Southerly by David Haywood

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Southerly: That CERA Rumour

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  • Russell Brown,

    Just for clarity, I deleted Islander's last comment while Ross was replying to it. It was just a bit abusive for a Monday.

    Auckland • Since Nov 2006 • 18516 posts Report Reply

  • James Green,

    In response to Kyle: While I can't guarantee that they don't use a ghastly amount of energy, Santa Monica has an outdoor ice-rink in what passes for 'winter' there. While I don't think it gets much sun on the ice, the outdoor temperature probably passes for summer *cough* in Dunedin (daily highs in the 15-20 range).

    Dunedin • Since Nov 2006 • 682 posts Report Reply

  • Rich Lock, in reply to Rich of Observationz,

    London manages an outdoor ice rink, although it has slightly cooler average winter days and a lot less insolation.

    Insole-ation? Well, due to the earthquake, there are more fallen arches in Chch.

    Did the temperature just drop in here? I'll get me coat.

    back in the mother countr… • Since Feb 2007 • 2326 posts Report Reply

  • kevyn, in reply to Lilith __,

    Regarding the comparison with the 3m tsunami, I do have the original GIS files from the tsunami evacuation study because that study is complete and in the public domain. None of the information gathered on the lateral displacement of the riverbanks is allowed to be made public but you can replicate this for yourself with a tape measure if you measure the displacement at the bridge abutments and the width of cracks on the riverbanks and along the neighbouring roads. The main point of doing this is to measure how far the banks have intruded into the waterway as this allows you to calculate the amount of riverbed heave without having to get wet. Once you know how much the profile has changed you can calculate the reduction in river capacity when springtides in the estuary essentially act as a damn and cause the rainwater runoff to backup along the river.
    If you can measure how far the cracking extends from the riverbed and the total width of the cracks then you can calculate the average amount of subsidence in that area due to lateral spreading. There are currently no official figures for the amount subsidence due to the removal of liquifaction silt but anybody who helped remove it can give a reasonable estimate, probably varying dramatically from property to property but generally 1-15 cm was my observation. A similar amount needs to be provided for the effect of compaction.

    When all this is added together it adds to a flood risk (defined by the RL) covering the same surface area as a 3m tsunami (but without the damage caused by the speed of inundation in a tsunami).

    There has been both uplift along the Heathcote and subsidence along the lower Avon as result of the Feb 22 quake which will tend to focus the springtide effect into the Avon but the size of that effect is to difficult to estimate.
    http://www.starcanterbury.co.nz/local/news/map-shows-quakes-fury/3952900/

    The cost comparison only came close to parity with the cost of relocation because the uplift and subsidence has a big impact on gravity sewerage system and assuming that the rebuilt local roads will need to have gravel bases normally only used on main roads due to the next Alpine Fault quake currently having a 80% probability of occurring within the normal design life of local roads. It is probably over 95% for the design life of underground infrastructure.

    But note that the rebuild cost is the same as the buy-out cost only because the infrastructure cost is assumed to have already been included in the subdivision section prices. If that's not the case then, along with the social costs of forced relocation, the relocation will be more expensive than the rehabilition option. But I think you'll find that social costs are something that governments are not good at with infrastructure decision making.

    Lincoln • Since May 2011 • 4 posts Report Reply

  • kevyn,

    Plus you'll need the council's Waterways, Wetlands and Drainage Guide to give you the baseline figures for the RL, recorded tide and rainfall levels, etc.
    http://resources.ccc.govt.nz/files/Appendices2.pdf

    Lincoln • Since May 2011 • 4 posts Report Reply

  • Kyle Matthews,

    In response to Kyle: While I can’t guarantee that they don’t use a ghastly amount of energy, Santa Monica has an outdoor ice-rink in what passes for ‘winter’ there. While I don’t think it gets much sun on the ice, the outdoor temperature probably passes for summer *cough* in Dunedin (daily highs in the 15-20 range).

    Sun doesn't help. Alexandra has sun on the ice for several hours during the day, and they often have to schedule their activities to finish by about 1pm, or start after 4pm. The bit in between the machinery can't keep the ice cold enough. Tekapo has parked their rink right in against a hill and surrounded by trees to prevent this being a problem.

    It's possible to have an outdoor rink in chch, but you should plan most of a million dollars to set it up, and over $100K for a winter of ice.

    Christchurch does need a second rink, but it should be a proper indoor rink. You can't book ice at the current rink unless you book about 6 months in advance, or want to get ice at 1am.

    Since Nov 2006 • 6150 posts Report Reply

  • Ralph Boardman,

    Yes, but you have not considered sea-level rise, up to 1.5m over 100 years. It would not be a sane thing to ignore, but we are pretty good at ignoring things here, aren't we?

    Chch • Since Jun 2011 • 1 posts Report Reply

  • David Haywood,

    I didn't realize this thread was still going, but am impressed that a couple of people are continuing the long tradition of assuming that I must be an idiot...

    Kyle Matthews: I used to teach thermodynamics at UoC -- so no, I don't think that you can 'cool' an icerink with river water at 8 degC! As Ross pointed out, I was talking about the improvement in performance from rejecting heat (from the hot heat-exchanger on the refrigeration plant) into river water. This would mean that the refrigeration plant was operating over at least an 8 K smaller temperature difference than if rejecting heat to a gas such as air. Which would mean a significantly higher COP and a proportionally smaller electricity bill.

    Ralph Boardman: no, I didn't forget about sea-level rise, but it's not relevant to the discussion of abandoning 100 metres around the river bank. Sea level rise would affect some of the lower river, but equally all the land surrounding it -- not just the nearest 100 metres. It wouldn't affect the upper river.

    In the event of this sort of sea level rise (the CCC were talking about 500 mm, last time I checked) it would be almost certainly be cheaper to build a dyke than abandon most of East Christchurch. While we're at it maybe we should make the dyke a tsunami wall -- I've just been looking at the possible effects of a tsunami on CHCH.

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • Islander,

    Slightly OT but
    anyone else had the message from "hedgehog100" apropos Fletchers, demolition tenders, and the government?

    I dont want to post my copy here (because it comes with a loong list of cc.s) but just checking out the current Fletchers' shareholding could be enlightning-

    Big O, Mahitahi, Te Wahi … • Since Feb 2007 • 5643 posts Report Reply

  • Robert Urquhart, in reply to Islander,

    Slightly OT but
    anyone else had the message from “hedgehog100” apropos Fletchers, demolition tenders, and the government?

    No, but I've just seen a copy of CERA's response posted to Sue Wells' blog

    Christchurch • Since Mar 2009 • 140 posts Report Reply

  • Islander, in reply to Robert Urquhart,

    Thanks Robert! Have onsent this link to the people who sent me it.

    Big O, Mahitahi, Te Wahi … • Since Feb 2007 • 5643 posts Report Reply

  • Tasneem Gould,

    So that CERA rumour turned out to be tru-ish, then didn't it.....

    Christchurch • Since Jun 2011 • 2 posts Report Reply

  • Islander,

    Tru-ish - for insurance companies, who werent mentioned, The Government & Fletchers connection was refuted.

    Big O, Mahitahi, Te Wahi … • Since Feb 2007 • 5643 posts Report Reply

  • Jeanette King,

    Interesting article in the Sunday Star Times today about the need for different types of house foundations required to work in liquefaction prone areas.

    Engineers are working on designing better foundations for houses to protect people's homes from the devastating effects of liquefaction.

    Hope they are cognisant of your ideas David!

    Edgeware • Since Oct 2010 • 27 posts Report Reply

  • David Haywood, in reply to Jeanette King,

    Interesting article in the Sunday Star Times today about the need for different types of house foundations required to work in liquefaction prone areas.

    Thanks for pointing that out, Jeanette!

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

  • David Haywood, in reply to Tasneem Gould,

    So that CERA rumour turned out to be tru-ish, then didn’t it…

    I am (naturally) going to disagree with that:

    1. There was no 100-metre abandonment strip.

    2. And, in fact, some portions of the river bank (e.g. along River Road) are not in the Red Zone.

    3. The land can be cost-effectively remediated and will be remediable.

    4. There will be no giant park (as things are currently planned).

    The bit I didn’t foresee – and, obviously, I totally admit my lack of vision here – is that the government would move people off the land in the short term, and then have the land remediated by the private sector via onselling the land to property developers in the long term.

    Which I gotta admit is a smart solution by the government…

    Dunsandel • Since Nov 2006 • 955 posts Report Reply

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