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S. Warr, Greater Wellington (unpublished, 2009)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!!!!