Author Topic: Coastal housing and sea level rise predictions  (Read 4111 times)

Murdoch

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Coastal housing and sea level rise predictions
« on: May 29, 2021, 07:41:44 PM »
Hi,

The answer to my question in this thread will probably come down to how much you trust the accuracy of the science behind sea level rise predictions, but I'll ask it anyway in case there are other factors I haven't considered.

Last year we bought a beach block in FNQ. Old brick house on it, tenanted, great location near boat ramp.
The block is about 4m above sea level, but substrate is matured sand dunes with large trees between block and beach covering about 30m in distance.

It is the region we plan to move to one day, and considering demolition and building a new home on the site.
Demolition costs are minor and given the age of the house and location it is on the block we aren't renovating.

My main hesitancy is whether the block will still be there in 20 years.
QLD legislation sets councils and shires climate change mitigation/adaptation to account for 0.81m sea level rise by 2100.
If this eventuates (or is worse or sooner), then not only my block and nearby suburb (we have one of the highest on the street) will be gone, but so will much of coastal Queensland's suburbs.

We got the property at a steal and it's up 25% in value since we bought it given the market shifts in recent months.

How should I factor in this risk?
Keen on your thoughts.

Cheers
Murdoch


middo

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Re: Coastal housing and sea level rise predictions
« Reply #1 on: May 29, 2021, 08:20:11 PM »
From the perspective of sea level rise, the 0.8m by 2100 is mostly in the latter half of the century, not the earlier half.  If you are only worried about up until 2050, I would no be concerned.  I would also keep an eye on progress of sea change, and erosion of the beach locally over the intervening years with a view to getting out when it may start to affect value. 

When will it affect the value?  That is a really difficult question because it is all about perception.

Personally, I am greatly concerned about seal level rise, and global warming.  I have a farm in an area that will become more arid and has already been a recent recipient of a cyclone, when the local regulations do not expect it to be a cyclone area.  I will ensure any future additions or repairs to the house and sheds are cyclone rated, so I cover my self.  I am also aware that water scarcity will be an issue.  But I am not prepared to sell it as I want it as a winter residence when we retire.

I guess what I am trying to say is if you plan to keep the place forever, then it is a concern.  If you plan to keep it only for 20 - 30 years, then I wouldn't worry.

mjr

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Re: Coastal housing and sea level rise predictions
« Reply #2 on: May 29, 2021, 11:50:57 PM »
81 cm in 90 years.  9mm/year.  Whereas the seas have been rising since well before climate change hysteria at a rate of significantly less than 3mm/year.

I am NOT concerned about global warming and sea level rises, it's all nonsense.  Flannery was quoted as suggesting a 6 metre rise in 30 years.  That and "our dams will never fill again". NASA's James Hansen prdeicted a 25 metre rise.  Flannery bought not one, but two, houses on the Hawkesbury.

Block still there in 20 years ?  Safe as houses.

deborah

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Re: Coastal housing and sea level rise predictions
« Reply #3 on: May 30, 2021, 12:15:40 AM »
I’d be more worried about cyclones (storm surge, flooding from high rainfall), which are increasing in that region. Especially when combined with king tides. When was the last time the place was flooded, or had a cyclone? What do insurance costs look like for water events?

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Re: Coastal housing and sea level rise predictions
« Reply #4 on: May 30, 2021, 12:24:01 AM »
81 cm in 90 years.  9mm/year.  Whereas the seas have been rising since well before climate change hysteria at a rate of significantly less than 3mm/year.

I am NOT concerned about global warming and sea level rises, it's all nonsense.  Flannery was quoted as suggesting a 6 metre rise in 30 years.  That and "our dams will never fill again". NASA's James Hansen prdeicted a 25 metre rise.  Flannery bought not one, but two, houses on the Hawkesbury.

Block still there in 20 years ?  Safe as houses.
It'll be interesting to see how well that post wears.

mjr

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Re: Coastal housing and sea level rise predictions
« Reply #5 on: May 30, 2021, 01:14:02 AM »
I’d be more worried about cyclones (storm surge, flooding from high rainfall), which are increasing in that region.

Looks to me like cyclone frequency and intensity is actually decreasing, according to the BOM

http://www.bom.gov.au/cyclone/climatology/trends.shtml
« Last Edit: May 30, 2021, 01:19:05 AM by mjr »

Model96

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Re: Coastal housing and sea level rise predictions
« Reply #6 on: May 30, 2021, 01:26:51 AM »
Ease your concerns by building a house that floats, like they do in Holland👍

deborah

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Re: Coastal housing and sea level rise predictions
« Reply #7 on: May 30, 2021, 03:57:01 AM »
I’d be more worried about cyclones (storm surge, flooding from high rainfall), which are increasing in that region.

Looks to me like cyclone frequency and intensity is actually decreasing, according to the BOM

http://www.bom.gov.au/cyclone/climatology/trends.shtml
Interesting article. Hedging bets each way. It says there was a redefinition of cyclones in 1979, and that may be contributing to the decline. However, the thing I read (wherever it was) said that there were a lot less cyclones in the period before 1948 than there have been since in Northern Queensland. Your article says...

Quote
...greater proportion of the high intensity storms (stronger wind speeds and heavier rainfall).

Wind speed is only one aspect of tropical cyclones and their impacts. The amount of heavy precipitation from all weather systems, including tropical cyclones, is likely to increase. Increased rainfall intensity from tropical cyclones is pertinent to Australia, since these storms have historically been associated with major flooding.

Additionally, increases in storm surges and extreme sea-levels are very likely to occur in association with tropical cyclones under future climate change. This change is independent of changes in tropical cyclone intensity and is directly related to increases in global mean sea-level due to global warming.

So it seems to say that the chances of flooding may be increasing.

norajean

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Re: Coastal housing and sea level rise predictions
« Reply #8 on: May 30, 2021, 07:03:41 AM »
Enjoy the house and don’t worry about things you can’t control. If sea level rises a bit, sell and move on.

mjr

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Re: Coastal housing and sea level rise predictions
« Reply #9 on: May 30, 2021, 01:08:31 PM »
"Is likely to increase" and "under future climate change".

Looks to me like weasel words from the BOM to try and obfuscate the obvious objective data in the graphic.  No doubt they rushed from this back to their task of homogenising temperature records to remove high past temperatures.

marty998

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Re: Coastal housing and sea level rise predictions
« Reply #10 on: June 05, 2021, 09:03:58 PM »
"Is likely to increase" and "under future climate change".

Looks to me like weasel words from the BOM to try and obfuscate the obvious objective data in the graphic.  No doubt they rushed from this back to their task of homogenising temperature records to remove high past temperatures.

Ugh. Do you really have to spew that nonsense?

mjr

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Re: Coastal housing and sea level rise predictions
« Reply #11 on: June 05, 2021, 10:35:16 PM »
That's your opinion, Marty, not mine.

Climate change hysteria leads to discussions like this one, councils and individuals being afraid that land will be under water in 20 years.  It's complete nonsense.

Personally, I pride myself on being an independent thinker and not following the herd and zeitgeist.  It'd sure be easier than being a conservative engineer in this day and age.
« Last Edit: June 05, 2021, 10:42:02 PM by mjr »

Fresh Bread

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Re: Coastal housing and sea level rise predictions
« Reply #12 on: June 06, 2021, 01:58:58 AM »
I used to work at an engineering firm and hmmmm it's more like "we've got this problem, what's the best solution?". Politics doesn't come up except when trying to get ahead of the others in responding to a change of government since the funding/agencies change.

I wouldn't build there because of storm surges, regardless of increased intensity. I live near Collaroy NSW.

ETA: maybe you could build a house that you can move to another block later!
« Last Edit: June 06, 2021, 02:00:31 AM by Fresh Bread »

middo

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Re: Coastal housing and sea level rise predictions
« Reply #13 on: June 06, 2021, 06:59:15 PM »
That's your opinion, Marty, not mine.

Climate change hysteria leads to discussions like this one, councils and individuals being afraid that land will be under water in 20 years.  It's complete nonsense.

Personally, I pride myself on being an independent thinker and not following the herd and zeitgeist.  It'd sure be easier than being a conservative engineer in this day and age.

I think you should be clear here.  Murdoch was not asking if his block would be underwater.  He asked:

Quote
My main hesitancy is whether the block will still be there in 20 years.

Storm surges and erosion of sandy beaches is nothing new around Australia.  Increased storm activity, changes to currents and sea level all play into how quickly sand is deposited or removed from a beach.  I'm pretty sure everyone who watched the houses in NSW try to fall into the ocean last winter knew they were not under water.  They were high above the water, but it doesn't stop the block ceasing to exist.


MrThatsDifferent

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Re: Coastal housing and sea level rise predictions
« Reply #14 on: June 06, 2021, 07:22:59 PM »
Unless a tsunami hits, you’ll see this coming and be able to get out before you’re  flooded. Don’t stress, live life.
« Last Edit: June 17, 2021, 05:51:18 PM by MrThatsDifferent »

Murdoch

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Re: Coastal housing and sea level rise predictions
« Reply #15 on: June 07, 2021, 05:04:16 AM »
Thanks all for the responses.

Despite its position and substrate structure it gets smashed by cyclones and storm surges almost annually.
Obviously it only takes one bad year to take out a whole region though.
Risk mitigation in the form of inshore reefs and the headland shape do mean it is fairly protected. The GBR offers great protection from large swell also (while it lasts).

The slow progression to any major sea level rise does put it into perspective a bit, so thanks for that take.
If it eventuates it's unlikely to be over 2-5 years, so there'll be more time than my fears probably considered.

We've asked the architects interested in the site to plan a minimum 1m elevation of the pad, or stump the lower floor up to this level to provide some breathing space from these events also.

Here's to hoping the fears don't come true, or if they do occur we have the solutions.

Cheers
Murdoch

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Re: Coastal housing and sea level rise predictions
« Reply #16 on: June 16, 2021, 02:03:47 AM »
It'd be interesting to get some insurance quotes.

No doubt that any risks that may apply to a beachfront block would be well and truly considered by any actuaries when calculating premiums :)

If storm surges or similar are a major problem in the near future, then that'll be reflected in insurability/insurance premiums.

I wonder if, for example, concrete stumps that are set into the ground and raising the house would provide a level of protection? I'm no engineer though :)

Bloop Bloop Reloaded

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Re: Coastal housing and sea level rise predictions
« Reply #17 on: June 26, 2021, 11:28:48 AM »
Climate change is kind of like covid. The scientists give out 'worst case scenario' quotes in order to try to spur us into action. I suspect the actual toll of climate change, just like covid, will be a lot less than the worst-case-scenario, since we are already onto it and taking action. Particularly with climate change we have a timeframe of decades to get there. Look how quickly petrol cars have fallen - in two decades (from about 2012 to 2032) we will have gone from 100% petrol cars to 0%. That shows how quickly things can change when they start to get dicey.

Just like covid, too, climate change is something that affects people disproportionately. The people who need to be most worried about climate change are not those in leafy suburbs of Melbourne/Sydney.

Murdoch

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Re: Coastal housing and sea level rise predictions
« Reply #18 on: June 26, 2021, 08:23:48 PM »
Thanks again all for the discussion.

At this stage we are going to sit on it as an investment property.
When we are closer to moving we will renovate rather than build and aim for comfortable rather than luxurious..
Will be approximately 1/4 the cost.

Cheers
Murdoch

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Re: Coastal housing and sea level rise predictions
« Reply #19 on: June 27, 2021, 01:03:10 AM »
I think that's wise.  Close to me there is a property that was completely rebuilt from a substandard 1930s version about 15 years ago.  It sold for about £1m to people who then got permission to completely rebuild it again at double the size.  The whole thing is in a lovely position by a beach, but the beach is eroding and the council policy is "no intervention" to stop the erosion: this is common around the UK coast for environmental and financial reasons: any money has to go on protecting only the most valuable and saveable settlements.  This property is, long term, gone, and anything spent on it in the meantime other than a bit of paint is a waste.

catprog

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Re: Coastal housing and sea level rise predictions
« Reply #20 on: July 18, 2021, 01:07:09 AM »
I think that's wise.  Close to me there is a property that was completely rebuilt from a substandard 1930s version about 15 years ago.  It sold for about £1m to people who then got permission to completely rebuild it again at double the size.  The whole thing is in a lovely position by a beach, but the beach is eroding and the council policy is "no intervention" to stop the erosion: this is common around the UK coast for environmental and financial reasons: any money has to go on protecting only the most valuable and saveable settlements.  This property is, long term, gone, and anything spent on it in the meantime other than a bit of paint is a waste.

And protecting this property could cause others to erode faster.

Linea_Norway

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Re: Coastal housing and sea level rise predictions
« Reply #21 on: July 18, 2021, 01:58:27 AM »
Climate change is kind of like covid. The scientists give out 'worst case scenario' quotes in order to try to spur us into action. I suspect the actual toll of climate change, just like covid, will be a lot less than the worst-case-scenario, since we are already onto it and taking action. Particularly with climate change we have a timeframe of decades to get there. Look how quickly petrol cars have fallen - in two decades (from about 2012 to 2032) we will have gone from 100% petrol cars to 0%. That shows how quickly things can change when they start to get dicey.

Just like covid, too, climate change is something that affects people disproportionately. The people who need to be most worried about climate change are not those in leafy suburbs of Melbourne/Sydney.

The IPCC climate report is a result of lots of negotiations among scientists and governments. They only publish the stuff that everyone agrees on. And that is more likely too conservative than too bold. I therefore think that reality might be worse than described in the report.

For the OP, you can expect the weather to become more extreme, rougher storms more often. So no, it should not be advisable to build a new home on a coast that already now is breaking off during storms.

On the other hand, about sea level rises, I heard a climate expert tell us on a podcast not to worry so much immediately. The predictions are indeed for 2100, which is still far away. Maybe your house won't even exist anymore by that time anyway.

I am myself a bit in doubt about what is wise. I would like to live in a house along the coast. But I would like some protection from the wind. And a bit of elevation to protect us from spring tide, which will be more frequent in the future.