Monitoring and Maintenance of Stabilization Works
Those topics have been addressed in previous chapters, but their relevancy does not
diminish once a bank stabilization project has been completed.
The key word for monitoring is "comparability." For visual inspection, consider the
season of the year and precedent flows. Observations made in late winter following high
flows, with dormant vegetation, are not totally comparable to observations made in late
summer. The perspective of sequential photographs should be comparable. Cross-sections
and hydraulic data should be taken at comparable points and by comparable methods.
11.2.3 PRIMARY ELEMENTS
Available resources usually don't permit a monitoring program which obtains all
possible or even all desirable data. The following discussion will re-emphasize some
important concepts and identify those elements most critical to monitoring protection work.
The primary elements are:
Site inspection;
Site surveys;
Geomorphic observations;
Hydrologic and hydraulic data;
Geotechnical data; and
Environmental aspects.
Within the scope of these primary elements, Mellema (1987) provides sound advice
by stating that periodic fixed cross sections, gages to monitor river stages, and photographs
are the basic monitoring tools. More sophisticated measures are often worthwhile, but must
be weighed in the context of project requirements and long-term commitment of resources.
Pickett and Brown (1977) provide an extensive listing of potential data collection activities,
from which those appropriate for a specific project can be selected.
11.2.3.1 Site Inspection
On-site inspection of the work itself is certainly the primary and most cost-effective
monitoring element. Photographs made during these inspections are an invaluable supplement
to written notes because they document conditions more reliably than memory or written
observations, they can be referred to in the office while designing repairs if required, and they
provide useful evidence of maintenance needs if competition with other projects for
maintenance funds is a factor. Inspection should extend as far upstream and downstream of
the project reach as is necessary to ensure that events elsewhere are not threatening the
project.
If stream depths permit, wading and probing may reveal scour holes and displacement
of armor materials at the toe of a revetment.
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