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| 1 Identify and quantify the seepage problem |
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IAL has investigated and documented techniques for identifying,
quantifying and monitoring channel seepage. A six-step process
for planning, implementation and evaluation of a channel seepage
and measurement investigation is proposed (Recommended approach
and techniques). Procedures are recommended for measurement of
seepage on both local and intermediate to large scale.
See Identification and measurement for information about determining
the rate of seepage for a particular site, following initial identification
by inspection, information from landowners, or apparent water losses.
Quantification of a seepage problem by the way of a seepage rate
(L/m2/day) is required to determine the extent of the seepage problem
and potential benefits of remediation works.
Seepage mechanisms
Seepage assessment should include an appraisal of the dominant
seepage mechanism occurring at the site. Seepage mechanisms from
earthen channels can be predominantly horizontal or vertical, or
a combination of the two. The dominant mechanism at a site will
affect the rate of seepage, the impact and the most appropriate
remediation approach. For predominantly horizontal seepage, remediation
using cut-off walls, core trenches or bank lining may be all that
is needed. This can be considerably cheaper than lining the entire
wetted perimeter of the channel. Vertical seepage or a combination
of horizontal and vertical seepage may require works in the channel
bed only, or may require full treatment of the wetted perimeter.
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Previous: Remediation decision-making process
Next: 2 Determine remediation objectives |
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