Take me to the River
Join social ecologist and river restoration expert Dr. Siwan Lovett in conversations about the ideas, issues and opportunities that relate to our connections with nature and each other. This podcast offers open, honest and practical insights for us to reflect on in our daily lives.
Take me to the River
Reviving Queensland's Mary River (and Great Barrier Reef) with environmental engineer Misko Ivezich
Questions, comments, feedback? Tap here to send us a message!
In this episode, we’re diving into the waters of the Mary River with environmental engineer Misko Ivezich. With over 15 years of experience at Alluvium, Misko has long been at the forefront of combating river erosion and sediment issues which are crucial to the health of riparian ecosystems and downstream systems which receive their flow. Today, we’re focusing on a successful project on the Mary River, a vital waterway that flows through Queensland and plays a pivotal role in the health of the Great Barrier Reef.
The project, led by Misko, implemented new engineering solutions and extensive revegetation to reduce bank erosion by an impressive 85% during the 2022 floods, compared to past data. This story isn’t just about geological and riparian engineering; it’s about ecological recovery. These efforts have had a substantial impact on native species like the Mary River Turtle and Lungfish, whose habitats are crucial for their survival yet have been degraded over time. Through this project, we see a blend of science, policy, and community engagement coming together to foster a more stable and vibrant ecosystem.
Join us as Misko walks us through this landmark initiative, shedding light on how strategic environmental management can lead to sustainable outcomes for both our natural heritage and the communities of wildlife and people who depend on it.
This episode talks about:
• Overview of the Mary River's importance and challenges
• Discussion on river erosion and past flood impacts
• Importance of vegetation in stabilising riverbanks
• Addressing sediment loads impacting the Great Barrier Reef
• Success of community initiatives in river management
• Engineering strategies used in the restoration project
• Future plans and ongoing work for the Mary River
If you enjoyed this episode, please consider leaving a rating and review wherever you listen to your podcasts.
✉️ Subscribe to our newsletter (no spam, we promise!) to keep up with new episodes of the show!
🎙️ Listen to our other episodes: https://arrc.au/podcast/
🌱 Learn more about the Australian River Restoration Centre: arrc.au
Take Me to the River is an Australian River Restoration Centre podcast production, hosted by Dr. Siwan Lovett and produced by Chris Walsh and Jimmy Hooper, with support from the rest of the ARRC Team. ✨
If you'd like to support the Australian River Restoration Centre and our work restoring rivers and supporting others to do the same, visit our shop for some of the best gift ideas for nature-lovers. You can also make a tax-deductible direct donation to help support our the health and resilience of our rivers 🌱
We acknowledge and honour Aboriginal and Torres Strait Islander Peoples as the Traditional Custodians of the country on which we work, learn, and live. We respect and learn from Elders past, present and emerging, valuing their knowledge, insights and connections to the waterways we love and care for. 🖤💛...
The Australian River Restoration Centre is a charity, restoring rivers and helping others to do the same. You can support our work by checking out our shop, where we have some of the best gifts and conversation starters. To help raise awareness about restoring our rivers, We've worked with South Australian-based artist Nina Rapina to design mugs, tote bags, T-shirts, hoodies and jumpers, all featuring our native Australian wildlife. Best of all, your purchase makes a real difference. All proceeds go directly towards our work for restoring rivers and protecting these treasured species. If you're feeling generous, you can also make a direct, tax-deductible donation at our website. Just $10 helps us buy buckets, gloves and spades for riverbank planting, which helps promote clean drinking water. $25 helps us buy five native river-loving plants. That provides habitat and refuge for platypus, frogs, fish and birds. All donations of any amount are gratefully accepted and they help us achieve our mission of protecting and restoring Australia's waterways. Visit arcau forward slash donate. That's A-R-R-C. Dot A-U. Forward slash donate to learn more. Hello and welcome to Take Me to the River where we share stories and inspire hope with extraordinary people who care for our rivers. I'm your host, Dr Shu-Anne Lovett.
Siwan:In this episode, we're diving into the waters of the Mary River in Queensland with environmental engineer Mishko Ivozic. Mishko has been at the forefront of combating river erosion and sediment issues, which are crucial to the health of riparian ecosystems and the downstream rivers that receive their flow. Today, we're focusing on a project Mishko has been working on on the Mary River. The Mary River is particularly important because its flows go out onto the Great Barrier Reef and it has been the source of significant sediment loads going out to this very precious ecosystem. This project implemented new engineering solutions and extensive revegetation to reduce bank erosion during the 2022 floods.
Siwan:This story isn't just about geological and riparian engineering. It's about ecological recovery for threatened species Mary River Turtle and the Mary River Cod but it's also about a community recovering from the impacts of drastic flooding that saw their river literally washed away before their very eyes. Join me now as Mishko takes us through this incredible initiative. Well welcome, Mishko. It's wonderful to have you joining us today to talk about a river that I really love and haven't been to for quite some time the Mary River up in Queensland. Can you tell me a bit about how you've come to know this river and why you're interested in rivers?
Misko:I'll go back to my interest in rivers first before I get to the Mary River. So I'm an environmental engineer, mainly work in river management, so around river processes and river river rehabilitation. I've been doing that for about 15 years, currently based in northern New South Wales, but my work is all up and down the east coast and a little bit overseas. So how I've got into this work, I guess I sort of fell into it in many ways. Obviously I love rivers and I've spent my childhood playing in creeks and streams and the North Island, new Zealand and the base of the Mount Lofty Ranges in Adelaide. But I never really imagined you could make a career out of it playing in creeks. But I have managed to. So yeah, so I basically got to it by studying environmental engineering at Adelaide University but again I didn't really know where I was going to go with that degree. I mainly chose it because I was good at mathematics and I cared about the environment and the natural world.
Misko:Finished that degree and still didn't really know where I was going to go with my work, I started a PhD for one year at Adelaide Uni and that was in sort of urban stormwater management and again didn't really enjoy that probably didn't have the maturity to do a PhD in my sort of early 20s.
Misko:I applied for jobs in Melbourne, had a friend moving to Melbourne, applied for jobs and got a job at Alluvium Consulting, which was a just a freshly new environmental consultant, new specialist specialized in river rehabilitation work, so went over there and I guess, yeah, those first formative years at Alluvium really developed my interest in rivers and river processes and river rehabilitation, and so how I got to the Mary River was we're doing quite a lot of work from Melbourne in southeast Queensland after the floods that hit that area in 2011, and so I relocated up to southeast Queensland at that time to help with all those flood recovery programs. And again there was another flood in 2013. And, yeah, I went out to the Mary River one day. I was introduced to this amazing river system, which I've now been working on for well over 10 years.
Siwan:I love the fact that you say that you know you were studying and had no idea where you were going to end up, because I was exactly the same. I did not expect to be running a river restoration centre at all. There's something about rivers, though. They just get to you and having the opportunity to work with them and the people that love them is fantastic. I was chatting to Mishko earlier because I actually remember the Mary River from my time in Land and Water Australia, which is now 20 years ago, and we had some great projects on the Mary River, with some farmers who were fencing off their stock and doing regeneration work. Tell me about a site that we actually worked on that now you've actually gone and worked on, where we'd actually put some structures into the river to try and control sediment.
Misko:Yeah, so this is a site up between Kennedale and not between Kenilworth and Connedale, and you put in some structures in the late 90s with Brad Wedlock from the Mary River Catchment Coordination Committee, who I still work with very closely, and so that was about putting in some structures along the toe to protect the bank toe from erosion and then revegetating the upper bank, and it's largely been intact over sort of 20 years later. But the middle of the section has become quite badly eroded in recent flood events and so we recently went in there as part of some funding for protection of the Great Barrier Reef and the Great Barrier Reef Foundation and rehabilitated sort of 200 metre section within the middle of that project area to mainly protect the revegetation works downstream that were planted in the late 90s that are doing really, really well. So you know really mature trees now. So it's great to see.
Siwan:It's a wonderful part of the world because the trees actually grow quite quickly there. We had a project in the Mary River and then we went to look at one in Tasmania and those trees were still very little.
Misko:So it's great. You're very right.
Siwan:It's a very sort of lucky sweet spot on the east coast of Australia nice, warm temperature, lots of rays, and things grow remarkably quickly they do indeed, so tell me a bit more about erosion for some of our listeners who might not understand what that actually means for a river in terms of sediment, and particularly what can happen with floods in systems like this. So you mentioned, in 2013 there was another big flood in the Mary River. What happened to the river as a result of that flooding?
Misko:Erosion is an essential process in river systems to start with. So we often think of erosion as a really really bad thing and something that needs to be managed, but it's a very natural process and it's fundamental to a lot of the landscapes we see within our catchments All the hills and floodplains and everything that's formed from either erosion or deposition over sort of thousands of years, and so an alluvial river is constantly eroding and depositing sediment and that helps form floodplains. It's really really important for agriculture and growing food. For us. It helps scour out pools which are really important for maintaining our native fish communities and our more broader fisheries as well. But often when we, you know, change something within our catchments and river systems, we can sort of change those erosion and deposition processes and sort of mess. They're sort of in this fine balance, if you like, and if we mess with things in the catchment or the riparian zone, we can tip the balance either into a really erosional phase where you get really much more erosion, or a depositional phase where the channel just fills up with sands and cobbles and gravels, and so I'll give it a give you. One example is the removal of riparian vegetation. So vegetation helps stabilise riverbanks and provide hydraulic roughness that basically slows down velocity and flow up against the riverbank. And when we remove that vegetation from the riverbanks there's nothing to take up that excess flood energy or stream power and we start to see erosion of our channels and widening of the channel, causing loss of floodplains and loss of those really deep pools that are so critical for our in-stream biota.
Misko:And I guess another one in the Mary River which has caused a whole lot of issue has been sand and gravel extraction.
Misko:So the Mary River was basically a sand and gravel mine for the latter part of the 20th century. Literally hundreds of thousands of cubic metres of sand and gravel mine for the latter part of the 20th century and literally hundreds of thousands of cubic meters of sand and gravel were taken out of the river to support the urbanization of the sunshine coast. And what that does is it destabilizes the riverbed and it steepens up the bed profile, leading to an increased slope and faster velocities and more stream power. And again, when you get those big flood events, water travels a lot more faster. Particularly once you go vegetation on the banks, you get really high rates events. Water travels a lot more fast. Particularly once you've got vegetation on the banks, you get really high rates of channel erosion and channel widening and a loss of all those really important habitat features, like our floodplains and our pools, that are really important for, yeah, ecological communities as well as our agricultural communities as well.
Siwan:And I think it's one of those things that you know humans, we like to fix stuff, and so when we think about floods, for some people it's really a license to get the water away as quickly as possible, but that actually then means that the water creates more damage because it's not allowed to slow down and go at a lot less speed and a lot less destructive power when you actually allow it to disperse more. So with a catchment like the Mary River, so the gravel and sands has been reduced, it's still got sediment coming in, and then it gets this whack of water coming through. What happened to the river? Like did it? Were there big chunks of the bed falling in, or was it just filled up with sand? How did it look after that flood? That caused people to actually say, okay, we've got to do some more work here.
Misko:Yes, the main reach, which we've focused our recent sort of work on, is around the Kenilworth area, but since then we've obviously been working across the whole Mary River as well, but I'll just describe the changes around that Kenilworth reach where we did our original plan and the majority of our work.
Misko:So what we can gather from you know, historical information of the channel, so old surveys that were done in the 1950s, and historical area imagery is that the channel bed's lowered by about two metres, from what we can tell, since the 1950s, and its channel width has probably doubled or in some cases tripled in width.
Misko:So it might have gone from 40 or 50 metres wide to well over 100 metres wide in some sections, and the bed's lowered a couple of metres as well.
Misko:So when I went out there after the I'm happy to put up some photos as well when I went out there after the sort of 2013 flood event, it was just, you know, sheer vertical cliffs of 10 metres high of loamy, highly erodible sediments just collapsing into really turbid water with high sediment loads working its way through it, and obviously it's lost all those really important in-stream habitat features, like the pools, which supports a pretty endangered species in the Mary, like the Mary River Cod and the Mary River Turtle, and so it's basically a basket case. After that 2013 flood, it was one of the most degraded rivers in Australia. I think it had been called at some stage in the late 20th century and at that time it was just when the Great Barrier Reef was coming into focus as a key sort of issue, and it was probably one of the most unstable river reaches within the Great Barrier Reef marine park catchment areas.
Siwan:So a pretty sad and sorry state. And, listeners, we will put some photos up so that you can see that poor old river after the flooding. The connection with the reef I think there has been a growing awareness about the fact that's what comes through our estuaries. Now onto the reef. You know people have seen photographs of plumes, but how much sediment are we actually talking about here, like, does it really make a huge difference to the reef? What's your view on this?
Misko:Well, it's different, for every catchment where the sediment loads are coming from, from the Mary River catchment, the main source to that area of the lower, the southern portion of the Great Barrier Reef. It's a very southern catchment with the Great Barrier Reef Marine Park Lagoon and it's yeah, the stream bank erosion has been estimated to be. You know, close to half of the fine sediment load getting out to the reef is coming from channel erosion within the Mary River catchment.
Siwan:Wow, that's an enormous amount. Yeah, so that explains having some support from the Great Barrier Reef. Was it the conservation fund you were talking about? I can't remember the exact name.
Misko:Great Barrier Reef Foundation. Yeah, they invested as a priority. I couldn't tell you the exact load off the top of my head, but it's probably tens of thousands of tonnes every year of fine sediment coming out the Mary River.
Siwan:And so when you're talking fine sediment, is that like tiny granules of sand, like just for people to have an idea about what you're meaning by fine? No, it's even tinier than sand.
Misko:It's the clay fraction, so there's clay silt and then sand as a sort of sediment classes. So it's a really, really fine stuff that stays in suspension. It doesn't really settle out within river systems very easily and is transported in suspension out into the ocean environment and then eventually settles in the ocean environment and in particular for the Mary River, it goes out in the Great Sandy Strait, which is near Gary or Fraser Island, and so all that fine clay particles sort of settle down in that area and they're famous for their seagrass beds and their dugong sort of areas and all that fine sediment smothers those ecosystems. Yeah, so when you get the erosion you also get the sand particles as well, but they generally get deposited out in the river network and they don't make it out to the ocean environment.
Siwan:Oh, that's interesting. So you actually get a range of sediment that the river's carrying, but it sort of drops off the bigger particles before it gets right out. I didn't know that. So when we see those big plumes, it's that fine suspended stuff that we're often seeing.
Misko:Exactly the coarse stuff still has an impact, particularly on the river system. So the sands and gravels and the coarser things are more readily visible when you're out looking at rivers. That fills up pools and has impacts on in-stream habitat diversity, but it's the fine, really fine clay fractions that's more important for the management of marine environments.
Siwan:So, when it came to designing something to address this erosion in the Mary River, do you take the sediment profile into account? Does that impact on the sort of design that you might develop?
Misko:Yeah, definitely. So you're considering sediment being moved through the river, on the bed of the channel, but also the sediment within the banks, and what sort of profiles needed to stabilise the vegetation, and then sort of surface treatments as well as particularly sandy materials. All that stuff definitely needs to be considered.
Siwan:So let's talk specifics then. What did you actually do with this project of yours on the Mary River?
Misko:Okay, I'll go back to right at the start. So you know, I went out there after the 2013 flood event and primarily with Brad Wedlock from the Mary River Catchment Coordination Committee. As I said, it just looked like an absolute basket case really of a river and probably at that time probably didn't ever think you were ever going to be able to do anything to address the issues that you're seeing in that river. That's how extreme the problems seemed. However, we thought I said we need to come up with some sort of plan.
Misko:So we got together all the key stakeholders that had an interest in the river, so Burnett, mary Regional Group, another regional group working in catchment management in the area, sq Water, who's a local water authority who supplies water to the township of Kenilworth, and Sunshine Coast Regional Council, which is the local government. We all got together and we said let's come up with a plan for this particular stretch of river, and I guess the key objective was to try to increase the resistance of the river so it would be able to withstand to the floods of a similar magnitude that occurred in 2013. So in that flood event, some of the banks migrated over 50 metres, taking out massive areas of really great agricultural floodplain land and just washing it down the river and out to the reef the reef. But there are also some other obviously ecological outcomes we wanted to get so by getting increased vegetation on the banks and, over time, returning some of that in-stream habitat diversity that supports those threatened species I mentioned earlier.
Siwan:It must have been absolutely devastating for the local community to see that happen to their river, because I just know from my working in the 1990s there there was so much being done to try and save the Mary River Turtle and the Mary River Cod. So, yeah, you must have been dealing with a highly traumatized community. Is that what it felt like to you?
Misko:Yeah, yeah, definitely, and the Mary River Cattle Conservation Committee are really great in that aspect of you know, talking to landholders and sympathising with them and building those long-term relationships. But, yeah, after that particular flood but all flood events, you get really traumatised communities when they see such drastic change, the changes in the river and their land as well.
Siwan:So, yeah, continue on. I'm fascinated. It just struck me that, wow, that must like 50-metre migration, that is a lot of land to see disappear before you, and 10-metre high banks as well.
Misko:Oh wow, 50 metres by 10, the amount of material that's coming out is huge. Yes, we came up with a plan. So obviously the key goal was we wanted to get really good native riparian vegetation growing on the banks and in the channel and on the floodplain again, and that's going to provide the long term resistance to erosion but also all the other ecological benefits we want as well. We have some problems or some areas where the banks were vertical and 10 metres high and some of the flood velocities on those outside bend areas were really really high. So planting trees wasn't going to be feasible by itself. So we had to come up with some other approaches to support the revegetation works. And that's when we look at sort of soft engineering approaches reshaping banks and putting in logs or pile structures along the tow to slow down the velocity.
Misko:So as an engineer working in rivers, I guess my philosophy is always just trying to do the minimum amount of engineering that's required to support vegetation to get established. So you want the vegetation to do all the work and be the long-term mechanism that holds our river channels together. But you need a little bit of engineering sometimes to help it along the way, but not not too much. We're going to be rock lighting riverbanks or over engineering systems, um, when they don't need to. So a lot of its analysis is looking at the flood, hydraulics and the geotechnical properties and coming up with just the minimum amount that you're comfortable with putting in the system just to help hold it together and for the first five to ten years to allow the time for the vegetation to get established.
Misko:So with this particular system we identified areas where the velocities were too high or the banks were too steep and we came up with some approaches to reprofile the banks back to a more stable gradient, sort of one is to three, to allow access, to revegetate those banks.
Misko:And then we installed sort of timber piles along the tow and those timber piles act like an artificial forest for the first five to ten years and slow down the velocities up against the toe of the bank and allow sediment and seeds to drop out in that area as well and regenerate that lower bank zone. And it just provides enough resistance in that critical area for the first sort of 10 to 15 years, which then allows the vegetation to establish on the upper bank and at that point it doesn't really matter if the timber piles rot away because we've got enough vegetation and roughness and root reinforcement in the lower bank, it can help resist those really big flood flows and return to more natural rates of erosion. We'll still see that erosion and loss of some tree material that will go into the river and provide habitat, but it's nothing like the extreme erosion we saw in the 2013 flood event, where some of these banks were migrating 50 metres.
Siwan:So why do you choose to work at the toe of the bank rather than just focusing on the top?
Misko:The highest forces in a river are down close to the bed of the river.
Misko:So if you've got a big flood flow going, this reach is greater than 10 metres deep and so the greatest force is right at the base.
Misko:And the greatest force in the bank is obviously at the base of the river or the bed of the river up against the toe of the bank, and that's where you get the maximum force exerted on the bank and that causes what is called bank toe erosion or fluvial scour along the toe, and what that can do is that steepens up the bank profile over time until it gets to a critical point and then it has gravitational failure.
Misko:It comes down to what's called bank slumping. So a toe erosion or scour from the velocity high velocities of the toe steepens up the bank and then you get slumping of the upper bank material. So a key thing to stop that process is to provide enough resistance at the toe. Toe steepens up the bank and then you get slumping of the upper bank material. So key thing to stop that process is to provide enough resistance at the toe, where the forces are highest, and then that will protect the stability of the upper bank area where the actual flood forces are less in the upper bank and the erosion there is generally due to that gravitational mass failure or bank slumping process.
Siwan:It's really interesting, isn't it? Because, yeah, we focus on the toe of the bank when we're out working with farmers as well, but I've certainly been on stretches of river where you've got a really steep bank and there's one tree just hanging on for dear life and the farmer will say that tree's what's causing that erosion. You know it's causing the whole thing to fall in, and I'm going that tree is the only thing that's keeping it up. Can you explain a bit more about that, because it's counterintuitive for people. They see a big tree and they think, oh, that's going to fall in and pull the bank in with it, but in actual fact, that tree and its root system is holding it together.
Misko:Yeah, you're right, and it's all the other area around the tree that's eroded.
Misko:It's left that tree standing by itself and the reason that tree hasn't been able to hold all the bank together is because one tree can't do all the heavy lifting.
Misko:You need an army, I guess, is one way of looking at it.
Misko:So you need lots of trees and shrubs and ground covers help holding the bank together, and each of those three things I mentioned the ground covers, shrubs and trees do something slightly different in terms of erosion control.
Misko:So your grasses and your ground covers lay flat and help armour the underlying alluvial sediments from erosion, provides a sort of filter layer, if you like. So that takes all the high-velocity flow force on the foliage of the grass and the ground cover, protecting the erodible sandy or clay material underneath your shrubs, which have lots of branches and physical elements. And physical elements are highly sort of malleable to move and get knocked around in flood events and what that provides is a lot of frictional resistance or hydraulic roughness helps slow down the velocity, just because the sheer surface area of all their little small branches and bits of foliage and then your really, really big trees might not have a huge impact on the flood velocities because it's just a trunk, but it's their root system, is what's happening underground, and those deep roots and it's almost like they're providing the reinforcement in the bank prover like almost like steel and concrete reinforcement. Those root systems provide that really strong tensile strength and reduce that mass failure or slumping process I talked about earlier.
Siwan:Yeah, it's a classic one, because you've also got to stop yourself from saying you're wrong, because you kind of need to. Well, my approach, anyway, is to ask questions about why they might think that and where they've you know. So you actually are not saying you're wrong. It's more about saying, well, actually, research is showing this or this or this, so, yeah, it's a better way to go. In fact, I do remember very clearly thinking about the sediment.
Siwan:I was up on a sugar farm in Innisfail and I was being taken out to this farm because the guy I was going to see, a guy called Tom, was known to be a very good riparian manager, and he took us down to his riparian zone and he had all these individual trees beautifully paced apart. He was mowing around all of them, so it all looked very it was like a garden, and I thought, okay, so that's interesting, that's the interpretation of what a healthy riparian zone looks like. And I left behind him a magazine that I used to produce at the time called Rip Rap, and it had a whole article on needing at least a five centimetre high swathe of grass to actually capture sediment. And so the next day I went back and he went. So, shu-anuan, I read that riprap article. Are you saying that I need to stop mowing as?
Siwan:much I said yes, I am, but it was a much better way of going about it. And we also then had the discussion about you actually need grasses and you need shrubs and you need trees, and it's that idea that somehow that's going to look messy and it's not going to actually do as well. Did you have any resistance in the community to your approach to this type of erosion control, or were they sort of fairly used to that idea? Did they want more? Did they want concrete? Was that going to make them feel safer?
Misko:Every landhold is a little bit different, but I think at this stage we'll be talking about this project of the mary river. At that stage, um, yeah, there was a lot of uncertainty, I guess, um skepticism even, but I guess they had to try something because they'd seen what happened from doing nothing. But moving forward now and seeing the outcome of the, you know there's been a massive change in the community and everyone wants more of this type of approach and, yeah, I've convinced many people of the benefits of this type of work and the benefits of vegetation more generally within the riparian zone.
Siwan:Oh, that's great, because I have had people say we just need green concrete. That's the environmental alternative is to go green concrete. So let's fast forward then to 2022. There were big floods down the Mary River again and I know that you've recently presented some work to show how your approach has actually managed to withstand that flooding. What were you particularly pleased about in terms of how the river was looking post the 22 floods?
Misko:I might just go back a bit there in time, if you don't mind. Just before what happened before the flood event.
Misko:Because, yeah, so we developed up the plan At the time, we never thought the plan would get funded. So that was probably the. Quite often as consultants, you get paid to develop up plans and they sit on shelves waiting for funding and they never get funded. So, given the scale of works that were required within this reach, we probably didn't think you know what we were recommending would ever get funded. But then the first funder was SEQ Water, who their water offtake for the town was going to be taken out in the next flood event if they didn't do something to the bank upstream, the section of bank just upstream of that bank. So they funded the first project and we did that about 2015, which was a major bank reshaping project and installation of pile fields, as I talked about.
Misko:Sunshine Coast Council got the parts of the plan and they didn't want to really invest in the engineering or the civil part of works.
Misko:But they jumped at, you know, just going out and fencing and revegetating all the lower risk areas where the bank was, you know, more gently sloping and didn't really need any engineering or reshaping work. So they just went to those sort of areas and engaged with landholders and implemented the fencing and did the planting works and, as I said, this was a time when the Great Barrier Reef funding was really sort of come online as well, and so, you know, about five years ago, we got funding for all the other really eroding, steeper areas that needed massive earthworks and engineering works to support the revegetation. So, slowly but surely, a whole lot of different funders came on board. So there was the Queensland government, there was the federal government, so, basically, this plan was funded for a whole range of different stakeholders over a series of years, for a whole range of different stakeholders over a series of years. Obviously, most of the work was implemented just before the 2022 flood events which came through the system.
Siwan:That's a great great approach, though, because you had one plan and one vision, and then people could say, well, actually, I'll do this bit, I'll do this. So were you sort of the constant in that, in terms of being the group to which people look to, to know, okay, if I do this bit, it's going to work or it's going to fit in with other stuff that's going on?
Misko:with the other stuff that's going on. So quite early on in the process we formed a consortium between myself and Alluvium, who I work for, and the Mary of a Catchment Coordination Committee and the Burnett Mary Regional Group or BMLG, and so we formed a consortium and basically we catch up, you know, every fortnight or so, and we talk about the current projects and we talk about upcoming funding opportunities we could leverage to invest in the Mary River catchment. And so that plan was, you know, a key piece of that exercise to look for funding opportunities. And when you're applying for grants and you've already got a fully-fledged plan, you're ready to go on some other projects that have been successful. It's, you know, looked on much more favourably by people um handing out money for this type of work makes a huge difference.
Siwan:And it also helps, I think, when people move on, if you still have a plan that a new person coming in can refer to or get locked into a new initiative. But I know there's so much great work being done around australia and then when one crucial, crucial person leaves, it just falls over and then you've got that rebuilding process. So I'm delighted to hear that, because I do care about the Mary River, as I do all rivers, of course. What about ecological surveys? You know, my big thing about the Mary River turtle, of course, is it's a bottom-breathing turtle, so it's got a cloaca. If no one has seen or heard that word before, you might not want to see it. But yeah, I always think about the bottom breathing turtle, which is the Mary River. So what have you learned from the ecology?
Misko:With ecological surveys. A big part of what we need to do is part of this work. So I don't necessarily deal with that directly, but Mary River Catchment Coordination Committee they're really on top of doing those surveys before we do works and while we're doing works as well. Because quite often what happens when we are reshaping or reprofiling these banks? The Mary River Turtle loves nice sandy nesting environments so we turn a vertical cliff that's no good for Mary River Turtle habitat into a nice reprofiled sandy bank and they sort of run for it and want to do all their nesting there.
Misko:But unfortunately we're also trying to install piles and do other things. So it's quite often during that early construction phase we've got to put up exclusion fences for that month or so just to try and stop them getting onto the bank, to enable us to finish the works and do the planting and then they can go for it. After that they can create a bit of a turtle sanctuary for them. With this nice, gently sloping bank they can climb up nice and easily compared to the vertical bank. So it does take a few headaches during construction trying to manage those turtles trying to get up onto these banks and trying to limit their access while we can. But yeah, over time we're improving their habitat, providing those more gently sloped banks that accumulate sediment and sand, which they like for their nesting.
Siwan:It's almost like you know you've got one of those billboards coming soon.
Siwan:You know like don't try now, in terms of real estate in the river, this is going to be the premier estate, but you have to make us build it first. And what about the cod? Because the cod needs deep holes. Some of these structures that you're putting in not only would be holding back sediment or making it more structurally sound, but is it also enabling some scouring to get back a bit more of those deeper pools that fish like yeah, it's a bit of a slower process for the cod.
Misko:Because the Mary River has got so wide over several decades it's lost the ability to maintain those deeper pools.
Misko:And basically how a river scours out and maintains pools it has to have a lot of roughness on the banks.
Misko:You imagine really density vegetated river banks. It forces flood flows between the vegetation and that helps scour out the bed and maintain those pool environments. And as the river gets wider and wider you don't have necessarily the force within the bed of the channel to scour out those pools and maintain those deep areas. So unfortunately a lot of the Mary River is a very shallow river now and a lot of those deeper pool areas where the cod still remains are in the tributaries. So over time as the vegetation establishes on the banks and encroaches more and more in the channel and on the bars, hopefully over time you know that's probably going to be decade timescales we can get enough roughness in the channel back again that we can start to scour out an insect low flow channel a bit more and provide that bed diversity and habitat for the cod. But it's a bit slower process. It's going to take decades unfortunately to undo all the damage that's been done to bed diversity in the Mary River.
Siwan:Yeah. I think, though, that really, if we think, decades is a long time, it's not actually that long in the life of a river. So I've been doing some work with traditional owners, who have a 100 year plan for a particular river, and I'm thinking that's actually much more sensible, because we do place a lot of pressure on ourselves to get things done quickly, but nature does respond more slowly, but probably with a longer term view in terms of it being there for much longer than we're around. I'm interested with the 2022 floods. What happened in terms of the amount of sediment that was moving, and were you able to, you know, report back to the Great Barrier Reef Foundation that you'd actually managed to stop some sediment getting out onto the reef?
Misko:So 2022 was a wet year across the east coast. We had a series of smaller floods in the Mary River, which culminated in the biggest flood in sort of May 2022. And so this through the REACH we worked on, I think. The flood peak was well over 10 to 12 metres high and it was basically the biggest flood that had occurred in the system since the 1990s, so well over 30 years. It's much bigger than the event in 2013, which instigated all these projects, and so I think the flood event occurred over a weekend, so it was a nervous weekend for myself.
Misko:I was checking BOM constantly on my phone and looking at river heights and rainfall and monitoring all the gauges and imagining all these structures and things that I'd put in the riverbed that were now 12 metres underwater and imagining what was happening to them and how the sediment was moving through them. But I was pretty nervous because obviously we'd implemented millions of dollars' worth of rehabilitation works in just the years before this flood event. So obviously you're really quite nervous. What's happened to all that investment and hundreds of hours of hard work that you've put into it? And so I didn't get out there for a few weeks, but the few days after the flood, um Brad from MRCCC, um his colleagues, colleagues did a walk down the reach and I remember being at work he was sending me text messages and photos of each section to see how it stood up. Suspense was killing me as he walked around every bend to see what we were going to see.
Misko:But as the photos kept coming in, I just got a bigger smile on my face because everything looked great and the trees were still there.
Misko:They were banged around a bit, but they were largely intact, and some of these banks that had migrated 50 metres nearly 10 years earlier were basically largely intact, with very little deposition.
Misko:And then he kept sending me these photos of his gumboots sinking into all the silt that had been captured on the banks as well. So not only had we stopped erosion on the banks, but all the vegetation and roughness we were adding was capturing sands and silts on the bank as well, so they were basically accumulating sediment. So what had been really big sediment sources were now becoming these sediment accumulation zones and capturing sediment on the banks. So everything held up really really well. It was managed to get out there and since then we've done a whole lot of more quantitative analysis and collected LiDAR data of the reach and compared the change in the bank morphology before and after the flood. And so yeah, we estimate, you know, sort of effectiveness of the works is, you know, in the range of sort of 80 to 90% sediment reductions going from the reach and out to the Great Barrier Reef. So really really highly effective projects at stopping sediment getting out to the reef.
Siwan:That's incredible. What sort of? Have you got any idea of sort of tonnes that might mean more to our listeners? I mean, the percentages are super impressive. Yeah, so from this, particular breach.
Misko:This is about a sort of four kilometre sort of breach we primarily did this analysis on. We're sort of basically stopping 20,000 cubic metres of sediment in total each year on average and going out to the reef. That's, you know, assuming about half of that's fine sediment that gets out to sort of the reef environment, so sort of 10,000 cubic metres. So that's close to almost, you know, 15 to 20,000 tonnes of fine sediment going out to the reef each year. That we've managed to stop from these works. That's sensational, that's so good. I can just imagine you, you know, seeing gumboot photos and smiling more and more and people going.
Siwan:Why are you excited about a gumboot in?
Misko:sediment River engineers get excited about strange things.
Siwan:They do indeed, they do indeed. So what are you doing in terms of ongoing work with the Mary River? You said you've formed this consortium, so you're obviously still talking. So what are the plans for the Mary River going forward?
Misko:Yeah, we're still talking and it's a big catchment.
Misko:There's a lot of areas that still need similar sort of management and interventions. We just finished the four-year program with the Great Barrier Reef Foundation, which has been another highly successful project, which did one project in the reach I've been talking about, but also did projects more broadly across the whole system from Conondale down to Tyro, and that program stopped about 26,000 tonnes of fine sediment annually getting out to the reef. We're also working on some disaster recovery reach scale projects following the flood events in 2022 in the Mary River and the tributaries, and we're just about to kick off another round of Australian Government Reef Trust funding in the Mary River, which is another sort of five or six year program of investment. So there's a lot of money that's been invested in repairing the Mary River over the last five to ten years and looks like it's going to be ongoing investment for the next five to ten years as well. So, yeah, really, really exciting and hopefully we can get a really much more improved outcome for the Mary River than was 10, 20 years ago.
Siwan:Oh, that's wonderful, Really good. So, listeners, we will put some photos up there. But you know, what I love most about this story is that you know it obviously had heartbreak and trauma, but you actually have managed to. You know, work with the community. It's obviously been a big community initiative to actually get this river starting to come back on what we often call a recovery trajectory, which is wonderful. And you're still smiling, which is wonderful, so you're still excited about what's happening. This is the great thing about working in rivers. I think Nature just gives you back so much. I mean, at least I think it does. I don't know whether you're the same, but it is for me.
Misko:Yeah, and every river, every reach, everything's different. That's the thing that keeps it interesting as well. The catchment area is different, different. That's the thing that keeps it interesting as well. Yeah, the catchment area is different, the geology is different, the ecosystem different. So each different section of river, each river, you're working. It's a different sort of story, a different puzzle to try and solve.
Siwan:So I love that. Different puzzles, that's exactly right. Well, look, as we come to the end, we have three questions that we always ask our guests. So the first one is do you have a favourite river or body of water? It doesn't have to be the Mary River, you might have somewhere else. That's special.
Misko:Well, probably from a working perspective, the Mary River is probably the one I've done my most work in. But seeing you said body of water, I'm also a keen surfer so probably the ocean near where I live in northern New South Wales is probably a favourite body of water For me anyway. There, the ocean near where I live in northern New South Wales is probably a favourite body of water for me anyway, there's a bit of time out and surfing and recreation. But from a work perspective the Mary Rivers is probably a special spot for me, just the amount of volume of work I've done in it. But I've worked on hundreds of rivers across the East Coast and everyone's got a special part to it.
Siwan:So yeah, and so where do you feel most connected to nature? It sounds like it might be on a surfboard, on a break, or is it a piece of country that you like to go back to?
Misko:Probably in our modern world. It's probably when we're camping somewhere where you can disconnect completely from technology. You don't have phone reception and it's relatively isolated. So I've took my family camping on the Upper Nambuida River in the national park there earlier this year in the beautiful gorge section with a camp right on a sort of floodplain pocket there and beautiful clear, fresh water to swim in and completely cut off from the rest of the world and you feel pretty connected to nature in those environments.
Siwan:Yeah, they're stunning 're stunning. We do the same. Actually, I was never a never a camper growing up, but uh, yeah, we've got a camper trailer now and it's just getting lost or not even lost. It's that sense of awe and uh, certainly not having your phone near you is absolutely wonderful, so you've made me want to pack my bags. You can take me back there. Mishko, take me to that place, it sounds wonderful.
Misko:Yeah, it was a very special spot.
Siwan:Well look, thank you so much for taking the time to talk to us about this fabulous project and, as I say, the Mary River was somewhere I was working on in the early 1990s, so it's lovely to hear that there's still work going on there and that it's being successful. So thanks again for spending time with us and listeners. We will put some show notes with Mishko's story so you can look at some photos, and it just leaves me to say thanks very much, mishko. I hope you have a great rest of your day. Thank you and thanks for the chat. You can subscribe to Take Me to the River. Wherever you get your podcasts, visit arrcau forward slash podcast to learn more. That's arrcau forward slash podcast. We acknowledge and respect Aboriginal and Torres Strait Islander peoples as the traditional and continuing custodians of the country and the rivers on which we live, learn, love and play. We respect and learn from Elders, past, present and emerging, valuing their knowledge, insights, cultures and connections to the waterways we all love and care for.