Floods

[Autocon]

Hope anyone of our QLD members affected by the floods is ok!

[griffin]

From last weekend in Brisbane... over a 3 day period, we had a low pressure system held in place by 3 different low pressure fronts from different sides, being close enough to the coast to keep feeding it with moisture. Basically, it was a non-rotating cyclone.... if it had significant wind in a cyclic pattern, the low pressure system probably would have been classified as a cyclone.
The rain event came to the coast around the Sunshine Coast, and moved very very very slowly south, taking 3 days to get to the boarder, and then a week to get to Sydney.
In that three days, some parts of the South East corner of QLD had over a meter of rain... so if you imagine standing in a meter of water, that would be what everywhere would have been like if the entire land was flat, but when you take uneven land and gravity, that one meter of water compounds quickly the further downhill you get, particularly if there is a drainage bottleneck anywhere, like small creeks or the tides.
Some places had more than the entire year's worth of rain in one weekend.

This was the rain system on Sunday afternoon with the most intense part (the brighter colour) still over the southern suburbs of Brisbane, but the rain (blue colours) starting to spread south of the border into Northern NSW (because it was a very slow moving, non-stop system, it quickly flooded the smaller towns south of the border even though the rain wasn't as heavy as it was over Brisbane.




The next three images are the rain gauge over South East QLD for Friday, Saturday and Sunday (totals are taken from 9am to 9am, so the Friday total is posted up at 9am Saturday). You can see how slow it took to move each day... and you can also see how the rain was so heavy in parts that it maxed out the BOM standard rain gauge of 25cm. If you have a school ruler around (30cm), most of Brisbane got at least that much water in just 24 hours. Take a look at Boondal (just above the dot for Brisbane CBD), and they got over the maximum amount all three days.
(Friday 9am to Saturday 9am)


(Saturday 9am to Sunday 9am)


(Sunday 9am to Monday 9am)


(Monday 9am to Tuesday 9am) The heavy rain had finally moved south away from Brisbane.


This is an interesting one. (well I think it is ) The two Dams that supply Brisbane with drinking water are called Wivenhoe (the big one) and Somerset (the smaller one). Somerset feeds into Wivenhoe, and Wivenhoe has an extra 200% of flood capacity (the "100%" level is about a 3rd of the entire dam capacity, but is the Drinking water level that they keep it under, which allows for rain events like this one to fill up the rest instead of adding to the flooding downstream in the city). If you look at the end of the graph, the rain event last weekend added the entire Drinking Water capacity to Wivenhoe, going from about 60% to 173%. That's like having about 5 years of drinking water in one weekend. (Somerset went from about 80% to 155%)
Now, look back to where 2011 is on the graph and see how the lines barely peak above 100%. That was the last Brisbane flood event that actually saw the River hit 4.2 meters above normal (this 2022 flood only reached 3.7 meters), and that was because that 2011 heavy rain event came in from the west (Toowomba) instead of the north, so it mostly missed the two Dams, and as such, most of that heavy rain flowed down towards the coast and went straight into Brisbane and backed up the creeks into the suburbs. So even though 2011 saw greater flooding and damage in Brisbane and Ipswich, the Dam level graph makes it look like 2022 was worse... just because the rain came in from a different direction.


Sunday, when the first rays of sunlight broke through from the west in the afternoon just before sunset, while the rain was still softly falling...

.

[kovert]

The weather was crazy that weekend.

Very informative analysis.

[griffin]

Covid gave us shortages of toilet paper (why??? we will never know), while the floods gave us shortages of frozen veges...

[Autocon]

Still have toilet paper shortages in WA

[DELTAprime]

Still have toilet paper shortages in WA

The reason for toilet paper still being in short supply is not the toilet paper supply, but the plastic the toilet paper is wrapped in being in short supply. Stupid eh.

[Sinnertwin]

Lol toilet paper
Stop pooing so much and learn to clench. You'd be surprised at what the human body is capable of.