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A visual inspection of a dam, and
its surrounding area, are an important part of a reservoir
safety check. Unusual features on the face of a dam may reveal
important clues about the condition of its internal body.
At embankment dams,
the civil
engineer looks for cracks, bulges and hollows on the
downstream
face and on the upstream
face, when the water is low. These features could indicate
that the dam is becoming unstable, and that there is a possibility
that, with time, a portion of the slope could collapse, just
like a landslide. Hollows can also indicate that floodwater
has been overtopping
the dam and gradually eroding
the downstream slope. Engineers also look for signs of water
leakage
through or underneath the dam. Water leaking through the dam
can erode away the material inside gradually creating a large
cavity. Eventually, the cavity can collapse in on itself reducing
the stability of the dam. Water leaking under the dam can
indicate that there is a problem in its foundation.
  Concrete
dams have tunnels running through them called inspection galleries.
These are just big enough for a person to walk through, so
the engineer can inspect the condition of the dam inside as
well as outside. The surface of the concrete is checked for
deterioration and cracking. The engineer also looks for any
signs that could show that the dam or sections of it are moving.
Checks are also made for any leaks.
On all types of dams the
condition of water pipes, valves
and floodgates
are checked. The valves and gates are operated regularly to
check that they will work when required.
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