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Remote sensing: applicability,
practical implementation, experience from the trials, indicative
costs
Pages in this section include:
This page provides a detailed description of the applicability,
practical implementation, experience from the trials, and indicative
costs for the remote sensing channel seepage identification
and measurement technique.
Applicability
- Remote sensing allows rapid identification of seepage zones
of large lengths of a channel system without interfering with
channel
operations. Quantification needs to be based on further analysis.
Remote sensing is appropriate for investigations where the
primary aim is identification of land degradation associated
with channel
seepage. It relies on detection of differences in soil and
moisture properties in the upper surface and has significant
potential
if there are known surface effects of channel seepage.
- Remote
sensing is most useful in environments where lateral seepage
is predominant. Sites with a high watertable, shallow
impermeable
layer or bank seepage are environments most likely to facilitate
lateral seepage and cause seepage to have a surface expression.
- Remote
sensing offers a means of providing a first-cut identification
tool for targeting potential seepage sites.
The main drawback is
that seepage must have a surface expression as moist soil
or associated vegetation adjacent to the channel. Therefore
remote sensing cannot
be used if the seepage mechanism is predominantly vertical,
which is likely to occur at sites with a deep watertable.
- Remote
sensing needs to be conducted at a suitably large scale to
be cost effective. Costs are likely to come down
and resolution
likely to improve as the technology develops, and it
will therefore become an increasingly attractive option.
| Practical implementation |
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Remote sensing is relatively expensive and requires
specialist technical input at the planning, data
gathering, processing and interpretation stages.
However, it can rapidly acquire data over long distances
of channel, and along with geophysical surveys it
is likely to be a key part of future large-scale
channel seepage investigations.
Care needs to be taken in the interpretation. For
example, sites with moist soils not caused by seepage
can be misinterpreted as seepage sites (e.g. drainage
lines, topographic lows). Interpretation of data
benefits from integration with other investigation
techniques.
| Indicative Costs |
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Remote sensing costs for specific channel seepage investigations
were not obtained from the IAL trials. A significant proportion
of the costs relate to data processing by specialist contractors.
The following indicative costs are for data collection only.
Spatial resolution of less than 10|m would be required.
- Landsat imagery (25m cells) 25 x 25km = $550
- Spot imagery
(10m cells, black and white only) - 25 x 25km = $325
- There
may be local opportunities for data collection: In Victoria,
there is a Daedalus multispectral
scanner which has 11 bands.
This is flown by DNRE in near infra-red mode during fire
season and
in multispectral (11 bands) mode otherwise. As a guide,
the cost for this in a 25 x 25km area may be about
$2,500 at 10m resolution
and about $3,000 for 5m resolution. The data collection
costs of suitable quality airborne infra-red data (3-5m
resolution)
for three lengths of channel in the Wimmera (approximately
10-20km each) were quoted approximately
at $11,000.
Data processing costs including integration with the stakeholder’s
GIS system are in addition to the above costs.
| Related
pages |
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Remote sensing: summary
Remote
sensing: principle, method |
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