SMALL DAMS PETITS BARRAGES

downstream slope will show seepage to a height of approximately one-third the depth of the
high water level. Such saturation reduces the stability of the dam and creates maintenance
problems.
Although formerly very common in the design of small dams, the completely
homogenous section has been replaced by a modified homogeneous section in which small
amounts of carefully placed pervious materials control the action of seepage so as to permit
much steeper slopes. The effect of drainage at the downstream toe of the embankment is
shown on Fig. 5.1.
Fig. 5.1– Homogeneous dams with different types of drainage (Lewis, 2002).
If there are soils of satisfactory quality and sufficient quantity (1.5 times to twice the
volume required) available on site, the homogeneous earthfill or pseudo-zoned alternative
imposes itself as the most economical alternative. The pseudo-zoned dam is a variant of the
homogeneous type, which consists in distributing materials in the dam body according to their
grading or their humidity, without requiring filters to separate them, so there are no true zones.
For example, a homogenous dam may be built with the fine materials placed upstream and the
coarsest ones downstream, or with the wettest materials placed in the centre, as pointed out
by the French Guidelines on Small Dams.
5.3.2 Zoned Embankment Type
The most common type of a zoned dam section is that in which a central impervious
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