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Introduction 7.1
The Transforming Trowbridge UDF identifies a number of key 7.1.1
aims regarding appropriate design for the River Biss corridor. This will ensure that the character of the river and central Trowbridge is not jeopardised and that existing assets in the area are protected.
The principles and design codes illustrated in this section of the 7.1.2
report are strategic in nature and are intended to provide overall public realm design guidance to a range of developments along the river corridor.
Creating and Protecting a Sense of Place 7.2
Designers and developers should seek to complement and 7.2.1
enhance an existing ‘sense of place’ by fully understanding what they are contributing to the character of an area. Sensitive urban design is required to reinforce local identity and to ensure that new development respects the river locations. By its very nature, a sense of place needs to be local, rather than one that has been ‘imported’ from somewhere else through the use of ‘pattern book’ designs or pastiche.
Urban character is strongly influenced by the land use and activity 7.2.2
present in an area. This document cannot allocate land use, but does support land uses which encourage activity along the river corridor.
Public Open Space Network 7.3
It is important that public spaces are fully integrated into the town 7.3.1
and respect the character and identity of their context. Access to public open spaces is critical in order to ensure they are vibrant and well used places. Public spaces should, therefore, relate closely to the proposed movement and linkages in Trowbridge town centre.
Strategic Design Guidance
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Movement and Linkages 7.4
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7.4.1 ew development adjacent to the river corridor should be well integrated into the wider street structure and high pedestrian and cycle permeability within the overall street layout should be a key goal. A connected street structure offering pedestrians routes to ‘where they need to go’ (eg. local facilities, the bus stop or the local park) is the best way of promoting walking and cycling. Development blocks that offer the pedestrian and cyclist a greater choice of permeable and legible routes should be promoted.
A network of interconnected streets and spaces should allow safe, 7.4.2
direct routes for pedestrians, cyclists, vehicles and the mobility impaired. This will maximise opportunities for interaction and minimise personal risk and isolation. Developments should look beyond individual site boundaries and ensure that linkages are made both to adjoining areas and within the development itself.
The public realm should be easily accessible for all, regardless 7.4.3
of age or physical ability. It is essential that existing pedestrian routes are protected and enhanced by development proposals. Development proposals should provide direct links which are attractive, well lit, have good levels of visibility and natural surveillance. Pedestrian links should be designed to a high standard and be clearly defined through high quality paving materials, pedestrian signage and street furniture. Seating should be provided at key nodal points and street trees should be planted to clearly define key routes.
Safe and direct access to public transport routes should also be 7.4.4
a key design principle. Providing easy walking access to public transport to/from new homes, employment areas, leisure and community facilities reduces the need to use the car and helps to ease congestion and pollution. Proximity to public transport also helps to make these facilities accessible to those who do not have a car. Bus stops should be located in popular, well lit and overlooked places and allow ease of access to key destinations.
Urban Form, Street Structure and Layout 7.5
The street structure relates to the pattern of streets and 7.5.1
development blocks within a given area. The urban form of Trowbridge has been analysed and compared with the layout and development of streets in the town.
The historic layout of Trowbridge consists of a number of clearly 7.5.2
defined perimeter blocks with buildings facing on to the street and the river. The historic town centre retail area has a relatively fine grain urban form and narrow plot widths provide a vertical emphasis to the street scene.
New development should respect the historic urban pattern and 7.5.3
where required, should seek to repair the perimeter block structure. This should ensure that all buildings have a positive interface with the public realm, and there is a clear definition between public and private space.
The street structure and layout should respond to the prevailing 7.5.4
urban form of the town, but should also respond to the need to provide the key series of movement links, public spaces and activities presented in the public realm strategy.
Layouts should be integrated into the wider urban fabric where 7.5.5
possible. The linkages should be based upon connected streets. Buildings should be orientated to create a recognisable street even if it is only used by pedestrians and cyclists.
The block pattern should consist of an interconnected network of 7.5.6
streets to create well defined, high quality, street environments. Continuity should be achieved by using perimeter block built form with buildings, arranged to provide street enclosure and definition.
Legibility refers to the degree to which people can understand and 7.5.7
identify with the built environment. Landmark buildings, marker buildings and a clear hierarchy of routes and intersections should increase the legibility of development. Building and layout design, planting and views should be employed to form visual focal points, achieve orientation and identity and create legible routes.
In
summary:-Public and private spaces should be clearly defined to create a sense •
of ownership. Development should front onto streets with backs facing onto private secure areas.
All routes should be well lit and overlooked. •
Car parks and service areas should be located and secured at the •
rear of development whilst blank walls interfacing with the public realm should be minimised.
Routes should be direct with consideration given to the creation of •
gateways and landmarks at key points. All new and existing routes should have a clear hierarchy and street typology and high quality and consistent signage should be provided.
UDF: Streets should encourage through movement
UDF: New river crossings should create landmarks to help orientate Trowbridge towards its river
UDF: Accentuate key landmarks and facades and emphasise key views to enhance the legibility of the town by night
UDF: All uses must be accommodated within an integrated pattern of streets UDF: A clear hierarchy of streets and squares should be developed.
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Building Heights and Relationships 7.6
Whilst the design and treatment of buildings is beyond the scope 7.6.1
of this public realm strategy, the interface between buildings and public space is of major importance. The physical bulk of the building, in terms of its footprint, length, width and height, has an impact on how public space is perceived and used. The physical massing of buildings also has an impact on the character of the area.
Trowbridge has a range of building forms including the fine urban 7.6.2
grain form of the historic core to the larger footprint former mill buildings, municipal buildings and food stores. In general terms the Town Centre consists of mainly 2 to 3 storey buildings with higher landmark buildings.
Designers will be expected to consider the relationship of the 7.6.3
building to the river and the public realm generally and in particular to the scale and massing of adjacent buildings. The set back of buildings to the river should also consider the proposed use of the adjacent public realm and the types of activities required.
One of the main objectives of redevelopment along the Biss 7.6.4
Corridor is to ensure that buildings enhance the setting of the river. Key frontages are critical to the appearance of any development. Particular attention should be paid to the massing and architectural style of the buildings adjacent to key open spaces, streets and squares to ensure that these prominent areas have a building frontage which helps to create distinctive quality and character.
Development should be ‘outward facing’ through the use of 7.6.5
active edges and perimeter blocks. This will take full advantage of natural surveillance. Buildings should be designed to enliven the street scene through the creation of street frontages and entrances. Ground floor door and windows fronting onto the street should be employed to provide activity.
Where possible, new development should provide active 7.6.6
frontages on to all major public realm areas so the building design should ensure sufficient interest and articulation to provide an interesting interface
High quality pedestrian links created by a positive relationship between built form
and public realm.
with the river corridor in these areas.
The landscape and urban design analysis highlights a number 7.6.7
of areas where space is poorly defined and where there is potential for strengthening street frontages. These areas tend to be the ‘backland’ areas where the distinction between public and private space is ambiguous. Development in these areas should build on the perimeter block approach and seek to create active frontages on to adjacent areas of public realm including roads, pedestrian routes and open spaces.
The orientation of buildings to overlook the river corridor and/or 7.6.8
street provides active frontages/eyes on the street which in turn provides natural surveillance and addresses issues of security and community safety.
Buildings should front the street to provide surveillance over 7.6.9
public realm areas and provide increased opportunities for social interaction by providing entrances on to the street. The aim is to create places and streets which are designed for everyone, reducing crime and improving personal safety.
The position of the front of the building in relation to the street is 7.6.10
commonly referred to as the building line. Trowbridge Town Centre has an urban character which in part is created by streets with a well defined building line, providing a strong degree of enclosure. The urban character is reinforced by nominal set backs from the back of footway and minimal gaps in the street frontage. In general terms the buildings proposed in new developments, have a minimal set back from the pavement, and so reinforce this very urban character.
In the more suburban parts of the study area (such as the Innox 7.6.11
Road residential area) the building line should be set back from the street. Where buildings are set back, a separate boundary is also provided often in the form of a low wall, railings or shrub planting. These features contribute to the character of a street or neighbourhood and should be respected.
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Building Line and Boundary Treatments 7.7
Ownership of space is one of the key determinants of well 7.7.1
managed safe and secure land. Where ownership of space is unclear, anti-social behaviour can take hold and create safety, security and maintenance problems. By establishing a clearly defined street and block structure a clear delineation is made between private and public space.
Building lines and boundary treatments have a significant role 7.7.2
to play in clearly defining public and private spaces. How boundaries are treated has a significant affect on the quality of the public realm. The scale and design of barriers can influence how people feel in a particular space. Blank elevations or high barriers can create a sense of insecurity.
To reinforce ownership within any new development the following 7.7.3
design principles should be considered:
Sensitive placement and appropriate selection of physical
barriers — gates, fences, walls and hedges — create safe places that are also attractive.
High fences and landscape that actively impede access
are most appropriate in places that are vulnerable to crime, such as the backs of dwellings.
Such barriers should be visually permeable so as not to
hinder natural or other forms of surveillance or provide places for offenders to hide.
Lower barriers, hedges and bushes are also highly useful to
signify the public/private divide.
UDF: Buildings of all types should front onto streets, squares or parks UDF: There should be eyes on the street
UDF: Development should have a clearly defined building line to create a disciplined and largely unbroken urban edge.
UDF: Where buildings are set back a significant distance from the street, they should have sufficient presence to contribute to that street
UDF: All streets, squares and parks should be clearly defined by appropriately scaled buildings and good quality trees.
UDF: Street elevations should be scaled to the proportions of the street
UDF: Use an approach that is of a sympathetic human scale appropriate to the county town.
UDF: There should be a clear definition between public and private space UDF: Development should have a clearly defined building line to create a disciplined and largely unbroken urban edge
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Street Design
7.8
Streets should be designed to be pedestrian friendly and 7.8.1
accessible for all users. In particular, public areas should be readily accessible for the mobility impaired and wheelchair users.
The proportions of street width to building height are an essential 7.8.2
component in defining local distinctiveness and these proportions should be taken into account within new development proposals.
Traffic calming is a key aspect of promoting pedestrian priority. 7.8.3
A holistic approach to traffic calming should be adopted, in which the environment is designed to reduce traffic speeds. Design elements such as tree planting, gateways and artwork can be introduced to deter speeding traffic.
The arrangement of buildings and road alignment, which 7.8.4
comprise the urban form, should be the primary means of ensuring that traffic speeds are appropriately low. The combination of road containment by buildings or planting, together with small radii corners are the most effective means of controlling traffic speeds. The careful location of these elements can slow traffic speeds by limiting forward views and reducing the physical and optical width of the carriageway.
This comprehensive approach to traffic calming creates a more 7.8.5
attractive environment and can reinforce local distinctiveness through the use of appropriate materials and planting. Recent streetscape
improvements schemes, such as Kensington High Street, have sought to minimise the use of guard railing.
UDF: Streets should be designed to encourage walking and cater for the needs of people with mobility problems.
Trowbridge Car Parking Strategy
UDF: On-street and rear courtyard parking is encouraged. UDF: The misuse of on-street parking must be avoided. UDF: The impact of the car should be minimised.
UDF: On-plot parking should be avoided in front of houses.
Parking 7.9
Whilst the quantity and distribution of car parking is beyond 7.9.1
the remit of the PRDG there are important design criteria related to the visual impact of on street and surface level car parking which should be considered. The wider context for car parking is contained in the Trowbridge Car Parking Strategy. The UDF also contains important references to the design of car parking in relation to built development. In particular the use of on-street car parking is promoted in order to bring activity to the street.
The need for disabled car parking spaces close to the town centre 7.9.2
and key community facilities is also required and should be provided. Servicing and Access Requirements
7.10
The need to accommodate servicing vehicles must be addressed 7.10.1
for all developments, but is of particular importance for commercial developments. The ideal mode of delivery should be from the street directly to the building. Where a delivery/storage yard is necessary, it is often placed within the rear of a development block, to ensure that it is hidden from public view, potentially secured with gates. Service or storage areas which have to be designed as semi-private space should be defined by contrasting paving which marks a transition from public to private space.
Access for refuse vehicles is a consideration for both commercial 7.10.2
and residential developments and appropriate manoeuvring space should be provided. In particular, there is a need for achieving convenient access to bins/recycling containers and minimising the distance they need to be moved to the refuse vehicles.
In terms of the public realm strategy the main aim is to avoid 7.10.3
potential conflict between servicing vehicles and pedestrians. In this respect, there is a need to keep vehicle servicing separate from pedestrian priority areas through appropriate design or management.
Development should also provide safe and effective access for 7.10.4
emergency and maintenance vehicles to all parts of the town.
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Public Space Design
7.11
The design of public open spaces should aim to achieve high 7.11.1
quality and multifunctional space which makes provision for a range of activities.
The layout should be fully integrated into the surrounding street 7.11.2
pattern and River Biss corridor and should be based upon the townscape analysis described previously.
The detailed design should respect the character of the area, 7.11.3
particularly in the use of materials, street furniture and planting.
Public space located nearer to the town centre should respect 7.11.4
the urban character that prevails. In these spaces the design will be based upon a hard landscape treatment.Towards the urban edge the design of public space should respect the parkland character.
Ecology 7.12
Ecological enhancement of the river and its corridor, should be 7.12.1
incorporated within new developments, creating a continuous ‘wildlife corridor’. Ecological enhancements have the advantage of increasing amenity and access opportunities and enhancing the aesthetics of the river. Known health benefits of creating such green space further justify improving the ecology of an area.
Opportunities should be taken to ‘open-up’ the river corridor, 7.12.2
by re-profiling the river channel and its banks, with appropriate marginal planting of native, locally characteristic species.
Creating a range of interconnected habitats within the corridor will 7.12.3
encourage a range of typical river species to use the enhanced habitat. Selective tree and scrub removal can create a mosaic of light and shaded areas along the river, adding to the diversity of habitats.
Planting 7.13
Planting provides seasonal interest and colour to the urban 7.13.1
environment. It is in contrast to the urban form and should be used to define public and private spaces. Tree planting is often an integral part of the quality of the streetscape. In Trowbridge Town Centre there is minimal planting which reinforces the urban character. There are opportunities for additional street tree planting to strengthen the landscape of car parks and existing green spaces.
In terms of street tree planting, ornamental species should be 7.13.2
used which are able to tolerate street conditions. Breedon gravel (or other bound gravel surface) should be used in preference to tree grilles which are often forced out of place by tree growth and can look unsightly if not properly maintained. Where the presence of underground utilities does not allow the use of tree pits, planters should be used. These should be properly integrated into the streetscape materials and constructed of York stone or other material appropriate to the particular character area. Where tree guards are used, these should relate to the style and colour of street furniture.
A palette of possible street trees includes: 7.13.3 London Plane • Ornamental pear • Sorbus • Whitebeam • Fastigiate Hornbean • Liquidambar styracifolia •
UDF: Use tree planting in the urban squares and streets to structure views and enhance the visual amenity of the built form.
UDF: Restore and enhance the character of the existing People’s Park by providing new specimen tree planting and additional planting.
UDF: Extend the formal avenue planting which currently exists in the Peoples Park into the surrounding streets of Parkside to give this district of the town a leafy character in keeping with the qualities of the existing park.
UDF: Deciduous species should be chosen for street tree planting which are robust and suitable for the soil type and location. They should be planted at an appropriate size to create initial impact in the development.
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River Channel 7.14
The definition of particular character areas offers the potential to 7.14.1
redesign the river channel to reflect the type of new development taking place. The more naturalistic character of Biss Meadows is to be extended into the Peoples’ Park by the proposed removal of channel retaining walls. This will provide opportunities for habitat enhancement and nature conservation.
An option for the existing concrete weirs along the river corridor is 7.14.2
to have ‘v’ notches cut into them. They could also be dressed with stone to create a more natural appearance and a more varied flow.
A low-flow channel, cut through the middle of the existing silty 7.14.3
river bed, would concentrate flows, providing faster flows in a central channel, with slower, shallow water over marginal ‘shelves’ adjacent to the existing banks. These marginal shelves could be planted with aquatic plants such as reeds, to provide much-needed habitat structure to the river.
In some locations, gabion baskets (stone-filled wire cages, used 7.14.4
for bank revetment) have silted-up over many years, resulting in a more natural appearance. Vegetation is already established on some of these areas and they should therefore be left in place if re-profiling of the river channel and banks is not feasible.
Where new gabion baskets are proposed, they should be 7.14.5
dressed with geo-textile or similar material and planted with suitable vegetation. This treatment will reduce their visual impact.
Where the river channel is highly engineered a range of options 7.14.6
should be considered:
Low intervention: retain existing channel, but install rock •
groynes to provide greater sinuosity and/or low-level berms to provide marginal vegetated shelves. Introduce gravel substrate to enhance channel habitat.
Medium intervention: cut a ‘v’ notch in existing concrete •
weirs, to reduce the impounding effect upstream. Dress the channel with stones upstream and downstream of the weirs to lengthen them, increasing the variety of flow and improving passage for fish. Install rock groynes to provide greater sinuosity and/or low-level berms to provide marginal vegetated shelves. Introduce gravel substrate to enhance channel habitat.
Major intervention: remove existing retaining features and •
re-profile whole river channel and banks to create a more natural profile and provide better access. Create two or three-stage channel profile to provide marginal ‘soft’ berms and higher-level berms for access. Carry out landscaping and appropriate planting on both banks. Remove weirs and restore channel bed, introducing gravel substrate to enhance channel habitat.
Sustainable Urban Drainage Systems (SUDS). 7.15
New development should consider SUDS as an element of 7.15.1
drainage infrastructure as well as for leisure and visual amenity. SUDS can be designed into most urban settings, ranging from hard-surfaced areas to soft landscaped features. They are used in conjunction with good management of the site, to prevent flooding and pollution. There are four general methods of control:
Filter strips and swales
Permeable surfaces and filter drains
Infiltration devices
Basins, ponds or centralised soakaways, reed beds.
