Porirua Harbour and Catchment Strategy and Action Plan

 The History


In 2012 Porirua City Council (PCC), Greater Wellington Regional Council (GW), Wellington City Council (WCC) and Ngati Toa Rangatira adopted the Porirua Harbour and Catchment Strategy and Action Plan, a move that pleased all those with concerns about the degradation of the natural condition of the harbour. These concerns had been around for at least least 40 years - and much longer for Ngati Toa, who had experienced over many decades a severe decline in their ability to harvest kai moana. The building of the railway and SH1, development of the Porirua CBD and the Titahi Bay Road extension all required land reclamation in the Onepoto Arm, reclamation which either destroyed or seriously modified the shellfish environment. Little or no attention had ever been paid to Ngati Toa's concerns. (The picture is a National Library image of Maori gathering shellfish in Porirua Harbour in the 1840s. Painted by Samuel Charles Brees.)


1970s: Beginning to listen

Pressure to consider the effects of urban development on the harbour environment, especially in the more pristine Pāuatahanui Inlet, began to mount in the early 1970s, when development in Whitby resulted in massive depositions of silt in Browns Bay. To its credit PCC persuaded the Minister of Science to authorise a detailed investigation of the Inlet's physical and biological environment. This would provide a baseline against which further development could be assessed and its effects monitored. DSIR developed the Pāuatahanui Environmental Programme and reported results in 1980 in Pāuatahanui Inlet - an environmental study.


1980s and 90s: Consulting the community

The DSIR study was influential in defeating a proposal to develop a causeway across the mouth of the Inlet and over the Mana sand flats as a SH1 Mana bypass. Its effect would have been the destruction of much of the intertidal area as well as degrading the visual qualities of the Inlet as seen from Dolly Varden beach.


The 1990s saw widespread concern that the local authorities were still not adequately recognising, let alone protecting, the Inlet's values. In 1999 PCC and GW responded by hosting a workshop to discuss these concerns. The outcome was the establishment of the Pāuatahanui Inlet Advisory Group, whose task was to seek community input into the preparation of an action plan. 


2000s: Detailed planning


2000: The advisory group produced the Pāuatahanui Inlet Action Plan, Towards Integrated Management (PIAP), which laid out the issues, the actions needed to address them, and the outcomes sought. PIAP was accepted by PCC and GW who immediately commissioned a Pāuatahanui Restoration Plan which was produced in two stages in 2002 and 2004.


2002: The Pāuatahanui Inlet Community Trust (PICT) was established. Its primary objective was to 'facilitate the implementation of the Pāuatahanui Inlet Action Plan' but, very importantly, it also set out to 'promote and support the development and implementation of an action plan for the Porirua Harbour arm' [i.e. Onepoto]. The outcome of this lobbying was that in 2006 PCC formally recognised that the harbour is an important city asset and adopted 'Healthy Harbour, Inlet and Waterways' as one of four strategic focus areas.


2008: A Porirua Harbour programme was established. Work began on developing this programme into a Harbour Strategy, which was finalised in 2012  - both the Pāuatahanui Inlet Action Plan and the Pāuatahanui Restoration Plan are integrated into this whole harbour strategy.


The Strategy and its accompanying Detailed Action Plan are available on the Porirua City Council website:




2011: The Porirua Harbour and Catchment Community Trust (PHT) was established. It included representatives from PCC, GW, WCC and Ngati Toa Rangatira. Its key objectives were to:

  • advocate for the sustainable management of the harbour and its catchment; and
  • foster an understanding of ecological and environmental issues within the harbour and its catchment through education and community awareness.


2015: The Pāuatahanui Inlet Community Trust considered that it had achieved its aims and objectives and the ongoing management of the whole harbour was now in the hands of PHT. By agreement PICT was formally disbanded in 2015 with several members joining the Guardians of Pāuatahanui Inlet to continue advocacy of PI under this alternative organisation.



What is the Strategy Aiming To Do?

Quite simply, the Strategy aims to restore '...a healthy catchment, waterways and harbour, enjoyed and valued by the community'. To do this, the Strategy attacks the 'Big Three' agents responsible for the current depressed state of the harbour environment:

  • Sedimentation
  • Pollution
  • Ecological degradation. 

The Detailed Action Plan lists 110 actions considered to be necessary. Some are very large, such as refurbishing stormwater and wastewater systems city-wide to reduce pollution. Some are long term, such as re-vegetation of erosion-prone areas of the catchment hills to reduce sedimentation. Some address the need for more research and some recognise the need for programmes to raise public and business awareness of the problems and how they can do something about them. The good news is that more than half of the actions are already underway.


To get a feel for harbour restoration issues you can't go past the FAQs page on the PCC website:



References to community involvement are everywhere in the Action Plan, and as a community organisation, we strongly support this focus. It's vital that the community is on board and able to contribute to achieving the Strategy's aims. We are pressing for a prioritised list of projects involving the community to be developed.


(The photo shows seagrass at Ivey Bay. Healthy seagrass growth is vital to the Inlet.) 



So, How is it all going?

You can check out how well the Strategy is being implemented by looking at the PCC's webpage:


Much of the work of the past two years has been in overhauling the city's infrastructure systems such as sewerage and stormwater drainage. While this doesn't seem to have much to do with the harbour itself it is in fact crucial to reducing harbour pollution - the second of the harmful 'Big Three'.

Other work relates to the other harmful elements: sedimentation and environmental degradation leading to erosion. The approach to dealing with these is largely through restoration planting, fencing and, most importantly, public education. These are all underway. Long-term plans have been drawn up for catchment-wide sediment reduction and estuary restoration options.



Sediment build-up in the harbour due to human activity is probably the most serious of the 'Big Three'. Natural changes such as the slow erosion of the land over millennia, and the consequent inevitable eventual infilling of the harbour, proceed so slowly that the flora and fauna of the harbour can adapt; but the rapid pace of human interference with natural processes through deforestation, agricultural practices, reclamation of the foreshore, urbanisation, road building etc. is producing radical and rapid changes to the marine environment of the harbour. For example the 'worst case scenario' is that, if erosion of sediment from the catchment continues at its present rate, then the Pāuatahanui Inlet will be a swamp in as little as 150-200 years. Compare that with the estimate of 1300-1700 years if sedimentation rates could be reduced to pre-European levels. That is precisely what the Porirua Harbour Strategy is targeting by 2031. In the short term - by 2021 - the target is to reduce sediment input by 50% (see page 8 of the Detailed Action Plan).

These targets are ambitious but the experts advise that they are possible*. Getting there will require an enormous effort of will by the local authorities and by the people who live or work in the harbour catchment. Land usage must change. Re-vegetation of the steeper, more erosion-prone, land must take place as quickly as possible. Urban development must be as eco-friendly as possible, with reduced cut-and-fill and other sediment-inducing activities. At the same time action must be taken to restore those parts of the harbour proper that have become severely degraded.


What about dredging?

Would removing some of the accumulated sediment, e.g. the offshore central sand banks, help in the revitalisation of the Harbour? Dr Mal Green of NIWA has advised PCC that while dredging could increase tidal flushing and improve navigability, it would be costly and/or impractical and could, for example, destroy these banks as a fish nursery, affecting both local recreation fishing and regional commercial fisheries. While Dr Green suggests that dredging should not be ruled out entirely as a management tool, his view is that a first priority should be to urgently and drastically reduce the inflow of sediment into the harbour.



GOPI monitors the progress being made in implementing the Strategy by analysing the annual reports and making submissions on them. The Porirua Harbour Trust also produces an innovative Porirua Harbour Scorecard. We recommend you take a look at both the 2013 and 2014 scorecards:








Last Updated: 03/02/2017 7:41pm