Australian Floods


APRIL 6, 2021tags: Australia

By Paul Homewood

Floods in Australia made big news last month, (Click on link to watch video):


The floods mainly affected NSW and SE Queensland. The video talks of “less than 1%” chance of this amount of rainfall occurring. But the BOM figures don’t support this claim.

In NSW, although it was the second wettest March, it was considerably wetter in 1956. Moreover it was not particularly wet in February, so the ground would not have been saturated.

March Rainfall - Total for New South Wales/ACT
February Rainfall - Anomaly for New South Wales/ACT

March of course is only one month. Last month 136mm fell in NSW, but this amount is not unusual when all months are taken into account. Indeed it would appear that extreme rainfall months were more common in the past:


The BOM published a summary last week, which highlights various daily and monthly records set at some locations, but again these are only for March. None of this supports the allegation of a 1 in 100 year event. Instead it was just an unusual and localised occurrence for the month of March.


As the video points out, Australia is a land of flood and drought:

I mentioned March 1956, but that year it barely stopped raining from February to May, which led to the worst flooding in NSW, Victoria and South Australia since 1870. This truly was an epic event, and was accurately described as a 1 in 100 year occurrence. This year’s floods don’t go anywhere near approaching 1956, as the following video vividly shows.

It is 16 minutes long, but I would thoroughly recommend watching it. It not only gives an idea just how bad the flooding was, but also offers an insight into life in those days. Below it is a short film, which also shows how widespread the flooding was. 

Towards the end, you will see a reference to the floods of 1870, which by all accounts were even worse.

The term 1 in 100 year event is regularly abused nowadays, and is invariably used to describe what are no more than common weather events. Scientists doing this belittle the truly epic events of the past.

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April 7, 2021 6:32 am

A “1 in 100 year event” is a civil engineering requirement planning term that attempts to statistically predict the future from sparse data, out of that specific context it is a prime example of the misuse of an inherently faulty model.

Reply to  dk_
April 7, 2021 10:39 am

Ahhh, another PIOOTA) number?
(pulled it out of their arses)

Reply to  Mr.
April 7, 2021 11:43 am

No, it is a quite serious and useful engineering tool for determining the cost of a project. No one would pay for something even 10% better. But it is a guess, subject to multi-dimensions of error, and useless outside of the engineering context, espectially destructive in the political and journalism venues.

Last edited 15 days ago by dk_
Reply to  dk_
April 7, 2021 1:35 pm

Well said, dk !

Reply to  dk_
April 7, 2021 1:39 pm

I was referring to the useless outside of the engineering context, espectially destructive in the political and journalism venues” usage.

Reply to  Mr.
April 7, 2021 1:48 pm

No, it is based purely on past data usually using a Log Pearson 3 plot with error bands…

Trouble is that in Australia data may not be much longer that 100 years, leading to large error bands as you get to rarer events


comment image

Michael Jankowski
Reply to  fred250
April 7, 2021 3:30 pm

Past data is the basis, but there are some who apply “climate change adjustments.” Random presentation here PowerPoint Presentation (

Reply to  Michael Jankowski
April 7, 2021 5:40 pm

Nice graphs but no numbers

Reply to  dk_
April 7, 2021 1:42 pm

I wonder if they are using the old ARR descriptors, or the ones that came out a a couple of years ago.

From comments I have heard, these larger events occur more often in the new ARR, because they take into account the phase of the PDO and ENSO that affect the east coast weather so much.

Maybe one day I will read the whole of the new ARR….. or not.!

Reply to  fred250
April 7, 2021 8:03 pm

The new Australian Rainfall and Runoff ARR guide states that impacts from climate change are inclusive and vary from place to place, but recommends engineers design for an 10% increase in peak rainfall.

To meet this 10% increase would increase the cost of drainage infrastructure by about 1%
Drainage infrastructure is generally less than 10% of a communities civil infrastructure.
The EXTRA impacts of flooding due to supposed climate change is a non problem.

BTW civil engineers don’t work with 10% safety margins

Bruce Cobb
April 7, 2021 6:32 am

Hurricanes tornadoes, and trees turned to ashes,
Big floods and long droughts causing no more green grasses
Dying fish and corals making kids cry
You know what comes next – WE’RE ALL GONNA DIE!

Reply to  Bruce Cobb
April 7, 2021 11:49 am


Well, that bits correct … some sooner than others …but ALL are GONNA DIE.

M Courtney
April 7, 2021 7:15 am

Sounds like a 1 in an 80 years event.
Considering the fact that they don’t come around like clockwork, one in a hundred years isn’t too far out.

Ron Long
April 7, 2021 7:17 am

Another case of weather being reported as climate (change). Droughts and floods, oh my, why can’t it just deliver the average amount of rainfall every year? And who is “it”?

Reply to  Ron Long
April 7, 2021 11:40 am

Climate change can only happen when the weather changes first. Cause and effect. To fight climate change, one must first fight weather change. Good luck with that.

Kevin kilty
April 7, 2021 7:19 am

I agree with “dk_” above who has said that the term 100 year event is out of context and highly misleading.

By 100 year event we mean an event of a size that we might expect it to occur with probability of 0.01 in a given year. It could occur twice or not at all, or even more than twice. What we are really interested in is how much we have to fortify a structure, or size a dam, to be confident to some level of certainty that the structure won’t be topped once in some lifetime.

So, for example, if we would like to be 90% certain that a structure won’t be topped in a ten year interval, then we have to build to an event whose return interval is 9.52 times 10 years — a 95.2 year event, if you will. Or to be 95% certain we have to build to an event with a return interval 10 years times 19.57 — the 195.7 year event. If one uses the event with a return interval of 10 years to design a structure it has a risk of about 63% of being topped at least once in ten years.

These floods! They don’t behave like we expected! Must be climate change….

Reply to  Kevin kilty
April 7, 2021 8:51 am

Any prediction of future events is scientifically faulty. Entropy works in one direction, regardless of the math and language we use to try to describe it. To claim that the present doesn’t match a prediction is to state the obvious. To use that claim to obtain political, social, or economic power is fraudulent. To use the claim to create fear is terrorism.

Reply to  Kevin kilty
April 7, 2021 9:17 am

In Las Vegas, Nevada, we used 100 year event to size roof and area drainage for buildings. The number is 3 inches/hour. We average around 4 inches per year, but localized storms often deliver at the 3 inches per hour rate for 15 minutes or more. The piping (primary and secondary) EACH must be sized to for the volume of flow created by the 3 inch/hour rate. Of course, with the secondary drain required, an actual 6 inches per hour could be handled, providing nothing plugs up the drains. There have been roof failures on large commercial buildings on rare occasions due to plugged drains.

As to the 100 year floods. We have, again localized, 100 year flood events pretty often. Just not for the whole valley. I have heard it said that if the whole valley got 100 year rain at the same time, it would be a 1000 year event. With the shape of the valley, a bowl with one outlet, the flow in the Las Vegas wash would be incredible. When you visit Reed Rock canyon and see a 30 foot cube of sandstone more than a quarter of a mile from where it separated from the mountain, you can see high rainfall events have happened in the past.

Reply to  Drake
April 7, 2021 4:51 pm

excellent example

Joel O’Bryan
April 7, 2021 7:27 am

The Left with just about everything now has politicized everything and has adopted the motto, “If we aren’t lyin’, then we aren’t tryin’.”
From weather as climate, and now COVID to control of the people, It’s pretty much lying 24/7 now on their quest to power.

Reply to  Joel O’Bryan
April 7, 2021 8:12 am

Yeah, if you follow, as I do, the COVID-19 infection rate in the Bay Area, where I live it has now flatlined, even though over 30% of the population has had at least one vaccine shot.

So that leaves a scientist with a puzzle in understanding the data; either there is (a), a scientific explanation or (b) the demo-Rats are up to something again.

Since, as you correctly pointed out, the demo-Rats are up to something involving lying 24/7, I’m leaning towards the latter explanation

Joel O’Bryan
Reply to  philincalifornia
April 7, 2021 8:28 am

Be interesting to see if Gov Nuisance survives his recall. I figure he is banking on Cal’s democrat ballot harvesting machine to save his sorry butt this November.

Demo-rat leadership has figured Florida Gov DeSantis is a real, serious threat to take the WH in 2024 from the unlikable Kamala Harris. Thus they tasked 60 Minutes to do the dishonest hit piece last Sunday on DeSantis. Expect more hit pieces and reputation smears on Gov DeSantis as his performance with managing Florida thru the COVID epidemic shredded the Dem’s narrative on masks and economy destroying lockdowns.

Last edited 15 days ago by joelobryan
Abolition Man
Reply to  philincalifornia
April 7, 2021 8:31 am

Keeping the borders open so that immigrants infected with the Brazilian variant can be widely dispersed around the country, the DemoKKKrats will be claiming all need a new and improved vaccine or you’re raaaacist in 3, 2, 1…
The great thing about the Fauxi virus is you can keep altering it slightly to target the intended victims and many of them will docilely acquiesce to the bio-warfare!

Joseph Z
April 7, 2021 7:28 am

1 in 100 means that after an event the next event has about a 1 in 3 chance of occurring in the next 40 year, 1 in 3 chance of occurring in 41 to 100 years and 1 in 3 chance of not occurring again for over 100 years.

Michael Jankowski
Reply to  Joseph Z
April 7, 2021 6:37 pm

1 in 100 means it has a 1 in 3 chance of occurring over 33 years (and 2 in 3 chance it doesn’t). Doesn’t matter if it is “after an event” or if there has been a 100 year drought of events. They are independent events.

Flipping a coin should be 1 in 2 heads and 1 in 2 tails over the long-haul. But if you flip tails once or even 10 times in a row, the probability of next flip is still 1 in 2 heads and 1 in 2 tails.

April 7, 2021 8:58 am

Statistics are such fickle thing’s, 1 in 100 yrs, Where for a start. Recorded by whom, over what time frame ? Over thirty years in our current location we have been flooded in (IE: Unable to traverse the local roadway”safely” ) five times at this time of year in FNQ, the last time was this time last year.
It is all relative to your local area FFS. In Aus the Rain Never Falls Mainly on the Plain… It is mostly all Arse over Tit and Fall’s wherever the Hell it want’s.
BOM have passed predictions off to Computer’s which are no better or worse than Humans given the current crop of Graduates that passed the last decade of “Candidate Selection” based upon far less than Meritocracy Standards.
Just Sayin….

Pat from Kerbob
April 7, 2021 9:50 am

Media, which includes many climate scientology groups, have learned sales concepts like needing “$100 words” in order to sell something.
Calgary had a big flood in June 2013, shamelessly plugged as a 1 in 500 year event.
Later that year there was an item in the Calgary Herald regarding a University of Calgary study that showed this event was actually only the 5th highest water level in the Bow River basin in the previous 130 years.

Lies are endless

Last edited 15 days ago by Pat from Kerbob
Climate believer
April 7, 2021 9:53 am

Don’t know which is worse, they could be living between 1880-86, experiencing one of Australia’s national devastating droughts.

In New South Wales alone it is estimated that 9 million sheep died during this period.

CO² levels at the time under 300ppm.

April 7, 2021 9:54 am

The weather event as big as two European countries

As ever the BBC likes to be more than vague. There are a total of 44 countries in Europe. The smallest of these is Vatican City, which is roughly 0.44 km2 in size.

It just so happens that Russia is the largest country in Europe by land area. 

I wonder which two European countries the Beeb had in mind?

It’s a ridiculous metric, either way. It follows that any claims made in the article are to be ignored.

It Is The Propaganda Service, after all.

Last edited 15 days ago by fretslider
Pat from Kerbob
Reply to  fretslider
April 7, 2021 10:55 am

I choose Andorra and Monaco.
No emergency as the flood is 12 square city blocks.

Its like GM advertising a truck getting 900km to a tank of gas. Great, but the truck could have a 1000liter tank built in, in which case oops.

So much garbage in this world. and people say we are the problem, not trusting media.

Reply to  fretslider
April 7, 2021 12:45 pm

The Baghdad Bob Corporation

As an ex_pat, I don’t know which is funnier – being forced to pay the BBC to lie to you, or for Canadians to want their country to be colder – some Canadians that is.

Reply to  fretslider
April 7, 2021 1:52 pm

The weather event….”


Australia has had large rainfall events in the past.

And will have again in the future.

April 7, 2021 9:59 am

Note to government of Australia: more dams. You’re welcome.

April 7, 2021 10:32 am

comment image

A look at the picture shows, rain at Ayers Rock is at least not unusual,
the water often flows down to give the rock it’s structure with these gullies.

Fresh water
April 7, 2021 12:16 pm

I suspect it calculated by fitting a frequency distribution to the data e.g. an expected distribution (gumbel, log Pearson, extreme value etc…) not based on the actual frequency. The curve you pick can make a big difference to the answer. I get asked to make such proclamations, but try to avoid that discussion and simply say it is the x largest in the xxx year record.

It is also more complicated when your talking about one rain gauge or many

Last edited 15 days ago by Fresh water
Reply to  Fresh water
April 7, 2021 1:53 pm

see example near top of standard method using LP3 fit.

or read all about it here

Last edited 15 days ago by fred250
Michael Jankowski
April 7, 2021 3:25 pm

1 in 100 year event has a 1% chance of happening in any year…10% change of happening every 10 years…50% chance of happening in the next 50 years.

Rainfall events get tricky…do you base it off just one rain gauge? A minimum area of coverage? And there is a 1 in 100 year event for any rainfall duration. You can have a 1 in 100 year 15 minute rainfall one day and a 24 hour rainfall on another. There are more 1 in 100 year events than you can shake a stick at.

Flooding events are also tricky. Data for undisturbed land is one thing. Development upstream means loaded dice.

Reply to  Michael Jankowski
April 7, 2021 4:26 pm

along with dk you have provided the best description of the relevance of the “1 in 100” rainfall event. But it is still more involved.
I can watch a storm front on BOM Radar slowly cross Melbourne.
the multiple coloured blob on the radar is constantly changing as it passes over the suburbs.
i can then request the actual rainfall data from several MElbourne Water automated rain gauges.
The data provides rainfall intensity in mm/hr and estimate ARI Annual Recurrence Interval.
Suburb A gets a 1 in 100 year storm for a 6, 12, 18, &24 minute storm, while suburb B gets a 1 in 100 storm only for a 6 minute event.
so for any given storm, there could be multiple 1 in 100 year events.

the above is important as each suburb may have multiple catchments with varying critical times.

April 7, 2021 4:46 pm

The alarmist aim is to make small temperature rise catastrophic.
To do this they made the wide claim of more droughts and more floods.
the IPCC models range was so huge many political jurisdictions have claimed the more droughts and more floods for the same location.

this is a total BS hypothesis and has never been and probably never be supported by quantitative analysis

April 7, 2021 4:49 pm

The Australian Bureau of Meteorology ignores historic record data prior to 1910, if that data was used the BoM creatively accounted warming trend would not be as useful for climate hoax propaganda purposes.

Dr Jennifer Marohasy and colleagues have been monitoring BoM weather stations and records for many years, they have written to The Australian Federal Government highlighting the “errors and omissions” that BoM promised would be dealt with when the Minister asked them to respond to the critics.

We must therefore assume that it suits political purposes to ignore deceptive weather reports and records.

And continue to exercise in futility focusing on reduction of CO2 emissions in accordance with the UN IPCC Paris Agreement targets. After all, so called renewable energy and other hoax based solutions are good for crony capitalist wealth creation at taxpayer and consumers of energy expense.

Reply to  Dennis
April 8, 2021 4:30 am

my town with a local (dodgy)bom rain sensor etc
has been removed from the bom state map and 2 places with NO rain gauges replaced it
wuwt? indeed

April 7, 2021 4:53 pm

Meanwhile, ignoring floods that cannot be ignored when properties are flooded out, the government authorities continue to give new development planning approval for building on concrete “floating slab” foundations, even on flood plains.

Maybe the railway engineers should be consulted as they have the expertise to choose routes and track level well above flooding levels.

April 7, 2021 4:55 pm

Regarding the most recent NSW floods, the following comment was posted at JoNova;

March 23, 2021 at 12:01 pm · Reply

My family has lived and farmed around the Hunter River since about 1850, so there is 170 years of oral history passed down through the generations. I grew up on stories of the 1893, 1949 and 1955 floods, the latter two being recent history just before my birth. I also grew up with the never-forgotten sweet stench of rotting vegetation in my nostrils after the numerous floods of my childhood on the Paterson River (a Hunter tributary). The Hunter River has the biggest catchment of any NSW coastal river and includes some very high rainfall terrain in places.
Maitland CBD sits on the riverbank where the bullock wagon track once ran and a series of grog shanties sprang up to service that trade from the (then largest) river port of Morpeth to all places north and west right up as far as Toowoomba in QLD. Until the advent of the railways in the 1880s Maitland and Morpeth were THE pre-eminent NSW towns outside of Sydney. Newcastle had yet to blossom. The river has changed its course many times since settlement, but back then the paddle-steamers used to come right up behind the Maitland shops to unload into bond stores, so Maitland was on the river for good reason. 
The Hunter’s history is nothing but floods and droughts. One of my grandfather’s earliest memories was of standing knee-deep in flood water as a 7 year old pulling beetroot to salvage what they could of their crop before it all went underwater and rotted. The locals took it in their stride. When the river was rising they would put their beds up on bricks and go to sleep, likewise with their other furniture. The 1955 flood was on a scale the locals had not seen.
In 1955 an entire street of houses below Maitland Hospital was washed away with their residents clinging onto the roofs. A line of big poplars stretched across the floodway downstream and some of the “lucky” residents were able to clamber into the trees as their houses were smashed to pieces on the bridge below. They were hanging out of the trees for a couple of days before they could be rescued as the current was too fierce and the only helicopter sent in for rescues had crashed during an earlier attempt elsewhere, killing all. 
As KK stated, the Newcastle surf clubs sent surf boats up to help with rescues, although Maitland had a number of heavy flood-boats always on hand too. The Army sent in trucks and Ducks (DUKW). The trucks did good service; the ducks not so much. Some of the Duck drivers insisted on plowing up and down the main street, creating bow waves that punched in the shop front windows on undamaged buildings. Out of town their activities were much more useful. 
After even the 1955 flood nothing remotely salvageable was thrown out. Mattresses were hosed off and stood out to dry for several weeks; clothes and bedding were used complete with mud stains; walls were scrubbed down until the fibres in the old plaster showed through; families pitched in to help each other. Several of my mum’s uncles and cousins had their homes and farms inundated.
My father was the northern NSW trouble-shooter for the Massey-Ferguson tractor company. He spent months after the flood stripping down tractors, where MF provided all labour for free via its dealers in the Hunter. The farmers were only charged for oil. Starter motors and generators were washed out then dried in the ovens of a local bakery after each batch of bread was done and the ovens cool enough. Flies were in absolute plague proportions. Life went on without any gnashing of teeth or blaming the CO2 weather gods. 
After the excitement was over many houses were moved up onto higher ground, with real estate prices for ground on the hills rocketing within the year. The block where my parents had planned to build went from £100 to £300 while they were pre-occupied with the flood aftermath.
KK is not quite right about the siting of the town in that the larger part of East Maitland as it then was, also went under. Only the newer hillside suburbs were unaffected. The hills were covered in homes mainly after 1955. Development throughout the floodplain was banned, but now we have three generations of blow-ins with no local knowledge plus young graduate engineers who think that floods are a thing of the past and it is quite OK to develop the flood plain once more. They base their confidence on the levee system strengthened in the 70s. The town centre has nearly gone under twice since then, but they know best. In time there will be a disaster that makes 1955 look tame.
Incidentally, the early settlers were told by the Aborigines that they (the natives) had seen huge mega-floods in the past, one where kangaroos were trapped and washed off the hill on which Maitland hospital now sits — which would make the water probably 70 feet deep on the floodplain. By comparison 1955 was about 20 feet deep in the worst places. Geofluvial survey work has been done on Wollombi Brook (Cockfighter Creek) — a major Hunter tributary — which proves the occurrence of mega-floods in the past few hundred years prior to white settlement, so 70 feet of water may not be far fetched.

Reply to  Dennis
April 8, 2021 4:33 am

yeah back then we saved n repaired damaged stuff
seeing what was being thrown out to be buried recently horrified me
an awful lot could have been pressure washed dried and saved
but the insurers prefer you to buy all new and dont pay to clean n save from what ive experienced myself too

April 7, 2021 5:23 pm

It helps to actually look at the data. March 2021 was not unusual, it was only because Warragamba was so full that it was an issue. Here is the monthly rainfall anomaly over the whole record…..

Walter Sobchak
April 7, 2021 5:49 pm

Antonio Carlos Jobim & Elis Regina – Águas De Março (Waters Of March)

Walter Sobchak
Reply to  Walter Sobchak
April 7, 2021 5:50 pm

This is the canonical version of one of the most beautiful songs ever written.

Walter Sobchak
Reply to  Walter Sobchak
April 7, 2021 5:57 pm

The Jobim Regina version is the canonical one.

Walter Sobchak
Reply to  Walter Sobchak
April 7, 2021 5:53 pm

With English Lyrics sung by Jane Monheit.

Jobim wrote both the Portuguese and English lyrics:

Walter Sobchak
Reply to  Walter Sobchak
April 7, 2021 5:56 pm

A bilingual rendition by the tragic Susannah McCorkle:

Travis T. Jones
April 7, 2021 7:25 pm

Back when carbon (sic) levels were ‘safe’ …
1852: Gundagai floods — 89 die in Australia’s deadliest flood

Unsafe carbon (sic) levels:

Australian floods of 2010 and 2011 caused global sea level to drop
Puzzled oceanographers who wondered where the sea level rise went for 18 months now have their answer – it went to Australia 

Silly, puzzled oceanographers. Just ask the Greens for the ‘science’ …

Coal miners to blame for Queensland floods, says Australian Greens leader Bob Brown

April 7, 2021 9:46 pm

NSW and Qld are big places. This rainfall was confined to the extreme coastal fringe, as it often is. Of course that fringe includes Sydney, hence it’s big news.

April 7, 2021 11:01 pm

also offers an insight into life in those days.”

I don’t need an insight. I remember it. And the Murray floods.

To bed B
April 8, 2021 1:51 pm

Although archived Australian rainfall data is negligible dur-ing 1870 and there is no record of weather systems affecting Australia during that year, a realistic history of the floods and weather systems in the Murray Darling Basin during 1870 is created.</

A study looking at the height of trees near Waikerie, which germinate on the edge of flood waters, showed the highest were just before European settlement, or about 240 years ago. The researchers estimated that it required 4 times the water of the 1956 flood to get so high.

With such a short record, even without being specific about the month, a piddly little flood event compared to pre -European history can look unprecedented.

To bed B
April 8, 2021 3:24 pm

Using data for Centennial Park in Sydney, the recent rains were not exceptional. The highest daily rainfall was for March 28 1943 of 302 mm. 484 mm fell for the month, or nearly 20 inches. For some reason, data stops on the 23rd this year at 315 mm, but likely another 100 mm fell, still well short of 1942.

Another nearby station with a record going back to the early 20th C is the Botanical Gardens. It only had 277 mm that day but 520 mm for the month. This March only had 457 mm.

10 % less rain for the two despite claims that the rains were worse because of simple physics. I’m not pointing out that global warming definitely didn’t make it worse, just that you can’t tell. Now the two sites are also 4 km apart and almost 10% different.

August 1986 shows even a bigger difference. 532 and 408 for the former, over 20% difference. A broken record is meaningless unless shattered by over a fifth because of the huge variability even over 4 km.

Not all months in Sydney are equally likely of having a big dump of rain but close enough that a one in 100 year event for a month happens one in 10 years.

It’s really impossible to claim this was unusual due to climate change.

Reply to  To bed B
April 18, 2021 6:32 am

Just visited Gundagai.
original township built on Murrumbidgee flood plain flooded to a meter depth 1846?
Rebuilt, in 1852? it flooded to a depth of over 4 meters and was completely destroyed with 78 registered deaths.
The next years flood was apparently larger but no town to destroy.
It was rebuilt higher up out of the flood plain and both parts of the township [feuding a little at the moment] exist today.
This was the largest natural disaster in Australia in terms of deaths for over a hundred and fifty years.
Technically a 1 in 75 year event?

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