Bishop Hill More on Brisbane floods
Jan 15, 2011 Climate: WG2 Casting around for someone to blame for the Brisbane floods continues and there is an excellent article in the Australian considering the issue of whether the Wivenhoe damn should have been emptied earlier (H/T Aynsley Kellow, in the comments). There is a fairly damning quote from a local hydrologist:
When they finally did release [water from the dam], it was because they had received so much inflow this week that they were afraid the whole system would collapse. There is no doubt in my professional opinion that most of the flooding in Brisbane should have been avoided. It is extraordinary to me that people are not asking more questions about this. Brisbane should have been protected by Wivenhoe Dam. Instead, the dam is a large part of the reason the city has flooded.
There is also, however, this word of caution from an engineer who was involved in the dam's construction:
"These questions are all valid, but put it this way - you would have to have very large balls to [significantly reduce the dam's volumes in the months after the weather warnings] after 10 years of drought, because if you had got it wrong you would be accused of wasting the water"
Reader Comments (91)
I can understand the instinct to hoard the water after a ten year drought. Anyone who's ever adopted a poorly treated, half-starved dog from the RSPCA is familiar with that pattern of behaviour.
There's flooding in Victoria, NSW and Tasmania too. Maybe there could have been something done on a local level, but across Aussie right now, things are pretty grim.
Ref the engineer's statement. The Wivenhoe Dam was built specifically to contain flood waters. That was it's original purpose, and apparently the dam should have been no more than 40% of capacity, pre rains. In fact, the Wivenhoe was considerably over it's planned "normal" capacity pre-flood, and the release of the stored waters at the Wivenhoe and two other major dams in the area was delayed by the State Governor, Ms. Bligh, co-incidently a well-known AGW supporter, until it was too late.
@Simon Hopkinson. We adopted a poorly treated, half-starved mutt from a rescue centre. In our case, the instinct to hoard the water was missing, and it was mop-and-bucket time until the poor thing stopped panicing at the least opportunity.
The blogosphere is debating the floods in a robust sort of way and this is very useful for our cause. If a Royal Commission comes up they will discover that the IPCC prediction for a drier environment in Queensland is flawed.
The models don't work too well in a tropical environment, even Mojib Latif recognizes that.
Are we seeing a sea change of opinion in the MSM?
Germain Greer (who lives part of the year in Australia) writing in the Guardian:
Why were we so surprised? Meteorologists warned Australians six months ago to prepare for a soaking. And nobody did a thing ...
http://www.guardian.co.uk/environment/2011/jan/15/australian-floods-queensland-germaine-greer
Steve Connor (Science Editor of The Indepedent):
This isn't about climate change – but it may be the face of the future ... Scientists have emphasised that none of the three extreme weather events occurring now can be linked directly to global warming. of the future
http://www.independent.co.uk/news/world/australasia/this-isnt-about-climate-change-ndash-but-it-may-be-the-face-of-the-future-2185153.html#
Exactly the the same thing but closer to home with the floods in Cockermouth last winter, the Thirlemere reservoir was full when it should have been at 50%, I believe the Insurance Companies and NW Water are still squabbling about it.
Brilliant discussion Bish.
matthu, I agree that the tone of the media is perceptibly changing, no longer tolerating a knee-jerk blaming of every disaster, drought or flooding, on man's CO2. Some people even remember the last regional forecast from the AGW 'experts', predicting disaster in a particular direction, and are beginning to hold them to it.
As el gordo says
Do they work well in any regional environment? Only it seems after the event. The vast Sahel region south of the Sahara in Africa - where AGW was forecast by models as likely to cause further catastrophic drought (as had happened in 1914) - experienced instead a remarkably greening between 1990 and 2009. By 2009 the models were predicting (or at least retrodicting) increased rainfall. Then, tragically, in June-August 2010, there was famine again in Niger and Chad. I heard nothing about any models predicting that.
With all respect to our friends under water in Australia, more lives are at stake in getting forecasts right for somewhere like the Sahel. It's essential that we try to improve regional forecasting. The increased impatience of the media with facile, unreliable links with AGW theory can only help.
The dam stuff does throw up an issue for the insurance companies trying to hide behind act of God clauses to avoid paying out. If it can be shown that human control of dams has a big impact the lawyers will have a field day.
"you would have to have very large balls ...": there's really little point in having built the dam if its use is handicapped by testicular magnitude deficiency.
The engineer is quite right when he points out the dilemma faced by the dam operators and their political masters.
Perhaps the key lesson to be learnt is that humanity is not as omniscient and in control as we seem to think we are, especially when it involves large systems.
Like all here, I am sure, I have great sympathy for our Australian friends, especially those who have lost family in these floods.
I hope it does cause some of the AGW cheerleaders to pause for thought about their pronouncements, although signs are, many will not.
I though this was interesting on GWPF - if you missed it.
http://www.thegwpf.org/opinion-pros-a-cons/2218-will-alexander-predicting-climatic-extremes.html
There are several issues at question with this event and it will remain to be seen if they are all answered publicly.
Firstly some facts and figures. The 100% capacity of the dam is the capacity perceived for water supply not the dams total capacity. The figures relating to this are laid out in the article in the Australian. The total capacity is then stated as, rightly or wrongly, in the order of 200%. Due to the drought situations in the area a minimum operational level was determined at 60% below which water usage was restricted. This policy I believe was set by the government.
The actual level of the dam can be seen with the historical graph, interactive, at the bottom of the web page for the dam, which I might add is a really informative page and a credit to Seqwater.
http://www.seqwater.com.au/public/catch-store-treat/dams/wivenhoe-dam
Between May 2009 and Feb 2010 it can be seen that the level was kept around the 60% level, but from March 2010 the level was increased to 100% and maintained at that level. Jan 2011 shows the influx of water from the severe rainfall in the catchment area reaching a level of around 190% within a few days between 6th of Jan and current.
So we come to the issues.
The pollicy to restrict water usage must have been issued in responce to the drought conditions and the scientific advice stating that the world was warming and the drought would be an extended situation for the area. The decision not to relax the restrictions after the dam attained the 60% level was probably influenced by the belief in global warming and the advice of alarmist scientist telling the government what they wanted to hear.
What was significant about March 2010?
During the months October to December 2010 there was plenty of published warning that the current build up of the La Nina weather system could provide 1974 levels of precipitation leading to a significant danger of flooding as referenced in the article.
With the conflicting advice from two scientific sources, one warning of long time drought and one of intense flooding it seems that the dam levels were maintained at 100% instead of preparing for severe influx by reducing the dam level to 60% or possibly beyond.
The decision to maintain these levels due to the warmist influence was probably the wrong one in hindsight. Hopefully the influences that led to that decision are now not as influential.
It remains to be calculated if a reduction in the level of the dam during Nov and Dec 2010 would have been enough to reduce the damage and loss of life but one thing is for certain. It would not have made it worse.
The second issue is the reports that over the weekend of 8th 9th of Jan that those responsible for making the decision about water levels were not available even as the level of the dam was rising significantly. This needs to be substantiated and as such I will not pass comment.
The river Brisbane has several tributries leading into it and two of these major ones are downstream of the dam. When the decision to lower the level of the dam was taken these tributries were already swollen and influencing the level of the Brisbane river. The intense release of the dam water thus caused a severe increase in an already swollen river. With the dam at 190% and still rising this decision was the only one that could be made at this time. Failure to control the level of the dam would lead to water coming over the top and start a catastrophic failure of the dam leading to unthinkable devastation.
The second issue needs public investigation which I am sure will happen within time. The first issue requires a change in mindset, not just by Australian authorities but by all. Now it is serious. Now it is costing lives. Now there has to be repercussions.
UK government be warned, this is a lesson to be learnt failure to do so will not be acceptable if the situation of our winter preparedness has not already triggered alarm sirens then this should do. How many lives will it take?
It has now been reported we received some 7 billion cu m of water in 2 weeks in SEQ. We needed about 3 Wivenhoes! The super cell that hit Toowoomba dumped some 200ml of rain in 1 hour in 1 small area.
I agree the dam was kept too high too near this rain event, predicted weeks back. The back room discussions need to come out.
Sad to see Brazil cop similar nasty weather.
Latest count is 12,000 homes here need to be demolished and anohter 16,000 have flood damage to varying degrees. The streets are lined high with wrecked contents. They had to turn away volunteers wanting to help with the cleanup as too many had come forward.
1 lady at 7.30am this morning, on her own, started the dreadful task and wondered how she could manage. By 9am over 35 people had knocked on her door to help - all unoffically. Job done by lunch time.
makes the heart warm.
the courier mail has the best coverage if you want more info.
@Lord B: "from March 2010 the level was increased to 100% and maintained at that level." To keep it at nominal 100% seems pretty rational as you head into the dry season. (Roughly, from April into November). To keep it as high as 100% in the wet season (say mid-November to March) is unwise unless you have reason to believe that the rains will fail in that wet season. Of course, it's fascinating to list the advice that the rains wouldn't fail and that the mother-and-father of a wet season should be expected. But it would be particularly revealing to search out any evidence that there was countervailing advice.
Partly this may be a matter of climate vs weather. The weathermen look at La Nina, muse on the many decades of evidence that droughts are succeeded by floods and say it's going to be Harry Pelters. The climatefolk declare that it's settled science that the drought can only get worse. Consensus, don'cha know?
dearieme
Thank you, should of realised, that answers one question that was outstanding.
This was all very predictable, as am I, so I'm jumping on my hobbyhorse again. Events like these were pointed out in Prof. Koutsoyiannis' 2008 Capri Symposium lecture. You can find the presentation here (click on "presentation", requires acrobat reader)
Discussions of climate flood events are on pp 19, 20 and 26 (the latter showing the tendency for periods of drought or floods to cluster, potentially misleading "experts" who think they can explain these variations)
The consequences are discussed on pages 35 (emphasis as per original)
and from page 37, again original emphasis:
Dr Koutsoyiannis has tremendous insights into this stuff, and as a hydrologist this is his field of expertise, and he foresaw the types of problems we are perhaps seeing in Australia today. Unfortunately because he disagrees with the consensus, his views are marginalised by advocate scientists. Sad.
pete m
"makes the heart warm."
It certainly does. It is the hard times that show you the strength of character of a people.
Australians are not only due our ( I'm British) sympathy, but our wholehearted respect.
Spence, I can't say enough how much I appreciate you pointing to Dr. Koutsoyiannis once again. His time will come. He may even live to see it.
Terrible decision making. They KNEW heavy rains were coming, the knew they could replace any water let out of the reservoir.
Despite knowing, they were so mindset by the years of global warming fear mongering they chose to let the city flood out, cause tens of billions in damages and recovery costs just so they could not be accused of wasting water.
Really "smart" decision making. Brain washed by global warming theology caused them to act really, really dumb.
Chalk up more wasted money caused by the warped and shallow Public Policy decisions driven by AGW bigotry.
There are countless sayings about those who ignore history are doomed to repeat the mistakes of the past. This is just another example. The world did not change because of AGW; peoples's perceptions of their world changed instead.
Now reality has come flooding back, much as the historical data shown elsewhere in this blog shows.
As I noted earlier, the winter in Boston area this year is a replay of the winter of 1978 and 1948. Is there a message there? I think so, and it is we will have a severe winter every 30 or so years.
You do not need a computer to see that. Just a simple chart will do.
A sorry situation all around and I understand the difficulties of balancing competing risks, but I guess it should be a cautionary tale for all those climate scientists that are clamoring for a policy making role.
Eureka! I've finally worked out the difference between weather and climate.
Weather – building a reservoir with capacity for both drought and floods based on past weather statistics and suffering water shortages because you've underestimated the climate.
Climate – using your reservoir to store water for the droughts you might have, based on climate statistics and drowning in the flood you actually get because you've underestimated weather.
According to its website, Brisbane City Council has not been slow in responding to the disaster:
"Financial relief
- All Brisbane ratepayers in flood affected homes will receive a $100 rebate on their water bill".
Interesting article in the Courier Mail from March 2010:
Politician: we need to determine if the balance which was struck in the early 1980s remains appropriate for today.. code for "fill her up"
Engineer: we've got to plan for events much worse than anything on the record
http://www.couriermail.com.au/news/plan-to-raise-wivenhoe-dam-storage-level-for-drinking-water/story-e6freon6-1225839328569
Just quietly, the evidence suggests that the flood would have been far worse without concerted action from the Wivenhoe dam engineers to try and synchronise the outflows with the high tides and peak flows further down the Brisbane river.
However, the skill and 'seat of the pants' judgements' of these guys during the crucial hours of the flood are not something I would want to rely on as a general rule.....and there's a high probability that this flood emergency is by no means over - there's still another 10 weeks of the wet season to go!
While I feel sorry for all the people hurt or worse, I must point out that Brisbane should not have happened. I live part time in northern California and we have had a drought every bit as bad as Brisbane, and the American River is the life blood of the central California agriculture.
Indeed, every drop of water that comes down that from the Sierras is coveted by four or five special interest groups.
Sacramento is the heart of all this as well as the capital of California, with Folsom Dam our equivalent of Wivenhoe Dam. And like Australia, California has had a very very wet winter. And have you heard about the flooding of Sacramento?
No. That is because the engineers at Folsom understood Folsom Dam
I wouldn't be keen on relying on engineers' "seat of the pants" judgments, either.
But infinitely better that than seat of the pants judgments on engineering matters from politicians.
Or scientists.
Or environmentalists.
Saaad,
I suspect you're correct, that once in the crisis, the engineers timed the releases to keep its downstream effects at a minimum, and they deserve credit for that. However, the crisis could have been, if not avoided, then mitigated by lowering the level in advance of the rainy season. This appears to have been a policy decision taken at higher levels, quite probably due to fear of continued drought.
I imagine the inquiries (which will certainly ensue) will establish how those policies were established, and if there was any discussion about rainfall expectation. It wouldn't surprise me if there were voices suggesting pre-season water release, who were over-ruled by those with a more simplistic view of weather and its trends.
Richard, thanks for the kind words, I agree and hope you are correct!
Not yet mentioned in the above is that Brisbane has recently built a desalination plant - currently in mothballs - that could have provided water in the event that the dams ended up empty. That places the decision not to empty the Wivenhoe dam in advance of the floods in even more stark relief.
The other factor is that councils have permitted construction of houses on land known to be prone to floods, most recently in 1974. As I understand the position, prolific information is available about the flood contours, and residents purchasing houses in the flood zones are required to acknowledge the flood risk in the conveyancing process.
Having said that, the role of councils and developers in encouraging residential building in flood plains is surely worthy of examination.
pete m wrote:
"It has now been reported we received some 7 billion cu m of water in 2 weeks in SEQ. We needed about 3 Wivenhoes!"
I would think it was only necessary to have spare capacity for the flash floood of that single day (which was seen coming) to avoid this and not for all 2 weeks rainfall ?
I think this is now an issue for insurance companies to find out to which extent the QLD government was responsible for perhaps irresponsible behaviour and damage.
Ken Blanch recaslls the 74 Brisbane floods
http://www.couriermail.com.au/news/sunday-mail/this-town-has-seen-it-all-before/story-e6frep2f-1225988533849
I must hand it to the Aussies, they show huge courage in adversity.
We had the opposite problem about 5 years ago in California. Predictions were for a heavier than average rainy season, and it started like that. Dam operators kept the reservoirs low in anticipation of big storms. Then the second half of the rainy season never materialized, and the reservoirs ended up low. This was followed by several dry years...
Key question to go along with the water levels at Wivenhoe; what % of capacity was released?
RR
In Alberta, Canada, we use dams for power generation, irrigation and drinking water. I expect this triad of uses is the same everywhere. Although dams are touted here as flood control devices, the fundamental uses are for power and useful water. The trouble with this is that when the first three uses dominate, dams have very little available space for flood control. Power generation requires maximum water levels for future generation certainty. Irrigation and drinking needs are best served with maximum levels for the same reasons.
Dams with non-flood control uses must, for efficiency sake be nearly full. Upstream of local dams I have seen catchment areas that flood during excessive runoff; these are useful flood control measures. Low tech and low cost, they are low, wide areas built in flat areas where the main river can be controlled into unnatural streambeds with elevated sides. When the river rises to a centain level, the larger area is flooded. Dams themselves are almost useless for flood control except by default - when drought has brought the desired level down. Even then, the number of days of excess water capture is severely limited.
We are sold dams for politically useful reasons. But look to they usage. Mostly, you have been sold a politically helpful way to get your tax dollars.
Rainfall or meltwaters beyond what dams can handle is not generally, or in large circumstances, the fault of dam managers. It is the fault of those who have told you you don't need to be prepared for flooding, or build catchement areas, after you pay for the dams. If you want flood control devices that look like dams, you can have them. And after the multi-million dollars they take from you, these engineering marvels will stand empty. Imagine the politicians who will tell you how badly the incumbents are spending your money, and the newspapers who write scathing articles on same.
Doug Proctor, your analysis is correct, but Wivenhoe was built with an explicit flood mitigation purpose beyond its water supply and pumped storage electricity functions. I understand that the operators are required by statute to return its level to 100% within 7 days to preserve its flood mitigation ability. It reached 190-odd percent full before discharges were increased on the Tuesday night before the Thursday morning flood peak in Brisbane. There is a case more should have been released earlier.
The key issue is whether it should have been kept at 100%, including a continuation of water restrictions, which the Premier had earlier said would be relaxed when it reached 60%. This is, after all, the wet season, and all the forecasts were of a severe La Nina. The Mayor saw it coming: the soil in the catchment was saturated, the dam was at 100%, and La Nina was well set. Why keep it at 100%? They spent billions creating a water network, so water could have been sourced from other catchments to maximise the flood control value of Wivenhoe. But maximising water levels in Wivenhoe allowed them to mothball the Tugun desalination plant, so decision-makers (either explicitly or at the margin of their decision) placed a greater value on water stored than on each additional centimetre of flooding.
That is a decision you might expect from a water company sold on the idea by the climate scientists (such as the BOM's David Jones) that drought might be considered 'the new climate': "Perhaps we should call it our new climate," said the Bureau of Meteorology's head of climate analysis, David Jones. http://www.smh.com.au/news/environment/this-drought-may-never-break/2008/01/03/1198949986473.html
A flood control agency might have decided differently.
Incidentally, Victoria, also currently subjected to flooding, is building a very expensive desalination plant. Ironically, construction had already been delayed by wet weather prior to the past week's rains. This project was decided upon by the previous state government on the grounds that building dams was useless, as there would be insufficient rain in future to fill them. Unfortunately, this is a public-private partnership costing around $5B, and its owners will be paid regardless of whether its output is needed. I gave a paper at a conference in Perth in 2005 (I think) in which I argued that desal plants should be regarded only as insurance, not as part of base supply (a little like gas turbines in Least-Cost Utility Planning, which can be built and run in short time if forecasts turn out to be wrong - cheaper than covering risk with high capital cost hydro or nuclear, eg). Victoria seems to have missed the point.
I also share some responsibility for Victoria's fate, having played a very minor role in the SW Victoria water planning process 25 years ago. The philosophy was to price water properly (LR marginal cost) and then build new capacity only when demand required. Pricing proved too unpopular and the anti-dam mentality prevailed, so nothing was built while the population grew.
Politics still isn't very good with dealing with uncertainty, and AGW demonstrates this only too well. But sadly, the 'drought-as-permanent' AGW meme seems to have prevailed over the predictions deriving from our understanding of ENSO.
Here is a few points that have not been mentioned here.
I live 230km north east of the Brisbane River catchment, on the coast.
The rain depression formed weeks earlier and had caused disastrous floods in Rockhampton , 400 km to the north, and caused wide spread flooding in the central Queensland coal fields.
This rain depression was slowly moving south without loosing intensity and flooded the Burnett river catchment to the extent Bundaberg city suffered serious flooding.
Still the rain depression moved south with very heavy rain. I made the comment on WUWT, that if it keeps raining like this, I’ll be able to walk to New Zealand by Friday, because all the water in the Pacific will be in Queensland.
I monitor the Gympie rain radar station, and the north easterly air flow was carrying the rain right into the Brisbane river catchment. http://www.bom.gov.au/products/IDR083.loop.shtml#skip
The people in charge of the Wivenhoe dam had plenty of warning that this rain was on its way and had been so for weeks, yet the policy of the Queensland Government was to keep the dams full because there advice from the likes of Tim Flannery et al, was, because of global warming, Queensland was going to remain in drought.
The timing was all inconvenient, the rains increased in the Brisbane River catchment on the Thursday, 6th, and by Friday afternoon the spillways were releasing 8000 cubic meters a second. Just a trickle for this dam, to maintain 100%, as per government policy.
No one could be contacted over the weekend (8 / 9th ) to make the decision to go against government policy, and open the spillways to lower the level in the dam, and so, over the weekend the dam went from 102% to over 144% in just 2 days, and this is a massive dam.
By Monday it was too late, the die was cast, the inflows to the dam were greater than could be released. The gates had to be throttled back because of the enormous flow in the Bremer river and Lockyer Creek which join the Brisbane below the Wyvenhoe dam.
The level in the dam went to within a few centimetres of having the emergency spillway plugs failing and releasing an unbelievable amount of water to save the main rock and earth fill wall. They are saying, behind closed doors, another 35mm of rain and the dam would have failed and Brisbane would be no more.
Because of bad policy, policy makers asleep at the wheel over the weekend, the Wyvenhoe Dam did nothing to reduce the flooding in Brisbane. In all, building the dam was a waste of time if it could not be managed in the way it was designed.
If the dam was at 40 / 60% when the rain started, there would be no flooding in Brisbane and did the job it was designed for.
Sorry for the long post !
Here's a video from Brisbane City Council's 'WaterSmart Strategy' web page looking at what it calls the "Cultural perspectives on the importance of water".
Beyond the gushing hippy-drippy eco-consciousness, the first thing a casual viewer notices from this slick council promo is its total absence of white Australians. Its dreamy 'spiritual' music segueing between soundbites from Brisbane's immigrants and 'Aboriginal elders', one is left wondering what the white Brisbane majority think about all this? Presumably, they couldn't find one to say anything other than... 'get stuffed'.
http://www.youtube.com/watch?v=Xg41qj-N4qo&feature=player_embedded
web.brisbane.qld.gov.au/environment-waste/plans-projects/
watersmart-strategy/index.htm
"No one could be contacted over the weekend (8 / 9th ) to make the decision....". That's a damning statement.
I live 70 k's south of Brisbane and we knew this was coming for at least a week or more so they have no excuse and it should be investigated, by the way just for a laugh the only part of the country that our BoM predicted excessive rainfall for was the South West of Western Australia the only place in just about the whole country it didn't rain, work that out on your computer models.
As a resident of Brisbane, I have taken a particular interest in the water issue over a number of years. The Wivenhoe Dam was built primarily for flood mitigation purposes following the major flood of 1974. This reached a level of 5.5 metres. The 1893 flood reached a level of 8 metres so the recent flooding is far from unprecedented as some have claimed.
The population of Brisbane has increased rapidly over the last 30 years yet there has been no increase in water storage infrastructure until the recent efforts to "drought proof" the city with a huge investment in a water grid which can redirect water around a grid and the massively expensive desalination plant.
While all this was going on the government imposed severe water restrictions.
In 1989 the proposed Wolfdene Dam was canned by the incoming government against the recommendations of the Water Resources Commission. This was a purely political decision to curry favour with green advocates. In my opinion it was this decision over 20 years ago which has led to the current disaster.
The government became increasingly reliant on the Wivenhoe Dam for water availability as the drought persisted. There was a constant campaign for the public to be "water smart". This became the dominant thinking that every drop was precious to the point that it blinded policymakers to the purpose of the dam. Even when the rains returned and reserves recovered the restrictions were maintained. To be seen to be releasing huge amounts of water in this climate must have terrified them politically.
The proposed Wolfdene Dam was in a high rainfall area and even in relatively dry times would have easily provided sufficient water to the growing population. Shortsighted political advantage won out however and now the only upside is the fantastic and spontaneous efforts of tens of thousands of citizens who are helping out their unfortunate neighbours.
No comment on this, other than to say that someone has jumped the shark!
http://www.news.com.au/breaking-news/coal-miners-to-blame-for-queensland-floods-says-australian-greens-leader-bob-brown/story-e6frfku0-1225988806619
Of course greed and politics play their part
"A SECRET report by scientific and engineering experts warned of significantly greater risks of vast destruction from Brisbane River flooding - and raised grave concerns with the Queensland government and the city's council a decade ago.
But the recommendations in the report for radical changes in planning strategy, emergency plans and transparency about the true flood levels for Brisbane were rejected and the report was covered up."
The full article in The Australian is here
http://www.theaustralian.com.au/news/nation/alarming-report-on-risks-covered-up/story-e6frg6nf-1225986634328
MY heart and money goes out to Queenland. Please give generously
http://www.qld.gov.au/floods/donate.html
I think hydrologist Aron Gingis,while right to call for an inquiry,is going too far with too little information.He needs to wait for his inquiry. If operators had decided to change procedure and keep the dam at 90%,they would only gain 116GL capacity,which is a fraction of potential daily inflows in extreme events.Keeping it at 80% would be better,I suppose but not much. The last few days flood inflows were massive. There was a lot of damage to monitoring infrastructure, data is missing and flow volumes will have to be carefully estimated in places.
The dam was never designed to prevent all flooding,particularly extreme floods.A dam which could do this would be a massive undertaking given the characteristics of the valley. It was modelled to take a few metres off a 1974 kind of flood,but a lot of perhaps unwise urban infilling and change has occurred in the flood plain with the city adding 1,500,000 people since that flood,so the flood footprint has changed.
For those who claim there would be no flooding in Brisbane if the dam had been kept at 40 or 60%,before we even consider that claim,you have to understand that two very substantial unregulated streams,Lockyer Creek and the Bremer River,join the Brisbane River below the dam and above the city. They can cause flooding in their own right along the Brisbane River. Then you have to realise that discharging big amounts of water supply speculatively is a management procedure most would avoid. And to lower the dam without causing any disruption downstream seriously constrains the amount releasable daily. All this to gain a few hundred gigalitres space. Much more than that amount entered the reservoir on just one day of the deluge.
Just before this flood,water managers had discharged 250GL from Wivenhoe to get the dam from 123% back to 102% from a smaller flood the previous week,and they had undertaken a similar procedure the week before. This put serious amounts into the river,cutting bridges and causing minor flooding when combined with Lockyer Creek waters...the river was running strongly for a lot of December.
Because of this time-frame the last real opportunity to change operating procedure and lower Wivenhoe was the first week of December. It would take some slick forecasting to predict and pinpoint rainfalls of up to 300mm/day a month later.Who saw that coming?
Chris of Hervey Bay,you are making stuff up. "No-one could be contacted over the week-end.." Prove it. "...to go against government policy.." The dam operations manual is not 'government policy',it is a carefully thought out technical work. "By Friday [7th] afternoon the dam was releasing 8,000m3/sec..."
Rubbish,according to Water Grid's daily press release,they were releasing up to 130,000ML/day,which is 1,500 m3/sec. Chris,at no stage in this event did dam managers release 8,000 cumecs,even in transient flow.
There are too many wild allegations circulating,mainly to use as a stick to beat imaginary foes.
Nick:
'Because of this time-frame the last real opportunity to change operating procedure and lower Wivenhoe was the first week of December. It would take some slick forecasting to predict and pinpoint rainfalls of up to 300mm/day a month later.Who saw that coming?'
Who? The BOM. The Lord Mayor. (To name just two). The issue is not so much about the management of the flood protection part of the storage, but keeping water supply at 100% from the start of a wet season, maintaining water restrictions in the face of a severe La Nina.
I have said it before: the climate scientists have a good understanding of ENSO. Why was this ignored in favour of a concern for 'every drop is precious.' It's not a matter of whether any flood could be avoided, but whether it would have been as serious. Was the value of water held in the dam (enough for several years' consumption) greater than the marginal value of damage that could have been avoided for each cm reduction in flooding in Brisbane? We don't know, and that is surely the point.
Prof Kellow's reference at 10:50 deserves to be shown in more detail. Senator Bob Brown is the leader of the Greens and they will have control (albeit as a "coalition" minority) of the Upper House in six months. Military, police and other personnel are still looking for bodies, but that hasn't stopped Bob jumping in and pointing the finger at who are "partly" responsible. Sitting on his ar*e 2000 km away in Hobart he comes up with this -
It would be incorrect to describe Senator Brown as contemptible. He is beneath that.
Aynsley, the intensity,position and persistence of a trough can't be known a month ahead,despite such events being experienced often enough in the past. Whatever,how real are the gains of a lowered Wivenhoe in extreme events?
Suppose government got advice to lower Wivenhoe on the chance that December would see flooding [it actually saw three in the Brisbane River catchment]. By how much? 10%/116GL? 20% 232GL? These are actually not very large amounts ,in the context of volumes in this last flood. But say they dropped it 20% by the end of November,taking the dam to 80% of full water supply. Then say that December unfolded exactly as it did-same release management moves,same rain events- with some rises and a couple of smaller floods entering the dam,then the big one hit. Instead of getting to 190% the dam would have got to 170%,they could have held on to that extra 232GL and gone to 190% the next day in so doing. So we take 232GL out of the top of the flood...
This hypothetical would have possibly translated into 100GL/day less going over for a day or two. How many tens of centimetres in a lower peak would this translate to at the City gauge,I'm not yet sure. Whatever amount,I don't think the flood would have been less than the major level. The many houses that went under to the roof line would not be spared by even a fifty centimetre drop. And all this speculation is based on an exact replica of the recent event,minus 20% of Wivenhoe. Vary the rainfall pattern,lengthen the period,and what appears to be clear-cut strategic sense becomes very modest. Really big events will be trouble for Wivenhoe at its current scale,20% down or not
This suggest to me that the plans to raise Wivenhoe will be fast-tracked,maybe the 4m option. That gains an extra 500Gl flood storage
If the rain intensities had continued for another few hours,even that hypothetical 20% gained by the precautionary lowering would have left us with the same flood peak.If rain had continued for twelve hours as forecast on the evening,the peak would have been higher in both scenarios. 1974 saw a lot more rain fall in the Bremer catchment, and the SW and N suburbs of Brisbane,which played a big part in amplifying that flood.This still remains an enormous vulnerability,once again worsened by the increase in urbanisation since that time.
...every time someone dies as a result of floods in Australia, a Guardian environment writer should be dragged out of his office and drowned ...
Only a joke.
The lawyers will have a field day with the Insurance companies.
This was not an Act of Nature. The flooding and all tel the death, damages and misery were an
Act of Government.
This is going to get very, very ugly when reality settles into the affected people that none of this should have happened.
This was a man made disaster.
The context that saw the building of the Wivenhoe dam was not they way it was ultimately operated.
That change is due to the rise of environmentalism and the impact that movement has had on Australian politics.
You cannot now build a Wivenhoe type dam anywhere in Australia, anywhere. It does not matter if the intent if store water, mitigate floods or generate power, dam building in Australia is impossible.
The effect of that situation is that Australians will have to live with long term water restrictions, future power black-outs and find themselves at more risk from severe wather and climate events.
Now here is the potty green irony their passion for building desalination plants means not are they hugely expensive to run, water is 12 times more expensive to produce than what a dam produces, they are all powered by coal.