Somerset Landscape Character Assessment

Geologically, Somerset is one of the most diverse areas in Britan, with its underlying geology giving rise to distinctive contrasts in landform. The limestone Mendip Hills in the north of Somerset enclose lower-lying landscapes of the levels and moors to the south-west, and the rolling limestone and sandstone ridges with incised valleys to the south-east. The Mendip Hills are primarily composed of limestone formed during the Carboniferous period around 350 million years ago. These limestone formations, along with the surrounding clays and sandstones, were laid down in shallow seas that once covered much of southern Britain. The Mendip Hills also feature significant karst landscapes with limestone caves, including Cheddar Gorge, created by water eroding the soft rock over time.

The lower-lying levels and moors are largely made up of alluvial deposits, including muds, silts, and peats, which were laid down in the last 12,000 years. These deposits were formed by the flooding of rivers and the subsequent settling of fine sediments, leading to the characteristic marshy landscape of the levels and moors. Together, the levels and moors form the second largest area of lowland peat in the UK.

The distinctive hill ranges of the Quantock Hills are formed of ancient sedimentary rocks of predominantly sandstones and slates, which date back to the Devonian period around 400 million years ago. These rocks were formed in a variety of marine environments, with rugged folded structures shaped by tectonic forces over time. Outcrops of volcanic rocks contribute to the varied geology.

The Blackdown Hills, in the south-west, are formed of sandstone of the Upper Greensand Formation. The Greensand plateau is a unique geological feature, that extends into Somerset from Devon, and is one of the finest, most extensive examples of Greensand plateau in Britain. Acidic loamy and clay soils overlie the bedrock in this area.

Geology along the coastline consists of both Triassic and Jurassic strata, including limestones, mudstones and shales, which were deposited in coastal environments around 200 million years ago. These rock formations are rich in fossils, providing valuable clues about the ancient environments and ecosystems that once existed in the region.

The underlying geology and subsequent weathering processes have created the distinctive landform and drainage patterns seen across Somerset today.

The Mendip Hills in the north of Somerset form a distinctive elevated plateau, descending to scarp slopes to the south which are incised by a number of gorges and combes. The central plateau descends to a gentle dipslope, extending towards Bath and North East Somerset to the north. The rising Mendip Hills and their south-facing scarp slopes enclose the lower-lying landscape of the levels and moors, which form a flat area extending across the north-west and centre of Somerset.

The levels are formed of a coastal clay belt, which sits at slightly higher elevation than the moors. The moors, located inland from the levels, act as a basin and capture water draining from hills and high ground. Most of the levels and moors is located within Flood Zones 2 and 3, and seasonal flooding forms a regular influence. The Rivers Tone, Yeo, Isle and Parrett drain into the moors, with a complex drainage pattern reflecting centuries of human intervention, ranging from the linear ditches delineating fields (rhynes) through to modern systems of embanked rivers, spillways, sluice gates and pumping stations.

The coastline to the west of the levels is formed of gentle sandy beaches and dunes, with the rising promontory of Brean Down in the north forming an isolated outlier of the Mendip Hills group. The River Parrett estuary, with low-lying areas of salt marsh and mudflats, extends across the centre of the Somerset coastline, midway between the Mendip Hills and Quantock Hills.

A series of limestone hills rise dramatically from the levels and moors, forming distinctive skylines. This includes Brent Knoll, the Isle of Wedmore, Pennard Ridge, Polden Hills, the High Ham and Somerton ridge and localised ridges and hills extending south from the Mendip Hills.

The sandstone foothills and plateau of the Quantock Hills contain the south-western edge of the levels. The narrow upland sandstone plateau is focused in the north and west of the Quantock Hills, forming a dramatic escarpment in views from the west. The south and east of the Quantock Hills is formed of a series of hills and footslopes incised by steep combes, contributing to the dramatic relief of the landform. Landform descends to a more gently rolling series of foothills and lowland coastal hills to the east and north-east of the Quantock Hills. The coastline to the north of the Quantock Hills is formed of dramatic cliffs rising from the sea, occasionally enclosing small, sheltered coves of rocky, shingle and sandy beaches. Fossil-rich geological exposures extend across this part of the coastline.

The hills of Exmoor rise beyond the western boundary of Somerset. The landscape extending between the Quantock Hills and Exmoor comprises a series of steep river and stream valleys, following the River Tone, Doniford Stream and their tributaries, dividing elevated areas of rolling foothills. Landform descends to the Vale of Taunton to the south, which forms a relatively broad floodplain between the foothills of Exmoor to the north and the Blackdown Hills to the south. The River Tone passes through the Vale of Taunton, draining to the moors to the east.

The northern escarpment of the Blackdown Hills encloses the southern edge of the Vale of Taunton. Further south, landform rises to the Greensand plateau of the Blackdown Hills, which extend beyond Somerset and into Devon. The Yeovil scarplands extend east and north-east from the fringes of the Blackdown Hills, forming a series of steep scarp slopes with hills. Areas of Greensand plateau, scarp slopes and hills in the south-west of Somerset are divided by tributary valleys, which drain these areas of higher ground into the lower-lying landscape of the levels and moors. These valleys follow the Rivers Brue, Isle, Fivehead, Parrett, Broad, Cam, Cary and Cale.

In the east of Somerset, a series of ridges rise above the lower-lying broad valley landscapes to the west, transitioning to the Greensand hills which extend into Wiltshire to the east. Another transitional landscape of slopes and valley heads extends between the fringes of the Mendip Hills in the west and the River Frome valley to the east.

The River Frome valley extends across the north-east of Somerset, forming a gentle shallow upper valley, descending to a more steeply incised valley in the north. Elevated areas of Greensand Hills rise to the south-east of the River Frome Valley and extend further east into Wiltshire. The distinctive escarpment along the western edge of these hills encloses the east of the upper River Frome valley.

The variations in land use, farming patterns and vegetation cover are a function of the complex interrelationship of physical factors, including geology, soils, drainage, and microclimate, as well as human influences, which have affected historic land use, settlement, and farming practices.

The quality of agricultural land varies across Somerset, though the majority is Grade 3 (Agricultural Land Classification (ALC)). Areas of Grade 1 and Grade 2 ALC are scattered throughout, though predominantly focused across areas of Yeovil Sands in the south, Taunton Vale in the west, and parts of the moors in the centre. These areas are considered ‘excellent’ or ‘very good quality’ agricultural land given the presence of lighter or fertile silty soils and gentle landform, and generally give rise to areas of arable land use. Pastoral land use dominates where areas of heavier clay soils, seasonal inundation and steep slopes influence the landscape.

Valued semi-natural habitats are located between areas of agricultural land use. These include woodlands, heathland, wetlands and grassland habitats. International and national designations within Somerset (outside of Exmoor National Park) include 211 Sites of Special Scientific Interest (SSSIs), 47 Special Areas of Conservation (SACs), one National Nature Reserve (Somerset Wetlands NNR), one Ramsar site (Somerset Levels and Moors) and one Special Protection Area (SPA) (Somerset Levels and Moors).

Extensive areas of deciduous woodland are predominantly concentrated along steep slopes, including the escarpments on the fringes of the Mendip Hills (in the north), Blackdown Hills (in the south-west) and Greensand hills (in the east, extending into Wiltshire). The Mendip Hills hosts a particularly notable density of ash woodland, though ash dieback poses an imminent threat to the extent and composition of these woodlands. Other extensive areas of woodland are located within the Quantock Hills (including sessile oak woodland) and at Copley and Butleigh Woods (including oak and ash woodland) in the south-east of the Polden Hills. Woodland habitats within the Quantock Hills contrast with areas of unenclosed semi-natural heathland, which form an important habitat, given the limited areas of semi-natural heath remaining within the UK. Notable areas of carr woodland (wet woodland) complement the fen habitats at Shapwick Heath within the moors. Areas of wood pasture and parkland are associated with the designed landscapes of historic estates (many of which are within Registered Parks and Gardens (RPGs)). Areas of traditional orchards (priority habitat) have declined from what was once a wide-spread land use within Somerset. However, surviving remnants of traditional orchards remain and are typically associated with farmsteads and settlement edges. Elsewhere, the treescape within Somerset mainly comprises smaller pockets of deciduous and mixed woodland, sinuous riparian woodland and scattered hedgerow trees. Blocks of coniferous and mixed plantation are located throughout the landscape, notably on the fringes of the Blackdown Hills (in the south-west) and Greensand hills (in the east, extending into Wiltshire) and within the Quantock Hills.

Important wetland habitats extend across the centre and west of Somerset, and form part of the wider Severn Estuary. Unique tidal and estuarine habitats within areas of salt marsh and mudflats in the west of Somerset support notable populations of birds, recognised in their designation as part of the Severn Estuary Ramsar Site, SPA, SAC and Important Bird Area (IBA) and Bridgwater Bay SSSI. Water-filled pits or ponds associated with areas of former peat extraction are managed as nature reserves with regenerated wet woodlands, reed beds and aquatic habitats, notably near Shapwick Heath, Meare Heath and Walton Heath. Areas of salt marsh, mudflats, coastal and floodplain grazing marsh, raised bog, lowland fens and lowland meadows (all priority habitats) form part of the Somerset Wetlands National Nature Reserve (NNR), England’s second ‘super’ NNR which absorbed six separate reserves spread across the landscapes of the coastline, levels and moors.

Underlying geological variations within Somerset have resulted in exploitation of mineral resources, particularly within and near the fringes of the Mendip Hills in the north. Many of the former quarrying sites within or to the east of the Mendip Hills offer notable geological exposures and are designated as geological SSSIs. Other sites of geological interest include fossil-rich exposures across the coastline between Blue Anchor to Lilstock and the limestone outcrop formed by Brean Down in the north (both geological SSSIs).