Monitoring and Maintenance of Stabilization Works
11.2.3.6 Environmental Aspects
The listing of this element last does not detract from its importance. It simply
acknowledges that the project must perform its bank stabilization function adequately, else
environmental function will likely be compromised as well. Also, some of the engineering
elements just discussed, particularly geomorphology and hydraulics, have environmental
implications as well.
The environmental parameters which should be monitored can be defined by reviewing
the environmental factors which were pertinent to the selection of the protection method.
Environmental specialists should be involved in the monitoring as appropriate.
11.2.4 FREQUENCY OF MONITORING
The first few years after construction and the first major flood flow are the two critical
periods in the life of bank protection works. Monitoring should be intensified during these
periods. Although events such as toe scour and scour at termination points and bank heads
may not fully develop during this period, major problem areas will usually become evident,
and will help define the required monitoring intensity for the long-term. As a minimum,
inspect the work immediately following the high flow season. If a need for immediate
reconstruction or repairs is discovered, then the process of design and construction can be
completed before the next high flow season.
During these critical periods, an additional inspection during low water levels in late
summer will allow an evaluation of the portion of the work that may have been underwater
during earlier inspections, as well as an evaluation of vegetative growth during the summer.
Problems with gradual deterioration of structural components does not carry the
urgency of major changes in channel geometry or alignment, or major flaws in the initial
design of the work. Therefore, any reasonable interval of monitoring will suffice for that
element.
Beyond these general guidelines, frequency of monitoring is determined either by
regulation) or by engineering judgement, whichever results in the most frequent monitoring.
Engineering judgement should take into account the safety factor of the original design and
the consequences of failure (see 6.6), the severity of hydraulic conditions, and the degree of
geomorphic instability of the stream. Monitoring of specific conditions such as channel
velocity, waves, or ice forces should be timed to coincide with the occurrence of critical
events if possible.
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