National Character Area 114

Thames Basin Lowlands - Description

The Thames Basin Lowlands today

The Thames Basin Lowlands lies at the southern end of the London Basin. Finger-shaped, it stretches from the London suburbs of South Norwood in the east to Hale on the Surrey/Hampshire border in the west. The landscape is gently undulating but flat in places, for instance within the river valleys. The underlying geology is mostly London Clay with small outcrops of sandstone between Esher and Cobham. Around Sutton and Croydon, there is a small outcrop of the Chalk bedrock that underlies the North Downs, fringed with sediments, and there are sand and gravel river terraces and alluvium along the river valleys. Several rivers including the Wey, Mole, Hogsmill and Wandle meander northwards through this lowland landscape to meet the Thames, forming part of its catchment. Rivers such as the Wey have changed their course during the Quaternary period due to river capture. All have been heavily modified in places, ranging from the straightening of the river course to the installation of concrete banks and culverts. The Wey and Mole are the least developed and their broad, wide valleys support riparian habitats, scattered trees and wet woodlands of alder, oak, lime, willow and poplar, as well as hazel and holly.

The NCA is well-wooded, predominantly broadleaved, with oak, or oak/ash on the more base-rich soils in the west and oak/birch more dominant on the less fertile acidic soils in the east. The largest blocks of woodland are concentrated around East Horsley, Fetcham and Oxshott. The west of the area is more sparsely wooded where ancient semi-natural woodland is an important habitat and feature of the landscape, including the veteran pollarded oaks of Ashtead Common. Towards the east and London, much of the woodland is mixed and the result of afforestation or natural woodland regeneration on heaths.

In the west, the landscape is mostly pastoral. Farmland is interspersed with woodlands and shaws (narrow belts of woodland that stretch out along field boundaries), villages and farmsteads. Fields are small-to-medium-sized, irregular shaped and bounded by hedges, resulting from a complex mix of enclosure from woodland in the medieval period, from medieval farmland strips and, in the late 18th and 19th centuries, from heathland. Occasional hedgerow trees include oak, ash and field maple. Closer to urban areas, these have been replaced by wire fencing or are neglected, gappy and in poor condition. Horse paddocks are a common feature. Field trees in straight lines frequently indicate the position of a lost hedgerow.

To the north-east towards London, the farmland character becomes heavily fragmented by increasing suburbia and the major transport links that cross the NCA such as the M25, A3 and A24. This densely populated part of the NCA includes the Greater London suburbs of Croydon, Mitcham, New Malden and Sutton as well as the north Surrey fringes of Esher, Epsom and Ewell. Towards the south west, with the exception of Guildford, it is more sparsely populated with a varied settlement pattern ranging from large towns such as Leatherhead, with housing estates to scattered houses and farmsteads. Almost nowhere in the NCA can be considered tranquil but throughout the NCA, the remaining commons, parks and river valleys are highly valued for their green space and recreational opportunities.

The landscape through time

The Thames Basin Lowlands NCA lies at the most southerly point of the London Basin; a shallow bowl formed 40 to 60 million years ago during the Alpine orogeny, the period of mountain building that formed the Alps. Over the millennia, this became filled with marine and riverine deposits. Some 55 million years ago, a sequence of shallow marine sediments was deposited under semitropical climatic conditions, to form the Thames Group sediments (London Clay), which is the thickest and most widespread Tertiary deposit within the London Basin. During the Quaternary Period (last ice age), rivers including the Wey changed their course due to river capture. Quaternary deposits in the area include sands and gravels forming river terraces, and alluvium along the valley floors.

Transport links have been a dominant feature within the NCA since the Roman conquest when Stane Street, now the A24, was built to connect London with the south coast. However, settlement of the area during this period does not seem to have been extensive, although the remains of a Romano-British villa have been found on Ashtead Common. The area was however densely settled in the medieval period. Land use was a complex mix of heathland, arable strips and ancient woodland with assarted fields relating to a varied settlement pattern of isolated farmsteads and houses, hamlets and small villages. Hunting and recreational parks with grand houses were established across the area, including Henry VIII’s Nonsuch Palace. The area west of Croydon was used for growing lavender and in a time when foul air was associated with disease, the area became a popular retreat from London.

Guildford probably had its origins in the early Saxon period, located at a crossing point on the River Wey. Its central position for passing traffic across the Wey or between London and the coast ensured its prosperity and it became the county town of Surrey, by the 17th century boasting a grammar school, alms houses and a hospital.

Although shallow, the rivers of the NCA were used from the early Middle Ages as a source of power for driving mills and Domesday records mills on the banks of the Hogsmill. Industry grew up alongside the Mole, Wandle and Wey. The construction of the Wey Navigation canal from the 17th century onwards allowed boats to reach Guildford.

During the 18th century, villages such as Cobham, Esher, Ripley and Send grew up along what is now the A3, providing stopping points for coaches as they travelled between London and Portsmouth. Industries such as copper, ironworking and snuff production grew up around the area’s rivers towns. The Wandle was probably the most industrialised, housing the famous William Morris mill and the Liberty factory at Merton Abbey Mills. Improved transport links added to the prosperity and many fine houses were built or older ones renovated, such as the Palladian mansion at Clandon.

Until the 19th century, the character of the NCA remained predominantly rural, Guildford being the most significant settlement. The arrival of the railways brought fast transport links into London, allowing people to work in central London but live on the periphery several miles from their place of work. When towns such as Croydon, New Malden and Sutton were linked to central London by rail, there was a significant influx of population to the area and agriculture and horticulture gave way to extensive urban development. Today commuting to central London is still an important feature of the NCA.

Industrial activities and their infrastructure, including London’s first airport at Croydon, led to the area being a target for bombing during the Second World War. A defence line was constructed and features such as pill boxes survive in the west. After the war, land around both Greater London and Guildford was designated Green Belt to prevent further urban expansion. Under the Local Government Act 1963, the London Boroughs were reorganised and parts of the NCA including Croydon, Sutton and Merton which were previously part of Surrey, became part of Greater London.