FLOOD04994

• County: Statewide
• Community: na
• Basin: Statewide
• Title: Guidelines on Selection of Acceptable Flood Capacity for Dams
• Date: 3/1/2000
• Prepared By: Australian National Committee on Large Dams
• Floodplain - Doc Type: Educational/Technical/Reference Information

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catchment dams. 1'he AEP procedure
assigns a risk probability of 10-7 to the
PMP Design Flood for small catchments
100 km2, but up to' 10-4 for the large
catchment dams,

The alternative upper limits of 10-6 and 10'
S respectively for High B and High C, to
apply whichever is less, will generally
,relate to the small catchments, whereas the
PMP Design Flood will generally relate to
the larger catchments.

The proposed hazard category table for the
Guidelines on Assessment of the
Consequences of Dam Failure is shown
below. Reference should be made to those
guidelines for the full explanation.

AZ.7.3. Base Safety Condition.

With hydrologic loading, there may be
cases, such as small capacity reservoirs
with a large volume inflow f100ll, where a
flood capacity stage is reached such that
the dam break incremental effects are
insignificant or acceptable. Some
authorities consider that if the incremental
effect downstream is less than 300 mm it
is acceptable. '

This stage is generally called the Base
Safety Condition (BSC), USBR (1989, P
1-5), Hawk (1991). The BSC may indicate
an AFC lesser than the fallback or from a
,
risk study, can be accepted on the basis
that a larger flood capacity would give no
safety or economic benefit.

HAZARD CATEGORIES
Reference ANCOLD Guidelines on Assessment ofthe Consequences of Dam
Failure.

Severity of Damage an,~ Lon
Population
at
Risk Negligible Minor Medium M.-jnr
0 Very Low Very Low Low Significant
,
,
Ito 10 Low Low Significant HighC
Notes J and 4 Notes 4 and S NoteS Note 6
lito 100 Significant HighC HighB
Notes 2 and S Note 6 Note 6
Note I
101 to 1000 / HigbA High A
Note 6 Notes 6
Note 2
>1000 Note 3 Extreme
Note 6

With a PAR of 5 or more people, it is unlikely that the severity of damage and loss
will be "Negligible".
"Minor" damage and loss would be unlikely when the PAR exceeds 10.
"Medium" damage and loss would be unlikely when the PAR exceeds 1000.
Change to Significant where the potential for one life being lost is recognised.
Change to High where there is the potential for one or more lives being lost
Refer Guidelines on Assessment of the Consequences of Dam Failure Section 2,7
and 1.6 for explanation of the range of High Hazard Categories

Note I:

Note 2:
Note 3
Note 4:
Note 5
Note 6

ANCOLD Guidelines on Selection of an Acceptable flood Capacity for Dams A2-1 I