2011 Brisbane rainfall dwarfed by 1974 figures

Just saw this snippet from the Courier Mail. Interesting that it runs against the torrent of “unprecedented event” style of reports that flood the media. Released on a holiday too. I liked the bit “The bureau stressed all data was not yet complete.”
What !! – two weeks with untold computing power – a century to get data in order – constantly pontificates in the media about what they know – and yet a little report on 10 or 12 days rain is not completed.
It is a huge no-brainer that Jan 1974 rain exceeded Jan 2011. Note the BoM coy way of putting it – “…what data the bureau has suggests 1893’s rainfall was extreme.” Feb 1893 rain might have exceeded Jan 1974 and 2011 combined.
I am puzzled they say “Insufficient data exists for a comprehensive assessment of the 1893 floods.” Looked to be plenty of stations recording – I think more a case of – no brownie points for going there.
Rainfall dwarfed by 1974 figures
* by Michael Madigan
* From: The Courier-Mail
* January 26, 2011 12:00AM

BRISBANE had more rainfall in the 1974 floods than it did in the latest episode, preliminary figures show.

And rainfall during the 1893 floods may have dwarfed both the 1974 and 2011 events.

The weather bureau on Tuesday unveiled rainfall comparisons suggesting the city falls were relatively light compared with ’74. But the inland falls that caused the flooding of the Brisbane River were extremely heavy.

The bureau stressed all data was not yet complete.

But weather experts suggested “peak rainfalls from the 1974 event were substantially heavier than those in 2011”.

Brisbane’s three-days and one-day totals were 600mm and 314mm in 1974, compared with 166mm and 110mm in 2011.

“However, in 1974 the heaviest rains were closer to the coast whereas in 2011 heavy rains spread further inland,” the bureau said.

Insufficient data exists for a comprehensive assessment of the 1893 floods.

But what data the bureau has suggests 1893’s rainfall was extreme.

Crohamhurst in the Glass House Mountains, inland from the Sunshine Coast, received 907mm on February 3, 1893.

That remains an Australian daily record.

9 thoughts on “2011 Brisbane rainfall dwarfed by 1974 figures”

  1. WSH,this C-M article is trash. If a headline makes a claim like “dwarfed” and backs it only by citing one station,Brisbane Met Office’s gauge,when we are really interested in the catchment-wide distributions,timings and totals,then we know,yet again,that the media are not up to the task of reasonable analysis.

    BOMS report on the 1974 event has a nice contour graphic of rainfalls for the five-day period of that flood. Clearly,the overall areal average-of limited value for determining the flood dynamics-is a little higher than Jan 2011. That does not support a headline using the word “dwarfed”.

    Clearly the areas around Mt Glorious,in the Oxley Creek and Warrill/Bremer headwaters over 5 days exceed this event over three days. However,one/two/three day amounts in critical parts of the Wivenhoe and Lockyer catchments match and often exceed same for ’74. A direct result that supports this is that the Lockyer@ Lyons Bridge exceeded 1974s peak figure by over 60cm. The western parts of the upper Brisbane stream network received more rain over five days than did the crucial five for 1974,and the Stanley catchment figures I’ve put together give 600-800mm for both floods over their critical periods [ 5 days for 1974,and 4 days for 2011]

    Here are a couple of interesting comparative stats for 1974 and 2011:

    Crows Nest PO: totals for preceding month and flood month to end of flood rain event for Dec 1973/Jan 1974 135mm + 515mm to 28/1/74 [59 days]

    Totals for Dec 2010/Jan 2011 307mm + 468mm to 12/1/11 [43 days]

    Peachester: Dec 73/Jan 74 175mm + 1177mm to 28/1/74 [59 days]

    Totals for Dec 10/Jan 11 529mm + 885mm to 12/1/11 [43 days]

    Peachester 24-28/1/74 total 709mm for five days, and 9-12/1/2011 total 741mm for four days.

    I cannot explain why the media is incapable of a little curiosity about comparing events of such significance.

  2. The CM says “The weather bureau on Tuesday unveiled rainfall comparisons…”
    I have looked for these on the BoM site – to no avail. But will keep looking – if anybody finds what was “unveiled” – please pass on.

  3. Helps to realise that journalists are only employed to fill the empty spaces between the advertisements, and that “exciting” leaders are there to make your eyes wander over the advertisements. They can’t afford to hire journalists for investigative reporting. If the UK Guardian did not have the BBC advertising, it would probably fall over into bankruptcy.

  4. WSH,I think the “unveiled comparisons” were in a revision [25/1] to Special Climate Statement 24.

  5. The BOM Radar showed massive falls between Brisbane and Wivenhoe with most not captured by the dam. In the middle of the summer day the sky over Brisbane was as dark as under a thunderstorm, it was like that for 2 days.
    In 1974 Brisbane got most of the rain, in 2011 it was west of us and on our side of the dam.
    Does anyone know how long it takes massive Wivenhoe outflows to reach Brisbane. An Engineer has suggested 24-36 hours, this seems believable for regular small outflows, do they know the figure for catastrophic flows?
    At Jindalee the river was always flowing one way and at about 25 knots, so 2 hours seems more probable.
    It seems to me that there are 2 possibilities for the flooding:
    1. The rain flooded Brisbane and the Wivenhoe outflows slowed the retreat of the water.
    2. The outflows caused 80% of the flooding as an Engineer suggested.

  6. If the Government can show Wivenhoe outflows take 24-36 hours to reach Brisbane as an Engineer suggested then the massive release must have arrived after normal river flooding from the intense rainfall.
    Why doesn’t the Government answer this question now?

  7. I did a back of the envelope calculation for the 4 major floods – 1893 (1) 1893(2) 1974 and 2011. The 1893 floods consisted of two major floods separated by 10 days. I looked at the data for the 6 sub-catchments of the Brisbane River and calculated a total for the whole catchment. I used the BOM Report on the 1974 Flood (p29-30), which gave me data for the 1974 and the two 1893 floods, and the DERM (SEQWater) Report on the 2011 Flood (p73,123), which gave me data on the 1974 and 2011 floods.
    Because of differences I couldn’t do a straight comparison but I assumed that if in the BOM Report Event A was greater than event B and in the DERM Report event B was greater than event C, then event A was greater than event C!
    My conclusions, in the form of rankings of volume of rainfall calculated by multiplying the area by the average rainfall for each sub-catchment :-
    Overall, 1974 flood (5600gl) was greater than 2011 flood (5400gl) which was greater than 1893(1)(5200gl) which was greater than 1893(2) (4300gl).Given the margin of error, 2011 and 1893(1) are comparable.
    1974 saw the greatest volume of rainfall in the Bremer, Lockyer and Lower sub-catchments. The 1974 rainfall in the Lower sub-catchment defined the 1974 flood with consecutive days of 200mm falls which resulted in flash flooding and flooding from local creeks. In the Somerset and Wivenhoe sub-catchments it ranked third.
    Interestingly, 1893(1) which had third overall ranking, came first in the Somerset and Wivenhoe sub-catchments. It was predominately an “Upper sub-catchment” flood whereas its sister, the 1893(2) was a Lower sub-catchment flood.
    The 2011 flood came in second overall and second in all the other sub-catchments except the Lower where it came in third behind 1893(2).
    Ironically, Wivenhoe Dam was built in reaction to the “Lower sub-catchment” 1974 flood which it would have been powerless to mitigate!!!
    Comparing 2011 with 1974 in the Lower sub-catchment we get ~400gl vs ~800gl.

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