If you read the whole chapter again ask yourself what anyone around in 2011, not just the four engineers, knew about W2. I think they knew that it was transitional from W1 to W2 and that it introduced 3,500 cumecs at Lowood as a limiter, along with 4,000 at Moggill. I think they clean forgot about the business of limiting releases to the natural flows at Lowood and Moggill, otherwise they would not have thought that W2 was in use at all, ever, during the event.

When the engineer said we were already releasing 900 cumecs at 8am when the natural flow at Lowood was 550, therefore W2 was unavailable, the Commission said, wait a minute, you can’t use existing release rates as a reason, you could intend to reduce the releases to less than 550, so you still have to make a choice, which you would do according to what is appropriate in the conditions.

The rejoinder is that you would only consider it appropriate if the rain had stopped in the Wivenhoe catchment, but was belting down in the Lockyer and you wanted to let it past. But you wouldn’t choose W2 because you could already do that under W3 and as Ruffini said (p448) there were other practical reasons for not wanting to ‘jump into that space’. W2 is redundant, and the Commission should have seen it as such.

That point about the relative rain in the catchments was made to them, but they were too intent on finding fault with the engineers to understand its true significance.

They have to allow time for someone to get out there and put up the barriers and the signs. In some cases, eg Fernvale, I believe they allow for emergency health evacuations also. This came out because there was impatience about how long it took to close the higher level bridges after a decision had been taken to do so.

The main game IMHO is the first page of W1, W3 and W4, with levels of 67, 68.5 and 74m respectively, together with stream flows of 1,900 cumecs at Mt Crosby Weir Bridge and 4,000 at Moggill.

W2 is redundant. The rest is at the next level of detail.

BTW the maximum flow of 1,900 cumecs in W1 is only theoretical, and would only be possible if no water was coming from elsewhere. The real limiting factor is the Mt Crosby Weir Bridge, which goes under at 1,900 cumecs. At 8am on Saturday there was 550 cumecs coming in from the Lockyer Creek.

Keeping some bridges open wasn’t a bad idea. the Fernvale Bridge (2,000 cumecs) is on the Brisbane Valley Highway. From memory at the time it was the only way to get to Rockhampton from SEQ until it too went under.

The manual dictates in each strategy except W4 a maximum allowable release, but not a minimum.

Reading through the strategies (particularly W1A to W1E) the alignment of the “maximum release” and the goals of limiting combined flows gives me the impression that the maximum release is simply where the flow from the dam itself (ignoring any other sources) is enough to cause the goal to be lost (i.e. water over the particular bridge). Once you’re at the point where the flow from the dam itself will cause a crossing to become untrafficable it’s pointless having a strategy where the primary purpose is to maintain the trafficability of that crossing. It’s the opposite to the situation I described above, where instead of lower objectives governing outflows in the higher strategies, you could have higher objectives governing outflows in lower strategies effectively rendering the strategy obsolete.

I recall when reading through the report that somewhere one of the engineer’s made the point that the strategy would be (in part) determined by the outflow of the dam (despite the apparent contradiction the commission pointed out). I think this is what he might have been getting at. If you’re already releasing water from the dam to deal with risks to the higher objective of protecting Moggill or Lowood (or urban areas) over the course of the flow event, it’s an academic exercise to determine whether the dam level means you’re operating under W1 or W2 (or W3) because making some lower objective “primary” doesn’t impact the fact that the higher objectives would govern releases. If you’re in a situation such as a major flood event I think it’s reasonable to deal with such distinctions after the fact (if at all).

I think there’s certainly a case to be made for improving the manual. However, given it was likely written by engineers for lawyers it’s not all that surprising it ended as much of a confusing mess as the commission’s report on the matter.

The second one was the inquiry into the black Saturday fires. The problems with this inquiry were discussed at length in
this LP post The inquiry reinforced the case for having someone other than lawyers running inquiries in areas where they haven’t a clue about who is responsible for what during an emergency and the practicalities of large scale evacuations during bush fires.
Now this one. Miles better than the Black Saturday investigation but, as Desipus put it so well they didn’t understand what the manual was and wasn’t and the relationship between the manual and what the engineers were really supposed to be doing.

Prioritising an outcome, whether minimising damage to urban areas or protecting the dam wall itself, is a meaningless exercise if there is no actual risk. Where there is no risk to a primary outcome then it would be the other outcomes, presumably the primary outcome of the previous strategy that would effectively guide actions. This means that in many circumstances there would be no practical difference between one strategy or another.

In these terms an examination of the third graph above suggests that the dam was being operated within the manual guidelines given that even engineers cannot predict the future. My only comment is that the flows from the dam might have been raised closer to the max allowed by W1 priorities a bit sooner. However, keep in mind that even engineers cannot see into the future, the high inflows started on Sunday and, until the second surge of high inflows started on Tuesday it looked as though the dam would be brought back to normal levels without exceeding the W1 max flows.

Also not even the Commission says they were in “clear breach of the manual” for 36 hours. What the Commission says is that on the balance of probabilities with no other explanation being reasonable they were in breach. I disagree, but I’ll talk more about that in a post to come.

This is offensive and unacceptable in a blog comment:

Then it seems they updated the operating logs nearly two weeks later, and were very economical with the truth.

You cite no evidence for this assertion. What I know is that two weeks after the event Tibaldi in examining the log of what happened realised that they were releasing too much water on Saturday 8 Jan to comply with the conditions of W2. They changed nothing in the log. What they were obliged to change was their account of what happened in relation to which strategy applied.

desipis, I’ll think about your long comment later. One point. The manual dictates in each strategy except W4 a maximum allowable release, but not a minimum. In W4 they can of course release whatever is necessary to safe guard the wall.

The strategies W1 to W4 only provide guidance as to the relative priorities of outcomes for dam operations. It’s only by applying modelling and professional judgement that one can arrive at a determination as to what action is appropriate. Prioritising an outcome, whether minimising damage to urban areas or protecting the dam wall itself, is a meaningless exercise if there is no actual risk. Where there is no risk to a primary outcome then it would be the other outcomes, presumably the primary outcome of the previous strategy that would effectively guide actions. This means that in many circumstances there would be no practical difference between one strategy or another.

From my general engineering experience, engineering strategies such as the W1 to W4 covered by the operations manual are intended to be used to develop specific operational procedures with limited scope for technical staff or flexible frameworks (including configuring sensors, dynamic software models, processes, spreadsheets, etc) for engineers. The later need to remain subordinate to professional judgement as it’s not feasible to sufficiently consider all possible scenarios to develop more deterministic processes.

Reading the dam operations manual, its obvious the strategies themselves are grossly insufficient to be considered something directly applied during operations, particularly crisis situations such as a major flood. While it might be considered an ideal for auditing purposes, nothing in the manual specifies the recording of the particular strategy selected. In fact the wording and structure of that section of the manual suggest its simply a recording of the current strategies used (potentially based on input from the operations engineers themselves), not a top down specification of the strategies that ought to be used. In such circumstances the strategies in the manual are likely to be gross simplifications of the complex issues of combining a large amount of data into qualitative assessment and forming a judgement about appropriate action. Attempting to consider the strategies as defined in the manual as authoritative in such circumstances would be irresponsible.

The more important issue to record, from an engineering perspective, would be the point when circumstances cause the primary outcome of the relevant strategy to be under risk and begin to drive what actions are taken. It’s in this context that the report at 6pm on the 8th (~12 hours into your 36 hour window) and its reference to the “application of W2″ should be read and understood (see section 16.7.2). It indicates to me that the engineers were already prioritising the primary outcome in W2 (if not W3) but at that stage had made the judgement that the outcomes were not at risk. By “application” I interpret it to mean changing actions (dam releases) to protect outcomes, to apply it in the real world, not changing the priority of outcomes in considering actions.

This is another key point where I differ with the naive “plain reading” and legalistic approach of the commission. It’s also worth pointing out that judging from the report the commissions took a view that is contradicted by the views from 3 of the 4 experts giving evidence. Importantly a breach of the manual doesn’t necessarily mean they breached their duty in a negligence context; although the manual is potentially persuasive in determining what they had a duty to do.

Had they followed the manual then the emergency releases made on Monday/Tuesday would have been much smaller, possibly zero.

Further to whether they actually breach the manual, there is nothing in the manual that dictates how much water to actually release. While all strategies involve prioritising one particular outcome, it’s explicitly stated in the manual all other outcomes must continue to be contemplated. It’s quite possible that (even if they were operating under the ‘wrong strategy’) that operating under the correct strategy would not have resulted in material difference in dam releases given the information the engineers had at the time. Importantly for showing causation in a negligence case, this is a question the commission appeared to not even attempt to answer. The commission’s report doesn’t accuse the engineers of causing damage, it’s accuses them of something akin to an “engineering thought crime”.