3. Highway Landscaping Assessment

Transcription

1 Guidelines for Highway Landscaping Highway Landscaping Assessment 3.1 Introduction This section outlines the steps necessary to assess the highway landscaping component of a state highway construction project. Highway landscaping assessment informs concept plans that are considered prior to obtaining designations and resource consents for a construction project. The planning stage of a project is critical in achieving successful highway landscaping that meets Transit s expectations and integrates with the surrounding environment. Collect background information Preliminary site assessment and site visit Scope level of assessment required Section 3: Highway Landscape Assessment Information to assist identification and evaluation of options: Transit s Expectations for Highway Landscaping (Section 2) Statutory considerations especially RMA district and regional plans Landscape and visual assessment (in the case of RMA approvals this will form an integral part of the AEE) Identify and evaluate mitigation options Site visit Consultation with key stakeholders may be required Information to inform solutions: Transit s Expectations for Highway Landscaping (Section 2) Highway Landscaping Maintenance (Section 5) Landscape vision Develop master plan and/or developed design Section 4: Highway Landscape Design Community consultation RMA approval conditions Detailed design Contract documents Establish vegetation Landscape resource inventory Section 5: Highway Landscape Planting management plan Maintenance Planting maintenance schedule Feedback and review Implementation of planting maintenance Performance monitoring

2 Guidelines for Highway Landscaping Assessment checklist Assessment checklist This checklist outlines the range of tasks required to complete a landscape and visual assessment for highway landscaping. At the end of the process, a statement of effects will help identify the appropriate landscape options to mitigate the adverse effects of the highway project on visual quality and the surrounding landscape. Preliminary steps 1 Collect background information 2 Complete desktop assessment 3 Complete field assessment Landscape assessment 1 Identify landscape and visual character 2 Identify landscape units of distinctive character 3 Identify landscape qualities 4 Determine landscape sensitivity Visual assessment 1 Identify/describe visual catchment 2 Identify viewing audience: use on-site observations 3 Establish viewpoints: take photographs 4 Identify the sensitivity of viewing audience 5 Identify safety and visual interest aspects Summary and evaluation of impacts 1 Assess the likely effects of the highway on landscape character including ability for the highway to integrate with the surrounding landscape context 2 Assess the visual effects of the highway on the viewing audience 3 Prepare a statement of highway development effects Mitigation 1 Identify areas where mitigation is required 2 Develop appropriate mitigation options that avoid, remedy or mitigate the potential adverse effects of the highway project 3 Incorporate mitigation options in the landscape design

3 Guidelines for Highway Landscaping Assessment objectives The need for assessment Successful landscape design relies on a thorough understanding of the existing landscape character and the likely effects of the highway development on the landscape, the surrounding environment and those who experience it. By carrying out both a landscape and a visual assessment of the area affected by the highway corridor, suitable mitigation options can be designed to fulfil Transit s expectations of highway landscaping and successfully integrate the highway project with the surrounding environment. Objectives of assessment The objectives of landscape assessments are to: identify the significant features, character and value of the existing landscape, and in urban areas the built environment, through which the highway will pass identify and evaluate the nature, extent and significance of any landscape, environmental and visual effects caused by the highway development identify the concerns of interest groups and stakeholders identify how landscaping contributes to the local sense of place and community. 3.4 Scoping the assessment Scoping the assessment For all highway landscape works, some level of assessment will be required. The amount of detail required is dependent on the size and complexity of the highway design and the landscape into which it is being placed. The Level of Assessment Matrix below can be used to help determine the level of assessment required.

4 Guidelines for Highway Landscaping 3-4 Level of assessment matrix Key Comprehensive landscape and visual assessments and reports (expert input may be required) Landscape and visual assessment statement required Preliminary assessment required to validate design options Urban Cities and towns Large viewing audience Environmental setting High natural and scenic values Higher biodiversity Coastal, wetlands, native bush and forest Wilderness areas Rural/modified and semi-natural Lower biodiversity Agricultural and productive land Limited natural values Minor projects Landscape upgrades Minor realignments Intersections Roundabouts Medium projects Interchanges Realignments Large bridges Bypasses Major projects Urban expressways Multi-lane highways Type of highway development Specific assessment for urban and natural environments Assessment of urban and natural areas requires special consideration as these areas tend to be more complex due to the features and character of the built environment or the makeup of the surrounding natural landscape. Particular considerations for assessment in urban areas include: the influence of built form on the local landscape character and local sense of place. The assessment should detail the context, character and connections between built form (including buildings, structures and urban infrastructure, such as utility poles) the patterns of activity and perceptions of pedestrians, cyclists and adjacent land users the role of vegetated areas for screening, green space and visual relief in the hard urban landscape the need to identify existing urban design and open space strategies and main street schemes to ensure highway landscaping is integrated with local initiatives. Natural areas are valued for being unmodified and pristine. To ensure highway landscaping in these areas support existing values, assessment should include: the makeup and complexity of the surrounding vegetation the integrity and sensitivity of existing vegetation the significance of ecological values that apply to surrounding vegetation on a local, regional or national scale the scenic qualities of the surroundings.

5 3.5 Preliminary assessment Guidelines for Highway Landscaping 3-5 Information required A preliminary assessment involves collecting background information and baseline data on the elements, character and quality of the highway corridor s surrounding environment. This information will be of three main types: land form (the physical qualities of the land and local climate) land cover (vegetation, habitats, biodiversity, ecological values and built form in urban environments) land use (land use and settlement patterns and cultural and heritage issues). It is important to understand the landscape character of the proposed route Collecting background information A range of background information and data may assist in the preliminary assessment: previous landscaping or other studies, including regional highway strategy studies and assessments of environmental effects highway design details maps containing information about roads, land-use patterns (existing and historical), cadastral information, geology and soils, landmarks, and topography aerial photography council plan and policy documents, studies such as urban design and landscape strategies/plans, and design guides any relevant legislation, case law and policy This may be sourced from: local knowledge central and local government agencies libraries and archives

6 Guidelines for Highway Landscaping 3-6 Information assessment Following the collection of background information, an initial desktop assessment should be used to identify the main characteristics of the area and the key elements of the highway development including: landscape features such as landform and land cover environmental values, such as pristine areas, unique or threatened species and important habitats cultural elements, either physical or spiritual heritage significance patterns of activity and pedestrian movements in urban areas Field assessment A field assessment clarifies, verifies and supplements the desktop assessment through site observations, measurements and photography. Depending on the nature and complexity of the project, the field assessment may require a number of site visits. Direct experience of the landscape site will provide supplementary information that goes beyond the purely visual. 3.6 Landscape assessment Introduction A landscape assessment determines: the distinctive nature and characteristics of the area surrounding the highway development the relative significance of sections of the surrounding landscape the sensitivity of landscape units to change the subsequent overall effects on landscape character and quality. The specific conclusions from the landscape assessment will be used to: identify opportunities for maximising benefits assist in the assessment of visual effects determine appropriate landscape and environmental mitigation options. Landscape assessments generally involve the following steps: 1 identifying and assessing landscape character and the surrounding environment 2 classifying landscape units 3 determining landscape and environmental quality 4 determining landscape and visual sensitivity. Expert advice should be sought where significant landscape and ecological values are identified.

7 Guidelines for Highway Landscaping 3-7 Landscape character Landscape character should be determined through the information gathered in the desktop and field assessments. Character is derived from the physical, environmental and visual attributes of the landscape, such as landform, land cover (including biodiversity and ecosystem integrity), adjacent buildings and land use. These components of the landscape combine with aesthetic elements to create the character or sense of place of an area or location. Aesthetic elements such as scenic qualities, remoteness, degree of activity or tranquility should be noted if they are significant characteristics of the local landscape and surrounding environment. Landscape units Landscape classification involves identifying and categorising relatively distinct landscape types that is, areas that display a unified and consistent landscape and environmental character. Landscape types can then be broken down into smaller landscape units, which will be more homogeneous in terms of physical and visual character. The edges of individual units are identified wherever significant changes in landscape character occur. Often these will be marked by natural boundaries such as catchments, prominent landforms (eg ridgelines) or water bodies. Depending on the size of the project and complexity of the landscape, these units can be broken down into sub-units, which display more subtle variations. As part of this process, it is important to consider how the various landscape units relate to each other and not just view them in isolation. Landscape and environmental qualities Determining the quality of the various landscape units (including their general environmental quality) should be part of the landscape assessment. Measures of landscape quality can also help determine landscape sensitivity. Each landscape unit may be ranked to easily compare the relative values of each unit. Quality is site-specific, however, and a landscape unit that is not considered to be of significant value in an area of higher natural character may be important in a more modified area. For example a small grove of remnant native trees may not be significant within the context of a National Park but take on considerable value within an extensively modified urban environment. Attributes that can assist in determining landscape quality are listed below.

8 Guidelines for Highway Landscaping 3-8 Landscape quality attributes Ecological integrity strong connectivity and linkages free of plant and animal pests Rarity Rarity involves assessing how rare or important the landscape unit is within the local or regional context. Rarity may result from either natural elements (including biodiversity and ecological values) or from cultural modifications to the landscape. Aesthetic values Attributes to consider in determining the aesthetic value of a landscape include: degree of modification of the surrounding environment activity iconic parts of the landscape diversity or uniformity remoteness or close connections to adjacent areas physical features such as land form, vegetation and water bodies (including their specific attributes variety, patterns, colours, composition, scale) visual attractiveness (scenic quality) including the nearby scenery. Heritage and community values Landscape heritage values may result from a combination of natural characteristics (landform, water bodies or vegetation) or cultural influences (land use and modification) or elements (a pa site or distinctive building). Heritage values provide strong continuing links to the past and help create a sense of identity. The value of a heritage element is dependent on a number of elements including how unique, representative or intact it is. Consultation with stakeholders including community groups, iwi and adjacent landowners should aim to identify the values and associations the local community has with the surrounding landscape. Landscape and visual sensitivity Landscape sensitivity is a product of the combined values of: landscape quality (described in the preceding section); and visual absorption capability (VAC). VAC is the capacity for the landscape and environment to accommodate change, while retaining its inherent character and quality. Generally, landscapes and environments that are more complex have a higher degree of visual absorption. Some factors to consider when determining VAC are listed below.

9 Guidelines for Highway Landscaping 3-9 Factors to consider in determining VAC Vegetation abundance and diversity The higher the cover and biodiversity the higher the VAC. Visual diversity The greater the visual diversity, determined by the presence of contrasting elements, and the complexity of both natural and cultural elements, the higher the VAC. Slope and topography Areas of varied terrain or undulating landscapes usually have a high VAC, as the landform allows for screening and visual integration. In contrast, both flat and steep landscapes usually have a low VAC as they provide fewer opportunities for accommodating change. Exposure and visibility The less screening provided by natural features (trees/topography) or development (buildings) the higher the VAC. Soil stability/erosion potential The more erosion potential, the lower the VAC. The most sensitive landscapes are usually those with a low VAC and a high degree of quality. 3.7 Visual assessment Introduction The process of carrying out a visual assessment is primarily site based. The function of the visual assessment is to determine: the nature and significance of the visual effects on local residents and businesses, who are most likely to be affected by any negative effects of the highway development visual and safety issues for the highway user sensitivities of the surrounding built environment. The results of the visual assessment will be used to determine appropriate landscape mitigation options. Visual assessments involve the following steps: 1 description of the visual character of the defined landscape units 2 identification and description of the visual catchment and views from the highway 3 identification and description of the viewing audience 4 establishment of viewpoints 5 consideration of visual sensitivity and safety issues. Visual character This involves identifying and describing the visual setting and character of the individual landscape units. Key features will have been largely determined by step one (landscape character) of the landscape assessment.

10 Guidelines for Highway Landscaping 3-10 Visual catchment The visual catchment is the main area from which any part of the highway development can be viewed. All significant visual effects of the highway will occur within this area. Viewing audience Once the visual catchment is determined, the viewing audience needs to be defined. Views-in audience: This involves identifying the location, composition and relative numbers of those people with views of the highway. This may include a permanent audience (local residents) as well as temporary audiences (people visiting the area or passing through). Views-out audience: The highway user has quite different needs and expectations to those in the surrounding visual catchment. It is usually not essential to define the composition of this audience. But it may help in setting priorities for landscape works in scenic and tourist routes, where there is likely to be large numbers of tourists with high expectations of a satisfactory scenic experience. In urban areas, the visual assessment should consider pedestrian and cyclist experiences of the surrounding landscape if appropriate. Viewpoints Viewpoints should be selected from within the visual catchment and at various points along the length of the highway corridor. Representative views should be obtained to: assist in the evaluation of the visual effects of the highway development from a representative range of locations within the visual catchment assist in the evaluation of the likely visual experience of the highway user. Often views in can be adequately realised from public land and roadways adjacent to the highway. If the highway alignment actually (or potentially) has significant visual effects from particular sites or properties, it may be necessary to enter private land to ascertain the full impact. Views out can be obtained by walking the existing or proposed highway corridor. This also helps ascertain the extent of the visual catchment area for both the views-in and views-out audience. From these locations, appropriate photo-viewpoints should be selected. These should fairly represent the range of public and private views towards the highway development from within the visual catchment area, as well as the visual experience from the highway. They can be used to assist in the overall assessment of visual effects. Serial vision, that is the sequence of views experienced by a moving observer, may be examined. The sequence of views experienced by both fast-moving observers (in vehicles) and slow moving observers (pedestrians and cyclists) should be considered if relevant. Panoramic photographs are most useful and should be taken with a 50 mm lens that approximates what is seen with the human eye. On larger projects it may be useful to employ 3D computer simulations to assist in the assessment.

11 Guidelines for Highway Landscaping 3-11 Visual sensitivity and safety The key factors to be considered when determining the visual effects of the highway development are: the sensitivity of the landscape and views to change the effects on driver safety. Sensitivity of the viewing audience to change The sensitivity and likely changes to the character and quality of the landscape unit will have been identified during the evaluation of landscape and environmental effects. The nature and sensitivity of the viewing audience within the visual catchment should be determined by considering the following: Type of audience The permanent views-in audience is likely to have a relatively high sensitivity to changes in a landscape that they experience on a daily basis and are attached to at an emotional level. Temporary views-in audiences are likely to have a wider range of sensitivities, as they are in the area on a more occasional basis. Distance from the highway The distance to the highway from the viewing audience will be a significant factor in determining the visual impact of the highway. From nearby, a highway will generally be a prominent feature. But when viewed from a distance of several kilometres, it will often be assimilated into the wider landscape setting. Relative viewing angle A highway is likely to be far more apparent when viewed from above. This is because more of the roadway, and its relationship to the surrounding landscape, will be revealed. Focus of the view In locations where the main views are directed toward the highway, the visual impact will be more significant. Clarity of view Clarity of view depends on the presence or otherwise of visual impediments (landforms, vegetation or structures) between the viewing audience and the highway. Safety and visual interest Sight lines, visual interest and landscaping aid drivers to read the road and are relevant considerations at the visual assessment stage to ensure road safety is addressed in mitigation options (refer to Section Road safety requirements for further discussion).

12 Guidelines for Highway Landscaping Summary and evaluation of impact Statement of highway development effects The objective of this stage is to consider and describe the actual or potential effects of the highway development on relevant landscape and environmental elements, including land form, land cover and land use, and the visual catchment and viewers. The statement should describe the severity of overall disturbance and state any specific effects on landscape, environmental or visual values. Mitigation options The statement of highway development effects can be used to develop appropriate mitigation options as the basis for the landscape design process. These measures should be designed to avoid, remedy or mitigate the highway development s potential effects and help integrate it with the surrounding landscape. As well as having an aesthetic function, landscape mitigation must maximise the opportunities for achieving Error! Reference source not found.: maintain and improve safety promote biodiversity improve visual quality manage stormwater runoff manage pests improve local air quality improve business practices. Consultation with the community and stakeholders in accordance with Transit s guidelines for consultation should be undertaken on significant mitigation options that are identified. This consultation will need to be aligned with the highway project plan and consultation on wider project issues. 3.9 Examples of mitigation options

13 Guidelines for Highway Landscaping 3-13 Safety Effects/issues identified Non-frangible vegetation in clear zone Planting causes pedestrians to perceive risk of concealment in urban areas Potential mitigation Installation of safety barrier, or removal and replacement with frangible species Shrubs and grasses allow clear views between pedestrians and traffic Biodiversity Visual quality Stormwater Fragmentation of indigenous vegetation Modification of existing wetland habitat Modification of landscape character Degrades landscape quality Impact on aesthetic appreciation of local community Reveals surrounding landscape to highway users Modification to existing ridgeline Treatment of road run-off Streambank erosion Re-establish ecological link with native planting Ensure continued water supply through appropriate earthworks to direct run-off to wetland area Establish planting to blend in with local character Integrate and conceal portions of the highway through screen planting and earth mounding Treat areas of main impact with earthworks and planting to meet community values Plant vegetation in front of buffers, walls or berms to enhance visual amenity for adjacent residents and highway users Frame views Conceal break in ridge with planting Vegetated swales are designed to filter road run-off Establish riparian planting Pests Native plant pests in soil Ongoing weed management Animal pest management Adequate site preparation Replenish mass planted areas to maintain dense ground coverage Replacement of blackberry with locally appropriate species and scheduled grass cutting Business practice Maintenance implications of landscape schemes Maintenance personnel consider the access, weed management, and replacement planting requirements of design before finalisation. Planting selection, spacing and establishment reduce maintenance visits and traffic management costs

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