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Porirua Harbour Seminar
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Talk to Porirua Harbour meetingPaul Blaschke
28 October 2009
Porirua Stream: ecological restoration priorities for
“your stream, your catchment”
PoriruaStream
catchment
Porirua catchment - issues
Terrestrial biodiversity: • Most of the original native vegetation
cover has been lost
• Present day forest is almost all second growth
• Catchment is showing some promising signs of recovery (increased pest management)
Stream and harbour: • Numbers and diversity of fish
populations appear to be declining.
• Sediment movement and pollutants badly affect the water quality and aquatic life in both stream and harbour
• Piping of streams and other development that restricts surface permeability - all threaten natural values.
Pollutants:
• Sediment
• Faecal coliforms
• Nitrogen
• PAHs, DDT, Lindane
The recovery in terrestrial biota doesn’t seem to be matched by what’s happening in the Stream!
Changes in Wellington stream environment
• Changes to natural stormwater flows – hard surfaces
• Modification of streams – piped or channeled
What we had……..
What is now piped……..
Changes in Wellington stream environment
Stream length
0
20
40
60
80
100
120
Porirua Kaiwharawhara Waitangi
pe
rce
nt
los
s
S. Warr, Greater Wellington (unpublished, 2009)
Porirua catchment – priorities for restoration
• Protect and enhance habitat
• Reduce sediment, pollution and water run-off
• Enhance the ecological design elements in flood and stream management
• Promote catchment-wide planning
• Build community support and awareness for restoration
Restoration priorities in the
catchment
• Protect and enhance habitat
• Reduce sediment, pollution and water run-off
• Enhance the ecological design elements in flood and stream management
• Promote catchment-wide planning
• Build community support and awareness for restoration
Protect and enhance habitat
• Protect and enhance existing
vegetation and animal populations
• Reserve areas during subdivision
• Focus on road/rail corridor
http://www.maararoa.wellington.net.nz/Thumbnails/
“Best Bets” species for the Porirua
catchment
• Scan??
Porirua catchment – priorities for restoration
• Reduce sediment, pollution and water run-off
• Enhance the ecological design elements in flood and stream management
• Promote catchment-wide planning
• Build community support and awareness for restoration
• Protect and enhance habitat
“Catchment design”
“Catchment design”- what’s involved?
• Think about all the catchment
• One part of the catchment affects another:– upstream – downstream
– upslope – downslope
– land to water
• Pests and pollinators moving around catchment
• People in the catchment influence each other too!
Catchment design – what?
• Reduce sediment,
pollution and water
run-off
– Set aside riparian land
– Reduce impervious surfaces
– Erosion and sediment
control guidelines
– Water quality
monitoring
Catchment design – what?• Enhance the ecological design
elements in flood and stream
management
– Set aside riparian land
– Floodway building and yard restrictions
– Review structures in streams – fish
passage
– Planting and public amenity in flood
control reserves
Project Twin Streams
"Working together for healthy streams and strong communities: creating a sustainable future.”
• Waitakere City: 10,000 hectares and has a population of 100,000 people.
• Integrate land use planning & management of the three waters to minimise flooding, reduce pollution & siltation in streams & the harbour.
Why Project Twin Streams needs to purchase some properties
Catchment design – what?
• Low-Impact Urban
Design and
Development
(LIUDD)
• Don’t squeeze the
stream!!
Catchment design – how?
• Promote catchment-wide planning– Statutory combined
catchment plan for Porirua Stream and catchment
– Porirua Stream forum
– Forum for sediment management
– Improved liaison between councils and infrastructure providers
Catchment design – how?
• Build community support and
awareness for restoration
– Equitable support for
community care groups
– Raise public awareness of
pollution and litter problems
Accessibility and approachability: a key to restoration
Bring on the walkway/cycleway!!!!