Navigation Lock, The Cutts, Coleraine, Co.Londonderry

Cutts Lock is a scheduled monument on the left bank of the River Bann, just downstream from the west end of the flood gates at the Cutts, near Coleraine. It is scheduled rather than listed, as this is considered a more appropriate form of protection. It is an excellent example of mid-19th century canal engineering, robustly built to withstand the frequent Bann floods, and its interest is enhanced by its juxtaposition with the adjoining quay, mill race, weir, fish traps and flood gates. Historically, it is significant as part of the last navigable waterway undertaking carried out in Ireland in the 1800s, and for its association with the engineer John MacMahon and the Commissioners of Public Works.

The lock is a single-chamber structure — Lock 1 of the Lower Bann Navigation — built by the Commissioners of Public Works. MacMahon, the waterway's designer, had originally intended the lock to sit on the opposite bank of the river, but its position was switched to the Castleroe side because of the proximity of a public road. Excavation began in the late 1840s and the first stone of the chamber floor (the invert) was laid on 19 June 1850. Work was completed in 1851. The Commissioners' plan of 1858 records the chamber as measuring 130 feet by 20 feet with a fall of 6 feet 4 inches, separated from the river by a masonry pier measuring 220 feet by 20 feet. James Barton, writing in 1859, noted that because this pier was shorter than usual, there was an increased risk of boats being swept over the adjoining weir during floods. The lock has appeared on all editions of the Ordnance Survey maps from 1850 onwards.

The sides of the chamber are built of randomly sized dressed stone blocks laid in courses and coped with large dressed sandstone blocks. A vertical metal ladder runs down the middle of the wall on the river side. There are pairs of timber gates at both ends, with timber footplates supported on cantilevered steel frames on their upstream sides. Water flow is controlled by land sluices set into the gate emplacements on the upstream sides of both sets of gates, rather than by gate paddles. The casing housing each sluice mechanism bears the cast legend "MacAdam Brothers & Co, Belfast". Vertical stop plank grooves run up both sides of the chamber, just below the lower gates and just above the upper gates. A depth gauge calibrated in feet and inches is set into the south-east gate emplacement, and a vertical ladder has been set within the north-east emplacement. A flight of concrete steps leads down to the water just beyond the north-west gate. In 2010, automatic depth gauges were fitted at both ends of the lock.

The pier separating the lock chamber from the river is faced along its river (east) elevation with masonry and has rounded ends. Its upstream end has been extended in concrete to facilitate access to the adjoining flood gates, which were erected in the early 1930s.

Setting

Several related features of note survive in the immediate environs of the lock.

Lock keeper's house

A single-storey building aligned north–south on the landward side of the lock, with a modern extension along its east side, a pitched artificial slate roof, cement-rendered walls and square-headed openings with modern frames. The premises are enclosed by a metal security fence. Although the lock was completed in 1851, the original lock keeper's house was not built until 1857. It was demolished around 1951 to make way for the present building immediately to its north-west. This replacement eventually fell into disrepair but was completely refurbished in 2004–05 as Waterways Ireland's regional headquarters, at which point the east-side extension was added.

Quay

A slightly curved squared rubble quay runs for approximately 150 metres along the left bank just upstream from the lock, with a tarmacked hardstand behind it separated from the road by a random rubble wall. At its north-west end is a modern Waterways Ireland pontoon aligned parallel with the quay and accessed at its upstream end by a hinged metal gangway. The quay was built by the Commissioners of Public Works as part of the Navigation Scheme between 1848 and 1851. The Commissioners' plan of 1858 shows it as a 480-foot-long, slightly curved structure immediately upstream from the lock. Its construction required the removal of the remains of the derelict Castleroe Mill — a five-storey building erected around 1808, whose two waterwheels had powered eight sets of millstones. The mill was gutted by fire around 1820 and is shown as a roofless shell on the 1830 Ordnance Survey map; all vestiges were removed by the Commissioners in 1847 in advance of the quay's construction. In 2003–04, Waterways Ireland added a pontoon at the downstream end of the quay for boats awaiting passage through the lock.

Mill race

This channel runs for approximately 200 metres from the north-west end of the quay to the downstream end of the former Department of Agriculture Fisheries Research premises just beyond the north-west end of the lock complex. Water enters at its upstream end through a segmental dressed stone arch let into the quay wall. Immediately below this are the vertical emplacements for a sluice gate, though the gate itself is missing. Just beyond this point, a concrete wall blocks the channel. The sides of the channel are partly lined with random rubble masonry. Approximately 65 metres from its intake, the channel is crossed by a concrete bridge giving vehicular access to the Waterways Ireland offices, and 50 metres beyond this bridge the channel is piped under the entrance to the former fisheries premises.

The mill race was constructed alongside the lock in 1850–51. The construction of the Lower Bann Navigation had allowed for the future erection of water-powered mills at the downstream ends of most of the locks, with the upper levels of the channels into the locks doubling as headraces, but in the event no mill was ever built at any of the locks. The channel is marked as "intended mill race" on the Commissioners of Public Works' 1858 plan of the Cutts.

Weir, fish traps and flood gates

Immediately south-east of the lock lies a natural waterfall known as the Cutts, an important salmon and eel fishery since prehistoric times. Its present name apparently dates from around 1613, when an artificial cut was made through the rock shelf to facilitate the passage of boats and timber downriver. Fish traps are recorded at the Cutts from the 1680s, with the Honourable the Irish Society holding the fishing rights.

The mid-1850s masonry weir runs from the right bank to four eel traps, and from the traps the 1930s flood gate emplacement runs to the south-east end of the lock. Between 1847 and 1851, the Commissioners of Public Works erected a masonry weir across the river as part of the Navigation Scheme to maintain sufficient depth of water above the lock, incorporating fish traps and elver slips into the structure. In 1931, the Ministry of Finance replaced the west section of the weir with four vertical sluice gates to allow better regulation of water levels, particularly during floods. The new emplacement was designed by Percy Shepherd of the Department of Works and Public Buildings, and the contractor was Walter Scott and Middleton Ltd. The gates themselves were supplied by Ransome and Rapier of Ipswich and are of F.G.M. Stoney's patented counterweighted type; similar flood gates exist at Portna and Toome. Affixed to the outside face of the west pier of the emplacement is a rectangular cast-iron plaque reading "Ransomes / Ipswich, 19 & 31 England / Rapier Ltd". Around 2006, Rivers Agency installed electric motors to replace the manual system for raising and lowering the gates, which also necessitated the addition of a gantry across the navigable channel to carry the electric cabling to the motors.

In 1996, salmon trapping at the Cutts was suspended under agreement with the Department of Agriculture (Northern Ireland) Fisheries Division under the EU Salmonid Enhancement Programme. In 2006, the Irish Society's right to net eels was leased to the Lough Neagh Fishermen's Co-operative Society Ltd; in the interests of eel conservation they have deliberately not exercised these rights, although eels are still trapped for stocking purposes upstream.

Today, Waterways Ireland is responsible for the operation of the lock, and Rivers Agency for the operation and maintenance of the weir and flood gates.