118 - Bristol, Avon Valleys and Ridges : Description

Physical and functional links to other National Character Areas

The western and north-western edge overlooks the flat Lower Severn Levels of the Severn and Avon Vales NCA, with further views across the estuary to the Forest of Dean and Wales. To the south, the Mendip Hills NCA rises from the Chew Valley. Outstanding viewpoints of Bristol and the surrounding area are gained from Brandon Hill and Cabot Tower. To the east and the south, the Cotswold scarp and Mendip Hills rise in an abrupt boundary, while at the south-eastern corner of the NCA the southern end of the Cotswolds and eastern end of the Mendips merge into an area of ‘confused undulations’.

The River Avon cuts a steep-sided valley through the area from the east, having passed through the Severn and Avon Vales NCA and Cotswolds NCA. It is joined by the Chew near Keynsham, which rises on the Mendips’ edge, and the Frome, which flows from the Cotswold edge at the north-east of the area to form the 2.5 km spectacular Avon Gorge in the centre of Bristol. Other streams and rivers in the south-east flow eastwards to join the Avon outside the NCA, and the Yeo on the south-western edge flows out across the North Somerset Levels and Moors directly to the sea. The River Severn connects this NCA with others that border the estuary through fluvial and tidal processes up and down the estuary.

The area is well connected to neighbouring NCAs and beyond by the rail network and the M4 and M5 motorways that cross the area, intersecting at the northern edge of Bristol, which provide fast connections north, south, east and west.

Distinct areas

• City of Bristol

The Bristol, Avon Valleys and Ridges today

Characterised by alternating ridges and broad valleys, with some steep, wooded slopes and open rolling farmland, the large urban expanse of the City of Bristol, with its dramatic limestone gorge of the River Avon, dominates the central and western part. The area is strongly defined by the NCAs that border it, with the scarps of the Cotswolds and Mendips in neighbouring NCAs to the east and south, and provides part of the landscape setting for the Cotswolds and Mendip Hills Areas of Outstanding Natural Beauty (AONB). To the west, the area overlooks the flat Lower Severn and North Somerset Levels and, beyond that, the Severn Estuary and Wales. Occasional high points break through creating landmarks, for example Dundry Hill to the south of Bristol, at 233 m in height with 360° views and, within the City of Bristol itself, Brandon Hill, topped by Cabot Tower, which provides a platform for a panoramic view of the city and beyond to the hills in the distance.

The varied landforms and settlement patterns of the NCA are strongly influenced by its diverse geology and complex geological history. The area has also made a considerable contribution to the history of the development of geology as a science through the studies of William Smith, the ‘Father of English Geology'”�.

Rivers such as the Chew and Avon have carved gorges in the older, more resistant rocks, while those such as the Frome have formed wide, shallow valleys in the softer, younger ones. The rivers have been heavily modified in urban areas. The limestone-derived soils are predominantly brown rankers and argillic brown earths. On the clays, poorly draining gleys are common, whereas the Coal Measure soils are more acidic. This variability in soil type is a result of the complex underlying geology and is reflected in the range of habitats that have developed and the opportunities for human land use.

The higher ground and steep scarps of the limestone ridge along the western edge extend from the Yeo Valley towards Thornbury; sandstone outcrops are present in places. The dramatic Avon Gorge cuts through the ridge at Bristol, spanned by the historic Clifton Suspension Bridge, rising about 100 m from the tidal River Avon to Observatory Hill on the eastern side and Stokeleigh Camp to the west. The gorge has natural cliffs and quarry exposures of Carboniferous Limestone, which are of great geological interest, and, together with the screes, scrub, pockets of grassland and adjacent woodland, it supports an exceptional number of nationally rare and scarce plant species. Further south the ridge forms the distinctive landscape of the Failand Hills. Ashton Court, the grandest of the parklands, makes good use of the limestone landform and provides a wide range of recreation opportunities for the surrounding population. To the west, the ridge falls – often steeply – to the levels. Along the scarp, woodland predominates; above the scarp there is open country, where large fields and low, rectilinear hedges lie around scattered farmsteads and houses, with mixed woodland blocks and patches of arable.

Concentrations of ancient woodland are found at Leigh Woods on the gorge”�s western side, to the north-east of Congresbury along the Failand Ridge (for example Lime Breach Wood near Cadbury Camp) and at Lower Woods SSSI near Wickwar. Elsewhere, the woodlands are much smaller and fragmentary, often on the steeper land, with their great variety reflecting the overall complex geology. In the former mining areas, they are augmented by planting on reclaimed colliery tips. Parkland such as at Tyntesfield and Ashton Court form characteristic features south and west of Bristol, where the woodlands and mature and exotic trees bring a distinctive local character.

The ridge contrasts with the gentle clay vale of the Frome north of the Avon; here the landscape is more open, particularly on the lower ground, giving way to an intricate field pattern mixed with woodland on the surrounding higher land. There are few hedgerow trees, and pylons are conspicuous. The settlement pattern is indistinct; there are some large villages, but many houses are scattered along the sparse network of roads and there are isolated farmsteads. At the northern edge of the area there is another, more undulating, type of landscape, as the land rises to the Cotswolds. To the east, the land is more rolling, and views of the Cotswold scarp begin to dominate. New settlements are particularly noticeable since there is little woodland.

South of Bristol, the land falls to the Yeo and Chew valleys, where Chew and Blagdon lakes, within the Mendip Hills AONB, are prominent features near the foot of the Mendip scarp. These lakes also provide a valuable source of drinking water and are designated as Drinking Water Protected Areas under the Water Framework Directive (WFD). Both lakes and the surrounding land are also of conservation value and provide recreational fishing, windsurfing and sailing. Chew Valley Lake is an SPA due to its internationally important population of shoveler ducks and nationally important numbers of gadwall, tufted duck and teal. The surrounding species-rich lowland meadow adds to the nature conservation value of the area. Long barrows, iron-age hill forts and the Wansdyke (a linear defensive earthwork) provide evidence of how long this area has been settled.

Merging with the eastern part of the Mendip Hills is a rolling landscape of hill-top pastures, deep river valleys, many stone villages and hamlets, and farmsteads linked by narrow, hedged lanes. There are often contrasts in the textures of the grassland, with rough grassland on the steeper slopes and lusher pastures in the valley bottoms. The gentler slopes are more open; the hedges are lower and there is more arable. Threading through this south-eastern landscape are the remains of the mining industry characterised by occasional spoil heaps, straggling settlements and small irregular fields including smallholdings. Midsomer Norton, Radstock and Paulton form large settlements that were once strongly associated with mining but are now commuter towns for Bath and Bristol.

At the heart of the NCA is the City of Bristol – the oldest parts and those with the most distinctive townscapes being the old city centre, the docks and Clifton, with its downs. The conurbation spreads down the river to the industrial complex of Avonmouth in the adjacent Severn and Avon Vales NCA. To the south-west, a boundary is formed by the Avon Gorge, and the river continues through the city. To the south and east, housing extends to Dundry Hill and is broken by fragments of farmland. Bristol Airport dominates the hill top along from Dundry. In the north and north-east, development is dispersed across a wide area and the motorways are prominent. Modern residential development, extending as far as Yate, is broken by open farmland. The strongest landscape structure is represented by formal landscapes such as Stoke Park and Oldbury along the lower Frome Valley and by modern commercial landscapes such as Aztec West and Cribbs Causeway. With its mix of urban and rural landscape, the provision of green infrastructure and quality green space is highly valued by the City of Bristol and surrounding unitary authorities in order to retain its attractiveness for inward investment. The NCA has a high level of accessible green space per head of population (Accessible Natural Greenspace Standard data, Natural England)

A short coastal stretch of the NCA occurs between Clevedon and Portishead, where limestone cliffs descend to the Severn Estuary. The Victorian seaside resort of Clevedon hosts the only structurally intact Grade I-listed pier in the UK, opened in 1869 to enable passengers to board steamers to south Wales. The town is well connected to the heart of Bristol by public transport and the National Cycle Network.

Although there is much uniform 20th-century housing across the area, many of the older village and town buildings in grey Carboniferous or Lias limestones or Jurassic oolites survive. There is much variation in the building stone used (Strategic Stone Study: A Building Stone Atlas of Avon, English Heritage, 2011); for example, sandstone is prevalent in the north, while white, rather bleak Lias limestone is common in the south-east within the Midsomer Norton-Radstock area. Around Nailsea, stone boundary walls of Pennant Sandstone known as Nailsea flats are found; where this stone is used in buildings it tends to be rendered. With a wide choice of attractive materials, including Bath Stone and Cotswold Stone, many of the mansions, gentry houses and churches are fine buildings in mellow tones, but there are also unspoilt village and town streets such as the centre of Chipping Sodbury. The principal roads radiate from the old centre of Bristol. Much modern settlement is close to these corridors or to the M4 and M5 motorways.

Bristol is one of the most affluent cities in the UK and has a strong manufacturing and service sector, providing employment for the settlements in the NCA and beyond. It is a popular destination for overseas and domestic visitors, as it is easy to reach by road, rail and air and is close to Bath, another popular tourist destination.

The landscape through time

The varied topography of this NCA is related both to the nature of the underlying rocks and to the amount of erosion to which they have been subjected. In general, the harder Palaeozoic rocks form areas of moderately high relief (such as Broadfield Down near Bristol Airport) that exceed 125 m above sea level. The solid geology consists mainly of Upper Palaeozoic (Devonian Sandstone and Carboniferous Limestone) and Mesozoic (Triassic-Middle Jurassic) rocks. The extreme north of this NCA also features important Silurian rocks with igneous intrusions. The Carboniferous Limestone has been quarried in the area since prehistoric times, ranging from small extractions to large, modern quarries such as at Wickwar, Tytherington and Chipping Sodbury.

Repeated geological periods of inundation and drying have resulted in sedimentation forming fossil-rich strata from a number of geological periods. The Coal Measures were formerly extensively mined but the last pit closed in 1973 and exposures today are usually confined to small scrapes on disused, landscaped tips. Writhlington SSSI is a notable exception, and fossil Coal Measure plants and insects can still be collected from the shales. The area around Keynsham is famous for its ‘Blue Lias’ fossils.

During the early Jurassic, parts of the area remained as islands, and Lower Lias deposits occurred here. The youngest Jurassic sediments exposed in the area are approximately 190 to 175 million years old and out-crop on Dundry Hill. Here Middle-Upper Lias siltstones and limestones are capped by pale oolitic limestones. These marine sediments are well known for their abundant and well-preserved ammonite and brachiopod fossils.

The high ground in the west and south of the area was settled at an early date. There is good evidence of Neolithic activity, for example the long barrows and stone circle at Stanton Drew. The ridges continued to be of importance through the Iron Age not least as the sites of hill forts, of which Cadbury Hill is the best known. The lower-lying clay vales had attracted settlement too, but it is likely that the heavier ground, for instance along the Frome Valley, was not cleared until later.

By Roman times, many parts of the area had been settled for a long time and the importance of the Avon was evident from the port at Sea Mills. Villas lay either side of the Avon Valley and on the fertile soils north of the Mendip Hills. After the Romans left, significant ‘dark-age'”� settlements were present on the eastern edge. The Saxon takeover occurred in the 6th century and the impressive earthworks of the Wansdyke, cutting across the ridges south of Bristol, date from this era.

By the later Saxon period, important centres existed at Pucklechurch, Chew and elsewhere, and the town of Bristol was already established by the time of the Norman Conquest.

The area was dominated by the port of Bristol, which expanded rapidly into England”�s second largest city from the 12th century, exporting corn and especially wool and cloth, and importing wine and wool from western France. As a result, lesser towns like Thornbury and Chipping Sodbury also prospered. The area”�s settlement, as developed by the 11th century and later centuries, displayed a great variation, from villages surrounded by open fields to medieval farmsteads and hamlets with early enclosed fields in the clay vales, all interspersed with patches of common and woodland. There was, however, extensive open downland on the western limestone area, and a large royal forest lay around Kingswood, up to 500 km2 at its peak (Kingswood Chase was carved out of the forest in the early 13th century).

Following the 14th century and, in particular, the rapid population decline that followed the disaster of the Black Death, open fields began to be enclosed; however, many remained in use in the north of the area, and much of the open downland was unenclosed until the 19th century. Grazed calcareous grasslands have largely been ploughed up or improved in the last 50 years; those that remain are generally restricted to very shallow soils or the steep hillsides that are less accessible to farm machinery.

A coal industry was present in the Middle Ages, and it developed on a large scale from the mid-18th century. Small pits were dispersed across the countryside, often fuelling local industries such as the brass foundry at Keynsham and the smelting works at Wormley. The Somerset Coalfield was significant enough to justify the construction of the Somerset Coal Canal. William Smith was one of the surveyors on the canal and some of the mines, and it was here that he developed his theory of stratigraphy. The pits were active well into the last century, but there was rapid decline following nationalisation and the last pit closed in 1973. Today, most of the obvious evidence has disappeared and the tips have been largely reclaimed.

During the medieval period, Bristol had become important enough as a port to sponsor John Cabot’s 1497 expedition of discovery to America in the founding of Newfoundland. In the post-medieval period, Bristol expanded to become Britain”�s second port based on its trade in sugar cane, tobacco, rum, cocoa and slaves; indeed, Bristol”�s trade in slaves exported to the colonies brought great wealth to the city. Exported goods such as tobacco were processed in warehouses and factories, visible alongside the docks today. In the 18th and 19th centuries the city continued to prosper and expand on the basis of its trade, engineering and other industries. The wealth that it generated is evident in the legacy of wealthy merchants”� houses that remains today, including the area around King Street, Queen Square, St Michael”�s Hill and Clifton village. The 19th century witnessed renewed efforts to deepen the Avon and remodel and extend the city docks. Isambard Kingdom Brunel helped to attract further investment into the area. Brunel did more than anyone to shape the character of modern Bristol; his legacy includes Clifton Suspension Bridge, the SS Great Britain and Temple Meads station. Despite this, the city lost the transatlantic trade to Liverpool and other ports, Avonmouth taking its place as a major port from the early 20th century.

The legacy of Bristol’s wealth is also evident in the parks and mansions that surround the city, such as Dyrham Park, Dodington House, Tyntesfield, Blaise Castle and Ashton Court. These parklands are nationally important for their diversity and range of architectural styles and planting. The parklands now provide biodiversity interest in addition to significant areas of comparative tranquillity and recreation.

In the 20th century, Bristol expanded even more rapidly to include the Avonmouth port and oil refining complex (within the Severn and Avon Vales NCA). Issues of water supply to the expanding city led to the creation in the 1950s of Chew Valley Lake, by flooding farmland, to supplement the by-then insufficient Blagdon Lake, which had been created in the 1890s. These lakes are now of significant conservation interest for wildfowl, invertebrates and plants and are surrounded by important neutral grasslands that support a range of rare plant species, such as the green-winged orchid.

The M4 and M5 motorways through the area were constructed between 1962 and 1977. The airport at Lulsgate Bottom became Bristol International Airport in 1997 (now named Bristol Airport). Residential, commercial and light industrial areas, such as Cribbs Causeway and Aztec West, have extended into the surrounding countryside, and major new roads have been developed. Expansion, notably at Emersons Green, Bradley Stoke and Cribbs Causeway, has resulted in areas of farmland being lost, and the landscape character of these areas has altered significantly. The growth has affected the whole NCA, and many of the outlying settlements such as Yate developed both as their own employment centres and as dormitories of Bristol. The growth of settlement has probably been the main influence on the rural landscape. The decline and greening over of the coal industry, the construction of major reservoirs and the loss of substantial tree cover as a result of Dutch elm disease have also been significant.

Future development within Bristol and South Gloucestershire is focused near existing services. Bristol City Council is not planning any urban extension, but South Gloucestershire Council is proposing significant development on the northern (the majority of which is housing) and eastern (mostly employment) fringes of Bristol, together with expansion at Yate and Thornbury, largely to accommodate new housing. Bath and North East Somerset Council is focusing on development in urban areas and brownfield at Keynsham and the larger settlements in the Somer Valley within this NCA, while North Somerset Council is concentrating its urban development outside this NCA. The planned expansion of Bristol Airport may significantly impact on the tranquillity and traffic of this NCA and the adjacent Mendip Hills NCA.