SMALL DAMS PETITS BARRAGES

1. SMALL DAMS DEFINITION AND CLASSIFICATION
The term “small dams” has various meanings and perceptions in the world. For some a
20m high dam will be the largest of the small dams category, while others see it as the
smallest large dam. Dams are being defined as having a safety risk when the dam height is
higher than 2m in America and 5m in South Africa, and having a storage capacity of a 30 000
m 3 and 50 000 m 3 respectively.
Furthermore, the concept of consequential damages and loss of life for the case of a
dam failure is widely used for classification of all dams into hazard classes, normally as low,
medium and high. The consequential damages are determined for the inundated area caused
by a dam break flooding event. Dam storage volume, depth of water at the dam wall and time
of the development of the breach are the most important parameters for the determination of
the dam break flood.
Large dams are being defined by ICOLD as any dam with:
maximum height (H), measured from deepest foundation level to highest structure
crest level, more than 15m, or
10m < H < 15m, and the following conditions:
• dam length more than 500 m,
• reservoir storage capacity more than 3 million m 3 ,
• flood discharge more than 2 000 m 3 /s, and
• unusual characteristics in dam type or foundation.
• suggestions and references
1.1 CLASSIFICATION
The French Committee on Dams and Reservoirs has developed a classification system
for dams [1] with two of the main parameters usually used in the determination of a dam break
2
flood, height and storage volume of dam. These two parameters are combined as H . V
with H = maximum height of dam wall in meters, measured from river bed level and V =
storage volume of reservoir at full supply level in million cubic meters. It has no particular
scientific significance, but it is an applicable deterministic “factor” for weighing potential risk of
damages and loss of lives in the dam break flooding area in event of a dam breach. This
combined parameter is used for the classification into low medium and high classes and for
the identification of design criteria applicable to the classes for various design components
mentioned in this bulletin.
The relationship on a log of storage volume to normal dam height scale and some values
are being shown on Figure 1.1.
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