138 - Weymouth Lowlands : Description

Physical and functional links to other National Character Areas

The chalk escarpment of the Dorset Downs and Cranborne Chase National Character Area (NCA) forms the northern boundary of the Weymouth Lowlands. This ridge provides a backdrop to the NCA and affords panoramic views towards the coast and north into Dorset. Sweeping coastal views in this NCA are dominated by the Isle of Portland lying off the southern tip of the area, linked by Chesil Beach to the mainland. Driving from Bridport on the B3157 towards Weymouth also reveals the well-known view of St Catherine’s Chapel overlooking Chesil Beach and The Fleet.

This stretch of coast forms part of the longer stretch of the Dorset and East Devon Coast World Heritage Site (the Jurassic Coast) and the South West Coast Path, providing strong recreational, cultural and geological links between coastal NCAs. The dynamic coastal geology and maritime cliff habitats along the coast provide a strong ecological link to Marshwood and Powerstock Vales NCA in the east and South Purbeck NCA in the west.

The chalk and limestone geology of the NCA forms part of a wider aquifer system which underlies this and the Dorset Downs and Cranborne Chase NCA to the north. This is a primary source of water for the populations of Weymouth and to the north of the NCA, such as Dorchester and beyond.

Relatively unimpeded coastal processes also link this and adjacent NCAs via long-shore drift and sediment cells. Offshore, the submarine geodiversity and seabed morphology are as varied as on the land. Terrestrial biodiversity is mirrored by an equally diverse suite of reef communities.

Transport links into and through the NCA are generally via a network of small roads linking villages. The A354 from Dorchester is the only major road into the NCA and to Weymouth. A rail link via Dorchester also runs to Weymouth, running parallel to the road.

Distinct areas

• Chesil Beach and The Fleet.

The Weymouth Lowlands today

This NCA is shaped by complex geology and associated landform, but also by its dynamic coast. The exposed chalk escarpment which bounds the NCA to the north slopes expansively into the more intimate coastal plain. The Bride Valley in the west has a particularly intimate feel lent by the rolling landform and patchwork of fields bounded by stone walls. To the east the landform around Osmington is noteworthy for its complexity. Sweeping coastal views are dominated by the Isle of Portland rising abruptly out of the sea, connected to the mainland by the thin strand of Chesil Beach. The Weymouth Lowlands are united by an underlying broad ridge-and-valley pattern of chalk, limestone and clay. The pattern is linked to a large, dome-shaped fold in the rock layers known as the Weymouth Anticline. Portland lies on the southern limb and the hard Portland Limestone dips below sea level at the Bill. To the north, the Portland Limestone dives steeply into the Ridgeway, where it is capped by chalk. In between, hard bands of limestone form ridges inland and headlands at the coast and Fleet shore while soft bands of clay form the vales and bays, including the large expanse of Portland Harbour.

The NCA is predominantly rural and agricultural in nature and has a remote and tranquil appeal. It can feel isolated from the rest of Dorset by the chalk escarpment which bounds it to the north. Limestone ridges are crossed by rectilinear fields, bounded by low, sparse hedgerows, largely without hedgerow trees, or post-and-wire fencing. Arable farming characterises these open ridgetops with panoramic views to the coast and provides important feeding and breeding grounds for farmland birds such as corn bunting and grey partridge. Valley floors have a mixed farming pattern but remain largely treeless and open. Locally, and particularly in the Bride Valley, there are patches of drystone walls, strongly associated with areas where suitable stone is locally and readily available, especially where the Purbeck Beds, Corallian Limestone and Forest Marble outcrop. Soils are thin and brashy, and 76 per cent of the area is classed as Grade 3 agricultural land. There is a trend towards conversion to arable from pasture across the area.

The landscape around the Bride Valley is more varied, wooded and undulating. Woodland patches are characterised by oak, ash and hazel, and often associated with a network of streams. Towards the sea, the landscape is still more strongly undulating with wide views and no trees. Towards Osmington there is an intricate, enclosed landscape of pasture, small fields, irregular hedgerows, woodland and scrub, which rises to the high, open Chaldon Down.

There are two major rivers in the area which run across the ridge-and-valley pattern. These are the rivers Wey and Bride. The River Wey is only 8.9 km long, emerging from the Portland and Purbeck limestone ridge below the South Dorset Downs chalk ridge at Upwey. At Weymouth, the in-filled estuary of the Wey has been extensively built on and the beach ridge is backed by a sea wall and promenade, apart from a section at the northern end of Weymouth Bay where there is a clay cliff (Furzy Cliff) which exhibits landslide activity. The Bride runs through Burton Bradstock and flows across the shingle to the sea. Occasionally fluvial flooding can be a problem alongside tidal flooding at Weymouth and Preston which benefit from sea defences. Breakwaters help to reduce wave action on the Portland Harbour area. The rivers are important sources of water, supplying fish farming and a hydroelectric scheme at Upwey. The area is also underlain by limestone and chalk and forms part of the aquifer network which underlies the Dorset Downs and Cranborne Chase NCA to the north. The nature of the geology means that where chalk or limestone meets impermeable clays springlines and small fens are common. There is an association between the springlines and land use, particularly the position of historic withy beds.

Soil slippage and slumping can also be seen as a result of springlines, especially following high rainfall. Radipole and Lodmoor nature reserves have large areas of reedbed and marshland extending up the Wey Valley. Wetland reserves at the coast and springline flushes throughout the NCA are important. The hillsides around Abbotsbury are covered in a mosaic of ancient landslides that may have lain dormant since the last ice age or before. The back-tilted surfaces created by large rotational slips take on the appearance of enormous terraces which have been mistaken for ancient field systems in the past.

The area has a rich and diverse biodiversity resource exemplified by 1,756 ha of Biodiversity Action Plan (BAP) habitat, and 867 ha of Sites of Special Scientific Interest (SSSI) (7 per cent of the NCA) of which approximately 461 ha (3 per cent of the NCA) are Special Areas of Conservation (SAC), Special Protection Areas (SPA) or Ramsar sites. The majority of the designations are contiguous, providing a strong network of habitats, particularly along the coast. Where gradients steepen along the chalk and limestone ridges, scrub and grazed semi-improved permanent grassland are found, generally calcareous in nature. Windswept cliff-top grassland adorns the soft, unstable cliffs of the coastal strip, supporting a rich mosaic of habitat which is particularly important for invertebrates. The coast and the limestone ridge account for much of the area’s 472 ha of unimproved grasslands, which are particularly rich around Osmington and White Nothe and include the Isle of Portland to Studland Cliffs SAC, designated for maritime vegetated sea cliffs and calcareous semi-natural grasslands. These grasslands support silver-studded blue, chalk-hill blue and Adonis blue butterflies and plants such as green winged orchid, pyramidal orchid, early gentian, early spider orchid, wild cabbage and Nottingham catchfly. A lack of management of some of these sites, principally from a decline in grazing, has led to an increase in gorse and other scrub cover. Chesil Beach and The Fleet, designated as an SAC, SPA and Ramsar site, dominate the coastline. The windswept, rugged nature of the beach contrasts with the gentle lakeside landscape on the inland edge of The Fleet with its mosaic of fields and hedgerows extending down to the water’s edge.

Chesil Beach, a 28-kilometre linear storm beach, is important in the study of coastal geomorphology. The enclosed brackish lagoon of The Fleet is extraordinarily rich in wildlife. Outstanding communities of aquatic plants and animals are present, including the looping snail and a sea slug Tenellia adspersa, both only known from one other British site, and the scaly cricket. These in turn support large numbers of breeding waders and tern, including one of the largest common tern colonies in southwest England, and overwintering waders and wildfowl such as dark-bellied Brent goose. The Fleet is the only significant estuarine fish nursery and breeding area between Swanage and Seaton and is identified specifically as a bass nursery area. The Fleet is also locally important for shellfish, in particular oysters, and a small fishing industry is supported. Flood defences are integral with Chesil Beach for a discrete length adjacent to Chiswell.

The NCA is relatively sparsely settled. There are a few compact nucleated villages, mainly on the lower slopes or near streams, while the ridgetops are almost entirely free of settlement. Farmsteads and hamlets lie generally on the valley sides, commonly quite close together along narrow lanes, with few main roads leading in or out of the NCA. Large farmsteads and manor houses, many dating from the 16th century or earlier, are also found in and around villages. The building style is generally mixed. There is a strong presence of locally derived Portland and Purbeck limestone in villages as well as flint and reed thatched cottages, although brick is also common. Abbotsbury to the west uses the more yellow coloured Corallian Limestone derived from the surrounding hills. Weymouth, a vibrant coastal town in the middle of the NCA, extends inland from its sheltered east-facing harbour, with the historically important Portland Harbour lying between it and the Isle of Portland.

Weymouth is fronted by an impressive Georgian sea front, but more recent urban development and land uses radiate along the main road corridors and associated infrastructure such as pylons is notable. Caravan parks and associated visitor infrastructure and pony paddocks are also more prevalent within the confines of Weymouth, especially to the west, but increasingly evident throughout the NCA. Two wetland reserves – Radipole Lake, fed by the River Wey, and Lodmoor – lie within Weymouth and are important for overwintering and breeding waders. Crookhill Brick Pit SAC in Weymouth is a disused brick pit supporting the highest counts of great crested newts in Dorset. Weymouth and Portland hosted the 2012 Olympic Games sailing events. Preparation for the Olympic Games and mitigation measures arising from the construction of the Weymouth Relief Road enabled a number of regeneration projects to take place and a general enhancement of the Georgian sea front. These included the development of 200 ha of green infrastructure along the Lorton Valley Nature Park and a mix of access and nature reserves as well as a spectacular new geological section through the Purbeck Beds along the Weymouth to Dorchester cycle route.

The NCA is crossed by a network of footpaths, and in particular a 68-kilometre stretch of the South West Coast Path, and is also known for water-based recreation. The geology of the NCA makes it important for study and research into geology, stratigraphy and coastal geomorphology.

The landscape through time

The area is underlain by bands of limestone, mudstone, siltstones and sandstone running in an east- west formation. These are tilted slightly to the east with progressively younger rocks exposed at the coast. Lias Group mudstones and limestones are exposed at the western extremities of the area, with later Jurassic Corallian, Kimmeridgean and Portlandian sediments exposed further east. The early Cretaceous Purbeck Beds sit above the Portland Stone and these are found on the northern edge of the NCA. Later Cretaceous sediments – Greensand, Gault Clay and Chalk – form the Ridgeway at the boundary between the Weymouth Lowlands and the Dorset Downs. The strata were deposited during the Middle to Upper Jurassic and Cretaceous under fluctuating conditions and maintain a record of changing climate and sea depths from relatively deep seas to coastal swamps. Sea levels rose and fell in a series of cycles, depositing deep-water clays, followed by sandstones and finally shallow-water limestones. Significant fossil localities yield abundant invertebrate material as well as vertebrates including marine reptiles such as pliosaurs, plesiosaurs and ichthyosaurs. The coast around Osmington is known for natural oil seepage rising from the seabed. A film of oil can still be seen on the surface of the sea near Bran Point on calm days. The coast around Osmington Mills is also one of the best places to see trace fossils.

About 100 million years ago a large and deep fault formed running between what is now Abbotsbury and Poxwell as a result of the opening of the Channel Basin. It is known as the Abbotsbury Fault. Around the same time significant uplift to the west tilted the entire rock sequence here gently to the east. At about 20-25 million years ago the collision of the African and European plates compressed the rocks here, creating a structure known as the Weymouth Anticline. This folded the bedrock across almost the entire Weymouth Lowlands NCA with an east-to-west axis running roughly parallel with Nottington Lane. Erosion of this structure has created a cross section of the geology across the landscape, destroying the post-Jurassic rock record and creating the distinct geomorphology of the area where the ridges and valleys are aligned with the tilted hard and soft rocks.

The Abbotsbury Fault forms a major boundary at the northern edge of the NCA. It was reactivated during the formation of the Weymouth Anticline, allowing rocks to the south to be thrust upwards while the pressure pushed up the chalk ridge on the northern side. The result is a sudden change in geology across this fault with Upper Greensand and Chalk always on the northern side and much older rocks on the southern side. This boundary creates springlines and the sudden rise in topography that characterises the change from the Weymouth Lowlands to the Dorset Downs.

The influence of the Weymouth Anticline and the Abbotsbury Fault dies out west of Abbotsbury and does not affect the Bride Valley.

Chesil Beach and The Fleet lagoon owe their origin to changing sea levels and landslides through the late part of the last ice age. Around 125,000 years ago sea levels were slightly higher than today, as evidenced by the eastern raised beach on Portland Bill. When sea levels dropped during the final cold period of the last ice age, the west Dorset and east Devon cliffs decayed into vast debris slopes that spilled across the exposed sea floor. Rising sea levels after the ice age (about 10,000 years ago) pushed material onshore but less than 10,000 years ago they also encountered these large, degraded landslides and released huge volumes of chert and flint onto the shorelines. Long-shore drift carried these pebbles east, creating the beach.

Important Mesolithic sites are found along the edge of The Fleet. Pollen analysis shows that during the Neolithic period there was grazing on the high downland and coastal grasslands and cultivation of the valleys, and there is also evidence of early field systems and arable cultivation on higher ground. Continued cultivation on the thin, brashy soils of the limestone ridge caused low soil fertility and subsequent crop failure: Mesolithic skeletons showing signs of starvation have been found here, testament to the relative poverty of the soils and biodiversity compared with the Fleet area. Neolithic long barrows are in evidence, such as Hell Stone near Portesham. Iron-age forts are also present, such as at Chilcombe. Roman villa sites are found throughout and there is evidence of a temple near Preston. The area of Weymouth was used as a harbour to supply goods for Dorchester.

It is likely that the present settlement pattern of a mixture of nucleated villages concentrated in the valleys or on the lower slopes and scattered farmsteads throughout became established by the 10th century. The Ridgeway Hill Viking burial pit is a mass grave of Viking men executed by local Anglo-Saxons and gives a glimpse into the turbulent history of this period.

A Benedictine abbey was established at Abbotsbury in the mid-11th century. The substantial market town of Abbotsbury, the base for a successful fishing industry, grew up around the abbey. The abbey was destroyed in 1538 during the Dissolution of the Monasteries. The nearby and prominent St Catherine’s Chapel was spared and later used as a lookout.

By the 12th century two competing ports were established across a narrow channel near Portland Harbour, Weymouth and Melcombe Regis. After the foundation of new boroughs in the 13th century both flourished. They grew rapidly as a base for fishing and for the exportation of wool to western France and importation of corn and wine from Gascony. It is thought that Melcombe Regis was one of the first towns to suffer the Black Death in the 14th century.

In 1571 the two ports were united by an Act of Parliament. The fortunes of Weymouth declined as Poole Port further along the coast grew. The rise in popularity in the 1760s of sea bathing revived Weymouth and saw the development of its Georgian sea front. The White Horse at Osmington was carved in 1808 in honour of King George III whose regular visits to Weymouth meant it became known as ‘the first resort’. It remained a modest seaside resort until the 19th century. The development of the railway encouraged leisure visitors on a larger scale, and its steady inland expansion began. In the 1850s new maritime defences were built and breakwaters enclosed Portland Harbour, coinciding with the establishment of Portland Naval Base as a coaling station opposite the French naval base at Cherbourg.

Evidence of medieval field patterns survives on the poorer land of the slopes and higher ground indicating that until the 14th century arable farming was extensive, combined with sheep grazing on the downland and coastal grasslands. The Black Death and other epidemics and climate change in the 14th century saw a contraction in the local population and deserted villages, evidence of which can still be seen at places such as Portesham, and in relict farming terraces. From the 14th century grazing increased and the most difficult land to plough was abandoned, but the mix of arable and pastoral farming boosted production and encouraged the growth of larger farms.

Most fields are of a rectilinear nature following a north-south grain, dating from Parliamentary enclosure, although to the west there are less regular field patterns which are thought to represent earlier enclosure from strip fields and some common land. There was an attempt to drain The Fleet and reclaim the land for agricultural use during the 17th century, and while this failed sluices and drains remain.

The area around Weymouth and The Fleet was important during the First and Second World Wars. The Fleet was used for testing military equipment such as the ‘bouncing bomb’. This is a nationally important defence landscape with lines of antitank cubes, pillboxes, battery emplacements and observation posts, especially in the hills behind Abbotsbury.

After the Second World War the area became valued for its tranquillity and rural nature and in 1957 sixty per cent of the area was designated as the Dorset Area of Outstanding Natural Beauty (AONB). Tourism has remained important and the infrastructure to accommodate this has increased accordingly, with caravan parks a prominent feature along the coast. Weymouth and its support infrastructure have expanded, radiating along main transport routes, including the completion of the Weymouth Relief Road. Rurally there has been a tendency away from pasture to arable production with some removal of hedgerows to produce larger rectangular fields.

This coastline was designated as the West Dorset Heritage Coast in 1972 for its natural beauty and access for visitors and in 2001 as part of Dorset and East Devon Coast World Heritage Site.