Assessment of Landscape, Visual and Natural Character Effects

Transcription

1 Assessment of Landscape, Visual and Natural Character Effects Consent Footprint Amendments Mangamaunu Half Moon Bay Okiwi Bay South

2 Report prepared for: New Zealand Transport Agency and KiwiRail Holdings Ltd Report prepared by: Bron Faulkner (Landscape Architect) Technical Reviewed by: Yvonne Pfluger (Landscape Architect) Date: 2

3 Contents 1 Introduction 4 2 Assessment of Coastal Natural Character, Landscape and Visual Effects Mangamaunu Half Moon Bay Okiwi Bay South 9 3 Effects Summary and Design Recomendations 11 3

4 1 Introduction This assessment has been prepared to assess the potential landscape, natural character and visual effects, in support of the consent application for the proposed amendments to the consent footprint at the following locations on the coastal route: 1. Mangamaunu 2. Half Moon Bay 3. Okiwi Bay South 2 Assessment of Coastal Natural Character, Landscape and Visual Effects This assessment considers landscape, visual and coastal natural character effects of the proposed works. It draws on the district and regional landscape descriptions detailed as part of the previous assessments for this project. Natural character considerations combine the biotic, abiotic and experiential elements of the coastal environment. As such, the assessment of natural character effects draws on the Ecological Assessment prepared for these works. Assessment Methodology Assessing landscape, visual and natural character effects requires a thorough understanding of the existing landscape and importance or value of the landscape. Where applicable, the existing environment includes the previously consented, but as yet unbuilt, design. Consequently, the assessment considers the incremental change between previously consented and proposed designs. Using the existing environment as a baseline, a determination of sensitivity and the magnitude of change which results from a proposed development can be made to determine the overall significance. Sensitivity depends upon the degree that a particular landscape or feature can accommodate change; the more natural (less modified) a landscape is, the higher its sensitivity to change. The magnitude of change judges the amount of change that is likely to occur to existing areas of landscape, landscape features, or key landscape attributes. In undertaking this assessment, it is important that the size or scale of the change is considered within the geographical extent of the area influenced and the duration of change, including whether the change is reversible. The significance of effects resulting from a proposal take into account the sensitivity of the existing landscape to change, the magnitude of the proposed change and any proposed mitigation. The significance of effects is expressed in terms of a seven point scale from Very Low to Very High 1. Very Low Low Moderate Low Moderate Moderate High High Very High In accordance with this methodology, an assessment of the three sites subject to this application is contained below. 1 Seven point scale adapted from NZILA s Best Practice Note. 4

5 2.1 Mangamaunu The already consented design for the shared path and access road extended onto the beach at Mangamaunu and included coastal protection in the form of a vertical seawall structure (or similar) along the coastal edge. To provide for additional design options including a gently sloping revetment structure using natural rock armour, the new consent line will shift seaward an average of 5-10m (up to a maximum of approximately 16m) from the previous permanent consent line. This permanent works area does not extend below MHWS and all temporary construction works will be carried out above MHWS. The sloping embankment will likely be constructed of fill overlaid with rock protection. A foundation (likely 3-4m deep) will likely need to be constructed at the toe of this embankment for stability. Cobbles excavated from within the footprint of works will potentially be used to cover this foundation and extend up the toe of the embankment to shape it into the existing beach. Access will be possible down the sloping embankment and onto the beach to access the surf break. Site Description Existing Environment SH1 and the railway occupy most of the wide coastal platform which is backed by old coastal cliffs and farmland on the inland side. The narrow strip of land between the railway and the coast is subject to the existing consented design including potential structures along the coast to provide space for an access road, shared path and amenity area with carpark and toilet block. The intertidal and coastal margin area comprises rock cobbles and stony/sandy beaches that curve around the southern headland into Mangamaunu Bay. Offshore of this coast are the popular and nationally recognised surf breaks at Mangamaunu and the Meatworks (recognised in the New Zealand Coastal Policy Statement). As such this shore is well used for recreational activities and frequently experienced from the sea by surfers. The proposed amendment to the existing consented line extends down to MHWS for approximately 410m of the coast to the south of the headland and 160m north of the headland. Natural Character A rock revetment will occupy more of the cobble beach area landward of MHWS than a vertical wall structure, and as such a structure of this nature will be a larger in scale modification of the coast than the consented design. While the sloped and textured nature of a rock revetment structure may appear more natural than a vertical concrete block structure, its scale and extent will still be a dominant man made element of this particular coastline. A revetment structure together with the widened platform will impact on the sense of naturalness experienced by people visiting the coast. Natural Character Sensitivity of coast: Moderate High (previously consented amenity area, shared path/access road) Magnitude of Change: Moderate High Significance of Natural Character Effect: High Landscape Effects This area is not identified as an ONL. The coastal edge is well used by surfers to access the surf breaks, and ride the waves. The consented amenity area, associated road access and shared path will increase the ability for the public to access this part of the coast. Subsequently this will be an area of high recreational use with carparks, toilets and site furniture. The proposed works will not change this character, but the formalised coastal edge may be rock revetment rather than a vertical seawall type structure. Revetment will facilitate easier access down to the beach than a more vertical structure. 5

6 However, the extended footprint will reduce the ability for access along the beach especially at high tide. Unlike the steep, craggy rocky bays and headlands elsewhere in the project, the near uniform rounded cobbles and rocks, and absence of steep coastal slopes behind the beach give this shore a distinctly low elevation and streamlined profile. Consequently this part of the coast has limited capacity to be able to absorb a new structure such as this without changing the character of the coastal edge. Visual Effects Landscape Sensitivity: High Magnitude of Change: Moderate High Significance of Landscape Effect: Moderate High The visual change of the seaward shift of the footprint will be apparent from many locations along the Mangamaunu coast, transport corridor, shared path and amenity area as well as from the surf reef off shore. However, a textured and sloping rock revetment would appear slightly more natural than a more vertical structure. As described above the streamlined profile of this beach provides less capacity to visually absorb a structure of this scale (compared to a steep rocky shoreline). Visual Sensitivity: High (nationally significant surf break) Magnitude of Change: Moderate High Significance of Visual Effect: High Recommendations Detailed design should seek to minimise the height, length and seaward extent of the new structures. Preference for use of natural rock revetment rather than man made units and sea walls. If concrete revetment units are to be used they should be angular in form rather than cylindrical. Consider design options of the revetment surface to facilitate access from the shared path to the coast. 6

7 2.2 Half Moon Bay The existing consented design at Half Moon Bay included a seaward realignment with a seawall extending along the full seaward edge. The proposed design at Half Moon Bay provides for the option of a revetment solution instead of or in combination with a seawall. To allow for this the consent footprint will increase in the order of 20-30m along an approximately 450m stretch at the head of Half Moon Bay. Further north, the consent footprint will be increased an average of approximately 10m along three sections totalling 1050m in length. A 5m temporary construction zone will be used outside of this permanent works area where required. Site Description Existing Environment This stretch of coast line forms a central part of the Kaikoura Coast ONL with distinctive rocky headlands and shore platforms at the base of the steep forested coastal slopes (now dominated by large slips). This assessment assumes the previously consented sea wall and shared path is part of the existing environment. As such the naturally rugged landward edge of the coast has been modified by the presence of the linear seawall, widened shore platform and shared path. Overall a revetment option appears to more closely follow the curving alignment of the original shoreline, than the consented seawall which would follow a more or less straight line along the coast. Generally the revetment toe is landward of MHWS with the exception of inner Half Moon Bay where the footprint extends beyond MHWS. Natural Character The extension of the footprint seaward of the previously consented line, will further impact on the natural features and processes of the coast particularly at the head of the bay. However the additional occupation of the shore platform area is still relatively small compared to the consented design. The proposed alignment will occupy space beyond MHWS in Half Moon Bay with the loss of much of the remaining beach at the head of the bay. The sloped and textured nature of a revetment option offers some benefits over the vertical seawall in terms of natural character, as its profile and rough texture appears to more closely approximate a natural coastal feature and it offers better potential habitat, albeit still a highly modified element. However, the benefits are offset by the loss of the coastal edge under the generally wider revetment foot print. Together this will continue to reduce the naturalness of the coast. Natural Character Sensitivity: Moderate High Magnitude of Change: Moderate Low Significance of Natural Character Effect: Moderate Low Landscape Effects The site lies within an identified regional ONL. The landscape values that underpin the ONL include the sequence of highly natural bush-clad steep slopes to the shoreline, including the state highway and railway. The proposed works will not impact on the ONL values when considered at this wider scale. The wider transport corridor platform will be particularly evident where the new footprint occupies the beach down to and beyond MHWS at the head of Half Moon Bay. 7

8 A sloping textured revetment is a slightly better option than a seawall in terms of landscape character. The sloping and highly textured nature of the revetment as it undulates along the coastline will result in a more naturalised built element that contrasts less with the rocky coastal environment than a smooth and vertical seawall. In addition the sloping revetment face potentially enables access to the coast from the shared path. Landscape Sensitivity: Moderate High Magnitude of Change: Moderate Significance of Landscape Effect: Moderate Low Visual Effects The visual effects of the potential modifications would be relatively contained from distant views along the coast but easily viewed from the close proximity of the shared path, road and rail. The visual change resulting from the widened flat platform will be notable. Overall, the revetment structures would have similar visual impact in the coastal environment as the seawalls would, as they will appear as a single element of an engineered nature and planar lines contrasting strongly with the natural organic nature of the rugged rock coast. However, the textured and sloping surface of the revetment could be considered a better visual outcome than a smooth vertical seawall. Visual Sensitivity of Bay: High Magnitude of Change: Moderate Significance of Visual Effect: Moderate Low Recommendations Detailed design should seek to minimise the height, length and seaward extent of the new structures. Preference for use of natural rock revetment rather than manmade units. If concrete revetment units are to be used they should be angular in form rather than cylindrical. Consider design options of the revetment surface to facilitate access from the shared path to the coast. 8

9 2.3 Okiwi Bay South The existing consented design at the southern end of Okiwi Bay comprised a rock revetment structure extending into the CMA to provide space for SH1 and the MNL to be realigned seaward around Slip 8. Two additional design options are proposed for Okiwi Bay South, both require a seaward shift of part of the revetment alignment. The two proposed options are: Option 1: Realign and straighten the road and rail to achieve a pre-earthquake level of service and install rock revetment coastal protection on the seaward side. Option 2: Retain the existing post-earthquake alignment but install rock revetment coastal protection on the seaward side to protect the corridor long term. To provide for both of these options the permanent works consent line will on average be shifted approximately 10m (up to a maximum of 17m) beyond the existing consent line along a length of approximately 200m (reduced from the originally proposed 1km length). An additional 5m temporary construction zone outside of this permanent works area will be used where required. The armour of the revetment structure will be either natural rock or concrete X blocks. Site Description Existing Environment This assessment assumes the previously consented revetment is part of the existing environment. As such the naturally rugged landward edge of the coast and the south end of Okiwi Bay beach would be replaced with a more or less linear built structure. Generally the consented revetment is at or above MHWS. The proposed revetment extends beyond MHWS. Natural Character Effects The extension of the footprint seaward of the previously consented line, will further impact on the natural features and processes of the coast with the loss of an area rock platforms. The scale of the proposed expansion of the revetment footprint is relatively small compared to the consented work. It will not impact further on the end of the Okiwi Bay beach proper, but will expand beyond the MHWS for approximately 200m. Consequently there will be some loss of intertidal area. The profile and texture of the proposed revetment will be similar to the consented structure, with the addition of the shared path on top. The ecological assessment assesses the level of ecological effects as Moderate due to loss of variable oyster catcher habitat and potential seal haul out habitat. Natural Character Sensitivity of coast: Moderate High Magnitude of Change: Low Significance of Natural Character Effect: Moderate Low Landscape Effects The site lies within an identified regional ONL. The landscape values that underpin the ONL include the sequence of highly natural bush-clad steep slopes on the landward side of the state highway and railway. The additional design options will not impact on the ONL values when considered at this wider scale. While the proposed works will increase the bulk of the modified coastal edge the form and texture of the revetment will be similar to the consented design. Overall, the proposed works will not significantly change the landscape character of this part of the coast. 9

10 Landscape Sensitivity: Moderate High Magnitude of Change: Low Significance of Landscape Effect: Low Visual Effects The revetment structures, and transport infrastructure in the widened coastal platform will be most visible from the shared path, SH1 and Okiwi Bay beach. While the seaward alignment of a section of the revetment will change, the appearance of the proposed structure will be very similar to the already consented one in terms of its scale, form, colour and texture. From more distant locations such as the middle or northern end of the beach the proposed structure would be visually similar to the consented one. Visual Sensitivity: Moderate to Low Magnitude of Change: Low Significance of Visual Effect: Low Recommendations Detailed design should seek to minimise the height, length and seaward extent of the new structures. Where a combination of seawall and revetment structures are required along a stretch of the coast the transitions should be designed to be integrated gradually to avoid abrupt changes in profiles and materials. Preference for use of natural rock revetment rather than man made units and sea walls. If concrete revetment units are to be used they should be angular in form rather than cylindrical. Consider design options of the revetment surface to facilitate access from the shared path to the coast. 10

11 3 Effects Summary and Design Recomendations The significance of effects consider the incremental change between previously consented designs and proposed designs (where applicable). Project Significance of Natural Character Effects Significance of Landscape Effects Significance of Visual Effects Mangamaunu High Moderate High High Half Moon Bay Moderate Low Moderate Low Moderate Low Okiwi Bay South Moderate Low Low Low Project Mangamaunu Design Recommendations Detailed design should seek to minimise the height, length and seaward extent of the new structures. Where a combination of seawall and revetment structures are required along a stretch of the coast the transitions should be designed to be integrated gradually to avoid abrupt changes in profiles and materials. Preference for use of natural rock revetment rather than man made units and sea walls. If concrete revetment units are to be used they should be angular in form rather than cylindrical. Consider design options of the revetment surface to facilitate access from the shared path to the coast. Half Moon Bay Detailed design should seek to minimise the height, length and seaward extent of the new structures. Where a combination of seawall and revetment structures are required along a stretch of the coast the transitions should be designed to be integrated gradually to avoid abrupt changes in profiles and materials. Preference for use of natural rock revetment rather than man made units and sea walls. If concrete revetment units are to be used they should be angular in form rather than cylindrical. Consider design options of the revetment surface to facilitate access from the shared path to the coast. Okiwi Bay South Detailed design should seek to minimise the height, length and seaward extent of the new structures. Where a combination of seawall and revetment structures are required along a stretch of the coast the transitions should be designed to be integrated gradually to avoid abrupt changes in profiles and materials. 11

12 Preference for use of natural rock revetment rather than man made units and sea walls. If concrete revetment units are to be used they should be angular in form rather than cylindrical. Consider design options of the revetment surface to facilitate access from the shared path to the coast. 12