FLOOD01798

• County: Statewide
• Title: Australian Rainfall and Runoff 1998, Revision of Book VI - Estimation of Large to Extreme Floods
• Date: 11/28/1998
• Prepared By: Rory Nathan, Sinclair Knight Merz
• Floodplain - Doc Type: Educational/Technical/Reference Information

UKAI-I U

tsOOK VI- tstlmatlon or Large to txtreme I"'I000S

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Table 2 Summary of procedures to derive Design Rainfalls.

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The credible limit of
extrapolation generally
ranges from 1 in 1 00 to
1 in 5000 AEP

Use of design
estimates based on
regional pooling of data
(Section 3.3.2)

Extrapolation of IFD
data to 1 in 500 AEP
(Section 3.3.1) where
no regional data exists
(applies only to a
limited range of
situations)

All rainfall depths are
for design bursts

For information on
seasonal estimates see
Section 3,7

Generalised IFD
information (Section
3.2); spatial
variation in depths
may need to be
accounted for
(Section 3.10b)

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Not appiicable

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Interpolation to areal PMP
estimate based on either:

shape factors
(Section 3.6.1)

2 paramo parabolic
function (Section 3.6.2)

extrapolation from long
to short duration storms
(Seclion 3.6.3)

See Section 3.2(b) for
discussion on areal
reduction factors

Derived from point design rainfalls by application
of areal reduction factors (ARFs), selected as a
function of storm area, duration, and AEP (design
ARFs based on regional data may not be
available for all regions in Australia).

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See Table 6 for
summary of
interpolation
procedures (applied to
areal rainfalls)

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See Figure 2 for areas
covered by different
generalised methods
Genera/ised methods
yield areal PMP depths
AEP of PMP based
solely on catchment
area, Section 3.5

GSDM for short
durations and small
areas (Section 3-4.2)

GSAM for SE Aust
region (Section 3.4.3)

GTSM for tropical
region (Section 3-4-4)

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Not applicable

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- GSDM pattems for all
short durations

- GTSM patterns for long
durations in tropical
areas

Unsmoothed GSAM for
long durations in SE
Aust

Both GSDM and
unsmoothed GSAM for
intennediate durations
In SE Aust

GSDM patterns for all
short durations

GTSM pattems for all
durations in tropical
areas

GSAM for long
durations in SE Aust.

Both GSDM and GSAM
for intermediate
durations in SE Aust.

GSDM patterns for all
short durations
GTSM pattems for all
durations in tropical
areas
GSAM for long
durations in SE Aust.
Both GSOM and GSAM
patterns for
intermediate durations
in SE Aust

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Unsmoothed
GSAM patterns
for long durations
in SE Aust.

Generalised
patterns (Book II,
Section 2) for all
other cases

Sae Table 8 for
summary of tempora'
pattern selection
Pre-burst temporal
patterns may be used
in conjunction with
storm losses (Section
3.9. Ie)

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See Section 3.10(b) for
discussion on need for
incorporation of spatia'
trend
See Table 9 for
summary of spatial
pattern selection

Use either GSDM, GSAM,
or GTSM patterns,
depending on location and
duration

Uniformly distributed
(unless clear
evidence for spatial
trend)

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