Protection of the existing landscapes and mature vegetation is of critical importance because of the long time scales required to establish landscapes that are able to support a variety of plants and animals and to allow planted vegetation to mature.
Mature vegetation and existing habitats, where possible should be retained. There are a number of solutions that can be implemented both pre and during the construction process to protect existing landscapes and habitats.
Buffer Zones are a well established method for protecting existing landscapes and habitats. They often contain mature planting therefore have the ability to separate conflicting land uses as well as provide attractive boundaries or ‘edges’. They can also be used to avoid disturbance of existing features during construction and operational lifetime as even temporary disturbance can cause permanent damage to existing landscapes.
Buffer zones can also reduce the potential for future conflicts with residents due to reduced security from houses about woodland, heavy shading from trees, potential for tree roots to cause subsidence and/or perceived danger from veteran trees. Where watercourses or other sensitive landscape features are located on site, a buffer zone will be required to protect it during construction and operation.
To be effective buffer zone widths should be a minimum of:
- Ten metres from rivers.
- Eight metres from smaller watercourses and ponds.
- 20 metres from woodland to the edge of residential gardens and other property boundaries.
Case Study: The Staithes, South Bank, Gateshead, Newcastle
Consultant: Hemingway Design and Glen Kemp
Development Type: Sustainable outside living space
The aim of the project was to redefine the streetscape and deliver sustainable external living space in which communal space and safe play space were given priority through innovative design.
The layout of the site respects the scale and character of the River Tyne corridor. In the central and western sections of the site, the development footprint was pulled back from the river so as to minimise the impact on a valuable roosting and feeding site for wading birds at the mouth of the River Team. Appropriate native screen planting is to be planted between the river and the development site in these sections. Adequate space was allocated to the continuation of a cycle route along the river edge.
At the western end of the site, a significant section of structure planting associated with the 1990 Garden Festival was retained, providing a buffer zone between the housing and the Borough’s sole area of saltmarsh habitat.
Exclusion zones are buffer zones which have additional restrictions on their use. Mitigation involving exclusion zones must be considered at the design stage, to ensure that the zone is feasible and viable in terms of practical working area and implemented and maintained in accordance with the approved plans.
Protective fencing is essential for ensuring contractors and others are aware of areas of landscape value which are vulnerable to damage on site. Breakdowns in communication are frequently responsible for irreversible errors on construction sites.
Where development will disturb a habitat, a habitat protection scheme must be in place. If protected species are present then a scheme of habitat fencing and supporting specification, including licenses will be required before work starts on site.
Habitat protection schemes may include fencing vegetation to preserve or reduce the adverse effects such as trampling. Fencing of buffer strips abutting watercourses is desirable in rural areas to reduce poaching from livestock.
Features such as trees that are proposed to be retained or removed must be clearly identifiable on site by spraying with brightly coloured paint. The project manager and contractor must also have the most up-to-date, approved plan of features being retained and those to be removed.
New landforms such as earth bunds can be an effective way of screening existing landscapes and habitats from adverse noise and visual effects. The M25 Widening Scheme case study below is an example of how this can be achieved.
Case Study: M25 Widening, Junctions 16 – 23
Consultant: Skanska Balfour Beatty
Development Type: Creation of new landforms to provide visual and acoustic screening for sensitive locations along the M25
Widening of the M25 in Hertfordshire between Junctions 16 and 23 began in Spring 2009, working predominantly within the existing highway boundary. The main contractor, Skanska Balfour Beatty (SBB) identified the need to dispose of large quantities of excavation spoil from the route that would, of necessity, need to be disposed of off-site unless they could find alternatives to conventional land fill adjacent to the motorway.
From the outset, SBB sought to identify sites where they could constructively dispose of excavation spoil to create new landforms that would provide visual and acoustic screening for sensitive locations along the route without detriment to the landscape. The aim in all cases, was to return the land to productive use and to a land quality at least the equivalent or better than its former condition whilst also reducing or eliminating the need to transport soil via lorries using the local highway network.
The first of the schemes was successfully completed in summer 2010 at Maple Cross where around 0.5m tonnes of soil was deposited on agricultural land adjoining the motorway to provide a new noise and visual screen for residential properties located close to the motorway. The entire operation from the initial stripping of the soils to the final restoration of the land back to agriculture took just 12 months.
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Timing and phasing
Timing and phasing are important ways of minimising adverse effects of development on wildlife and existing habitats. Works must be phased and carried out with regard to seasonal patterns such as nesting, mating and hibernation. It is important that advanced planning of development schemes is carried out in order to maximise the effectiveness of development schemes.
Monitoring of a development, particularly during the construction phase, is critically important. This will ensure that a development is not having unanticipated adverse effects including; dust, noise, unauthorised vegetation clearance, inappropriate materials storage, night lighting and polluted runoff, on the biodiversity values on a site and the surrounding area. Active and regular monitoring in a timely manner helps ensure that mitigation measures can be provided where necessary e.g. constructing bunds to catch runoff before it enters a watercourse.