TRANSCRIPT

Inquiry into flood mitigation infrastructure in Victoria

Lakes Entrance — 18 October 2011

Members

Mr T. Bull Ms L. Wreford Mr D. Koch

Chair: Mr D. Koch Deputy Chair: Mr J. Pandazopoulos

Staff

Executive Officer: Dr G Gardiner Research Officer: Dr I Zwart Office Manager: Ms K Taylor

Witnesses

Mr C. Rodda, Managing Director, Southern Rural Water

18 October 2011 Environment and Natural Resources Committee 246 The CHAIR — We now call upon our last presentation from Southern Rural Water and the Managing Director, Clinton Rodda, will be joining us at the table.

On behalf of the Committee I welcome you this afternoon to our public hearing, you are our seventh and last making a presentation here in Lakes Entrance and we thank you for that. I’d just like to add that all evidence taken at this hearing is protected by parliamentary privilege as provided by the Constitution Act 1975 and is further subject to the provisions of the Parliamentary Committees Act 2003. Any comments you make outside the hearing may not be afforded such privilege. All evidence given today is being recorded. You will be provided with proof versions of the transcript in the next couple of weeks. Sorry, not hopefully, within the next couple of weeks. We now look forward to your presentation.

Mr RODDA — Thank you. Thanks for the opportunity. I’ve put together a bit of a presentation to address the terms of reference. Try to provide a little bit of context around what Southern Rural Water does. Our main focus is on flood management is around our storages, in particular Lake Glenmaggie. Talk about the role that we take in flood management, give you a couple of case studies, because you talked about in the terms of reference, your practices around managing floods, so a couple of case studies of the most recent flood that we had and the biggest flood that we had, which was June 2007. Talk about the instruments or the framework that we have around managing floods and then talk about some of the issues and challenges in flood management.

So, a number of the areas in the terms of reference are not relevant to us, things like levees, we don’t hold levees or those sorts of things, so I will focus on the areas which are relevant for us.

Overheads shown.

Just a little bit of context, we have three businesses in Southern Rural Water, we are a rural water provider and we look after rural water management in the south of the state. So we look after 37 per cent of the state, right from the South Australian border, to the New South Wales border, and effectively below the Great Dividing Range. We have three main businesses, an irrigation business, including the Macalister Irrigation District, not too far from here, Werribee and Bacchus Marsh in the west, we’ve got what we call ‘Headworks’, which are our large dams, we have seven of those and I will touch on those in a moment. We have what we call our Groundwater and Rivers Business, which is around licensing and regulated extractions from rivers and streams and ground water across the south of the state. So there our role there is more akin to a regulator rather than a water supply, but we manage to licence conditions. We make our allocations. We also manage farm dams, as well, beyond a certain scale. We have about 10,000 customers or licence holders, about 170 staff spread across those locations, where you can see the little yellow triangle and revenue of around $30 million, in capital, between about $8 and $18 million, so that give a sense of our business.

In terms of our storages, we have seven what we call ‘large dams’ so these are over about 5,000 megalitres capacity, up to about 200,000 megalitres. In the western part of our business, this is the central west area, not too far from , we have Lake Merrimu, Melton Reservoir, Pykes Creek, and Rosslyn Reservoir in the Werribee and Maribyrnong systems. They’re all between about 15,000 and about 35,000 megalitres. None of those have floodgates, so they are all what we call fixed crest storages so they just fill and spill naturally, as the water come through. Most of those reservoirs were empty for three or four years and in the last 12 to 18 months, just about all of them are now spilling, which is rather nice.

On the eastern side of our business, we have one small reservoir called , that’s only a capacity of about 7,000 megalitres and its on the Latrobe system so you can’t really play any role in flood mitigation, because it’s so small. is quite a large storage, it’s around 200,000 megalitres and it’s again a fixed crest storage, it provides natural flood mitigation so because of it’s area and size, flows coming in could be up to 15,000 megalitres a day, what will come out might only be about 8,000 megalitres a day, just because it naturally attenuates flows.

Lake Glenmaggie is the one that has the most interest for the community around flood mitigation. It’s the only storage with floodgates and some capacity to mitigate, what we would say minor or moderate floods. To give you a sense of Lake Glenmaggie and one of the things that we try and do a lot, is educating the community around how big the storage is and how big the catchments are. So we use this concept of the funnel, so you can see the funnel representing the size of the catchment. So you can see Lake Wivenhoe there on the far end, it’s got a very very large catchment. Thompson Reservoir has actually a very small catchment compared to both

18 October 2011 Environment and Natural Resources Committee 247 Wivenhoe and Lake Glenmaggie. Lake Glenmaggie’s catchment actually is about four times the size of the Thompson Reservoir’s catchment. As you can see, the size of the dam which we represent by the beakers, Lake Glenmaggie’s size is about one fifth the size of the Thompson Reservoir, whereas Wivenhoe is very large, both compared to the Thompson and Lake Glenmaggie and Wivenhoe has, as you would know, more than 50 per cent of it’s capacity dedicated to flood mitigation. Whereas, Lake Glenmaggie is solely constructed for irrigation use. So that gives a bit of sense of the scale. What that says is, if we get a lot of rain, then Lake Glenmaggie will fill and spill, that’s just the natural behaviour. It’s a fairly small storage on quite a large catchment.

So we have two primary roles, around floods, one is managing releases and managing the storage level of the reservoir, before, during and after rainfall and also, very importantly, making and managing notifications to various emergency bodies, that happen while floods are actually occurring.

So, we have a policy that is on our website about how we manage levels in Lake Glenmaggie. There are three key things that we think about in managing water levels in Lake Glenmaggie. Firstly, the structural integrity of the dam is our prime focus, because the consequences of the dam failure and the water coming down in one rush would be disastrous. So that’s always our number one priority.

The CHAIR — That’s been strengthened though hasn’t it?

Mr RODDA — That has yes, the floodgates were put in about 50 years ago and there is also very strong anchors. So that dam meets the, what we call ANCOLD standards, the Australian New Zealand Dam Safety Guidelines installed in 1987.

The CHAIR — One in 100?

Mr RODDA — Oh, far greater than that. It would be a one in million type floods. So it’s a very well structured, well managed dam. When we had the big flood it performed as we would have hoped. There was no structural issues at all with that. I’ll come back to that.

Secondly, we also want to harvest water on behalf of the entitlement holders who pay the cost of operating, maintaining the storage. So the storage costs are paid by fundamentally the irrigation district, so there’s about 700 customers that pay for the storage and where possible, mitigate the impacts of high flows on downstream farmland, properties, roads and towns.

Mr BULL — In that order, Clinton? Mr RODDA — Not particularly. What typically happens in a flood is that when we get to around 7,000 or 8,000 megalitres coming out of Lake Glenmaggie, the first farmland starts to become inundated around the river. As more flows go you start to get more and more inundation of land, you then, when you start to get up to around about 30,000 megalitres a day, start to see properties in Tinamba becoming inundated and historically, when you get above 60,000 megalitres a day, the township in Newry starts to get inundated. So that’s the history but Newry might have only flooded a handful of occasions so it’s very hard to be specific about the level that the river will break out and the flooding will happen. But, in November 2007 we kept flows to, and this was after the big flood, to about 59,000 megalitres and the river didn’t break out and Newry didn’t get flooded. Now, that’s now to say it might not happen lower than that or it might be higher than that in the future. But, that’s the target we work to when we can manage flows. The CHAIR — When did Newry last succumb? Mr RODDA — June 2007. Prior to that was 71. The CHAIR — And boy, it got inundated! Mr RODDA — It certainly did. That’s the case study I’ve got here. So the SRW policy sort of sets parameters for managing unseasonably high water levels, so this year is the case in point where we’ve had the reservoir full or almost full, pretty much from the beginning of the year, which is extremely unusual. Lake Glenmaggie fills and spills typically each year, nine years out of ten, but it always gets drawn down very heavily in January, February, March as irrigation demand’s very high. But with rain almost

18 October 2011 Environment and Natural Resources Committee 248 every 2 weeks there was almost no irrigation demand and continued inflow. So, we made a decision consistent with this policy to hold the reservoir at about 80 per cent over the autumn/winter period. I’ll come back to that. We also pre-release water prior to predicted rainfall if we believe the likelihood of rainfall is very high and the storage will fill and spill, and we can again mitigate some of those downstream impacts. Now, that’s quite a judgement and is quite a challenge for us.

The CHAIR — How much do you let go?

Mr RODDA — Well, one thing that we won’t do is create an artificial flood …

The CHAIR — Do you get under, if time allows do you get down to 50 per cent?

Mr RODDA — Oh, it would be very difficult … it depends where the storage starts. So minor flood levels is at about 7,500 megalitres a day, but properties start to get at risk at maybe 5,000 to 6,000 megalitres. So we would rarely go above that in pre-releases

The CHAIR — The limiting factor?

Mr RODDA — That limits that and you’ve got to judge the confidence of the bureau and the rainfall. Sometimes they’re very confident with the likelihood and the quantities, other times it can be much less predictable and models might be conflicting. So, we take into account about a dozen factors that are all listed in our policy, before making a decision to pre-release.

We also have to be up to the levels of the floodgate before we can actually start making any significant releases as well.

When we are at unseasonably high water levels, an analysis comes to me on a fortnightly basis which is then endorsed, which sets the level of the water for the next couple of weeks.

So, a couple of case studies – these are just a couple of examples of how we apply that. So as I mentioned with, we’ve held the storage and lowered it to about 80 per cent since April 2011. Our irrigation season finishes on the 15th May and we have a three month maintenance season and you don’t get a lot of demand from April particularly when it had been such a wet season. So we started lowering the storage there to give us some air space over winter to give us the ability to manage, if we did get big rain in that period of time. In this particular case, had some insight from the bureau that yes, there could be some quite significant rain on the way and there could be more after that, so actually started releasing three days prior. So we built it up from about 3,000 megs a day up to about 5,000 megs a day, before the rain came.

The rainfall was at the top end or maybe even a little bit above what the bureau predicted, so the way the pattern happened, was the rain came during the day, it backed off for a couple of hours and then picked up from 7.00 to 8.00 o’clock and went through the night, as it always goes so through the night. You never get to manage a flood during the day. The peak inflows that we got was about 58,000 megalitres a day. Now, major flood level kicks in at about 32,000, 34,000 megalitres a day, so upstream of Lake Glenmaggie, that’s quite a significant inflow. But, because we held the airspace, we were able to keep outflows down at 28,000 megalitres a day, so that’s a moderate flood.

Mr BULL — Over how long a period was that?

Mr RODDA — See here, this is what we call a hydrograph, so this is what we plot during the event. You can see the grey line here is the inflows into Lake Glenmaggie. The blue is our releases. So as you can see, you’ve got a little bit of a double peak up there, and this is what we call our very nervous period, because you’ve got inflows still rising, you are trying to hold it and you’re trying to make sure you don’t overtop the storage as well, as you can see that line there is the graph going up showing the storage level. So, what we do is we work off these upstream gauges, that give us an indication that a few hours later, we’ll start to see a drop off. So once we start to see them taper and drop off, we start to get confidence that the inflows will drop off a few hours later.

We know the system very well. This one here called Glenmaggie Creek, it tends to peak earlier, it’s much closer to the reservoir whereas, Glencairn, the furthersest one up the catchment, so it tends to be slower, cause it gets

18 October 2011 Environment and Natural Resources Committee 249 all the rain at the top of the catchment, which slowly comes through. So because we’ve had a lot of years of managing this, we can make reasonable judgements as well as what the bureau is predicting in terms of future rainfall and they sometimes give us, if we ask for them, rainfall runoff scenarios, that gives us a predicted peak flow.

So, in that case, that one was very good and it looks quite easy there, but when you are in the middle of a rainfall event, you’ve only got this bit of information here. You don’t have all of this stuff that’s come. We can try and predict that. So that case, from our perspective, that went very well. We were able to hold it at moderate level, we ensured Tinamba didn’t get flooded and we didn’t overtop the reservoir. The reservoir came within about 8,000 megalitres. So, we used 20,000 ML of the airspace.

You mentioned Newry getting flooded, so this was the main one. This was the really big, and we’re talking about almost a perfect storm. We had the bushfires in the catchment, which burnt 95 per cent of the Macallister catchment prior to the rain. We had a really major east coast low, which gave sort of 150 to 200 millimetres of rainfall in a fairly short concentrated period of time. Because of the bushfires, we got rapid runoff because there were no trees there to soak it up and slow it down and we got an enormous amount of debris coming down. So, one of the things that happened early that we mentioned there, well a few hours after the rain was at it’s peak and the flow started picking up, we lost our gauging stations, because literally the rivers ended up three or four times larger, you had trees and logs coming down, we had concrete structures that we found hundreds of metres downstream.

So where we were then, that’s quite challenging because we have to rely on calculated inflows, what’s actually coming in because we’ve only got visual observations maybe from locals upstream. So that becomes a real challenge.

So at that time Lake Glenmaggie had a capacity of about 190,000 megalitres and we had about 100,000 megalitres in storage, so we were only a little bit over half full, at that stage. We had all the rain that I talked about. We made a decision to start releasing water when we reached the 130,000 megalitres, which is where our floodgates kick in. We did a review after 11.00 o’clock and we commenced releases just over midnight. We gradually increased releases to just below major flood level because we took a decision that we didn’t want this water coming down at 3.00 or 4.00 or 5.00 o’clock in the morning, where it would be dark and people just couldn’t, well they would really struggle to manage the scale of the flood that was coming.

The peak was estimated to be over, above 250,000 megalitres and 3.00 am, which is more than twice the previous peak that we’d ever had coming into the storage. We went through our notification processes as we moved through different levels. When we reflected on it, we had actually more than 200,000 megalitres come in, in the 24 hour period. So, more than the capacity of the reservoir, came in, in one day. Interestingly, the whole year before, 2006, that really dry year, we had 60,000 megalitres for the whole year. So, we had 200,000 in one day, 60,000 in one year. So that is a great example of our environment. Our flows were classified, when we had the technically analysis done, as a one in 105 year event. Our storage capacity and our pre-release action meant that we reduced the peak spilling flows from above 250,000 megs to 148,000, which was the peak. Which again, about 50 per cent more than anything that had ever come out of the storage before, or nearly double. The duration of these high flows was reduced from about 14 hours back to about 8 hours. This is the hydro backing this situation, so you can see the flows rising unbelievably rapidly, so this is six times the flows we sort of had in August this year. We gradually kept the releases until basically the reservoir was full at about 6.00 o’clock in the morning. That was our prime strategy, even though we knew we were getting massive amounts in, we were just trying to hold the water back until daylight hours to give people time to respond. Now, in that situation, when you go from fairly rapidly up from about 30,000 to 130,000 megalitres of releases, it’s a great wall of water that’s coming down and that’s what you’re referring to, that hit Newry at that time, as well as Tinamba. Mr BULL — Clinton, with the floodgates being on Glenmaggie, obviously that can deliver significant mitigation benefits to the community, as you’ve just outlined to the communities downstream. It’s the only one of your seven storages with floodgates. If the others had that infrastructure put on them, if possible, I might add, would they be able to deliver similar benefits to communities downstream? Or is this a little bit unique in that area?

18 October 2011 Environment and Natural Resources Committee 250 Mr RODDA — Certainly in , Blue Rock is a similar size to Glenmaggie, it’s a little bit larger, but its catchment’s tiny, so you don’t get much more than 15,000 in some of the biggest sort of recorded inflows. So without floodgates and as I mentioned earlier, it naturally attenuates floods anyway, because of its size. So it would have minimal impact. Narracan already has floodgates but it’s tiny. In the west the storages aren’t that large. Melton many years ago did have floodgates, but it was replaced with a fixed crest, at that point in time. Melton’s lost about 40 per cent of its capacity over its life, so its only 15,000 megalitres in size now anyway. So, floodgates would have a fairly limited impact on that. So, I would say, some benefit, Merrimu is off-stream so that wouldn’t provide any benefit, Roslyn hasn’t been full for a long time, so very limited benefit. Pykes Creek is the other one, but its again at the top of the system, so you don’t get massive flows through Pykes. I’d say limited pretty limited benefit, particularly because you’d be talking about tens of millions of dollars to put floodgates on.

So that was certainly the biggest …

The CHAIR — So how much mud did Glenmaggie pick up? How much, what’s the total capacity of it today, versus what it was prior to this huge impact?

Mr RODDA — So, its lost 13,000 megalitres of its capacity, so about seven per cent of its storage capacity. Now, we believe most of that was because of flood, because we had very dirty water, as you can imagine, coming in, picking up …

The CHAIR — [inaudible]

Mr RODDA — Yeah, all of that sort of stuff. So it lost that seven per cent of capacity. Now we hadn’t measured it for some, but there was no major floods, bushfires and that sort of stuff in the intervening periods.

The CHAIR — How do you recover that?

Mr RODDA — We can’t. The cost of trying to excavate resilt, dredge is just cost prohibitive and we’ve explored a whole host of options to try and see if there’s much we can do, but there is very limited that we can actually do to reduce that.

The CHAIR — Is that the only volume that’s been lost in the …

Mr RODDA — That we know of, yes. We measured it about 12 months after the flood and we will do another measurement in the future to see whether there’s future. But, certainly the water quality improved dramatically over an 18 month period.

The catchment took a long time to recover because the top of the catchment was really burnt hot, so it not only burnt, as you would understand, it burnt even the soil, so it lost a lot of the seed and that sort of stuff and a lot of the topsoil washed away, so its very rocky there now. So, the bottom of the catchment recovered pretty well, but the top of the catchment is still struggling.

There’s probably nothing too significant here, but we have a number of policy documents or that sort of stuff that frames our approach. We’ve got the green book that provides the overall state framework, corporate incident management plan that we have in our organisation. We have dam safety emergency for each storage, flood manuals for each storage, operation and maintenance manuals that provide guidance. We have a number of notifications that we do, during floods and particularly on Glenmaggie, but to the SES in particular, who are the control agency for floods, triggers for notifications to others. We notify the Council in Werribee, which is the historic arrangement. We have a flood warden system in the Macalister, that was set up after the 1971 floods, by the community, so there is a range of people, we contact to trigger levels there, and they have phone trees so they contact each other in the community. Particularly for people close to the river, that move their pumps and their stocks. Now, most of them are very used to managing that, so they do it anyway. But, we keep them up to date with that, so they can manage their way through, and also to DSE.

We put a lot of information now on our websites, so in terms of policy and our role etc. We also, during floods, have live updates in terms of what is coming out of the storages and what is coming into the storages, so they get updated typically every two hours, depending on where we are in the flood.

Ms WREFORD — Updated onto what? 18 October 2011 Environment and Natural Resources Committee 251 Mr RODDA — Onto our website, so if you look at our website, we have a big bright orange button, that says ‘Flood Information’ and you click on that, you can click on Lake Glenmaggie and it will tell you how much is coming and how much is coming out, that sort of stuff. You can also click on that to get automatic updates.

We also do a fair bit of media, as agreed by the SES as a control agency, they say when we can and can’t. But, certainly around Glenmaggie, people know the flow rates and that sort of stuff, so they rely on us, keeping the media up to date.

Our challenges – managing community expectations is the number one. You know, certainly there was a lot of people in Newry that said you should have stopped that flood. We shouldn’t got flooded. But, the reality is if the reservoir is half full and we get a full reservoir coming in, in the next day. All we can do is slow it down. So the expectations about what we can do with particularly Lake Glenmaggie, is something that we work really hard, we put out fact sheets, we’ve done joint flood information drops with the SES, we do a lot of media now, talking about where Lake Glenmaggie is and what our strategy is for the season, and that sort of stuff, so people are aware of that. That seems to be working particularly well in the last 12 months.

The CHAIR — Time lapse between Glenmaggie and Newry?

Mr RODDA — Time lapse? If there is a lot of water coming down – two to three hours.

The CHAIR — It’s on top of you …

Mr RODDA — Yeah, yes. In November 2007 which was another big flood, it was a sixth biggest flood on record, happening just a few months after the June. As we approached what we thought could be something significant, we had a joint meeting with the SES and the local Tinamba and Newry community. We got them in and went through what was happening, what we were doing and that sort of stuff, so they were all really well informed. I think the SES is well on top of the community notifications in our areas now. We work closely with them.

So managing community expectations is important, also managing customer expectations. We lowered the storage after the 2007 flood and we had delegations to our board saying, ‘We’re paying for this water’, ‘You’re holding the storage down’, ‘You’re putting our irrigation at risk’, and our advice was that we believe the storage will fill, but, of course had the November flood after that. So, there is community concern from our customers who pay for the storage about us, keeping the storage level down a bit. But, we’ve been able to manage that to date.

Community knowledge about our capacity to manage flood, builds on what I was saying before. Community behaviour during floods is a major issue for us. Particularly, in the west, but also at Lake Glenmaggie, in the last flood, we had a person that wanted to abuse one of our storage operators and we had to have him escorted off-site. It’s a great sight seeing a reservoir spilling, but we can’t have people getting in the way of our operational people getting out and doing their jobs. You’d be, you probably wouldn’t be, but you’d be amazed at the sort of things that people will do and put themselves at risk during floods. The last one in Werribee, we had someone get on a jet-ski and try and jet-ski down the main street and get on a surfboard and then had to get lifted out by the SES because they got caught. All of those sorts of things happen during floods – no matter how we try and warn people.

One of the real challenges, particularly in 2007 is if you see a lot of rainfall, the rumours about the dams about to break … I must have done between 20 and 40 media interviews reassuring people that the dam was stable, was performing as expected. But, as soon as I do that, two hours later, someone else would ring and there would be another rumour and we would have to come on and do it. So, managing the rumours, that come from who knows where, is a bit of a challenge.

So that’s covered what I want to cover, I think.

Mr BULL — Clint, with the significant drainage network, obviously related to the MID, does that play any role in flood mitigation.

18 October 2011 Environment and Natural Resources Committee 252 Mr RODDA — No, not significant at all. The drains fill during flood events and they slowly drain, they help the natural land drainage, but they don’t really provide any levees or that sort of thing. There is questions around whether our channels provide some benefit, and certainly move water in different directions, they move the way of the channels, so, but, and we try and manage them to make sure they are secure and safe and suffer as little damage during floods as possible. When we are considering projects like MID2030, one of the things that we do is look at, if we are looking to move to a pipeline, well, what impact would removing the channels have off that now.

Mr BULL — Yeah

Mr RODDA — At the end of the day, most of the land, we’ve got easements over most of the land, so the land actually owned by the land-holder. But, there are things that we would work through in major modernisation projects.

The CHAIR — Thank you very much Clinton, on behalf of the Committee, I see your role in flood mitigation really is focused on Glenmaggie period. We also appreciate that in the bigger picture, Glenmaggie is but a puddle, and fills extremely quickly, releases are immediate, the impacts are immediate, so again on behalf of the Committee thank you very much for making the time available and clarifying that situation. We will certainly in your irrigation district, about what, 3.00 pm this afternoon Tim.

Mr BULL — Yes.

Mr RODDA — Very good.

The CHAIR — Something in that order, so we will be on a site visit with the West Gippy CMA so we will certainly have the opportunity to take in what you have put in front of us this morning.

Mr RODDA — Terrific.

The CHAIR — Thank you very much.

Mr RODDA — You’re welcome, thank you.

Mr BULL — Thanks Clinton, excellent.

Mr RODDA — Did you want a copy of the graphics?

The CHAIR — Yes, that would be great, terrific

Witness withdrew.

The CHAIR — I was just going to thank all those who have given their time this morning and to make the presentations. In assisting the Committee, in putting recommendations to the Parliament next May. We had many interesting persons from the total region and at stages in excess of thirty people in the gallery, which I think was similar if not greater than we’ve experienced in the north-west, so I think there is obviously a concern from the Gippsland community’s point of view of what the Committee is endeavouring to achieve and assisting in flood mitigation.

Importantly, I’d like to thank Golf Club for making the venue available for the public hearing in Lakes Entrance today. I was going to thank the ladies from Hansard for recording what took place, but I am very happy to thank the lady, as in our own Karen, for assisting in that passage and also I was just going to announce before we close, that we’ll have further site inspections, when returning to Melbourne this morning, around the MID at Tinamba, which kindly, Tim has put together and we appreciate that the West Gippsland CMA will support us in those inspections this afternoon, as their colleagues in East Gippsland did yesterday.

Thank you everyone for attending.

Committee adjourned.

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