Turning houses into boats...???

[Buzzook]

OK, be gentle, not an engineer. Only a gorblimey chippie, by trade...so understand nothing...much...but am aware that climate change effects are becoming more visible and more regular, leading to a greater than historic frequency of repeat inundations in riverine and coastal environments.

What I'd like to understand is whether or not it might be feasible to turn 'lightweight timber structures' like older-style timber framed, timber-clad dwellings, into 'houseboats' as a means of avoiding repetitive flood inundation (as per Lismore NSW in recent years).

As a boat owner, and marina user occasionally, I'm familiar with the modern 'marina construction' methodology of driven piles and floating pontoons.

Would it be possible to place similar driven piles (maybe vibration driven) around such dwellings, jack them up, add floatation chambers to the sub-structure (possibly even add a RHS steel sub-structure to prevent twisting), and attach 'rollers' at the pile attachment points, to enable such homes to simply *rise and fall* with the floodwaters..?

OK, so I know my thumbnail sketch is a massive over-simplification of what would need to occur to make this work but....could it work...??

My best guess on house mass is between 4-10 tonnes. So would 4000-10000L of buoyancy be enough to float that...??? Even if double that was necessary, a 1.0m X 1.0m X 10m rotomoulded floatation chamber would contain 10,000L, so two of them, either side of the dwelling...?? [This is wet thumb in the breeze guesswork, so probably hopelessly inadequate...]

I'm not even remotely close to being a mathematician, so cannot hazard more than a guess at whether this might even be possible, so am wondering if there are engineers here willing to respond - kindly - and without scoffing *too* loudly at my 'below the salt' hypothesis....????

It seems to me, from the $$$numbers various agencies have been floating about, that there is a LOT of expenditure on new, greenfields land, and new-built housing to 'replace' so-called flood-affected housing. Maybe $500-800K per dwelling. What might the 'cost per pile' be for, let's say, 500mm diameter 10m long R/C driven piles...?? Especially if, as seems to be the case, there could be a lot of 'ongoing work' in localised areas, enabling some degree of 'scale' to be factored in.

I'm wondering whether there is enough in that to interest a piling engineering firm to perhaps investigate the feasability of 'floating the boat' rather than removing the dwelling and destroying the existing community....??

I mean, thousands of homes along every river and coastline....with a successfully designed 'floatation system' potentially being a 'development condition' for future dwellings in flood-risk areas.....

There's certainly, I think, some potential there, if someone could work out a cost-effective 'system'...??

Now, I'll just don my flame-proof overalls, and duck behind this heatshield......

Anyone care to enlighten me? Politely? Tx in advance.

 

[GregLocock]

I asked chatgpt

"Please find references for the following statements:the seismic plate that forms the USA is tipping, and local actions such as dredging, building cities, and groundwater extraction all affect local sea levels vastly more than the thermal expansion of seawater and melting ice. The mean sea level is measured relative to the average geoid"

It complied.

 

[XR250]

@XR250 yes of course I have references.I suggest google will help you once you have well formed questions.

Ok, What I am finding is that seismic plate tipping is unlikely to be affecting North Carolina.
Subsidence is part of it though, but so is sea level rise.

 

[TugboatEng]

Surely we can quantify how much of a part each of those two factors are?

 

[XR250]

Thank you ChatGPT...

 

[TugboatEng]

That's interesting that the sea level rise and subsidence changes are nearly identical. Most sea level rise studies don't even mention subsidence so I doubt it's accounted for. In that case, nearly all of the sea level rise may actually be subsidence.

 

[TugboatEng]

XR250, it looks like ChatGPT is using gauge sea level and adding it to subsidence. Gauge sea level already includes subsidence meaning their measurements essentially double the actual climate change caused sea level rise.

Here is what Grok says, note that Grok made the same error and corrected it after further questions.

"The sea level rise rates provided in my first answer for North Carolina (3.6–4.5 mm/year, or 0.14–0.18 inches/year, with some areas seeing up to 0.5 inches/year since 2010) represent relative sea level rise (RSLR), which includes the combined effects of:
Absolute sea level rise (global ocean level increase due to melting ice and thermal expansion).
Land subsidence (sinking of the land due to geological and human-induced factors).
Clarification:
Relative Sea Level Rise (RSLR): This is what tide gauges measure and reflects the net change in sea level relative to the land. In North Carolina, RSLR is higher than the global average (~3.7 mm/year) because subsidence adds to the global rise.
Subsidence Contribution: As noted in my second answer, subsidence in North Carolina averages 1.4 mm/year (up to 4 mm/year in northeastern areas). For example, in Wilmington, the RSLR is 3.59 mm/year, of which ~1.4 mm/year (about 40%) is due to subsidence, leaving ~2.2 mm/year from absolute sea level rise.
Breakdown Example:
Wilmington: RSLR = 3.59 mm/year = (Absolute rise ~2.2 mm/year) + (Subsidence ~1.4 mm/year).
Northeastern NC: RSLR = 4.5 mm/year = (Absolute rise ~2–2.5 mm/year) + (Subsidence ~2–4 mm/year).
Why This Matters:
The rates in my first answer are from tide gauge data (e.g., Virginia Institute of Marine Science, 2024), which inherently capture both components. If you were asking for absolute sea level rise (excluding subsidence), the rate would be lower, closer to the global average of ~2–2.5 mm/year in North Carolina, depending on the location.
Subsidence significantly amplifies flood risk, as it effectively doubles the impact of sea level rise in some areas (e.g., northeastern NC).
Answer:
The sea level rise rates in my first answer (3.6–4.5 mm/year) are relative sea level rise rates and include subsidence. Subsidence contributes 1.4–4 mm/year (0.06–0.16 inches/year), with the remainder (~2–2.5 mm/year) from absolute sea level rise. If you want the absolute rise (excluding subsidence) for a specific area or further details, let me know!"

 

[XR250]

Thanks TBE.