Duplication of the Southern Expressway – North–South Corridor
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Duplication of the Southern Expressway | Project Impact Report 17. Visual amenity 17.1 Overview The visual impact assessment of the project examined the existing landscape character, potential sensitivities of adjacent land use and degree of likely visual modification. It also reviewed the interrelationship of the existing landform, vegetation patterning, recreational activities, frequency of views, cultural values, environmental sensitivities, land use and key view corridors to determine the landscape character. The methodology applied considered the existing landscape character and the proposed new developments of visual modifications to that characteristic. There is no universal approach to visual assessment; however, the methodology outlined below is consistent with best practice and DTEI’s approach on previous infrastructure corridor projects. 17.2 Visual amenity methodology Linear infrastructure presents a unique development form as it typically traverses numerous landscape character areas and areas of sensitivity. A road corridor is typically assessed as a transient experience of visual effect both travelling along and from adjacent land use. The visual catchment of the project was assessed by numerous site visits identifying areas that have views towards or along the road corridor, areas of cultural sensitivity and an interrelation of the road alignment, associated earthworks and existing landform. Key views have been identified along the corridor, representing the driver and adjacent land. An assessment has been made of the potential effect of the duplication from these varying visual experiences. The visual amenity assessment was completed in a methodology in three stages (Figure 17.1). 17.2.1 Stage 1 – Desktop review The desktop review of land use patterning, mapping and information gathering on areas of significance identified several areas of significance from the available literature. These areas have tangible and intangible qualities of historical, environmental or recreational importance for community groups and include: Warriparinga O’Halloran Hill Recreation Park Glenthorne Field River Significant remnant vegetation adjacent to the Beach Road interchange. 17.2.2 Stage 2 – Site assessment, mapping and description of existing character The existing landscape character was mapped and described during numerous site visits to form a baseline reference for determining the potential sensitivity of the landscape to visual change. PAGE 17–1 Duplication of the Southern Expressway | Project Impact Report A hand-held global positioning system (GPS) was used to certify the potential extent of visual change and reference the elevation of visual observation of points along the corridor and surrounding publicly accessible locations, with views of the road corridor. The level of visual modification was predicted to provide a reference to the potential visual effect. Following the site assessment, viewpoints were mapped and supported by a photographic survey to illustrate the landscape character. Table 17.1 lists the classifications derived to predict likely sensitivity levels of adjacent land use areas according to distance, environmental impacts, existing built form and infrastructure, and frequency of views. Table 17.1 Landscape sensitivity to visual change Visual sensitivity levels Nearest visible project Nearest visible project Nearest visible project element 50 metres element 50–150 metres element > 150 metres Cultural significance High High Moderate River corridors High High Moderate Residential High High Moderate Recreational High Moderate Moderate Rural agricultural lands Moderate Moderate Low Commercial Moderate Low Low Industrial Low Low Low The degree of visual change was assessed against the level of contrast and potential integration of the development in the existing landscape. Assessment of the ability of the landscape to absorb the visual effects of the development from viewpoints along the corridor considered distance, vertical and horizontal scale of works, and removal or modification of vegetation and landform created by the duplication. The level of contrast and integration of the development determines the degree of visual change. The visual amenity impacts of the development were then determined using the matrix in Table 17.2. Table 17.2 Visual amenity impacts Visual sensitivity High Moderate Low High High visual impact High/moderate visual Moderate/low visual impact impact Moderate High/moderate visual Moderate visual impact Moderate/low visual impact impact Visual change Low Moderate/low visual Moderate/low visual Low visual impact impact impact PAGE 17–2 Duplication of the Southern Expressway | Project Impact Report 17.2.3 Stage 3 – Mitigation measures and potential treatments Following a review of the potential visual amenity impacts of the project, a series of landscape and urban design strategies were suggested to either mitigate or reduce adverse impacts. These design considerations informed the concept development phase as opportunities and constraints. Figure 17.1 Visual amenity assessment PAGE 17–3 Duplication of the Southern Expressway | Project Impact Report 17.3 Landscape sensitivities and areas of significance A review of relevant literature has identified areas of significance and high sensitivity to the community adjacent to the project area. 17.3.1 Warriparinga Warriparinga, located in the precinct bounded by Sturt Road, Marion Road and Main South Road, Bedford Park, has particular significance to Aboriginal culture. The site also has non-Aboriginal heritage as it was settled in the 1840s. A state heritage listed farmhouse (Fairford House) remains on site (Chapter 9 – Non-Aboriginal heritage). In the late 1990s the site was redeveloped as a wetland designed to filter water from Sturt River before it reached Patawalonga River. It is planted with native vegetation and is now a natural landscape aesthetic in an urban context. Sturt River is a considerable catchment and linear park with strategic plans to provide a recreational linkage from Belair National Park in the Adelaide Hills to Patawalonga and the Coast Park at Glenelg. This site marks a key destination point along this trail. The sense of tranquillity in the parkland aesthetic is a unique quality in the surrounding urban context and one that has high sensitivity to change. 17.3.2 O’Halloran Hill Recreation Park O'Halloran Hill Recreation Park, south of Darlington in the Hills Face area, has a series of recreation walking trails, horse trails, fire tracks, connecting communities to the south. The park also encompasses the Sturt Pistol Club and Southern Field Archers Club, and hosts a venue for model aircraft flying. Although the entire area was cleared and used for grazing for more than 90 years, shady trees throughout the park still provide pleasant picnic spots. The park is characterised by steep north-western and north-eastern gullies. A bluestone quarry near Main South Road, used for many structures in the City of Adelaide, is still visible. There is very little remnant vegetation as the park but it has been revegetated in the recent past through various active revegetation programs. Important stands of Grey Box trees can now be found throughout the park with the addition of native planting associations that are common throughout the Adelaide Hills. The park is characterised by the natural vegetation planting and panoramic views over the Adelaide Plains. It forms a definitive edge to the urban form of the Adelaide Plains. The geological form of the Hills Face location has unique qualities. The Southern Expressway is located in the park’s eastern gully, which reduces the potential sensitivity and visual catchments; however the sensitivity to change would still be considered as moderate. 17.3.3 Glenthorne Glenthorne is located to the eastern side of the existing Southern Expressway corridor, south of Majors Road and bounded by Main South Road on its eastern extent. It encompasses approximately 208 hectares of what is visually classified as heavily modified agricultural landscape. PAGE 17–4 Duplication of the Southern Expressway | Project Impact Report Glenthorne’s rich history includes numerous recorded tenants. It was originally settled in 1839 by Major Thomas O’Halloran, the first Police Commissioner of South Australia, who was subsequently immortalised in the names of the suburb of O’Halloran Hill and Majors Road. Table 17.3 outlines Glenthorne’s ownership history. Table 17.3 History of Glenthorne Year Owner Comments/land use 1839 Major Thomas O’Halloran Settlement 1878 Thomas Porter Renamed O’Halloran Estate to ‘Glenthorne’ 1913 Commonwealth Compulsory acquisition and used by Australian Army for training troops and raising horses 1946 CSIRO Research station 1998 South Australian Government Unknown 2001 The University of Adelaide Subject to Land Management Agreement with State of South Australia The University of Adelaide’s options for the property include developing a vineyard on the site, not a viable option, and revegetating as open woodland. The visual sensitivity of this landscape would be described as moderate to low. 17.3.4 Field River Field River is located to the west of the existing Southern Expressway, south of Landers Road, adjacent to Panalatinga Road interchange. The catchment area includes Happy Valley Reservoir, Main South Road and the Southern Expressway, in a total area of 5,530 hectares. Suburbs bordering the river include Hallett Cove, Sheidow Park, Trott Park, Reynella, Happy Valley and Woodcroft.