Brisbane’s Man-made Flood Peak!

How SEQ Water failed “Flood Mitigation 101”.

It is surprising how some journalists couldn’t pick a story if it was humping their leg.

On the morning of 12th January, the day before the flood peak that inundated the Brisbane CBD and much of Ipswich, Brian Williams of Brisbane’s Courier Mail, in a masterpiece of misreporting by omission, reported that releases from Wivenhoe Dam were to be reduced from an overnight peak of 645,000 megalitres/day to 205,000 ML/day with the stated aim of “allowing the Bremer River and Lockyer River to subside, thereby easing floods on Brisbane downstream.”

“Wivenhoe Dam levels had dropped just 1 per cent from the previous night, reflecting the massive volumes of water flowing into the storage from its 7020 km2 catchment.” That 1% drop was from a dam capacity of 191% and is an oblique way of saying that the massive flood surge buffer had been pushed close to its limits and they now had no choice but to dump the same amount of water that was flowing into the dam.

What wasn’t mentioned was the fact that for more than a week prior to this large release, only 170,000  only 100,000 ML/day was released over the weekend as the storage capacity was allowed to rise to 191% from two weeks of heavy rains. And this meant the carefully designed flood buffer, having been taken to its limits, could no longer function as a buffer. The city was entirely at the mercy of the elements and it would only have taken another 37mm of rain in the catchment to hit the limits.

And as it takes 36 hours for water to flow from Wivenhoe to the CBD then it is absolutely clear that the flood peak of Wednesday night and Thursday morning was a direct result of the previous night’s forced release of the total inflow from the catchment. And this was only necessary because SEQ Water had spent two weeks releasing much less water than was being captured, into a river that was still well below minor flood level.

The article went on to report that releases would go back up to 301,000 ML/day in a few days to reduce the flood buffer volume and that this level of release was, “unlikely to cause a second significant rise in the river.”

What wasn’t mentioned in relation to the reduction from the overnight peak of 645,000 megalitres/day to 205,000 ML/day, with the stated aim of “allowing the Bremer River and Lockyer River to subside, thereby easing floods on Brisbane downstream,” was the fact that the earlier large forced release did the direct opposite. It prevented the Bremer and Lockyer Rivers from subsiding and exacerbated the flooding of Brisbane downstream.

By reducing releases to only 205,000 ML/Day after the peak discharge, SEQ Water is essentially admitting that the peak discharge impaired the flow from the Bremer and Lockyer Rivers by about 100,000 ML/day over that 36 hour period, which they then had to remedy with a lower Wivenhoe release.

At this point those who did not come down in the last shower might ask, “so why didn’t they release 300,000ML/day before the buffer was fully extended?” If they had done so there would not have been any need for a larger forced release at all. 

Limited Wivenhoe releases on Monday and Tuesday were justified because the flash flooding in the Bremmer and Lockyer Valleys needed somewhere to go.  But that doesn’t explain the low releases right through the previous week to Sunday the 9th January.  Larger pre-releases in the order of 300,000 ML/day would have maintained sufficient buffer to ensure that no flood peak occurred at all. The river would have kept on flowing at minor flooding level right through this period.

What sort of people, in Queensland of all places, in a strong La Nina wet season, would not start serious dam releases when they were already at capacity, with saturated catchments, in the first week of December? Surely, pre-releases would be more prudent than post-releases in such circumstances?

We need a full inquiry into why this dam managed by SEQ Water, and others managed by Sunwater, were managed in a way that actually produced the kind of flood it was designed to prevent.

[Update: 13/01/11 4.53pm,  The spin is on in full. Television reports are now wrongly reporting that the drop back from the temporary high release volume was instrumental in preventing a worse flood peak. This is totally inconsistent with the 36 hour time lag for water to get from the dam to the city. For the record the major shareholders of SEQ Water are Anna Bligh (Qld), Campbell Newman (BCC) & Paul Pissale (Ipswich).

Wivenhoe Dam capacity is 1,165,000 ML normal (100%) and 1,140,000 ML flood surge (197.8%). It went to 191% or 2,225,000 ML with just 80,000 ML to spare.

Somerset Dam capacity is 380,000 ML normal (100%) and 524,000 ML flood surge (238%). It went to 190% or 722,000 ML with 182,000 ML to spare.  This minimal buffer meant that only 37mm of additional rain in the 7020 KM2 catchment would have maxed the system out, giving them zero control over flows.

The original article by Williams with the same title has been rewritten for the CM archives with the volume data at the end rather than the beginning. You can still get the gist from this link.  I still have a copy of the original if anyone wants to see it. Ian Mott.

Related story

See the SEQ Water site and scroll down to the graph. Note no data for the weekend. They all took the weekend off and came back to a crisis on Monday morning.


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66 Responses to Brisbane’s Man-made Flood Peak!

  1. ggm says:

    I can believe that the MSM will cover this up to protect one of their own (Qld Labour), but you would think that at least the lazy Liberals would at see an opportunity to expose the incompetance of a Labour administration. Yet we see nothing from them.

  2. Tony says:

    You need to check your figures before making such assertions. The Website clearly states for 7 January “Wivenhoe Dam currently sits at 100% capacity, no change from last week” so your claim that it was “allowed to rise to 191%” is clearly rubbish. A graph of dam levels on the SEQWater website also ddemonstrates the erroneous nature of your claims. I have monitored the dam levels closely and so much comment on blogs is similar – just rubbish!

    • Ian Mott says:

      You had best look at the attached link yourself, Tony. Wivenhoe, Friday 7th 106.3%, no data for Sat/Sun and Monday 10th (9.00am) 148.4%, Tuesday 11th 175.9%, Wednesday 12th 186.3%. Somerset, Friday 107.2%, Monday 154.7%, Tuesday 160.8%, Wednesday 189.7%. The CM report refering to 191% was obviously using data other than the standard 8.00am records.

    • Treeman says:

      The Wyvenhoe dam has 100% for storage and a further 100% buffer for flood mitigation. The dam wall was raised a few years ago. The Wyvenhoe was at 190% during the floods. Read this and get a better understanding of the reality Ian is trying to get across.’s-man-made-flood-peak/#more-12840

      • Ian Mott says:

        The good news for all those underinsured residents who’s homes and businesses only went under after Wednesday morning is that you are, in fact, fully insured, courtesy of the public liability of the shareholders of SEQ Water. Going home for the weekend during a 1 in 120 year flood is about as negligent as you can get.

      • sHx says:

        From the SEQ website linked above:

        “The following table provides the latest available information about the region’s dams. Information about the major dams is updated Monday to Friday around 9am, the smaller dams at least weekly. Dam levels are not updated on weekends.

        I checked. Indeed, two days of every seven day period is missing from the records. Must be some kinda conspiracy.

      • Ian Mott says:

        Yes, sHx, probably more of a stuff-up than a conspiracy. It seems the saying, “if it is not being measured then it is not being managed” rings true.

  3. 1735099 says:

    Can you explain why you weren’t posting about this alleged mismanagement of Wivenhoe during the first week of December?
    Unless you can, I’m left with the conclusion that this is simply polemic.
    As a resident of Toowoomba with family in Yeronga, I can assure you that at this point in time there are more important priorities.
    Leave the political analysis until the immediate crisis is over.

  4. Wylie Wilde says:

    They did that because – according to the experts and Global Warming scientists – we won’t be seeing much rain water (forever) and therefore we need to horde as much of it as we can. Besides – having group hugs and public crys – makes for good PR.

    • Didactylos says:

      It hardly needs pointing out that no credible source is claiming “we won’t be seeing much rain water (forever)”. Models project that some areas of the world will see more precipitation, while others will see less. Australia is likely to see little overall change in precipitation (Dai, 2010), although regional projections are still very uncertain.

      Drought isn’t just caused by lack of rain.

  5. Ian Mott says:

    Yes, ggm, it is no small irony that most of the victims of this stuff up are people who voted for Bligh in general and Pissale in particular. Most of the media are simply transfixed by the spectacle to think any further.

    • Deb Buick says:

      Thank you Ian Mott. I was beginning to feel like the only sane person in this circus of double speak.
      Your article and its references are excellent and I too am keeping copies and dates of downloads before they disappear or are reworded. I was amazed with the journalist who had Newman in the Chanel 7 helicopter surveying flooded Brisbane, as Newman was explaining that they were now going to release water daily to reduce the flood water stored. Newman didn’t mention they’d been storing it for months and the journalist didn’t ask why it hadn’t been happening all along!!!! Journalist? Press agent would be a better description.
      I may be very cynical, but the decision to horde the flood waters and thereby place in jeopardy Wivenhoe’s purpose as a flood mitigation system, may be due to the “privatisation” of the water system and the following raise in water rates and substantial charges if anyone dared used in excess of the set amount.
      Serious questions, instead of gentle jibes about drought as we ploughed through flood waters, may have been asked about why we were being forced to pay so much for water, if it was being released to run into the sea.

      • Ian Mott says:

        Thats an interesting point, Deb. My understanding is that it is much easier to get the total volume down to 100% due to the flood gates but getting below 100% is much slower because the “normal” release capacity is much smaller. One of the things that was never made clear when the system was handed over to the SEQ Councils was who pays for the flood mitigation portion of the infrastructure overheads? The price of drinking water is the only revenue stream and a number of Councils get their water from the system but get no flood mitigation benefit because they are on different rivers. I think the whole transfer of ownership from the state to the Councils (at historical cost) needs much closer scrutiny.

  6. Craig says:

    Wivenhoe actually has storage for 1,450,00 Million Mega Litres approx 224% of it FSL. Given that you couldn’t even get this basic fact right and your claimed missing data is actually available on the SEQ website I really have to question accracy of your remaining statements. This analysis leaves much to be desired.

  7. Treeman says:


    How interesting to note the only job advertised for SEQ Water…..

  8. Nick says:

    Hi Ian,

    How were you able to get the daily water release data? Are these figures from SEQ and are they available to the public?


    • Ian Mott says:

      Hi Nick, the numbers I quoted were from the Courier Mail article, presumably Brian Williams got them from SEQ Water. What I don’t understand is why Williams made the subsequent reduction from the peak flow the theme of his article when there had been no reporting of the initial increase in discharge.

      • Nick says:

        Williams assumed figures are wrong. All his estimates in cusecs are high,and he should talk daily volumes.

        He gets one figure right,the 645 GL/day that Wivenhoe releases reached…but this is a transient peak flow figure,not a daily volume. The mean daily volume was in the vicinity of 350-400GL.

        Savages Crossing gauging figures show the transient peak flow there at 1.00am 12/1 was about 6,900 cusecs,which includes Lockyer Creek and local run-off [which would have been intense given the 250mm plus that fell right around the dam wall in the last 20hrs of the deluge]. Transient peak flow drops as the water moves downstream,flattening out. Even if the transient peak of the Brisbane perfectly coincided [unlikely]with the Bremer’s, the most it could amount to with William’s guess is considerably less than 10,000 cusecs.

        The Bremer peaked at 19.4m on the 12th,1.3m shy of 1974,and the Brisbane peaked 60cm shy of 1974’s 26.74m at Mt Crosby,so the flood was never as big as 1974,and 10,000 cusecs could not have been ‘tearing down the city reaches’ .

      • Ian Mott says:

        Nick, I concede that my earlier figure of 170,000 ML/day was too high. Michael O’Brien, in the quote above puts it at 200,000 ML for the two days. I got the 170,000 ML/day figure from an earlier news article that mentioned that figure. But the fact that the releases were lower, at 100,000 ML/day, makes SEQ Water’s position even worse. The 300,000 ML/day release after the surge is the volume that has allowed the water to drop from the flood peak. So it is a moot point as to whether it may or may not have cause minor flooding before the event. The fact is that it was substantially less than the peak release and a few days of pre-release at that volume (ie 200,000 ML/day more than they actually did release) would have ensured there was no need for the panic release and no need for the flood height that innundated so many houses.

        Best you take up the issue of the 10,000 cusecs you think is incorrect with Williams. You are only guessing.

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  10. Ben Cunning says:

    An interesting article, however, how you can state all these as facts without knowing the whole story I don’t know.

    Let me just leave very powerful tool you’ve included here in your arguement.

    I don’t know how you have gone from knowing only the dam levels to concluding the whole situation is SEQwater’s fault. But very well written article, guaranteed to get fellow armchair experts and conspiracy theorists riled up due to your psychologically powerful wording.

    • Ian Mott says:

      Ben, it is all very well to provide a link to a convenient label but you didn’t bother to explain how you think my article fits your label. The facts, as reported by the Courier Mail, are that 645,000 ML/day was dumped over a 36 hour interval from the 12th January. This was the full volume of inflows from heavy rain during that period. They had to dump this volume because most of the flood buffer had already been used up. So unless you can contribute some additional facts that might improve our understanding of the situation then spare us all the faux tabloid analysis.

  11. Nick says:

    Hang on a tick….I think this is one of those ‘hindsight is a wonderful thing’ moments,and I think your figures are a bit wrong. Though hindsight reveals an opportunity missed,I don’t think it was as big or achievable as you think.

    If you are claiming that SEQ water were releasing from Wivenhoe a max of 170GL/day for more than a week prior to suddenly releasing 645 GL/day on the 12th,well I have to disagree. The gauging at Savages Crossing shows nothing of the sort. They released far less than this on every day this year except for the 10th and 11th when they released well in excess in an attempt to keep the dam from overfilling. The total figure passing Savages Xing for the 12/1 will have to be estimated.I’d guess 450-500 GL for the day.

    It is also impossible to reconcile the dam levels in percentages with a figure of 170,000 ML/day release for more than a week. 170 GL is about 15% of the actual contents of the dam on the morning of 4/1. Release that amount every day for a week and you have removed 1190 GL,which would have pretty much emptied the dam allowing for the inflows before the big rain event! That clearly did not happen…and it could not be done in a week from 102% level. It can be done from 190% though.

    One percent of Wivenhoe is 11.65GL [one percent of full water supply level,1165GL]
    After the late December flood ,they were bailing water out fast: as much as 7.8% for the 25 hours to 8.00am 31/12/2010. That’s almost 91GL in 25 hours,nowhere near 170GL. Still a lot of water,over 1000 cumecs,and the Lockyer was just calming down after a bit of a gush,so there was a minor flood on.

    From a peak on the 29/12 at 123% to a low on the 4/1 they got 20.9% out,about 243 GL in 6 days. That didn’t get the dam below 102%… technically,they had done the right thing and freed up nearly all of the flood reserve.The flood that came was a monster,sadly.

    If they kept up the c.90 GL/day rate for six days from 31/12,that would have taken 540GL out of the dam]lowered it from 123% to 80%..but would keep the river well above minor flood level and cut off three bridges as well.. Adding in the flows of the Lockyer,Bremer and smaller tributaries over that period puts in about 7GL/day,so not much to worry about there. However,keeping a lot of people inconvenienced by minor flooding and taking the dam 20% below full may have been politically difficult without 100% certainty that such a huge rain event would turn up.

    But,yeah,if they had managed to win an extra 20% capacity,they would have had space for 233GL more inflow,which as it turned out with the freakishly quick retreat of the trough system and the vanishing of intense rainfall,would have lowered the peak some what.I still reckon it would have got to more than 3.5m at the City gauge.

    Your idea of releasing 300GL/day for several days makes quite a big flood in itself,and is physically limited when the level drops to EL57,the lip of the spillway. After that the smaller capacity outlet works is the only release mechanism.

    • Ian Mott says:

      Nick, great looking post but you forgot to include the inflows to the dams from rain in the catchment. It is more than just a little bit relevant, don’t you think?

      • Nick says:

        I think you need to re-read my post,whether its good looking or not,and re-do maths. Let’s work this out together. Maybe I do underestimate inflows in the week before the 7th,but I think you overestimate outflows even more. Two media releases from Water Grid ,for the 7 and 8/1 mention peak transient flows of 130 and 100GL/day for Wivenhoe releases for those days.These cannot come to 170GL volume per day.

        Dumping 300Gl/day for several days will cause a flood in itself,which is why it is a last resort,and not a pre-flood management option.

        If you look at Savages Crossing gauge at the DERM water site,you will see that 490 GL went down river for the 24hours of 12/1. Pull Lockyer Creek,in flood at the time, out of that,with an estimated 120Gl for the day,and you have 370GL being the highest daily release from Wivenhoe of the flood. That’s the day that they managed to lower the dam 1%, suggests that the total inflow for the reservoir was a little over 350Gl for that day.

        To get an idea of what was coming into the dam on the 11th,we have to add the discharge to the level of increase. Wivenhoe went from 175.9% to 188.5% in the 24 hours to 9am 12/1. That’s about 147GL. For the same 24 hours, they released about 370GL,judging by Savages Crossing gauge and subtracting the estimated Lockyer input. So maybe 517GL entered the dam,I think the figure will be between 500 and 550GL,the bulk of it being immediately discharged.

        All the discharge figures in ML/day used in the media releases that you cite are transient,not 24 hour volumes. If they used cusecs it would help,I know.

        Your suggestion that Wivenhoe was storing more than it was releasing is not true. It stayed at around 100% since being lowered after the October flood. Look at the real time release graph on the dams page at SEQwater’s site. There were two floods before the big one,and in each case they were absorbed, then discharged to return the dam to 100% or very close to. So it was storing 1165 GL and discharging any excess,as per manual.

        You may remember that there were floods on the Bremer system before Christmas as well,which affects how fast they can lower Wivenhoe.

        A dam being kept at 100% is not ‘storing more water than it is releasing’. In the month leading up to the big one,they shed a cumulative 350GL of flood water at the very least,not including other daily releases on non-flood days,to keep the dam at 100%.

      • Ian Mott says:

        No, Nick. Your earlier “analysis” didn’t include inflows and now you are attempting to re-calculate flows based on a downstream reference point and a blatant guess as to how much came from another source. The 645,000 ML figure was supplied by Williams, presumably sourced from SEQ Water. Your references to September and December flows are irrelevant. I was in minor error in not clarifying that most of the rise above 100% took place from Friday to Tuesday rather than the more generalised statement I made that it was over the previous two weeks. But the essential facts remain that the level got to 191% and was still 189% a day later after a discharge of 645,000 ML. It was a needlessly forced discharge.

        17 Jan: Herald Sun: AAP: “Brisbane River flooding avoidable, claims engineer
        THE Brisbane River flooding would have been largely avoided if dam operators had raised their releases of water on the weekend before last Monday’s deluge, an engineer says.
        Engineer Michael O’Brien told The Australian the river flood and the devastation of thousands of homes was inevitable after a decision to release relatively low volumes of water from the Wivenhoe Dam on Friday, January 7, and over the ensuing weekend.
        He said over that weekend the dam’s operators released a total of about 200,000 megalitres.
        Scrutiny of official water-release and dam volume data shows the flood would have been moderate at worst in Brisbane had there been larger releases in the days before the deluge, he said.” Reprinted fropm Jo Nova.

    • Nick says:

      Williams figures are guesstimates,and are too high. My estimates are far more credible,and I have given you their basis.

      645 GL/day was not discharged for a day. Once more,this is a max. transient figure. The proof for that is that Savages Crossing gauge, the first downstream of the dam,and also below the Lockyer confluence passed a daily volume of 480GL for the 24 hours to midnight 12/1. If 645 GL had been discharged for the day,Savages would have seen 645 + 100-150 for Lockyer=up to 800GL 24 hour flow. This is not to be seen in the records.

      During the period of rapid dam increase over the weekend,SEQ water was discharging increasing volumes of water,so it was not as though they shut down the discharge and hoped for the best,then were forced to dump. For instance,from Savages data, the Lockyer passed 47GL for the 24 hours to midnight on the 10th,and Savages Xing 193.4 GL. So 24 hour discharge from Wivenhoe was about 120GL for that period-over 10% of full supply volume. And of course the discharges were raised hourly through that time. I estimate that they were discharging 180GL/day transient flow at midnight on the 10th,and perhaps 225 GL/day transient by 9am on the 11th. The mean volume release for the 11th I estimate at least 250GL.

      Go to the DERM water monitoring site and check for yourself.

      SEQ water may have been able,in technicolor retrospect, to release more on Thursday,Friday and Saturday but this was a time well before the true nature of the coming rainfall was known,and inflows to the dam were in fact quite small up to the 6th [They went mad late on the 9th,after dropping back from a smaller peak very early on the 8th]. SEQwater had just finished discharging 250GL from the previous flood,and have to consider many downstream users if keeping the river high. Again, in absolute hindsight they could have knocked the peak down further at the expense of moderate flooding down to Mt Crosby on the 6-7-8th,but any suggestion they could have got it below major flood level at City gauge later needs to supported by better numbers than you are presenting.

      • Ian Mott says:

        Nick, you claim they are guestimates but you fail to see that your own are not also guestimates. I can see that you are having a lot of fun with these numbers but you are sourcing from only one location without hard numbers from the other sources. I go back to my conclusion which was that we need a very thorough investigation of the whole issue, as Lord Mayor Campbell Newman has called for.

      • Nick says:

        Ian, if we want to know what came out of the dam,we cannot ,in absence of SEQwater dam gate figures, do better than the hourly/daily measurements from Brisbane River @Savages Crossing,subtracting Lockyer Ck @Rifle Range Road.

        I do recognise my figures are guesstimates,but I know they are better than Williams’,because I have obviously had more time to gather them and check them against his.

        I find SEQwater’s lack of detail by now ,Monday 17th pm, bloody annoying, too,and absolutely agree with the need for an inquiry and more thorough media releases.

      • Ian Mott says:

        Don’t get me wrong, Nick. People like yourself who automatically get out the calculator to run through the general numbers they are being told are far too rare. It is the one part of my own personality that I will allow myself the indulgence of being proud of. You are welcome here any time.

      • Chris O'Neill says:

        Nick said:

        During the period of rapid dam increase over the weekend,SEQ water was discharging increasing volumes of water,so it was not as though they shut down the discharge and hoped for the best,then were forced to dump. For instance,from Savages data, the Lockyer passed 47GL for the 24 hours to midnight on the 10th,and Savages Xing 193.4 GL.

        But the 10th was Monday, not the weekend. Looking at the graphs for Savages Crossing and Rifle Range Road on Lockyer Creek is very interesting.

        Lockyer Creek went to moderate flood level (12 m) just after 1 am on Friday morning and at this time the flow at Savages was just over half the flow at Rifle Range Road. The flow at Savages didn’t reach that flow rate (28 Gl/day at a level of 5.36 m which is below the minor flood level of 9 m) until 11 am so I guess it must take at least around 10 hours to get from Rifle Range to Savages. However, SEQ Water had let Wivenhoe go to 106.3% by 6 am Friday morning, even though Savages didn’t even get to minor flood level until after 10 am the next day. So the first question is: what were they doing on Thursday and Friday night that justified letting Wivenhoe get to 106.3% at 6 am on Friday morning?

        The Lockyer then went back below moderate flood by 3 pm Friday and below minor flood by about 9.20 pm Saturday. Meanwhile, Savages was still only 5.63 m at 3 pm Friday and didn’t reach minor flood level until after 10 am Saturday. The second question is: why weren’t they releasing more water from Wivenhoe in this period? Wivenhoe would have been substantially higher than 106.3% and releases in this period would not have increased the flood peak in the Lockyer or have delayed its fall for very long.

        The level at Savages did not reach moderate flood level (16 m) until 4 am Tuesday morning and included a period from 10 pm Saturday to 2 pm Sunday during which it started at 10.36 m and finished at 10.36 m. The third question is: what were they doing during this period? Is there some precious infrastructure below moderate flood level in the Brisbane valley that they were trying not to disturb? Hardly seems likely. If they had allowed a 16 m level at Savages for Saturday, Sunday and Monday, they could have released an extra 178, 146, and 74 Gl on those days respectively, a total of 398 Gl or 34% of Wivenhoe, and this doesn’t include doing anything different on Friday on the premise that it might have aggravated the Lockyer.

        They have a lot of serious questions to answer.

      • Nick says:

        Sure,Chris isn’t hindsight wonderful?

        A few of points.

        At all times before the really heavy rain on the weekend,the agencies did not know,beyond that rain was forecast,how heavy it would become. This should be kept very strongly in mind when considering your last paragraph. I don’t care how many people say they ‘saw it coming’,I say bullshit. They are trying to move from a generality to specifics after the event,and they really need a real inquiry to check it out.

        I don’t think it takes Lockyer 10 hours at moderate to high flow to make it to Savages. It’s a bit under 50km by river from Rifle Range. 5km/hr?

        On Thursday 6th and Friday 7th,flows into Wivenhoe were on the increase,though this was before the real heavy rain. Hence Wivenhoe rose,even while releases increased.They upped the discharges to 100 GL/day transient/1160 cusecs by midnight Friday according to press release. For reasons explained below this won’t square exactly with what you see at Savage’s. They were not doing nothing,by any means

        One thing we have to consider when using the Savages Crossing data to guesstimate Wivenhoe releases is friction.

        I’ve noticed that dam releases are now steady at around 300 GL/day all day,and have been so for days,as they draw down the dam to plan. The steadyness of these releases enables us to benchmark. At Savages, a wider point with more friction and a lower gradient the river is passing about 220 GL/day all day. Pull out Lockyer,which is dropping a couple of gigs a day and is well under 10 GL/day and what do we have? 300 at the dam is about 210 at Savages

        You can see how much a set tranche of water at the dam slows down, drops level and smears out by the time it passes Savages.
        Roughly, it looks like,at these discharge levels, 24 hours of Wivenhoe takes 28 hours to pass Savages.

        They have drained 300GL/day out of the dam at that rate for almost 120 hours:about 1500GL. That quantity will take,therefore, about 140hours-nearly another day-to pass Savage’s Xing.

        This throws our calculations out a bit,and we can’t expect the 24:28 ratio to apply to other dam discharges of course, but I guess it means that we have to add a significant amount to estimated discharges at the wall. This might make what they did do seem less inadequate in your eyes.

        Chris,there always was going to be an inquiry. After an event this big there is a thorough analysis.

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  13. muirdeach says:

    it appears to me you’re pumping an ideological line. It’s well known and noted on the SEQ Water website that Wivenhoe can extend to 200% of capacity and remain within design specifications. The dam is what it is. A flood mitigation project created by Bjelke-Petersen in response to 1974. Without it, Brisbane would have wholly under water this time around. You’re raising spectres which simply don’t exist.

    • Ian Mott says:

      Best read the article again, muirdeach. I refered to both the SEQ Water web site and the flood buffer. But you seem to have missed the point. A buffer is no longer a buffer if it is used up. This buffer was taken very close to it’s limits so they had to dump the entire inflow on the night of the 12th.

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  16. Chris O'Neill says:

    They all took the weekend off and came back to a crisis on Monday morning.

    Ian, is there some way to find out for sure that they took the week-end off? Some people don’t want to accept this until there is proof.

    Also, even if they didn’t take the week-end off, the fact remains that they let Wivenhoe go to 148.4% and Somerset to 154.7% by 9am on Monday the 10th. Marginal additional releases before this time would not even have produced minor flooding in Brisbane, let alone moderate flooding. They need a very good reason why they allowed this rise before 9am Monday morning to happen.

    • Ian Mott says:

      Chris, I posted this at Quiggins just now.
      “Salient Green is attempting to both muddy the waters (sic) and split hairs to obscure the obvious. The BoM data that he quotes as taking place, for example, Maleny 10th 282mm, did not take place on Monday the 10th. It took place during the 24 hours prior to 9.00am on Monday 10th. That is, mostly on Sunday. Ditto for the day before.

      It should also be noted that discharge rates can be seen to rise through a day without management input. There are a number of Flood Gates with a height of about 16 metres (don’t quote me) and their cross section increases as the water level increases, and their discharge rate increases accordingly. But this rise is in a limited range. Clearly, the number of gates needed to discharge 100 Gigs/day is about 1/6th the number required to discharge 650 Gigs.

      So calls for hard evidence that no-one was actually at work on the weekend are standard ploys to obscure a conclusion by linking it to a barely relevant fact. What appears very obvious to most will be that the people with the authority to approve the opening of additional gates were either not at work, or were not contacted to enable them to make that decision.

      The fact remains that an additional release of 100 Gigs/day over 3 days would have halved the subsequent panic release of 650 Gigs on Tuesday night/Wednesday morning. In fact, the 300 Gigs of extra buffer capacity would have allowed them the room to maintain a very modest 200 Gig/day flow right through the past week. It was an entirely avoidable flood.”

  17. Lisa says:

    According to the media (if you believe them), this Royal Commission – type investigation won’t have any findings for about a year. All I can say is that people’s lives and property have been destroyed, and they have to wait a year for these so called “findings” to be produced. Imagine how much corruption and pay offs are going to take place, and people that will have their lives destroyed as they are used as scapegoats.

    • Ian Mott says:

      I hope you are wrong about the pay offs, Lisa. It is fortunate that the largest shareholder of SEQ Water id Brisbane City Council, headed by Campbell Newman, and with a strong political interest in ensuring we don’t get a Labor whitewash. Imagine what it would have been like if Soorley was still in power and the Labor Councils got together with the Labor State Government to massage the truth.

  18. Treeman says:

    This site reveals all: Scroll down to older news and have a look at how much was released and when. It’s damning!

    • Ian Mott says:

      Great stuff, Treeman. So they were there alright but just bumbled along until it was too late. Well done. I knew my 170,000 ML/day figure was in there somewhere. Note how each media statement claims they were in close contact with BoM, with constant references to more rain.

    • Ian Mott says:

      Yes, Treeman, it looks like Game, Set and Match to the unencumbered intellects. And foremost among them is yourself. It is not often one gets a blog thread that starts with a sniff of truth in a forest of backscatter and proceeds to systematically hunt it down through every nook and diversion until it is cowed and cornered. And a large part of that result has been your work. Well done. And well done Chris, Nick and the other fellow travellers who also spoke out on the issue.

  19. Lisa says:

    I am not an expert on the dam levels. Could someone please comment on gate closures at Wivenhoe, and what impact this may have on future rainfall in affected areas. There are so many people who think that everytime it is going to rain, it will flood. The amount of trauma in the general community is rising, especially amongst young children who are exposed to the media (as children return to school next week).

    • Ian Mott says:

      I’m not sure I understand your question, Lisa. Gate closures will not change rainfall patterns. Could you rephrase the question for us?

      • Lisa says:

        What level should Wivenhoe be maintained at (eg 50% or 100%) so that rainfall in this catchment area can be “caught” and “collected” (to remain in the dam), and not be outputted to the brisbane river system. Is 100% viable, like the manual apparently states?

      • Ian Mott says:

        Sorry for the late reply, Lisa, but I was away at my farm without internet access. In answer to your question, there is no problem with a target storage volume of 100% provided it is not set in stone. Wise flood mitigation should have the capacity to react before events, not just after them. The current “manual” appears to only provide for releases after a major inflow but they normally have a few days warning of major rainfall events and in such cases they could easily lower the volume to 70% or even 40% with the knowledge that the pending rainfall will return the level to 100%.

        This is especially the case at the start of a wet season when the likelihood of returning to the desired 100% by the end of April is very high. As long as the 100% target can be achieved by the end of the wet season then any variations before that are of minimal consequence.

  20. Treeman says:


    As sad as it is, whatever the fatalities from these floods you can add one…….Bob Brown!

    The challenge is now to model the unthinkable, Wivenhoe dam wall breached at 200%. Do you know anyone with the ability?

    • Ian Mott says:

      Yes, Treeman, he does seem to have shot himself in the foot. But the problem with him is that he is always playing to his own target audience. And in the inner city electorates where the primary focus is on what goes in which orifice, his crap makes sense to 20% of the voters. The fact that he hasn’t bothered to visit the flooded areas makes it clear that he doesn’t see any votes there anyway.

      As for the modelling, there would be some in DNRM who could do it but the problem is trusting their output.

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  23. Ian Mott says:

    Surprise, surprise, this disaster has the unmistakable stench of the relevant Minister, Stephen Robertson, who has held the DERM/NRM portfolio for all but about 2 years of the past decade. It was his 2010 revision of the Dam operators “manual” that introduced the notion that the Dam should be kept at 100% capacity after each major flow event. This squeezed the last vestige of proactive management out of the show and turned it into a purely reactive disaster waiting to happen.

  24. Treeman says:

    We approach the time when all the people get will be what Bligh wants to say under convention of sub judice. Someone should challenge this convention which has been rolled out over enquiries in a brush it under the carpet style by Labor. You are absolutely right, the stench of Robertson is unsurpassed by the stench from the mud that the Myth of Wivenhoe perpetrated on some less fortunate along the river.

    • Ian Mott says:

      I agree, Treeman. The huge number of journalists now employed by government departments now ensures that all journalists now regard emplyment in government as an integral part of their career path. And that has two implications;
      First, there is a large pool of skilled, fully funded, media manipulators who are actively engaged in either ‘muddying the waters’ or promoting distractions. And second, a large portion of those employed in the media who are reluctant to pursue government incompetence, and in this case, negligence, out of concern for maintaining future career choices.

      • Treeman says:

        No concern for maintaining future career choices is precisely why you and I are prepared to go for the jugular on critical issues like this one. My lobbying effort is totally independent of career although somewhat aligned.
        The thing that amazes me is that so few can grasp the totality of what happened here. For me, an eight year old living in Port Moresby with my own constructed rivers, weirs and dams under the house on stilts, it’s a no brainer. Things that are self evident for me will never gel for most of the punters defending SEQW.

      • Ian Mott says:

        I agree, if they haven’t lived next to a creek then it takes a while to sink in, for some of them never.

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  26. Mary M says:

    Hey you were spot on Ian! Good job. Why aren’t you working in the MSM – we need more journalists like you instead of the group think drones we have now

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