©Crown Copyright. All rights reserved. Hertfordshire County Council, LA 076678, 2001
| Landscape Character Assessment | HertsDirect | Environment | |||
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©Crown
Copyright. All rights reserved. Hertfordshire County Council, LA 076678, 2001
Mimmshall valley runs in a north/south direction around Welham Green. The area is confined in the east and west by major transport corridors (the A1(M) and the railway line) and higher ground. The settlements of Hatfield and Potters Bar form the north and south boundaries respectively.
©Crown
Copyright. All rights reserved. Hertfordshire County Council, LA 076678, 2001
Mimmshall Brook valley slopes and floor have a wooded farmland character, with rectangular field compartments along the valley slopes. It is strongly influenced by the major transport routes and the surrounding settlement, which give it an urban-edge rather than a rural character. The Royal Veterinary College is located centrally and has a local impact. The roads down the slopes coincide with a series of high points and the meandering streams that feed the brook also mark the shallow valleys between.
Swallowholes in Brush Wood (E. Staveley)
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Geology and soils. The area lies within the central river valleys, part of the northern Thames basin. The slowly permeable clayey soils mostly have brown subsoils and lie over Tertiary clays, giving rise to seasonal waterlogging (Windsor series). There are local areas of slight seasonal water logging on the slopes. Springs issue from a distinctive spew gravel bank at Potterells.
Topography. A string of high points runs centrally along the area and the land falls slightly away to the east at the boundary of the Hatfield estate.
Degree of slope. The average gradient is 1:30.
Altitude range. 80m to 110m.
Hydrology. Water End swallowholes (SSSI) are major sinkholes in chalk and a permanent landscape feature. The site, which is the largest in England, consists of a group of more than 15 sinkholes where two streams drain from the London clay and sink very close to the boundary of a chalk outcrop. During heavy rainfall a lake accumulates in the basin but is only temporary. This flow is the spring source for Chadwell at Ware (New River), and overflows westwards into the Colne (the Mimmshall Brook at Water End). Ponds at Welham Green are connected underground. A number of small ponds on the higher ground are associated with the farms and woodlands.
Land cover and land use. Wooded farmland is prominent throughout the area. The farmland is predominantly arable, with small fields of pasture with fenced boundaries edging the settlement and surrounding the Vet College. The area is well used for informal recreation.
Vegetation and wildlife. The willow carr/swamp community adjacent to the Water End swallowholes is of biological importance, with stands of wetland species. Field boundaries are generally treed hedgerows, with hedgebanks locally. Hawthorn is a common hedge species throughout the area, with elder and elm also frequent. Other species include ash, dogwood, field maple and blackthorn. Woodland blocks are relatively small and unconnected, generally an oak/ash mix with wetland species associated with watercourses. Hornbeam, field maple and the occasional beech can also be found. Bush Wood at Welham Green is a significant hornbeam woodland. Some remnant acid grassland can be found in association with the oak/hornbeam woodland. Immature woodland planting mixes edge the A1(M) corridor.
Historically, the woods were used for a supply of timber for brick kiln furnaces. A moat is sited to the west of Welham Green. The transport corridors and regular configuration of lanes that cross the area have strongly influenced the landscape character and evolution of the settlements and have obliterated the historic/cultural pattern. For example, any links with North Mymms Park have been severed by the motorway corridor. Relics of the historic field pattern can be found further up the slopes away from the A1(M).
Field pattern. Small regular.
Transport pattern. The A1(M) and the railway define this area to east and west.
Settlements and built form. Linear 20th-century settlement borders Hawkshead Lane and the historic village of Water End follows the Mimmshall brook. Some infill development has occurred adjacent to the A1(M) corridor. Isolated houses and farms are scattered throughout the area. Mimms Hall is located close to Potters Bar and has a flint and red-brick lodge house, which is unusual in the area.
English Nature SSSI notification.
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In general, dense hedgerows and woodland restrict visibility. Longer views are generally associated with the larger fields on the high ground. Vegetation and landform confine views within the Mimmshall Brook valley.
Rarity and distinctiveness. The geological SSSI in this area, Water End swallowholes, is the best example of its type in England
The site and sound of the A1(M), railway line and the surrounding settlements of Potters Bar and Hatfield cause a significant impact on the character of the entire area, while the Vet College has a localised impact. The pig farm only presents a very localised impact and is well screened by vegetation. At the southern end of the area views are marred by the leisure centre and Cranborne Industrial Estate, offset by the Furzefield Local Nature Reserve.
Access is good and the landscape is well used by the local residents. Parking access is difficult for most of the footpaths in the area. Motorcycling, walking and riding recreational activities also occur.
Elements in this landscape are regarded as distinctive (D). The Potterells slopes are perceived as being particularly significant: 'A pleasant walking area with many paths' (Potters Bar Society). The Furzefield Local Nature reserve is valued by local residents.
Mimmshall is recognised within the county Biodiversity Action Plan as a High Biodiversity area (HBA) for its woodlands.
Geological SSSI: Water End swallowholes
| CONDITION | |
|---|---|
| Land cover change: | localised |
| Age structure of tree cover: | mixed |
| Extent of semi-natural habitat survival: | fragmented |
| Management of semi-natural habitat: | poor |
| Survival of cultural pattern: | interrupted |
| Impact of built development: | high |
| Impact of land-use change: | moderate |
| ROBUSTNESS | |
| Impact of landform: | apparent |
| Impact of land cover: | prominent |
| Impact of historic pattern: | relic |
| Visibility from outside: | locally visible |
| Sense of enclosure: | partial/mixed |
| Visual unity: | incoherent |
| Distinctiveness/rarity: | frequent (with SSSIs) |
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