Monitoring and Maintenance of Stabilization Works
accommodate toe scour (see 6.3) will determine if maintenance or reinforcement of the toe
is required.
Other examples where maintenance may not be required are:
Loss of stone at the riverward end and along the downstream side of stone
dikes. This is to be expected as scour holes develop to an equilibrium
condition, and should have been allowed for in the original design (see 8.1).
Settlement of flexible mattresses at the toe of the bank slope. Again, this is
a common occurrence and is not cause for alarm unless the original design
(see 7.4) did not adequately provide for it.
"Chipping" or "shelving" at the top of the bank slope where armor protection
terminates below top bank, or within indirect protection structures. This
condition may stabilize naturally as the slope flattens and as vegetation
becomes established (see 6.2.5).
Minor, long-term deterioration of structural components, if stone or other
permanent toe protection is present, and if vegetation is becoming well
established on the slope or within the dike or retard field.
Maintenance requirements for vegetative components of stabilization is highly regional
and site-specific. Substantial effort may be involved for some projects. The transition from
the construction phase into the maintenance phase is often ill-defined, and may in fact depend
more upon administrative distinctions for funding purposes than upon engineering and
biological judgements. The situation is further complicated by vegetation being a basic
component of the work in some cases, but perversely posing a threat to the work's integrity
in other cases. The key is a judgmental determination of whether the vegetation adversely
affects the "functionality" of the work.
11.3.2 DETERMINATION OF METHOD OF REPAIR
As with the determination of the need for maintenance, there are seemingly
contradictory alternative approaches to selecting a method of maintenance if part of the work
fails:
Restore the work using the original approach;
Increase the safety factor of the work by using the same type of protection
with more severe design criteria; and
Select a different method of stabilization for the repairs.
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