SMALL DAMS PETITS BARRAGES

Fig.5.17 – Standard cross section view of inclined impervious zone
Table 5.25 – Reference dimensions for reservoirs with an inclined impervious zone.[8]
Height of dam H (m) - 5 5 - 10 10 - 15 Summary
Height from foundation surface
to water level H1 (m)
-3,3 3,3-7,8 7,8-12,2
Assumed from dam
height
Major differences exist
Planned overflow depth h1 (m) 0,3-0,5 0,5-0,8 0,8-1,2
in accordance with
position and design of
spillways.
In accordance with
Freeboard h2 (m) 1,0-1,2 1,2-1,4 1,4-1,6 formulas (3.3.5) and
(3.3.6)
Dam crest width B (m) 2,0-3,0 3,0-4,0 4,0-5,0
In accordance with
formula (3.3.7)
Gradient n1 (%) 1,5-1,8 1,8-2,1 2,1-3,0 1.5-3.0
Front Slope
Step width b (m) 0-1,5 1,5 0,2
Minimum of 1 m if dam
is to be stepped
Distance from dam
crest h3 (m)
0,3-0,5 ≥ 0,5 ≥ 0,5 ≥ 0.3 m
Dam crest width d1
(m)
1,5-1,8 1,8-2,4 2,4-3,5 1.5–3.5 m
Distance from front
d4 (m)
1,5 1,5 ≥ 1,5 ≥ 1.5 m
Impervious Zone
Where n2=n1-0.1
n3=n2-0.2
Upper excavation
width d2 (m)
Lower excavation
width d3 (m)
Depth of
excavation h4 (m)
1,1-1,3 1,3-2,1 2,1-3,2
d3=1/2 d2
Depends on soil quality
of foundation surface.
Figures here included only
for reference.
Rear gradient n4 (10%) 1,5-1,8 1,8-2,1 2,1-2,5 1.5-2.5
Note: Construction of drains may be considered depending on on-site conditions.
(3.3.5) In case R ≦ 1.0 m , h2 = 0.05 H2+1.0
(3.3.6) In case R > 1.0 m , h2 = 0.05 H2+R
Where R :run-up height of waves(m)
(3.3.7) In case B ≥ 3.0 m , B = 0.2 H + 2.0
5. Experience of Czech Republic
The cross section shape of the dam shall be determined in accordance with calculations
to ensure its stability. The standard cross section diagram shown in Figure 5.18 and Table
5.26 shall be used in determining the preliminary cross section shape of the small dam
Table 5.26 – Recommended slopes for small dams in Czech Republic.
Dam sealing Dam Categorization of earths Slopes
90