Sea level rise and the Christchurch rebuild

Jim Salinger delivered a timely warning in Christchurch this week when he pointed out that the city in its rebuild would be wise to work to at least a one metre estimate for sea level rise rather than the current estimate of 50 cm.

There’s a report on the Stuff website, and in the Waikato Times print edition there was a little more that evidently didn’t make it to the website.

The 50-centimetre estimate on which the council currently works is based on outdated science, Salinger said. Estimates of how much ice is melting in Greenland and Antarctica are more definite and the reviews are saying that we’re looking at a 50 to 160 cm sea rise. Some local bodies in Australia are now using a one metre estimate.

He illustrated with reference to areas like Brooklands “where you have the Waimakariri [River] coming out to the sea. You can have floods coming down the river at the same time as a storm surge, and they’re really at a lot of risk from inundation and flooding.”

In the Waikato Times piece he also referred to push-back from the insurance industry. “They may say, ‘If you build there we won’t insure you because the risk is too high’.”  The paper reported that Salinger had met with council staff the previous day to press the case for a one metre estimate, with a response from the council that it was “considering its options” and “would take Dr Salinger’s comments into account”.

Let’s hope they take them very seriously into account and incorporate them into their plans. It would be a supreme irony if the Christchurch rebuild paid attention to seismic safety but overlooked vulnerability to sea level rise. The infrastructure implications for New Zealand carried by a rising sea level are very great and very costly and will extend long into the future if global temperatures are permitted to rise to the height currently in prospect. If the Christchurch rebuild offers opportunity to pre-empt any of those future threats and costs, that’s an opportunity to be grasped.

15 thoughts on “Sea level rise and the Christchurch rebuild”

  1. Decades of breathless predictions of over a m of sea level rise…
    Meanwhile the real world continues to be the ultimate catastrophism denier:
    Yes that’s right: 3 mm/year.

    It is bad enough that Christchuch is experiencing one disaster, without the added disaster of unnessessary restrictions on where they can rebuild based on the collapsing phopesies of climate alarmists.

    1. This certainly seems to be the viewpoint at the opposition blog:

      Whatever may be happening to eustatic sea levels, New Zealand’s sea level rise has been decelerating for some years. Then there’s the fact that there’s been no significant SST rise this century (the heat has gone to the ocean depths instead).

  2. I had the pleasure of spending some time with Jim a few weeks ago at meeting in Boulder, likewise with Kevin Trenberth (who is from Christchurch and stil has relatives there).
    Both know what they are talking about and neither they (nor Niash, who I don’t know, but obviously knows his stuff, too) would be so naive as to use 1992-201 straightline history to predict 2100AD. Hint: among other issues, ice melts faster when it’s warmer, and of course, the meltback of the Arctic Ocean won’t help, since more energy every summer will go ints warming the ocean, not melting the ice. Lower albedo wont’
    help, either.

    Here in SF Bay Area, the current proposed guidelines:
    “Sea level rise from global warming is a fact. Water levels in San Francisco Bay have risen nearly eight inches over the past century, and scientists agree that the rate of sea level rise is accelerating. In April 2009, a San Francisco Bay Conservation and Development Commission (BCDC) report was released summarizing the latest scientific research on climate change. While exact future in­creases in sea level rise are uncertain, scientists believe it is likely that the Bay will rise 10 to 17 inches by 2050, 17 to 32 inches by 2070, and 31 to 69 inches at the end of the century. ”
    (So, by 2100, that’s .8 to 1.7 meters. Of course, SLR varies by region anyway, but I’ve participated in political planning exercises on what that means here. Not nice. One thing people don’t think about much is sewage systems in relatively flat areas near the sea. )

    I’m sad for Christchurch, having enjoyed my visits there.
    But I’d be really sad for them if, given that they have serious rebuilding to do anyway, they didn’t use the best available science to guide them, because it will get really expensive.

    1. “get really expensive”??
      NEWSFLASH: It already has. It’s the biggest disaster in relation to GDP in a developed country in the last 50 years. That warmists wish to compound this disaster by forcing up the cost of rebuild by massive restrictions (as well as the extra costs for fuel, materials and everything else that their energy rationing policies will bring about) is obscene.

      1. “That warmists wish to compound this disaster by forcing up the cost of rebuild by massive restrictions (as well as the extra costs for fuel, materials and everything else that their energy rationing policies will bring about) is obscene.”
        Not as obscene as standing idly by when even worse disasters loom. It will compound the tragedy of Christchurch if just about the time the city starts to recover, we realise that all the rebuilding was futile and that we would have been better moving out nearer West Melton.
        Of course the climate change that could/will destroy ChCh is going to create havoc all around the world, not just in coastal areas. The worry is that so many people refuse to believe the warnings or put short term financial gain ahead of the future of humanity.

  3. The worry for ChCh is not that the sea level is threatening us with inundation, it’s that it will. The Cathedral Square is only 4m above sea level with the high tide mark on the Avon within the CBD, just below the Kilmore St bridge. It won’t require water sloshing through what remains of the cathedral for confidence to collapse, only the realisation that it will eventually. We have enough problems with Insurance companies being spooked by after-shocks, it won’t take much for them to add flooding to the not-included list even if they are prepared to offer any sort of cover. Insurance companies are not like fossil-fuel companies or politicians with agendas requiring business-as-usual, they are very, very long-sighted. They know damn well climate change is not a hoax and are already unwilling to offer protection to people who fail to heed warnings.

    1. Well if Cathedral square is only 4 metres above sea level, it will be underwater within 2 centuries, and we won’t be able to stop that happening no matter what we do. Too much thermal inertia in the oceans.

      1. True. Possibly sooner if IPCC’s perchance for underestimating the speed of transition is true to form.
        An engineer friend leapt into the fray with the observation that the value of Nth Canterbury was high enough to warrant throwing up a dyke to hold back the rising water, even if it had to be built from Scarborough to Waipara. I deflated that hope by asking about how far upstream on the Waimakariri and Ashley Rivers the walls would have to go and how porous did he think the gravels of Canterbury would be to sea water bubbling under the dykes? Then there’s the problem of Lake Ellesmere…
        Sadly the only solution that will work (Don Elder’s claims not-withstanding) is a serious cutback in our fossil fuel consumption. Why is that little pink birdie up in the tree going “oink, oink!”?

    1. He’s a former National Party MP and Minister and is chairman of the ironically-named NZ Climate Science Coaliion. He knows as much about sea level rise as his comments indicate – ie he knows what is passed around in the denialist world.

  4. Christchurch has suffered a disaster but rebuilding the City and then,in fifty years time, seeing large lumps of it unusable would compound the problem.
    The last IPCC report indicated 650mm sea level rise at today’s CO2 rate of production and the next one is going to be in the 1.00mt to 1.8mt range if advance reports are anything to go by.
    Look at the flood map set at one meter. Try Europe and UK East coast California and Florida. We might have some problems but the big nations are going to lose major cities.

  5. Town planners need to:
    1) Understand the best science we have, including the uncertainty limit, and as any insurance company will tell you, uncertainty is not your friend.

    2) Hash out what to do locally in light of the expected trajectory.
    That might be:
    a) Ignore it.
    b) Start modifying building codes and zoniing.
    c) Do rational things with infrastructure, i.e., do not rush out to rebuild things before the end of their natural lives, but if something’s to be rebuilt anyway, do something sensible in whatever time horizons people work to.
    Town planners I’ve met work to 50-100 years. I have no idea if that’s typical.

    d) SLR planning is very, very tricky politically – I’ve been through one simulation of that, having attended this. In some places, it might be way cheaper in long term to build dikes uphill at point X than at the edge of the water, point Y. Those uphill from X will have one opinion, those living/owning between X and Y another. In some cases, the town might want to buy people out.

    In addition, given a shore shared by towns A, B, and C, it is fairly hard for town B to select Y, when A and C select X, i,e. nearby communities have to cooperate.

    Of course, when it comes to water, the Dutch are experienced. See ,a href=””>Netherlands floating houses. In some places, making structures float, like boat docks, is a really good idea.

    Of course, storm surge is a real issue in some places, but also, somebody mentioned rivers. Low-lying cities on flat coasts with big rivers flowing through them are really awkward. Anyone who’s been to Shanghai may know what I mean.

    At least Auckland and Wellington are hilly.

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