SMALL DAMS PETITS BARRAGES

For dams with 5 to 15 m height, the following crest width are then recommended.
Table 5.18 – Crest width recommended for small dams – Bureau of Reclamation/87 [3]
Dam Height (m) Crest Width (m)
5 4
10 5
15 6
Many successful small dams have been constructed with crest less than 6 m wide. No
dam should have a crest width of less than 3 m, because this is the minimum needed for an
access road to permit maintenance works.
The French Guidelines for Small Dams observed that for zoned dams their width also
depend on the number of zones at the crest. The following minimum widths are proposed,
depending on their safety parameter H V
2
:
Table 5.19 – Minimum crest widths proposed for small dams (French Guidelines) [5]
Parameter H V
2
< 100 100 to 300 > 300
L minimum 3 m 4 m 5 m
Lewis, 2002 [4] observed that the crest width increases as the height of the dam
increases, and presents the following empirical formula for crest width:
Crest width (m) = H 0,5 + 1
Where H is the height of the crest above the bed stream. Table 5.16 presents the
Australian recommended top width for dams of various heights based on the above formula.
Table 5.20 – Crest width recommended for small dams (Lewis, 2002)
Dam Height
Crest Width
(m)
(m)
4 3.00
5 3.25
6 3.50
7 3.65
8 3.85
9 4.00
In China, at the Hongshiyan homogenous dam, 12 m maximum height, in Hubei
Province, a crest width 5 m had been used, as can be seen in Fig. 5.14.
82