Marple Locks: Water Levels, Gravity and a Flight of Sixteen

On the south-eastern edge of Greater Manchester, the Peak Forest Canal leaves the high stone aqueduct over the River Goyt and climbs a wooded hillside in sixteen deliberate steps. These are the Marple Locks, a flight that lifts the canal about 209 feet (64 metres) in just over a mile, and they are one of the clearest places in England to watch a canal deal with the one thing water will not do on its own: run uphill. The flight and the aqueduct below it are on Day 2 of our Canals and Railways in the Industrial Revolution tour, after Salford Quays and before the Anderton Boat Lift.

Why elevation is the canal problem

A canal is a staircase of flat ponds. Each stretch of water, called a pound, has to be level from end to end, so wherever the ground rises the engineer has three choices: follow the contour round the hill, cut or tunnel through it, or climb it. The Peak Forest Canal was authorised by Act of Parliament in 1794 to carry limestone from the hills around Dove Holes in Derbyshire down towards Manchester, and its route ran straight into this problem. Its upper level sits on the high ground near Marple; its lower level has to cross the deep valley of the Goyt and continue north to meet the Ashton Canal at Dukinfield.

The consulting engineer, Benjamin Outram, worked with Thomas Brown as resident engineer. Their answer was in two parts. The lower canal was carried across the Goyt on the Marple Aqueduct, three stone arches standing around 100 feet (30 metres) above the river, and the change of level between the aqueduct and the upper canal was taken by locks. The canal’s committee twice asked Outram to reconsider how many locks the climb needed before sixteen was settled.

The aqueduct is worth a look in its own right. Its lower stonework is red sandstone and its upper courses a much paler stone, and it is the highest canal aqueduct in England. It is Grade I listed and a scheduled monument. Only Thomas Telford’s Pontcysyllte Aqueduct in Wales, which the tour crosses by boat later in the first week, stands higher above its river.

How a lock chamber works

A lock is a short, walled chamber with gates at each end and a set of sluices, called paddles, that let water in or out. To take a boat uphill, the chamber is emptied to the lower level and the bottom gates opened. The boat enters, the bottom gates close behind it, and the top paddles are wound up so water from the pound above flows in. As the chamber fills, the boat rises with it. When the water inside matches the level above, the pressure on the top gates is equal on both sides, and they can be pushed open with the long timber balance beams. Going downhill, the sequence runs in reverse.

The principle is simple, but the numbers at Marple are not small. The chambers are a little over 23 metres long and around 2.4 metres wide, built for narrowboats, and each one raises the canal by roughly 13 feet (4 metres). That makes them among the deepest narrow locks in the country. A historical survey of the flight calculated that an average chamber holds around 49,000 imperial gallons, about 220 tonnes of water, and every one of those tonnes passes downhill each time a boat goes through.

The Marple Locks as a sequence

Sixteen locks in a mile means a lock roughly every hundred metres, so the flight works as a sequence rather than a set of separate structures. Each lockful drawn from above runs down into the pound below, then on to the next lock. Outram kept the locks separate rather than joining them into a staircase, which meant boats could pass one another between chambers and less water was used, and he made the pounds between the locks wider than a boat needed. That extra width is a reservoir: it lets each pound give up a full chamber of water without dropping so low that the next boat runs aground. Overflow weirs beside each lock carry surplus water down the hill when the pounds are full.

The flight also reads differently as you climb. The lower eight locks run through woodland with little housing nearby, locks 9 to 12 sit beside a park, and the final four rise steeply and close together through the town to Marple Junction, where the Macclesfield Canal joins the Peak Forest just beyond the top lock. Local historians note small details along the way: a footbridge at the tail of every lock, carved keystones with weathered faces, and a gargoyle at Lock 8 said to caricature Thomas Brown, who had a reputation as a hard taskmaster.

Why are the Marple Locks numbered from the bottom?

Because that was the convention the builders followed: Lock 1 is beside the aqueduct and Lock 16 is at the top. The Marple Local History Society records the local explanation that numbering downhill was thought to be unlucky. Whatever the reason, it means boaters heading towards Manchester count down, and walkers climbing from the aqueduct count up.

A tramway, a shortage of money and Posset Bridge

The locks were the last part of the canal to be finished. The upper level opened for trade in August 1796 and the aqueduct was filled with water in May 1800, but the company ran short of funds before it could build the flight. Samuel Oldknow, the cotton manufacturer who was the canal’s largest shareholder, and Richard Arkwright Junior, who provided much of its finance, were left with a canal in two halves. For several years a temporary tramway carried goods up and down the hillside between them, and cargo was moved between wagons and boats at each end.

Oldknow had a particular stake in the top of the flight, where his lime kilns stood beside the canal. The top four locks, 13 to 16, opened in October 1804, and the whole flight was open by November 1805. The story of the opening is attached to Posset Bridge, which carries the Stockport road over the canal beside Lock 13. Worried that the bridge would not be ready in time for his boat, Perseverance, to be first through the new locks, Oldknow is said to have treated the workmen to possets, a hot drink of milk curdled with ale, to speed them on. The bridge has three openings: one for the main canal, one for a short branch to the lime kilns that has since been filled in, and a narrow horse tunnel that let towing horses pass under the road while the boat was worked through the lock.

Peak Forest Canal and regional industry

The flight existed to move heavy, low-value material cheaply. Limestone came down from the quarries at Dove Holes on the Peak Forest Tramway, a gravity-worked line about six miles long, to the canal basin at Bugsworth. From there it travelled by boat as stone, or after burning in kilns as quicklime, used for building mortar, for agriculture and for industry across the Manchester area. Coal came up the canal to fire the kilns. Every boat on that trade had to pass through all sixteen Marple Locks.

Railways eventually took the canal’s business. A railway cutting was made at Marple in 1862, and the line passes beneath the lock flight with less than a metre between the tunnel roof and the canal bed. Sidings near Lock 1 allowed cargo to move between rail and water. The tramway and Bugsworth Basin closed in the 1920s, and by the early 1960s the lower canal, including the Marple flight, was impassable.

Campaigning by the Peak Forest Canal Society and the Inland Waterways Association, who wanted to keep the Cheshire Ring of canals open as a cruising route, led to restoration, and the lower Peak Forest Canal reopened on 1 April 1974. The aqueduct itself had already been repaired in 1963 and 1964. The flight is now maintained by the Canal & River Trust and used almost entirely by pleasure boats.

What is the difference between a lock flight and a staircase?

In a flight, every lock has its own top and bottom gates with a pound of water between neighbouring locks; in a staircase, the top gate of one chamber is the bottom gate of the next, with no pound in between. Marple is a flight. A staircase saves space on a steep slope but must be worked in a fixed order and uses more water. The tour shows both: Neptune’s Staircase on the Caledonian Canal near Fort William lifts boats through eight joined chambers.

How much walking is involved at Marple?

The full flight is a climb of about 64 metres over 1.6 kilometres on a towpath, so walking all of it is a steady uphill mile. The lower locks run through woodland, and the top four rise steeply beside roads in the town. The tour is rated Level 2 (Moderate), with three to five hours of activity on most days and walks of up to 8 kilometres, sometimes on uneven ground, and the aqueduct and the bottom locks can be seen with very little climbing.

Will the Marple Locks be open to boats in 2027?

They are scheduled to be. The Canal & River Trust has announced a full closure of the flight from 4 January to 12 March 2027 to replace gates and repair Lock 10, with further work at Locks 2, 3 and 4, which falls before the April 2027 departure. Earlier work in 2017 replaced gates and repaired masonry along the flight, part of a continuing programme to keep two-hundred-year-old locks working.

Seeing water management in the landscape

Once you know what to look for, the hillside at Marple explains itself. The broad pounds are the canal’s working store of water, the weirs show where it overflows, the wide change bridge near the bottom marks where the old tramway once crossed, and the horse tunnel at Posset Bridge shows how the boats were moved before engines. The same day continues to Northwich, where the Anderton Boat Lift solves a similar change of level without locks at all, lifting boats between the Trent and Mersey Canal and the River Weaver in water-filled caissons.

Further north the tour cruises the Lancaster Canal, built to follow the contours so it could avoid climbing for long stretches, a useful contrast with the sixteen steps at Marple. Our overview of Britain’s canals and railways and their industrial heritage shows how each of these structures fits into the wider story. At Marple the story is a simple one, told in stone and water: how a canal climbed a hill, one lockful at a time.