Toowoomba Dams

[Gad]

Hi all neighbour just called out to say for the 1st time since 1999 all dams at Toowoomba, Perserverance,Cooby and Cressbrook have reached over 100%.

Do these dams have flood gates ,do they have an over load(flood mitigation) storage capacity or do they just reach a point and overflow spillways.

What catchment area do these releases/overflows go into...Wivenhoe??

Thanks, just trying to do some figures to see if now is the right time to buy an Ark :dry: :laugh:

[ellicat]

Considering they are on the other side of a fairly well-known range, I'm pretty sure they empty into the west/south flowing rivers .

Lucky for you as there are no arks currently on the market.

[Gad]

ta,I was under that impression also,but She Who Knows All(#2 daughter)tells me that they flow into Cressbrook creek(river?) and that flows into upper Brisbane system then into Wivenhoe.

just as a by line this came up on a weather forum at 3.40 today don`t know if real or not at the moment..

Radio 4BC just read out a list of emergencies happening in Toowoomba at the moment due to that 'cell' that has just hit it. Apparently people are missing, landslides occurring. Several cars including police cars are underwater.

Edit to say: a TWBA resident has just called into the radio station. At the moment there is no way into or out of TWBA with landslides/flooding occurring. People trapped inside a fruit shop, they are apparently hanging onto poles waiting to be saved. Cars with people trapped inside them and helicopters have been called in for emergency rescues. He will be back on 4BC after 3pm with full details. This has all happened in the past hour apparently

[Gad]

The reason I wanted to find out which way their overflows are going is,with our own catchments at high levels of runoff and more predicted rain I saw this maybe incoming mass and automatically thought ARK... check out MTSAT loop . http://www.goes.noaa.gov/sohemi/sohemiloops/shirgmscol.html

[ellicat]

SWKA may well be right. I just had a look at the Google map and the spillway is on the eastern side and looks like it flows up and over into the Brissie.

Cooby is definitely a west one though.

[Terry H]

Perserverance flows into Cessbrook.

I can't see where Cessbrook flows though, its right up against the range, and to be honest, doesn't look like it has that clear of a creek bed flowing from the dam wall. Unless its that dry dirt path? lol.

Guess the dam hasn't had much water coming over it in the past 10 years!

If the flows meander their way through the range, it's quite possible they link up with the brissy River either upstream, or downstream from Wivenhoe.

Be nicer if its Upstream, at least then Wivenhoe Dam can control, to some degree, the volume of water getting pushed downstream.

[goldnugget]

A quick update on the Toowoomba situation, the bulk of the flooding that affected the city is splitting between Stanthorpe and down the range. Those living in low lying areas between Toowoomba and Brissie (gatton etc) are being advised to get to high ground asap until the surge passes (heading towards Brissie River I suspect)...from the channel ten news latest update...Helidon apparantly has gone under, so it is on its way.

[Terry H]

Brian, take a look at google maps (the maps, not the satellite images)

Looks like Lake Cressbrook flows into Wivenhoe. So all that outflow from Perseverance they showed on the news goes into Cressbrook, and out towards Wivenhoe.

On the news they said it was receiving inflows of 1M ML a day... fk me if thats true, that's the water supply capacity.. each day o_O

[tomca]

Cressbrooks overflow goes past Esk and into Wivenhoe.

[Gad]

thanks fellas. what started me looking at these particular inflows was a comment on a weather forum re in flows into Wivenhoe and at what height on the dam wall is reached when SEQwater has to fore go precautions and just open gates wide and stand clear all below

response was...

asked about the floodgates ,

at 73 meters it reaches the top of them but they are built into the wall which stands at a whopping 80 meters, however at 74 meters they have to attempt to keep the dam at 74 m by opening the gates wider at 75 meters it starts to go around a fused spillway like a big rock spillway and this will washout allowing more water out of the dam ! At 78 m and rising I'd evac half of Brisbane

Wivenhoe dam wall would never break as such , it has a second spillway to let water out seen clearly on google maps on the northern side of the wall. If it went over the wall it could possibly wash part of the wall away.that will never happen!

[goldnugget]

From memory, as far as the main Wivenhoe wall goes (the one you drive on), as you come in from the fernvale side you have the gate section, and the second half of the wall is a fixed reinforced flood overflow of the wall as well, I remember stopping there on the other side (right side park and info centre) and reading about it.

[Do$tylz]

wow... so is it time for the Bris river siders to start to consider what they'd do if this rain into Toowoomba continues??

[dassa]

What people don't understand is that the 7 metre's of water coming down laidley creek joins the brisbane river below the wall at wivenhoe so any one in low lying area's take care now.

My mate's misses car was 1 of the one's washed away this afternoon.

[goldnugget]

I agree with Dassa, anyone affected by floods comparable to the 70's floods should look at making a plan to go to higher ground from tonight. May sound extreme but the levels in the brisbane river are rising, and they are not affected yet by the wall of water comin down the locker, check my thread on re dangerous conditions coming and you will see that the flooding has just reached Glenore grove, so I dont know what will happen come midnight for Brisbane...this is just my opinion, I am not in the region, but make my call based on the data available from the pages I have listed on the other thread.

[rayke1938]

From memory, as far as the main Wivenhoe wall goes (the one you drive on), as you come in from the fernvale side you have the gate section, and the second half of the wall is a fixed reinforced flood overflow of the wall as well, I remember stopping there on the other side (right side park and info centre) and reading about it.

The second ( New) spillway is designed to self destruct if it is topped.( Called fuse plug spillway)

It is simply a heap of rubble that is designed to erode away and immediatly drop the level of the dam to the normal full supply level of 67m.

I do not know what the height of the fuse plug spillway is.

This is to protect the integerty of the dam wall itself.

Oviously this would let a very large volume of water into the Brisbane river and would cause major flooding and the dam would be left with no buffer to prevent subsequent flood events until the fuse plug spillway is reconstructed.

Cheers

Ray

[goldnugget]

Thanks Ray,

I knew it had something to do with an overflow but couldnt remember the exact details. I do remember that they had sort of like staggered baffle plates on top of them (and I presume some depth within the wall)so that even though that wall deteriorates, supposedly these will prevent the top of the mound just dropping away in one hit.