Catchments are the fundamental unit for most resource planning and
management purposes, but how are they defined? Until now it has been either a tedious and
expensive manual exercise, or something of a "best guesstimate". We solve the
problem, and remove the hard work and uncertainty from this important process. The
following page begins with a few basic explanations. You can skip the intro and proceed to
detailed examples by clicking here, or to a new case study of water supply and environmental flow analysis.
To be effective and widely
applicable, we use widely available data types:
Elevation or "height" data, and.. |
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drainage or watercourse
information |
We then subject the raw data to powerful
calculations.
While this image doesn't resemble a "catchment map" as
we would generally think of it, our technology allows us to convert the results to
real-world catchment boundaries.. |
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The blue dots highlight individual
catchments for each watercourse in the "district", including first order
tributaries (that is, the smallest creeks). This is useful for
cooperative catchment management between neighbouring land managers for example. |
Regional catchments can be generated
progressively, depending on the purpose.
Erosion control and flood risk are two catchment management areas
where this approach is of enormous value. |
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This shows a "bird's eye" view of our district, and
highlights one of its catchments which we will now use to show how additional information
can be extracted.. |
The sub catchments can be categorised according
to where they occur. "First order" creeks flow into
"second order" creeks and so on. All eventually
flow into a major river, and then (usually!), the ocean.. |
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This view
shows the relationship between sub-catchments and the
landscape. Notice that some second order creeks flow into fourth order rivers or higher.
This is important for many land management purposes, especially in hilly country, and can
only be usefully determined by comprehensive catchment analysis. Click
on the image to see a more detailed (200K) version.. |
Once defined, our state-of-the art technology
allows users to extract important information about the land they manage..
For example how prone each sub-catchment will be to flooding
following a particular rainfall event. |
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Or to build up a picture of regional flood risk
for infrastructure planning, land valuation, insurance assessment.. |
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Very useful for local authorities, emergency services, primary
producers, engineers and construction professionals.. This map shows an
assessment of the extent of flooding which could be expected in the event of a breach in
the dam wall of a major reservoir in Tasmania. |
| Of course the real world is dynamic and complex. It requires a
good understanding of how its components interact. For flood prediction for example,
rainfall is only one ingredient! Here we have used land cover (whether
forested, cropped, or urban) to further refine the tendency for each catchment to flood. Dark green is relatively high. |
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Even so, only the tendency of each individual catchment to
flooding is revealed - dark blue are individually
high risk sub-catchments. The power of spatial technology
allows us to calculate the cascading impact of run-off flowing down each catchment into
the next.. |
| The final result predicts behaviour for the entire
catchment, having taken into account all the known variation, plus the dynamic behaviour
of the landscape. Also see our new data products
page for more detailed information!
Notice
how the "first order" creeks contribute differently to different parts of the
catchment.Click here to remind yourself how the different catchments are arranged.
Similar approaches can be used for predicting (and
therefore controlling) soil erosion, weed spread, and many other pressing land and
environmental management issues. |
 
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In addition, our
ready-made catchment data can be applied to water management issues generally, including
the derivation of environmental flows and seasonal availability of water for urban and
other essential supplies. This example shows how
rainfall data and MapMakers soils data have been used to model the water yield for each
catchment supplying the City of Hobart. |
Soil
permeability characteristics and profile depths are combined with..
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..annual rainfall data
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..to allow an analysis of
potential water supply, and thus storage and environmental flow requirements, for
different planning horizons. |
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At MapMakers we specialise in delivering
considered, professional solutions to land and resource management professionals.
Contact us soon to take advantage of our application and
technical expertise. |
Nested catchment boundaries ©
MapMakers P/L. Relief for this catchment demo based on: Nix, H. A., Stein, J.A. and Stein,
J.L., 1992, Developing an environmental geographic information system for Tasmania. Report
to the Land Resources Division of Rural Resources, Department of Primary Industries and
Energy. Drainage information extrapolated and enhanced from Topographic base
data © Australian Surveying and Land information Group www.auslig.gov.au.
Topographic backdrop © Australian Surveying and Land information Group www.auslig.gov.au. |
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