Applications of Close-range Imagery in River Research - Fluvial Remote Sensing for Science and Management - page 334

Table 15.2 Examples of possible ground-based imagery applications.

Types of photos Area covered References

Grain size Vertical ground photo Set of stations Graham et al. 2005 a&b

Grain morphometry Vertical ground photo Set of stations Roussillon et al. 2009

Grain petrography Vertical ground photo Experiment Riquier 2009

Sand coverage over a gravel
surface

Vertical ground photo Carbonneau et al. 2005

Bank retreat using
photogrammetry

Oblique ground photo At a station Lawler, 1993; Barker et al., 1997;

Pyle et al., 1997

Wood raft area or isolated
pieces detection

Oblique ground photo At a station Moulin and Piegay, 2004

Light under the canopy Fish eye/ground photo Set of stations Digan and Bren, 2003; Ringold

et al. 2003

Water level fluctuations;
morphological changes

Oblique ground
photo/timelaps video

At a station Chandler et al., 2002; Hicks

et al., 2002; Ashmore and
Saucks, 2006; Luchi et al.,
2007; Bertoldi et al., 2009;
Bird et al., 2010

Wood censing, bank states Oblique helicoptere

photos

Continuous reach Piegay and Landon, 1997

Riparian Landscape
characterisation

Set of stations Set of stations Cossin et Piegay, 2001

Landscape changes between
n dates

Oblique ground photo
(present and archived)

Sampling landscape scenes Start & Handasyde, 2002;

Michel et al. 2010

River ice growth Oblique ground Set of stations Dube, 2009

Subaerial processes on a
river bank

Oblique ground photo One river bank Hamel, 2011

River sediment structures Vertical from balloon

or mast

River channel width, riffle Church et al., 1998

experiments, is not easily found in field studies,
particularly on large rivers. The Tagliamento River
example discussed briefly above and more fully below,
provides another case study where oblique photography
from fixed locations has provided important reach-scale
insights about a large braided river. A set-up similar
to the one described by Chandler et al. (2002), with
the acquisition of four daily images, allowed Ashmore
and Saucks (2006) to assess the relationship between
discharge and channel width in a braided network. The
analysis showed that it is possible to use this method to
obtain discharge data in a multi-channel system, where
other direct measurements may be impossible.
Imagery can also be used to target smaller features and
focus on a narrower scene. Some authors have used cam-
eras 'at-a-station', focusing on specific river cross sections
or on a morphological unit of interest. Examples of this
include Dube's (2009) quantification of river-ice growth

rate on a riffle and pool sequence during the freezing
season in Quebec and Moulin and Piegay's (2004) exami-
nation of wood accumulations to evaluate wood trapping
at reservoirs (Figure 15.3). In this last case, the reser-
voirs trap and accumulate migrating dead wood, which
allowed the authors to determine the geographical origin
and the transported volumes of dead wood in relation
to river flow regime. In these examples, ground-based
techniques are essential to guarantee a high temporal
resolution, but even more importantly to accommodate
the unpredictable nature of the documented processes.
Oblique close-range photography also has the advan-
tage of providing information on sites or processes that
are not seen by vertical images such as those beneath a
vegetation canopy (e.g. bank profiles and channel beds
in rivers with vegetated banks). For example, Bird et al.
(2010) recently showed how close-range photogramme-
try can overcome the limits of aerial surveys. In narrow