134 CIVIL WORKS GUIDELINES FOR MICRO-HYDROPOWER IN NEPAL
Figure 9.4 A gabion check dam at the intake of Jharkot micro-hydro scheme
by rolling boulders, 100 mm thick plain concrete was provided
at the top surface of the gabion wall. A minimum foundation
depth of 1 m from the lowest streambed level has been provided
for all check dams.
These check dams were constructed by the end of June 1998.
They have survived the first monsoon floods and currently
their conditions are being monitored.
9.7 Maintenance
Retaining walls, check dams and other slope stabilisation
structures should be inspected regularly; specifically before and
after every monsoon. Remedial works should be done as soon
as any problems are noticed. For example, the gabion crates, if
broken, should be repaired soon. Similarly, if stones are missing
from the dry stone masonry retaining walls or check dams,
they should be replaced. The drainage system of the stabilised
slope should be well maintained. Deposition of boulders, gravel
or soil in the drain should be removed. If the plaster or masonry
is broken, it should be repaired. Note that stability problems
can occur in even a well stabilised slope if the drainage system
stops functioning. It is important to note that some structures
such as gabion walls are not meant to be permanent on their
own. They may deteriorate and collapse. However, once
appropriate vegetation over these structures has taken root and
has matured repair of these structures may not be necessary,
since the roots of the vegetation will stabilise the soil mass. In
the case of bio-engineering measures, any plants that are
missing should be replaced. If possible, newly planted areas
should be fenced to prevent grazing of animals.