Manukau Harbour Coastal Reserves draft management plan
(Avondale/Mt Roskill)
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5.0 Natural and physical environment
5.1 Landscape and natural character
The northern coastline of the Manukau Harbour is a unique and distinctive landscape characterised by its landform and
vegetation pattern. The landform is comprised of a steep coastal ridge and subsidiary ridges running down to the headlands and
bays, with steep cliffs behind the bays and small beaches. The extensive intertidal mudflats are also a dominant feature
of the coastline and provide low tide pedestrian access. The coastal edge is well vegetated and gains much of its
character from the combination of strong landform and regenerating coastal forest. The coastal edge has been identified as
regionally significant in the Auckland Regional Plan: Coastal and the coastline was rated as having 'significant sensitivity' in
the Auckland Urban Area Landscape Assessment
[3].
The landscape character of the area is also strongly influenced by the coastal processes. The coastal edge is also one of the
most visible and elevated sections of the Manukau coastline and consequently views to and from the coast are highly important.
The landscape is highly visible from Onehunga, Mangere, Mangere Bridge and from State Highway 20, being the northern gateway to
the city from the airport.
Looking across the Manukau Harbour towards Waikowhai Bay.
Waikowhai Park.
The reserves are predominantly natural in character and the integrity of them is largely due to their continuous and
relatively undeveloped state. The coastal edge also acts as a valuable buffer between the harbour and the urban development beyond.
Maintenance of this buffer is important in the restoration of the quality of the harbour.
5.2 Geology and coastal processes
The Resource Management Act recognises the significance of the coastal environment and the Auckland Regional Plan: Coastal
identifies White Bluff as a Coastal Protection Area 1, being one of the best exposures of complexly deformed Waitemata Group
rocks in the Auckland area.
The coastal edge is a dynamic environment characterised by a number of physical and ecological processes and is subject to
constant change. The northern coastline of the Manukau Harbour between Green Bay and Hillsborough Bay is dominated by
the hard rock shoreline consisting of Waitemata strata overlain with soft soils. The cliffs are comprised of the eroding scarp of an
upraised block of Waitemata sandstones and mudstones. The easy slopes have a low fertility, while the steeper and unstable mid-slopes
are more fertile. The very steep eroding slopes that drop away to the harbour develop little topsoil. The coastal slope soils
appear to have been derived from the eroding Waitemata rocks and the area appears to have escaped the volcanic activity on the
Auckland isthmus.
The coastal edge is subject to a number of erosion processes including wave erosion, bio-erosion on the rock platform,
land based erosion, mass movement and weathering erosion. Wave erosion is not dominant due to the low wave energy in
the inner Manukau Harbour and cliff face erosion is not significant. Sand beaches are not dominant around this coastline
having being washed away either by water runoff from residential development or increasing tidal currents within the Wairopa Channel.
Significant earth slides have already been recorded in Wattle Bay Reserve, Hillsborough Cemetery and Hillsborough Park,
within Wesley Bay Reserve / Waikowhai Park and the eastern slopes of Blockhouse Bay. Large areas of active instability are prevalent
within the Waikowhai Bay, Wesley Bay and Wattle Bay reserves and Hillsborough Reserve. Smaller incidents along the coast have also
occurred. Erosion of the headland at Te Whau Point is degrading the pa site and middens.
Erosion has the potential to significantly impact on the utilisation of the coastal reserves, and slope stability within the
reserves needs to be continually reviewed.
Erosion of the cliffs at Te Whau Point.
5.3 Water quality
The water of the Manukau Harbour is characterised by high turbidity due to the harbour's shallow nature and predominantly
muddy brown sediments. Stormwater has a significant impact on the water quality and is the largest uncontrolled source
of discharge into the harbour.
Within the coastal reserves there are a number of natural overland flow paths which discharge into the harbour and several
streams including the Wairaki Stream, which terminate along the foreshore. The reserves also contain a number of stormwater
pipes and outfalls which discharge into the harbour.
Maintaining the quality of the coastal water is an important aspect of managing the coastal environment. Coastal water quality can
affect the health of coastal ecosystems and many of the amenities associated with the coastal environment such as recreation and
cultural heritage.
The coastal interface.
5.4 Vegetation and wildlife
The coastal edge of the Manukau Harbour contains significant remnants of Auckland's indigenous plant communities. More than 213
native plant species, including shore plants have been identified along the coast. The strip of coastal forest extends from Green Bay
to White Bluff creating an ecological corridor for a range of native flora and fauna, promoting natural processes such as seed
dispersal and wildlife movement from the Waitakere Ranges along the Manukau cliffs and into the coastal reserves.
The easy upper slopes have been extensively modified by burning and clearing of the past 100 years. No original representative
vegetation of landform remains along this forest strip. The vegetation lies on Waitemata sandstone, a deposit of sand
and silt laid down under the seas and the ridge tops and easy slopes have soil of low natural fertility further impoverished by
kauri forest. The steeper land is more fertile through soil movement enabling the subsoil to yield more nutrients.
As a result of these geological differences, three well defined vegetation habitats exist:
- gumland vegetation (mainly manuka) on the easy slopes;
- regenerating forest (mapou and mahoe developing to puriri-kohekohe forest) on the intermediate slopes; and
- pohutukawa forest on the coastal scarps
Whilst most of the vegetation has been affected by fire in the last 100 years, there has been a progression back to
the characteristic vegetation in each habitat with the addition of some exotic species. The exotics have been planted
and include pines, wattles and eucalypts. Their vigorous growth patterns are an issue for the long term viability of the
regenerating native bush as they can play a role in terms of suppression and establishment of indigenous species,
ageing nature, safety aspects and impact on slope stability.
The low fertility soils today support gumland plant associations, dominated by manuka, mapou, karamu and hangehange with a dense
understorey of typical gumland ferns and sedges. The best example of this vegetation is in Manukau Domain. The
intermediate slopes of the reserves support a range of regenerating coastal forest types, the most common being the
mapou/mahoe forest and more mature pockets of kohekohe/puriri forest. The understorey vegetation on these slopes is
the most diverse of the forest types present and supports a wide range of ferns, shrubby species and regenerating broadleaf trees.
As with much of the area, the intermediate slopes have suffered from vegetation clearance in the past. The pockets of more mature
vegetation however may have been afforded some protection by the relative steepness of these slopes. Some good examples of
this vegetation type are found in Wattle Bay and Waikowhai Park. The coastal scarps are dominated by pohutukawa forest and other
coastal species including five-finger, mapou, karo, coastal astelia, houpara, karamu and taupata. A prime example of this vegetation
is around Te Whau Point at the western end of the management plan area.
Low coastal herbfields grow along the coast on exposed damp sites just above the high tide mark. This saline vegetation grades
from the occasional area of flax, searush, jointed rush and rengarenga through to herbfields dominated by samolus, selliera,
glasswort and wild celery. Young mangrove vegetation is also present.
The botanical quality and conservation status of all the reserves within the management area is high due to the scarcity of intact
coastal vegetation within the Tamaki Ecological District. Of particular significance are the native forest remnants at Wattle Bay
and Wesley Bay, with these being the largest remaining areas on the Auckland isthmus. Wattle Bay contains the largest pohutukawa forest
on the isthmus and also contains a large number (747) of different species of bettle including 646 native species.
Captain's Bush at Wesley Bay represents part of the original Auckland flora that largely escaped destruction during
volcanic eruptions and clearance during Maori and European settlement. It is the best representative of the original
kohekohe/puriri/kowhai forest in the forest remnants that stretch along the coastal edge. It also contains a number of
native bird species including kaka and tui.
The vegetation is a significant natural feature of the coastal reserves
A point worthy of note regarding these pockets of representative vegetation is the conspicuous absence of regenerating kauri.
Kauri forest was once common in these coastal environments and helped form the gumlands present today. It is significant that this
species is now largely absent from the management plan area and replanting with this pioneer species will contribute to comprehensive
and representative restoration of the coastal forest.
The coastal edge also contains a number of remnant wetlands with indigenous plant species, most notable being the wetland at
Wattle Bay. These wetlands have developed at the mouths of small streams draining into the Manukau Harbour from
the coastal reserves behind. They provide a valuable habitat for flora and fauna as well as serving as a filtration system for
water runoff, before entering the wider harbour. Small areas of saline wetland vegetation are present in the
inter-tidal zones of many of the bays. These provide some valuable habitat for native fauna and enhance the natural
ecotone between the marine, freshwater and terrestrial ecosystems.
The Manukau Harbour forms one of the most important wintering grounds for wading birds in New Zealand and the south-western Pacific.
It is considered to be of international significance and has been identified as a Site of Special Wildlife Interest of
"Outstanding" significance. Hillsborough Bay and Motukaraka Bank at Green Bay form two of these significant low-tide
feeding areas for wading birds.
5.5 Weeds and pests
The coastal forest is very sensitive to the impact of urban development. This has resulted in the spread of many weed species,
some of which threaten the integrity of the forest ecosystem. The main sources of infestation have been on the boundaries with
residential properties due to illegal dumping of organic material and lines of clearance within the forest such as
roads and paths. Wild ginger, wandering willie, bamboo, honeysuckle, privet, wattle and jasmine are particularly invasive species.
This weed dispersal is a major concern, exacerbated by the close proximity of the adjoining residential properties and
the illegal depositing of garden waste into the reserves.
Waikowhai Park, Avondale South Domain, Hillsborough Reserve and Te Whau esplanade reserves were considered high priority natural
areas requiring weed control in Council's Weed Management Policy (1999). Captain's Bush, Hillsborough Cemetery, Himalaya Reserve,
Lynfield Cove, Sylvania Crescent Reserve and Wairaki Stream Reserve were considered medium priority areas.
Weed control is currently staged and prioritised according to the level of infestation and available funding for replanting.
Replacement planting is undertaken immediately after exotic removal. A weed-free status is a high
priority for the most invasive species, that is, those that threaten long-term viability. Long term weed control is involving a
concerted effort to reduce herbicide use and adoption of non-herbicide methods. Weed-led and site-led weed control is currently
applied based on site requirements.
Local community input into weed management and issues of spread is critical. Mechanisms by which this could be achieved
include informative leaflets, provision of free weed bins, raising the profile of the reserves in local schools, encouraging local
action groups and discouraging weed encroachment from neighbouring properties.
Pacific oyster shell build-up along the coastal edge
Pacific oysters have become a problem along the foreshore, reducing the amenity of the rocky shore and hindering low-tide pedestrian
access along the foreshore. The Auckland Regional Council promotes the removal of Pacific oyster shells from beaches where they
are creating a community concern.
Possums are also prevalent throughout the area to the detriment of the native vegetation. In 2004 a community possum and rat
control programme commenced in Waikowhai Park. Plans are afoot to expand the programme to include neighbouring
reserves. Waikowhai Park is earmarked as a key ecological node linking the Waitakere Ranges and Mutukaroa / Hamlins Hill.
Stoats are a problem in some areas and rats and feral cats have been identified in the reserves in particular, Waikowhai Bay
and the coves below Granny's Bay and Wesley Bay.
5.6 Recreation and use
The coastal reserves are well used and contribute to the attraction and accessibility of the coastal environment.
The reserves are the focus for a number of formal, informal, passive and active recreation uses. The recreational use of the reserves
is largely determined by the topography and bush cover of the area. The natural characteristics of the reserves are
conducive to informal recreation with the public enjoying the natural assets of the coastal edge.
Due to the physical nature of the coast, the majority of activities are passive in nature - bush walking, visiting the beach,
picnicking and barbeques, informal games, dog exercising, bird watching, fishing, orienteering, exercising, sightseeing and viewing.
More active recreation occurs in the open park and grassed areas of Waikowhai Park, Blockhouse Bay Beach, Manukau Domain and
Taylors Bay.
Enjoying the view at Blockhouse Bay
The reserves' proximity to the harbour facilitates easy access to water-based recreational activities however the
topography of the coastline, tidal nature and limited access restricts options for boat access. Boat ramps are located at
Blockhouse Bay Beach, Flounder Bay and Faulkner Bay. The Blockhouse Bay Sailing Club is located below Te Whau Point, with
clubroom facilities, launching ramp and slipway on the foreshore.
Children's play areas are located at Taylor's Bay, Lynfield Cove, Blockhouse Bay Beach and Waikowhai Park.
A large number of local residents frequently use the coastal reserves throughout the year for informal recreation with wider use,
particularly over the summer months, by visitors from throughout the region.
The primary use of the coastal reserves should be for passive recreation, enabling the public to enjoy the natural assets of the coast.
As coastal water quality improves, public access to and along the coast is enhanced and coastal restoration is undertaken,
there is likely to be increased recreational use of the coastal reserves. Increased use of the reserves will need to be carefully
managed to ensure that their natural values and characteristics are not degraded.
Taylors Bay Reserve and play area
5.7 Pedestrian access and linkages
The maintenance and enhancement of public access to and along the coast is a matter of national importance under the
Resource Management Act. Public access is generally provided by esplanade reserves or strips, access strips, easements and
covenants.
A number of pedestrian walkways have been established to the coast, along the coastal edge and within the coastal reserves.
At present the walkways are not continuous across the area, hindered by private properties or steep topography
and vegetation. This is particularly so between Flounder Bay and Lynfield Cove,
between Manukau Domain and Himalaya Reserve and between Granny's Bay and Aldersgate Reserve. There is widespread public interest in a
continuous walkway along the coast.
Pedestrian access tracks appropriate for the reserve use
There are a number of established walks throughout the coastal reserves - around Blockhouse Bay, Lynfield Cove, Hillsborough Bay and
Wesley Bay to Wattle Bay. Low-tide pedestrian access around the coast is available along the rock shelving providing a different
recreational experience. Coastal pedestrian access is currently blocked between Lynfield Cove and Flounder Bay due to the absence of
esplanade reserves along this coastal strip.
Disabled pedestrian access is restricted due to the nature of the terrain, however opportunities need to be explored to
provide recreational experiences of the coastal environment for mobility impaired users.
Existing pedestrian access points into the reserves should be assessed on the basis of their appropriate location, visibility and
signage, ease of use and standard of maintenance and additional entry points and pathway access into the
reserves should be provided where required.
Investigations into the most efficient method of providing pedestrian access throughout the coastal reserves should be undertaken,
whether it be formed tracks, markers or free roaming. The design and construction of the tracks should be appropriate to their
location and level of use and should not compromise the values of the coastal reserves. Consideration must also be given
to surface selection in terms of reserve character, minimisation of water runoff and impact on water quality.
Paved access paths in high use areas
Public access should not be provided to all parts of the coastal edge. Areas of high ecological, cultural or conservation value
should be avoided. Similarly pedestrian access should not be provided where public safety is an issue, for example, Te Whau Point
cliffs, or in areas where steep terrain would make construction difficult and tracks could exacerbate erosion.
Directional signage should be improved to the entry points, exit points and within the reserves to facilitate easier
pedestrian movement. Signage should also focus on the linkages and connections between the reserves, including low-tide pedestrian
access and inland options.
5.8 Vehicle, boat access and parking
Hillsborough Road is the main source of access for the coastal reserves with most served by streets leading directly off it.
Vehicle access is provided into a number of the reserves with car parking at Blockhouse Bay Beach, Lynfield Cove, Waikowhai Park,
Hillsborough Reserve and Taylors Bay. Others have road frontages with on-street car parking including Taunton Terrace, Avondale South
Domain, Lynfield, Manukau Domain, Aldersgate and Belfast reserves. In some cases, however, road frontage is minimal - Wattle Bay,
Lynfield Cove and Granny's Bay reserves or non-existent - Captain's Bush and Bamfield Foreshore reserves.
Boat launching ramps are located at Blockhouse Bay Beach, Faulkner Bay (Waikowhai Park) and Flounder Bay
(adjacent to Avondale South Domain). Faulkner Bay is the only all-tide boat ramp on the northern side of the Manukau Harbour and
therefore a very popular and well used facility.
Car parking requirements within the reserves should be assessed in light of the existing facilities and likely future demands.
Formed car parks should be restricted to those reserves with an identified need, including those with public facilities such as
picnic areas, toilets/changing rooms, children's playgrounds or boat launching ramps.
Off-street parking adjacent to Wattle Bay Reserve
5.9 Buildings, facilities and coastal structures
Limited development of the coastal reserves, including structures, is appropriate in some locations to enhance recreational use.
However, development must not compromise the integrity of the reserves or the wider coastal environment.
A limited range of buildings, facilities and structures are located within the coastal reserves. Public toilets are provided at
Blockhouse Bay Beach, Waikowhai Park and Taylors Bay. Boat launching ramps are provided at Blockhouse Bay, Faulkner Bay and
Flounder Bay.
A number of unauthorised public and private coastal structures are located along the coastal edge including boat ramps,
boat sheds, seawalls, access steps, several baches, garden sheds, jetties and a sewer pump station. Auckland Regional Council is
currently addressing the issue of coastal structures which do not have the necessary coastal permits with a view to having them
validated or removed.
'Boatman's shed' at Taylors Bay
Well designed, sited and integrated buildings and facilities can enhance the reserves and the public use and enjoyment of it,
others can detract from and have severe detrimental effects on the coastal environment. Buildings and facilities, such
as toilets and shelters, should be kept to a minimum number required to serve the needs of the reserve users.
Boatsheds and slipway at Sandy Bay
5.10 Furniture and signage
Furniture within the coastal reserves includes seats, rubbish bins, bollards, picnic tables, barbeques and signs.
Signs and site furniture should be provided to enhance the use of the reserves where appropriate. An integrated approach to
signage and furniture should be developed to cover the complete range of sign design, style, colour, use, placement and maintenance
for all signage including:
- entrance signs
- directional signs
- walkway / trail markers
- informative signs
- interpretive signs.
At present there is a lack of signage to indicate connections between walkways and entrances into the reserves, in particular the
secondary pedestrian access points. A number of the road frontages to the reserves have signs but no pedestrian access into the
reserve which is confusing to the user. Signage should also indicate the extent and nature of the access, including low-tide
pedestrian access availability and level of agility.
Well designed 'Living Parks' signage enhances the reserves
5.11 Adjoining land use
Land adjacent to the coastal reserves is zoned Residential 5 and Residential 6A in the District Plan. Residential 5 zones are
generally characterised by low rise, low density housing with relatively generous areas of open space. Residential 6a
is characterised by medium density housing and recognises the opportunity for further development while retaining a reasonable
level of amenity.
The adjoining residential properties can have an impact on the natural and landscape values of the reserves. Adjoining landowners
should be encouraged to appreciate and enhance the valuable resource that the reserves provide and work in with
Council to the benefit of the landowners and the general public. It would be of mutual benefit to all parties to establish good
relationships in terms of the defined boundaries and individual expectations.
While some residential activities such as planting enhance the aesthetic qualities of the reserves, others such as poorly
constructed fences and retaining walls can be detrimental. Problems have been encountered in the past through the dumping
of garden waste within the reserve boundaries leading to noxious weed invasion. Other problems include encroaching onto
reserves for car parking, trailer storage, access to construction sites and water runoff.
The northern coastline of the harbour is a transmission line route with pylons and overhead wires traversing the reserves in a
number of places. Structures such as these detract from the natural character values of the coastal edge.
5.12 Leases and Licenses
There are no current leases operating within the reserves.
Due to the largely natural state of the reserves and the emphasis on informal and unstructured recreational use,
the provision of any future leases or licences should be carefully assessed. It is essential to monitor and regulate any future
leases and licenses to protect and preserve the natural qualities of the reserves, whilst providing a minimum of compatible
facilities for the enjoyment of the reserve users. No leases or licences would be entered into for scenic reserves.
[3] Auckland Urban Area Assessment, ARC, 1994
