The really boring and totally pointless snippets thread V

[Hydromet]

Good morning all. Clocks back today, will have to refer to manuals for watches. Clear blue skies, currently 19C, forecast max 27C.

[bob2s]

Thanks for that info Hydro, like all others here in the flood plains, we would prefer a more controlled release to take into account the choke points,
incoming tide etc. rather than have the release of 200 glt/day which equates thoroughly to 1/2 a Sydney Harbour/day to add to the runoff flowing
into the river. Surely in this day and age, there must be enough in the way of observations, studies and other information to allow a prior release of
water to mitigate flooding . This time flooding is only classed as minor and did not leave us isolated as the Windsor Bridge did not close, even with the inflow from the dam helping, the water level was still a meter below the bridge at 9.5m, 10 m and we are isolated from the rest of Sydney.

[Karearea]

Blue dome day, was chilly 3°C first thing, now well on way to the 19°C promised.

I see ZK-TAF, North American P-51D Mustang, is heading northward along the Pacific coast of the South Island.

Autumn leaves colouring and falling fast now.

[Hydromet]

Unfortunately, quantitative rainfall predictions are still not very good, especially more than three days out. If you look at radar, i.e a few hours ahead, they're a lot better, but even then, they're far from perfect. When you know how much rain has fallen, you can predict pretty accurately how much runoff you'll get, but in the Warragamba catchment, that will only give you a few hours warning. Think how many times the BoM has forecast floods that didn't eventuate, and how many times they haven't forecast floods that hit (less often, because you always want to cover your arse, but I can think of a few.) If you forecast a big flood and it doesn't arrive, pre-releasing is likely to bring you into a drought earlier, and everyone will remember all that water you wasted.

If I recall, the dam was at about 150 Gl below FSL immediately before the flood. I'm not sure what the channel capacity is, but say They'd started releasing an extra 50Gl/d, three days early. They'd have reduced the duration slightly, and taken a little off the peak flow, but in reality, there would have been little reduction in the peak level once the river broke its banks, albeit there may have been a decent reduction in the area flooded.

The whole show is a monument to greed and poor planning, Bob. It's been known for 200 years that the Hawkesbury floods, but over the years, politicians from the lowest to the highest levels have allowed developers to build large urban areas on arguably the most fertile area in Australia. Each building on a flood plain increases the level and velocity of the flood. Each building, footpath, road, tree removed and swimming pool increases the peak flow and speeds up its arrival. I know it's easy to say that building shouldn't have been allowed there - Macquarie tried that, and look where he got - but it's true.

I can only think of two - partial - solutions. One, already proposed, is to enlarge the dam to allow a larger flood mitigation storage. This allows more water to be stored during a flood and released later at a controlled rate. This only works if you have the topography, the money and the popular support to do so. The effectiveness of this will rely on the size of the flood mit storage, relative to the size of the floods. It's probably going to be quite effective for small floods, less so for big ones. However, if the flood is followed by a drought (and they always are, eventually) there will be no shortage of people telling you you should have used the flood mit storage to store more water for the long term. The other is to ban further building on the flood plain, buy back the worst effected properties and assist, to whatever extent, the occupants to relocate. Again, you need the money, the popular support and somewhere for people and businesses to relocate to. That's hard enough in a small country town - let's see anyone do it for several million people.

I make no comment on the merits of either of these partial solutions. It's way above my pay grade. However, there is a quotation often known as Munro's Law after Professor Crawford Munro, first professor of Civil Engineering at UNSW, that says, effectively, "If you've had a flood, you'll have a bigger one." So far, it's proven true.

[Karearea]

Unfortunately, quantitative rainfall predictions are still not very good, especially more than three days out. If you look at radar, i.e a few hours ahead, they're a lot better, but even then, they're far from perfect. When you know how much rain has fallen, you can predict pretty accurately how much runoff you'll get, but in the Warragamba catchment, that will only give you a few hours warning. Think how many times the BoM has forecast floods that didn't eventuate, and how many times they haven't forecast floods that hit (less often, because you always want to cover your arse, but I can think of a few.) If you forecast a big flood and it doesn't arrive, pre-releasing is likely to bring you into a drought earlier, and everyone will remember all that water you wasted.

If I recall, the dam was at about 150 Gl below FSL immediately before the flood. I'm not sure what the channel capacity is, but say They'd started releasing an extra 50Gl/d, three days early. They'd have reduced the duration slightly, and taken a little off the peak flow, but in reality, there would have been little reduction in the peak level once the river broke its banks, albeit there may have been a decent reduction in the area flooded.

The whole show is a monument to greed and poor planning, Bob. It's been known for 200 years that the Hawkesbury floods, but over the years, politicians from the lowest to the highest levels have allowed developers to build large urban areas on arguably the most fertile area in Australia. Each building on a flood plain increases the level and velocity of the flood. Each building, footpath, road, tree removed and swimming pool increases the peak flow and speeds up its arrival. I know it's easy to say that building shouldn't have been allowed there - Macquarie tried that, and look where he got - but it's true.

I can only think of two - partial - solutions. One, already proposed, is to enlarge the dam to allow a larger flood mitigation storage. This allows more water to be stored during a flood and released later at a controlled rate. This only works if you have the topography, the money and the popular support to do so. The effectiveness of this will rely on the size of the flood mit storage, relative to the size of the floods. It's probably going to be quite effective for small floods, less so for big ones. However, if the flood is followed by a drought (and they always are, eventually) there will be no shortage of people telling you you should have used the flood mit storage to store more water for the long term. The other is to ban further building on the flood plain, buy back the worst effected properties and assist, to whatever extent, the occupants to relocate. Again, you need the money, the popular support and somewhere for people and businesses to relocate to. That's hard enough in a small country town - let's see anyone do it for several million people.

I make no comment on the merits of either of these partial solutions. It's way above my pay grade. However, there is a quotation often known as Munro's Law after Professor Crawford Munro, first professor of Civil Engineering at UNSW, that says, effectively, "If you've had a flood, you'll have a bigger one." So far, it's proven true.

^

[Hydromet]

Thanks Karearea.

[OFSO]

Morning all. Dry and breezy out. An excellent night's sleep as drank less water yesterday.

[Ex-Ascot]

Moring folks. Wish we had a flood. The very few patches of water remaining of the lagoon our drying up leaving mud flats. Fortunately the flood plain in front of us is all green. A sunny day.

[Hydromet]

Don't worry, Ex-A, it always rains after a drought.

[G-CPTN]

Maybe you should appoint a Minister for Drought?

In the last week of August 1976, days after Denis Howell was appointed 'Minister for Drought', severe thunderstorms brought rain to some places for the first time in weeks. September and October 1976 were both very wet months, bringing to an end the great drought of 1975–1976.

[Rwy in Sight]

My father was in hospital for the battery of his pacemaker and I was concerned about the outcome. He is at home now but I didn't make a point about wearing a facemask and I am concerned about getting a renew case of COVID after his December one.

We could use for massive amount of rains as we had a very dry winter.

[Wodrick]

Greetings,

17°c, 24°c predicted by the soothsayer.
Calima, viz <4km. Supposed to dissipate today.

Really quite unpleasant with a grey denseness like this.

Normal Sunday.

[1DC]

Full gale on the Humber,presently 12C and 16 predicted but blue skies although we have had showers. We always seem to have showers!
Found Hydro's missive interesting, nice that most of the people on here seem to know what they are talking about.
Made a chicken curry last night now in the fridge festering away getting ready for tea, looks good.

[Hydromet]

Thanks 1DC. I'm happy to talk about what little I know about, because discussions on here are invariably civil, unlike some other places.

[Malvernian]

Jackdaws have been building a next under the solar panels on the roof. Had to make a rod with grappling hooks on the end to get all of the twigs away. Managed to fill half a dustbin with the twigs. Always feel a little guilty doing this, but don't want the nest affecting the panels

[Hydromet]

Good morning all, clear blue skies today. Currently 16C, forecast max 25. Hope to finish mowing the lawn today.

[bob2s]

Morning all, I just returned from the doctor due to needing scripts and arm punctures for Flu and Covid. The flood waters are receding and most of the
roads are open, those that are still closed are a few where the road edges crumble due to the road being too narrow, and are likely to cause
damage to vehicles before drying out. Thanks, Hydro once again, but you can understand it's nice now and then to vent one's thoughts even when one
knows it is a lost cause.

[Hydromet]

I do understand, Bob, and we all know that sometimes, even 'experts' have their agendas and it's worthwhile questioning them. As we know, the current situation puts lives & property at risk, and we have to find a solution. I doubt that there are any more engineering solutions, but I may (probably) be wrong.

[Ex-Ascot]

Morning folks. Cloudy, rain forecast but not much. See a BA stewardess has been sent home from the Maldives for being drunk and disorderly. BA have a better class of trolley tart these days.

[Woody]

Whatever happened to the unwritten rule that, whatever happens down route stays down route

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