How a hydrology engineer prepares for a flood
Think: Sustainability. Ideas in action to protect people and planet. Every Sunday at 11am on 2ser 107.3
Associate Professor James Ball in the School of Civil and Environmental Engineering talks to 2ser’s Think:Sustainability about what engineers can do to mitigate the impact on people and places, and how engineers of each generation are constantly solving problems created by their predecessors. Listen to the interview, which aired on Sunday 5 March 2017.
Host: Jake Morcom, 2ser
Listen online 107.3 2ser (audio length 8.12 mins)
START OF TRANSCRIPT
James Ball: Engineers tend to be a bit more risk taking than scientists who adhere more to the concept of ‘well if we don’t do anything we’re not going to hurt anybody’.
Jake: This is James Ball from the School of Civil and Environmental Engineering at the University of Technology Sydney. James was one of the authors of the Australian Rainfall and Runoff Guidelines, which are the guidelines used across the country to estimate how bad flood events will be. And to give you an indication of just how in detail these guidelines are, they took eight years to write.
James: An engineer will have to make a decision even though they don’t have adequate information to define all the risks and problems associated with that particular issue. The do nothing option is not a viable option.
Jake: And although a lot of time went into writing these guidelines, what James is saying is, more so than scientists, engineers have to act fast. And, because floods tend to come on pretty quickly. However, the problem in acting fast means you have less time to plan. And less planning makes for potential problems in the future.
James: We are solving problems now that the generation of engineers before created by solving the problems that the earlier generation of engineers created, and we will continue to do that.
Jake: But as time goes on, engineering is becoming stronger, and more thought out.
James: Engineering and the management of floods, interesting problem. We know a lot of things that can be done to mitigate the impact of floods, but a lot of it also comes down to how much the community is prepared to pay to mitigate that impact.
James: If we throw in the climate change scenario where magnitudes of events are going to change, because most flood mitigation works are already designed on probability analysis, what is of greater concern is the magnitude of the hazard rather than the probability. What that means in essence is 'how much bigger is my flood going to be'.
Jake: To figure that out, James would look back at flood records over time. The main thing would be to look at rainfall. Look at a particular area, what the trends were, how much rainfall there was one year as opposed to the next. He’d also look at how they dealt with flood events in the past, where they had catchment systems in place, meaning where the extra flood water would flow to. But he’d also take a look at the future rainfall predictions.
Jake: The Australian Research Centre of Excellence for Climate System Science published research in January this year that says with a raise of just 2 degrees celsius in global average temperatures, Australia will see an 11.3-30 per cent increase in rainfall from extreme precipitation events.
Jake: These sorts of predictions could mean not only more rainfall, but more severe flood events. So with all of this mind, what James do with all this data?
Jake: let’s imagine you’re on a team of engineers, builders, and you’re building a new town. And this place, given it’s geography, it’s a place that is prone to flooding. Let’s also say over time, this place, the floods are going to get worse and worse. In this hypothetical, you as the engineer, what are you thinking about first?
James: The first is what is the risk to the people living in the town? And what can we do to mitigate that risk? The second thing is trying to design systems that are or can be expanded with time, as the risk from flooding changes for whatever reason.
Jake: What are these systems?
James: Could be levy banks, around the town to protect water.
Jake: What’s that?
James: A mound of dirt designed at a certain level so that the flow from the river doesn't end up in the town. The Dutch call them dykes.
Jake: Let’s say that is Option 1. What if that option fails, what would Option 2 be?
James: Generally the way a flood protection system works, they work by having some physical structures in place to try and manage flows. But at the same time you are running with models of what that flood event could look like. If it looks like it'll overtop the levee, you will start evacuating the people.
James: Nyngan was an example of that.
Jake: Where’s that?
James: West of Dubbo
Jake: What happened? It overflowed, but why?
James: In this particular case, one sub catchment area with very limited rainfall gauges, and in this instance got a very heavy downfall. It was very unexpected that the rainfall and the flooding coming down the catchment onto the town.
James: The town had already been in flood for the best part of two weeks, this extra rainfall was just enough to overtop the levees.
Jake: Have you learnt from old flood events in terms of how we have systems in place to deal with floods?
James: We are continually learning from historical events. Every event teaches people and ourselves something new. Even if it's just when we had undertake some evacuation, what worked with the evacuation, what didn’t work.
James: If we have designed a levee how it worked, did it work to design or not. Every time there is a flood event we learn something new that can be implemented in the next event, another big advantage of having flood events is that they provide more info.
Jake: Do you feel like in terms of having a system that may have deteriorated over time, that it’s just this constant wild goose chase? Are we ever going to be able to get a system of having a great system and this is the best option?
James: The only way that we will get a system that is inherently going to work over all times is if we stop things happening. And that’s an impossible situation.
James: The big question comes in however, if we do it now, we have a massively over designed system for the current flood regime. If we do it at the end, we're admitting the system has failed all the time. At the other hand, an over designed system ends up with the current generation has a higher level of flood security, than the future generations.
Jake: And so what’s your option then? What can you do to solve that problem?
James: We cannot solve the problem. All we can do is mitigate the outcomes.
END OF TRANSCRIPT