ENVIRONMENT
It is key for our studio to begin to explain some of the key environmental factors that are associated with Weston Island. Undertaking an environmental analysis of the site to determine how the elements affect the site, a survey of the trees and other vegetation that can be found in and around the area as well as a brief undertaking of the ecology that can be found along the river edge. With this information provided within this section, it informs us of important ecological factors that will have to be taken into consideration when proposing scheme that are going to directly affect the ecology of the place.
Environmental Analysis
Site Vegetation
This tree survey was undertaken in the 1990’s, in order for the planning application for the current bus depot to go through. Please note that some of the information recorded within this survey may be out-dated and some of the existing trees have been felled due to their condition in the recent years being deemed as hazardous for the surrounding ecology.
Flooding & Water Level Analysis:
The areas surrounding the Weston island are associated within flood zone 3, this
includes the pathways alongside the river as well as a part of Brassmill Lane.
The island itself is raised above the potential flood zone area, and due to the
defence mitigation alongside the embankment has allowed the hard surfaces to
be free from a potential flood. Furthermore, the Twerton Gates also inform a level
of defence through controlling the levels of the water all year round, these operate
on a automated computer system, that also work as a monitoring station, that is
used by the environmental agency to monitor water levels across the UK.
The section illustrates a site section, showing the differing land and water
heights relative to the average sea level. It also identifies the incident that occured on the 3rd and 4th October 2019, where both the river and the canal dropped by over 900mm over the course of the two days. This released imagery of the near bottom of the canal, and provided a slight indication of the depth of the Weston Cut Canal.
This graph was taken from the river levels website, and it informs a quantitative
data analysis of the River Avon. The data comes from the Twerton Gates and is fed
to a data base that stores information on the river levels. This is used to detect
potential flooding with rising river levels.
The areas surrounding the Weston island are associated within flood zone 3, this
includes the pathways alongside the river as well as a part of Brassmill Lane.
The island itself is raised above the potential flood zone area, and due to the
defence mitigation alongside the embankment has allowed the hard surfaces to
be free from a potential flood. Furthermore, the Twerton Gates also inform a level
of defence through controlling the levels of the water all year round, these operate
on a automated computer system, that also work as a monitoring station, that is
used by the environmental agency to monitor water levels across the UK.
The section illustrates a site section, showing the differing land and water
heights relative to the average sea level. It also identifies the incident that occured on the 3rd and 4th October 2019, where both the river and the canal dropped by over 900mm over the course of the two days. This released imagery of the near bottom of the canal, and provided a slight indication of the depth of the Weston Cut Canal.
This graph was taken from the river levels website, and it informs a quantitative
data analysis of the River Avon. The data comes from the Twerton Gates and is fed
to a data base that stores information on the river levels. This is used to detect
potential flooding with rising river levels.
Types of Vegetation on Site
Potential and Existing Wildlife Corridors
Utilising existing green routes from the catchment area provides potential wildlife corridors for the likes of bats, kingfishers and other birds to be able to migrate to different roosting areas. Optimising these areas are essential for the mitigation and preservation of the existing ecology of Bath and the wider context.
Ecological Analysis
Weston Island is subject to a number of planning designations. With regard to ecology the river is designated as a ‘Site of Nature Conservation Interest’ (Policy NE3, and the edges of the island form an important associated habitat).
Development proposals that seek a frontage with or to increase access to the river’s edge may be challenging as there is a need t maintain and improve this habitat.
Given the importance of the habitat, a use that doesn’t require a relationship with the water, such as the current use or other employment use, would be more appropriate, and would better enable biodiversity enhancements to be achieved.
Given the sites location within the bat corridor, lighting will need to be sensitively designed within the island.
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1. OTTERS
On the east and western fringes of the site, otters have been found to take refuge in these densely wooded areas. Al be it they are not there year in year out, improving these fringes in order to facilitate the resurgence of otters is an opportunity that can be utilised.
2. BATS
The River Avon is identified as a bat corridor, especially in the areas where overhanging woodland is present. This occurs in many areas of the site, and Weston island has been outlined as a special area of interest in order to maintain and preserve these ecological corridors.
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3. KINGFISHER
A kingfisher is a rare and easily disturbed bird. Its population saw a massive reduction when it was hit with extreme cold during the winters, but this population increases back to normality within the warmer months of the year. The optimum habitat is within still or calm waters, where it can feed on the small fish within the banks of rivers.
OTTERS
The European Otter Lutra is a species that has suffered historic declines due to hunting and pollution but which has recovered in many areas and in recent years become adapted to urban river stretches in many cities and towns. Fully protected under the Wildlife and Countryside Act 1981 (as amended) and Conservation of Habitats and Species Regulations (2010). Protection extends to the places of shelter or protection.
Otters typically have 40 lying up sites that they use as refuges through the year and holt sites. Coghill (1980) summarised the types of resting site recorded in the upper reaches of the Severn catchment. From a total of over 250 sites:
• 42% were under the roots of trees (90% Ash or Sycamore)
• 20% of sites in open air in reed or osier beds, young forestry plantations, islands, rhododendron bushes, bracken, hedges, scrub,
• 13% stick heaps and rocks
• 11% enclosed drains
• 14% - varied: badger setts, rabbit burrows, ‘hollow islands’, and a car body
Most lying up sites are within 10 m of water but some can be 50m away. Thom (1997) identified holt locations from an extensive study
• 58% were under trees (with half of these under Ash or Sycamore).
• 33% were in rocky banks, stone filled gabions or caves, and
• 9% were piles of debris or holes in the bank.
Average holt density = one holt per km of stream, but distribution clumped, with around a third of 5km sections having no holts and some 5km sections having around 10 holts.
BATS
There are 17 species of bat known to breed in the UK. Of these at least 8 species have recently been recorded in the Bristol Avon corridor through Bath. These were:
• Serotine Eptesicus serotinus
• Daubenton’s Bat Myotis daubentonii
• Noctule Nycatlus noctula
• Common Pipistrelle Pipistrellus pipistrellus
• Soprano Pipistrelle Pipistrellus pygmaeus
• Brown Long-eared Bat Plecotus auritus
• Greater Horseshoe Bat Rhinolophus ferrumequinum
• Lesser Horseshoe bat Rhinolophus hipposideros
The general consensus is that populations all species of bats in the UK, with the possible exception of Daubenton’s, are in decline (Mitchell-Jones 2004). All species of bat receive full protection under the Wildlife and Countryside Act 1981 (as amended). In view of their status across Europe, all species of bat have been listed on Annex IV of the EC ‘Habitats and Species Directive’, transposed into UK law by the Conservation of Habitats and Species Regulations (2010). Taken together UK legislation ensures that individual bats, their breeding sites and resting places are protected. Annex IV of the Habitats Directive relates to the designation of Special Areas of Conservation (SACs) and covers Greater and Lesser Horseshoe bats, One such SAC is the Bath and Bradford-on-Avon SAC; there are several roosts of this species within commuting distance of the Bath river corridor.
KINGFISHER
As a fairly rare, easily disturbed bird, the Kingfisher Alcedo atthis is afforded the highest degree of legal protection under the Schedule 1 of the Wildlife and Countryside Act 1981. It is an offence to take, injure or kill a Kingfisher or to take, damage or destroy its nest, eggs or young. It is also an offence to intentionally or recklessly disturb the birds close to their nest during the breeding season. Kingfishers breed beside still or gently flowing freshwater. Where there are no available nesting banks, they sometimes take to nesting on ledges or gaps in walls. Although shy and wary it can adapt to human settlements or to rivers much used for recreation when other conditions are sufficiently favourable.
Pairs are solitary and territorial and, although feeding may take place up to 1km from the breeding territory, each pair usually occupies a length of watercourse or shoreline of 0.8-1.5km. (Andrews and Kinsman, 1991). Breeding territories are vigorously defended.
The nest site is a tunnel in a steep or vertical bank, normally over water, and mostly 90 – 180cm above the water. Nests are reused in successive years. If there are not
any suitable banks available they may nest among the roots of fallen trees or in a sandpit (Holmes, 1985). Artificial banks for nesting have been successfully deployed (Hopkins, 2001).
During the breeding season Kingfishers feed mainly on small fish such as minnow, stickleback and fry, supplemented by a variety of aquatic insects, including caddis flies and the nymphs of dragonflies. Kingfishers will eat tadpoles, small molluscs
and crustaceans such as crayfish (Holmes, 1985).
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As much as possible of the wooded fringe around the island should be retained.
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An Otter holt, surrounded on the landward side by a thorn buffer, could be installed on the eastern end of the island.
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A Kingfisher bank could be installed on the southern bank of the island.
POTENTIAL INTERVENTIONS ALONG THE RIVER EDGE