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

:;;
;'i~.
I
I
I
I
I
I
I
I
I
I
I
I
I
II
I
I
I I
I
I

TERM

Freeboard

Full Supply Level (FSL)

Fuse Plug

Imminent Failure Flood (IFF)

Incremental Flood Hazard Category
(IFHC)

Probable Maximum Flood (PMF)

Probable Maximum Precipitation
(PMP)

Recommended Design Flood (RDF)

Spillway

Spillway Design Flood (SDF)

DEFINITION
The vertical distance between a stated water level
and the top of the non-overflow section of a dam.
The part of the freeboard that relates to the flood
surcharge is sometimes referred to as the "wet
freeboard", and that above the flood surcharge,
due to wind and other effects, is sometimes
referred to as the "dry freeboar.d".

The maximum normal operating level of a
reservoir, as distinct from flood surcharge.

An emergency spillway bank designed to fail at a
selected flood level.

As defined in the 1986 ANCOLD Guidelines on
Design Floods for Dams, the flood" event, which,
when routed through the reservoir, with the existing
spillway, just threatens failure of the dam.

The potential incremental losses and damages
directly attributable to the failure of a dam due to
inadequate spillway capacity.

The flood resulting from PMP, and where
applicable snow melt, coupled with the worst
flood-producing catchment conditions that can be
realistically expected in the prevailing
meteorological conditions.

The theoretical greatest depth of precipitation for
a given duration that is physically possible over a
particular catchment area, based on generalised
methods, The estimated PMP is referred to as the
operational estimate of PMP,

In the 1986 Guidelines the recommended annual
exceedance probability flood producing the
highest flood surcharge for the dam, for the
appropriate IFHC.

A weir, channel, conduit, tunnel, gate or other
structure, designed to permit discharges from the
reservoir when pondage levels rise above FSL;
can include secondary, auxiliary, emergency
spillways or fuse plugs.

The flow stage selected from site and other
considerations for the hydraulic design of the
spillway structure, chute and dissipator, under
operational conditions, as distinct from potential,
but low probability extreme floods selected for
overall dam safety.

ANCOLD Guidelines on Selection of an Acceptable flood Capacity for Dams

31