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Home » Submission on proposed variation 17 to Wellington City District Scheme

February 2000

The Geological Society of New Zealand Inc. represents the professional interests of New Zealand geologists. With a membership of 750, it includes most New Zealand geologists, and it is a member body of the Royal Society of New Zealand.

We are concerned that the plans to develop the Lambton Harbour area outlined in Proposed Variation 17 to the Wellington City District Scheme entirely fail to consider natural hazards, specifically (a) poor foundation conditions, (b) the ground shaking hazard from earthquakes, including possible subsidence and liquefaction, and (c) the potential danger from tsunamis and exceptional storms.

The whole of the Lambton Harbour area is reclaimed land. The sea floor was uplifted during the 1855 Wairarapa earthquake, and was subsequently raised above sea level by dumping artificial fill during the succeeding 40 years.

(a) Poor foundation conditions

The artificial fill and underlying soft sea-floor sediments provide very weak foundation conditions. Intensive investigation and engineering work will be required before sites can meet minimum foundation requirements for large buildings. For example, considerable, disruptive site preparation work was required for Te Papa, and there is no reason to believe that this would be less for the planned multi-storey buildings.

(b) Earthquake hazard

Such poor foundation conditions often amplify earthquake shaking relative to sites on solid rock, and liquefaction of soft sediments is common. This can cause subsidence and ground deformation. It can be anticipated that any buildings on Lambton Harbour are likely to suffer greater earthquake shaking than, for example, similar buildings on solid rock sites elsewhere in the Wellington region.

Liquefaction occurred on Aotea Quay during the relatively small 1942 Wairarapa earthquake, and a stronger earthquake could cause considerable damage today if the area was covered with buildings.

In the 1855 Wairarapa earthquake the land around Wellington harbour was uplifted, but it cannot be assumed that uplift will happen in future earthquakes Earthquake-induced subsidence is equally likely, especially from an earthquake along the Wellington fault. Studies of the Wellington Fault show that historically rupture of the fault is accompanied by subsidence of the eastern (harbour) side. In the recent Turkish earthquake there was widespread subsidence along the Sea of Marama accompanied by flooding of buildings close to the coast.

(c) Tsunamis and exceptional storms

Any coastal site, including Wellington Harbour, has a risk of damage from tsunamis and exceptional storms, and this would certainly apply to the planned Lambton Harbour development. In Te Papa this has been allowed for by ensuring that no collections are kept on the ground floor of the Museum, but it is unlikely that owners of commercial building would want to consider such restrictions on the location of people or property.

CONCLUSION

Developing further buildings on the edge of Wellington Harbour would inevitably increase the number of people living and working there. We consider that there are real, long-term hazards in developing this area, and that before Variation is considered further there needs to be a full assessment of the hazards and associated public safety issues. This should also consider the earthquake resistance of existing buildings.

The Geological Society of New Zealand does not wish to comment on the aesthetic aspects of Variation 17. We consider that such comments would be premature when questions of public safety have not been addressed.