Note: Where available, the PDF/Word icon below is provided to view the complete and fully formatted document
Disclaimer: The Parliamentary Library does not warrant or accept liability for the accuracy or usefulness of the transcripts. These are copied directly from the broadcaster's website.
Coastal Flood Impact -

View in ParlViewView other Segments

Ruben Meerman

In January 2011 this whole place was under water. The normally tranquil Brisbane River had
transformed into a surging torrent of destruction.

NARRATION

Lives were lost and tens of thousands were affected. The media captured incredible pictures of the
river. Now a vast brown plume of mud as it headed for Moreton Bay. Scientists looked on in horror.

Dr James Udy

You spend a lot of your time trying to protect these ecosystems and then one flood with all that
mud it just gets washed out.

NARRATION

It was here in the Moreton Bay Marine Park that sediment ended up.

Ruben Meerman

A little over a year later I'm here to find out how this beautiful bay is faring.

NARRATION

And we're going to be in for a few surprises. Moreton Bay Marine Park covers around three and a
half thousand square kilometres between the Gold and Sunshine Coasts. It's enclosed to the east by
islands and it's in the west, close to the city that the Brisbane River enters the bay.

Dr James Udy

Brisbane and South East Queensland is in the subtropics where we expect to get big floods. The
catchments deliver a lot of mud with the flood waters and it's that mud that causes the problem
when it smothers the marine ecosystems.

That's basically mud that will have come down from the 2011 flood.

Ruben Meerman

Oh goodness.

Dr James Udy

And you can see how this area may have been sandy previously, but now it's basically all mud and
you can feel when we're walking in it how you sink in now.

Ruben Meerman

I'm going way under.

Dr James Udy

Yeah.

NARRATION

In pre-European times it's estimated the Brisbane River carried twenty thousand tonnes of sediment
every year. A much lower figure compared to today.

Ruben Meerman

And so how much mud comes out of the river in a year?

Dr James Udy

A normal year maybe about half a million tonnes.

Ruben Meerman

Right.

Dr James Udy

Um, this last flood we estimate something over ten million tonnes of mud.

Ruben Meerman

Ten million tonnes, so that's nearly twenty years worth of mud?

Dr James Udy

Pretty much. Twenty years worth. The difference that's happened in the last century is the land
clearing and the way we use our landscape. The mud's made up of really fine sediment that may have
come from highly productive agricultural land, or it may have come from a construction site.

Ruben Meerman

Ah I'm um, I'm sinking right down here. Let me have a look at this stuff. It's really quite gross
isn't it?

Dr James Udy

Yeah it's really fine and the, gets resuspended in the water column really easily.

NARRATION

Professor Rod Connelly is leading a team of scientist who are monitoring the effects of the
sediment on the health of the bay.

Ruben Meerman

Tell us a bit about this place?

Prof Rod Connolly

So the way to think about Moreton Bay, Ruben is that away on the east it's relatively pristine, the
ecosystem is in good health. And then here on the west, we're at the mouth of the Brisbane River
and every year there's some sort of impact from the, the river water coming out of the catchment
and delivering things like sediment and silt.

Ruben Meerman

So what did you think was going to happen when you saw the floods?

Prof Rod Connolly

We expected that the main impact on the ecosystem would be near the mouth of the Brisbane River. We
expected that seagrasses in particular would be negatively affected, and they might be gone and not
be back for years.

NARRATION

Seagrass plays a critical role in the health of the ecosystem. It provides food for dugongs and
turtles and habitat for lots of other creatures.

Paul Maxell

Floods affect seagrasses um, in different ways. It can effectively smother the seagrass, so just
sit on top of it. Or it can stay in the water columns so it decreases the light environment, so it
makes poorer light conditions for seagrass to photosynthesise.

NARRATION

Seagrass meadows are found right across Moreton Bay.

Ruben Meerman

Beautiful.

NARRATION

Here in the east is one of Paul Maxwell's study sites.

Ruben Meerman

So how's this seagrass looking Paul?

Paul Maxell

Well it's very difficult to see by visual means, but we can tell by looking at the energy levels
that are inside these root systems down here. So we can compare them across the bay and we can
understand how the, the seagrasses internal pulses are going.

Ruben Meerman

Right so it's kind of, its little reserve in there.

Paul Maxell

That's correct.

Ruben Meerman

What is got stored up.

Paul Maxell

That's right.

NARRATION

And what Paul's finding is unexpected.

Paul Maxell

We've been seeing um, the seagrasses on the western side of the bay have been doing a lot better in
terms of their energy stores than the ones on the eastern side of the bay where it's clearer. So it
was a bit of a shock to us, we thought that the ones on the west where it's dirtier were going to
fall over a lot faster, but they didn't do that.

Ruben Meerman

Yeah that's really surprising. It's so beautiful over here, and yet this seagrass is not doing as
well as the grubby looking stuff over there.

Paul Maxell

Stuff on the west. That's right.

Ruben Meerman

That's really weird.

NARRATION

It's these depleted areas in the east that provide the most significant meadows in the bay. And
since dugongs eat only seagrass they're particularly vulnerable to any impact.

Dr James Udy

What we did find during 2011 after the flood is that the number of strandings or deaths was
definitely up on previous years. What we don't know is the longer term impact yet and I think it
really is a bit early to say.

NARRATION

The rich ecosystem of Moreton Bay also includes over sixty species of coral. Research scientist
Andrew Olds is assessing how they're fairing.

Andrew Olds

When coral is impacted from a, a event like the flooding that we saw last year, the corals become
stressed, it could be to do with nutrients, sediments or fresh water or all of the above.

NARRATION

This stress can sometimes lead to coral bleaching. Like here in the east.

Ruben Meerman

It's amazing there's, I've never seen a bleached coral like that before but there's not many of
them.

Andrew Olds

No there's not. No the, a, a small amount of the coral in the bay, bay bleached and it was
relatively consistent across the bay, but this site had some of the most bleached coral in Moreton
Bay.

Ruben Meerman

Yeah right. Well let's look at some more.

Andrew Olds

Sounds good. The floods cause two to ten percent of the coral across Moreton Bay to bleach, and
only a really small proportion of this, this bleached coral to actually die.

NARRATION

Just as they found with seagrass the results are showing that despite taking more of a hammering
than the east, the west has coped better.

Ruben Meerman

What do you thinks the reason for that?

Paul Maxell

I think one way to look at it is if you think about would you expect an individual, a human that is
in very good health to be better able to ward off disease, and you probably think well yes you
would. But in fact with the ecosystem it's the, part of ecosystem here on the western side that's
been having little bits of suffering year in year out was better able to cope this time when the
major flood came.

Dr James Udy

Longer term we have to be very mindful of what we're doing on the land that comes swishing out into
Moreton Bay and will affect the ecosystem for now and in the future.

Ruben Meerman

This time Moreton Bay faired surprisingly well, but with climate change we expect bigger floods
more often.

NARRATION

And while this ecosystem has proved more resilient than expected, nobody knows how much more it can
take. The one thing that's certain it's too beautiful to risk finding out.

Topics: Environment

Reporter: Ruben Meerman

Producer: Geraldine McKenna

Researcher: Sarah Shands

Camera: Brett Ramsay

Sound: Basil Krivoroutchko

Editor: Toby Trappel

Story Contacts

Dr James Udy

Chief Scientist

Healthy Waterways

Prof Rod Connolly

Australian Rivers Institute

School of Environment,

Griffith University, QLD

Paul Maxwell

School of Environment,

Griffith University, QLD

Andrew Olds

School of Environment,

Griffith University, QLD