Brooklands Residential Red Zone: Summary of Technical Information As at October Area ID: 18A, 2016 18B, 18C

Brooklands residential red zone: Summary of Technical Information as at October Area ID: 18A, 2016 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

Natural Environment and Cultural Setting and Features

Natural Area 18 is adjacent to three Sites of Ecological Significance (SES’s) as identified in Environment 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 – Current median groundwater depth is predominantly at about 1m below the depth below surface 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. 2 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. 2

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: - 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

Mana Whenua / The Culturally Significant Area (Te Riu o Te Aika Kawa) is located in the vicinity of Ngāi Tahu Interests 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 Chapter 9 (Natural and Cultural Heritage) of the notified version of the Proposed Heritage 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.

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 Located on the south bank of the Waimakariri River and in close proximity to three Features sites of ecological significance.

Hazards

Coastal Hazard 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. Coastal inundation The existing average ground elevation above perigean high tide level is 0.5m in Coastal Erosion Area 18A, and 0.1m in Area 18B. In Area 18C the average ground level is 0.1m Tsunami below perigean high tide level in Area 18C. SLR = Sea Level Rise Area 18C is currently protected by the Waimakariri stopbanks and the tide gates at assumed to be 0.4m the outlet of the Styx River to Brooklands Lagoon. over the next 50 The Waimakariri stopbanks do not provide protection from future higher sea levels years and 1m over entering Area 18A from the direction of Brooklands Lagoon. the next 100 years. 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/south- american-tsunami-modelling.aspx

Flooding Area 18 falls within the proposed Christchurch Replacement District Plan Flood Management Area (200 year flood) and Flood Hazard Management Area (more ARI = Average than 1m depth in 500 year flood) and the Flood Ponding Management Area (200 Recurrence Interval 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.

3 Archaeologists engaged by CERA to undertake observation of demolitions. 4

For further information on flood hazards refer to the: ‘Flooding’ and ‘District Plan’ pages on the Regenerate Christchurch webpage.

Geotechnical 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 Earthquake induced liquefaction-induced subsidence. Additionally, in Area 18C there is potential for Liquefaction, lateral major area-wide lateral spreading towards the river. spreading For further information on geotechnical issues in this area refer to the following Subsidence geotechnical summary: (consolidation) 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 Stormwater mains discharge to The Styx River from Harbour Road, south of management 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. The area can be accessed from the south through Lower Styx Road and from the Transport 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.