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It’s washing away – why aren’t they saving Pukerua Bay’s coastline?

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by Jim Mikoz
Why is the Porirua City Council letting the Pukerua Bay coastline wash into the sea?

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As Secretary of the Wellington Recreational Marine Fishers Association I called a public meeting to introduce a closed area for all shellfish gathering in this valuable area. The waters off Pukerua Bay attract bait fish and in turn trevally, kahawai and snapper which form a major component in our MPI recreational bag limit. Yet now we find the Council has failed to protect this area from sediment and land collapse.

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A past attempt to protect the land with a Geotec strip and small stones was a complete failure and now the walking track is under threat. Not only is the track under threat but you have an untreated sewage pipe with three to four metres exposed and at the point of breaking into the sea.

It would be cost effective to protect the pipe now rather than wait for it to collapse into the sea and then build another wastewater pipe down the middle of the road with attachments to the many properties. The cost to lay another waste water pipe to link into the houses and install another pumping station would be well over five million dollars.

At the boat ramp there has been no attempt to protect the land from the sea and four metres of grassed bank has disappeared into the sea along with a seat.

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Recently a table and seats were installed but that area is being undermined and is slumping into the sea. The damage has occurred as a result of a big storm several months ago. Such storms should never be considered a once in a hundred years event as they will occur more often and with our weather patterns rapidly changing in the last twenty years; it is quite likely the next storm will be even bigger.

In our submission to the WRC Natural Resources Plan I identified how councils are not preparing our coastal resources against the effects of climate change. However it is hard to describe to a council what is about to happen in the future until the result of their lack of marine knowledge is exposed.

Porirua City Council is not alone in failing to build adequate coastal defences against the effects of climate change. Photos I have taken at Pukerua Bay, Paraparaumu Beach, Port Road and AirPort Road all show this lack of marine knowledge.

The effect of climate change is not just about raising sea levels, as at times the opposite takes place with lower than normal sea levels. This has been caused as the sea level moves between a high or low air pressure systems.

This low water is becoming a major issue for those with large boats moored within the Mana Marina. The recent storm and earthquake has reduced the depth of the bar in the designated shipping channel into Porirua Harbour to a point where boats of around fifteen metres in length cannot travel in or out of the Harbour two hours either side of low tide.

I have been representing all NZ recreational marine fishers on Mfish, MPI, MofE and DOC NGO forums for 37 years. At these meetings we were informed that climate change would raise sea levels in twenty years’ time by one centimetre. I knew they were not describing how climate change was effecting our marine environment, and councils and Government were being subjected to some serious misinformation from NIWA and Victoria University describing Cook Strait currents.

When I discovered a rock south of Ohau Point 400 millimetres above the surface – when LINZ marine charts described it should have been two metres below the surface – this demonstrated there was a problem. I proved it had been caused by a higher than normal air pressure system over Wellington. NIWA acknowledged that this was the first time air pressure had been identified as lowering sea levels.

The extra volume of sea water is having another effect as it is increasing the surface currents and bringing warmer air and water down from the Coral Sea a lot faster than 20 years ago. The increase in surface currents when combined with stronger than normal winds and assisted by a shifting low pressure system is causing a massive increase in surface current speeds. Police and rescue authorities are not being provided with this information; they are provided with tidal predictions based on the sea bed and not any information describing surface currents which in a storm travel with the wind carrying everything with it.

The location of a storm surge has never been predicted although the Meteorological Service obtains air pressure and wind readings by the hour and has access to tidal information. We watched the deep low pressure system track down off the west coast to pass through the Cook Strait and combine with a southerly to produce a storm surge in Wellington that flooded the industry along Port Road at Seaview and washed out the railway tracks alongside State Highway Two. Such events are predictable 24 hours in advance but not from Government science providers as they still think the currents in the Cook Strait are produced by tides.

Building an adequate future proof coastal defence system at Pukerua Bay will be a challenge for the council. Its last effort failed in the next big sea. The use of Geotec mats may be alright around a wetland to hold back dirt, but it is not suitable to hold back the sea. Placing small rocks in the gaps between the larger rocks would not make a very strong wall on land without concrete to secure the bank let alone building a wall of rocks facing the sea knowing it would be subject to wave after wave in a storm surge.

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The Hutt City Council built a wall with one tonne cubes of concrete at Korokoro but they have cracked and become dislodged.

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At Paraparaumu, the Kapiti Council failed to protect their wooden walls with rocks and the sea washed behind the wall and blew away the wooden runners leaving the posts. An effort to protect properties with one tonne concrete cubes also failed as the cubes are sinking below the sand allowing the sea to wash away more land.

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Along Port Road, a layer of rocks was built to to protect the road but they all disappeared to expose concrete pipes and old building waste with large blocks thrown up on the road.

If the Porirua council doesn’t take immediate steps to protect the coast line at Pukerua Bay, then in a short time it could look worse than Paraparaumu Beach with the sea closing in on the houses and the sewage pipe discharging into the sea.

Jim Mikoz is President of the Wellington Recreational Marine Fishers Association. This is an edited version of a letter that he has sent to the Porirua City Council.

3 comments:

  1. David Lindsay, 31. May 2017, 16:52

    The answer to this sea erosion problem was tackled by the settlement of Waimarama on the east coast south of Cape Kidnappers. Intially large concrete blocks were tried, but were ineffectual. Then someone had the idea of using very large limestone rocks which they tipped over the bank into the eroding area. And what do you know? The sea crashed over these rocks and trickled down through the uneven surfaces. The back stabilised, and the beach itself, which had become totally shingle, got its sand back. I’m surprised other settlements haven’t tried this solution.

     
  2. Jim Familton, 5. June 2017, 21:40

    It will be impossible to stop erosion in the future when the sea levels rise a meter and with even bigger storms.
    We all must do our bit to reduce global warming. Use public transport or a bike. Switch to electric cars, buses and trains.

     
  3. Keith Flinders, 7. June 2017, 12:51

    So if the Regional Council is working to avert the effects of climate change, then why is it getting rid of non polluting electric trolley buses. Then we have KiwiRail wanting to replace non polluting electric locomotives on the North Island Main Trunk with diesel ones. To date no public protests against these ill considered decisions.

    In Piatra Neamt, Romania, the trolley buses were withdrawn in January of this year, but due to public concern and protests they are to be re-instated next week. We should be taking note of this.

     

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