108 - Upper Thames Clay Vales : Analysis: Landscape Attributes & Opportunities

Analysis supporting Statements of Environmental Opportunity

The following analysis section focuses on the landscape attributes and opportunities for this NCA.

Further analysis on ecosytem services for this NCA is contained in the Analysis: Ecosytem Services section.

Landscape attributes

Low-lying clay-based flood plains coursed by the River Thames and its dense network of tributaries and ditches, often lined by willow, reed and, in the Aylesbury Vale and Cotswold Water Park, native black poplar.

Justification for selection:

• Lowest elevation is 39 m AOD. Rivers such as the Thame have shallow gradients (Thames Corridor Catchment Abstraction Management Strategy, Environment Agency, 2004).
• River Thames and its tributaries drain the Vales, their headwaters flowing off the Cotswolds to the north or emitting from the springline along the Chilterns and Downs escarpments.
• Numerous upper tributaries of the Thames flow off the Cotswolds dipslope into a vale bounded by the Midvale Ridge. The Midvale Ridge constrains the river network within a narrow corridor, giving rise to a high density of watercourses and ditches. The Thames breaks through at Oxford to pass into a wider vale to the south where watercourses and ditches are at a lesser density than the northern vales.
• Willows have historically been pollarded. Ditches full of reeds are particularly characteristic in the wetter areas north of the Midvale Ridge.
• Native black poplars are distinctive of the Aylesbury Vale and Cotswold Water Park.
  Long and wide views across open fields, small and occasional woods. High ground in adjacent NCAs provides a backdrop and there are strong linear features in the form of hedgerows, tree belts, ditches and roads.
• Woodland cover is only 3 per cent of the NCA. Historically, the area was more wooded, with more extensive wet woodland and mature elm trees.
• The Great Western Community Forest is a focus area for sustainable regeneration although not particularly well wooded.
• The Chilterns, Berkshire and Marlborough Downs and Midvale Ridge rise up abruptly from the Vales in adjacent NCAs. The Midvale Ridge is a much smaller feature than the Chilterns and Downs.
• Parliamentary enclosure determined much of the field pattern in this NCA. As a result, boundaries are straight and defined strongly by hedgerows and roads.

Superficial deposits create undulating topography across much of the area. Better drained land on higher ground is often settled and cultivated. A legacy of mineral extraction gives rise to geological exposures, numerous waterbodies supporting wildfowl and a nationally important complex of marl lakes.

Justification for selection:

• Superficial deposits cover 40 per cent of the NCA including alluvium and gravel terraces.
• Arable land is concentrated on higher ground, away from the wetter flood plain where soils are heavy to cultivate.
• SSSI and Local Geological Sites aim to conserve important geological exposures in redundant quarries and small pits.
• Where mineral extraction takes place, pits naturally fill with water. There are over 100 lakes comprising the Cotswold Water Park, creating a distinctive landscape and popular with bird-watchers. Limestone gravels from the Cotswolds give rise to marl formation.

In the river corridors, grazed pasture dominates with limited areas of historic wetland habitats including wet woodland, fen, reedbed and flood meadow. Wet grassland supports breeding birds. Snake’s head fritillary flowers in internationally important meadows.

Justification for selection:

• Wet ground conditions and heavy clay soils discourage cultivation in many places, giving rise to livestock farming. Most grassland is improved or semi-improved.
• This NCA has around 7,200 ha of flood plain grazing marsh, 1,700 ha of wet woodland and 1,300 ha of lowland meadows and 600 ha of fens. There are also rich and extensive ditch systems around Otmoor, the upper River Ray, and the River Thames near Wallingford and in the Lower Windrush Valley.
• Some river valley meadows and pastures are important for wading birds, including regionally important breeding numbers of lapwing, snipe, curlew and redshank, and large wintering numbers of lapwing and golden plover. Scrapes have been created in some areas to encourage such birds, as for example around the River Ray in Buckinghamshire.
• Limited fields have retained their species-richness, including traditional flood meadows where soil fertility has been sustained by seasonal flooding. There are two areas of flood meadow designated for their importance at a European level as Special Areas of Conservation (SAC).
• North Meadow and Clattinger Farm SAC supports over 90 per cent of the country’s fritillary population.

A mosaic of mixed agriculture, ponds and small woods. Relict orchards remain on the Greensand.

Justification for selection:

• Supports typical farmland wildlife such as brown hare, bats, barn owl and skylark.
• Fertile soils associated with the limited area of Greensand adjacent to the Chilterns and Berkshire and Marlborough Downs have historically been a focus for orchards.
• The Aylesbury Vale was known for its plums known as Aylesbury prune.

A regular, planned field pattern defined by boundaries of thorn hedgerows, often with mature hedgerow trees, stone walls near the Cotswolds and straight roads. Smaller fields are found around villages while large arable fields are particular to the Vale of White Horse.

Justification for selection:

• Field pattern was largely set out by Parliamentary enclosure and is well-ordered and defined by straight boundaries and roads. Earlier smaller, irregular fields persist around villages.
• Large arable fields with a less dense hedgerow network characterise the Vale of White Horse. This field pattern resulted from the enclosure of medieval strip fields.
• Mature hedgerow trees, including veterans, are found in many hedges. Elm was once a mature hedgerow tree characteristic of this area but now it is a shrub component only.
• Blackthorn and hawthorn were the typical hedge species of Parliamentary enclosure.
• Near the Cotswolds, the availability of Cotswold stone has led to stone walls in this locality.

Relict features of ancient Royal Hunting Forests of Bernwood, Braydon and Wychwood include embankments, veteran trees and clusterings of small ancient woods. Designed parkland landscapes are sparsely scattered, including Blenheim Palace World Heritage Site.

Justification for selection:

• Historic Royal Hunting Forests comprised a mosaic of open grassland and woodland. Small ancient woodlands, veteran trees and embankments are relict features of these Royal Hunting Forests. Mature field oaks are a feature south of the Midvale Ridge. Bernwood lay around Brill, Wychwood east of Witney and Braydon near Swindon.
• Braydon Forest supports a patchwork of broad-leaved woodland blocks (often ancient semi-natural or replanted) and small fields delineated by mature, species-rich hedgerows. Woodland cover is locally high here compared with the wider NCA.
• There are 38 Registered Parks and Gardens (many are associated with the Oxford Colleges). Buscot, Claydon and Hartwell are examples. These large estates most likely evolved from the ancient Royal Hunting Forests.
• Part of Blenheim Palace World Heritage Site lies in this NCA. It was designated in 1987 in recognition of the international significance of the architecture of its buildings and the landscaped grounds. The famous landscape designer Lancelot ‘Capability’ Brown worked at Blenheim to create ‘one of the greatest examples of naturalistic landscape design’ (Nominations to the World Heritage List, UNESCO, 2008). Blenheim influenced designs elsewhere in England and abroad.

Pasture preserves historic earthworks, including ridge and furrow and, concentrated in the Aylesbury Vale, deserted medieval villages. Roman roads, castles and historic bridges are striking features.

Justification for selection:

• Nationally important survivals of ridge and furrow include those at West Hanney, Denchworth, Lodgershall, Hogshaw and Creslow.
• Deserted medieval villages include those at Quarrendon, Fleet Marston and Creslow.
• There are 245 Scheduled Ancient Monuments.
• Roman roads include Ermine Way and Akeman Street.
• Castles include Shirburn and Wallingford.
• River crossing points have long been a focus for settlement and there is a rich history around bridges in this NCA. Wallingford and Abingdon are noted for historic bridges.

Brick, tile, timber and thatch are traditional building materials across the area, combined with Cotswold stone near the Cotswolds and occasional clunch and wichert near the Chilterns.

Justification for selection:

• Local clay enabled bricks and tiles to be made for local use.
• Stone available from the Cotswolds was used to construct buildings and walls in that locality. Near the Chilterns, clunch (a chalk rock) was occasionally used.
• Wichert was a plaster made by mixing chalky marl with straw or earth. It was often colour-washed, as seen at Haddenham and Cuddington.
• Thatch is seen across the area and characteristic of many villages such as Stanton Harcourt and Sutton.

Historic settlement is found sparsely dispersed on higher ground and exceptionally at river crossing points such as Abingdon. Large urban areas comprise Aylesbury and outskirts of Oxford and Swindon, plus growing towns dispersed across the NCA such as Didcot, Bicester, Witney and Thame. A web of A roads connects major settlement, while the M4 and M40 pass through.

• Settlement has mostly been avoided in areas liable to flooding, except at river crossing points such as Standlake. Large towns of Abingdon and Wallingford are historic crossing points.
• Aylesbury and Swindon are major urban centres, having been a focus for recent growth.
• Industrial uses include Didcot Power Station and car factories at Swindon and Oxford.
• The dispersed nature of settlement means that there are A roads connecting large towns. Numerous A roads emanate from Oxford, Swindon and Aylesbury.

Landscape opportunities

• Conserve historic features in the flood plains, including traditional flood meadow, pasture, pollarded willows, historic bridges and Scheduled Monuments.
• Conserve wetland habitat in the flood plains, from species-rich ditches to lowland meadow to wet grassland supporting breeding birds including waders.
• Restore and create wet grassland, ponds and fens in the flood plains. Create new woodlands in places where enclosure of the landscape does not negatively impact upon valued views and does not impinge upon open habitats such as wet grassland providing for breeding waders.
• Manage and restore extraction pits to avoid negative impacts upon the landscape. Create wetland habitat as hydrological conditions sustainably allow, providing for a range of wildlife and contributing positively to the wider mosaic of habitats in the landscape.
• Maintain hedgerows, hedgerow trees and stone walls as strong landscape features which also contribute to the ecological network. Maintain characteristic native black poplars in the Aylesbury Vale and Cotswold Water Park.
• Conserve veteran trees in fields, hedgerows and woods. Ensure there are successor trees and retain deadwood where possible.
• Conserve small woodlands, particularly ancient woodlands and semi- natural woodlands. Explore opportunities to restore woodland within the historic Royal Hunting Forests and consider new woodlands and tree screens as part of development. Avoid new woodlands and overgrowth of hedgerows where they will obstruct valued views or otherwise enclose an open landscape, including grasslands supporting waders.
• Maintain the mix of agriculture and the mosaic of farmland habitats. Consider ways to increase heterogeneity of the arable landscape of the Vale of White Horse, for example ponds, grass strips, beetle banks and non-cultivated field corners. Restore and create orchards and restore semi- natural habitats associated with historic Royal Hunting Forests in order to enhance the farmland habitat mosaic and conserve historic land use.
• Conserve the built and natural heritage of Registered Parks and Gardens, including Blenheim Palace World Heritage Site. Assess non-registered parklands to determine the need for conservation and designation.
• Encourage continued use of traditional building materials. Where possible, integrate with conservation of geological exposures at extraction sites.
• Conserve historic settlement pattern and historic buildings. Manage the expansion of settlements such as Swindon and Aylesbury.