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Whole suburbs flooded after exhaustive expert flood modelling says they won’t

Posted By Jo Nova On February 7, 2019 @ 3:09 am In Global Warming | Comments Disabled

Another triumph of modeling

In 2014, Townsville City Council launched a detailed flood mapping service.

The maps will allow people to search individual properties to find out the risk of it being inundated during a one-in-100-year flood event.

Five years later and they’re publishing inundation maps. Sadly, new suburbs were built with the wrong expectations.

 Townsville flood maps reviewed as more homes go under

Jared Owens and Charlie Peel The Australian

Townsville City Council’s spokeswoman said last night the model, which was based on expert modelling of different scenarios, was overwhelmed by an “unprecedented” monsoonal trough …

Local Government Associa­tion of Queensland chief executive Greg Hallam said Towns­ville’s flood maps relied on “exhaustive modelling of every possible scenario”, looking at variable­s such as rainfall and artificia­l structures.

“We’re not God. We don’t have supreme knowledge. We only have the best science, the best knowledge we can have,” he said. “We now know with the (dam) gates fully open … what will flood and what won’t, so there will be a new set of flood maps prod­uced out of this event.”

If we had better climate models, perhaps we might have been able to empty the dam before the downpour instead of during it. (Though I’ve yet to see any data on dam levels yet, so perhaps not. Wait and see.).

The Local Government Guru must be flummoxed. He (Hallam) even protests they used the “Monte Carlo” risk analysis “as recommen­d­ed in 2012 by experts.” What could possibly go wrong?

How about basing a $1.5Trillion dollar global industry, agriculture, energy generation and national wealth on models one hundred times more complex which also use a “Monte Carlo” analysis.”

Another ugly lesson:

Beware, people who followed the expert advice have no legal recourse to get compensation if they’ve just “discovered” it was built on a floodplain instead.

In the global warming parallel universe there won’t be compensation: no climate modeler could even afford to pay back 0.1% of the damage created by those expert predictions.

Here’s a house constructed without expert models

Queenslander House

A Queenslander house.  Image NJM2010

Inhabitants from the slide-rule-era built a kind of house on stilts that suited both droughts and flooding rains.

It was so common, it was known as a “Queenslander”. After the Brisbane floods the ABC even featured an article lamenting the lost art of the old architecture: “Have we forgotten to build for the wet“?

For those from foreign lands, Brisbane is also in Queensland, but is 1,300km south of Townsville, outside the tropics, yet still prone to droughts and floods too.

Best wishes to those suffering at the hands of monsoons and or models.

 

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UPDATE: The Ross River Dam was 65% full before the downpour. This is not the same situation as the Wivenhoe Dam disaster near Brisbane. h/t Jonesy  (I note Townsville is currently under Level 2 water restrictions. :-) Don’t use your sprinklers on the wrong day!)

Martin Clark: The State Govt forces councils to plan for the UN IPCC RCP 8.5 (worst case “global warming” scenario).

This has been an exceptional event, but it is NOT unprecedented. There is a swale at the rear of my property. I have a marker placed at the level where the 1998 flood reached. The flood water has gone way past this marker four times in the last 6 days.

The flood mapping may be partly based on expert engineering analysis, but the provisions are augmented by the lunatic projections of the UN IPCC’s RCP 8.5. This is called up in the State Planning Policy, so it MUST be incorporated in local planning provisions. This has resulted in some ridiculous requirements. I objected to RCP 8.5 being included in the SPP. Much to my surprise, it was removed, but was then put back in by the current regime. It is a distraction that can’t happen, but diverts attention from events that can happen.
There are areas downstream of the Ross Dam that have flooded many times before, and will flood again. In this respect, Townsville is better than many towns and cities on the eastern seaboard, in that it is built at the estuary of rivers that have a limited catchment, not the 1/2 million km2 that applies to many other places. However, stuff that has been approved and constructed under the post-2014 provisions has gone under. Bunnings at Idalia went under by a whole metre.

The ’98 flood was the result of a spent cyclone sitting over the city for about 24 hours. This has been a monsoon trough that has stayed almost stationary for 6 days. “Australian Rainfall and Runoff” does not adequately cover events that don’t move.

Up until quite recently, “monsoonal” weather was regarded as something that only applied to India and SE Asia. As far as we know, monsoon troughs don’t go round for a second go like cyclones sometimes do. We hope.

The only solution is to design for this type of phenomenon and where cost-effective, refit existing development to be recoverable. The money we waste on ruinable energy needs to be spent on real problems. “100 year” events? More like “100 week” events.

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