Misplaced Pages

#139860

85-603: The Hiram M. Chittenden Locks , or Ballard Locks , is a complex of locks at the west end of Salmon Bay in Seattle , Washington's Lake Washington Ship Canal , between the neighborhoods of Ballard to the north and Magnolia to the south. The Ballard Locks carry more boat traffic than any other lock in the U.S., and the locks, along with the fish ladder and the surrounding Carl S. English Jr. Botanical Gardens , attract more than one million visitors annually, making it one of Seattle's top tourist attractions. The construction of

170-512: A National Historic Civil Engineering Landmark . As early as 1854, there was discussion of building a navigable connection between Lake Washington and Puget Sound for the purpose of transporting logs, milled lumber, and fishing vessels. Thirteen years later, the United States Navy endorsed a canal project, which included a plan for building a naval shipyard on Lake Washington. In 1891 the U.S. Army Corps of Engineers started planning

255-474: 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 a flash lock . Pound locks were first used in China during

340-558: A 235 ft (72 m) spillway with six 32 ft × 12 ft (9.8 m × 3.7 m) gates to assist in water-level control. A fish ladder is integrated into the locks for migration of anadromous fish, notably salmon . The grounds feature a visitors center, as well as the Carl S. English Jr. Botanical Gardens . Operated by the US Army Corps of Engineers , the locks were formally opened on July 4, 1917, although

425-528: 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

510-426: 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

595-709: A hinged barrier was installed just upstream of the large lock. This hollow metal barrier is filled with air to remain in the upright position, blocking the heavier salt water. When necessary to accommodate deep-draft vessels, the barrier is flooded and sinks to the bottom of the chamber. The fish ladder at the Chittenden locks is unusual—materials published by the federal government say "unique"—in being located where salt and fresh water meet. Normally, fish ladders are located entirely within fresh water. Pacific salmon are anadromous ; they hatch in lakes, rivers, and streams—or, nowadays fish hatcheries —migrate to sea, and only at

680-531: A large part of the Eastlake neighborhood, making tap water brown and unpotable. Many restaurants and other businesses were forced to close. There was concern for the integrity of a 40-inch main adjacent to the smaller one that broke. With the bridge closed, surface traffic between Seattle's University District and Downtown areas was heavily impacted. It was reopened on May 3, 2007, after city workers poured about 40 cubic yards of stabilizing concrete-sand slurry around

765-480: 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

850-537: 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

935-436: A major run of Sockeye Salmon using stock from Baker River, Washington. The ladder was designed to use attraction water: fresh water flowing swiftly out the bottom of the fish ladder, in the direction opposite which anadromous fish migrate at the end of their lives. However, the attraction water from this first ladder was not effective. Instead, most salmon used the locks. This made them an easy target for predators like Herschel

SECTION 10

#1732782377140

1020-451: A part of the rebuilding, the Corps also added an underground chamber with a viewing gallery. The fish approaching the ladder smell the attraction water, recognizing the scent of Lake Washington and its tributaries. They enter the ladder, and either jump over each of the 21 weirs or swim though tunnel-like openings. They exit the ladder into the fresh water of Salmon Bay. They continue following

1105-428: A relative few survive to adulthood. Causes of death include natural predators, commercial and sport fishing, disease, low stream flows, poor water quality, flooding, and concentrated developments along streams and lakes. Visitors to the locks can observe the salmon through windows as they progress along their route. Although the viewing area is open year-round, the "peak" viewing time is during spawning season, from about

1190-480: 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

1275-404: 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

1360-400: 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

1445-426: 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

1530-565: Is drained for approximately 2-weeks, usually in November, and the small lock is drained for about the same period, usually in March. The locks can elevate a 760-by-80-foot (232 m × 24 m) vessel 26 ft (7.9 m), from the level of Puget Sound at a very low tide to the level of freshwater Salmon Bay, in 10–15 minutes. The locks handle both pleasure boats and commercial vessels, ranging from kayaks to fishing boats returning from

1615-414: Is necessary for floating bridges , mooring facilities, and vessel clearances under bridges. "Smolt flumes" in the spillway help young salmon to pass safely downstream. Higher water levels are maintained in the summer to accommodate recreation as well as to allow the lakes to act as a water storage basin in anticipation of drought conditions. If excessive salt water were allowed to migrate into Salmon Bay,

1700-443: 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

1785-575: 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,

SECTION 20

#1732782377140

1870-523: The Bering Sea to cargo ships. Over 1 million tons of cargo, fuel, building materials, and seafood products pass through the locks each year. South of the small lock is a spillway dam with tainter gates used to regulate the freshwater levels of the ship canal and lakes. The gates on the dam release or store water to maintain the lake within a 2 ft (0.61 m) range of 20 to 22 ft (6.1 to 6.7 m) above sea level. Maintaining this lake level

1955-881: 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

2040-476: 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

2125-596: The Kennet and Avon Canal . University Bridge (Seattle) The University Bridge is a double-leaf bascule bridge in Seattle , Washington that carries Eastlake Avenue traffic over Portage Bay between Eastlake to the south and the University District to the north. It opened on July 1, 1919, and was extensively rebuilt from 1932 to 1933. It is included in the National Register of Historic Places . The bridge opened in 1919 under

2210-613: 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

2295-625: 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

2380-598: 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

2465-560: The Ballard, or Government, Locks connecting Salmon Bay to Shilshole Bay began in 1911, proceeding without further controversy or legal entanglements. In July 1912, the Locks gates were closed for the first time, turning Salmon Bay from saltwater to freshwater. The first ship passed through the locks on August 3, 1916. On August 25, 1916, the temporary dam at Montlake was breached. During the following three months, Lake Washington drained, lowering

2550-689: 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

2635-679: The Cedar River to spawn and most end up at the Landsberg Dam Hatchery. Chinook and Coho migrate up the Issaquah Creek and most end up at the Issaquah Hatchery. Steelhead ( Oncorhynchus mykiss ), once migrated through the Locks but none have been seen in years. The run is considered functionally extinct. Lock (water transport) Locks are used to make a river more easily navigable, or to allow

Ballard Locks - Misplaced Pages Continue

2720-466: 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

2805-483: The Duwamish causing frequent flooding. The rerouting of the rivers opened up huge lowland areas for development but significantly disrupted the Duwamish salmon runs. To rectify this problem, salmon runs were reintroduced allowing the fish to migrate through the locks. The locks officially opened for boat traffic on May 8, 1917. The total cost of the project to that point was $ 3.5 million, with $ 2.5 million having come from

2890-567: 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

2975-605: The South. White River was rerouted into the Puyallup River. Cedar and White Rivers did support significant Salmon runs but also created severe flooding conditions for the early settlers. The rerouting of these two major rivers was a mixed blessing, while reducing flood threats, the Duwamish River salmon runs were decimated. To rectify this situation, salmon runs were rerouted through the Locks, which included introducing

3060-521: The United States. Wooden paving had to be replaced every ten years or so; the steel-mesh grating has been replaced once, in 1990. The reconstructed bridge was opened April 7, 1933. All three double-leaf bascule bridges (Ballard, Fremont, and University) were added to the National Register of Historic Places in 1982. In 2014, its electronic controls were replaced after several components had worn out and caused multi-hour delays to lift and lower

3145-423: The accompanying diagram). The lower gates ( B ) and the draining valve ( D ) are closed. The vessel is assisted by the lockwall attendants who assure it is tied down and ready for the chamber to be drained. Next, the upper gates ( A ) and the filling valve ( C ) are closed and the draining valve ( D ) is opened allowing water to drain via gravity out to Puget Sound. When the water pressure is equal on both sides of

3230-475: 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

3315-720: The beginning of July through mid-August. A public art work, commissioned by the Seattle Arts Commission, provides literary interpretation of the experience through recordings of Seattle poet Judith Roche's "Salmon Suite," a sequence of five poems tied to the annual migratory sequence of the fish. Among the species of salmonids migrating routinely through the ladder at the Chittenden Locks are Chinook (king) salmon ( Oncorhynchus tshawytscha ), Coho (silver) salmon ( Oncorhynchus kisutch ), Sockeye (red) salmon ( Oncorhynchus nerka ). Sockeye primarily migrate up

3400-587: 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

3485-471: 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

Ballard Locks - Misplaced Pages Continue

3570-521: The bridge. During especially hot summer days, the University Bridge need daily dousings with cool water to avoid expanding so much that they bind. On May 2, 2007, a 24-inch (61 cm) water main broke near the south end of the University Bridge, creating a 10-foot-deep (3.0 m) sinkhole forcing the closure of the bridge. The sinkhole also swallowed two unoccupied parked cars. The water main break compromised water quality and pressure in

3655-641: 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

3740-544: 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 ,

3825-631: 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

3910-404: 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

3995-496: 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 ,

4080-523: 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

4165-667: The control of the Corps of Engineers, for excavation of the canal between Lake Union and Lake Washington. In June 1910, the US Congress gave its approval for the lock, on the condition that the rest of the canals along the route be paid for locally. Construction was then delayed by legal challenges, mainly by mill owners in Ballard who feared property damage and loss of waterfront in Salmon Bay, and by Lake Washington property owners. Under Major James. B. Cavanaugh , Chittenden's replacement as Seattle District Commander, construction of

4250-477: The end of their life return to fresh water to spawn. Prior to the Locks construction, no significant salmon runs existed here, as there was only a small drainage stream from Lake Union into Salmon Bay. In order to provide enough water to operate the Locks, Cedar River was rerouted into Lake Washington (which was lowered 9 feet). Cedar River originally flowed into the Duwamish River along with the White River from

4335-572: The federal government and the rest from local governments. To allow for the intended boat traffic, three bridges were removed along the ship canal route, at Latona Avenue, Fremont, Stone Way. The Ballard and Fremont Bridges were completed in 1917, followed by the University Bridge in 1919, and Montlake Bridge in 1925. The University Bridge was improved in 1932, and in 1934 the Lake Washington Ship Canal project

SECTION 50

#1732782377140

4420-547: The first ship passed on August 3, 1916. They were named after US Army Major Hiram M. Chittenden, the Seattle District Engineer for the Corps of Engineers from April 1906 to September 1908. They were added to the National Register of Historic Places in 1978. Vessels passing from the freshwater Lakes Washington and Union to Puget Sound enter the lock chamber through the open upper gates ( A in

4505-425: 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

4590-518: 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

4675-418: The gate, the lower gates ( B ) are opened, allowing the vessels to leave the lock chamber. The process is reversed for upstream locking. The complex includes two locks. Using the small lock when boat traffic is low conserves fresh water during summer, when the lakes receive less inflow. Having two locks also allows one of the locks to be drained for maintenance without blocking all boat traffic. The large lock

4760-414: 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

4845-403: 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

4930-403: 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

5015-757: 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

5100-509: The locks profoundly reshaped the topography of Seattle and the surrounding area, lowering the water level of Lake Washington and Lake Union by 8.8 feet (2.7 m), adding miles of new waterfront land, reversing the flow of rivers, and leaving piers in the eastern half of Salmon Bay high and dry. The Locks are listed on the National Register of Historic Places and have been designated by the American Society of Civil Engineers as

5185-494: The locks. Conversely, with several rivers redirected, flooding worsened throughout the watershed. That last problem was exacerbated by logging, and at times during storms the locks had to be opened just to allow water to flow out. The locks and associated facilities serve three purposes: The complex includes two locks, 30 ft × 150 ft (9.1 m × 45.7 m) (small) and 80 ft × 825 ft (24 m × 251 m) (large). The complex also includes

SECTION 60

#1732782377140

5270-532: The name of Eastlake Avenue Bridge (also then known as the Tenth Avenue Northeast Bridge ). It got its current and proper name on June 30, 1919. By 1930, the bridge had begun to deteriorate enough for an extensive refit to be ordered: the timber trestle approaches were replaced with ones made out of concrete and steel, the control towers were rebuilt, and the wooden paving was replaced by the first application of open steel-mesh grating in

5355-688: 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

5440-528: 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

5525-740: The project. Some preliminary work was begun in 1906, and work began in earnest five years later under the command of Hiram M. Chittenden . The delays in canal planning and construction resulted in the US Navy building the Puget Sound Naval Shipyard in Bremerton, Washington , which is located across the Sound from Seattle. In early 1909, the Washington State Legislature appropriated $ 250,000, placed under

5610-486: The salt could eventually damage the freshwater ecosystem . To prevent this, a basin was dredged just above (east of) the large lock. The heavier salt water settles into the basin and drains through a pipe discharging downstream of the locks area. In 1975, the saltwater drain was modified to divert some salt water from the basin to the fish ladder, where it is added via a diffuser to the fish ladder attraction water; see below . To further restrict saltwater intrusion, in 1966,

5695-416: The sea lion ; also, many were injured by hitting the walls and gates of the locks, or by hitting boat propellers. The Corps rebuilt the fish ladder in 1976 by increasing the flow of attraction water and adding more weirs : most weirs are now one foot higher than the previous one. The old fish ladder had only 10 "steps"; the new one has 21. A diffuser well mixes salt water gradually into the last 10 weirs. As

5780-469: 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

5865-407: 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

5950-411: 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

6035-413: 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

6120-493: 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,

6205-400: 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

6290-462: 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

6375-542: The water level by 8.8 ft (2.7 m) and drying up more than 1,000 acres (400 ha) of wetlands , as well as drying up the Black River and cutting off the Cedar River salmon run. The Cedar River was rerouted into Lake Washington to provide sufficient water flow for operating the Locks. Additionally the White River was rerouted into the Puyallup River. The Cedar and White Rivers both originally flowed into

6460-416: 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

6545-434: The waterway to the lake, river, or stream where they were born. Once there, the females lay eggs, which the males fertilize. Most salmon die shortly after spawning. The offspring remain in the fresh water until they are ready to migrate to the ocean as smolts . In a few years, the surviving adults return, climb the fish ladder, and reach their spawning ground to continue the life cycle. Of the millions of young fish born, only

6630-453: 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

6715-463: 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

6800-422: 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

6885-416: 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,

6970-422: Was declared complete. While generally a success, the project was not without its problems. Salt water began to make its way upstream toward Lake Union, requiring a system of siphons and flushing mechanisms. Because the Cedar River was the main water source both for the lakes and locks and for Seattle's potable water, at times there were problems maintaining an adequate water supply to maintain lake level and operate

7055-412: 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

7140-456: 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

7225-606: 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

#139860