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contents
Background 4
Introduction 6
Context 6
History 8
Catchment 10
Contaminated Sites 10
Water 10
Landscape Character 11
Plant Communities 12
Plant Pests 14
Birds 15
Fish and Invertebrates 19
Recreation 20
Green Corridor Connections 20
Community Involvement 23
Summary of Community Views 24
The Bexley Wetland Trust 25
Restoration Efforts 25
Schools take Action 26
Funding 26
Bexley Wetland Proposals 27
Introduction 28
Cleaning up Contaminated Sites 28
Stopbank Changes 28
Landscape 28
Plant Communities 33
Restoring Bird Habitat 36
Restoring Fish Habitat 43
Cultural and Heritage Values 44
Recreation 45
Interpretation and Education 46
Partnerships 47
Action Plan 48
Appendices 51
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INTRODUCTION
An enthusiastic group including the Bexley WetlandTrust, staff from the Christchurch City Council, andthe community, is restoring Bexley Wetland. This saltmarsh / salt meadow wetland with some freshwatersprings is located near where the Avon River meets theAvon Heathcote Estuary. This development planhighlights the natural and cultural heritage features ofthe site and identifies management priorities andtimeframes. It is a guide to the integrated developmentof one of the potentially more important wetlandecosystems in Christchurch.
Bexley Wetland Restoration Goal
To protect existing plant communities, and to restorelost or damaged plant communities and wetland birdfeeding, nesting and roosting habitat, while providingpublic access for recreation and education.
CONTEXT
Bexley Wetland is situated between Bexley Road tothe West, the Avon River to the East, Pacific Parksubdivision to the North and the estuary to theSouth.
A significant portion of the local community has forsome time been concerned about, and active in,saving the unique habitats of Bexley Wetland. In1984 a petition signed by 2044 Christchurchresidents was presented to the Christchurch CityCouncil, requesting that certain low-lying areas ofthe then Bexley Employment Zone be retained forwildlife, landscape and flood alleviation purposes.The petition was referred to the Parks andRecreation Committee for consideration. In spite ofthis petition the Council decided to proceed withresidential development.
BAckground
Figure 1: Location of Bexley Wetland
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Figure 2: Zoning map and Ecological Heritage Site location.Bexley Wetland is part of the Ecological Heritage Site.
BAckground
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CATCHMENT
Bexley Wetland’s surface water catchment is primarilyconfined to the boundaries of the wetland. Stormwaterrunoff that would have drained into the wetland fromthe neighbouring subdivision has been redirected awayfrom the wetland. Where possible springs andupwellings have been protected and enhanced,however, some of the original waters feeding thewetland have been reduced as a result of work on theadjacent subdivision.
CONTAMINATED SITES
An area of approximately 2.9 hectares in BexleyWetland was known as Cunninghams Yard and usedfor a scrap metal recovery business. An investigationby Pattle Delamore Partners Ltd (1997), found thatchemical residues from the former scrap metal yard,started over 50 years ago, have affected surface soils,sub-surface soils, surface water and groundwatershowing elevated concentrations of dissolved metalsover much of the site. Elevated levels of a variety ofmetals and organic compounds, which exceedguidelines for aquatic ecosystems, are found in the soilover much of the area identified for restored saltmarshand meadow. With river controls and minimaldisturbance, the contamination does not present anysignificant threat to the greater estuarine area.
WATER
Bexley Wetland has predominantly brackish water (amix of saline and freshwater) with both freshwater andsaltwater inputs. Freshwater comes from rain, runoff,and groundwater, and there are freshwater springsproviding water from deeper aquifers. Seasonalgroundwater levels are often higher than existingground levels. No monitoring has been carried out todate to determine whether groundwater levels resultfrom tide levels. Much of the site would be inundatedby daily tides without existing stopbanks and tide-gated stormwater outfall pipelines through thestopbanks. Notwithstanding the tidal protection, thesite is subjected to periodic flooding from extreme tidesand leaking tide-gates. There is one well-definedspring to the north-east of the wetland that hasallowed a freshwater habitat to develop. This area hasbeen isolated from the more brackish waters elsewhere.Other freshwater upwellings over the site are hard toaccurately identify as seepage zones are often in poolsof water or vegetated areas.
The site of Bexley wetland was used as a scrap metal yard, whichhas left the soils contaminated.
Credit: K
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LANDSCAPE CHARACTER
Bexley Wetland has expansive, open views to thesouth with a backdrop of the Port Hills, and to thenorth and west, the distant Southern Alps (Figure 3).Conifer plantations are strong features across the AvonRiver. The wetland is presently divorced from the riverdue to the presence of the stopbank.
At a finer level the area is reminiscent of coastalfarmland and wasteland. It has a modified, disturbedappearance. The cyclical and seasonal changes inBexley Wetland are not strongly reflected. BexleyWetland’s natural values are only obvious to thetrained eye. The subdivision being developed on thenorthern boundary of Bexley Wetland will result insharp profiles and hard lines of the buildings andfences. New native plantings along the embankmentor buffer strip are softening the impact of thesedevelopments.
LANDSCAPE CHARACTER
Figure 3: Expansive, open character.
Credit: K
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The report identifies the following important plantcommunities:• Several areas of native salt meadow (an association of low-growing species such as glasswort, salt grass, sea spurrey, Samolus and Selliera). This is a rare community type in the estuary because in the past these areas have often been reclaimed or treated as wastelands.• Marsh ribbonwood with various salt marsh species. This is one of the largest extensive stands of this vegetation type and backs onto the rush-reed saltmarsh.• Freshwater wetland with raupo, lake clubrush, duckweed and floating fern (Azolla). These wetlands are the result of springs, which displace the saltwater, allowing freshwater species to become established.• Mixed salt and freshwater plant associations.
The extensive stands of sea rush and jointed wire rushthat dominate most of the saltmarsh outside thestopbank are poorly represented in Bexley Wetlanditself, but are likely to become a significant vegetationtype to be restored once appropriate salinity patternsoccur.
The present vegetation indicates changes due todesalinisation and associated farming activities. Thegeneral lowering of salinity has resulted from therestricting of saltwater inflows following theconstruction of the stopbank. The resultant changehas seen an influx of freshwater species and pastureplants. The remnant saltmarsh plants have lost contactwith their appropriate tidal salinity patterns and persistunless displaced by other vegetation.
PLANT COMMUNITIES
The Black Maps were compiled in 1856 and showvegetation types throughout Christchurch city. In thearea of Bexley Wetland a swamp of flax, toetoe, grassand rushes abounded, with tidal creeks and channelsclose to the Avon River (Figure 4).
Since then, the margins of the Avon HeathcoteEstuary have been encroached upon by urban andagricultural development through reclamation, to sucha degree, that for much of its perimeter the margins arenow tidal mud alone. The natural sequence of tidalflats, short salt marsh meadow, maritime rushes andreeds, marsh ribbonwood-New Zealand flax shrubland,coastal bush and freshwater wetland has beentruncated. This truncation has been especiallydamaging to the landward margin of the sequence.Although highly fragmented and damaged, remnantparts of this sequence are still present at BexleyWetland, and it is still possible to repair and restorethem.
The Bexley Wetland forms part of a continuum of saltmarsh vegetation extending from the South BrightonJetty, up both sides of the Avon River to AdmiralsWay (McCombs & Partridge 1992). This constitutesthe largest continuous area of salt marsh vegetation inthe estuary.
Selliera radicans
Glasswort
Floating fern
Credit: K
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PLANT COMMUNITIES
Credit: K
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Credit: K
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Figure 4: Bexley Wetland & surrounding areas, Black Maps 1856.
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The major freshwater threat is from willows, especiallygrey willow, which is present in the Bexley Wetland.This is the only willow in New Zealand that canreproduce by seed, and the numbers of these are vastand many seedlings have been seen.
Most of the current plant pest problems occur at thesaltmarsh to non-marsh boundary and comprise typicalgarden, wasteland and pasture weeds that are anuisance to the restoration plantings.
The plant pests establishing in the filled area alongBexley Road, and on the open areas of the housingsubdivision, are a source of weed seed for the nearbywetland.Bucks horn plantain
Sickle grass
Tall fescue
PLANT pests
PLANT PESTS
Several plant species compete with native plants andrequire management. Bexley Wetland has a number ofexotic and rank grasses due to past grazing,desalination, and use of the site as a wasteland.
Credit - K
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Credit - K
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The main plant pests of the wetland are the grasses tallfescue and creeping bent. These are unfortunatelyfairly salt tolerant (Partridge and Wilson 1987). Otherweeds of salt meadow include buck’s horn plantain,which is so widespread that it is taken for granted andnot possible to be acted upon, and the annual grassessalt barley grass and sickle grass, which althoughdistracting from the appearance of the vegetation, playno detrimental ecological role.
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BIRDS
The Estuary
Crossland (1993) has extensively researched thebirdlife of the area. He writes.....
“The past 150 years have seen dramatic changes in theAvon Heathcote Estuary and Christchurch wetlandbird populations. Prior to European settlement, theestuary mudflats supported large numbers of typicalestuarine species (cormorants, shags, waders, terns andgulls). The beaches and rocky coastline would havesupported nesting populations of many coastal andmarine birds. Extensive freshwater wetlands wouldhave abounded with waterfowl and swampbirds.
European settlement caused a rapid decline offreshwater wetland birds through swamp drainage,introduced predators and shooting. Shooting was alsothe demise of mudflat birds. While pollution beganentering the estuary from the 1860s, its impact waslocalised. Widespread degradation of breeding groundsdid not occur until the 1920s when silt depositionfrom river sweeping smothered shellfish and eelgrassbeds. The period of rapid siltation ended in the 1940s,and this, combined with new laws prohibiting theshooting of many wetland birds, led to a significantrecovery in numbers from the late 1940s onwards.
The completion of the Bromley Oxidation Ponds in1962 created valuable waterfowl habitat that wasquickly colonised. Changes to the outfall system fromthe ponds in the 1970s led to significant improvementsin environmental conditions, and a subsequentincrease in bird numbers.
From a bird population peak in 1989/90 the numbersof many species on the estuary began to decline forunknown reasons.
Although high numbers of birds are often observed inthe Avon Heathcote Estuary complex, residentbreeding populations are very small. Nesting success isvery low, with failure rates for many species typicallyexceeding 90%.
The future of the Avon-Heathcote Estuary’s birdlifedepends a great deal on the health of the ecosystemand the future variety, size and quality of the habitatsavailable. Bexley Wetland is one area that hasexcellent potential to increase habitat quality andquantity in the estuary vicinity. This is particularlyimportant for the future viability of certain Avon-Heathcote Estuary resident breeding populations suchas pied stilt, banded dotterel, grey duck and NewZealand shoveler. Rare species, which do not presentlynest here, namely bittern and marsh crake, could onlyoccur in a continuous tract of high quality wetlandhabitat incorporating Bexley and the lower Avon salt/river marshes.”
BIRDS
Cormorant
White-faced heron
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Birds at Bexley Wetland
“....to a large degree the future of the estuary’sresident breeding population lies in thedevelopment of this (Bexley) area as a reserve.”
Andrew Crossland, 1993.
“Bexley Wetland supports the most diversebreeding community of any site in the AvonHeathcote complex outside of the human-made(and very artificial) Bromley Oxidation Ponds.”
Andrew Crossland, 1995.
Birds nesting at Bexley Wetland(Figure 5)
Banded dotterel
Grey duck
Mallard
New Zealand scaup
New Zealand shoveler
Paradise shelduck
Pied stilt
Pukeko
Spur-winged plover
Welcome swallow
Birds feeding and roostingat Bexley Wetland
(Figure 6)
White heron
White-faced heron
Marsh crake
New Zealand kingfisher
Grey teal
Harrier
Gulls
A range of native and introduced passerines
birdscontinued
New Zealand kingfisher
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Figure 5: A few of the bird species that nest at Bexley Wetland.
paradise shelduck (male)(putangitangi)
welcome swallow
paradise shelduck (female)(putangitangi)
NZ scaup (papango)
NZ shoveler (hono)
pukeko
grey duck, (parera)
BIRDS
18Figure 6: A few of the bird species that roost and feed at Bexley Wetland.
grey teal (tete)
NZ kingfisher (kotare)
white-faced heron
BIRDS
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Fish and Invertebrates
The National Institute of Water and AtmosphericResearch (NIWA) maintain a Freshwater FisheriesDatabase. A search on the Avon River near BexleyWetland revealed a surprising diversity of freshwaterand marine fish species (Mark Taylor, NIWA). Thesespecies include yelloweye mullet, shortfin eel, inanga(whitebait), common bully, giant bully, cockabully(marine), salmon, common smelt, yellowbellyflounder, sand flounder, and brown trout.
The mouth of the Avon River near Bexley Wetlandwas known for the abundant supply of tuna (eel),inanga (whitebait), and kokopu (native trout) to befound there. The abundant fish and bird populationsprovided an excellent source of mahinga kai for localMaori.
Mud crab
Polychaete rag worm
Ten crab species can be found in the Avon HeathcoteEstuary - you can spot the tunnelling mud crab’sburrows in the mouth of the Avon River. The mudflatsnail, several species of polycheate worms, andshellfish populate the area around the Avon Rivermouth. Refer to The Estuary (Owen 1992) for moreinformation on the ecology of the estuary.
Fish & Invertebrates
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Green Corridor Connections
Bexley Wetland is part of a green corridor stretchingfrom the Avon-Heathcote Estuary, up the Avon River,through the Woolston Burwood Expressway wetlandsto Travis Wetland, into Burwood Forest and up toBrooklands Lagoon (Figure 7). It is also an importantlink in a chain of coastal Canterbury wetlands that lieunder an international bird flyway.
The establishment and maintenance of connectionsthrough the coastal green corridor aim to fosterecological, recreational, cultural and heritage linksthrough the wetlands and open spaces of easternChristchurch.
recreation
green corridor connections
RECREATION
Joggers, walkers and dog owners use the existingwalkways. Local people have a very keen interest inthe area and have been involved in planting andmaintenance activities at the wetland.
Credit: K
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Figure 7: Estuary to Lagoon Green Corridor
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Summary of Community Views
A community meeting was held on February 2, 2000to introduce the development plan and to seekcommunity feedback. The following comments werereceived at the meeting.
Maintenance and Management• Regular maintenance - whose responsibility?• Predator control - rabbits and rats• Horse grazing in adjacent paddocks - will weeds spread if grazing pressure is reduced?• Mulch new plantings well to keep the weeds down.• Informal surveillance from adjacent houses to create a safer human environment, eg., by lowering fences
Human Values• Retain the site as an area for bird watching and walking• Ecological and recreational linkages• Loop walk is a good option• Proactive community education programme• Provide viewing areas and hides with interpretative panels
• Include more public education - signs and maps• Involvement of schools• Involve children with planting• Contemplation area• Foster new themes for the area - eg., ‘a peaceful place’, ‘being surrounded by nature’.• Picnicking area• Ecotourism opportunities• Should developments be fenced off?• Planting height may block views for children
Planting at Bexley Wetland
community involvement
Water Management• Flooding if stopbanks are lowered or during very high tides or wet weather• Flexible management of water levels needed to avoid midge problems• Avoid stormwater and sediment in the reserve.• Water quality - pollution issues• Stagnant pool in previous backwater• Stopbank removal. Erosion control? Is it necessary to remove the stopbank? Contamination spread by tide? Can some stopbank be kept as a walking track?• Could use weirs to control freshwater and salt water mixes
• Provision of more freshwater areas.• Preservation of the springs
Wildlife• Focus on bird habitat creation• Larger trees on filled area would be good for roosting cormorants. These will eventually be killed by the birds and will require replacement in time.
• Enhance connections between the river and wetland, eg. fish passage and water movement• Can there be more research into marine life?Human Impacts• Motor cyclists through walkway• Graffiti on bridges• Removal of contaminants
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Earthworks and Community Planting
A moat of deeper water, generally 1.2 to 1.5 metresdeep, is being excavated along the wetland’s northernboundary as a buffer zone to protect birds from predators.
Construction of the moat is a “partnership”arrangement with the Pacific Park developer. Civilworks to dig the moat and form the northern bank areaare being carried out by the developer in exchange forsoil. The Council has committed to plant out theprepared buffer strip.
Pre-excavation work included lifting the top soil layer,which still retains significant communities ofsaltmeadow. This layer was replanted onto the newlyformed banks of the finished moat.
With the assistance of Coast Care (Parks Unit, CCC),the Trust has organised community planting days, withover 6000 trees, shrubs, grasses and rushes plantedalong the moat to reinforce the buffer zone. Boundedby the Avon River in the east and south, and the moatin the northand west, and buffer planting, the Trust expects this12.5 hectare habitat to have a degree of protectionfrom domestic pets.
Trees for Canterbury has donated trees and shrubs andhas future plans to propagate some of the specificshrubs and plants needed for the restoration projectfrom the appropriate sources. In February 2000, Treesfor Canterbury and their staff, together with CoastCare and Bexley Wetland supporters, planted over 900rushes propagated and donated by Trees forCanterbury.
The Bexley Wetland Trust also works together withthe Travis Wetland Trust, with members frequently incontact with each other and supporting communitydays at both sites. A walk was organised by members ofboth Trusts in October 1999 from Travis Wetland toBexley Wetland, in which 35 people participated.
THE BEXLEY WETLAND TRUST
In the beginning of 1999, seven concerned peopleincorporated a charitable Trust, with the aim of notonly protecting, but of restoring, the unique habitats ofBexley Wetland. The Trust aims to integrate the widerange of wetland habitats, plant communities and soilswith the Pacific Park housing development throughinvolvement in restoration work. The Trust also aimsto foster community awareness and involvement in therestoration of Bexley Wetland.
restorationefforts
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Hap Hill, Bexley Wetland Trust
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School children regularly plant at Bexley Wetland
FUNDING
The Bexley Wetland Trust has been successful inapplications for funding for ecosystemenhancement and restoration and for informationpanels. Funding has been received from theLotteries Grant, the Pub Charities Grant and theCommunity Trust.
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Schoolstake Action
As well as the restoration of the wetlands, the Trustaims to foster community and school involvement forthis project. St James School is the first school thathas taken up the challenge. They have made thistheir Community Project for the new millennium bygrowing native trees for the wetlands from youngseedlings propagated by the Native Seed Bank inRiccarton Bush, with potting mix provided by theBush Society. Next year they plan to plant theseyoung trees out in Bexley Wetland, to assist theTrust with the restoration of this habitat.
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STOPBANK CHANGES
Parts of the stopbank are to be removed to restorenatural tidal influxes into the wetland. It is anticipatedthat the remaining stopbank will be part of a chain ofislands with tidal waters flowing between. The inletstructures will be created from low, reinforced bunds atdefined levels to enable tidal inflows. Appropriateland-based vegetation will be restored on to theseislands.
INTRODUCTION
A landscape plan has been prepared for BexleyWetland. The proposals are explained in detail in thissection.
Bexley wetland proposals
It has been agreed that because of the proposedchanges in water regimes (the more regulated tidalinflow) that remediation of the contaminated sitemust occur before wetland development begins.Monitoring of the site after remediation will also benecessary to check that the area remains suitable forthe restoration of aquatic communities.
The Christchurch City Council has considered thefollowing options:• Do nothing• Remove all contaminated material to an approved landfill• Remove all contaminated material from the proposed wetland restoration areas and “secure” it elsewhere on the site.• Onsite treatment of material
The proposal currently favoured is to excavate allcontaminated soils from the wetland restoration zoneand place it elsewhere on site on a prepared base ofhighly impermeable silts at an elevation abovegroundwater levels and beyond existing and expectedfuture seasonal tide levels. The material will be cappedwith clean imported soils to minimise rainwaterpercolation down through the contained soils.Landscaping would enhance the created mound,which would be left as another valuable addition tothe overall restored site.
LANDSCAPE
The proposed developments will restore the wetland’snatural ecosystems and processes, improving theexisting wetland values and making these more visible.
Removal of the stop bank will allow more water intothe wetland and provide experiences of tidal changesand reflections on water. The connection between theriver and wetland will be reinforced.
As new plantings mature they will provide screeningof nearby residences, giving the wetland morewilderness character. The increase in birdlife will addto the impression of a “wild place”.
Cleaning upContaminated Sites
Figure 8: Landscape Development Plan
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Ngaio - coastal bush
Plant Communities
Creating a Mosaic of Vegetation Types
The aim is to create appropriate conditions at BexleyWetland to encourage stress-tolerating plant species.The main stresses will be salt and water - we areencouraging salt marsh and freshwater species in theappropriate ecosystem contexts.
To do this we must:• create a good elevation sequence with depths from low to high tide• ensure water composition changes along gradients from salt to fresh• create zonation patterns that allow for a variety of communities, and• provide the right environmental conditions through appropriate tidal flushing.
Protection of Existing Vegetation
A freshwater wetland fed by a spring lies at the northeast end of Bexley Wetland. This area is dominated bya healthy stand of raupo with the native floating fern(Azolla filiculoides) in areas of open water. Thesespecies will not tolerate salinity and require protectionfrom tidal influxes. The area is now isolated from tidalwater flows and only fed by a freshwater spring.
Much of the wetland still has remnant nativevegetation mixed in with weeds of pasture and wasteareas. These native species are out of their naturalsaline context and are simply persisting there. Theywill however be placed back into their appropriateenvironment once tidal saltwater flows are re-established. Tidal flows will provide the opportunityfor the native saltmarsh plants to re-establishthemselves either through seed or vegetative spread. Itis important that as much as possible of this vegetationis left to repair the saltmarsh once tidal waters arereturned. It will be necessary for some to be sacrificed,but careful planning should ensure that such damage iskept to a minimum.
Coastal Bush
The coastal bush plantings will include species such asake ake, broadleaf, ngaio, Olearia, Pittosporum, totaraand kowhai. These will occur on areas well removedfrom saline influence, such as on the paddock byBexley Road.
Brackish Sandpiper Pools, Inlets and Mudflats
Sandpiper pools, inlets and mudflats will be dominatedby small sedges, rushes and salt grass. Some areas willbe left bare to allow for bird roosting. It is anticipatedthat these areas will become significant feeding andnesting habitat for wetland birds. To ensure optimumhabitat for aquatic insects and other prey fauna,salinity levels will be regulated to a limited extent byonly allowing shorter duration, higher levels of tidalflows from the estuary into the site. This will beachieved by setting “weir” levels in the proposedstopbank openings. At least one freshwater zone to thenortheast, currently sustained by a spring, will remainseparated from the more regular tidal flows proposedelsewhere.
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Bexley wetland proposals
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Freshwater Wetlands
Raupo grows near the primary freshwater spring(Te puna o te puhi ariki - the spring of the chieflywoman). Areas of freshwater will be protected wherepossible from saline intrusion to allow freshwaterwetland communities to establish. The sites will bemonitored and changes made to the control inletstructures to manage salinity in the wetland. Issuesregarding the management of these freshwater basinsystems will need to be addressed, especially in regardto infilling.
The freshwater springs at Bexley are perceived assignificant habitat for eels by Waitaha. Tidalinundation of these freshwater habitats will berestricted and salinity levels controlled to enable thewetland to sustain populations of both long and shortfin eels.
Cabbage Tree / Manuka / Tall Shrub Wetland
This association includes sedges, Coprosmas, cabbagetrees, toe toe, kanuka, manuka and flax on appropriatesoil and moisture gradients. This vegetation is mostappropriate for areas above tidal flooding wheresalinity is lowest.
Flax Swamp, Freshwater Pools and Seepages
Carex species, raupo and flax will dominate freshwaterwetland associations, with reeds and rushes whereappropriate. The vegetation will vary according towater table and salinity levels.
Salt Meadow
It is proposed to encourage intermittent tidal flowsinto salt meadow to allow salt-tolerant meadow plantsto naturally replace invasive weeds and grasses. Activeplanting is not proposed for these areas. These speciesare typically able to establish themselves, and there is agood pool of seed both within the Bexley Wetland andfrom the estuary. These areas will become importantnesting and roosting habitat for wetland birds.
Saltmarsh Ribbonwood Wetland
Ribbonwood, jointed wire rush, sea rush and othersaline tolerant species dominate the area betweenBexley Wetland and the Avon River. It is proposed toincrease the proportion of these associations in BexleyWetland as brackish ecosystems are nowunderrepresented in Christchurch. This will be bestachieved by ensuring that remnant stands of thesespecies are allowed to spread, with enhancementplantings to speed the process.
Saltmarsh ribbonwood
Credit: K
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Raupo (Typha orientalis)
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Jointed wire rush
Bexley wetland proposals
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Grading from Saltmarsh to Freshwater Vegetation
The Bexley Wetland provides the opportunity forenhancing the saltwater system by the creation offreshwater ecosystems and brackish water mixes.These opportunities arise because of the presence offreshwater springs. At the Wairoa Street end of theBexley Wetland, a small and separate spring-fedfreshwater wetland has been created at a level abovethe surrounding estuary, and has an outlet to theestuarine restoration area. This wetland comprises apond and short vegetation with a stand of raupo.A freshwater spring atthe Bexley Road end ofthe moat, provides theopportunity for therestoration to includea gradation fromsaltmarsh to truefreshwater vegetation.These gradations arenot well represented inCanterbury (SaltwaterCreek is the best), sosuch vegetation will beof special value.
Plant Pest Management
Passive control of plant pests through water level andsalinity control is the most appropriate managementfor many exotic and rank grasses. However, restorationof salinity will only repair the situation in the mostsaline lower saltmarsh zones. Tall fescue in particular isan annoyance, and will only be displaced by a densestand of jointed wire rush and coastal ribbonwood inthe upper saltmarsh zones. Creeping bent will be aplant of salt meadow and turf, but if thosecommunities are returned to an appropriate salinityregime, its impact should be minimised.
The plant pests at the saltmarsh to non-marshboundary interfere with initial growth and survival ofrestoration plantings. Eventually, the establishment ofdense vegetation of shrubs and trees will cause these todisappear through light competition. Spraying,mulching and weeding of non-saline areas will benecessary at this establishment phase.
Willow trees and seedlings will need to be removed assoon as possible, to avoid larger problems in the future.Enhanced salinity levels should help at keeping thisplant at bay.
Grazing Pests
Rabbit control may also become an issue, althoughwater levels will hopefully deter grazing.
Credit: K
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Avon River plantings
Avon River Bank Plantings
Restoration plantings of both estuarine and landplants have occurred along the banks of the AvonRiver, outside the Bexley Wetland itself. In somesituations these can be enhanced through the plantingof maritime rush on the tidal margins, grading intojointed wire rush and ribbonwood. Enhancements tothe coastal bush associations are proposed for anyhigher, drier land.
Tall fescue
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Raupo
Bexley wetland proposals
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Restoring Bird Habitat
Increasing Bird Habitat
One of the main objectives for restoring BexleyWetland is to increase bird habitat. The birds that arelikely to increase in numbers include water fowl,waders, white faced and white herons, grey teal, NewZealand shoveler, native grey duck and kingfishers.Bellbirds may also use the area when flax bushes andtrees of kowhai around the margins are established andproviding nectar.
We need to create a range of habitats with thefollowing features:• A series of islands divided by waterways throughout the site to increase the feeding margin for birds, and surrounded by a moat to protect against predation. These islands also provide nesting sites with reduced predation pressure from cats and ferrets.• Shallow muddy margins for wader feeding (inanga and invertebrates) along the waterways between islands.• Ample bird feeding and breeding opportunities• Plenty of high tide roosting sites• Areas of tall freshwater wetland plants to promote nesting habitat for waterfowl, pukeko, marsh crake and bittern. Plants can be used for screening the road, while still allowing visual access from the road into the wetland.• Tidal influx enabling the saline influence to maintain the dominance of salt tolerant plants and restrict invasive weeds.• A range of water salinity levels.• Tree stump roosting sites for birds to add habitat variety.• Dogs prohibited in feeding, roosting and nesting areas, and required on a leash in all other areas.
Bexley wetland proposals
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Dog control is critical to protect bird habitat
Figure 10: Moat cross-section.
Bexley wetland proposals
Predators
Predator control and avoidance of disturbance iscritical to protect bird habitat. A deep moat aroundpart of the wetland, surrounding islands divided bywaterways, will deter cats, dogs and ferrets fromaccessing at least some of the wetland (Figure 10).Stoats and rats can swim but can be controlled whennecessary by poison bait laid on the islands or by traps.This design should eventually provide relatively safebreeding habitat for a wide range of wetland birdspecies, and provide feeding and roosting habitat formany more. The removal of part of the stopbank willalso assist to keep dog access to the outside of themoat.
Signs have been erected by the Bexley Wetland Trustto educate dog owners and to encourage them to keeptheir dogs on a lead. While signs may be a positivereinforcement of appropriate behaviour they cannot beexpected to change behaviour. This is more likely tooccur with direct contact between dog walkers, councilstaff and Trust members.
Developing a community sense of ownership throughcommunity activities (leaflet drops, BBQ, work parties,community recreational events) will have an impacton site management. Activities that coincide withregular times of the day for walkers, joggers and dogwalkers will have more impact. The Bexley WetlandTrust will continue to fill the role of watchdogs for thearea.
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Potential Wildlife Target
Andrew Crossland (1995) identified key targets forbird numbers and breeding success at Bexley Wetland.
Pied stilt
Pied stilt - 30 pairs nesting annually, with 50 chicks fledged (= about 50% success)
Banded dotterel5 pairs nesting annually, with 5chicks fledged (= about 40% success)
Grey duck10 pairs nesting annually
New Zealand shoveler10 pairs nesting annually
Pukeko 25 nests (they breed in groups, notpairs) annually
Other wetland species expected to nest should includeblack swan, paradise shelduck, mallard, grey teal,harrier, spur-winged plover, southern black-backedgull, New Zealand kingfisher and welcome swallow.
Other species occurring to feed or roost include blackcormorant, pied cormorant, little cormorant, littleblack cormorant, white-faced heron, white heron,royal spoonbill, Canada goose, marsh crake, SouthIsland pied oystercatcher
By 2005Bittern 1+ pair nesting; 2-4+ present during the
non-breeding season
Marsh crake2+ pairs nesting; 4-8+ present duringthe non-breeding season
Regular occurrence of New Zealand waders onmigration or dispersal (eg., wrybill, black-fronteddotterel, New Zealand dotterel, black stilt, amongstothers)
Irregular occurrence of arctic migrants (eg. Godwitspecies, curlew species, plover species, sandpiperspecies and tern species amongst others).
Irregular occurrence of Australian vagrants (eg. egretspecies, ibis species, tern species, amongst others)
Possible successful reintroduction of South Islandfernbird (locally extinct since about 1898 but stillcommon on the West Coast and in Southland).
By 2010
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Wildlife Linkages
Andrew Crossland reports that Bexley and the lowerAvon marshes form the largest continuum of naturalvegetation remaining in the Avon Heathcote complex.As many wetland birds use both areas, it is importantthat they be managed as a whole.
Birds rely on a chain of local wetlands rather than justone site. Locally, birds will travel between BexleyWetland and the estuary, the Bromley OxidationPonds, nearby paddocks and Travis Wetland.
Bexley Wetland is situated very close to theconvergence of major flyways used by migratingwetland birds and is a stopping off point for many ofthese species. Once high quality habitat has beenrestored at Bexley it is expected that many of thesemigrating birds will make this site their first port ofcall when arriving in the Avon Heathcote Estuary.
Heathcote River
Hills
Styx River
Waimakariri River
Flyway aroundGodley Headand BanksPeninsula
McLeans Island
Avon Heathcote Estuary toLake Ellesmere Flyway
Figure 11: Bird flyways in and around Christchurch
Bexley wetland proposals
43
Eel
Restoring Fish Habitat
After a search of the Freshwater Fisheries Database,Mark Taylor of NIWA has suggested that the followingspecies may colonise the wetland from the Avon Riverif the proposed breach in the stopbank lets sufficientwater enter the system:
• Mullet may school into the wetland on the high tide if the water is deep enough.
• Shortfin eel will certainly colonise wetlands, and coastal wetlands are important rearing grounds for this species, as long as they are not over-fished.
• Inanga may also use the wetland.
• The common bully and giant bully may enter the wetland provided there is some refuge such as plants and rocks in the water as shelter.
If the water quality and habitat is good there ispotential for quite a diverse fauna in the wetland.
Monitoring fish populations over time will provide uswith good information for the restoration of othercoastal wetlands.
Common bully
Yellow-eyed mullet
Inanga
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Interpretation and onsite activities can highlightcultural and heritage values. Several extensive reportsby Optimax Research identify tangata whenua themesfor the eastern coastal Green Corridor. Some of thesethemes are listed below:• Maori cultural values include the restoration of the life force to signify the spirit as one in the collective and as one in partnership• An eastern gateway to the city - Easter Island and Tahiti links• Trade links along the coast and inland• Guardianship and resource utilisation• Sustainable mahinga kai harvest practices, reseeding and management (eel traps of manuka stakes, deep sea fishing, estuary gathering, flax harvest)• Interconnectedness of ecosystems• Importance of water quality and appropriate use of water• Recognition of nearby park sites and naming of landmarks• Use of dry earth ovens for cooking• Oral communication highlighting the importance of sites• Transmission of knowledge/whakapapa (geneology)• Importance of indigenous species and replanting• Flax planting, reseeding of fisheries nurseries, water quality improvement
Cu
ltu
re &
her
ita
ge
Credit: Cathel-Black Collection
Bexley wetland proposalsCultural and Heritage Values
45
Recreation
A contemplation site will be developed near thefreshwater wetland adjacent to the Avon River,overlooking the wetlands and river. A platform andseating with a brief message to contemplate will becreated.
The change to the stopbank will curtail an existingwalkway through the middle of the wetland, with anew walkway being established around the wetlandperimeter. Waist high planting aims to reduce thedisturbance impact of “moving legs” on birds.
A cycleway/walkway with a cycle/walk bridge over theAvon River has been proposed. There are opportunitiesto link the Avon Heathcote Estuary and BexleyReserve through the coastal green corridor, extendingnorth along the Avon River to Cockayne Reserve,Travis Swamp, Bottle Lake Forest and up to BrooklandsLagoon. This same link could be extended into andaround the City.
Eco-tourism including bird watching and communityplanting could be developed for Bexley Wetland andadjacent ecosystems in the future.
White-faced heron
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Bexley wetland proposals
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Interpretation andEducation
Visitors
Education, information and on-site interpretation isaimed at four different user groups that may visit thewetland:
1) Local community, particularly regular walkers, joggers and dog owners. Interpretation aims to develop a sense of ownership of the site and encourage appropriate behaviour (eg., keep dogs on leads, quiet around bird flocks)
2) School groups. Interpretation aims to give an introduction to site features and restoration and conservation values.
3) Casual visitors who are making a one-off visit to the site. Interpretation aims to provide recreation and conservation information and highlight key features of the site.
4) Special interest natural history groups and individuals will visit the site as habitats develop and more species make the wetland home. Interpretation will provide recreation information and some detail about the restoration of the wetland. More detailed interpretation developed later in the project may appeal to this group.
Interpretation and Education Possibilities
The interpretation and education possibilities atBexley Wetland are boundless. Some possibilitiesinclude:• Onsite maps showing walking tracks linking the Avon River and nearby reserves.• Interpretation panels with information about the wetland, the wildlife, and cultural and heritage features.• An A3 leaflet with a map, general information on birds, history, culture, restoration, etc.• Booklets, books and other publications about the wetland.• Ranger, teacher or volunteer led field trips looking at birds, insects, plant life, ecosystems, food chains, use of plants, etc.• Environmental education activities.• Information on the wetland in nearby information centres.• Festivals such as “Welcome the Birds Back” or themes around tidal processes or fishlife.• Planting and weeding days.• Flax weaving demonstrations.• Bird viewing hides on remnants of stopbank.• Website information.
There is scope to involve a wide range of people inthe restoration and appreciation of Bexley Wetland.
Kids taking action
Planting
Credit: M
ia Colberts
Credit: M
ia Colberts
Bexley wetland proposals
47
Signage
Interpretation signage must be managed sensitively.The site is quite small, so signs and interpretive panelsshould be kept to a minimum and designed to be bothsympathetic to the environment and support thethemes being interpreted.
Vandalism can be an issue in remote sites. Signs mustbe robust and easily replaced.
Other Sites
Interpretation at other estuary and wetland sites needsto be considered to avoid presenting the sameinformation at every site. The aim is to develop acomplementary interpretation framework for thecoastal green corridor. Information centres at TravisWetland and Bottle Lake Forest, and eventually nearthe estuary, will provide detailed interpretation of thearea’s natural and cultural heritage.
Refer to Appendix Two for details on the proposedcontent and location of interpretation at BexleyWetland.
Partnerships
The Bexley Wetland Trust are involved withorganising protection, planting, maintenance, andeducation in and about the wetland. Trustees includespecialists such as Trevor Partridge, a botanist fromLandcare. The Christchurch City Council and theirconsultants assist the Trust by providing plants,planting and maintenance, assistance and advice.Trees for Canterbury, The Bush Society, Friends of theAvon-Heathcote Estuary, The Estuary Association,Riccarton Bush Trust, tangata whenua, schools, localbusinesses and others are all current or potentialpartners in the restoration of Bexley Wetland.
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Action planThe following activities will commence in the Year 2000-2001.
Action Responsibility Year $
Ed
uc
at
ion
Interpretation Plan
Sign Preparation - one
Sign Construction - one
Build 3 bird hides
Design and producean A3 pamphlet onBexley Wetland
Involve schools in restoration
Road frontage plantingat Bexley Rd
Break in stopbanks• Earthworks• Restoration• Monitoring impacts
Freshwater pond bankplanting on east bank- Plant and mulch
Wairoa St entranceplanting and fencing
Track Planting• 2 stages• screening• amenity
Freshwater Wetland• Raupo removal• Digging out sediment
Landscaping nearBexley Rd
Plant horse paddock withcoastal scrub
Freshwater/saline wet islandplanting (only flax on islands)
Maintenance of planting
Weed control• female willow• boxthorns
Predator control- rabbits, hares
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Bexley Wetland Trustand CommunitySt James School
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Parks Unit
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Parks Maintenance
Parks Unit & Bexley Wetland Trust
Parks Unit & Bexley Wetland Trust
Year 1
Year 1
Year 1
Years 3 - 5
Year 1-2
Years 1 - 5
Year 1Pre-August
Years 1-2
Now - Year 0Year 1
Year 0
Years 4- 7
Ongoing
Year 1 - 5
Years 1-5
Years 2-5
Ongoing
Ongoing
Ongoing
$3000 (Parks Lotteries Grant)
$1500
$2400
$12,000 Sponsorship
$6000
$1,000
$5000
$ Coming
$3600
$10,000
$12,000
$3,000
$5,000
$5,000
$3,000
$10,000
$3000Volunteers
$3,000
Rest
or
ing
Pla
nt
Co
mm
un
itie
s
int
er
pr
etat
ion
Bexley wetland proposals
49
Create islands for bird roosting.
Complete swales.
To be completed at time ofcontamination removal.
Pest control(cats, rats, weasels, stoats)
• Trapping and monitoring• Trapping
Scraping of islands to clearoff vegetation for bird roosting
Building and installation ofnest boxes
Install posts for bird roosting
Monitoring bird speciesand numbers
Marine life research andestablish monitoringprogramme
Monitor fishlife / instream changes
Remove contamination andsecure elsewhere on site(including landscaping)
Monitor water quality
Wairoa St Reserve Carpark
Path completion around swale
Create path by motorwaybetween bridge and trackhitting Bexley Rd
Stoppage of Wairoa andAnthony Rds
Survey and change varioustitles to Local PurposesReserve - WetlandConservation
Parks Unit
Parks Unit
Parks Unit
Scott Butcher - volunteer(Bexley Wetland Trust)
Bexley Wetland Trust
Bexley Wetland Trust
Parks Unit and NIWA
Parks Unit,Bexley Wetland Trust, NIWA
Parks Unit & BexleyWetland Trust
Parks Unit
Parks Unit
Roads
Parks Unit and City Streets
Parks Unit -City Streets to do work
Parks Unit
Year 1
Year 1Ongoing
Years 1-10
Year 0
Year 1
Ongoing
Year 3?
Ongoing
Year 1
Year 1-3
Year 2
Year 1
Years 5-10
Year 1
Year 0 - 1
$ ?
$4,000$2,000
$2,000
$ 0
$ 0
$2,000
$6,000
$3,000
$100,000 - $170,000 ?
$6,000
$15,000
$ ?
$ ?
$1,000Free
$10,000
Action Responsibility Year $
BIR
D H
AB
ITAT
CR
EAT
ION
Stu
die
s
contamination
Roads and Path Work
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References
Crossland, A.C. 1993. Birdlife of the Avon-HeathcoteEstuary, Rivers and Margins. Report for the Parks Unit,Christchurch City Council.
Crossland, A.C. 1995. Bexley Wetland Landscape Plan:Wildlife Considerations. Report for the Parks Unit,Christchurch City Council.
Innes, K. and Bradshaw, M. 1991. Botanical Survey ofthe Bexley Wetland. Report prepared by the DrainageLaboratory of the Christchurch City Council andWaste Management Unit.
McCombs, K.P.C., Partridge, T.R. 1992. Vegetation ofthe Avon-Heathcote Estuary, Christchurch. ChristchurchCity Council, Christchurch. 50pp.
Owen, S.J. (Editor). 1992. The Estuary. Where OurRivers Meet the Sea. Christchurch’s Avon-HeathcoteEstuary and Brooklands Lagoon. Produced by the ParksUnit. Christchurch City Council.
Partridge, T.R., Wilson, J.B. 1987. Salt tolerance ofsalt marsh plants of Otago, New Zealand. New ZealandJournal of Botany 25: 559-566.
Pattle Delamore Partners reports on environmentalsite investigation. June and December 1997.
Tau, T.M. Goodhill, A., Palmer, D., and Tau, R. 1990.Te Whakatau Kaupapa. Ngai Tahu ResourceManagement Strategy for the Canterbury Region.
Taylor, M. 2000. Freshwater Fisheries Database, NIWA.Personal communication.
SUMMARYThe implementation of this Development Plan willallow the restoration of significant saltmarsh,saltmeadow and freshwater wetland plantcommunities, restoration of natural salinity sequences,and improved bird nesting, roosting and feedinghabitat.
Bexley Wetland will continue to be a place forcommunity involvement through restoration activities,such as planting, weeding and monitoring, recreationactivities such as festivals and bird watching, andeducational activities, such as projects for schoolchildren.
enjoyProtectEducate
Restore
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City Plan Rules for the Bexley WetlandEcological Heritage Site
The part of Bexley Wetland that is within EcologicalHeritage Site 19.01 is shaded on City Planning Maps34B and 41B. There are several rules in the City Planfor the site.
Rules
“2.3.6 Protection of native vegetation, natural featuresand existing landscape character - Open Space 2 ZoneEcological heritage sites 11.05, 29.01, 3.13 and 19.01identified in Part 4 Appendix 2 only.
(a) Vegetation removal(i) The maximum removal or loss of nativevegetation indigenous to the area in anycontinuous five year period shall be 100m2 perhectare. The area per hectare shall not beaggregated over the total area of the site.(ii) The above rule shall not apply tomaintenance and weed control (including theclearance of existing drains and ponds), theconstruction or maintenance of vehicle or foot tracks provided their width is not greater than1.5m, and/or for the planting of speciesindigenous to the site.
(b) Planting(i) The planting of exotic species (includingexotic trees or oversowing) or native plants ofnon-local origin, shall be a discretionaryactivity.(ii) The above rule shall not apply to there-introduction of native species no longeroccurring naturally in the Christchurch area.These species are to be procured from the nextmost appropriate source where they still occurnaturally.
(c) Site CoverageThe maximum area of the site to be covered bybuildings shall be 40m2.”
Appendix 1
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Bexley Wetland Interpretation Signs
The following information is a detailed breakdown of interpretation themes and sites.
type of sign code location description priority
Main entrance
Visitor informationboard
Secondary entrance
Contemplation platform
Interpretation panel
Interpretation panel
Interpretation panel
Interpretation panel
ME
VI
SE
CP
IP1
IP2
IP3
IP4
Wairoa Street roadside
Junction of track from WairoaSt carpark and riverside track
At various walking entrances(see map)
On riverside stopbank
Beside spring near trackjunction (see map)
On platform at end of SeaBreeze Close entrance
At bird hide
At platform overlookingsaltmarsh
CCC standard park entrancesign
Upright board (approx. 1m/1.2m x .6/.8m) Map and visitor
care code (on vinyl behindacrylic) Magnetic whiteboard
(behind glass) *
Upright sign (approx..4m x .3m) Reserve name, CCClogo, Dogs on leads. Option one- reword current standard parkssign. Option Two - sign in same
style as Visitor Informationboard with simple graphic
Fully accessible platform andseating area. No interpretationhere except a reflective quote
relevant to wetlandconservation, possibly
a sculpture.
Full colour interpretation panel,low to the ground interpreting
the freshwater spring. Welcometo the site. *
Panel introducing commonspecies (plants, birds and
insects) of the wetland. Paintedsilhouettes and labels create a
simple interactive quiz. *
2-3 panels interpreting wetlandhabitats and species. Large
identification books. See TravisWetland Interpretation Plan for
ideas for bird hideinterpretation.
Interpretation panel showingthe significance of Bexley aspart of the Avon / Heathcote
Estuary.
On completion of carparkand track connection
On completion of carpark,track connection fromcarpark to Bexley Rd
To be mounted aseach track entrance
is completed
Not a high priority althoughthere is interest from a localcommunity group so couldbe an immediate project
Medium priorityBexley Wetland Trust
is keen to progresswith this
Medium priority whensite is more established and
funding available
Longer term priority.Ideally suited when coastalbush habitat has developed
to a shrubby height
Longer term priority,dependent on whether
visitors use track
*For more see Detail of Interpretation panels.
Appendix 2
53
Detail of Interpretation Panels
Visitor Information Board (VI)
Interpretation Panel - Springs (IP 1)
This panel could include:• Welcome to the site• Use and significance of springs to Maori (an illustration)• Maori name - Te Puna O Te Puhi Ariki - “spring of the chiefly woman”• Source of springs - wider hydrology including a graphic• Impact of freshwater and saltwater mix
Interpretation Panel - what’s here today? (IP 2)
This set of panels, aimed at children and family groups,could be in two parts:1) An introductory panel at the edge of a viewing platform. A standard interpretation panel with text introducing the common plant, bird and insect species that can be seen on the wetland tracks. It could be a quiz - Have you seen any of these today? Have a friend cover up the hand and see if you can guess the names of the plants and animals.
2) Animal silhouettes placed on posts around the platform. Around the edge of the platform silhouettes of species (raupo, herons, damselflies ...) could be painted. The shape of a hand could be painted on in a different colour with a small label naming the species (maybe with a photo and/or text note).
Visitor Care Code
• Cartoons to show impact of dogs on the nesting and roosting birds.• Show a positive and a negative image.• Beginner’s guide to bird watching• Contact and more information details
Magnetic Whiteboard
Behind a glass case to protectmaterial from theft. For informationsuch as:• Seasonal information (the birds are nesting - time to take special care)• Events• New arrivals of species• Current developments
Map
To show:• Existing walking tracks• Proposed tracks (in lighter colour)• Existing habitats (colour coded like development proposal)• Selected proposed habitat developments - take care to distinguish between proposed and existing
Appendix 2