Severe Weather in Victoria:
Impacts and Response
Version 2 – May 2016
Severe Weather in Victoria: Impacts and Response
Disclaimer
This publication is presented by the Victoria State Emergency Service for the purpose of disseminating emergency
management information. The contents of the information have not been independently verified by the Victoria
State Emergency Service. No liability is accepted for any damage, loss or injury caused by errors or omissions in
this information or for any action taken by any person in reliance upon it.
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Severe Weather in Victoria: Impacts and Response
Foreword
The State of Victoria has experienced a number of significant severe weather events in recent history that has both
tested and informed readiness, response and recovery strategies at all levels of government.
Severe storms are estimated to cost A$284 million per annum 1 and can cause significant damage to homes,
businesses and community infrastructure. This represents one quarter of the average annual cost of natural
disasters in Australia. In terms of insured costs, severe storms are responsible for more damage than tropical
cyclones, earthquakes, floods or bushfires 2.
With the increasing intensity of some hazard events, and, changing environmental, social and economic factors,
Victoria State Emergency Service (VICSES), as the control agency in Victoria for storm events, acknowledges the
need for an improved understanding of the severe weather hazard and the broader risks and consequences faced
by Victorian communities.
This document reports the findings of a study undertaken by VICSES into impacts and response to Severe Weather
in Victoria. The study aims to provide useful insights for the Agency and key partners to examine the trends of the
event occurrences across the State and correlations to impacts and responses where available.
Although some evidence is available economic costs of such events (predominantly insurance data and
intelligence) on a National scale; limited studies have been conducted at a State level on the broader impacts and
responses to communities for these events. This study therefore undertook to develop new data and intelligence
for the State of Victoria.
In developing a more detailed understanding of the factors that have led to such situations occurring and how
these events have been planned, managed and communicated before, during and after in the past; the findings
will support the delivery of improved and more sustainable community and organisational understanding and
safety outcomes.
The study is not intended to be a definitive or final report. In areas identified as being particularly prone to severe
weather impacts and responses, further research will be required with key stakeholders in the collaboration,
exchange and sharing of data and intelligence to further explore current and future program and resource
investment.
VICSES also acknowledges the Productivity Commissions report findings on Natural Disaster Funding (May 2015)
taking into account the priority of effective natural disaster mitigation and the reduction in the impact of disasters
on communities.
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Department of Transport and Regional Services (2001), Economic costs of natural disasters in Australia p.41 https://www.em.gov.au/Documents/
economic_costs_of_natural_disasters_in_Australia.pdf
http://www.ga.gov.au/scientific-topics/hazards/severe-weather/basics/what
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Severe Weather in Victoria: Impacts and Response
Availability of Data
VICSES would like to thank State and Commonwealth Agencies that were consulted during this study for their
assistance and in the provision of spatial data for use where available.
It should be noted that studies such as atmospheric modelling or risk exposure databases have either not been
undertaken for the State of Victoria or were not available at a suitable scale for use in this study.
The general unavailability of data influenced and reduced the scope of this study. The initial intent to associate the
weather events with their consequences was unsuccessful due to the predominance of severe weather impacts in
metropolitan Melbourne.
No annual trend projections were possible due to the short time frame of data timeline (approximately 5.2 years)
and the significant variability over those years, likely influenced by one of the strongest La Nina events.
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Severe Weather in Victoria: Impacts and Response
Contents
Foreword
Availability of Data
1.
Introduction
1.1 Introduction
1.2 Risk from Storms
1.3 Purpose
1.4 Storms in Victoria
1.5 Impacts of Recent Severe Weather Events
1.5.1 Windstorm - 2 April 2008
1.5.2 Hailstorm - 6 March 2010
1.5.3 Storm - Christmas Day 2011
1.5.4 Severe Thunderstorm - 21 March 2013
1.5.5 Wind – September through October 2013
1.5.6 Storm and Storm Surge - Warrnambool & Port Phillip Bay June 2014
1.5.7 Summary
2.
Methodology
2.1 Data Availability and Sources
2.2 Scope and Considerations
2.3 Methodology
2.3.1 Data Inclusions
2.3.2 Data Exlusions
2.3.3 Data Analysis
3.
Results & Discussion
3.1 Analysis of Received RFA Data
3.1.1 Analysis of Totals
3.1.2 Analysis of Types of RFAs Received
3.2 Actions undertaken by VICSES
3.3 When does severe weather occur?
3.3.1 Which month does severe weather occur?
3.3.2 What time does severe weather occur?
3.4 Population Trends and Analysis
3.4.1 Population Analysis
3.4.2 RFA Projections
4.
Conclusion
Appendix A1 – Severe weather findings for East Region
1.1 Findings reviewed by VICSES Unit
1.1.1 Which RFAs are received by VICSES East Region?
1.1.2 Which actions are undertaken by East Region SES Units?
1.2 Findings reviewed by Local Government Area
1.2.1 Requests for Assistance received reviewed by Local Government Area
1.3 When are Severe Weather RFAs received in East Region?
1.3.1 What are the temporal trends of Severe Weather RFAs received in East Region?
1.3.2 When are Severe Weather RFAs received in East Region?
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Severe Weather in Victoria: Impacts and Response
Appendix A2 – Severe weather findings for Central Region
1.1 Findings by VICSES Unit
1.1.1 Which RFAs are received by VICSES Central Region?
1.1.2 Which actions are undertaken by Central Region SES Units?
1.2 Findings reviewed by Local Government Area
1.2.1 Requests for Assistance received reviewed by Local Government Area
1.3 When are Severe Weather RFAs received in Central Region?
1.3.1 What are the temporal trends of Severe Weather RFAs received in Central Region?
1.3.2 When are Severe Weather RFAs received in Central Region?
Appendix A3– Severe weather findings for Mid West Region
1.1 Findings reviewed by VICSES Unit
1.1.1 Which RFAs are received by VICSES Mid West Region?
1.1.2 Which actions are undertaken by Mid West Region Units?
1.2 Findings reviewed by Local Government Area
1.2.1 Requests for Assistance received reviewed by Local Government Area
1.3 When are Severe Weather RFAs received in Mid West Region?
1.3.1 What are the temporal trends of Severe Weather RFAs received in Mid West Region?
Appendix A4 – Severe weather findings for North East Region
1.1 Findings by VICSES Unit
1.1.1 Which RFAs are received by VICSES North East Region?
1.1.2 Which actions are undertaken by North East Region Units?
1.2 Findings reviewed by Local Government Area
1.2.1. Requests for Assistance received reviewed by Local Government Area
1.3 When are Severe Weather RFAs received in North East Region?
1.3.1 What are the temporal trends of Severe Weather RFAs received in North East Region?
1.3.2 When are Severe Weather RFAs received in North East Region?
Appendix A5 – Severe weather findings for North West Region
1.1 Findings by VICSES Unit
1.1.1 Which RFAs are received by VICSES North West Region?
1.1.2 Which actions are undertaken by North West Region SES Units?
1.2 Findings sorted by Local Government Area
1.2.1 Requests for Assistance received sorted by Local Government Area
1.3 When are Severe Weather RFAs received in North West Region?
1.3.1 What are the temporal trends of Severe Weather RFAs received in North West Region?
1.3.2 When are Severe Weather RFAs received in North West Region?
Appendix A6 - Severe Weather findings for South West Region
1.1 Findings reviewed by VICSES Unit
1.1.1 Which RFAs are received by VICSES South West Region?
1.1.2 Which actions are undertaken by North West Region SES Units?
1.2 Findings reviewed by Local Government Area
1.2.1. Requests for Assistance received by Local Government Area
1.3 When are Severe Weather RFAs received in South West Region?
1.3.1 What are the temporal trends of Severe Weather RFAs received in South West Region?
1.3.2 When are Severe Weather RFAs received in South West Region?
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Severe Weather in Victoria: Impacts and Response
1. Introduction
1.1
Introduction
The Victoria State Emergency Service (VICSES) is the agency responsible for responding to floods, storms,
earthquakes, tsunamis and their effects, providing rescue services and assisting other emergency services
organisations 1. Response activities are split across six operational jurisdictions, these operational areas, which
align to Local Government Authority (LGA) boundaries are presented in Figure 1.
The State Emergency Storm Plan mandates that VICSES shall work in partnership with support agencies and
organisations to ensure all elements of preparedness, including planning for, response to and recovery from a
storm emergency are managed. However, there is currently a limited knowledge of the locations, trends and
consequences of storm events and this lack of a clear, evidence-based understanding has generally necessitated a
reactive response to storm events.
1.2
Risk from Storms
This study utilises the definitions of ‘risk’ as defined by VICSES’ Community Emergency Risk Assessment (CERA) tool.
Risk = hazard x exposure x vulnerability
Where:
„ Hazard is a dangerous phenomenon, substance, human activity or conditions that may cause the loss of life,
injury or of health impacts, property damage, loss of livelihood, disruption of services etc.
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1.3
Exposure is the people, property or other elements in the hazard zone that are subject to potential losses.
Vulnerability is the characteristics and circumstances of a community, system or asset that makes it
susceptible to the damaging effects of a hazard.
Purpose
In line with the State Emergency Storm Plan, the objective of the study is to improve the understanding of the
severe weather hazard. This will be understood by analysing the exposure of communities across the State to
severe weather and the impacts of these events. An assessment of how VICSES units have responded to severe
weather in the past will help to inform future unit resourcing considerations and readiness activities. Where such
information can be used to inform community understanding and VICSES readiness activities, it may also assist to
reduce exposure and vulnerability.
It is recognised that a number of factors influence the vulnerability of a particular area or community to severe
weather. Older buildings may not meet modern building code requirements; maintenance regimes, the proximity
to and shielding from adjacent properties affect risk, community members may reduce their risk by preparing for
storm events, while the species, size, density and age of trees, along with bushfire, flood and soil water conditions
influences tree stability in high winds. Typically, data at property level to assess such factors is unavailable and
this report is not intended to be a definitive or final study. Rather, it is intended to be a starting point, to provide
baseline data to support VICSES’ anecdotal and operational knowledge, to identify broad regional patterns and be
a baseline for future work. It is envisaged that this data will be used to assist in emergency planning and response
activities, preparedness and as a tool to engage with stakeholders and communities.
Note that this study focuses on storms and severe weather. Riverine or flash flooding is outside the scope
of this work. References to flooding may refer to water leaking through ceilings or similar associated with
building damage. Refer to section 2.3.1 for more information.
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Victoria State Emergency Service Act 2005 (VIC) s.5
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Severe Weather in Victoria: Impacts and Response
1.4
Storms in Victoria
The Victoria State Storm Emergency Plan 2011 identifies a threat to Victoria from storms, dust storms, tornadoes,
snow storms, blizzards, hail storms and severe thunderstorms including hail storms and heavy rain that may lead
to flash flooding 2. Storms can have wide-ranging impacts on transport, power supply and the safety of education
activities (i.e., school bus routes, camps), which requires interagency cooperation to undertake preparation,
response and recovery activities. High wind events may result in tree branches, trampolines, outdoor furniture or
other loose items such as roof tiles becoming flying projectiles. Hail can injure people and damage property while
heavy rainfall may lead to leaking roofs, flash flooding and increased hazards near stormwater drains. On average,
storms cost Victorians an average of $28 million each year and the damages associated with individual storm
events can be significant; the March 2010 Melbourne storm event (refer to Section 1.3.2) incurred damages of $1.04
billion 3, only slightly less than the cost of the February 2009 ‘black Saturday’ bushfires.
Victoria is affected by a number of regional weather patterns that tend to move from west to east. Cold fronts
form when cold dense air moves towards the equator, fronts generally move across southern Australia from
west to east and can bring thunderstorms, hail, heavy rainfall and strong winds 4. The Southern Annular Mode
(SAM) refers to the north-south movement of the band of westerly winds south of Australia. This region of strong
westerly winds is associated with cold fronts and storm activity, and influences weather in southern Australia. A
negative SAM results when westerly wind belt expands and can result in more (or stronger) fronts over southern
Australia 5. Cut-off lows are low-pressure systems that form away from the main belt of low pressure that lies across
the Southern Ocean, they do not move in the traditional west to east pattern and their movement can be difficult
to predict 6. They are associated with sustained, often heavy, rainfall, and can produce strong, gusty winds and
high seas. East Coast Lows are a form of cut-off low 7.
Weather conditions are classified by the Australian Government Bureau of Meteorology (BoM), which separates
severe weather and thunderstorm events. Severe weather comprises potentially hazardous or dangerous weather
that is not directly related to severe thunderstorms, tropical cyclones or bushfires, such as:
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Sustained winds of gale force (63 km/h) or more;
Wind gusts of 90 km/h or more;
Very heavy rain that may lead to flash flooding; or
Abnormally high tides (or storm tides) expected to exceed highest astronomical tide 8.
Victoria State Emergency Service, http://www.ses.vic.gov.au/prepare/em-planning/em-partners-resources/state-storm-emergency-plan p.2
National Climate Change and Adaptation Research Facility – Climate Change Impacts Factsheet (Emergency Management)
Australian Government, Bureau of Meteorology, Frontal Systems, http://www.bom.gov.au/watl/about-weather-and-climate/australian-climateinfluences.shtml?bookmark=fronts Accessed on 12 June 2015
Department of Environment and Primary Industries, Sam, http://www.depi.vic.gov.au/agriculture-and-food/farm-management/weather-andclimate/understanding-weather-and-climate/the-climatedogs-the-four-drivers-that-influence-victorias-climate/sam Accessed on 12 June 2015
Department of Environment and Primary Industries, Eastie, http://www.depi.vic.gov.au/agriculture-and-food/farm-management/weather-andclimate/understanding-weather-and-climate/the-climatedogs-the-four-drivers-that-influence-victorias-climate/eastie Accessed on 12 June 2015
Australian Government, Bureau of Meteorology, Cut-off Lows, http://www.bom.gov.au/watl/about-weather-and-climate/australian-climateinfluences.shtml?bookmark=cutofflow Accessed on 12 June 2015
Australian Government, Bureau of Meteorology, Bureau of Meteorology: Severe Weather Warnings http://www.bom.gov.au/catalogue/warnings/
WarningsInformation_SW_SWW.shtml Accessed on 5 January 2015
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Severe Weather in Victoria: Impacts and Response
For this study, severe weather is generally considered to comprise high wind events, tornados, hailstorms and
severe thunderstorms including hailstorms and heavy rain. Flash flooding is the subject of specialist hydrologic
and hydraulic study and is excluded from this study. The term ‘severe weather’ is used throughout this report in
preference to ‘storm’ to align with this description.
BoM issues severe weather warnings for nine Victorian forecast districts (Mallee, Wimmera, Northern Country,
North East, East Gippsland, West and South Gippsland, Central, North Central and South West). The regional
scale of warning is indicative of the large-scale synoptic events that result in severe weather and the difficulty in
predicting exactly where severe weather will manifest. Weather patterns that may cause severe weather include:
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Recently decayed tropical cyclones moving into southern regions and sometimes interacting with cold
fronts;
East coast lows: deep low pressure systems that can form in the Tasman Sea and affect the Gippsland coast;
Vigorous squally cold fronts;
Strong pressure gradients, often due to cold fronts, causing land gales - particularly in exposed alpine
regions;
Distant tropical cyclones or deep southern low pressure systems that can produce ocean swells that reach
the Australian shores causing dangerous surf; or
Locally intense rainfall, particularly in susceptible areas that can cause flash flooding
Occurrences and locations of severe weather are provided by the BoM’s Severe Storms Archive 9, which contains
reported occurrences dating back to the 19th Century. The locations of severe weather reported to the BoM
between 1900 and December 2013 are provided for hail (refer to Figure 2), lightning (refer to Figure 3), rain (refer to
Figure 4) and wind and tornado events (refer to Figure 5). This database contains reported severe weather events,
if an event was not observed then it will not be recorded, the database therefore provides an indication of the
distribution of severe weather.
Review of over 100 years of reported occurrences of severe weather indicates that the severe weather hazard
is generally distributed evenly across the state.
1.5
Impacts of Recent Severe Weather Events
Recent weather events and the reported impacts are outlined below. Data is sourced from BoM Severe Weather
Summaries, which include total Requests for Assistance received by VICSES and other agencies, such as the
Country Fire Authority and Metropolitan Fire Brigade.
1.5.1 Windstorm - 2 April 2008
A very strong northerly gradient developed during the morning of Wednesday 2 April 2008, which caused gusty
northerly winds affecting central and western Victoria. The maximum wind gust in Victoria was 131 km/h at Mt
Gellibrand (west of Geelong) at 1300 hrs; Melbourne Airport recorded 107 km/h.
VICSES received about 3300 RFAs, mostly for fallen trees, over 2,000 requests were received from the Metropolitan
area. The rail network was severely disrupted and 200,000 homes were without power for various periods.
Lanes were closed on the Westgate Bridge where gusts were close to 120 km/h, many traffic lights were out and
conditions on the roads were chaotic. Several boats were washed ashore at Mornington, where large waves were
observed.
VICSES’ Incident Reporting System (IRS) commenced in July 2009 and no spatial data of the locations of RFAs
received during this event is available.
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Australian Government, Bureau of Meteorology. Severe Storms Archive http://www.bom.gov.au/australia/stormarchive/ Accessed 10 October 2014
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Severe Weather in Victoria: Impacts and Response
1.5.2
Hailstorm - 6 March 2010
A developing low-pressure system with an associated low-pressure trough to the west of Victoria combined with
low-level moisture to generate showers and thunderstorms in the west of the State during the morning of March
2010, which spread eastward and intensified during the early afternoon. Severe thunderstorms developed to the
northwest of the Melbourne metropolitan area and moved through the city from early afternoon progressing to
the eastern suburbs and then into West Gippsland later in the afternoon.
The severe thunderstorms were associated with large hail (≤10 cm were reported) and heavy rain resulting in
widespread flash flooding and water and hail damage to property. There were some isolated severe wind gusts
with the thunderstorms.
Damage was severe, 4232 motor vehicles were damaged in City of Knox alone and 5901 reports of damage to
houses were received. Many people suffered injuries from hail stones; although the exact numbers are unknown,
most received cuts and bruises. Two people were admitted to intensive care with serious injuries.
Locations of RFAs received by VICSES during this event are provided in Figure 6.
The consequences are outlined below:
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1.5.3
The cost of the hailstorm across Victoria has been reported as $2B.
VICSES crew numbers reach 300 per day, with deployments from Victoria, NSW, Tasmania, WA and SA
Red Cross visited more than 4,000 homes
Hardship Grants handed out by Department of Human Services
Storm - Christmas Day 2011
A trough of low pressure developed over Victoria on 23 December 2011, deepening further into 25 December,
before progressing east the following day. The quasi-stationary nature of the surface trough, high moisture, and
wind shear all contributing to the highly unstable atmosphere and severe thunderstorms were forecast for central
and eastern Victoria on both 24 and 25 December.
The worst affected areas were the northern and eastern suburbs of Melbourne including Taylors Lakes, Keilor,
Eltham, Greensborough, Melton and Keilor Downs. Tornadoes hit Fiskville (between Melbourne and Ballarat),
powerful enough to upend cars. VICSES responded to more than 2,000 RFAs in the first six hours; Powercor and
Jemena reported more than 23,300 people without power, Melbourne Airport was closed for a short period of
time.
Locations of RFAs received by VICSES during this event are provided in Figure 7.
1.5.4
Severe Thunderstorm - 21 March 2013
On Thursday 21 March 2013, a low-pressure system and associated cold front crossed southeastern Australia. The
low tracked south of Tasmania while the strong cold front crossed Victoria during the day causing widespread
damaging winds and severe thunderstorms. Wind gusts in excess of 100 km/h were recorded at many locations,
with the highest gust of 126 km/h recorded at Mt Buller.
The cold front triggered severe thunderstorms as it moved eastwards across the State. A supercell north of
Yarrawonga was associated with damaging winds, hail and at least one tornado, possibly more, caused significant
damage to buildings, and overturned caravans. At least 20 people were treated for injuries.
Severe Weather Warnings and Severe Thunderstorm Warnings were issued well in advance for this system, warning
of potentially damaging winds and large hail for the entire state. VICSES received over 1000 RFAs during the
day due to the widespread nature of damaging winds, approximately 150 of which were in the northeast where
the most intense severe thunderstorms occurred. Towns affected included Koonoomoo, Cobram, Yarrawonga,
Bundalong, Rutherglen and Mulwala.
Locations of RFAs received by VICSES during this event are provided in Figure 8.
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Severe Weather in Victoria: Impacts and Response
1.5.5
Wind – September through October 2013
Melbourne experienced a number of severe and prolonged wind storms, which predominantly came from the
South during late September/Early October 2013. The metropolitan area of Melbourne was badly hit; the reported
consequences of 26 September 2013 are outlined below:
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Reported power disruptions – Jemena 982, Citipower 812, Powercor 1559, United Energy 659, and SP Ausnet
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Train delays and cancellations on most lines
The Melbourne Show was forced to close early
A 4.9m aluminium boat sank on Port Phillip, the 78-year-old occupant was treated for hypothermia
A man was injured when tree branch fell near Cranbourne Shopping Centre
Numerous reports of trees falling on houses and cars
Wind and waves damaged beach boxes at Mount Martha
Flash flooding affecting roads at South Melbourne, Middle Park, and Narre Warren
A deep low-pressure system traversed the Southern Ocean on 30 September as a cold front amplified across the
southeastern states and swiftly crossed Victoria during 1 October 2013. Gale force north to northwesterly winds
developed across Victoria late on Monday 30 September, with damaging gusts reaching 90-100 km/hr in western
Victoria and about elevated areas during the afternoon. These extended to central parts of the State in the early
hours of Tuesday morning, where widespread gusts of 100-120 km/hr were recorded in various suburbs around
Melbourne. The highest recorded gust was 142 km/hr at Fawkner Beacon.
By midday on Tuesday 1 October, VICSES had received 3147 RFAs, most of them in relation to building damage and
trees down/traffic hazards. Over 53,000 properties were without power during the evening of 1 October.
Strong northwesterly winds developed across Victoria early on Wednesday 2 October, with gusts reaching 90-100
km/hr and 110 km/hr in elevated areas. Isolated thunderstorms developed along the cold front as it moved rapidly
east, becoming most active as it moved across the Central District during the early afternoon. Wind gusts of 100110 km/hr were recorded over Port Phillip in the vicinity of thunderstorms.
By 5 pm on Wednesday, VICSES had received almost 1700 RFAs, most of them in relation to trees down and minor
building damage around Melbourne suburbs. The locations of RFAs that were received during the severe weather
than occurred in Victoria during September and October 2013 are provided in Figure 9.
1.5.6
Storm and Storm Surge - Warrnambool & Port Phillip Bay June 2014
Strong north to northwesterly winds developed across Victoria during the morning of Monday 23 June 2014,
ahead of a strong cold-front approaching from the Bight. Damaging gusts were experienced, mainly over elevated
areas and the far south, very cold air spread across the State with the front leading to unstable conditions, which
resulted in thunderstorms over central and northeastern Victoria as well as near the southwest coast.
A re-strengthening of winds occurred early Tuesday 24 June as a deep low-pressure system moved into Bass
Strait. Wind gusts up to 110-120 km/h were observed early in the morning, with the strongest winds around the
Melbourne region occurring between around 10:30 am and 2 pm with mean winds above gale force at many
locations and gusts up to 120 km/h.
VICSES received around 2500 RFAs on 24 June, a wall collapse at a construction site in Brighton East on the
morning of 23 June resulting in one death and the system on Tuesday coincided with high tides to create a
storm surge along parts of the coast and Melbourne’s Southbank. Damage to a barrier/wall at the Merri River in
Warrnambool resulted in some flooding and residents being evacuated. Localised flooding disrupted a number
of roads and tram routes while fallen trees resulted in the suspension of some train lines just ahead of the evening
peak hour. Up to 80,000 homes across the State were without power.
Locations of severe weather RFAs received by VICSES during this event are provided in Figure 10. Note that storm
surge is not shown on Figure 10.
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Severe Weather in Victoria: Impacts and Response
1.5.7
Summary
A review of historic and recent severe weather events indicates that while the hazard from severe weather is
distributed across the state, exposure is concentrated in metropolitan Melbourne and larger regional towns.
The distributions of impacts vary, events may have a relatively even spread of damages, such as from the June
2014 and 2013 Thunderstorms, or damage may be concentrated, with pockets of building damage in north and
east Melbourne clear from severe weather events in 2010 and 2011. The regional-scale nature of severe weather
means that areas at risk are difficult to predict on a less than regional scale, as suggested by warnings issued to
BoM’s severe weather districts. Identifying those locations that have sustained historic damage and using the
local knowledge from the range of emergency service organisations may help to identify the factors influencing
vulnerability at a local scale.
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Severe Weather in Victoria: Impacts and Response
2.
Methodology
2.1
Data Availability and Sources
The exposure and vulnerability from severe weather is influenced by a number of complex factors, such as
elevation, topography, proximity of building or trees, and construction age and materials. Information of this
type at a property level is generally unavailable. Therefore, the consideration and assessment of data availability,
coverage and reliability is an essential precursor to developing a methodology.
Review of severe weather on a statewide basis requires a consistent spatial data set. Data available to VICSES
includes that developed in-house, such as RFA data and VICSES specific spatial data. RFAs are placed by the public
in response to actual or imminent occurrence of an event which in any way:
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Endangers or threatens to endanger the safety or health of any person
Destroys/damages or threatens to destroy/damage any property
Endangers or threatens to endanger the environment or an element of the environment
RFA data includes a number of fields, including date, type, address, responding unit, actions undertaken and
x- and y-coordinates. Various spatial and tabulated data is available from the Victorian Government including
information relating to LGA boundaries, roads and other infrastructure, vegetation and tree density and urban
growth areas. Tabulated population estimates at LGA scale were provided by the then titled Department of
Transport, Planning and Local Infrastructure (DTPLI).
BoM reported that they do not currently hold information on locations at risk from severe weather nor are records
kept of the movements of storms. BoM provided Severe Weather Summary Reports covering the period from
2009 to 2014, which outlined the weather conditions and consequences of a range of severe weather, including
high wind events, storm surge and tornados. Relevant data from these summaries has been provided in Section
1.3. BoM also provided historic severe weather data for a range of severe weather elements (high wind, rain, hail,
lightning and tornado). These are presented in Figure 2 through Figure 5.
Geoscience Australia (GA), which undertakes a range of environmental risk assessment, modelling and analysis
was approached to determine whether relevant data was available. GA reported that its atmospheric modelling
activities are focussed on risk from tropic cyclones and do not cover non-cyclonic weather events as would be
expected in Victoria. GA did confirm that some work had been undertaken to estimate the probabilities of highwind events in Victoria. However, it was reported that this data was archived and it was unclear how old this
information was or its suitability for this study. A request was made for this data but it has not been forthcoming.
GA’s National Exposure Information System (NEXIS) database is a nationally consistent database of building assets,
essential infrastructure, economic activity and demographic information. However, the property level data is
unavailable outside of GA and summaries at LGA or census unit level were insufficient for this study.
Discussions with relevant agencies revealed that studies and data suitable to support the objectives outlined
in Section 1.2 do not exist or are unavailable to VICSES. This study therefore requires undertaking study not
previously examined by state or Commonwealth agencies for Victoria.
2.2
Scope and Considerations
Initial scoping discussions were held with VICSES representatives from Central and Mid West Region. Discussion
with Central Region was held on 10 September 2014 at VICSES’ Mulgrave Office. Two Manager Regional
Operations and one Regional Officer - Emergency Management attended. Generally, Central Region knows where
its highest risk areas are and believe that the consequences from severe weather are generally predictable across
the metropolitan region, dependent on wind speed and direction and the time of day. Tree height, species and
age were identified as important factors in storm damage and typically, a greater proportion of trees led to fewer
instances of roof damage, but a greater proportion of tree related jobs.
Central Region sought evidence to support activities undertaken by VICSES such as the Community Emergency
Risk Assessment (CERA) process, for which VICSES is the storm subject matter expert and to aid the suggested
development of a storm section for Municipal Flood Emergency Plans. To support this, it was proposed that
50 severe weather RFAs received in a 24-hour period should be the threshold where the use of RFA data was
proposed, this broadly aligns to what would be considered a ‘significant’ storm event in a CERA assessment.
7
Severe Weather in Victoria: Impacts and Response
Notwithstanding, 50 RFAs would generally be considered a very low-end event in Central Region. It was also
noted that the IRS does not capture all RFAs, for example, units may complete a job without recording it. It was
estimated that during significant events, the reported RFA totals may include a ‘fudge factor’ of up to 15%. It was
recommended to seek information from insurance companies.
A lack of public understanding of weather warnings was noted and a document that explained what the language
used in severe weather warnings means was identified as a requirement. Data on historic consequences may
assist council preparedness activities. It was also noted that there seemed to be an increasing number of smallscale weather events for which no warning was received from BoM.
Discussions were also held with the Regional Manager of Mid West Region on 10 September 2014. Mid West
Region know the areas that are more susceptible to storm damage, which is influenced by building age and tree
density. Building damage leads to building elements, especially roofs, being updated to meet modern building
code requirements; it is considered that this will reduce the incidences of RFAs in the future. Visual outputs were
recommended, with Municipal, Unit and suburb level outputs recommended.
2.3
Methodology
To allow comparison of areas, the selected approach needed to utilise similarly detailed information.
Consideration was given to a number of different approaches with varying levels of detail, complexity and outputs,
although ultimately, the availability of data was the primary constraint and consideration. The use of LiDAR digital
terrain data collected by the Department of Environment, Land, Water and Planning was considered. Insurance
companies have been reported to assess risk from severe weather and base associated premiums on roof size
information captured from analysis of LiDAR data. This approach was considered and discarded due to cost and
the lack of a clear correlation between roof size and areas of risk.
Given the complexities of the factors influencing risk and the lack of property level data, it was decided to use
VICSES RFAs as the primary data source. This data covers the entire state and is a relatively reliable and validated
data set. Notwithstanding, it was reported by Central Region that up to 15% of RFAs may not be captured in the
IRS during significant storm events, this dataset therefore provides an estimate of the number and location of
reported damage from severe weather. Secondary sources comprise BoM severe weather summaries, with a view
to determine whether different synoptic weather events had different consequences and population projection
provided by DTPLI.
RFA data was imported into MapInfo GIS and matched to its location based on x- and y- coordinates or address.
This dataset was analysed to identify locations at risk and patterns in the data that may assist response and
planning activities.
2.3.1
Data Inclusions
Severe weather related data was extracted from VICSES’ Incident Reporting System (IRS) by VICSES State
Operations. Data was extracted for the period between 1 July 2009 (when the IRS commenced) and
9 September 2014 (when the study commenced) for days where over 50 storm related RFAs were received. This
number broadly aligns with what would be a considered a ‘significant’ storm event under CERA. A total of 74,879
RFAs were provided.
The IRS codes utilised response codes with a primary incident type of ‘storm’ and included responses relating to
the following categories:
„
Tree Down refers to trees fallen on private roadways, limiting access. (IRS codes 101-107). Note that a tree
that falls on a residence or building would be classified as Building Damage.
„ Tree Down Traffic Hazard refers to a fallen tree that is fully or partially blocking a public carriageway. (IRS
codes 111-117).
„ Building Damage refers to damage to single or multi-storey residences or auxiliary buildings such as sheds or
outbuildings. (IRS codes 131-139).
Note that there is a difference between how a RFA is received and how it may be reported by the responding
VICSES Unit. For example, water leaking through a ceiling may be reported to the ESTA call taker as a flood related
job, but classified and reported by the VICSES Unit responding as a Building Damage related job.
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Severe Weather in Victoria: Impacts and Response
2.3.2
Data Exlusions
Any IRS code not specifically mentioned in Section 2.3.1 or reported in IRS with a primary incident type of
Building Damage, Tree Down or Tree Down Traffic Hazard has been excluded from this report. Therefore, any
activities relating to riverine or flash flooding (refer to IRS codes 121 – 127), road or other rescue activities and IRS
code not specified in Section 2.3.1 are excluded.
2.3.3
Data Analysis
RFA data was imported into MapInfo GIS and matched to its location based on x- and y- coordinates or address.
This dataset was analysed to identify locations at risk and patterns in the data that may assist response and
planning activities.
Records were matched to location using two methods, either by matching the record to the receiving SES Unit
or by coordinate data. Not all records could be matched using the receiving unit name, for example; records for
Mid West RHQ Support, Central RECC and South Australia SES could not be matched. In total, 74,870 records were
matched by VICSES Unit.
IRS data was also imported to MapInfo and mapped based on the coordinates provided by the Emergency
Services Telecommunications Authority when logging the RFA. Mapping using these coordinates provided the
locations of 61,367 records, 13,294 records had coordinates that placed them south of Australia in the Southern
Ocean. A range of alternative projections was tested but to no avail. These remaining records were geocoded
using address data contained in the IRS records and VicMap’s Address spatial dataset. This resulted in an additional
9,233 records being matched to location.
In total, 70,600 RFAs were matched to location, leaving 4,610 records unmatched (6%). This is likely to be due to
insufficient address details or indicative locations, such as the corner or intersection of roads that could not be
geocoded. Notwithstanding, it is considered that matching 94% of records to their spatial location provides a
sufficiently representative sample for spatial analysis.
The locations of the matched RFA records are provided in Figure 2. A summary and comparisons of the address
matched IRS and total data set are presented in Table 1.
Table 1: Comparison of IRS and location matched records
RFA Type
Building Damage
Tree Down
Tree Down Traffic Hazard
Flooding
*Other
TOTAL
Original IRS
Count
24,817
24,173
23,621
1,235
1033
74,879
Location
Matched Count
23,593
23,235
21,833
1,156
783
70,600
Location
Unmatched
1,224
938
1,788
79
581
4,610
Percentage
matched
95%
96%
92%
94%
74%
94%
*Other may include SES incident other, message, assist fire service, assist police agency liaison, assist ambulance, rescue
persons trapped, rescue structure collapse, assist agency, ICC, rescue road trap, animal incident, assist crime scene, other
Public relations and SECC
Population data for 2011 was obtained from the Victorian Government’s official population and household
projections, Victoria in Future 2014, provided from the Department of Transport, Planning and Local Infrastructure
10
. Tabulated population data and projections were imported into MapInfo and then matched to its location.
Population data was used to determine the number of RFAs received per capita. Population projections were also
reviewed with a view to correlate population growth with projections of future loadings of units.
10
Total population, households and dwellings http://www.dtpli.vic.gov.au/data-and-research/population/census-2011/victoria-in-future-2014/vif2014-data-tables
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Severe Weather in Victoria: Impacts and Response
3.
Results & Discussion
As outlined in Section 2, 74,879 severe weather related RFAs were provided by VICSES’ State Operations for the
period between 1 July 2009 and 9 September 2014, a period slightly greater than five years.
74,870 records were matched based on VICSES Unit name and 70,600 were matched based on coordinates or
address. Locations of severe weather RFAs are provided in Figure 11.
Generally, information provided in the main body of this report has described statewide trends. Region specific
information and summaries are provided in the Appendix A1 though Appendix A6, which include the following:
„
„
„
„
„
„
A tabulated summary of severe weather RFAs received by each unit
A tabulated summary of the actions undertaken by each unit
A tabulated summary of severe weather RFAs received in each region’s LGA
Maps for each LGA showing the location and type of severe weather RFA received 11
A summary of the annual breakdown of RFAs received by each LGA over the study period
A summary of when during the year the most severe weather RFAs are received by the region
3.1
Analysis of Received RFA Data
3.1.1
Analysis of Totals
Table 2 confirms that severe weather related RFAs are concentrated in VICSES’ Central Region, which generally
covers metropolitan Melbourne (refer to Figure 1). LGAs and VICSES units that receive the greatest number of RFAs
are presented in Figure 12 and Figure 13, respectively. Note that the data provided for this study did not include
any RFA allocated to the Wyndham West Unit. Location matched data identified 833 RFAs falling within Wyndham
City Council’s LGA and 134 within the Unit’s footprint. Note that the total number of RFAs received is 74,874 rather
than 74,789 as some RFAs were located outside of Victoria.
Table 2: Summary of RFAs across Victoria
Region
Central
East
Mid West
North East
North West
South West
Total Number of RFAs
52,360
5260
3955
4391
5028
3880
Percentage
69.9%
7.0%
5.3%
5.9%
6.7%
5.2%
As would be expected based on Table 2, Units based in Central Region generally received the greatest number
of RFAs. With the exception of Ballarat Unit, which received 1962 RFAs over the study period (11th place); the 20
highest totals were received by Units in Central Region. Tabulated summaries are provided in the region specific
Appendices.
To provide a normalised assessment of risk, RFA totals were divided by population data to provide a per capita
value i.e., the number of RFAs received per head of population. Population data for 2011 was provided by the then
Department of Transport, Planning and Local Infrastructure. This analysis (refer to Figure 14) shows that contrary to
the absolute numbers which suggested a concentration of risk in the metro areas, the per capita risk from storm
events is spread across the state, with much of Mid West Region and areas peripheral to metropolitan Melbourne
receiving a proportionately greater number of severe weather RFAs.
11
With the exception of Central Region, whose GIS specialist will undertake mapping activities
10
Severe Weather in Victoria: Impacts and Response
As discussed in Section 1, RFAs are being used as a proxy for the incidence and distribution of severe weather. This
approach is not without its flaws, especially when drawing conclusions for regional areas. As demonstrated by
BoM’s Severe Weather Archive (refer to Figure 2 through Figure 5), severe weather historically has been relatively
evenly distributed across the state. However, the anecdotally reported greater resilience of regional communities
is expected to result in fewer RFAs being reported in regional areas. For example, instead of placing a RFA to
VICSES about a fallen tree, it might be cleared by a farmer using his own tractor and chainsaw. Furthermore, not all
parts of Victoria are covered by the same level of service and awareness of VICSES’ services in these areas may be
limited.
To remedy this, other data sources are required to add to and validate the RFA data. In particular, insurance data
relating to building and property losses or damages to crops would help to build a more complete picture of
the exposure from severe weather and factors influencing vulnerability. It is also recognised that not all rural
communities are serviced by VICSES. In such locations, the local Country Fire Authority (CFA) unit may undertake
severe weather response activities. It is therefore also recommended that severe weather RFA data from the CFA,
as well as the equivalent from the Metropolitan Fire Brigade, are obtained and incorporated into the dataset.
3.1.2
Analysis of Types of RFAs Received
Severe weather RFAs received during the study period are summarised in Table 3. As would be expected from
high wind and stormy weather, the greatest number of RFAs relate to building damage and trees fallen on roads
or property. The most common RFA type in each LGA is shown in Figure 15. This indicates that tree down traffic
hazard is the most received RFA over much of the state. A pocket where building damage dominates is located
towards the northwest of the state, while the Melbourne metropolitan region tends to be split between building
damage and tree down. It generally appears that built up areas, for example, metropolitan Melbourne, Ballarat,
Shepparton and Wodonga are prone to building damage from severe weather events.
Table 3: Breakdown of Received RFAs
RFA Type
Building Damage
Tree Down
Tree Down Traffic Hazard
Flooding
Other*
TOTAL
Total Received
24,817
24,173
23,621
1235
1033
74,879
Percentage
33.1%
32.3%
31.5%
1.6%
1.4%
100.0%
*Refer to Table 1 for a breakdown of ‘others’
3.2
Actions undertaken by VICSES
Actions undertaken by VICSES units are classified in the IRS. ’No action taken’ denotes that there was no response
activity required, i.e. no chainsaws were used. SES members still assessed the incident either via phone or onsite
and provided additional information to the complainant. This advice may involve community education or
referring the complainant to another service provider. Furthermore, a ‘no action’ may be the result in a late night
call waking a volunteer’s household and a conversation with the requestor that results in a decision not to attend,
which may have a significant impact on volunteers. It is also understood that some units have agreements with
Councils to undertake tree clearing from roads.
Detailed unit breakdowns are provided in the region specific appendices in Appendix A. Detailed analysis of unit
responses is generally outside the scope of the study. However, these figures may assist with planning around unit
resourcing and training.
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Severe Weather in Victoria: Impacts and Response
Table 4: Actions Undertaken by VICSES Units
Action Undertaken
Triaged
Cutting, moved with chainsaw
*
Referred to contractor
Assessment, collect incident details
Moved, made safe
*
Referred to council
Replace roofing material
Roof top safety system used
Tarping
*
Referred to power company
Isolated, stabilising
Cutting, moved with other saw
Unspecified
Cleared pipes, gutter
Shoring
Traffic management
Sandbagging
Window, shutter service
Lighting
TOTAL
*
Total
Percentage
17,441
17,242
9569
9387
5468
3696
2482
1982
1850
1806
1592
1344
608
287
127
111
82
76
66
75,210
23.2%
22.9%
12.7%
12.5%
7.3%
4.9%
3.3%
2.6%
2.5%
2.4%
2.1%
1.8%
0.8%
0.4%
0.2%
0.1%
0.1%
0.1%
0.1%
100.0%
* Denotes that there was no response activity required, i.e. no chainsaws were used. SES members still assessed the incident
either via phone or on-site and provided additional information to the complainant. This advice may involve community education
or referring the complainant to another service provider.
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Severe Weather in Victoria: Impacts and Response
3.3
When does severe weather occur?
3.3.1
Which month does severe weather occur?
The Victoria State Emergency Storm Plan recognises that “most severe thunderstorms occur between October and
April. January is the most active month for Severe Thunderstorms followed by December then November 12”. This is
based on data provided by the BoM for reported severe weather events that occurred between June 2000 and
June 2010. An extract from the Storm Plan is provided in Chart 1.
Chart 1: Severe Weather occurrences in Victoria as reported by the State Emergency Storm Plan (June 2000
to June 2010)13
The data provided in the storm plan generally corresponds with the data extracted from the BoM’s severe storms
archive, which provides 2,779 records for the period between 1900 and December 2013. The data shows that
severe weather (comprising rain, hail, wind, tornado and lightning) occurrences peak in December and January.
However, analysis of the occurrence of RFAs received by VICSES does not agree with this timing and indicates that
the consequences of severe weather are greatest during August and September (refer Chart 2, overleaf).
What may explain this disparity? There is little evidence that regional variations are skewing results, Central Region
received approximately 70% of the storm related RFAs during the study period; however, there is close similarity
between the patterns of occurrence between Central Region and the rest of the state. This suggests that the fiveyear RFA record may be anomalous across the 110 year range of BoM archive data or peak occurrences of severe
weather related RFAs are associated with something other than the reported occurrences of severe weather.
12
13
Victoria State Emergency Service (2011), State Storm Emergency Plan. June 2011 p. 3
Victoria State Emergency Service (2011), State Storm Emergency Plan June 2011 p. 4
13
Severe Weather in Victoria: Impacts and Response
Chart 2: Comparison of BoM Severe Storm Archive (1900-2013) and SES Data (2009-2014)
RFA records and records from the severe storm archive that correspond to the same period (July 2009 to December
2013) were extracted to provide a comparison across a corresponding date range. This provided a total of 413
records from the severe weather archive (Wind 88, Hail 95, Rain 190, Tornado 40) and 65,433 RFA records. This data
is shown in Chart 3, which illustrates an even poorer correlation, especially around February, March, August and
September.
Chart 3: Comparison of BoM Severe Storm Archive and VICSES Data (2009-2013)
14
Severe Weather in Victoria: Impacts and Response
The difference may be partly explained by continental scale climate variations, in particular the Southern
Oscillation Index, which gives an indication of the development and intensity of El Niño or La Niña events in the
Pacific Ocean. The 2010–12 La Niña event consisted of two peaks over successive summers; the 2010–11 peak
was one of the strongest on record and these years were the third-wettest and second-wettest calendar years on
record for Australia and resulted in extensive flooding across Victoria. This may have resulted in RFAs classified as
‘flood’ rather than ‘storm’ in VICSES’ IRS which may not have been captured in the data used for this study.
A further possible explanation is that severe weather events during August and September are fewer, but more
severe than those during the summer months. There is little evidence to support this supposition apart from the
raw numbers in Chart 3 and consideration should be given to determining how this discrepancy may be answered.
More research into the occurrences of severe weather is recommended. A greater understanding of how
climate variances may affect incidences of severe weather may assist emergency planning, improve the
strategic view for resource planning, and inform the timing of VICSES activities such as Stormsafe Week.
3.3.2
What time does severe weather occur?
The Victoria State Emergency Storm Plan comments on the timing of severe thunderstorms rather than the
more general severe weather, as defined in this report. The Storm Plan recognises that severe thunderstorms
can occur at any time of day; however, “it is the afternoon and evening period when severe thunderstorms are
more frequent”. An extract from the State Emergency Storm Plan showing the timing of severe thunderstorms is
provided in Chart 4.
Chart 4: Times of reported Severe Thunderstorm Events between July 2000 and June 2010
Data from the BoM’s severe storms archive was used to review when severe weather has historically been reported.
15
Severe Weather in Victoria: Impacts and Response
As noted in Section 1, this dataset contains reported severe weather events (classified as rain, hail, wind, tornado
and lightning), if an event was not observed then it was likely not recorded, the database therefore provides an
indication only of the distribution of severe weather. The archive provides 2,779 records for the period between
1900 and December 2013.
Chart 5 shows the reported timing of severe weather between 1900 and 2013. It is worth noting that all of the
records from 1900 to 1959 and many after have a time of midnight, this is considered to represent a null time entry
and as such 687 records that report the time of occurrence as midnight have not been included.
Chart 5 clearly shows that historically, severe weather has been generally reported in the early morning.
The reason for this is not known. It may be that historically, severe weather events that occurred during the
evening or night were reported the following morning i.e., there may have not been a telephone, or perhaps
damage was more readily observed in the morning. No details of this nature are provided in the Severe Weather
Archive and as such, this anomalous record is unexplained.
Chart 5: Occurrence of Severe Weather as reported in BoM’s Severe Storm Archive (1900-2013)
The times that RFAs were placed has also been reviewed. Anecdotally, severe weather RFAs are considered to
coincide with the return of workers to their homes in the early evening and it was requested that this assumption
be tested. In May 2015, State Operations provided a time related dataset for the same date range as previously
requested, being approximately 75,000 records for the period between July 2009 and September 2014. The
incident_datetime (Call Accepted) field was used and timing rounded to the nearest hour.
16
Severe Weather in Victoria: Impacts and Response
Chart 6: Timing of Receipt of RFAs by VICSES (2009 – 2014)
Findings are reported in Chart 6, which shows that while a peak does occur between 4 pm and 6 pm, this
proportion is only about 1% greater than the period between 10 am and 7 pm, suggesting that severe weather
RFAs are generally received throughout the day. However, review of when RFAs are received in each region (refer
Chart 7) indicates a few regional differences, in particular:
„
„
East Region tends to receive the greatest number of RFAs between 11 am and 2 pm
North East and North West Regions tend to receive the greatest number of RFAs between 5 pm and 9 pm
As reported during consultation, anecdotally, severe weather RFAs are expected to follow a distribution similar to
that reported in the State Emergency Storm Plan, with the greatest number of RFAs received during the evening.
Whether data provided as part of this study supports or contradicts this anecdotal knowledge may depend on the
region.
Ultimately, this study suggests that if severe weather RFAs do not peak outside of typical working hours, then
the impacts on volunteers to respond to these incidents may be greater than previous thought.
This therefore also raises questions as to the RFAs that VICSES receives. As noted, approximately a quarter of
RFAs result in no action. Is the assessment or referral of these RFAs impacting on volunteers’ capacity to deliver
day-to-day work requirements? This question is generally outside the scope of this study, but further review is
to determine whether these questions need to be answered.
17
Severe
Weather
in in
Victoria:
Impacts
and
Response
Severe
Weather
Victoria:
Impacts
and
Response
Chart 7 Comparison of the timing of Receipt of RFAs across VICSES Regions (2009 – 2014)
18
Severe Weather in Victoria: Impacts and Response
3.4
Population Trends and Analysis
RFA data was analysed against population data and projections provided by the Victoria in Future 2014 Study. This
dataset provides the estimated resident population for each Local Government Area for the period between 2011
and 2031.
3.4.1
Population Analysis
Trends of populations and rates of population increase were assessed against RFA totals. The first review plotted
municipal populations (for 2011) against the total number of RFAs received in that LGA throughout the study
period. Chart 8 (Note log/log scale) displays a clear relationship between the total number of RFAs and population.
Chart 8: Relationship between LGA Population and RFA Totals
However, somewhat counterintuitively, Chart 9 (overleaf) indicates that the greatest number of RFAs are received
from the slowest growing LGAs, suggesting that older, established suburbs are more prone to damage from severe
weather. This may be due to older houses built under a less stringent building code or different building materials,
or trees having matured causing significant damage if they fall over in strong wind. Conversely, newer areas will
be built to modern building standards and trees may be immature or sparse. This suggests the potential for newer
suburbs to be problematic in 20-30 years when trees are fully-grown. Note that Chart 9 is produced on a log-log
scale.
19
Severe Weather in Victoria: Impacts and Response
Chart 9: Relationship between Population Growth and RFA Totals
3.4.2
RFA Projections
Location matched RFA data for the period between 1 July 2009 and 9 September 2014 (n = 70,600) was split into
calendar year and then matched to the Local Government Area in which it was reported. Datasets for 2009 and
2014 are for incomplete calendar years. To estimate full years, it was assumed that the period of record – 183
days for 2009 and 252 days for 2014 was representative of the entire year. The RFA totals for 2009 and 2014 were
multiplied by the ratio of full calendar year to days of record i.e., 2009 data was multiplied by 365/183 and 2014 by
365/252 to provide a representative annual dataset.
This provided annual RFA totals for 2010, 2011, 2012 and 2013 and estimates for 2009 and 2014. Each LGA in a
VICSES Region was plotted to identify broad trends. Trends were determined by fitting a linear line of best fit to
each LGA dataset and calculating the y value (slope) as an approach to estimate the average annual change in an
LGAs RFA total. It was hoped that this would provide a means to identify trends and allow an estimation of future
RFA totals. However, due to the short period of data analysed (approximately 5.2 years) and the large range of
most regions, this method was not considered robust enough for use.
Consideration was also given to whether rates of population increase could be viewed in conjunction with RFA
rates to estimate future totals. However, this method also did not provide any usable results. Therefore, the length
and annual variability of the dataset does not support its use to estimate future RFA projections.
20
Severe Weather in Victoria: Impacts and Response
4.
Conclusion
Following a high wind event in June 2014, VICSES sought to improve its understanding of the impacts from severe
weather.
State and Commonwealth Agencies were approached to determine whether existing bodies of work may assist
in this process. While some data was provided, discussions with GA and BoM confirmed that studies such as
atmospheric modelling or risk exposure databases have either not been undertaken for Victoria or are not
available at a suitable scale for use. This study therefore undertook to develop new data and intelligence for
Victoria.
Ultimately, spatial data provided by the Victorian Government was utilised in conjunction with records from
VICSES’ Incident Management System. The latter provided approximately five years of data relating to severe
weather and in the absence of a comparable statewide, consistent and relatively validated and reliable dataset was
selected to be the primary data source.
Approximately 75,000 RFAs were provided for the period between July 2009, when the IRS commenced to
September 2014, when the study commenced. Of this dataset, 70,600 records were matched to location using
either coordinates or address data; either dataset was used depending on the analysis. The findings indicate that
severe weather consequences are split broadly into three categories, building damage, tree down, and tree down
traffic hazard, with approximately 4% comprising other categories.
Location data confirmed that the greatest number of severe weather RFAs were received from the Melbourne
metropolitan region, which received 52,360 RFAs during the study period, about 70% of all RFAs, while regional
areas received approximately 4-5,000. Urban centres peripheral to Metropolitan Melbourne were also prone to
damage from severe weather. These risk areas were generally known anecdotally or by VICSES regional staff.
As would be expected based on the data source, the results demonstrate that risk from severe weather generally
follows population and infrastructure; roads and population centres were clearly visible. A review of population
data confirmed the generally expected trend that RFAs increase in relation to population. More unexpected was
a negative trend between the population growth rate and RFA total, with the fastest growing LGAs displaying the
lowest totals. This may be due to greater resilience from modern building standards.
The dominance of RFAs from the metropolitan region does not necessarily mean that severe weather occurs
more in these areas; rather, this more reflects the density of population and property and may also reflect the
anecdotally understood greater resilience of regional populations. A more complete picture of risk requires
additional data sources, in particular, insurance and RFA data from other agencies.
A review of the actions of VICSES demonstrated that nearly a quarter of all RFAs (23%) resulted in a classification of
‘no action’. This may indicate the receipt of RFAs for work outside the general scope of VICSES’ activities, which if
correct, may be evident of a lack of understanding amongst the public as to the responsibilities of VICSES and its
status as a volunteer emergency service organisation.
Anecdotally, severe weather RFAs peak in the early evening as workers return home and find property damage.
VICSES IRS data supports this but also indicates that RFAs are received throughout the period from 10 am to 7 pm.
This generally correlates well to the occurrences of severe thunderstorms, but suggests that impacts to volunteers’
day-to-day activities may be greater than previously expected.
The general unavailability of data influenced and reduced the scope of this study; the initial intent to associate the
weather events with their consequences was unsuccessful due to the predominance of severe weather impacts in
metropolitan Melbourne. No annual trend projections were possible due to the short time frame (approximately
5.2 years) and the significant variability over those years, likely influenced by one of the strongest La Nina events
on record.
The resolution of spatial data precluded detailed analysis with respect to RFA occurrences. The likelihood of
sustaining damage from severe weather events is influenced by a range of local, regional and property level
factors. Building age, size, construction materials and proximity to other buildings affect risk at property scale,
local factors include the size, density and age of trees, whilst regional factors such as geology, topography and the
temporal variability of risk influencers such as flood and bushfire also influence the potential and propensity for
property impacts.
21
Severe Weather in Victoria: Impacts and Response
It is acknowledged that the RFA database has issues of accuracy and reliability. Central Region estimated a ‘fudgefactor’ of up to15% due to units not reporting all jobs completed during large events. This study has also found
a lower number of instances where multiple RFAs were placed from the same address in the same general time
frame, suggesting that RFA call taking may inflate the number of RFAs received by VICSES. Notwithstanding,
no alternative statewide data was available and this study has generally broken new ground, developing new
information and intelligence to inform VICSES’ emergency planning and management activities.
This study is not intended to be a definitive or final study. In areas particularly prone to damage, it may be
appropriate for VICSES to work with local stakeholders such as Local Government Authorities to identify causative
factor and for the findings to inform community education, resilience activities and preventative measures.
Recommendations for further work are presented below:
1. It is acknowledged that the use of RFAs as a primary data source limits the scope of the study. Other sources,
such as insurance loss related data would provide a broader view, which may include parameters such as crop
damage or losses and allow a more normalised view of risk across the state. Data from other agencies (CFA,
MFB) should be examined for a more complete statewide view.
2. This study has utilised RFA data for days when over 50 severe weather RFAs were received. Given the relatively
small number of RFAs received in regional Victoria, this parameter may unduly prejudice the outcomes.
Parameter values more appropriate for regional Victoria should be reviewed to determine whether lower
thresholds alter the findings for regional areas.
3. The lack of attention to storm risk in Victoria from those State and Commonwealth Agencies with specific
hazard assessment capabilities suggests that VICSES needs to be more engaged with technical partners. In
particular, opportunities should be examined to partner with the Bushfire and Natural Hazards Cooperative
Research Centre to produce practical and implementable research outcomes.
4. The relationship between severe weather damage and other natural hazards should be examined; for example,
do reports of storm damage increase following floods or bushfires?
5. Review of RFAs indicates that a just over half of all severe weather RFAs are received during typical working
hours (8 am to 5 pm). The impacts of potential duplicates, repeat calls or RFAs placed to VICSES for work
outside the general scope of VICSES’ activities on volunteers day-to-day work requirements should also be
examined.
6. BoM and VICSES data suggest that the periods of greatest storm and thunderstorm activity, as reported in the
State Emergency Storm Plan do not align with the periods when VICSES receives the greatest number of severe
weather related RFAs. Further examination of why this may be is recommended.
7. Approximately a quarter of RFAs result in no action. Is the assessment or referral of these RFAs impacting on
volunteers’ capacity to deliver day-to-day work requirements?
8. During meetings with regional staff to discuss the outcomes of this study, there has been a clear desire
expressed for continuation of this study so that annual and regional trends can be further explored. This
could be an assessment of unit actions and the RFAs received, which could generally be undertaken in MS
Excel with data exported from the IRS. Summaries of LGA related data would require data to be mapped in a
GIS. The lack of a substantive technical / data analyst post in the VICSES’ Emergency Management Planning
Team limits ongoing capability and suggests that this should be resourced from State Operations and could be
incorporated into Emergency Response Activity Standards Project.
9. This study should not be a one-way flow of information. Where discussions are held between VICSES regional
staff and local stakeholders to determine why certain areas are more prone to severe weather damage. A
process should be developed where these findings are fed back to EMP and recorded so that future studies
can more accurately focus on influencing or confounding factors.
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Severe Weather in Victoria: Impacts and Response
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Severe Weather in Victoria: Impacts and Response
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Severe Weather in Victoria: Impacts and Response
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Severe Weather in Victoria: Impacts and Response
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Severe Weather in Victoria: Impacts and Response
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