River Avon (Bristol)

River Avon (Lower Avon)
Bristol Avon
River
The Avon Gorge and Clifton Suspension Bridge
Name origin: Welsh afon meaning river
Country	England
Counties of England	Gloucestershire, Wiltshire, Somerset, Bristol
Tributaries
- left	River Malago Brislington Brook River Chew Corston Brook Midford Brook River Frome, Somerset Paxcroft Brook River Biss Semington Brook Cocklemore Brook River Marden Brinkworth Brook Woodbridge Brook Tetbury Avon
- right	River Trym River Frome, Bristol Siston Brook River Boyd Lam Brook Bybrook Gauze Brook
Cities	Chippenham, Melksham, Bradford on Avon, Bath, Bristol
Source	Old Sodbury
- coordinates
Mouth	River Severn
- location	Avonmouth, Bristol, West of England, England
- coordinates
Length	120 km (75 mi)
Basin	2,308 km² (891 sq mi)
Discharge	for Bath
- average	21.98 m3/s (776 cu ft/s)
- max	310 m3/s (10,948 cu ft/s)
- min	2.48 m3/s (88 cu ft/s)
River system	River Severn

The River Avon (pronounced /ˈeɪvən/) is a river in the south west of England. Because of a number of other Rivers Avon in England, this river is often also known as the Lower Avon or Bristol Avon. The name Avon is a cognate of the Welsh word afon meaning "river" (f is pronounced as v in Welsh).

The Avon rises near Chipping Sodbury in Gloucestershire, dividing into two before merging again and flowing through Wiltshire. In its lower reaches from Bath to the River Severn at Avonmouth near Bristol the river is navigable and known as the Avon Navigation.

Etymology

The name Avon is a cognate of the Welsh word afon meaning "river" (f is pronounced as v in Welsh). "River Avon", therefore, literally means "River River". This explains why several English rivers have the name Avon.^[1] The County of Avon that existed from 1974 to 1996 covering the Avon valley, including Bristol and Bath, was named after the river.

Course

The Avon rises near Chipping Sodbury in Gloucestershire, between the villages of Old Sodbury and Acton Turville. Running a somewhat circular path, the river drains east and then south through Wiltshire. Its first main settlement is the village of Luckington, two miles (3 km) inside the Wiltshire border, and then on to Sherston. At Malmesbury it joins up with its first major tributary, the Tetbury Avon, which rises just north of Tetbury in Gloucestershire. This tributary is known locally as the Ingleburn, which in Old English means 'English river'. Here, the two rivers almost meet but their path is blocked by a rocky outcrop of the Cotswolds, almost creating an island for the ancient hilltop town of Malmesbury to sit on.

After the two rivers merge, the Avon then turns south east away from the Cotswolds and then quickly south into the clay Dauntsey Vale, where it is joined by the River Marden, until it reaches the biggest town so far, Chippenham. The wide vale is now known as the Avon Vale, and the river flows on via Lacock to Melksham, then turns north-west through Bradford on Avon, where the centre of the town grew up around the ford across the river Avon, hence the origin of the town's name ("Broad-Ford"). This was supplemented in Norman times by the stone bridge that still stands today. The Norman side is upstream, and has pointed arches; the newer side has curved arches. The Town Bridge and Chapel is a grade I listed building. It was originally a Packhorse bridge, but widened in 17th century by rebuilding the western side.^[2] On the bridge stands a small building which was originally a chapel but later used as a town lockup.

The Avon Valley between Bradford on Avon and Bath is a classic geographical example of a valley with all four forms of ground transport is found: road, rail, river, canal. The river passes under the Avoncliff and Dundas Aqueducts and at Freshford is joined by the Somerset River Frome. Avoncliff Aqueduct was built by John Rennie and chief engineer John Thomas, between 1797 and 1801. The aqueduct consists of three arches and is 110 yards long with a central elliptical arch of 60 ft (18.3 m) span with two side arches each semicircular and 34 ft (10.4 m) across, all with V-jointed arch stones. The spandrel and wing walls are built in alternate courses of ashlar masonry, and rock-faced blocks.^[3] The central span sagged soon after it was built and has been repaired many times.^[4] The Dundas Aqueduct was built by the same team between 1797 and 1801 and completed in 1805. James McIlquham was appointed contractor.^[5] The aqueduct is 150 yards (137.2 m) long with three arches built of Bath Stone, with Doric pilasters, and balustrades at each end.^[6] The central semicircular arch spans 64 feet (19.5 m); the two oval side arches span 20 feet (6.1 m).^[7] It is a grade I listed building,^[8] and was the first canal structure to be designated as an Scheduled Ancient Monument in 1951. The stretch of river below and above the aqueduct, where it is joined by Midford Brook, is used by the Bluefriars of the Monkton Combe School Boat Club up to six days a week since at least the 1960s.^[9]

It then flows past Claverton Pumping Station, which pumped water from the River Avon into the canal, using power from the flow of the river. The pumping station is located in a pump house built of Bath Stone, located at river level. Water is diverted from the river by Warleigh Weir, about 200 yd (180 m) upstream. The water flows down a leat to the pumping station, where it powers a water wheel, 24 ft (7.3 m) wide and 17 ft (5.2 m) in diameter, with 48 wooden slats. At full power the wheel uses 2 tons (2 tonnes) of water per second and rotates five times a minute.^[10] The water wheel drives gearing which increases the speed to 16 rpm. From here, cranks drive vertical connecting rods which transfer the energy to two 18 ft (5.5 m) long cast iron rocking beams. Each rocking beam in turn drives an 18 in (0.5 m) diameter lift pump, which also take their supply from the mill leat. Each pump stroke raises 50 imperial gallons (230 litres) of water to the canal.^[10] In 1981, British Waterways installed two 75 horsepower (56 kW) electric pumps just upstream from the station and presented the diesel pump to the Kennet and Avon Canal trust for preservation.^[11]

Palladian Pulteney Bridge and the weir at Bath

The Avon then flows through Bathford, where it is joined by the Bybrook River, and Bathampton, joined by the Lam Brook at Lambridge in Bath and then it passes under Cleveland and Pulteney Bridges and over the weir. Cleveland Bridge was built in 1826 by William Hazledine,^[12] owner of the Coalbrookdale Ironworks, with Henry Goodridge as the architect,^[13] on the site of a Roman ferry crossing. Named after the 3rd Duke of Cleveland, it spans the River Avon at Bathwick, and enabled further development of Georgian Bath to take place on the south side of the river. It was designed by architect Henry Goodridge to take the traffic of his day, horse drawn vehicles and pedestrians, and was constructed using Bath Stone and a cast iron arched span. Pulteney Bridge was completed in 1773 and is designated by English Heritage as a grade I listed building.^[14] The bridge was designed by Robert Adam, whose working drawings are preserved in the Sir John Soane's Museum,^[14] and is one of only four bridges in the world with shops across the full span on both sides.^[15] It is named after Frances Pulteney, heiress in 1767 of the Bathwick estate across the river from Bath. Pulteney approached the brothers Robert and James Adam with his new town in mind, but Robert Adam then became involved in the design of the bridge. In his hands the simple construction envisaged by Pulteney became an elegant structure lined with shops. Adam had visited both Florence and Venice, where he would have seen the Ponte Vecchio and the Ponte di Rialto. But Adam's design more closely followed Andrea Palladio's rejected design for the Rialto.^[15] Pulteney Bridge stood for less than 20 years in the form that Adam created. In 1792 alterations to enlarge the shops marred the elegance of the façades. Floods in 1799 and 1800 wrecked the north side of the bridge, which had been constructed with inadequate support. It was rebuilt by John Pinch senior, surveyor to the Pulteney estate, in a less ambitious version of Adam's design. 19th-century shopkeepers altered windows, or cantilevered out over the river as the fancy took them. The western end pavilion on the south side was demolished in 1903 for road widening and its replacement was not an exact match. In 1936 the bridge became scheduled as a national monument, with plans being made for the restoration of the original façade. The restoration was completed in time for the Festival of Britain in 1951,^[16] with further work being carried out in 1975.^[15] In 2009 Bath and North East Somerset council put forward plans to ban vehicles from the bridge and turn it into a pedestrianised zone.^[17]

The river is then joined by the Kennet and Avon Canal which connects with the Avon just below the weir at Bath Locks. Together with the Kennet Navigation and the River Thames it provides a through route for canal boats from Bristol to London. From this point downstream it is known as the Avon Navigation.

Navigation

Weir at Swineford Lock.

The Avon then flows through Keynsham towards Bristol. For much of its course after leaving Wiltshire, it marks the traditional boundary between Somerset and Gloucestershire. For most of this distance the navigation makes use of the natural river bed, with six locks overcoming a rise of 30 feet (9 m). From Bath to Netham Lock where it divides into the New Cut and the Floating Harbour is 12 miles (19 km). The stretch is made navigable by the use of locks and weirs.

Weston Lock on the outskirts of Bath is in what now forms the Newbridge. Weston cut is a man made channel, opened in 1727, for boats to approach and pass through Weston lock, which created an island between the cut and the river weir, which became known as Dutch island after the owner of the brass mill established on the river side in the early 18th century.^[4]

Kelston Brass Mill overlooking Saltford Lock.

Kelston Lock and weir have permanent moorings above and below them. The Riverside Inn and Saltford Marina are also close by. Saltford Lock and weir are overlooked by the remains of the Kelston Brass Mill, which was working until 1925. It is a grade II listed building.^[18] Alongside the lock is a pub, whose garden extends over the lock to the small island between the lock and weir. The lock was opened in 1727 and destroyed in 1738 by rival coal dealers to stop the use of the river for transportation.^[4] In its heyday, between 1709 and 1859 Swineford had an active brass and copper industry around the Swineford Lock which were served by the river which also provided water power for the cloth industry,^[4] as did the River Boyd, a tributary which flows into the Avon near Bitton. Keynsham Lock opened in 1727.^[4] Just above the lock are some visitor moorings and a pub, on an island between the lock and the weir. The weir side of the island is also the mouth of the River Chew. Hanham is the last tidal lock,^[6] after which the river is joined by Brislington Brook.

Netham lock is the point at Netham in Bristol at which boats from the River Avon, gain access to Bristol's Floating Harbour. Construction started in 1804 to build the tidal New Cut, where it is joined by the River Malago, and divert the River Avon along the Feeder Canal to the harbour; a system designed and built by William Jessop and later improved by Isambard Kingdom Brunel.^[19] A weir carries the river into the New Cut and boats use the adjacent lock. Access to the harbour is only possible during the day when the lock keeper will open the gates unless the water level in the river between Netham and Hanham is above or below the level of the harbour.^[20] Netham Lock and the weir form part of Bristol's flood defence mechanisms and it was announced in December 2008 that they would be upgraded as part of the £11 million City Docks Capital Project.^[21]

Bristol Bridge from Castle Park

The River Avon in Bristol, looking towards Bristol Bridge with Welsh Back on the left. Boats of the Bristol Ferry Boat Company are moored in the foreground, and the spires of St Nicholas, All Saints' and St Mary le Port churches can be seen in the distance.

In central Bristol, where the river is tidal, it is diverted from its original course onto the New Cut, a channel dug between 1804 and 1809 at a cost of £600,000.^[22] The original course is held at a constant level by lock gates (designed by Jessop) and is known as the Floating Harbour. The Floating Harbour is protected by a 1870s replacement for Jessop's locks. This unusual dock has a tentacled plan resulting from its origins as the natural river course of the Avon and its tributarys, the River Frome and Siston Brook, and is intimately entwined with Bristol's city centre as few docks are. As a result of this, the Floating Harbour is one of the more successful pieces of dockland regeneration, with much of the dockside now occupied by residential, office and cultural premises, and the water area heavily used by leisure craft. The Floating Harbour gave the port an advantage by enabling shipping to stay afloat rather than grounding when the tide went down. Downstream of central Bristol the river passes through the deep Avon Gorge, spanned by Brunel's Clifton Suspension Bridge, the river is tidal and is navigable by sea going vessels at high tide but drying to a steep sided muddy channel at low tide. It was largely the challenge of navigating this section that sealed the fate of the Floating Harbour as commercial docks, and saw them replaced by docks at Avonmouth where the Avon joins the Severn estuary.

Before reaching its mouth it is joined by the River Trym at Sea Mills which was the site of Portus Abonae a Roman port, and passes under the Avonmouth Bridge which carries the M5 motorway. The main span is 538 ft (164 m) long, and the bridge is 4,554 ft (1,388 m) long, with an air draught above mean high water level of 98.4 ft (30 m). The river then serves two major dock areas. The Royal Portbury Dock on the southern side of the mouth of the river. The deepwater dock was constructed between 1972 and 1977, and is now a major port for the import of motor vehicles. The Royal Portbury Dock has the largest entrance lock into any UK port, accommodating vessels up to 41 m (135 ft) beam, 290 m (951 ft) length and 14.5 m (48 ft) draft. The Avonmouth Docks are on the north side of the river and are one of the UK's major ports for chilled foods, especially fruit and vegetables. The first dock at Avonmouth, Avonmouth Old Dock, was opened in 1877. It was acquired by the Bristol Corporation in 1884. In 1908, a much larger dock, the Royal Edward Dock, was opened. The docks form part of the Port of Bristol and were operated by the Port of Bristol Authority, part of Bristol City Council, until 1991, when the council granted a 150 year lease to the Bristol Port Company.

Biodiversity

The river is important for its dragonfly communities, with a strong population of Scarce Chaser (found in only six other areas in England),^[23] together with a strong population of White-legged Damselfly.^[24] Red-eyed Damselfly is also found.

The river is also important for aquatic plants, including Loddon Pondweed.

The Avon Gorge has been designated as a Site of Special Scientific Interest because it supports some rare fauna and flora, including species unique to the gorge. There are a total of 24 rare plant species and two unique trees: the Bristol and Wilmotts's whitebeams.^[25] Other notable plants include Bristol Rock-cress,^[26] Bristol onion,^[26] Spiked Speedwell,^[27] Autumn Squill^[27] and Honewort.^[28][29] Other areas along the river which have this designation include Bickley Wood,^[30] Cleeve Wood, Hanham for its large population of Bath Asparagus (Ornithogalum pyrenaicum).^[31] Stidham Farm near Keynsham contains at least At least 2 metres (7 ft) of Pleistocene terrace-gravels, consisting of limestone clasts mainly, but also with Millstone Grit, Pennant Sandstone, flint and chert clasts. The site is of considerable importance for studies relating to the possible glaciation of the area, and of the terrace stratigraphy, particularly as it is one of only two accessible terrace deposits in this part of the Avon valley.^[32] Newton Saint Loe is also listed for geological reasons as it represents the only remaining known exposure of fossiliferous Pleistocene gravels along the River Avon. In conjunction with other sites within the wider area, they have aided the development of a scientific understanding of the history of early glaciation within South West England.^[33]

At Horseshoe Bend, Shirehampton the wooded cliff and a narrow salt marsh are supported by rocks of Devonian sandstone and Carboniferous limestone, overlain by with Triassic Dolomitic conglomerate. The site's principal interest and the reason for its designation as an SSSI is the presence of a population of the True Service-tree (Sorbus domestica) growing on the cliffs. This tree is nationally rare in Britain, and this site hosts the largest known population in England. Other notable species of Sorbus here are the whitebeams Sorbus eminens and Sorbus anglica, both of which are also nationally rare in Britain. The nationally scarce Large-leaved Lime (Tilia platyphyllos) also occurs, and herbs include Field Garlic (Allium oleraceum) and Pale St. John's-wort (Hypericum montanum). The saltmarsh vegetation, which lies at the base of the cliff, is predominantly made up of Sea Aster (Aster tripolium) and English Scurvygrass (Cochlearia anglica). There are however two nationally scarce vascular plant species here as well - Slender Hare's-ear (Bupleurum tenuissimum) and Long-stalked Orache (Atriplex longipes).^[34]

The tidal reaches of the River Avon provide habitat for waterbirds, with 64 species having been recorded up to 2004,^[35] including 21 species of shorebird,^[36] and 13 species of gull.^[37]

History

The river Avon had been navigable from Bristol to Bath during the early years of the 13th century but construction of mills on the river forced its closure.^[38]

The Bristol Avon Navigation, which runs the 15 miles (23.3 km) from the Kennet and Avon Canal at Hanham Lock to the Bristol Channel at Avonmouth, with 2 locks,^[39] was constructed between 1724 and 1727, following legislation passed by Queen Anne,^[40] by a company of proprietors and the engineer John Hore of Newbury. The first cargo of 'Deal boards, Pig-Lead and Meal' arrived in Bath in December 1727.^[4] It is now administered by British Waterways.

Route and points of interest

See also

• Other Rivers Avon
• Photograph of the Clifton Suspension Bridge from Brunel Way
• Photograph of the estuary at Avonmouth
• Rivers of the United Kingdom

References

External links

• The Bristol Avon Catchment Abstraction Management Strategy
• Portishead and Bristol Lifeboat