Brooklands residential red zone: Summary of Technical Information as at October
2016
Area ID: 18A,
18B, 18C
Purpose of this document:
The following information provides a summary of the local environmental values, conditions and potential
hazards. The information has been gathered using the best available technical data held by a number of
agencies and organisations. It does not identify or assess land use options or the feasibility of land uses.
The information in this document is not, and should not be interpreted as, a pre-determination,
recommendation or decision about future use. No decisions regarding the future use of this land have
been made.
Overview of Brooklands residential red zone (Area 18):
Area 18 is approximately 78 hectares in area and is surrounded by the Brooklands Lagoon to the east and
the Styx River to the north and west. To the south-east Area 18 adjoins Seafield Park and an area of rural
land. The surrounding area is noted in the proposed Christchurch Replacement District Plan to have high
existing environmental values. There is forestry and pastoral land use in the area to the south and east and
a relative absence of built features. This area falls within an expansive flood ponding area located between
the Styx River and the Te Tai o Mahaanui/the Christchurch Coast. Consequently coastal processes
dominate the geographic context and there are large areas of adjoining and proximate reserves. Stopbanks
to the north of Brooklands provide protection to this locality from flooding from the Waimakariri River.
There are also tidegates within the stopbank at the outlet of the Styx River providing protection from tidal
water flowing up the Styx River. This infrastructure is owned by Environment Canterbury.
Area 18 is susceptible to a number of natural hazards, which can potentially occur either in isolation or
collectively, leading to a number of adverse cascading effects. The risk from many of these hazards will
increase over time due to the accelerating effects of sea level rise.
In the longer term, with sea level rise, susceptibility to natural hazard risks, and the consequential increase
in ground water levels, it may be increasingly difficult to maintain underground horizontal infrastructure in
this location.
Location Map
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Natural Environment and Cultural Setting and Features
Natural
Environment
Area 18 is adjacent to three Sites of Ecological Significance (SES’s) as identified in
Chapter 9 (Natural and Cultural Heritage) Appendix 9.1.4.1 of the notified version
of the proposed Christchurch Replacement District Plan1:

Brooklands Lagoon (site ID no. SES/LP/5)
'The Brooklands Lagoon SES is an originally rare ecosystem that contains
indigenous vegetation communities that have been greatly reduced within the
Low Plains Ecological District, and is also of local, national and international
importance in terms of it supporting a representative assemblage of indigenous
and migratory birdlife, including 20 threatened, At-Risk or uncommon species. '

Styx river Mouth Wetlands SES (site ID no. SES/LP/20)
'The Styx River Mouth Wetlands SES is significant because it contains a large
area of wetland habitat vegetation that is representative of the Low Plains
Ecological which provides important habitat for several threatened species.'

Styx River SES (site ID no. SES/LP/23)
'Site contains remnant wetland vegetation that is representative of the natural
diversity of the Low Plains Ecological District, and supports the At Risk longfin
eel.'
Adjacent to inanga spawning site (CCC spawning site location “Reach ID2”, Styx
River, immediately upstream of the tide gates).
The presence of bird nesting islands in the constructed wetland "Seafield Lagoon"
adjacent to Area 18 are noted.
Waterways
Within Area 18 and 18A there are three waterways: Sullivans Drain, Barkers Drain
and Lower Styx Drain. These waterways are subject to minimum setback
requirements (refer to Chapter 6 of the notified version of the proposed
Christchurch Replacement District Plan)2.
Area 18 is also adjacent to the Styx River (a Downstream Waterway with a 30m
setback), and Kainga Stream (an Environmental Asset; with a 7m setback).
Groundwater –
depth below surface
Current median groundwater depth is predominantly at about 1m below the
surface but can rise to the surface in wet conditions.
Median groundwater depth with 1m sea level rise is anticipated to be
predominantly at the surface.
Coastal Marine Area
Immediately adjoins the Coastal Marine Area Boundary to the east.
1
The Independent Hearings Panel is yet to issue its decision on Chapter 9 hence the provisions and related maps are subject to change.
A resource consent is required from the Christchurch City Council to fill, excavate or build within this setback. Furthermore, the Independent Hearings Panel is
yet to issue its decision on Chapter 6 hence the provisions and related maps are subject to change.
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Public Facilities
Public facilities within Area 18 include tennis courts and public toilets in the
Domain in addition to a boat ramp and associated parking area adjacent to the
Lagoon.
Reserves
There is significant reserve land surrounding Area 18. This includes:





Seafield Regional Park located along the western shore of Brooklands
Lagoon
Styx River Mouth Conservation Reserve
Brooklands Spit (east of the Brooklands Lagoon)
Styx River Boating Reserve, three areas of reserve connecting Brooklands to
the Styx River
Lower Styx River Conservation Reserve located alongside the Styx River,
which includes the Source to Sea walkway (this is not yet continuous).
The Waimakariri River Regional Park, Chaneys Plantation and Bottle Lake Forest
are also noted in the wider locale.
Within Area 18 are a number of local purpose/community reserves. These include:
-
Mana Whenua /
Ngāi Tahu Interests
The Brooklands Domain (28,054m2), in the centre of Area 18A
The Harbour Reserve (2,528m2) at the northern end of Area 18A
Brooklands Playcentre Reserve located just south of the Lower Styx
Road/Dartford Street intersection
The Culturally Significant Area (Te Riu o Te Aika Kawa) is located in the vicinity of
Brooklands Lagoon and part of a wider Ngāi Tūāhuriri takiwā area of interest. It
encompasses large area of Area 18 to the east of Lower Styx Road and is known to
be a site of Māori occupation, of which evidence has been found in the past.
Area 18 is located close to the Styx River which is culturally significant to mana
whenua and Ngāi Tahu and the location of Māori Reserve 892 – Pūharakekenui.
Mana Whenua and Ngāi Tahu strongly recognise the relationship of this area with
Te Ao Tūroa (Natural Environment), ecological values and the water. This area also
has significant Mahinga Kai values.
Archaeology and
Heritage
Chapter 9 (Natural and Cultural Heritage) of the notified version of the Proposed
Christchurch Replacement District Plan: No listed features.
New Zealand Archaeological Association: There are three listed archaeological
within the boundary of Area 18. One of these is in Area 18A and two are in Area
18C. All of the sites relate to Māori occupation.
There are also a number of other recorded archaeological sites in the adjoining
area and there has been significant material evidence of Māori occupation found
in this area in the past. The number of sites reflects the extent of Māori occupation
associated with the resources of the Lagoon and the Māori Reserve 892 –
Pūharakekenui.
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Underground Overground Archaeology 3 advises that the archaeological value of
this area is described as relatively significant. While there was little in the way of
archaeological evidence uncovered during the residential red zone demolitions,
the earthworks were shallow.
Special or Other
Features
Located on the south bank of the Waimakariri River and in close proximity to three
sites of ecological significance.
Hazards
Coastal Hazard
Coastal inundation
Coastal Erosion
Tsunami
SLR = Sea Level Rise
assumed to be 0.4m
over the next 50
years and 1m over
the next 100 years.
All of Area 18 is considered at risk from coastal erosion and inundation, in addition
to being increasingly susceptible to daily tidal influence within the next 50 years.
The existing average ground elevation above perigean high tide level is 0.5m in
Area 18A, and 0.1m in Area 18B. In Area 18C the average ground level is 0.1m
below perigean high tide level in Area 18C.
Area 18C is currently protected by the Waimakariri stopbanks and the tide gates at
the outlet of the Styx River to Brooklands Lagoon.
The Waimakariri stopbanks do not provide protection from future higher sea levels
entering Area 18A from the direction of Brooklands Lagoon.
For more information on coastal hazards, Christchurch City Council have a web
page dedicated to coastal hazards which can be accessed at:
http://www.ccc.govt.nz/environment/land/coast/coastalhazards/
The area has also been mapped as being in a tsunami inundation zone. Further
information on tsunami risk is available at:
http://ecan.govt.nz/advice/emergencies-and-hazard/tsunami/Pages/southamerican-tsunami-modelling.aspx
Flooding
ARI = Average
Recurrence Interval
Area 18 falls within the proposed Christchurch Replacement District Plan Flood
Management Area (200 year flood) and Flood Hazard Management Area (more
than 1m depth in 500 year flood) and the Flood Ponding Management Area (200
year storage volume required for flood control).
Any fill placed on the lower terrace (within 50 – 200m of Styx River) would
diminish the volume in the Flood Ponding Area in the District Plan. Over the
remainder of the area, if it was proposed to raise the land above flood level, an
average fill height of about 1.1m would be required.
The depth of flooding in Area 18 in a 50 year flood event with 1m sea level rise
may range from 0.4 to over 1m.
The depth of flooding across the whole of Area 18 in a 200 year flood event with
1m SLR may range from 0.7 to over 1m.
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Archaeologists engaged by CERA to undertake observation of demolitions.
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For further information on flood hazards refer to the: ‘Flooding’ and ‘District Plan’
pages on the Regenerate Christchurch webpage.
Geotechnical
Earthquake induced
Liquefaction, lateral
spreading
Subsidence
(consolidation)
In Area 18 the main geotechnical constraint is the thin and weak non-liquefying
ground surface crust, resulting in the potential for moderate to severe
liquefaction-induced subsidence. Additionally, in Area 18C there is potential for
major area-wide lateral spreading towards the river.
For further information on geotechnical issues in this area refer to the following
geotechnical summary:
http://ceraarchive.dpmc.govt.nz/documents/flat-land-geotechnical-summaries
Contamination
Only one known HAIL site. This is likely to be a single domestic tank. Age of
dwellings means that soil contamination from asbestos is possible.
Infrastructure
Wastewater
Maintenance of services to Kainga, requires wastewater mains with associated
wells and pumping stations to be maintained within Area 18. These are located
generally within the Lower Styx Road reserve, running north/south through Area
18.
Water supply
Maintenance of services to Kainga, requires water supply mains with associated
wells and pumping stations to be maintained within Area 18. These are located
generally within the Lower Styx Road reserve, running north/south through Area
18.
Stormwater
management
Stormwater mains discharge to The Styx River from Harbour Road, south of
Dartford Street, north of Anfield Street. There are also stormwater mains
discharging to the Brooklands Lagoon at the end of Blue Lagoon Drive and from
Seafield Park subdivision to Seafield Park Wetland.
Transport
The area can be accessed from the south through Lower Styx Road and from the
west from Kainga and Harbour Roads. Under the new Christchurch District Plan,
Lower Styx Road is identified as a Collector Road in the strategic road network,
with Lower Styx Road, Harbour Road and the existing boat ramp providing access
to the Lagoon.
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