Management Applications of Optical Remote Sensing in the Active River Channel - Fluvial Remote Sensing for Science and Management - page 36

Second, sometimes ground based measurements are
more precise, but the broad areal coverage provided by
the imagery makes remotely sensed maps more globally
accurate. Marcus and Fonstad (2008) make this case with
the example of field surveys of cross sections, which are
precise and very accurate at that one location. Yet those
cross sections are poor predictors of depth a short distance
away from the survey location. The

for decades to acquire information they do not share
with other parties. However, because rivers are often a
publicly owned and managed resource and are connected
to up- and down-stream users, the issue of privileging a
set of technologically savvy users over other residents of
the basin is particularly problematic with rivers. If a small
number of users have information on the best fish habitat,
gravel supplies, reaches with high quality water, or other
factors, they can potentially exploit the river resource to
their own benefit, but not necessarily to the benefit of
others living within the same watershed. Whether this is
viewed as good or bad depends on the perspective of the
individuals and society.
One solution to the concern regarding private exploita-
tion is to make all remote sensing results publicly available,
an approach advocated by the United Nations (United
Nations General Assembly, 1986). Yet allowing this degree
of access raises concerns regarding intellectual property
and environmental protection. Particularly with high spa-
tial resolution imagery, the maps may reveal the locations
of sensitive resources (e.g., habitat for an endangered
species), potentially jeopardising the very resource one
is trying to protect (Marcus and Fonstad, 2008). Man-
agers may therefore want to consider aggregating the data
to a coarser spatial resolution, as is done with the U.S.
Census, where results are reported at the block level but
not the household level. Alternatively, one could make
the locations blurry or indistinct, obscuring the map
coordinates to prevent resource exploitation. But these
approaches invite the same criticism leveled before, where
a privileged elite have access to information that others
cannot share. Competing social goals thus leave managers
having to grapple with such issues on a case-by-case basis.
As with any technology, the potential for use and
misuse of river remote sensing is broad. The importance
of water to human society and the connectivity of rivers
make the potential benefits and costs all the greater in
rivers. It will largely be up to river managers, who have the
broadest access to information about rivers and their user
populations, to contemplate and develop uses for remote
sensing that most benefit rivers and the communities that
depend upon them.

15 cm precision of
the remote sensing depths at all locations in the stream
thus provides better global bathymetric accuracy than the
high local accuracy of the cross section survey. Similar
arguments can be made for SAV, turbidity, and algae, all
of which require relatively time consuming local surveys
that are representative of values at or near the sample site.
Third and finally, remote sensing maps are clearly
the most accurate alternative when they are the only
alternative. This occurs when historic data are needed
or where sites are inaccessible or too dangerous for
field surveys. Reconstruction of historic channel change,
mapping of algae in roadless areas, and mapping of floods
and ice breakup all represent cases discussed above where
remote sensing might provide the only viable mapping
alternative.
None of the points above are intended to imply that
remote sensing is always the most accurate or the preferred
alternative. Rather, our point is that accuracy measures
must be considered in the context of the management
needs for local precision, global accuracy, and the range
of alternatives available for gathering data.

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2.14 Ethical considerations

Remote sensing of rivers can raise ethical issues not
typically encountered with classical ground-based data.
Some of these issues are addressed in guidelines regard-
ing professional conduct (ASPRS, 2007), data sharing as
it relates to national security (Federal Geographic Data
Committee, 2005), and the use of remote sensing to bene-
fit people of all backgrounds and economic levels (United
Nations General Assembly, 1986). Many countries also
have a history of legal precedent regarding privacy and the
use of remote imagery. We do not attempt to provide an
in-depth discussion of these issues, but rather, raise some
concerns that are particularly relevant to river managers.
The use of remote sensing raises social equity issues,
potentially providing users who have access to remote
sensing technology an advantage in accessing the river
resource. This situation is nothing new; timber and min-
eral companies, for example, have used remote sensing

2.15 Why use optical remote sensing?

The reasons for using remote sensing for river manage-
ment are similar to those reasons for considering remote
sensing in any setting. Among the most important con-
siderations are which features can be remotely mapped