Catchment Description Forum Through a Narrow Valley That Breaks Through High Chalkland on Either Side
Total Page：16
File Type：pdf, Size：1020Kb
South of Sturminster Newton, the Stour flows towards Blandford Catchment Description Forum through a narrow valley that breaks through high chalkland on either side. The northern entrance to the valley is Geology & Landscape guarded on its eastern flank by the twin hills of Hod and The Stour catchment extends across several very different types Hambledon. Here there is evidence of ancient settlements of geology. This greatly influences the landscape, giving rise to extending back through Roman to Neolithic times. The hills also landscapes of different character and with different types of support some of the most species rich chalk grassland in the countryside habitat. catchment, a habitat that once extended unbroken across the chalk landscape. Other fragments survive on the steep scarp The catchment watershed in the north is formed by chalk and slopes above the Blackmore Vale. greensand, each with groundwater that feeds the uppermost tributaries of the river system. Immediately south the catchment Rainfall across this chalkland percolates down into an extensive crosses a broad area of softer geology, predominantly of clays. groundwater, providing clear, cool water for chalk streams that The landscape is gently undulating and known locally as the flow south along the dip of the chalk toward the lower part of Blackmore Vale. It is drained by the Stour and a dense pattern of the catchment. They are few in number (including the Iwerne, tributaries that fan out across the vale. This is an agricultural Gussage, Tarrant, North Winterbourne, Allen and Crane) but are landscape of pastures, scattered villages and hedgerows forming an intrinsic element of the chalk landscape and the focus of an irregular patchwork. The larger settlements mostly border the villages scattered along the valley bottoms. vale, at Wincanton and Mere in the north and Sturminster Newton in the south, while Shaftesbury overlooks the vale At Wimborne Minster, joined by the River Allen, the Stour flows perched on high ground formed by greensand on the eastern over the chalk boundary and into the western side of a geological watershed. Gillingham lies on the junction of the Stour with two area known as the Hampshire Basin. Here the geology is of more of its major headwater tributaries and has expanded rapidly in recent Tertiary age and comprises mainly sands and gravels, and recent decades from an old centre to become a significant urban also clays and pebbles. The soils are typically clayey and sandy, area within the vale. and the landscape is characterised by once extensive tracts of heathland but with woodland on London Clay around the 1700704 v3 northern fringe. The tributary rivers are very different in Population character to those on the chalk. They are slower flowing, acidic The catchment has a population of 400,000. Around 75% live in waters, often rising at groundwater fed mires and bogs within the Bournemouth, Poole and Christchurch urban areas. The rest heathland. Many of these streams have been lost into of the catchment is mainly rural. Other towns within the underground sewers or greatly confined into green corridors by catchment include: Gillingham (12,000 population), Wincanton, the urban expansion of Bournemouth and its surrounds. Shaftesbury (7,000 population), Sturminster Newton, Blandford (9,000 population), and Wimborne. Several other settlements The Stour flows past this urban area, meandering widely within a have been developed in the south of the catchment around the broad floodplain, across a landscape of typically large pasture urban expansion of Bournemouth, such as Corfe Mullen, and arable fields. During wet weather the open land can flood Ferndown and Verwood. extensively, storing water unable to escape along the river at Christchurch and into Christchurch Harbour. Land Use The land use in the Dorset Stour catchment varies considerably Christchurch Harbour with the different geologies and drainage provided by the pattern of ditches, streams and rivers. There is evidence of agriculture and settlement going back to pre-historic times, especially on the chalk downland, at Christchurch Harbour and at the older historic towns such as Gillingham, Sturminster Newton, Wimborne and Christchurch. Across the catchment there are estimated to be over 300 Scheduled Ancient Monuments. Most of the catchment is agricultural. Farming ranges from small mixed farms through to intensive dairy units (both large and small) and onto considerable sized arable enterprises. Settlements and roads tend to be concentrated along the valleys or lower slopes of the chalk escarpments. Urban development only becomes dominant in the south of the catchment, especially along the seaward edge through the inland expansion of Bournemouth. There is little industry or history of industrial development, but commercial areas are associated with the towns and are more extensive around Bournemouth, particularly in the Moors River catchment which also contains Bournemouth Christchurch Harbour is a low lying basin that was flooded by sea airport. level rise after the last ice age. It now forms an almost enclosed estuary at the junction of the Stour and the neighbouring River The northern reaches of the catchment are rural; it is an Avon. The harbour is sheltered from the open sea by the agricultural landscape of mostly enclosed pastures and villages. headland of Hengistbury Head to the south and then by On the chalkland either side of Blandford the gentle slopes are Mudeford Spit which extends across the harbour mouth on its mainly used for growing cereals, often across large fields giving east side. At high tide the Harbour has an area of approximately wide open expanses to a distant horizon. The steeper valley 160 ha. As the tide recedes most of the water empties into slopes and the chalkland scarp to the Blackmore Vale are more Christchurch Bay and the English Channel through a narrow characteristically grassland used for sheep and cattle grazing. channel known locally as The Run which rests between Mudeford Quay and Mudeford Spit. Shallow draught boats can The valley bottoms and floodplains are also predominantly enter through the Run and cruise upstream for 2 miles into the grassland, for cattle and also dairy farming. The better drained River Stour or part of the River Avon. The land around the land is used for arable. Parts of the catchment are important for harbour supports many of the wildlife habitats that can be found forestry, mainly near Blandford and more especially on former where lowland rivers like the Stour meet the sea. These include heathland where extensive areas were converted to conifer th mudflats, saltmarsh, reedbed, wet meadows and sand dunes. plantation in the 20 century, such as at Ringwood and Hurn The area is also locally distinctive for the presence of Dorset Forests. heathland and ancient archaeological sites on Hengistbury Head. 1700704 v3 .