Yesterday, 2nd March, ABC weather reporter Kate Doyle posed this question on the ABC website about the recent rain event in SE Queensland and Northern NSW.
Her answer to the above question was:
“Very unusual.
The rainfall totals from this event have been staggering.
From 9am Thursday to 9am Monday three stations recorded over a metre of rain:
– 1637mm at Mount Glorious, QLD
– 1180mm at Pomona, QLD
– 1094mm at Bracken Ridge “
She goes on to say: “South-east Queensland and northern NSW are historically flood prone and have certainly flooded before but this event is definitely different from those we have seen in the past.” And of course climate change is involved.
Time for a reality check.
My answer to Kate’s question: Not very unusual at all.
I went looking at Climate Data Online for four day rainfall totals over one metre, to compare with the recent totals above at Mount Glorious, Pomona, and Bracken Ridge.
For a start, Pomona’s BOM station has been closed for years, and Bracken Ridge is not listed at all, so those reports are from rain gauges external to the BOM network and can’t be checked.
That’s OK. In about half an hour I found the following four day rainfall records.
| Crohamhurst | 4/2/1893 | 1963.6mm |
| Yandina | 3/2/1893 | 1597.8mm |
| Tully Sugar Mill | 13/02/1927 | 1421.3mm |
| Palmwoods | 4/2/1893 | 1244.6mm |
| Buderim | 3/2/1893 | 1150.3mm |
| Bloomsbury | 20/01/1970 | 1141.8mm |
| Dalrymple Heights | 6/04/1989 | 1141mm |
| Innisfail | 3/04/1911 | 1075.8mm |
| Nambour | 11/1/1898 | 1013mm |
1893 was a wet year! Crohamhurst had 2023.8 in five days, and Brisbane had three floods in two weeks in February and another in June.
And there is no such thing as a “rain bomb”, a term invented to make it sound unprecedented. This was an entirely natural and normal rain event. Slow moving tropical lows drift south every few years in the wet season, producing a large proportion of Queensland’s average rainfall.
Floods have affected Brisbane and surrounds since before European settlement. The Bureau has an excellent compilation of accounts of past floods at
http://www.bom.gov.au/qld/flood/fld_history/brisbane_history.shtml
It includes this graphic showing the height of known floods. I have added an indication of the height of the 2022 flood.
Here are some notable Brisbane floods:
1825 a flood probably as high as the 1893 flood
1841 8.43m
1844 about1.2 metres lower than 1841
1864 ?
1887 ?
1889 ?
1890 ?
1893 8.35m
“ 8.09m
“ ?
“ ?
1908 4.48m
1974 5.45m
2011 4.46m
2022 3.85m
Every flood is different- water backs up higher in unexpected places, or gets away faster, so for many people this flood was worse than 2011. However it is beyond any doubt that this flood, heartbreaking as it was for many people, could have been much worse. It was nowhere near as big as several in the past. Wivenhoe Dam worked as planned this time, which greatly lessened the impact.
Another thing worth remembering: floods were more frequent and higher in the 19th Century than they have been in the last 100 years.
ABC journalists need to do a lot more research.
Tags: climate, floods, Queensland, Rainfall
kenskingdom 
March 3, 2022 at 3:40 pm
Great post Ken. I will use this when I am on the radio. Crohamhurst in fact has the one day record on 3/2/1893 with 907mm or just over 36″.
In addition the East Coast of Australia particularly the Hunter Valley flooded every year from 1949 to 1955 with 1955 being the big one with some parts of the Hunter Valley recording 11″ or 275mm.
The issue is not the floods but, as with droughts and bushfires, the lack or preparation and infrastructure, or in the case of Wivenhoe and Warragamba, infrastructure being used incorrectly based on alarmist predictions. Warragamba is also facing the usual green opposition to its proposed height increase.
March 3, 2022 at 5:01 pm
Thanks Ken.
March 3, 2022 at 6:29 pm
Thanks for your detailed report.
Have shared it to a few sites.
March 3, 2022 at 9:14 pm
Thank you, Ken. That is exactly what I told an enquiry in 2011, but also pointed to the misuse of Wivenhoe, which is a flood mitigation dam and never to be used as an urban water supply first.
March 4, 2022 at 6:21 am
[…] There have always been big floods in Brisbane | BOM Source | KensKingdom […]
March 4, 2022 at 9:04 am
B*****t detection from fact-cherry-picking non-scientific Ken Stewart
• Yes slow moving low system are possible for making rainfalls as big as this year in history, not denied
• in the 1800’s the majors rivers like Brisbane River, Hunter River, etcs were 1/3rd of the width and 1/10th of the flow. In the 1800’s flood plains were very extensive and slowed water moving downstream, and the 1800’s rainfall would take “weeks to reach the sea” compared to “a few days” nowadays.
• less floods in last 100 years may be due to dredged river and man made stormwater drains, and drained swamps so you can’t correlate to CO2
• The use of one piece of data to then hypothesis that CO2 is not a factor in a multi-variable scientific analysis, is an unscientific myopia of troglodytes
• I can cherry pick some counter facts too, like for every one degree increase in air temp the air holds 3-5% more water in the clouds based on laws of thermodynamics which then can fall at twice the rate to earth – refer https://www.engineeringtoolbox.com/maximum-moisture-content-air-d_1403.html
March 4, 2022 at 10:47 am
An amazing comment. What evidence do you have for rivers being “1/3rd of the width and 1/10th of the flow” in the 1800s, and rain would take weeks to reach the sea? That’s a first for me and sounds like hand waving to me. Flood plains have not changed in size but in the 1800s were much clearer grassy flats, whereas now they’re covered in houses and buildings which act as dams. Dredging certainly will allow water to drain away faster, but stormwater drains have no effect on riverine flooding, and swamps have been filled for sure, but that will counteract the effect of dredging. And what exactly am I correlating with CO2? And what hypothesis? First I’ve heard of it. A warmer atmosphere should hold more water vapour for sure, so floods should be higher and more frequent now. Now, about cherry picking. I’m not the one picking cherries. That was done by the ABC reporter using ONE data point (the recent rains) to claim it was different from before, without comparing with previous rain events and floods, which is what I’ve done.
Over to you.
March 4, 2022 at 4:57 pm
The Clausius-Clapeyron relationship which defines the capacity of warm air to hold moisture is a POTENTIAL capacity. One of the many errors the GCMs make is they assume the full potential of the CC relationship when observational evidence shows this not to be the case; see Kininmonth: https://www.lavoisier.com.au/articles/greenhouse-science/climate-change/kininmonth-Clausius-Clapeyron.pdf
The other factor is of course the increase in CO2 is mainly natural: https://journals.lww.com/health-physics/Fulltext/2022/02000/World_Atmospheric_CO2,_Its_14C_Specific_Activity,.2.aspx
The fact is these recent floods are NOT unusual and given we are now in a -ve or cool, La Nina dominated PDO we can expect more of them. What is needed is more flood mitigation infrastructure and use of existing infrastructure as flood mitigators rather then drought mitigators which when Wivenhoe did this in 2010 cost the Australian taxpayer over $400 million in damages.
But of course the greens oppose this.
March 4, 2022 at 8:24 pm
1893 heavy floods, 1896 massive heatwave. Is there a cycle? Could we be in for a stink9ing hot summer in the next four years?
March 5, 2022 at 5:20 am
It’s a stinking hot summer in in central and north Qld right now.
March 4, 2022 at 8:50 pm
Great job here Ken. Thanks so much for your work!
March 23, 2022 at 5:07 pm
[…] floods. Brisbane was hit hard by floods last month. Figure 1 is from a previous post, showing historic floods in the Brisbane River with the 2022 flood inserted. No cause for alarm […]