Thames-Coromandel District Council has posted some Frequently Asked Questions on its website regarding the proposed swimming pool near the Thames airfield. There are plenty of questions it has not answered, and many of the answers given only tell half the story.
Question 2 –In the future, to accommodate sea level rise, how much extra will it cost to provide additional flood protection for the site?
The answer suggests there will be no extra cost for the site. But this ignores the huge cost involved in protecting the whole of the Thames coastline from Kopu to Tararu including Thames CBD (not to mention Te Puru, Waiomu and Te Mata and Coromandel). Maybe not everywhere will get protection and some areas may have to be abandoned in coming decades. Before we spend another $20 million on a major facility which could be placed somewhere else safer, shouldn’t we be finding out first whether the existing infrastructure at Totara has a long-term future? Maybe when all of the options and costs are known, Thames Township and CBD and the State Highway (and every other low lying town and city in NZ) will be a priority for funding and protection, but Totara may not be?
Question 4 Does the proposal increase the risk of flooding of the pool?
Here the answer provides a false choice. The answer confuses river flooding with sea flooding which is an entirely different beast. Yes, the existing swimming pool is beside the Hape stream which can flood. But the future risks from climate change from river flooding are much less than the identified future risk from sea flooding. Experts tell us that inundation from sea flooding will be the dominant flood risk in a few decades. So the purported present 1-in-100 year protection from the Waihou River flooding (note river) is meaningless, without the greatly increased risk from inundation from the sea in the future being considered.
Also, the legal test under the New Zealand Coastal Policy Statement is whether the new development itself will increase the risk of a hazard, not whether the new development is less risky than the one it replaces.
Question 5 is the residual risk of flooding?
The answer suggests that residual risk is reduced because the proposed swimming pool would be approximately 500 m from the seawall. But this ignores the fact that the land between the proposed swimming site and the seawall is flat and less than half a metre above sea level. So any inundation through or over any seawall would rapidly inundate the site. This can be seen from the January 5, 2018 storm surge in Kaiaua where farmland was inundated far inland.
The sea flooding of the Hauraki Plains in 1938 extended kilometres inland.
Even with a seawall, the residual risk to the Totara site is significant. The recent inundation of Edgecombe when the stopbank was breached also provides a good example of residual risk.
Question 8 Is the land at Totara site susceptible to subsidence?
While the answer admits that subsidence is an issue, it makes a comparison with the Hauraki Plains, but fails to mention that much of the coastal land and the seawall between Kopu and Moanataiari is subsiding at a rapid rate. For example, the seawall at Moanataiari has subsided 0.2 m since it was built about 15 years ago, and back in the 1970s, the seawall at Danby Field had already sunk by 1.5 m. What the answer fails to mention is that subsidence is a concern because the rate of subsidence has to be added to the rate of sea level rise to calculate the local threat.
TCDC is fully aware of the subsidence plus sea level rise threat because it has received regular reports from engineering consultants about this issue relating to the Moanataiari seawall. The answer from TCDC tries to divert the issue to one of the land stability for buildings protected by the seawall but this is not the major concern.
Question 9 Will increases and groundwater cause problems for the site?
Huge problems with rising groundwater due to sea level rise had been identified in South Dunedin and major studies have been undertaken, and the identified potential responses will cost millions of dollars. TCDC summarily dismisses these threats by suggesting that groundwater can be managed through stormwater and drainage systems when at this stage it has no idea whether that is feasible, or affordable.
Questions which were not asked and answered.
1 does the proposal comply with the New Zealand Coastal Policy Statement and recent authoritative legal precedent? What legal advice has TCDC sought and received on these issues?
2 does the proposal comply with the latest guidelines from the Ministry for the Environment and the advice on the New Zealand Coastal Policy Statement from the Department of Conservation?
3 why is TCDC not waiting for the outcome of the expert hazard assessments which will have to be undertaken under its Coastal Management Strategy and the Shoreline Management Plan it is developing for this area? $2.6 million has been set aside for this work over the next 3 years. Why has TCDC rushed in to spend $1 m on the land purchase at Totara before this essential work has been done and before it knows that the site is viable?
4 why is TCDC insisting on proceeding with this site when other elevated sites may be available which do not have flood risk?