] as their manual operation is considered to be dangerous, and involves lifting weights which exceed those recommended by the Manual Handling Operations Regulations 1992. [10] Most weirs on the River Thames in the present day are operated with the aid of hydraulics and other less-dangerous manual modes of operation.
Two or three paddles are stacked between each of the rymers, which slot into a beam placed on the bottom of the river. The paddles are of differing lengths allowing a very fine adjustment of the amount of water flowing through the weir. [11]
Four of these weirs were replaced in 2009. Three were on the Thames at Mapledurham, Molesey and Radcot, while the fourth was at Blake's Lock, the first lock on the River Kennet, which is managed as part of the Thames. Three more of these weirs, at Rushey, Goring and Streatley, have been Grade II listed since 2009, but the EA is proposing to replace most of Rushey, which would be the only full-width example left. [10]
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 that rises and falls.
The Lee Navigation is a canalised river incorporating the River Lea. It flows from Hertford Castle Weir to the River Thames at Bow Creek; its first lock is Hertford Lock and its last Bow Locks.
The English River Thames is navigable from Cricklade or Lechlade to the sea, and this part of the river falls 71 meters (234 feet). There are 45 locks on the river, each with one or more adjacent weirs. These lock and weir combinations are used for controlling the flow of water down the river, most notably when there is a risk of flooding, and provide for navigation above the tideway.
Bray Lock is a lock and weir on the River Thames in England near Bray and Dorney Reach, and is just above the M4 Bridge across the Thames. The lock is on the Buckinghamshire side of the river on the opposite bank from Bray itself and Maidenhead which are in Berkshire. Here, the county line stands roughly halfway between the lock and the opposite bank, following the course of the Thames itself. The pound lock was built by the Thames Navigation Commission relatively late, in 1845. The lock keeper's cottage is on an island between the lock and the weir.
Whitchurch Lock is a lock and weir on the River Thames in England. It is a pound lock, built by the Thames Navigation Commissioners in 1787. It is on an island near the Oxfordshire village of Whitchurch-on-Thames and is accessible only by boat.
Shiplake Lock is a lock and weir situated on the River Thames in England between the villages of Shiplake and Lower Shiplake, Oxfordshire. It is just above the points where the River Loddon joins the Thames and Shiplake Railway Bridge crosses the river. The first pound lock was built by the Thames Navigation Commission in 1773.
Goring Lock is a lock and weir situated on the River Thames in England at the Goring Gap in the Chiltern Hills. The lock is located on the Oxfordshire bank at Goring-On-Thames, with Streatley, Berkshire on the opposite side of the river. It is just upstream of Goring and Streatley Bridge. The lock was first built in 1787 by the Thames Navigation Commissioners
Cookham Lock is a lock with weirs situated on the River Thames near Cookham, Berkshire, about a half-mile downstream of Cookham Bridge. The lock is set in a lock cut which is one of four streams here and it is surrounded by woods. On one side is Sashes Island and on the other is Mill Island connected to Formosa Island, the largest on the non-tidal Thames.
The Thames Conservancy was a body responsible for the management of that river in England. It was founded in 1857 to replace the jurisdiction of the City of London up to Staines. Nine years later it took on the whole river from Cricklade in Wiltshire to the sea at Yantlet Creek on the Isle of Grain. Its territory was reduced when the Tideway was transferred to the Port of London Authority in 1909.
Boulter's Lock is a lock and weir on the River Thames in England north-east of Maidenhead town centre, Berkshire. The present 1912-built lock replaces those at this point of the river to the immediate east dating from the late 16th century and that of 1772 built by the Thames Navigation Commission. The lock is on the western side of the north–south flowing reach between the A4094 Maidenhead to Cookham road and Ray Mill Island. The name is variably used for the immediate surrounding area.
Day's Lock is a lock on the River Thames near Dorchester-on-Thames, Oxfordshire, England on the Dorchester side of the river.
Iffley Lock is a lock on the River Thames in England near the village of Iffley, Oxfordshire. It is on the southern outskirts of Oxford. The original lock was built by the Oxford-Burcot Commission in 1631 and the Thames Navigation Commission replaced this in 1793. The lock has a set of rollers to allow punts and rowing boats to be moved between the water levels.
The River Wey Navigation and Godalming Navigation together provide a 20-mile (32 km) continuous navigable route from the River Thames near Weybridge via Guildford to Godalming. Both waterways are in Surrey and are owned by the National Trust. The River Wey Navigation connects to the Basingstoke Canal at West Byfleet, and the Godalming Navigation to the Wey and Arun Canal near Shalford. The navigations consist of both man-made canal cuts and adapted parts of the River Wey.
Benson Lock is a lock on the River Thames in England, close to Benson, Oxfordshire but on the opposite bank of the river. The first pound lock here was built by the Thames Navigation Commission in 1788 and it was replaced by the present masonry lock in 1870. The distance between Benson Lock and Cleeve Lock downstream is 6.5 miles (10.4 km) - the longest distance between locks on the River Thames.
Sunbury Lock is a lock complex of the River Thames in England near Walton-on-Thames in north-west Surrey, the third lowest of forty four on the non-tidal reaches. The complex adjoins the right, southern bank about 1⁄2 mile (0.80 km) downstream of the Weir Hotel.
Hurley Lock is a lock and weir on the River Thames in England, situated in a clump of wooded islands close to the village of Hurley, Berkshire. The lock was first built by the Thames Navigation Commissioners in 1773.
Cleeve Lock is a lock on the River Thames, in Oxfordshire, England. It is located just upstream of Goring and Streatley villages, on the eastern side of the river within the village of Goring. There was a hamlet of Cleeve, after which the lock is named, but it dropped out of use, as always part of Goring.
Eynsham Lock is a lock on the River Thames in England. It is on the southern bank near Swinford Oxfordshire. The large village of Eynsham is a little distance away on the northern bank.
Shifford Lock is a lock on the River Thames in England. It is in the centre of a triangle formed by the small villages of Shifford, Duxford and Chimney in Oxfordshire. It is at the start of a navigation cut built with the lock by the Thames Conservancy in 1898. This was the only new lock built on the non-tidal Thames in the era of falling revenue after the Thames Conservancy took over responsibilities of the Thames Navigation Commission. It replaced a flash lock in a weir about 3⁄4 mile (1.2 km) downstream.
Rushey Lock is a lock on the River Thames in England. It is on the northern bank of the river in Oxfordshire, at a considerable distance from any village, the nearest being Buckland Marsh, a hamlet on the road to Buckland to the south of the river.
