Geotechnical News • December 2016
35
WASTE GEOTECHNICS
allows for the identification of critical
landscape features that may affect the
location of tailings impoundments,
landfills, roadways, pipelines, etc. For
example, not only can soil material
types (e.g., till, residual bedrock,
fluvial, organic, etc.), drainage regime
(e.g., well, moderate, poor, very poor,
etc.) and slope gradients be deter-
mined from interpreting the aerial
photographs in 3D, but small features
such as coarse-textured crevasse fill-
ings or wetlands can be identified and
mapped properly.
Figures 5 – 8 and 9 - 11 provide a
number of screen shots at various
scales to show the advantage of soft-
copy mapping tools; unfortunately, 3D
images cannot be presented within this
paper due to formatting, so examples
are provided
showing a small
water impound-
ment in the Great
Plains of the
United States and
a tailings pond in
northern Canada.
Both these fea-
tures, especially
the water impoundment are relatively
obscure features on the landscape at
1:30,000 and are often overlooked or
not mapped when using 1:20,000 or
1:30,000 scale aerial photographs.
Using B&W aerial photographs
initially captured at 1:30,000 scale
(Figure 5), the mapper is able to
zoom down from the original capture
scale of 1:30,000 to scales as large as
1:2,000 (Figure 6) and 1:1,000 (Figure
7) to better delineate the impoundment
features, including the water and the
earthen dam. The dam in this series of
figures is 100 m in length; the reser-
voir is 0.65 ha (1.6 ac.) in size and 162
m in length. The surrounding area is
comprised of strongly eroded morainal
veneers and residual bedrock materials
overlying bedrock.
Figure 7. 1:30,000 scale image zoomed into at 1:1,000
scale.
Figure 8. Detailed 1:2,000 scale terrain mapping; blue -
water; red - anthropogenic impoundment dams); brown
- colluvium; bright yellow – fluvial; coral – residual; and
olive, eolian.
Figure 9. 1:30,000 scale image, initial capture scale of
the aerial photo.
Figure 10. 1:30,000 scale image zoomed into at 1:2,000
scale.
