Environmental Assessment
Volume C-3.1
Slurry Pipeline
Topography and Geomorphology
Ambatovy Project
20
January 2006
Table 3.1-1 Impact Description Criteria for Topography and Geomorphology
Direction
Magnitude
Geographic
Extent
Duration
Reversibility
Frequency
neutral:
no change
in topography
negative:
a change
in topography that
affects function for
human or biological
services
negligible:
no
measurable effect on
slopes and landscape-
level topographic
features
low:
slight changes in
slopes or overall
topographic layout
moderate:
locally
prominent changes in
slopes or overall
topographic layout
high:
regionally
prominent changes in
slopes or overall
topographic layout
local:
effect
restricted to the
LSA
regional:
effect
extends beyond
the LSA
short term:
<3 years
medium
term:
3 to
30 years
long term:
>30 years
reversible or
irreversible
low:
occurs
once
medium:
occurs
intermittently
high:
occurs
continuously
3.1.5.3 Mitigation
During construction, operations and closure, erosion control measures will be
applied as described in Volume C, Section 6 to minimize the formation of gulleys
and the removal of surface material due to water and wind erosion.
During construction, operations and the beginning of the closure phase, water
management systems will be used to catch flows along the base of disturbed
features and mitigate siltation in downstream basins. This will be particularly
important to mitigate effects on valleys downstream that are productive for rice
production and other land uses.
During the operations and closure phases, reclamation will occur. Revegetation
will reduce erosion of surface material and will help to maintain slopes and other
topographic features. Slopes will be contoured to maintain long-term stability.
Closure landforms will be designed such that there will be continuity of
landforms and watershed systems between undisturbed land and reclaimed areas.
3.1.5.4 Results
All along the pipeline route, small-scale topographic modifications will be
necessary to accommodate a flat pipeline RoW (right-of-way) with a width of
between 25 and 100 m. Areas with steeper side slopes require greater
topographic modification to create adequate, flat pipeline RoWs. Slope cutting is
expected to create a variety of locally noticeable landscape modifications along
the length of the pipeline, given the prevalence of locally steep slopes for most of
