Your Dam Your Responsibility (PDF~1.2MB)

4 Planning to Build a Dam
It is important to realise that building or owning a dam carries responsibilities for the owner,
regardless of any responsibilities which may apply to the designer or constructor (if these
are different people from the owner). When considering the construction of a new dam,
make sure you get the best advice on its design and construction to minimise the chance of
dam failure.
4.1 Dam Features
Farm dams are usually built using suitable materials found locally in the gully or hillside
where the dam is to be located. If local materials are not suitable, they may have to be
brought in from other areas or properly processed.
An embankment constructed across a valley or on a hillside is usually trapezoidal in
section. The sloping water face is called the upstream slope (face) and the downstream
side is called the downstream slope. More generally, the main features of a dam are
shown in Figure 4.1 below.
Figure 4.1 – Dam Features
Note: Spillway may be located at the left or right abutment, or both, as appropriate.
Freeboard is the difference in level between dam crest and spillway crest (overflow level).
The main features of a dam are the:
• embankment;
• spillway;
• outlet works; and
• environmental (or compensation) flow by-pass where required.
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International and national convention for ‘left’ and ‘right’ sides of a dam are determined
when looking downstream from the crest of the dam. This is the same as looking in the
direction water would naturally flow in the stream or gully
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