SMALL DAMS PETITS BARRAGES

small dam impounding a lot of water may be as much of a danger as a high dam impounding
little water.
Recent changes in French regulation changed in 2007 the dam classification system,
introducing a graded system with four classes of dams [4]:
A: H 20 m
B: 10 < H < 20 m and H V 200
2
(V in hm 3 )
C: 5 < H < 10 m and H V 20
2
D: 2 < H < 5 m
The authorities may in some cases modify the classification if there are special
circumstances.
The new French classification replaces the all-or-nothing system, whereby dams listed
as a potential danger to public safety absorb massive supervision and monitoring resources,
while others are frequently ignored. It must be acknowledged by Governments that even small
dams are not without risks.
According to the above referred graded system, responsibilities and requirements are
defined as it will be further explained.
The USA Model Law for State Supervision of Safety of Dams and Reservoirs adopts a
different classification system. According to this Model Law, the Dams are defined as any
artificial barrier with ability to impound water and which is: H ≥ 7,5 m and V > 18,450 m 3 , or V ≥
61,500 m 3 and H > 2 m (please note that in the USA this type of dam regulation is a State
matter, not a Federal one, and in some States we may find different definitions according to
their own experience and needs).
The American Model establishes a Hazard Potential classification that does not reflect in
any way on the current condition of the dam (safety, structural integrity etc), but in the possible
adverse consequences of the release of stored water due to failure or mis-operation of the
dam [6]:
I) High Hazard Potential Dam: dam’s failure or mis-operation will probably cause loss
of human life (even if it is only one person);
II) Significant Hazard Potential Dam: no probable loss of human life but can cause
major economic loss, environmental damage, disruption of lifeline facilities, or impact other
concerns;
III) Low Hazard Potential Dam: no probable loss of human life and low economic
and/or environmental losses (losses mostly limited to owner’s property).
Regardless of which classification system each country adopts, it is important that the
Regulation establishes a Risk Prioritization Criteria and based on this classification, defines
responsibilities and requirements.
4.3 THE SUPERVISING AUTHORITY
A unit of the Government must be designated by law to be responsible for
implementation and administration of the Regulation. The Supervising Authority shall be
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