TRaCK—Tropical Rivers and Coastal
Knowledge—has around 1.2 million square kilometres of land
within its research area in tropical northern Australia, much of it
remote and inaccessible. A new GIS tool promises a dynamic and
flexible way for researchers and land managers to examine
river data. By Mary O’Callaghan
Figure 1. The GIS-based geomorphic
classification tool highlights that there are major differences
between rivers in the Southern Gulf country and in the Kimberley.
In this example, streams that are similar to the selected section
of river are shown in red. Streams that are dissimilar are shown in
green.
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With such a large research area, it is easy to see why
scientists can’t visit each river reach. For this reason,
TRaCK research focuses on four catchments: the Daly in the Northern
Territory, the Fitzroy in Western Australia, and the Mitchell and
Flinders in Queensland. But how do we know whether we can
confidently apply the findings from field work in one catchment to
other catchments across the north?
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The Mitchell and the Daly, two very different rivers:
The Mitchell (pictured above) has a 1.5
kilometre-wide channel in its lower reaches which flows through an
alluvial floodplain. When it is choked with sand it can shift
sideways by 50–100 metres in some years.
Large pools (up to several kilometres in length)
form one year and disappear the next. By contrast, the lower Daly
(pictured below) has a relatively narrow (about 100 metres wide)
and stable channel, largely bounded by bedrock. Pools in this river
tend to ‘stay put’.
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“There are some fundamental differences between, for
example, the Mitchell and the Daly Rivers,” says Dr Andrew
Brooks from Griffith University (see pictures right).
“So, it’s important to get the message across that,
just because we’ve done a lot of detailed work on the Daly,
for example, this doesn’t necessarily mean that it’s
applicable across Australia.”
Dr Brooks and his team set out to develop a method for
describing the similarity, or dissimilarity, of the region’s
riverine landscapes, as part of a method for legitimately
extrapolating information from one segment of river to another.
What they’ve come up with is a way of classifying rivers
that Dr Brooks believes could make other classification systems
redundant.
Overcoming scale and subjectivity
In the field of geomorphology—understanding landscapes
—there is a long history of classification systems.
“Just about every government program doing research over
large scales uses some sort of classification,” explains Dr
Brooks. “The problem is that any classification system has a
lot of subjectivity; and they are often designed for specific
purposes.”
Understanding that different people use classifications for
different reasons, Dr Brooks and colleague John Spencer thought
they could develop a better, more flexible approach using large
spatial data sets.
Driven by the users’ needs
What John Spencer has developed is an interactive GIS-based tool
where you select a specific segment of river, choose one or more
variables—such as stream slope, valley width, catchment area,
drainage density, geology—and you are presented with a
measure of similarity between your river segment and all
others.
For categorical data, such as geology, where there are no
degrees of similarity, river segments that are the same show up in
red on the map; those that are different show up in green. For data
that is continuously variable, such as elevation, river segments
that are similar are shown in varying shades of colour that reflect
the degree of similarity.
From there you can define how many classes you want and, at the
click of a button, the system will generate your user-defined
classification.
And, unlike most GIS-based classifications, you can save the
specification for how you made it, in case you ever want to run it
again or compare it to another version. You can also download the
underlying layers of data that the classification comprises.
Not just another classification
According to Dr Brooks, this is not just another
classification.
“It’s dynamic and flexible, and allows people to
explore the data. It really is a quantum leap from other
classifications,” he said.
“To my knowledge this is the first time anyone’s
developed such a system anywhere in the world. And you can build on
it—that’s the beauty of it. It’s not set in time,
which is the major constraint with a lot of other classifications.
We can update it as new data becomes available.”
The system is already providing insights.
“It is obvious that there are major differences between
the Southern Gulf country and the Kimberley—really
fundamental differences that people need to understand,” says
Dr Brooks (Figure 1). ‘If you’ve got a study on
the Flinders River floodplain, it’s probably not going to be
a lot of use to someone in the Kimberley.”
Dr Mark Kennard, a fish ecologist and senior research fellow at
Griffith University, says the system’s advantage is its
flexibility. “There is no single correct classification as it
really depends on the particular environmental features the user is
interested in,” he said, “so being able to do things on
the fly and then quickly try again with a different combination of
variables is great.
“I think it’s a really useful tool for the public,
for scientists and for people doing field surveys where they need
to stratify sites, comparing like with like.”
Because it’s so flexible, Dr Brooks is keen for different
groups with different objectives to try it out.
“The plan is to make the system available on the web so
that people can run it from anywhere,” explained Dr
Brooks.
“We need to know it is meaningful on the ground, that we
are not just generating pretty maps. It has to be able to usefully
distinguish one type of river from another.”
Contact
Dr Andrew Brooks, Griffith University
Email: andrew.brooks@griffith.edu.au
John Spencer, Griffith University
Email: j.spencer@griffith.edu.au
Reprinted with permission from ON TRaCK newsletter, Issue 2
www.track.gov.au
TRaCK
TRaCK brings together leading tropical river researchers and
managers from Charles Darwin University, Griffith University,
University of Western Australia, CSIRO, James Cook University,
Australian National University, Geoscience Australia, Environmental
Research Institute of the Supervising Scientist, Australian
Institute of Marine Science, North Australia Indigenous Land and
Sea Management Alliance, and the Governments of Qld, NT and WA.
