IGEM Report 1: 2017-18 - THE CYCLONE DEBBIE REVIEW

The Cyclone Debbie Review

In this event, perhaps the highest risk to communities was of storm tide inundation, depending on where and to what extent this might impact. Information available from remote sensors and in the Bureau’s own cyclone advices enables them to issue a Storm Tide Warning, containing what are known as “most likely” and “worst case” scenarios. These two, from a spectrum of possibilities, follow direction set out in the T ropical Cyclone Storm Tide Warning – Response System Handbook . 88 However, the technology exists with probabilistic models like SEAtide TM and others being progressively developed by the Bureau to produce outputs so that decision- makers, and ideally the public, can see and easily understand the likelihood of the risk in a particular area. In the case of a storm tide these outputs might be in the form of a simple bar graph for a specific location (see example below). This might show the highest tide, the colours of evacuation zones – which the public already know, together with familiar landmarks – a bridge or headland, with the chances of various storm tide heights superimposed. This has implications for new ways of messaging that we discuss below. In Townsville, inundation level probabilities from SEAtide for particular locations were layered over evacuation zones, to support decisions by the Townsville local group about risks to the community.

Themes

This graph produced by SEAtide™ shows the information to which the Townsville LDMG had access.

Courtesy of DSITI

An example of a future storm tide warning product for potential use in public information and warnings. Based on: Bailey, W. and Preedy, W.; “Decisions, Decisions, Decisions. Basing Townsville’s evacuation decision for Cyclone Debbie on probabilistic storm tide modelling” (Unpublished)

Location: XXXXXX Date and time: DDMMYYhhmm

Local references

HAT

AHD

Evacuation Zones (including probability of inundation)

4.0

5.0

0%

Council Office ground floor

3.5

4.5

0.5%

3.0

4.0

Public hospital ground floor

2.5

3.5

Public hospital carpark

3%

2.0

3.0

Bridge access to CBD inundated

1.5

2.5

Council library ground floor

Australian Height Datum (AHD)

35%

1.0

2.0

Height above Highest Astronomical Tide (HAT)

Coast road inundated

0.5

1.5

Surf Life Saving carpark

High tide mark

90%

0

1.0

75

6 THEMES

Planning: Risk • Storm Tide warnings