- We have had a catastrophic rain event. It's definitely a hundred year flood, and we're 30 kilometers from
Lismore, by river anyway, 20 kilometers by road. And they had a 14 meter rise on the river, two meters, a whopping two
meters over the previous record. There's 900 to a thousand houses that are going to have to be demolished 'cause they're so wrecked
by the flood water. It went right over the roofs. People's lives are ruined by this event. There's a massive, massive flood
recovery going on right now with thousands of people. It looks like a war zone. There's helicopters
going over all the time. The Army are involved. It's really, really a huge rain event. We recorded 775 millimeters in 24 hours. One hour alone was 180 millimeters. That is absolutely huge. So, we've got a car coming down the road, he's going to come past us. And everybody's trying to recover somehow. So we're in the head water creeks, where they converge down towards
the floodplain in Lismore. All of these creeks were coming in with that massive volume of water, and they bottle necked there at Lismore, and that flooding event
went up that huge volume. How did Zaytuna Farm handle that event? Well, let's go and have a look. This spillway's still going over. And this is one of our
main catchment dams. This is Tinkers Bubble. It's one of our main
irrigation dams actually. And there are two main
catchments on Zaytuna Farm, this one and Koonorigan Road, and we concentrate them
toward the central valley. So here, although we have a really good swale spillway connection to the next dam, the spillway just couldn't
take the enormous amount of water coming off the hill country, and it came up over the dam wall. You can see the flood patterns here, the flow patterns of the
water rushing through here. So normally that will
actually breach a dam wall and cut it away, but we
have this really good clumping bamboo plantation here. And what's happened is a
little bit of top soil's gone and you get this skin of like
a carpet of bamboo roots. And it's held it together perfectly. So without the emergency
spillway in position, with the top end of the wall and the water going over the top, the bamboo just was the perfect solution, and it was here and well established. But that went on down to the next dam, and it hit the next dam with a big thump. Now let's go and have a look
at what happened right here. Now this is actually a farm track, but it's not been mowed
for obvious reasons. We're having a job to get
in here at the moment, with this much water. But our main irrigation
dam, Tinkers Bubble is just above us where I've just left. Coming down here, I come to a set of dams. Fish pond here we call Tambuktee overflows and goes under this
track with a crossing pipe into a dam called Mud Hole, appropriately. And that's the big overload. It got hit by the overload
of Tinkers Bubble. It was already getting fed by Tambuktee, the dribbler pipe here in Mud Hole wall couldn't take it and it cut right out and took all that material
down to the next dam, where it stopped, luckily,
in the Fern Gully dam below, a dam called Fern Gully. Now, there's no emergency
spillway in this section, and it's one of the only two dams that doesn't have an
emergency spillway here. It was really built with
a co-joined spillway to handle a 20 year event. It couldn't handle the hundred year event. We can design that to change, but right now we've got
a little bit of luck. It didn't cut the dam wall out, it cut the spillway out, and it's the spillway
material between the two dams. Luckily, we can rebuild this, and then we can demonstrate how you handle one of these hundred of year events. So here's the cut, I've straddled the cut. It's wider at the top
where it first went over with volume and pressure. And then as the pressure went down, it's just a narrow little cut here. And that's the lost material
with the erosion down there. The crossing pipe's still running, the spillway above us is still running, the dribbler pipe's
well left high and dry. So this is the most damage we've
ever, ever had to withstand at Zaytuna Farm. Here we are, well this is Fern Gully dam, or let's say it was. I'd be stood on about three
meters of water here normally, but I'm stood on three
meters of stone and dirt that's come down from
the spillway up there, and it stopped here. So at least it stopped here. Interestingly, the flow is
still going down the swale and over the level sill. And it didn't quite go over the wall, and it actually forced its
own level sill spillway like an emergency spillway
emerged right here. So the emergency spillway,
which we didn't install, but it pushed itself over here and went down through a
beautiful set of rocks there that stopped any erosion. So there was quite a
clear run of water here. It kind of self indicated
what needs to be installed, an emergency spillway right there. The other end, it's still performing. The swale was still holding water. So let's see if we can walk on through over the rocky sections here. So if I suddenly disappear, send out for the rescue squad. (laughing) So we're going over the rockier bits. And we're almost walking on water here. Hopefully we don't suddenly sink. Our flow of water's still coming through instead of through a dam to a swale, it's almost like a little stream going to the level sill spillway. So I think we've got to jump
over this section in here. So here's our swale,
well our silted swale, connected to what was our dam, Fern Gully. But the swale flow is
still working perfectly. It's overflowing here, that big dribbler pipe's
taking some pressure, and it's hit the level swale here. So this level swale has
completely pacified the water, spread it out, and then
continued to spread it, come through the fence here. And it spread out and out and
out and pacified more and more as it's gone downhill. That's the story all the way
through our water harvesting earthworks. So here in our bottom floodplain paddock, we've had a massive deposit of topsoil. It's not our topsoil, it's
come from up in the catchment. But in some places it's between
one and two meters deep. That's hundreds of years of soil. It would take you quite
a few hundred years to build that much soil on a property, and it's all deposited in one day. It's always quite dangerous
to walk through here. It's very soft at the moment. But this will be a massive deposit for us, a benefit to us. Many farms have only had a
few in inches of topsoil. We've had a lot because we
have a lot of treed gullies. We planted a lot of trees
along our contour water harvesting systems, that
slows down the flood water and allows it to drop the
material it's carrying. As soon as you drop the
velocity in a moving fluid, it drops the volume of
material it's carrying. So this is a massive deposition, and it's really where the
problem becomes a solution for actual soil fertility 'cause
we've gained so much soil. With it has come enormous logs. So if we turn around here, you can see the volume of material that floats in the flood
all the way through here. Big rainforest logs arrived here. And if we look up, you can see the flood
deposit up in the tree. So that doesn't lie. That's how high the flood was above us. That's the volume of water that
was heading towards Lismore from these top catchments. Here's one of our huge clumping bamboos. It's literally been uprooted
some 500 meters upstream and now deposited here on
one of our farm tracks. I don't think we're going to move it easy. But we cut the top off here
and cut out the root system. It's quite a valuable nursery crop. But it just shows you the
absolute power of the water coming downstream. So this is Campers Lagoon. We're on the other side
of Zaytuna Farm now, and this catchment is about
the biggest and the strongest. But this dam has a level
sill on a swale just here with a swale pipe further down
and an emergency spillway, also a level sill on a swale on this side and multiple swivel pipes
further down the swale. So as soon as this spillway, the normal spillway gets
up to a certain height, the emergency kicks in
and takes all the flow. It performed perfectly because we had enough
overflow infrastructure. Now without this dam being here, there would be a massive erosion gully coming straight through the
middle of the valley here. But instead there's a
nice passive body of water and everything flowed very nicely. So what's to come next? The world is continuously changing. These radical events are
going to become more extreme and more frequent. Every end of 20 years, we can't repair as quick as the event increases. A few years ago, not that long ago, this whole landscape was burning just a few kilometers from here. We have to maintain
drought proofing earthworks to buffer those extreme events, and we have to handle these extreme events when we get these massive flows of water that are so destructive. That we can do. We can do it with design, and design is what we are all about. (bright music)
