I think the engineers should have software which can do the modelling that you talk about. However it also needs to be able to clearly explain why it makes the recommendations it does and the engineers have to understand how it works, what it takes into account and most importantly what it doesn’t.

Just as importantly it should be seen as a resource that engineers can use (like a calculator) and perhaps even as an aid to remind them what is important during stressful situations, but they should not be expected to just blindly follow its advice. Otherwise you end up with situations like with GPSs where people will go the wrong way up one way streets or lost on bad dirt roads in the country because the GPS told them to do it.

I am going to labour the point, because it is important. I implore you to find an up to date process and control engineer and ask him what his industry is all about.

PID control is all about assessing information and reacting to arrive at a precise point in the most efficient way. It applies to motion control, temperature control, time management, compounding and mixing, even commerce and economics. In CNC machinery you can have many motors operating different axes (dimensions) all working in unison to arrive at a precise point within submicron accuracy. All robotics depend on this calculation.

A PID control function applied to the Wivenhoe/Brisbane River system would very likely have been letting some water go from the dam before the rain began to fall as it would be looking at the precipitation data and making forward decisions based on the total amount of information available. Humans cannot reliably operate in this manner. We can define the process and establish the parameters, but we cannot compute the data with anything like the precision achieveable with computers.

Now I am not trying to be a smart arse here. I do not have a command of this level of computation and programming, but I do know what it can achieve, and I know when to call the engineers and I know what to ask them to do. For my class of industry. All I am suggesting is ask more questions. Talk to more people about this. I would expect that you would be fascinated and you might find another dimension that operates in so many parts of our lives without our even knowing about it.

In the meantime I will miss our conversations now that LP is about to shut down. Best of luck with your business.

You guys obviously know nothing at all about control systems and what they can do. This particular case is one that desperately needs a Proportional Integral Derivative calculation constantly being applied to meet the conflicting needs of water management releases in flood and the water retention needs when in drought. The manual that the engineers were following is a clumsy hamfisted method for achieving what any type of motion controller is doing all day long. The machinery that I use can be spinning at thousands of revolutions per minute one second and pull to zero the next in exactly one particular spot that will be 1 ten thousands part of a revolution in accuracy with absolutely no over run. Every one of my machines has at least three controllers that can achieve that. The brisbane water management is no different in principle, just a lot more independently varying inputs.

This is no massively complicated achievement these days. These systems are all around you. To say that this is too hard to achieve “look at what a mess the hospital pay system is” is just total nonsense that engineers should be ashamed to be espousing. What you’re suggesting might be ok for Warragamba dam here near me where we usually drink the water faster than it can flow into the dam for a decade at a time, but the river system in the Brisbane area is vastly more complex with dams spilling into other dams which then spill into rivers that combine with other rivers. That needs a true proportional total system integrated control which is constantly looking ahead and adjusting flow rates to meet the clearly defined target river levels. And integrated also with the weather radar and tides.

This bucket brigade calculation and discussion that has been happening upthread is fun to do to play with the maths, but in real life should never be done by humans these days. Humans make too many mistakes, and the first of them is to say that the floods can only happen every 50 years. The last time that parts of brisbane was flooded was ith in the life of this blog, and John Quiggins, and that was not fifty years ago. The most important realisation is that there is absolutely no weather certainty from here on in.

John D, the first image in this post shows we got into flood territory three times from October to December 2010.

At the bottom of this site where by selecting Wivenhoe, manipulating dates and hovering the cursor you find that the 1999 flood saw the dam at 135%, albeit from about a 75% start. In the first post I said they dealt with 1,410 GL of water compared to 2,650 this time.

Back in 1893 according to this link there were four fairly significant floods within six months.

The kind of risk analysis you are talking about has to be done, and may be for all I know. Implementing it and selling it to the public will be fun as you imply.

I don’t believe it is possible to create any system that will achieve perfect decisions in such circumstances. You must make decisions given imperfect present information, with unreliable forecasts about an uncertain future. There is no zero risk strategy. Release too much now and you flood people. Release too little now and you may flood many more people later. Judgement is required, and there is not time to brief politicians and defer to them. I think the engineers in this case have been poor communicators, but that does not make them incompetent as engineers.

I also wonder why there has been no discussion about building approvals?. Why had so many new buildings been given planning approval on what were clearly flood prone sites between the 1974 flood and now? After the 1974 flood levels were extensively studied and risks with Wivenhoe in place well known. The flood levels in 2011 were below 1974 levels, yet flooded some new buildings built since 1974 in flood prone locations. Who let new buildings be built in flood prone locations? I thought there were rules for the degree of flood immunity required to permit residential building?