Brisbane River
Strategic Floodplain
Management Plan
The Brisbane River Strategic Floodplain Management Plan project is a joint initiative of the Australian
Government, Queensland Government, Brisbane City Council, Ipswich City Council, Lockyer Valley
Regional Council, Somerset Regional Council and Seqwater.
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Floodplain Management Plan, as long as you
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Attribution
The Brisbane River Strategic Floodplain
Management Plan is a joint initiative of
the Australian Government, Queensland
Government, Brisbane City Council, Ipswich
City Council, Lockyer Valley Regional Council,
Somerset Regional Council and Seqwater.
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0289
The Brisbane River Strategic Floodplain
Management Plan (Strategic Plan) is a non-
statutory guide for delivering a coordinated
approach to managing flood risk across the
Brisbane River floodplain, now and into the
future. It sets out a range of strategies and actions
for state and local governments to consider in
order to strengthen the flood resilience of the
region. The strategies and actions can be applied
to a range of floodplain management measures
that include but are not limited to land use
planning, disaster management, building controls
and structural mitigation options.
This Strategic Plan is a resource for state and
local governments to enable the coordinated
implementation of flood resilience actions
over time. Its purpose is to facilitate regionally
consistent flood risk management outcomes for
the region, with flexibility in local implementation
approaches and processes. It does not alter the
statutory effect of existing legislation and policy.
The Strategic Plan provides the basis from which
local governments will further their understanding
of flood risks and impacts at the local level
through the development of Local Floodplain
Management Plans.
1
Our Shared Vision
residents, businesses, community
groups and governments working
together to better manage flood
risk and strengthen the resilience
of our communities, our economy,
our infrastructure and
our environment
2
Brisbane River Strategic Floodplain Management Plan
Foreword
The Brisbane River Strategic Floodplain Management Plan provides
the blueprint for how we will better prepare for and manage flood
risk across the Brisbane River floodplain.
This plan has been developed in proud partnership between the
Queensland Government, the four local governments of Brisbane,
Ipswich, Somerset and Lockyer Valley, and Seqwater.
It builds on 2017’s Brisbane River Catchment Flood Study, which
was the largest study of its kind to be undertaken in Australia, and
I commend all the stakeholders who have contributed.
Floodwaters hold no regard for local government boundaries,
which is why it’s so important we take a whole-of-catchment,
regional approach to identify more efficient ways to strengthen our
flood resilience.
The Queensland Government is committed to keeping communities
safe, and this strategic plan will play a major part in that for the
Brisbane River floodplain area.
This work contributes to the Queensland Strategy for Disaster
Resilience and Resilient Queensland 2018-2021 – Delivering
the Queensland Strategy for Disaster Resilience vision of making
Queensland the most disaster resilient state in Australia.
Professionals seeking guidance from this strategic plan are
encouraged to join us in our efforts to ensure we build flood
resilience in ways that support this regional plan.
Cameron Dick MP
Minister for State Development, Manufacturing,
Infrastructure and Planning
3
Introductory statements
Brisbane’s subtropical
climate makes our city
a great place to live,
work and relax.
Defined by its river,
it’s important that
Brisbane is a resilient
New World City that
can plan for, respond to and recover from floods.
Brisbane City Council is committed to building
a more liveable, resilient city – a city that is
safe, confident and ready to respond to natural
disasters.
The WaterSmart City priority actions in Council’s
Brisbane. Clean, Green, Sustainable 2017-
2031 is our long-term approach to managing
and reducing the risks of flooding for Brisbane
residents, businesses and infrastructure.
The challenge of managing floods also needs a
whole-of-catchment approach that transcends
local government boundaries. The Brisbane River
Strategic Floodplain Management Plan embodies
this approach, outlining actions that support
resilience across the Brisbane River catchment.
In combination with the Council of Mayor’s
Resilient Rivers Initiative, this work provides
a coordinated approach that helps us work
together to improve community safety and reduce
the impacts of flooding.
While we cannot prevent flooding altogether, we
now have the best possible information
and framework to ensure our community is
prepared, adaptable and can recover more
quickly after a flood.
Adrian Schrinner
Lord Mayor
Brisbane City Council
Ipswich City and its
region is no stranger to
river flooding having
experienced significant
events in 1893, 1974 and
2011.
The flood of 2011 was a
stark reminder that we
live, work and play in the
Brisbane and Bremer River floodplains, and given the
right climatic conditions, flooding can and will occur
again.
Despite these events we witnessed incredible
examples of community resilience, determination and
mateship in the aftermath.
Flooding in the Brisbane and Bremer River catchment
is not just an issue that affects Ipswich. It is a regional
issue determined by a single large catchment that
also affects the council areas of Somerset, Lockyer
Valley and Brisbane.
The Strategic Floodplain Management Plan is the
outcome of the Brisbane River Catchment Flood
Studies in response to the Queensland Floods
Commission Inquiry.
The catchment studies encompass an extensive
body of work which required a strong collaborative
partnership across state and local governments, and
many other entities involved in the Brisbane and
Bremer River floodplains.
The plan provides a framework for the four local
governments (and other entities) to strategically
assess and develop regionally consistent approaches
to improving community resilience to the impact of
future floods.
Ipswich City Council will refer to the Brisbane River
Strategic Floodplain Management Plan when
formulating a Local Flood Management Plan for the
Bremer River.
Major floods will happen again.
By adopting a coordinated regional approach it will
be possible to better manage flood risks in the future.
David Farmer
Chief Executive Officer
Ipswich City Council
4
Brisbane River Strategic Floodplain Management Plan
Living with flooding
is a part of life in
the Brisbane River
catchment. We live in
a sub-tropical climate
so from time to time
we will experience
flooding and as a
community we need to
be informed, ready and resilient.
The floods experienced across Queensland in
2010/11 was the catalyst for change in how we
understand our flood risk and plan for the future.
Flood waters cross local boundaries and taking
a whole-of-catchment approach allows us to
understand the bigger picture and better manage
flood risk together.
Local governments will now use the Brisbane
River Strategic Floodplain Management Plan
to inform local floodplain management plans
to apply regionally consistent approaches to
increase flood resilience in their communities.
Cr Graeme Lehmann
Mayor
Somerset Regional Council
Following the historic
floods of 2011, it
was vital for Lockyer
Valley Regional
Council to take action
and ensure we were
doing everything
possible to protect
our community.
While it’s impossible to avoid flooding events
altogether, the Brisbane River Catchment Flood
Study is a key part of the puzzle in providing the
information we need to strengthen the resilience
of our growing community.
Using the data from the Study, the Brisbane
River Strategic Floodplain Management Plan will
be instrumental in undertaking local flood risk
assessments for residential properties as well as
new infrastructure projects.
It has been a challenging, but rewarding journey
since 2011 and a pleasure to partner with State
Government and other key organisations on
projects such as this and the Resilient Rivers
Initiative to protect the future of the Lockyer Valley.
Cr Tanya Milligan
Mayor
Lockyer Valley Regional Council
5
6
Brisbane River Strategic Floodplain Management Plan
CONTENTS
Introduction 8
Understanding our flood risk 19
Desired outcomes of this Strategic Plan 35
Actions supporting improved flood risk
management in the Brisbane River
floodplain 54
Implementation and monitoring
arrangements 64
Appendix A – Glossary of terms 65
Appendix B – Acronyms and abbreviations 69
Appendix C – Potential Hydraulic Risk Matrix 70
Appendix D – Reference list 72
7
Introduction
The Brisbane River floodplain is the most flood impacted area
in Australia. Some 1.2 million
†
people live within the Brisbane
River catchment. The Brisbane River floodplain has a population
of more than 280,000 people and almost $300 million in
annualised damages. As our population grows, this will increase.
Increasing our flood resilience is necessary to improve community
safety and reduce the costs of floods.
The floods experienced across Queensland in
2010-11 demonstrated the impact flooding can
have on our community. The events reinforced
that floods do not respect local government
boundaries and regional-scale and multi-
disciplinary approaches are necessary to better
coordinate efforts to identify and respond to
flood risk.
The Brisbane River Catchment Flood Studies
(Flood Studies) responds to recommendations
from the Queensland Floods Commission
of Inquiry (QFCoI), including undertaking a
comprehensive flood study of the Brisbane River
Catchment and other (floodplain management)
matters relating to land use planning, building
controls and emergency management that assist
us in managing the flood risk of the Brisbane
River floodplain.
The Flood Studies are a partnership between
the Queensland Government, Seqwater and the
four local governments of Brisbane City Council,
Ipswich City Council, Somerset Regional Council
and Lockyer Valley Regional Council. The Flood
Studies are a major program of work, which
encompasses a new approach to integrated
management of the Brisbane River floodplain.
They represent a firm commitment between the
Queensland Government and local governments
to deliver on a long-term plan that will further
manage the impact of future floods and enhance
community safety and resilience in the Brisbane
River floodplain. The Flood Studies comprises
four phases and are illustrated in Figure 1 and
listed below:
Phase 1 Data Collection (2013)
Phase 2 Brisbane River Catchment Flood Study
(2017)
Phase 3 Brisbane River Strategic Floodplain
Management Plan and Technical
Evidence Report (2018)
Phase 4 Local Floodplain Management Plans
(2018-19).
†
Geoscience Australia 2016.
8
Brisbane River Strategic Floodplain Management Plan
Figure 1 – Phases of the Brisbane River Catchment Flood Studies
Data
Collection
COMPLETE
Brisbane
River
Catchment
Flood Study
COMPLETE
Strategic
Floodplain
Management
Plan
+
Technical
Evidence
Report
COMPLETE
Local
Floodplain
Management
Plans
Phase 1
2013
Phase 2
2017
Phase 3
2018
Phase 4
Commencing 2018–19
9
The peer reviewed Brisbane River Catchment
Flood Study (Flood Study) took four years to
complete using industry leading modelling
techniques. The Flood Study modelling provides
a better understanding of flood behaviour based
on a range of scenarios looking at the location of
rainfall, ground conditions, sea levels and dam
water levels. While we can’t prevent flooding
from occurring, a greater understanding of
catchment behaviour can help us improve how
we prepare and respond to the various flood
events that may come our way.
This Brisbane River Strategic Floodplain
Management Plan (Strategic Plan) has been
informed by more than 18 months of work by a
range of key stakeholders. It outlines our shared
understanding of current and future flood risk in
the Brisbane River floodplain. It also identifies
the desired outcomes and strategies for the
ongoing management of the floodplain and
contributing catchment, and identifies a suite
of actions that the Queensland Government,
Seqwater and the four local governments will
work towards to improve community safety and
reduce the costs of floods.
This Strategic Plan focuses on flooding from
the Brisbane and Bremer Rivers (referred to as
riverine flooding), and is the first time flood risk
has been explored on a regional scale across
the Brisbane River floodplain. This Strategic Plan
provides guidance to a range of professions
across all levels of government for more detailed
consideration and implementation of consistent
regional scale strategies to flood risk over time.
The Brisbane River floodplain is located
within a dynamic region encompassing
multiple community, environmental and
economic interests. A holistic, integrated and
collaborative approach, which engages these
interests in decision making and action, will
ensure floodplain management is effective
and sustainable. An integrated planning
approach involves:
• collaboration with the community and all
levels of government
• capturing the connections between key
strategic planning processes and building
on the extensive work already undertaken
• acknowledging that a range of interests
need to be considered in floodplain
management
• recognising that floodplain management
strategies and actions can offer multiple
benefits in addition to flood risk reduction
• identifying how floodplain management
strategies and actions may impact the
delivery of other strategic plans.
The Brisbane River Strategic Floodplain
Management Plan Technical Evidence Report
(Technical Evidence Report) assessed the
consequences which may occur for the full range
of flood events, now and in the future, and how
they can be managed. The Technical Evidence
Report considered potential regional-scale flood
management measures including structural
options, land use planning, building controls,
landscape management, disaster management
and community resilience. This analysis provided
the evidence base for making decisions about
ways we can collectively manage current and
future risks, informed by integrated and whole-of-
floodplain considerations.
This Strategic Plan builds on the extensive work
already undertaken since 2011 by the four local
governments, Seqwater and the Queensland
Government to better manage flood risk in the
catchment. This work will continue to develop
through the implementation of this Strategic Plan
and the development and implementation of
subsequent Local Floodplain Management Plans.
Implementation of the floodplain management
strategies and actions outlined in Section 4,
will work towards achieving these outcomes,
supported by governance arrangements as
detailed in Section 5 of this Strategic Plan.
Local Floodplain Management Plans will be
delivered as the fourth and final phase of
the Flood Studies program of work. The Local
Floodplain Management Plans will build on
the Strategic Plan to establish more detailed
floodplain management approaches within each
of the local government areas.
10
Brisbane River Strategic Floodplain Management Plan
This Strategic Plan provides guidance for a
range of professionals involved in building
flood resilience in the Brisbane River
floodplain.
Supporting information contained in the
Appendices includes a glossary of terms, list
of acronyms and a reference list to assist in
interpreting and applying this Strategic Plan.
11
Our shared vision for the Brisbane River floodplain
Residents, businesses, community groups and governments working together to better manage
flood risk and strengthen the resilience of our communities, our economy, our infrastructure and
our environment.
1.1 Working together to
achieve our shared vision
Effective floodplain management requires an
integrated and whole-of-catchment approach.
Floods do not respect local government
boundaries and there may be cause and effect
impacts experienced in different parts of the
catchment. Figure 2 illustrates the coordinated
approach across a range of disciplines for
delivering flood resilience.
This Strategic Plan has been developed
as a partnership between the Queensland
Government, Seqwater and the four local
governments located within the Brisbane River
floodplain. Collaboration and engagement within
each of these organisations has been critical to
the successful development of this Strategic Plan
and has involved a range of professions including
engineering, planning, community development,
disaster management, transport, environment
and communications.
A coordinated approach to each (flood
resilience) measure shown in Figure 2 helps to
reduce the impact of flooding in different ways
and enhance the flood resilience of communities
in the catchment. Measures such as land use
planning and structural options focus on the
reduction of exposure to flooding whereas
community awareness and resilience are aimed
at improving how we prepare for, respond to,
and recover from floods.
Figure 2 – An integrated approach to managing the Brisbane River floodplain
12
Brisbane River Strategic Floodplain Management Plan
This multi-disciplinary approach has informed
the development of nine desired outcomes for
flood risk management. When implemented
these outcomes will support the delivery of our
shared vision and guide the regionally consistent
and integrated response required for robust
floodplain management of the Brisbane River
floodplain. The nine desired outcomes are:
1. floodplain management initiatives are delivered
using a holistic, integrated and collaborative
approach
2. floodplain management initiatives are
informed by a regional understanding of
current flood risks
3. future climate change impacts are recognised
and planned for through adaptation and
resilience building
4. community awareness, understanding and
response is the foundation for community
resilience
5. land use is planned, located and considers
design elements to ensure development
appropriately responds to the level of
flood risk
6. building design and construction improves
community resilience and reduces property
damages
7. infrastructure is used to reduce flood risks
where appropriate
8. landscape management is planned across
the catchment in a way that contributes to
flood risk reduction
9. disaster management planning and response
applies a regionally consistent approach
whilst recognising local flood risks.
13
1.2 About the study area
The Brisbane River Catchment spans
approximately 13,570 square kilometres
and is home to the largest river in South East
Queensland. Approximately half of the catchment
drains into the Wivenhoe and Somerset Dams,
providing the primary source of water supply for
communities located in the region.
The focus for the Flood Studies is on flooding
in the Brisbane River floodplain downstream of
Wivenhoe Dam to Moreton Bay, as well as the
lower reaches of the major tributaries of Lockyer
Creek, Oxley Creek and the Bremer River. However,
flooding from local creeks and tributaries within
the study area are not addressed.
Wivenhoe
Dam
Lockyer
Creek
Bremer
RIver
Somerset Dam
Brisbane River Catchment
Brisbane River Floodplain
Figure 3 – Brisbane River catchment and floodplain
The Flood Study investigated regional-scale
flooding on the Brisbane River floodplain that
would be caused by substantial rainfall across
the Brisbane River Catchment. The Brisbane River
floodplain extends into parts of the four local
governments of Brisbane, Ipswich, Somerset
and the Lockyer Valley (refer Figure 3). The Flood
Studies also included a five kilometre buffer area
around the floodplain to consider any indirect
implications of flooding from the Brisbane River.
14
Brisbane River Strategic Floodplain Management Plan
1.3 Key influences on the
development of this Strategic Plan
Queensland Floods Commission of
Inquiry recommendations
In January 2011, Queensland experienced
widespread flooding that caused extensive damage
to both public and private property, the evacuation
of towns and the loss of more than 30 lives.
The Queensland Floods Commission of Inquiry
(QFCoI) Final Report was released in March 2012
and recommended a comprehensive flood study
of the Brisbane River Catchment be completed
to identify the probability and extent of various
floods occurring. Key recommendations included:
• Recommendation 2.2 – ‘as soon as
practicable, a flood study of the Brisbane
River catchment should be completed.’
• Recommendation 2.12 – ‘councils in
floodplain areas should, resources
allowing, develop comprehensive
floodplain management plans that accord
as closely as practicable with best practice
principles.’
In addition, a range of other recommendations
were made relating to land use planning,
development regulation, building controls,
emergency management, community awareness
and other matters relevant to managing the
Brisbane River floodplain.
The 2011 floods and outcomes of the QFCoI
represent a benchmark against which future
major flood events in the Brisbane River
catchment will be compared.
Queensland Audit Office review of
flood resilience since the 2011 floods
In 2016, the Queensland Audit Office (QAO)
undertook a review of the effectiveness of
flood resilience activities since the 2011
floods, focusing specifically on the four local
governments covering the Bremer, Lockyer, Mid
and Upper Brisbane River Catchment; namely
Ipswich, Somerset, Lockyer Valley and Scenic
Rim. The findings concluded that a coordinated
strategic approach that manages risk at a
whole-of-catchment scale is required. It also
recognised that the absence of such an approach
is a missed opportunity to undertake integrated
catchment management, incorporating flood
risk mitigation with other elements of catchment
management such as water quality, biodiversity
and recreational activities.
A key recommendation of QAO (2016) was that
the Queensland Government coordinate flood
resilience activities and funding on a catchment
scale in collaboration with local governments
and other relevant entities, to effectively identify,
assess, prioritise and manage catchment scale
flood risks.
Local government
Each local government within the floodplain is
continuously refining responses to flood risks
as resources permit, through the integration of
best practice floodplain management principles
in their community engagement, disaster
management, land use planning and other
floodplain management activities. Collaboration
at a whole-of-catchment level and guidance for
the preparation of Local Floodplain Management
Plans for the Brisbane River catchment will
enhance the effectiveness, integration and
consistency of these local scale initiatives.
Queensland State Planning Policy
- adoption of a risk-based planning
approach
The QFCoI recommendations relating to land use
planning have been incorporated into a range
of state planning instruments including the
Queensland Planning Act 2016 and the State
Planning Policy July 2017.
The Natural Hazards, Risk and Resilience policies
and guidance material was updated as part
of the State Planning Policy July 2017 review.
This update incorporates a risk-based land use
planning approach as recommended by the
QFCoI. This approach has been further supported
by the 2015 Productivity Commission Report
into Natural Disaster Funding (Volume 1) and
is recognised as best practice by the Planning
Institute of Australia in supporting community
resilience to natural hazards as outlined in
the National Land Use Planning Guidelines for
Disaster Resilient Communities (2016).
15
SEQ Regional Plan – aspirations for
flood resilience
The ShapingSEQ – South East Queensland
Regional Plan 2017 (ShapingSEQ) identifies this
Strategic Plan as an action for natural hazard
management (flood risk) within the Brisbane
River Catchment, for the purpose of ensuring
‘the resilience of SEQ communities to flooding
through a coordinated approach to management
of risk to acceptable levels’.
Queensland Disaster Resilience Policy
The Queensland Strategy for Disaster Resilience
was updated in 2017 to incorporate climate
change risk and deliver a comprehensive ‘all
hazards’ approach to building disaster resilience
throughout Queensland. Further to this, the
Queensland Strategic Policy Framework for
Riverine Flood Risk Management and Community
Resilience was developed in 2017, which also
informs this Strategic Plan.
Queensland State Natural Hazard
Risk Assessment 2017
The Queensland Disaster Management
Committee endorsed the Queensland
State Natural Hazard Risk Assessment (Risk
Assessment) on 28 August 2017 as an ‘all
hazards’ assessment of natural hazard
risks to the state of Queensland. The Risk
Assessment identifies that “riverine flooding
is of equal highest priority (natural hazard risk)
for Queensland. However a range of climate
influences, as indicated within this report, may
give rise to riverine flooding, thereby making it
a more frequently manifesting hazard.”
The approach to flood risk management
underpinning this Strategic Plan aligns with the
risk management approach of the Queensland
State Natural Hazard Risk Assessment 2017 and
the Queensland Emergency Risk Management
Framework.
Queensland Climate Adaptation
Strategy 2017
The Queensland Climate Adaptation Strategy
2017 (Q-CAS) provides a framework for the
Queensland Government to lead action on
adaptation to climate change. The Q-CAS
acknowledges the risks associated with a
changing climate and is an important point of
reference in understanding and responding to
climate change related impacts on future flood
risks within the Brisbane River floodplain.
1.4 An integrated catchment
planning approach
An integrated catchment planning approach will
ensure appropriate linkages are made with other
planning processes to deliver multiple benefits
for the region and avoid unintended outcomes.
Figure 4 provides a visual representation of this
approach and shows how the common elements
between the planning processes occurring in the
catchment are considered. Refer to Section 3.1
of the Technical Evidence Report for further detail
about this collaborative approach.
The success of integrated catchment planning is
influenced by several key elements as discussed
in QAO report, including:
• recognising and balancing the
relationships between cause and
effect impacting on people, property,
infrastructure and ecosystems within a
catchment
• a coordinated approach from all levels of
government
• community and private enterprise
engagement.
16
Brisbane River Strategic Floodplain Management Plan
Figure 4 – Integrated Catchment Planning components
Dam operations and upgrades
Critical infrastructure network
Meeting current
and future demands
Water sensitive urban design
Re-engaging floodplain
Flood
management
Water
supply
Secure, sustainable
and safe water
for all users
Improving
public safety and
reducing costs
of flooding
Balancing the needs of
multiple landusers and
the environment
Common elements
Water quality
Ecosystem health
Catchment condition
Making space for rivers
Allocating land uses across
floodplain
Hazard-appropriate built form
Efficient water
allocation and use
Sustainable,
connected liveable
communities now and
into the future
Land use
planning
Landscape
Management
Integrated Catchment Planning
Balancing social, environmental and economic considerations
17
Strategic planning processes for the Brisbane
River Catchment include:
• Land use planning – the Queensland
Government’s ShapingSEQ sets out a
regional framework for sustainable growth,
global economic competitiveness, world-
class infrastructure, ecological and social
sustainability and high quality living.
ShapingSEQ was developed through
extensive community engagement and
collaboration between all levels of
government. It considers the need to
protect our natural environment and
lifestyle in addition to managing future
growth. Local governments are required
to reflect the relevant outcomes of
ShapingSEQ through their local planning
instruments.
• Floodplain management – the focus of the
Flood Studies is to deliver complementary
regional and local structural and non-
structural measures that improve public
safety and reduce flood damages across
the Brisbane River Catchment.
• Water supply – Seqwater is responsible
for providing ‘a safe, secure and reliable
water supply’ to South East Queensland.
Seqwater has adopted a whole-of-
catchment approach to water quality
and recognises that water treatment
begins at the source. In addition to being
South East Queensland’s primary bulk
water provider, Seqwater offers public
recreation facilities as well as essential
flood mitigation services through the
operation of Wivenhoe and Somerset dams
for flood storage. Of particular relevance
to this Strategic Plan is the planning work
underway for upgrades to the Somerset
and Wivenhoe dams.
• Landscape management – the South East
Queensland Resilient Rivers Initiative
aims to improve the resilience and health
of the region’s waterways through the
development of Catchment Action Plans
for key catchments throughout South
East Queensland. Catchment Action Plans
aim to enhance investment collaboration
across local government boundaries by
a number of investors. Catchment Action
Plans have been completed for the Lockyer,
Mid Brisbane, Lower Brisbane/Redlands
and Bremer catchments. Local Floodplain
Management Plans will be incorporated
into revisions of the Catchment Action
Plans as appropriate.
‘reflect the local context and integrate
with other planning processes’
Sayers et. al 2014: 10 Golden
Rules for managing floods
18
Brisbane River Strategic Floodplain Management Plan
Understanding our flood risk
2.1 Landscape characteristics
that influence flood behaviour
The Brisbane River valley was carved out of
bedrock over millions of years as waters drained
from the catchment into Moreton Bay. This
river valley is relatively narrow with steep sides
in some places, and has a generally flat base
that has been infilled by sediment washing off
the catchment over millennia. The Brisbane
River Catchment is capable of generating large
volumes of floodwaters depending on the
magnitude and extent of a major rainfall event
and the condition of the catchment (e.g. soil
moisture). Just 1 millimetre of run-off across the
whole catchment is sufficient to fill over 5000
Olympic-size swimming pools.
Most floodplains contain three functional areas
as follows:
• Flood conveyance is where the vast
majority of water flows and where flood
waters are typically deep and fast flowing
during big floods
• Flood storage areas are parts of the
floodplain that fill up with floodwaters,
and are then temporarily detained during
a flood. (Flood waters in these areas are
typically deep and slow moving)
• Flood fringe represents the remainder of
the floodplain, which features generally
shallower flooding.
The function of the floodplain varies between
different flood events, i.e. flood fringe areas in
smaller floods may become flood storage areas
in larger, rare events.
Downstream of Wivenhoe Dam, the Brisbane
River valley is very incised – meaning the
riverbed is bounded by a steep floodplain, with
several points of restriction. When flooding
occurs, water quickly fills the lowest-lying parts
of the floodplain. During larger floods, the spread
of water is constrained by the narrow width and
steep edges of the floodplain. This means that as
floods get bigger, the waters rise upwards rather
than dispersing sideways. In comparison, areas
upstream of Amberley in the Bremer Catchment
and within the Lockyer Creek Catchment have
more extensive and broad floodplains that
capture and temporarily store floodwaters during
significant flood events.
Given it has mostly steep valley sides, there
are very few areas within the Brisbane River
floodplain that can be considered flood fringe
(refer Figure 5). This means that for most of the
floodplain, floodwaters in the Brisbane River can
potentially be quite deep, while areas closer to
the river can also flow relatively fast during big
floods. This unique topography also means the
floodplain is sensitive to changes in landform as
most of the floodplain has an important natural
function during a flood.
19
The Technical Evidence Report introduces the
concept of Potential Hydraulic Risk (HR), which
has been defined based on the hydraulic
behavior of floods and their likelihood of
occurring. This concept was the first step in
identifying flood risk however it does not define
the overall flood risk. Flood risk considers a
range of factors in addition to potential hydraulic
risk and is best suited to be determined at the
local level to reflect local context. The HR is
determined by grouping similar hydraulic risks
into five bands, with HR1 being the highest risk
and HR5 the lowest (refer to Appendix C of this
Strategic Plan, and Section 4.2 of the Technical
Evidence Report). The HR categories broadly
correlate to, and help visualise, the level of risk
associated with flood conveyance, flood storage
and flood fringe areas. This information can be
used, along with other factors, to inform risk
assessments.
Flood conveyance areas, within the Brisbane
River floodplain shown in Figure 3, generally
align with those defined as HR1 and HR2. These
are the most potentially hazardous parts of the
floodplain and are critical for transporting floods
downstream. Flood storage areas generally align
with those defined as HR3 and HR4. Changes in
the topography of these flood storage areas can
cause increased flood levels elsewhere in the
catchment. A detailed discussion and mapping
of HR areas is provided in the Section 4.2 of the
Technical Evidence Report.
Figure 5 – Example river cross section showing the physical characteristics of the Brisbane River
floodplain
2.2 Terminology describing
floods
Floods are described in terms of the probability
of their occurrence as expressed by the term Annual
Exceedance Probability (AEP). AEP refers to the
probability of a flood of the nominated size or larger
occurring in any given year. For example, a 1% AEP
flood describes an event that has a 1 in 100 chance
of being equalled or exceeded in any given year.
The 1% (1 in 100) AEP is commonly used to
identify areas at risk from large-scale flooding.
However, it is important to understand the risks
and potential consequences of the full range of
floods, from the small and frequent to the very
large and rare.
The Flood Study provided estimates for 11 different
likelihoods of flood events, ranging from a frequent
50% (1 in 2) AEP, to extremely unlikely with a
0.001% (1 in 100,000) AEP. The 0.001% (1 in
100,000) AEP flood inundation extent is considered
the notional extreme event and in the context of
the Flood Studies has been used to define the full
extent of the Brisbane River floodplain.
Table 1 compares the likelihood of a range of
floods occurring in an 80-year lifetime and their
corresponding flood levels at Brisbane City and
Ipswich gauges.
20
Brisbane River Strategic Floodplain Management Plan
Table 1 – Likelihood for a range of flood AEPs occurring in an 80-year lifetime in the Brisbane River
floodplain derived from the Flood Study
AEP At least once in
80 years
At least twice in
80 years
Brisbane City
gauge
(m, AHD)
Ipswich CBD
(m, AHD)
10% (1 in 10) 100% 100% 1.8 14.8
5% (1 in 20) 98% 91% 2.2 16.1
2% (1 in 50) 80% 48% 3.2 18.7
1% (1 in 100) 55% 19% 4.5 20.1
0.2% (1 in 500) 15% 1% 7.3 23.4
0.05% (1 in 2000) 4% 0.1% 9.9 25.7
0.001% (1 in 100,000) 0.1% < 0.1% 23.7 36.1
2.3 History of flooding in the
Brisbane River floodplain
Brisbane River flooding has occurred for
millennia. Since formal records began 170 years
ago, there have been a number of significant
floods including in 1841, 1844, 1893 (two
events), 1974 and 2011. Figure 6 highlights the
peak flood levels for the 1% (1 in 100) AEP and
the 0.2% (1 in 500) AEP floods at key locations
compared to major recorded floods. Modelling
carried out for the Flood Study shows the 1%
(1 in 100) AEP flood event is higher than the
2011 and 1974 floods in some areas, while in
other parts of the floodplain it is lower. A number
of factors contribute to floods inlcuding rainfall
variability, ground conditions, tidal conditions
and dam operations. These factors vary between
flood events, meaning that no two floods are the
same, and similar or larger sized floods could
occur in the future.
Over an 80 year period, there is a 55
per cent chance that a 1% (1 in 100)
AEP event will occur at least once.
21
Figure 6 – Historical flooding in the Brisbane River floodplain
Flood behaviour varies across the floodplain as a
result of different combinations of rainfall across
the catchment (amounts, timing and location),
ground and tidal conditions, and dam operations.
The level of flooding experienced in parts of
the floodplain is particularly influenced by the
location of rainfall, which can occur in the Bremer,
Lockyer or Upper Brisbane sub-catchment areas,
or a combination of any or all of these. History also
shows that the occurrence of major floods does
not prevent other major or moderate floods from
occurring in short succession.
Brisbane
River
Brisbane
River
Wivenhoe
Dam
Oxley
Creek
Lockyer
Creek
Bremer
River
Warrill
Creek
Purga
Creek
BRISBANE
LOCKYER
VALLEY
IPSWICH
SOMERSET
GATTON RAIL BRIDGE
0.2% AEP
1% AEP
1893 fl ood
1974 fl ood
2011 fl ood
DAVID TRUMPY BRIDGE
2011 fl ood
1974 fl ood
1% AEP
0.2% AEP
SOUTH BANK
0.2% AEP
2011 fl ood
1974 fl ood
1% AEP
0.2% AEP
2011 fl ood
1974 fl ood
1% AEP
1893 fl ood
GOODNA
BRISBANE RIVER FLOODPLAIN
Localised flooding in creeks and tributaries are
the result of high rainfall occurring in an isolated
area of a creek catchment over a short period of
time. In contrast, the majority of regional floods
in the lower Brisbane River have almost always
been the result of ex-tropical cyclones that
delivered persistent rainfall to the region over a
number of days. This Strategic Plan focuses on
regional riverine floods and associated risks.
Localised flooding and overland flow issues are
investigated and managed separately by local
governments.
22
Brisbane River Strategic Floodplain Management Plan
Figure 7 shows the AEPs of the peak flood levels
experienced throughout the Brisbane River
floodplain during the 2011 floods.
Flood levels in the Brisbane CBD were estimated
to be a 1% (1 in 100) AEP, while flood levels in
other areas such as Lowood reached a 0.7% (1
in 140) AEP and for Ipswich a 1.3% (1 in 80) AEP.
Although significant, it was not the largest flood
experienced in the floodplain.
2.4 How flood risk is
determined
Risk occurs when a community is potentially
affected by a hazard, such as flooding. In
accordance with leading practice risk standards,
including the Queensland Emergency Risk
Management Framework (QFES, 2017), risk is
defined as the combination of the likelihood of
the hazard occurring and the consequence once
the hazard occurs. Likelihoods can range from
very frequent to very rare, while consequences
can range from insignificant to catastrophic.
Understanding both the likelihood and
consequence of a range of possible floods
will inform decisions for appropriate flood
risk management including assessment and
selection of flood risk management measures.
Risk reduction can be achieved by lowering the
chance of the hazard occurring or reducing the
potential consequences when it does occur.
In the context of flooding, the likelihood
of a flood hazard occurring is relatively
straightforward to determine (e.g. a 1%
(1 in 100) AEP). The consequence of flooding is
more complex and dependent on a number of
factors including:
• hydraulic behaviour – where the flood
waters will go (such as depths and
velocities)
• exposure – land uses, buildings and
population in the path of the flood
• vulnerability – susceptibility or sensitivity
of land uses and populations to flooding
• tolerability – the degree to which a level of
flooding is considered acceptable for the
land uses and populations in the path of
the flood.
Lowood
0.7% AEP
(1 in 140)
JindaLee
1% AEP
(1 in 100)
MoggiLL
0.9% AEP
(1 in 110)
LoaMside
20% AEP
(1 in 5)
waLLoon
2% AEP
(1 in 50)
ipswich
1.3% AEP
(1 in 80)
Mt crosby
0.8% AEP
(1 in 120)
savages
c
rossing
0.77% AEP
(1 in 130)
one MiLe
b
ridge
3.3% AEP
(1 in 30)
brisbane
c
ity
1% AEP
(1 in 100)
Figure 7 – Flood AEPs experienced during the 2011 floods
Risk = Likelihood x Consequence
23
Socio-economic drivers often dictate that the
more vulnerable members of our community have
a higher degree of exposure to hazards as these
may be the only convenient and affordable areas
to live. Within the Brisbane River floodplain,
an estimated 2000
1
people live in the highest
potential hydraulic risk category (HR1), of which
three-quarters (1700 people) are considered
to be highly vulnerable. However, across the
remainder of the floodplain (HR2 – HR5) less
than half of the population is considered highly
vulnerable (130,000 of the estimated 280,000
people). Refer to Figure 8 and Section 4.5 of the
Technical Evidence Report for further detail.
Figure 8 - Vulnerable population within
hydraulic risk categories
Risk-based approach
Consideration of the full range of flood risks
has become embedded in best practice, as
described in key flood management guidelines
for Australia (Ball et al., 2016, AIDR, 2017). The
SPP also requires floodplain management to
adopt a risk-based approach and Queensland Fire
and Emergency Services (QFES) has incorporated
this approach in its State Natural Hazards Risk
Assessment 2017 and the Queensland Emergency
Risk Management Framework 2017. This means
that rather than considering hazards for a single
likelihood such as a 1% (1 in 100) AEP, the total
risk covering a suite of flood likelihoods and
resulting hazards is to be considered, ranging from
small and frequent events up to the most extreme
and unlikely event.
A risk-based approach also requires judgement on
what is considered to be an acceptable, tolerable
or intolerable risk. The SPP Natural Hazards, Risk
and Resilience (Flood) Guidance Material (DSDMIP,
2017) defines these as follows:
Acceptable risk is a risk that, following
an understanding of the likelihood and
consequence, is sufficiently low to require no
new treatments or actions to reduce risk further.
Individuals and society can live with this risk
without feeling the necessity to reduce the risk
any further.
Tolerable risk is a risk that, following
an understanding of the likelihood and
consequence, is low enough to allow the
exposure to continue, and at the same time high
enough to require new treatments or actions to
reduce risk. Society can live with this risk but
believes that, as much as reasonably practical,
steps should be undertaken to reduce the risk
further.
Intolerable risk is a risk that, following
an understanding of the likelihood and
consequence, is so high that it requires actions
to avoid or reduce the risk. Individuals and
society will not accept this risk and measures
are put in place to reduce the risk to at least a
tolerable level.
HR1
76%
Vulnerable
Population
HR2-5
50%
Vulnerable
Population
1
Population numbers are indicative only based on building footprint counts (which in some areas does not identify multi-storey or
multi-unit dwellings) and census averages.
24
Brisbane River Strategic Floodplain Management Plan
Tolerability of flooding will vary along the risk
spectrum from individual to individual, land
use to land use, and community to community.
Tolerability is largely driven by a community’s
awareness of flooding and resilience to impact.
Tolerability may also change over time as a
community changes. Tolerability cannot be
assessed at a regional scale and should be
determined at the local scale to establish
levels of flood acceptance. The Local Floodplain
Management Plans to be developed as part
of the Flood Studies will establish acceptable,
tolerable and intolerable risk on a local
government scale.
Risk treatment involves an array of approaches
including:
• avoidance – keeping inappropriate land
use and development away from certain
areas to minimise risk to life
• accommodation – using controls and
measures to increase flood resilience and
minimise damage to property
• protection – changing flood behaviour
through structural measures such as dams,
levees and floodgates
• awareness – ensuring the community
understands their risk and can respond
accordingly to maintain community safety.
2.5 Current flood risk and
impacts
Urban development has been extensive
throughout the Brisbane River floodplain over
the past century (refer Figure 3). As of 2017, an
estimated 134,000
2
buildings were located in the
Brisbane River floodplain. Approximately 75 per
cent of these buildings were located in Brisbane,
22 per cent in Ipswich, 3 per cent in Somerset
and 0.5 per cent in the Lockyer Valley (refer
Chapter 6 of the Technical Evidence Report).
Existing development in the Brisbane River
valley is the result of evolution from the original
colonial settlements and infrastructure, as well
as taking advantage of the continuing social and
amenity values provided by living near water.
For a 10% (1 in 10) AEP flood, 51 buildings would
flood above floor level in Brisbane, 74 buildings
in Ipswich, 10 buildings in the Lockyer Valley and
15 buildings in Somerset.
For a 1% (1 in 100) AEP flood, about 17,300
buildings across the floodplain would experience
flooding, two thirds of these are located in the
Brisbane City Council area. Of these properties,
about 12,000 are expected to be flooded above
the main habitable floor level (refer Figure 9).
For the 0.2% (1 in 500) AEP flood, the number of
buildings flooded above floor level increases to
32,000. For the extreme 0.001% (1 in 100,000)
AEP flood, an estimated 130,000 buildings
would be flooded above floor level.
Figure 9 – Number of existing buildings in
Brisbane that would flood above the lowest
habitable floor level for different sized floods
Population in Flood Plain
Population
HR1
HR2
HR3
HR4
HR5
2,000
17,000
40,000
41,000
182,000
Existing Buildings Flooded over Floor Level
Buildings
1 in 2 AEP
1 in 10 AEP
1 in 50 AEP
1 in 100 AEP
1 in 500 AEP
1 in 2,000 AEP
1 in 10,000 AEP
1 in 100,000 AEP
3,300
76,000
48,000
10
150
32,000
130,000
12,000
HR1 HR2 HR3 HR4 HR5
Proportion of properties impacted (%)
66
8
13
7
6
70
14
7
7
2
77
11
7
3
2
78
9
8
3
2
86
5
1
4
4
Residential
Industrial
Commercial
Other
Agricultural
The Brisbane River floodplain is
estimated to have the largest number
of existing buildings of any floodplain
in Australia.
2
Building numbers are indicative only based on the limitations of the Flood Study modelling and building database as described in
Section 6.3.8 of the TER.
25
Flood levels for different AEP events at the
Brisbane City and Ipswich gauges are presented
in Table 1. Sensitivity of the floodplain to
changes in flow means that flood levels increase
significantly from one AEP to the next. In the
mid reaches of the Brisbane River and the lower
reaches of the Bremer River, a 1% (1 in 100) AEP
flood is approximately three to four metres higher
than a 2% (1 in 50) AEP flood. A 0.2% (1 in 500)
AEP flood is approximately four to five metres
higher than a 1% (1 in 100) AEP flood.
Most properties located within the Brisbane
River floodplain are residential. Within
HR1 areas, two-thirds of the properties are
residential. The remaining properties are mostly
industrial, commercial and agricultural. For
lower risk areas HR2 to HR5, the proportion of
residential properties progressively increases
and the proportion of industrial, commercial and
agricultural properties progressively decreases
(refer Figure 10).
Approximately 2000
1
(see previous page) people
live within the HR1 area, which is the highest
hydraulic risk area (refer Figure 11). Residents
living in these areas may experience flooding
on a regular basis, with larger less frequent
floods resulting in financial losses, substantial
disruption to their lives and emotional stress.
Approximately 19,000
1
people live within the
combined HR1 or HR2 areas.
It is not just the occupants of directly affected
properties that are impacted by flooding. A much
larger section of our community can be indirectly
impacted as a result of services and facilities
affected by floods such as key transport network
linkages, loss of power and communications and
essential community services such as health
and welfare support. Loss of these services and
facilities can have cascading effects including an
inability to work, get to school, supply shops with
goods for consumption or impact on the ability to
evacuate.
Population in Flood Plain
Population
HR1
HR2
HR3
HR4
HR5
2,000
17,000
40,000
41,000
182,000
Existing Buildings Flooded over Floor Level
Buildings
1 in 2 AEP
1 in 10 AEP
1 in 50 AEP
1 in 100 AEP
1 in 500 AEP
1 in 2,000 AEP
1 in 10,000 AEP
1 in 100,000 AEP
3,300
76,000
48,000
10
150
32,000
130,000
12,000
HR1 HR2 HR3 HR4 HR5
Proportion of properties impacted (%)
66
8
13
7
6
70
14
7
7
2
77
11
7
3
2
78
9
8
3
2
86
5
1
4
4
Residential
Industrial
Commercial
Other
Agricultural
Figure 10 – Proportion of property types
impacted by flooding in each HR area
An estimated 280,000 people live in the
Brisbane River floodplain as at 2018.
Figure 11 – Approximate population
1
by HR areas
Population in Flood Plain
Population
HR1
HR2
HR3
HR4
HR5
2,000
17,000
40,000
41,000
182,000
Existing Buildings Flooded over Floor Level
Buildings
1 in 2 AEP
1 in 10 AEP
1 in 50 AEP
1 in 100 AEP
1 in 500 AEP
1 in 2,000 AEP
1 in 10,000 AEP
1 in 100,000 AEP
3,300
76,000
48,000
10
150
32,000
130,000
12,000
HR1 HR2 HR3 HR4 HR5
Proportion of properties impacted (%)
66
8
13
7
6
70
14
7
7
2
77
11
7
3
2
78
9
8
3
2
86
5
1
4
4
Residential
Industrial
Commercial
Other
Agricultural
2 Population numbers are indicative only based on building footprint counts (which is some areas does not identify multi-storey or multi-unit
dwellings) and census averages
26
Brisbane River Strategic Floodplain Management Plan
2.6 Economic impacts
The Queensland Strategy for Disaster Resilience
(2017) notes that Queensland is the most
disaster impacted state in Australia. The
frequency of tropical and ex-tropical cyclones
and storms in Queensland means that storm
and flood damage can be significant, requiring
enormous disaster relief and reconstruction
efforts. The Australian Government invests
Figure 11 – Approximate population
1
by HR areas
approximately $50 million each year in disaster
adaptation funding and in the last decade spent
more than $8 billion on post-disaster relief and
recovery (Productivity Commission, 2014).
Economic impacts of flooding in the Brisbane
River floodplain are detailed in Chapter 6 of the
Technical Evidence Report. The cost of flooding in
the Brisbane River floodplain has been estimated
by including both tangible and intangible
damages as outlined in Table 2.
Table 2 – Definition of tangible and intangible damages
Tangible (measurable) damages Intangible damages
Direct Indirect
Includes costs to repair or
replace damaged property,
goods, perishables and
infrastructure; or the loss in
value if it is not repaired or
replaced.
Includes the estimated loss in
production or revenue, loss of wages,
additional accommodation and living
expenses, and any other additional
expenses incurred by society due to
floods.
Indirect damages are estimated by
adding a factor to direct residential
and business losses in accordance
with Guidance on the Assessment
of Tangible Flood Damages by the
Department of Natural Resources,
Mines and Energy (2002).
Includes the ‘social costs’ of
flooding reflected in increased
levels of emotional stress and
psychological and physical
illness including loss of life.
Intangible damages also includes
environmental, cultural and
heritage losses incurred.
Intangible damages have been
estimated by reviewing the social
costs of catastrophic events in
Australia and overseas, including
the 2011 Brisbane River floods
and the 2009 Black Friday
bushfires in Victoria.
Refer to Section 6.1 of the Technical Evidence Report for further information
27
Intangible damages are difficult to measure
and meaningfully quantify in dollar terms.
Nevertheless, these are very real, significant and
often enduring ‘costs’ that emerge as a result of
disasters such as floods.
Estimated damages (tangible and intangible)
resulting from floods in the Brisbane River
floodplain are summarised in Table 3.
This Strategic Plan includes
intangible damages in the
assessment of overall economic
costs.
Table 3 – Estimated cost of flooding in the Brisbane River floodplain for different size floods
AEP Tangible
($million)
Intangible
($million)
Total
($million)
10% (1 in 10) $39 $0 $39
2% (1 in 50) $1,560 $190 $1,750
1% (1 in 100) $5,150 $1,610 $6,760
0.2% (1 in 500) $14,360 $11,050 $25,410
0.05% (1 in 2,000) $22,960 $24,500 $47,460
0.001% (100,000) $73,650 $127,100 $200,750
For a 1% (1 in 100) AEP flood, the total damage
cost is estimated at approximately $6.8 billion
($1.6 billion intangible and $5.2 billion tangible).
Refer to Figure 12. These costs are comparable
to actual damages incurred in the Brisbane River
floodplain as a result of the 2011 floods.
When considering the likelihood of all floods,
the total cost of flooding can be calculated on an
annual average basis , which is referred to as the
Average Annual Damages (AAD). This is the cost
incurred by flooding each year when averaged
over a significant period of time.
The AAD in the Brisbane River floodplain is $289
million per year, comprising $187 million for
tangible damages and $102 million for intangible
damages.
65%
Tangible
35%
Intangible
$289M per year
Average annual damage
28
Brisbane River Strategic Floodplain Management Plan
65%
Tangible
Average Annual Damage
35%
Intangible
$289M per year
Property damages
Intangible
Damages
Tangible
Damages
$m damages
2 505 10010 20020
Property damages
Residential
$m/year
HR1
6.8
HR2
21.4
HR3
17.6
HR4
4.1
HR5
1.8
Non-residential
$m/year
HR1
12.9
HR2
37.2
HR3
19.4
HR4
4.4
HR5
1.6
Expected Tangible Costs for a 1 in 100 AEP Event
= $5.2B total
Residential
$1.3B
Non-residential
$2.2B
Transport
$0.7B
Other infrastructure
$0.6B
Utilities
$0.1B
Clean-up
$0.2B
By comparison, tangible damages in the
Hawkesbury-Nepean River are estimated
at approximately $80 million per year. The
Hawkesbury-Nepean River has its own strategic
plan and is a catchment somewhat comparable
to the Brisbane River in its size. Located on the
outskirts of Sydney, it has long been regarded
as one of the most dangerous for flooding due
to the significant flood depths and evacuation
difficulties for local communities.
Figure 12 - Expected tangible costs for a 1%
(1 in 100) AEP flood
Figure 13 – Percentage of Average Annual
Damages for AEP floods
The Brisbane River has the highest
potential flood damages of any
floodplain in Australia.
The high flood damage costs for the Brisbane River
floodplain is due to the large number of properties
potentially affected by rare but devastating events.
More than 70 per cent of the total AAD is due to
floods that are rarer and larger than the 1% (1 in
100) AEP flood (refer Figure 13).
38%
29%
33%
Floods rarer than 0.2% (1 in 500) AEP
Floods up to 1% (1 in 100) AEP
Floods between 1 in 100 AEP
and 1 in 500 AEP
29
The AAD for the Brisbane River floodplain has
also been calculated for residential and non-
residential properties across different Hydraulic
Risk areas. HR1 is the highest risk area and
contains 880 residential and 460 non-residential
buildings, from which tangible damages of
$6.8 million per year and $12.9 million per year
would be derived, respectively (refer Figure 14).
Impacts to property within HR2 contribute
the most to the AAD for both residential and
non-residential damages due the high frequency
of flooding.
HR5 contains by far the largest population and
largest number of buildings (approximately
83,000). However, its contribution to the AAD
is minor as it is very rare for these properties to
be impacted.
65%
Tangible
Average Annual Damage
35%
Intangible
$289M per year
Property damages
Intangible
Damages
Tangible
Damages
$m damages
2 505 10010 20020
Property damages
Residential
$m/year
HR1
6.8
HR2
21.4
HR3
17.6
HR4
4.1
HR5
1.8
Non-residential
$m/year
HR1
12.9
HR2
37.2
HR3
19.4
HR4
4.4
HR5
1.6
Expected Tangible Costs for a 1 in 100 AEP Event
= $5.2B total
Residential
$1.3B
Non-residential
$2.2B
Transport
$0.7B
Other infrastructure
$0.6B
Utilities
$0.1B
Clean-up
$0.2B
Figure 14 – Estimated property damage costs by Hydraulic Risk categories
2.7 Existing dam flood
operations
Both Somerset and Wivenhoe dams include
purpose-designed flood mitigation capacity
and are well located within the Brisbane River
catchment to provide significant flood mitigation
during many flood events.
Impacts from floods in 1999 and 2013 were
mitigated to the extent that potentially Major
flood conditions were reduced to only Minor
flood levels. In 2011, the dams effectively
reduced peak flood levels by 2.8 metres at
Ipswich, 2.3 metres at Fernvale,
3.2 metres at Moggill and 2 metres at Brisbane
City. These estimated flood levels are relative to
the equivalent ‘no dams’ scenario modelled in
the Flood Study.
Central to the dams’ ongoing flood mitigation
effectiveness is the ability to establish flood
operation procedures that reduce adverse
impacts downstream. Planning for the reduction
of flood impacts requires an understanding of
potential damages across the range of Brisbane
River flood flows.
30
Brisbane River Strategic Floodplain Management Plan
Estimates of the number of flooded properties
and buildings (based on 2017 development) for
various Brisbane River flow rates are shown in
Figures 15 and 16. These figures show the impacts
for flow rates at Moggill up to 10,000 cubic metres
per second.
Figure 15 – Number of properties flooded above ground level
The impact bands shown in Figures 15 and 16
are based on consideration of:
1. AEP flood impacts (for Brisbane River
and tributary inflows) incorporated in the
Technical Evidence Report
2. additional modelling of constant Brisbane
River flows downstream of Wivenhoe
Dam with no inflow contributions from
downstream tributary catchments.
Figure 16 – Number of buildings flooded above floor level
0
1,50 0
3,000
4,500
6,000
7,500
9,000
10,5 00
12,0 00
13,5 00
15,0 00
1,00 0 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,0 00
Number of properties
Brisbane River flow at Moggill (m
3
/s)
0
1,50 0
3,000
4,500
6,000
7,500
9,000
10,5 00
12,0 00
13,5 00
15,0 00
1,00 0 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,0 00
Number of buildings
Brisbane River flow at Moggill (m
3
/s)
Impact band for residential properties*
Brisbane River AEP floods (incl tributaries)
Brisbane River constant flows (excl tributaries)
Impact band for non-residential properties*
Brisbane River AEP floods (incl tributaries)
Brisbane River constant flows (excl tributaries)
Impact band for residential properties*
Brisbane River AEP floods (incl tributaries)
Brisbane River constant flows (excl tributaries)
Impact band for non-residential properties*
Brisbane River AEP floods (incl tributaries)
Brisbane River constant flows (excl tributaries)
31
2.8 Environmental benefits
Risks to community safety and property
from flooding are significant. However, the
environmental and economic benefits of floods
should also be acknowledged in the context
of floodplain management as highlighted in
Understanding Floods: Questions and Answers
(State of Queensland, 2011) as follows.
“In many natural systems, floods play an important
role in maintaining key ecosystem functions and
biodiversity. They link the river with the land
surrounding it, recharge groundwater systems,
fill wetlands, increase the connectivity between
aquatic habitats, and move both sediment and
nutrients around the landscape, and into the
marine environment. For many species, floods
trigger breeding events, migration, and dispersal.
These natural systems are resilient to the effects of
all but the largest floods.
The environmental benefits of flooding can
also help the economy through things such
as increased fish production, recharge of
groundwater resources, and maintenance of
recreational environments.”
The natural variation in the flow regime is
required to sustain freshwater ecosystems.
This includes flood events where water flows
out onto floodplains or down waterways to
wetlands. The flood characteristics determine
the amount and quality of habitat created for
different organisms to complete their life cycles,
as well as providing opportunities for carbon and
nutrients to be exchanged between the river and
floodplains. The importance of this natural cycle
for the Moreton Bay area was considered in the
preparation of the Queensland legislation Water
Plan (Moreton) 2007.
Flooding can also contribute positively to the
rural economy through the replenishment of
groundwater aquifers and the deposition of
nutrients onto floodplains used for primary
production.
Section 2.2.4 of the Technical Evidence Report
provides further detailed analysis of the
environmental benefits of floods.
2.9 Future flood risk
Future flood risk may be impacted by urban
development as well as possible changes to our
climate. There is still much uncertainty regarding
conditions of the Brisbane River floodplain over
the long term. Sensitivity assessments have been
carried out to help understand the impact that
potential future changes may have on flooding in
the Brisbane River floodplain if measures aimed
to mitigate such changes are not adopted.
The results of these sensitivity assessments are
described below.
2.9.1 Urban development
ShapingSEQ, the regional plan for South East
Queensland, indicates that the South East
Queensland population is expected to grow by
an additional 1.8 million people over the next
25 years. While some of this growth includes
expansion of urban areas including some new
areas within the floodplain, much of it will be
accommodated through consolidation of existing
areas. An increase in the density of existing
development within the floodplain will increase
the population exposed to floods, and without
mitigation measures such as through appropriate
land use treatments, could potentially increase
flood risk in the future.
Flood levels in the Brisbane River
floodplain are sensitive to filling in the
floodplain as well as the anticipated
changes in rainfall and sea level due
to climate change.
32
Brisbane River Strategic Floodplain Management Plan
As well as increasing the population that would
be exposed to flood risk, future development
within the floodplain could modify flood
behaviour. This could occur through changes
to landform such as filling of land in order to
elevate the area above a known flood level,
and introducing built structures and impervious
areas. Such changes may lead to increased flood
risk in nearby areas, especially if development
occurs within flood conveyance areas (refer
Section 2.1 of this Strategic Plan).
Section 5.1 of the Technical Evidence Report
explains how flood modelling was used to
assess the sensitivity of flooding to filling areas
identified for future urban development. This
work was based on two scenarios considered
to represent the lower and upper bounds
of flooding. The results of the modelling
demonstrate that cumulative impacts across
these future urban areas could potentially lead
to sizeable increases in flood levels across the
floodplain. For example, in the 1% (1 in 100)
AEP flood event the upper bound impacts result
in flood level increases of 0.9 metres at David
Trumpy Bridge (Ipswich), 0.4 metres at Jindalee,
0.3 metres at Moggill and 0.1 metres at Brisbane
(City Gauge).
2.9.2 Climate change
Australian Rainfall and Runoff (Ball et. al., 2016)
recommends climate change be considered as
part of flood investigations in accordance with
recommendations of the Intergovernmental Panel
on Climate Change (IPCC). The IPCC provides a
range of projections for future climate conditions
based on an understanding of global climate
and weather models. Researchers have taken
these global projections and downscaled them
to local areas. For the Brisbane River Catchment,
local estimates for future sea level rise and
changes to rainfall have been sourced from the
Commonwealth Scientific and Industrial Research
Organisation (CSIRO), Bureau of Meteorology (the
Bureau) and the Queensland Government. These
local estimates are discussed in detail in Section
5.2 of the Technical Evidence Report.
Sensitivity testing of future climate change
conditions has been carried out looking at 2050
and 2090 timeframes for two IPCC scenarios that
relate to different emission levels. The IPCC’s
Representative Concentration Pathway (RCP) 8.5
for 2090 aligns with the Queensland Climate
Adaptation Strategy 2017–2030 (Q-CAS). It
identifies an increase in rainfall intensity of
33
20 per cent for the Brisbane River Catchment as
well as sea level rise of 0.8 metres for adjacent
marine waters. The Q-CAS states the following:
“in 2030, under a high greenhouse gas
emissions scenario [i.e. IPCC’s RCP 8.5 scenario],
Brisbane’s climate is projected to be more like the
current climate of Bundaberg”.
Further information about the impact of climate
change on the risks posed by natural hazards in
Queensland is included in the Queensland State
Natural Hazard Risk Assessment 2017.
Flood modelling results from the projected
climate changes indicate the Brisbane River
floodplain is particularly sensitive to changes in
rainfall, with flood levels increasing significantly
in some locations. In the 1% (1 in 100) AEP
event, flood levels at the Brisbane City Gauge
increase between 1.2 metres to 2.5 metres
76%
Vulnerable
Population
Vulnerable
Population
50%
HR1 HR2-5
Phase 1
2013
Phase 2
2017
Phase 3
2018
Phase 4
Commencing
2018
Data
Collection
Brisbane
River
Catchment
Flood Study
Strategic
Floodplain
Management
Plan
+
Technical
Evidence
Report
Local
Floodplain
Management
Plans
COMPLETE
COMPLETE
COMPLETE
Climate change impacts on AAD
$300M/yr to
$430M/yr
$187M/yr
Today 2090
Floods up to
1 in 100
AEP
Floods between
1 in 100
AEP
and
1 in 500
AEP
Floods rarer than
1 in 500
AEP
29%
38%
33%
Figure 17 – Climate change impacts on tangible average annual damages
across the scenarios tested. A similar trend is
observed in Ipswich at David Trumpy Bridge,
with flood levels increasing by 0.9 metres to 2.4
metres. As a result, the estimated average annual
cost of tangible damage in the year 2090 (under
RCP 8.5 and RCP 4.5 conditions) more than
doubles that of current flood conditions (refer
Figure 17).
Under the higher RCP 8.5 scenario, by 2050
the 1% (1 in 100) AEP flood level is projected
to be comparable to a current day 0.5% (1 in
200) AEP level. From a risk-based perspective,
if unmanaged this increase in flood severity and
magnitude for a given likelihood will increase the
overall risk profile across the floodplain.
34
Brisbane River Strategic Floodplain Management Plan
Desired outcomes of this
Strategic Plan
Desired outcome 1
Floodplain management
initiatives are delivered using
a holistic, integrated and
collaborative approach
The principles of integrated catchment planning
are outlined in Section 1.4 of this Strategic
Plan. It is essential that this collaborative and
coordinated approach is applied within the
catchment to achieve integrated outcomes for
water supply, landscape management, land
use planning and floodplain management.
This rationale is expanded in Chapter 3 of the
Technical Evidence Report.
Opportunities for information and resource
sharing, and continuous improvement will be
explored by stakeholders and overseen by
the governance arrangements identified in
Section 5 of this Strategic Plan. The governance
arrangements will support improved coordination
of flood resilience actions across the floodplain
and between agencies.
Outcome 1 will be achieved using the following
key strategies.
Strategy 1.1 – Integrated catchment planning
principles adopted in this Strategic Plan
are carried forward in all future floodplain
management initiatives
Future floodplain management initiatives will be
delivered using integrated catchment planning
principles.
Stakeholders will work collaboratively to identify
opportunities and embed integration principles
into the range of flood management initiatives
identified within this Strategic Plan.
Stakeholders will continue to recognise other
planning processes underway and engage with
relevant entities to identify where projects can
complement each other and avoid duplication.
I
N
T
E
G
R
A
T
E
D
C
A
T
C
H
M
E
N
T
P
L
A
N
N
I
N
G
Resilient
buildings
Community awareness
and resilience
Land use
planning
Disaster
management
Current/future
flood risk
Structural
mitigation options
Landscape
management
I
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T
E
G
R
A
T
E
D
C
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T
C
H
M
E
N
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P
L
A
N
N
I
N
G
Strategic
Floodplain
Management
Plan
35
Strategy 1.2 – Learnings from effective
awareness and resilience activities and
new research findings are shared
throughout the catchment via collaborative
professional forums
Evaluating the effectiveness of resilience
activities more regularly and systematically
across the floodplain will enable results to be
shared regionally to support shared learnings for
continuous improvement.
Ongoing research into emerging areas of
resilience will help inform the implementation
of resilience building activities. This includes
consideration of the effectiveness of
psychological preparedness before a flood and
ongoing mental health outcomes in recovery.
Research into new technologies is also a key
area for consideration, including innovations
such as virtual reality tools. New technologies
provide opportunities to deliver more informative
and persuasive visualisations, and to deliver
personalised information and warnings that
could more effectively contribute to attitude and
behaviour change. Volunteer coordination and
education programs through schools is another
area of influence that can be investigated further.
To support this strategy, a program of evaluations
can be undertaken and incorporated into the
resilience activity compendium (part of Strategy
4.1) in addition to an ongoing program of
evaluations and research on flood resilience. The
findings of any evaluation and research program
can be shared through ongoing collaborative
regional arrangements with local government and
state agency representatives. Representatives of
peak business, professional groups, community,
real estate and insurance bodies can also
be involved (where required) to facilitate
collaborative approaches to activities that build
community resilience.
Strategy 1.3 – Consistent information sharing
at a regional-scale is emphasised and
supported through a cycle of continuous
improvement
A key challenge identified by stakeholders
is sharing information and data between
agencies both during and outside of flood
events. Opportunities for improved and ongoing
interagency information sharing includes the
following:
• Continue the approach used to develop
regional-scale flood analysis and
information for the development of Local
Floodplain Management Plans. Delivery
of a consistent approach and outputs will
facilitate simpler data sharing and collation
mechanisms across the region.
• Investigate opportunities to enhance
information sharing, including
development of standard information
requests at the commencement of each
wet season, regular meetings of disaster
management groups across the catchment,
and investigation into platforms which
enhance interoperability between incident
management systems.
• Adopt new products, services and findings
into disaster management processes as
they become available, including updated
flood forecast products from the Bureau.
• Investigate options for a regional, real-
time flood forecasting / modelling
system to improve the ability of disaster
management officers to forecast flood
behaviour and impacts during a flood. This
can be pursued in a staged manner such
as the short-term development of simpler
approaches followed by longer-term
planning for a world-class, real-time flood
modelling system for the region.
• Communicate implications of any upgrades
to the Wivenhoe and Somerset Dams on
flood risk and modelling.
36
Brisbane River Strategic Floodplain Management Plan
Desired outcome 2
Floodplain management
initiatives are informed by a
regional understanding of
current flood risks
A key driver for the Brisbane River Catchment
Flood Studies was to develop a regional
understanding of flood behaviour and
consequences that is consistently considered
across the catchment and not constrained by
administrative boundaries.
The modelling undertaken in the Flood Study,
combined with the comprehensive analysis of
current flood risks within the floodplain provides
this regional understanding. Refer to Chapter 4 of
the Technical Evidence Report for further detail.
A shared understanding of Potential Hydraulic
Risk (refer Appendix C) has been established
as a common foundation for representing and
comparing the hydraulic behavior across multiple
flood likelihoods. Potential Hydraulic Risk in
combination with other flood risk factors such as
community exposure, vulnerability and isolation,
provides the basis for complete flood risk
assessments.
The methodology used to undertake the
regional flood risk assessment, including the
agreed definition of Potential Hydraulic Risk
as one of the risk assessment factors, can be
applied by all authorities across the Brisbane
River floodplain to maintain this consistent
understanding of flooding.
Outcome 2 will be achieved using the following
key strategy.
Strategy 2.1 – Floodplain management
initiatives incorporate a shared definition of
Potential Hydraulic Risk across the floodplain
Floodplain management initiatives undertaken
within the Brisbane River Catchment, which
adopt the same definition of Potential Hydraulic
Risk as agreed and applied in this Strategic Plan
(refer Appendix C) will maintain a consistent,
catchment-wide approach to understanding
flood behaviour. This shared understanding
then becomes the common basis from which
locally tailored floodplain management
processes are undertaken.
37
Desired outcome 3
Future climate change impacts
are recognised and planned
for through adaptation and
resilience building
“There is now widespread acceptance that human
activities are contributing to observed climate
change. Human induced climate change has
the potential to alter the prevalence and severity
of rainfall extremes, storm surge and floods.
Recognition of the risk associated with climate
change is required for better planning”
Bates, et al., 2016, Climate Change Considerations, Chapter
6 in Book 1 of Australian Rainfall and Runoff - A Guide to
Flood Estimation, Commonwealth of Australia
Section 5.2 of the Technical Evidence Report
analyses the results of climate change modelling
undertaken as part of the development of
this Strategic Plan. Whilst the investigations
undertaken are considered a sensitivity analysis,
they are in line with the recommendations of
Australian Rainfall and Runoff (Ball et al., 2016),
and conclusively demonstrate that climate
change has the potential to significantly alter
flood behaviour in the catchment, including
notable increases in flood levels (and hence
flood risks) across most of the floodplain.
To achieve adaptable and resilient communities,
floodplain management actions should be
prioritised based on the ‘no regrets’ principle.
That is, measures are taken with the aim of
responding to possible negative impacts before
they intensify, which improves the quality of
life today as well as helping to mitigate future
adverse conditions.
Outcome 3 will be achieved using the following
key strategies.
Strategy 3.1 – Climate change is incorporated
into the preparation and implementation of
the Strategic Plan actions
Given the scale of potential changes to flood
behaviour in the Brisbane River Catchment, climate
change will require a multi-faceted response if
long-term safety and resilience is to be achieved.
As such, the potential impacts of climate change
should be considered in the implementation of all
actions of this Strategic Plan.
Ongoing monitoring of climate change and its
impacts within the Brisbane River Catchment will
be essential for future adaptation planning and
response.
The sensitivity approach adopted to date is
appropriate for use and remains consistent
with best practice guidance (Ball et al., 2016).
Sensitivity analysis supports decision making
in the face of uncertainty by providing an
understanding of the potential impacts from
a range of climate change scenarios. Where
analysis shows there is potential for a significant
increase in impacts and/or there is limited
scope for mitigation, a conservative climate
change scenario should be adopted such as that
outlined in RCP 8.5.
As part of the Local Floodplain Management
Plans, ‘no regrets actions’ can be identified for
immediate implementation whilst a longer-term
climate change adaptation plan is established.
These ‘no regrets actions’ provide immediate
benefit, as well as helping to mitigate against
adverse future changes.
38
Brisbane River Strategic Floodplain Management Plan
Some possible actions could include:
• Adopting a managed adaptive approach,
whereby action is taken when particular
trigger points are observed. It is most
appropriate in cases where ongoing
responsibility can be assigned to tracking
the change in risk, and managing that risk
through pre-determined interventions. For
example, incorporating larger structural
foundations that would allow for future
upgrades should the climate trigger unfold.
• Incorporating an allowance for climate
change when considering built form. For
example, using a Defined Flood Event that
incorporates an additional climate change
factor allowance or resilient building
design to accommodate some of this
exposure. This would not only reduce the
consequences of larger floods (assuming
no changes in climate conditions), but also
future floods which may be influenced by
climate change.
Strategy 3.2 – A coordinated and holistic
approach is undertaken to respond to a
changing climate in the future
Adapting to changes in climate will require long-
term and flexible planning that is built on the
best available science and linked to observable
triggers. It involves collaboration and monitoring,
and should consider opportunities as well as
risks. Climate change adaptation planning within
the Brisbane River Catchment will extend well
beyond floodplain management and is best
undertaken within an integrated catchment
planning framework and at a regional scale.
39
To achieve adaptable and resilient communities,
stakeholders will work together to become a
more flood resilient community by progressing
the community flood resilience outcome of
a risk-informed, appropriately-prepared and
adaptable community.
Outcome 4 will be achieved using the following
key strategies.
Strategy 4.1 – Regionally consistent flood
terminology and approaches to resilience
building activities are supported through
the development of a Communication and
Engagement Framework Compendium
To avoid confusion, resilience building activities
require regionally consistent information
and messaging. This includes consistent
key messages, language and terminology,
flood-risk categories, mapping outputs and
mapping functionality. Regionally consistent
explanations of key concepts and terminology
will assist residents and visitors to understand
flood-risk information and support appropriate
preparedness actions.
This strategy is supported by the proposed
development of a regional information resource
consisting of a communication and engagement
framework compendium of evaluated resilience
activities and a toolkit of effective activities for
local implementation. Local governments and
agencies will continue to lead and implement
locally responsive activities, while utilising
this resource to ensure regionally consistent
approaches and terminology.
Desired outcome 4
Community awareness,
understanding and response is
the foundation for community
resilience
Community awareness and resilience is
discussed in detail in Chapter 11 of the
Technical Evidence Report. Flood resilient
communities have the knowledge, skills and
capacity to prepare, respond and adapt to
floods. Community resilience activities focus
on awareness and education, building and
maintaining strong community and agency
networks, and community-led actions.
Section 11.3 of the Technical Evidence Report
identifies a variety of activities currently being
undertaken throughout the floodplain by the
Queensland Government, local governments,
other agencies and communities. These activities
range from broad awareness-building advertising
campaigns for multiple hazards using traditional
and new media, to programs targeting specific
vulnerable groups using one-to-one engagement.
Whilst community awareness and resilience
activities should be tailored to suit individual
communities, there are opportunities for improved
regional alignment, planning and coordination.
40
Brisbane River Strategic Floodplain Management Plan
Strategy 4.2 – Regionally consistent flood
risk data is made available throughout the
catchment to inform risk assessments and
preparedness actions
Consistent flood-risk mapping data will
be supported by referencing the regional
Communication and Engagement Framework
Compendium (part of Strategy 4.1). Regionally
consistent flood risk categories, design elements
(for example, the colours used for flood risk
categories) and mapping functionality used for
flood awareness purposes across the floodplain
will increase the community’s ability to easily
reference and understand their flood risk.
Where not currently available, flood risk
mapping should be available for property-
specific enquiries and continue to be updated,
improved and shared over time. This includes
using new technologies to provide more targeted
and geographically-specific risk information to
support attitudes to flood risk and create positive
behaviour change.
Strategy 4.3 – A range of engagement
approaches are used to increase community
involvement and strengthen social networks
Strong community networks contribute to
community resilience by building the social
connections between community members
and governments. Awareness and educational
activities that aim to strengthen social networks
may be more effective at creating attitudinal
and behaviour change than those without
social involvement.
As well as awareness and educational resilience
activities, a range of engagement approaches
should be undertaken to:
• involve and empower the community in
planning and decision-making related to
flood risk and disaster management
• use and strengthen social networks
• support community-led initiatives.
Community involvement may also include
workshops with networks of organisations to
undertake continuity planning and community
champion programs. This strategy may also be
supported by community development training
for disaster management officers.
41
Desired outcome 5
Land use is planned, located
and considers design elements
to ensure development
appropriately responds to the
level of flood risk
Land use planning plays a key role in avoiding
or mitigating flood risk to new development,
particularly in respect to managing future risk.
The Queensland land use planning system
requires land use planning authorities to adopt
a risk-based approach for managing flood
risk in local planning instruments and new
development. This involves understanding
flood behaviour across the full spectrum of
flood hazard conditions and likelihoods, as
well as the implications for future development,
to determine its acceptability or tolerability to
current and future flood risk.
Analysis undertaken to inform this Strategic
Plan has identified that the Brisbane River
floodplain is sensitive to the impacts of any
future development which relies on filling. The
floodplain is also sensitive to the projected
effects of climate change.
Land use planning therefore has a key role to
play in supporting resilience of the region’s
settlement pattern to current and future flood
risk by ensuring a ‘no worsening’ of existing flood
risk arises from new development. The four local
government planning schemes regulate much
of the development in the floodplain. However,
there are other planning mechanisms such
as Priority Development Area – Development
Schemes, which apply in specific areas of the
floodplain.
Consistent approaches to the way flood risk is
identified, evaluated and treated, are proposed
to support floodplain wide land use planning
outcomes.
Outcome 5 includes strategies to address
regionally consistent responses in the following
areas:
• a regional impact assessment and ‘no
worsening’ of flood risk as a result of
cumulative land form change in the
floodplain
• avoidance of vulnerable land uses
involving vulnerable persons in areas of
increased flood risk
• regional assessment of flood evacuation
capability and evacuation networks.
Other strategies supporting regionally consistent
land use planning outcomes are addressed
elsewhere in this Strategic Plan as follows:
• Strategy 2.1 addresses the adoption
of an agreed definition of Potential
Hydraulic Risk as a key input to flood risk
assessments
• Strategy 3.1 identifies a common approach
to responding to the anticipated impacts of
climate change
• Strategy 4.2 aims to provide regionally
consistent flood risk data.
Local integration of these elements of regional
consistency through local planning instruments
will be informed by Local Floodplain Management
Plans and local flood risk assessments which
may identify the potential to evaluate planning
changes against regional growth assumptions.
Local governments can collaborate with the
Queensland Government to understand these
implications and improve the resilience of future
development to future flood risks.
42
Brisbane River Strategic Floodplain Management Plan
The State Planning Policy Natural Hazards, Risk
and Resilience (Flood) Guidance Material, in
conjunction with the Land Use Planning Guide
are non-statutory resources designed to assist
planning authorities assess and treat flood risk
through land use planning methods.
Analysis and discussion of land use planning
and its role in managing flood risk is discussed
in detail in Chapter 9 of the Technical Evidence
Report.
Outcome 5 will be achieved through the
following key strategies.
Strategy 5.1 – Planning instruments across
the floodplain are informed by local flood
risk assessments
The requirement for local flood risk assessments
to inform local planning instruments is
embedded in the SPP. Development of Local
Floodplain Management Plans across the
Brisbane River floodplain may be used to inform
local planning instruments. Local Floodplain
Management Plans should consider the
requirements of the SPP, with regards to the
scope of local flood risk assessments where
they are intended to inform the review of local
planning instruments.
Strategy 5.2 – Local Floodplain Management
Plans, local flood risk assessments and local
planning instruments consider the following:
• potential hydraulic risk and hazard
classification
• regional evacuation capability
• ‘no worsening’ of flood risk from new
development
• regional assessment of cumulative land
form changes across the floodplain
• regional climate change adaptation.
The role of this Strategic Plan in
land use planning
This Strategic Plan provides a framework
to guide flood responsive land use
planning for planning authorities and
local governments in the Brisbane River
floodplain. It supports the outcomes of
ShapingSEQ and the SPP state interest for
natural hazards, risk and resilience (flood).
The purpose of the land use planning
components of this Strategic Plan is to
provide regional context for flood risk
management and strategic land use
planning. It is not statutory in its effect.
However, it supports the implementation
of the SPP state interest (flood) through
local land use planning.
This Strategic Plan seeks to achieve
regionally consistent flood risk
management outcomes assessment and
decision making processes implemented
by local jurisdictions and institutions. It
does not alter the statutory effect of the
SPP (including the need to balance other
state interests) or the statutory effect of
ShapingSEQ. It does however provide
potential for review of regional strategies
for flood risk management in future
iterations of local planning instruments
and ShapingSEQ.
Land Use Planning Guidance material
has been developed. The Brisbane River
Strategic Floodplain Management Plan
Technical Evidence Report –Land Use
Planning Guidance Material Addendum
(Land Use Planning Guide)
is non-statutory and intended as a
resource to assist planning authorities
achieve key outcomes of this Strategic
Plan when undertaking local land use
planning processes.
43
Evacuation capability is a key input to a
range of floodplain management initiatives
including land use planning. An assessment
of regional evacuation capacity and capability
and the region’s evacuation network is a
recommendation of this Strategic Plan. The
outcomes of this analysis will provide important
insights that will inform local flood risk and risk
based land use planning in the floodplain.
‘No worsening’ of flood risk is defined in the
Glossary of terms (refer Appendix A) and requires
the assessment of development at both the
strategic and lot scales. This is to consider
the impact that developments may have on
neighbouring sites and elsewhere on the
floodplain.
A regional assessment of the cumulative impacts
of landform change across the floodplain
is proposed as a recommendation of this
Strategic Plan. The outcomes of this analysis will
determine at a floodplain scale, the extent and
location of filling or land form change to support
new development that is possible without
causing unacceptable cumulative impacts
on flood risk. This analysis can inform the
development of Local Floodplain Management
Plans, local risk assessments and cascade into
the land use allocation, provisions and policy
under local and other planning instruments.
Strategy 5.3 – Local planning instruments
incorporate consistent approaches that
protect vulnerable people from increased
flood risk
Vulnerable land uses are those most impacted
if subject to flooding. The Land Use Planning
Guidance contained in the Technical Evidence
Report describes these uses. A key factor
affecting land use vulnerability is whether it
performs functions that support vulnerable
people, who due to physical, cognitive or other
constraints have reduced resilience to floods and
are therefore at greater risk.
When developing land use responses and
particularly in allocating land uses, as well as
considering the risk and risk treatment to determine
the acceptability and tolerability, consideration
should also be given to the vulnerability profile of
the community where known.
Vulnerable land uses involving vulnerable
persons should not occur in areas of high flood
risk or where evacuation risk is assessed as
moderate, serious or intolerable. Local planning
instruments should apply this principle when
planning for vulnerable land uses supporting
vulnerable persons.
Strategy 5.4 – Local Floodplain
Management Plans, flood risk assessments
and the review of local planning instruments
consider implications for regional planning
assumptions
The review of planning instruments informed by
a refined understanding of flood risk may identify
a need to adjust regional planning assumptions
about dwelling and employment supply, its
distribution and infrastructure considerations.
These should be undertaken collaboratively by the
region’s local governments and the Queensland
Government to inform the annual land supply
assessments of the SEQ Growth Monitoring
Program and future reviews of ShapingSEQ.
44
Brisbane River Strategic Floodplain Management Plan
Desired outcome 6
Building design and construction
improves community resilience
and reduces property damage
The interface between planning and building
systems is recognised as an area of uncertainty
for natural hazard practitioners in terms of
policy development, regulation and practical
implementation.
The Queensland Development Code MP 3.5 is
triggered when building work is carried out within
a local government declared flood hazard area
with a defined flood level. The purpose of this
code is to ensure minimum flood immunity of
habitable areas and the structural integrity of
buildings located in flood hazard areas. This is
designed to safeguard people from illness and
injury caused by flood water affecting buildings
and to ensure utilities are protected from the
effects of floodwaters.
The Queensland Development Code MP 3.5
does not specifically cover flood resilient design
principles. However, Acceptable Solution A1
relies on Section 2.8 of the National Flood
Standard – Construction of Buildings in Flood
Hazard Areas Version 2012.2 (2012) for the
structural element. The National Flood Standard
does not provide information on materials,
appropriate uses or the expected benefits and
costs associated with flood resilient design.
Reducing the physical damage to possessions,
whilst enabling people to return to their homes
and workplaces sooner, improves the resilience
of a community to floods. Flood resilient
construction principles extending beyond
structural integrity have the ability to reduce the
intangible and tangible damages from floods.
Outcome 6 will be achieved through the
following key strategies.
Strategy 6.1 – Develop guidance on how
flood resilient building design principles can
be applied, assessed and built
Targeted and specific guidance for planners,
engineers, homeowners, architects, builders and
certifiers about wet-proofing new and renovated
residential properties, will provide greater clarity
on how built form can increase flood resilience
under current legislation and arrangements.
This guidance should be developed specifically
for the Queensland context and housing stock,
and where possible provide a compendium
of materials currently on the market that are
appropriate in various applications.
Strategy 6.2 – Further encourage and
support the uptake of flood resilient built
form through greater clarity in legislative
arrangements
In Queensland, the distinction between planning
and building systems is an identified source of
uncertainty for practitioners, particularly about
what can and cannot be achieved under current
arrangements. Specific information about how
the wide range of professions can interact with
the current system will provide greater certainty.
Furthermore, given the move towards risk based
approaches, consideration should also be given
to whether modifications to the current building
arrangements are required.
45
Desired outcome 7
Infrastructure is used to reduce
flood risks where appropriate
Infrastructure located within the floodplain can
modify flood behaviour. This generally involves
heavily engineered works and can encompass
a range of structural options for flood risk
management including dams, levees, detention
basins and flood gates. As flood behaviour
in the Brisbane River is sensitive to flow and
floodplain conditions, infrastructure can be used
to alter flood behaviour and potentially mitigate
adverse impacts. It is due to this sensitivity that
infrastructure may also have detrimental effects
to other areas within the floodplain.
Wivenhoe and Somerset dams provide significant
flood mitigation within the Brisbane River
Catchment (refer Section 2.7). Despite this,
dams and other infrastructure cannot prevent
or eliminate flood risk downstream caused by
extreme flood events.
A large number of possible structural solutions
to flooding in the Brisbane River Catchment
have been suggested in recent years. These
have covered large-scale and regional solutions
ranging from new dams in the upper catchments
to smaller more localised solutions. More
than 300 options were submitted to the QFCoI
by the public and stakeholders. In addition,
the Queensland Government carried out
targeted investigations into additional flood
storage within the Brisbane River Catchment
(Prefeasibility Investigation into Flood Mitigation
Storage Infrastructure, Department of Energy and
Water Supply, 2014).
Seqwater is progressing feasibility planning for
options to upgrade Wivenhoe Dam to safely pass
a Probable Maximum Flood event. A preferred
upgrade concept for Wivenhoe Dam may increase
the flood mitigation benefit, although this is
yet to be determined. Given investigations are
already progressing on Wivenhoe Dam options,
this Strategic Plan focuses on other infrastructure
works that can provide regional benefits to flood
risk in the Brisbane River floodplain that are
congruent with possible future dam upgrades.
A range of infrastructure options for the Brisbane
River Catchment are discussed in Chapter 8 of
the Technical Evidence Report. Infrastructure
can involve high capital costs as well as ongoing
maintenance costs. Economic benefits can be
measured in terms of reductions in future flood
damages, for both tangible and intangible
damages. Feasibility of new infrastructure
for flood mitigation purposes should not be
judged solely on financial merit. It should also
consider a range of social and environmental
factors including potential benefits to integrated
catchment planning outcomes. This Strategic
Plan has adopted a multi-criteria assessment
to evaluate and compare the merits of various
structural options across a selection of criteria
including community safety, economic viability,
technical feasibility, community attitudes,
infrastructure and transport, environmental
impact and natural resource management.
Outcome 7 will be achieved through the
following key strategies.
46
Brisbane River Strategic Floodplain Management Plan
Strategy 7.1 – Feasibility assessment of
regional opportunities and linkages with
other regional projects
Warrill Creek Dry Flood Mitigation Dam (refer
Technical Evidence Report Section 8.6.2)
Preliminary investigations of this option were
carried out by the Department of Energy and
Water Supply in 2014. The Commonwealth’s
Inland Railway project is proposing to construct a
high level embankment across Warrill Creek (on
the alignment of the Southern Freight Railway
Corridor). With appropriate design of the wall and
outlet structure, the new railway infrastructure
could be used to provide temporary flood storage
(flood detention) upstream, providing significant
benefit to downstream properties, as well as
providing critical road immunity for the Amberley
Royal Australian Air Force Base. It is anticipated
that concept design refinement could optimise
detention benefits and minimise infrastructure
costs. A detailed benefit-cost analysis should
be carried out on the optimised design using
the most up-to-date flood model and property
database developed through the Flood Studies.
Re-evaluation of catchment hydrology under a
dry flood mitigation dam condition for
Warrill Creek will be required to identify an
appropriate ensemble of specific events that
produces peak flood levels throughout the
Brisbane River floodplain.
Cooperation between all levels of government
will be required to achieve the integrated
and multiple potential benefits possible for
this structural option. Such cooperation and
coordination between governments is central
to the integrated catchment planning principles
advocated by the QAO (2016).
Strategy 7.2 – Further consideration of local
opportunities through Local Floodplain
Management Plans
Brisbane CBD and South Brisbane temporary
flood barriers (refer Technical Evidence Report
Sections 8.5.2 and 8.5.3)
The Brisbane CBD and South Brisbane
(Southbank) are special interest areas with
substantial economic, tourism and cultural
uses. Whilst these locations are not suitable
for permanent levees, temporary flood barriers
can be an effective means of protecting small
areas of inundation that have relatively confined
connections to the main watercourse. The
temporary nature of the barriers means that they
can be deployed in locations that are normally
used for other purposes such as roadways. The
practical size of the barriers limits the extent
to which floods are excluded from areas of
interest, while they need to be complemented
with other measures to prevent backflow of
floodwaters through stormwater systems and
other flow paths. Initial assessments suggest
temporary flood barriers could provide flood
immunity potentially up to the 1% (1 in 100)
AEP flood for South Brisbane and 0.5% (1 in
200) AEP flood for the Brisbane CBD. Further
investigation is required.
Ipswich CBD flood gate (refer Technical Evidence
Report - Section 8.4.6)
The Ipswich CBD is low-lying and parts are
impacted by 5% (1 in 20) AEP floods. Flood
waters passing through the Marsden Parade
Rail Underpass inundate mostly commercial
properties in the CBD. Marsden Parade is an
important local access route across the rail line.
Further consideration should be given to installing
flood gates that can be closed relatively quickly
across Marsden Parade to prevent the backwater
inundation from the Bremer River. When the flood
gates are closed, the rail embankment would act
as a temporary dam wall and prevent flooding of
low-lying land, being the Ipswich CBD. The rail
embankment is approximately eight metres high
and overtopped by 2% (1 in 50) AEP floods. The
integrity of the rail embankment to support a
water differential of eight metres with potential
overtopping is unknown, and must be established
before this option is assessed further.
47
Fernvale levee (refer Technical Evidence Report
Section 8.4.2)
A number of properties within Fernvale are
inundated by a 1% (1 in 100) AEP flood and a
larger number of properties are isolated through
flooding of a single access road. A levee located
within an existing road reserve to the immediate
north of the village could prevent floodwaters
from the adjacent rivers deviating into residential
areas and isolating residents, for selected
flood events. Further feasibility investigations
are required to progress flood management at
Fernvale including optimisation of a levee.
Amberley Royal Australia Air Force (RAAF) Base
(refer Technical Evidence Report - Section 8.4.3)
Under present day conditions, low-lying areas
of the RAAF base at Amberley are inundated by
10% (1 in 10) AEP flood levels. For a 1% (1 in
100) AEP event, most of the runway, apron and
hangers are inundated which would significantly
compromise base operations and access. Works
to improve the flood immunity (i.e. up to the 1 in
100 AEP flood level) of the base would include a
ring levee around the operational sections of the
base, including the runway, aprons, taxiways and
instrumentation. Road access works in and out
of the base would also be required, including the
Cunningham Highway. Construction of the Warrill
Creek Dry Flood Mitigation Dam (refer to Strategy
7.1) would achieve critical road immunity for the
RAAF Base. In the absence of the Warrill Creek
Dry Flood Mitigation Dam, a ring levee may have
impacts on downstream properties which would
need to be considered through further feasibility
assessments. This option requires further
investigation to understand the practicality of the
solution and any potential impacts.
Goodna Major Centre (refer Technical Evidence
Report Section 8.4.5)
During 2011, Brisbane River floods impacted large
areas within Goodna, including the CBD. There
is potential for the Goodna CBD to be protected
from Brisbane River floods up to about a 1% (1 in
100) AEP level through the installation of a flood
wall levee along the Ipswich Motorway. This may
prevent overtopping of the motorway, as occurred
in 2011, as well as closure of the motorway
underpass roadway via a very large flood gate
structure. The feasibility and practicality of this
solution requires further assessment.
48
Brisbane River Strategic Floodplain Management Plan
Desired outcome 8
Landscape management across
the catchment contributes to
flood risk reduction
Landscape management is discussed in detail
in Chapter 7 of the Technical Evidence Report.
Landscape management actions such as targeted
catchment and riparian revegetation, rural
landscape management practices and water
sensitive urban design can be effective tools that
contribute to enhanced floodplain management
particularly in terms of improving resilience to
the damaging effects of floods. At the same time,
due to the importance of the timing of flows
from the major tributaries in the Brisbane River,
landscape management could have an adverse
impact on flood behaviour.
Sustainable management of natural and built
landscape provides environmental, social
and economic benefits to the community.
The Department of Environment and Science
undertook a scientific review about the affect
natural landscapes can have on flooding in the
report ‘Natural Assets for Flood and Cyclone
Resilience – Synthesis of scientific evidence on the
role of natural assets to reduce the human impacts
of floods and cyclones’ (DEHP, 2012). The report
found that while ‘there is a clear link between
vegetation clearing and an increase in rainfall
runoff … vegetation is not likely to noticeably
affect extreme flood events but has the potential to
reduce local runoff and small-scale floods.’
In addition, landscape management can have
significant benefits to ecosystem health and
habitat, a reduction in landscape salinity,
improved groundwater recharge and a reduction
in erosive capacity.
This Strategic Plan aims to recognise and support
the significant amount of landscape management
activities already underway. Projects within the
catchment incorporating landscape management
options include:
• Resilient Rivers Initiative Catchment Action
Plans identify priority actions based on an
integrated catchment risk assessment of
each catchment and includes strategies
to improve the health of waterways within
South East Queensland.
• Sapling Pocket Floodplain Stabilisation
Project (Ipswich City Council and Seqwater)
investigates landscape management
activities to stabilise riverbanks, improve
water quality and reduce water treatments
costs.
• The Big Flood Project (ARC, 2016) identifies
priority locations for riparian restoration.
• Catchment Stories (compiled by DEHP,
2015) investigates the complexity of
catchments throughout Queensland
including water flow, geology, topography,
rainfall and runoff, natural features and
human modification.
Healthy catchments are fundamental in
supporting our regional economy and provide
social and recreational benefits for the
community. Considering landscape management
options in combination with other floodplain
management activities will provide a holistic and
integrated approach to flood risk management
for the Brisbane River floodplain.
Outcome 8 will be achieved through the
following key strategies.
49
Strategy 8.1 – Catchment wide research into
the effect of landscape management actions
on flood behaviour
Currently, it is not possible to quantify the effects
landscape management actions have on flood
behaviour. This means it is not possible to model
the impacts these actions have on flood hydrology
and subsequently it becomes difficult to assess
these options for flood mitigation purposes.
Physical testing is required to understand on-the-
ground impacts that different types of vegetation
and other landscape management activities have
on flood hydrology. This will create the necessary
link between revegetation practices and changes
in flood behaviour, which can then inform the
most appropriate location and scale of landscape
management options in order to achieve the
desired outcomes.
Strategy 8.2 – Stakeholders continue
to collaborate and identify landscape
management opportunities in the catchment
A number of planned and ongoing catchment
management initiatives are currently underway
within the wider Brisbane River Catchment. These
initiatives, such as catchment revegetation, rural
landscape management practices and water
sensitive urban design, each have the potential
to make a contribution to improving flood
management outcomes, particularly for smaller
floods where these initiatives help to slow
catchment runoff and reduce flood peaks.
Considering landscape management options in
future floodplain management studies and plans
will continue to support current projects looking
at landscape management opportunities such
as the Big Flood Project (ARC, 2016) and the
Catchment Action Plans (RRI, 2016 a,b).
Strategy 8.3 – Recognise benefits in
addition to flood mitigation when assessing
landscape management opportunities
Landscape management opportunities have the
potential to provide flood mitigation benefits
for small-scale flood events. However, where
these activities may have significant benefit
is in improving ecosystem health including
by reducing salinity, improving water quality,
increasing habitat and reducing in soil erosion.
Stakeholders will consider and where possible,
endeavour to quantify these benefits, supported
by the work currently under development through
the Land Restoration Fund (DES) to establish a
co-benefit valuation method.
50
Brisbane River Strategic Floodplain Management Plan
Queensland’s disaster management
arrangements encompass a multi-tiered system
of committees and coordination centres at state,
district and local levels, as shown in Figure 17.
Local Disaster Management Groups are
coordinated at the local government level. Within
the Brisbane River floodplain, Local Disaster
Management Groups exist for the four local
government areas of Brisbane, Ipswich, Somerset
and the Lockyer Valley.
District Disaster Management Groups tend to
encompass multiple local government areas.
Three disaster districts are located within the
Brisbane River floodplain. Disaster Districts
and Local Disaster Management Groups are
based on administrative boundaries and as they
address all hazards do not necessarily align with
catchment boundaries related to flood hazards.
Disaster management is most effective at the
local level when it is tailored to local conditions,
risks and communities. However, when floods
become too large for local governments to
manage on their own, additional support may
be provided by other government areas at the
district or state level. Queensland’s disaster
management arrangements enable a progressive
escalation of support and assistance through
four tiers as required (refer Figure 17). These
arrangements comprise several key management
and coordination structures for achieving
effective disaster management in Queensland.
During a flood, resources can be limited and any
unnecessary inefficiencies in communication and
response systems can have critical impacts on
community safety.
Effective disaster management also relies on
an appropriate community response to flood
warnings and evacuation notices. With increased
reliance on delivering critical information through
online channels such as social media, disaster
managers need to ensure the community is
receiving consistent messages from all sources.
Outcome 9 will be achieved through the
following key strategies.
Desired outcome 9
Disaster management planning
and response applies a regionally
consistent approach whilst
recognising local flood risks
Disaster Management is detailed in Chapter
10 of the Technical Evidence Report. Disaster
management is a unique combination of
advance planning and real-time decision making.
Managing flood disasters relies on a sound
understanding of flood behaviour, the nature of
communities at risk and the potential for flooding
to be worse than previously experienced. This
understanding is built upon past experience and
information derived from the hydrologic and
hydraulic models, intersected with flood exposure
data, which is interpreted to local conditions.
While there are key response agencies across
government with responsibility for disaster
management planning, effective disaster
management requires input and action from
the entire community. Critical to the success of
disaster management is information sharing
between agencies and engagement of the
community to empower them to understand
and respond to flood emergency warnings. The
disaster management outcome in this Strategic
Plan aligns closely with those of community
awareness and resilience.
51
Strategy 9.1 – Regional-scale flood analysis
and consequence information is shared and
maintained across all agencies
A range of digital data has been developed for this
Strategic Plan as described in Section 10.3 of the
Technical Evidence Report. This information and
analysis builds on the regional-scale flood model
to expand the suite of tools all stakeholders can
use to inform disaster management planning and
response. The data includes:
• analysis of major road network flood
immunity that identifies low points in the
road network and provides inundation
timings for a range of flood AEPs
• assessment of flood exposure and
isolation risk for residents, properties, and
sensitive and critical infrastructure
• provision of catchment-wide ‘time-to-
inundation’ mapping
• analysis of available flood data at forecast
stream gauge locations to identify data
gaps, as well as advice about how to fill
the gaps with sufficient data to improve
disaster management applications.
There is an opportunity for disaster managers
in the Brisbane River Catchment to continue to
build on the outputs of this Strategic Plan to
develop a ‘world class’ data-driven solution to
flood management in the region.
Strategy 9.2 – Disaster management
analysis informs community awareness and
resilience building with property-scale flood
risk information
Personalised and localised information is essential
for community directed emergency planning and
resilience. This includes providing the community
with the information they need to plan for flooding
and act on real-time and forecast information
during floods. Information and data developed
for this Strategic Plan is described in Sections
10.3 to 10.5 of the Technical Evidence Report, and
supports the development of community resilience
through the following information:
• A surveyed property database for the
Brisbane River floodplain that includes
information about ground level, building
level, property type, image and address,
as well as a range of flood risk information
including flood depth-at-ground for a range
of flood sizes.
Figure 18 – Queensland Disaster Management arrangements (source: www.disaster.qld.gov.au)
52
Brisbane River Strategic Floodplain Management Plan
• Identification of floodplain ‘zones’ for
each stream gauge, which the Bureau uses
to report actual and forecast flood levels.
These zones would support emergency
managers and help the community to
understand what stream gauges should
be reviewed when seeking real-time and
flood forecast information relevant to their
location or property (i.e. their ‘reference’
gauge).
• Information relating property levels to the
reference stream gauge that will enable
emergency managers and the community
to better understand how actual and
forecast stream gauge flood levels relate to
their property. For example, ‘my house will
likely become flooded when my reference
stream gauge reaches between 4.2 metres
and 4.5 metres AHD’.
Strategy 9.3 – Regionally consistent
communication supports disaster
management operations with consistent
language and messaging
The community works, lives and travels
throughout the catchment (and beyond) on a
daily basis and is therefore exposed to flood
awareness and warning messaging issued
by a range of local governments and entities
(especially the media). Inconsistent language
and messaging may introduce confusion and
result in poor uptake of the messages and alerts.
Guidelines for a consistent approach to
communication and engagement across the
floodplain, building on the work being developed
by the Bushfire and Natural Hazard Cooperative
Research Centre titled ‘Effective risk and warning
communication during natural hazards’, will
support regionally consistent language and
messaging. This includes areas of flood warning,
local interpretation of warnings and forecasts
provided by the Bureau.
53
A series of actions are outlined in the table
below to achieve the flood management desired
outcomes and strategies (Section 3) of this
Strategic Plan. The actions have been developed
from a flood risk management perspective and
are subject to standard agency prioritisation
and funding processes prior to commitment for
implementation.
The actions take into account the constraints
and opportunities relevant for the Brisbane
River based on an understanding of current and
future flood risks and an appreciation of existing
Actions supporting improved flood
risk management in the Brisbane
River floodplain
knowledge, resources and capabilities across
the communities and stakeholders that have an
interest in the Brisbane River floodplain.
The tables include links to the relevant outcomes
and strategies in this Strategic Plan, as well as
the more detailed discussions in the Technical
Evidence Report.
Refer to Appendix B for list of acronyms including
Queensland Government departments.
4.1 General floodplain management actions
ID Relevant
strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
FM1.1
1.1
1.2
1.3
3.4
13.1
Establish suitable
governance arrangements
Strategic Plan and the
development of the Local
Floodplain Management
Plans.
Regional QRA High
FM1.2
1.1
1.2
1.3
10.7.2.1
11.6.3.1
13.1
Investigate opportunities
and mechanisms for
ongoing resource and
knowledge sharing.
Regional QRA Medium
FM2
1.1
1.2
1.3
13.1 Review this Strategic
Plan every five years (or
in response to relevant
triggers) including
updates of significance to
regional models.
Regional QRA Medium
54
Brisbane River Strategic Floodplain Management Plan
ID Relevant
strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
FM3
1.1
1.2
1.3
2.1
1.2
5.1
5.2
5.3
9.5.1
13.8
Develop Local Floodplain
Management Plans
based on the findings,
outcomes, strategies and
approaches identified in
this Strategic Plan.
Local Local
governments
High
FM4.1
1.1
1.2
1.3
6.10.2
10.7.2.4
13.2
Pre-plan collection
of post event data
including requirements,
specifications,
approaches, and
the development of
templates.
Regional QRA Medium
FM4.2
1.1
1.2
1.3
6.10.2
10.7.2.4 13.2
Coordinate and
collaborate with the
insurance industry,
QFES, QRA, Geoscience
Australia and universities
to collect standardised
post event data.
Regional QRA Medium
FM5
1.1
1.2
1.3
8.11.1
13.1
Establish a state policy
on the assessment,
prioritisation and funding
of state-funded flood
mitigation works.
State QRA High
FM6
1.1
1.2
1.3
9.2.3
11.2.4 11.5.7
13.2
Collaborate with the
insurance industry
to share the most
current floodplain risk
management information.
State DNRME Medium
FM7
1.1
1.2
1.3
6.7
13.1
Extend the economic
framework established
in this Strategic Plan and
Technical Evidence Report
to include community
awareness and resilience,
disaster management and
land use planning.
Regional QRA Medium
FM8
3.1 5.2
5.3.2
13.1
Use the climate change
sensitivity analysis
approach applied in this
Strategic Plan to support
the implementation
of actions and the
development of Local
Floodplain Management
Plans.
Regional All relevant lead
agencies
High
55
ID Relevant
strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
FM9
3.1 9.6
13.5
Local Floodplain
Management Plans to
identify ‘no regrets’
actions to improve
resilience to climate
change related flood risks
now and into the future.
Local Local
governments
High
FM10.1
3.1 5.2
13.8.3
Ongoing monitoring of
climate change research,
science and modelling
advances.
Regional DES High
FM10.2
13.1
13.8.3
Findings from FM10.1
should be considered and
incorporated into future
reviews of this Strategic
Plan and Local Floodplain
Management Plans.
Regional and local State and local
governments
High
FM11
3.2 5.2.1
13.1
Coordinate and link in
with existing climate
change adaptation
planning processes
across state and local
governments, ensuring
a holistic response
to climate change for
the Brisbane River
Catchment.
Regional DES Medium
FM12.1
9.1 10.7.2.3
13.6
Coordinate an
assessment of regional
evacuation capability
with support from LDMGs,
DDMGs, DTMR, QFES, QRA
and DSDMIP.
Regional and local QPS High
FM12.2
9.1 10.7.2.3
13.6
Findings from FM12.1
should inform any works
required to upgrade
local evacuation route
networks for safe
evacuation of local
communities or escalate
as required (for state-
controlled routes).
Regional Local
governments
High
FM12.3
Develop state guidelines
to support the
identification of ‘fair and
reasonable’ immunity for
evacuation routes.
Regional DTMR High
56
Brisbane River Strategic Floodplain Management Plan
4.2 Structural / Infrastructure (SO) actions
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
SO1.1
7.1 8.1.8.2
8.11.1
13.4
Wivenhoe and Somerset
Dam upgrades and
operations
Review and incorporate
relevant findings of
the Brisbane River
Catchment Flood Studies
into ongoing planning
and investigations for
upgrades to the Somerset
and Wivenhoe dams.
Regional Seqwater High
SO1.2
7.1 8.1.8.2
8.11.1
13.4
Wivenhoe and Somerset
Dam upgrades and
operations
Upon completion of
SO1.1, DNRME to
consider the incremental
costs of any dam upgrade
works associated with
flood mitigation benefit
compared to options
to increase operational
release rates through
downstream land
rezoning or buy-back.
Regional DNRME Medium
SO2
7.1 8.6.2
8.11.1
13.4
Warrill Creek dry flood
mitigation dam
Undertake a feasibility
study for a dry flood
mitigation dam at the
Southern Freight Railway
crossing of Warrill Creek.
Regional DNRME High
SO3
7.1 8.6.1
8.11.2
13.4
Upper catchment dry
flood mitigation dams
Investigate potential
for other locations for
regional-scale dry flood
mitigation dams at new
floodplain crossings of
the Southern Freight
Railway or other major
linear infrastructure. Any
potential locations to
be referred to the state
for consideration in
conjunction with SO2.
Regional ICC
LVRC
High
57
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
SO4
7.2 8.5.2
8.5.3
8.11.1
13.4
Brisbane CBD / South
Brisbane temporary
barriers
Undertake a feasibility
study into temporary
barriers in the Brisbane
CBD and South Brisbane
as part of the Brisbane
Local Floodplain
Management Plan.
Local BCC Medium
SO5
7.2 8.4.6
8.11.1
13.4
Ipswich CBD flood gate
Undertake a feasibility
study for a flood gate
at Marsden Parade as
part of the Ipswich Local
Floodplain Management
Plan.
Local ICC Medium
SO6
7.2 8.4.2
8.11.1
13.4
Fernvale levee
Undertake a local options
assessment for the
Fernvale levee as part
of the Somerset Local
Floodplain Management
Plan.
Local SRC High
SO7
7.2 8.4.5
8.11.1
13.4
Goodna CBD levee
Undertake a local options
assessment for the
Goodna CBD levee as
part of the Ipswich Local
Floodplain Management
Plan.
Local ICC Low
SO8
7.2 8.4.3
8.11.1
13.4
Amberley levee
Consult with the
Department of Defence
regarding a levee for the
Amberley RAAF Air Base.
Regional DSDMIP Medium
58
Brisbane River Strategic Floodplain Management Plan
4.3 Disaster management (DM) actions
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
DM1
9.1 10.7.2.1
13.6
Relevant LDMGs and
DDMGs consider the
information provided by
this project in developing
practices to address
cross-boundary and
cross-district implications
for preparation, planning,
response and recovery
arrangements across the
Brisbane River region.
Regional LDMGs
DDMGs
High
DM2
9.1 10.7.2.4
13.6
Recognise and use
the existing disaster
management
arrangements for
information requests.
Regional All Disaster
Management
stakeholders
Medium
DM3.1
9.1 10.7.2.5
13.6
Identify (rainfall and
stream) gauges to be
included in the Bureau’s
forecast network based
on the Queensland Flood
Gauge Network Review.
Local Local
governments
High
DM3.2
9.1 10.7.3.4
13.6
Review stream gauge
classifications and amend
where necessary.
Local Local
governments
Medium
DM4.1
9.1
9.2
9.3
10.7.3.2
13.6
Develop a disaster data
information framework to
provide all stakeholders
with access to consistent
and up-to-date disaster
data for the region.
Regional QFES Medium
DM4.2
1.3
9.1
9.2
9.3
10.6
13.6
Lead discussions with
the Bureau to develop
a real-time regional
hydraulic modelling
system and incorporate
outputs into a regional
flood intelligence system
to share information.
Regional QRA High
59
4.4 Land use planning (LU) actions
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
LU1
5.2 9.5.4.2
13.5
Coordinate a floodplain-scale
cumulative impact assessment to
inform decisions relating to regional
and local infrastructure and land
use planning in the Brisbane River
floodplain.
Regional QRA High
LU2.1
5.1 9.5.1
13.5
Align the scope of local flood risk
assessments undertaken within the
Local Floodplain Management Plans
with the SPP requirements.
Local Local
governments
High
LU2.2
2.1
3.1
5.2
5.3
9.6
13.5
Incorporate the following actions into
Local Floodplain Management plans
to ensure regional consistency:
• assessment of ‘potential hydraulic
risk’ in line with the approach
undertaken to inform this Strategic
Plan.
• consideration of local and
regional evacuation capability and
evacuation networks (within a
risk/hazard framework).
• consideration of findings from the
cumulative impact assessment
(LU1).
• Consider climate change scenario
RCP8.5 in informing land use
planning within the floodplain
where there is potential for
significant ramifications and/
or limited scope for mitigation.
Where land use longevity or
resilience to increasing flood
risk warrants, a range of other
climate change scenarios may be
appropriately applied.
• Consider vulnerable land uses
involving vulnerable people in
higher flood risk circumstance
across the full known extent of the
floodplain.
Local LGAs High
LU2.3
5.4 13.5 Consider the outcomes of this
Strategic Plan and the Local
Floodplain Management Plans when
amending local planning instruments
(noting that any amendments
identified would occur following
Phase Four of the Flood Studies).
Local Local
governments
EDQ
High
60
Brisbane River Strategic Floodplain Management Plan
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
LU3.1
5.4 13.5 Consider relevant land use planning
related findings from the Local
Floodplain Management Plans,
in accordance with the SPP and
ShapingSEQ state interest policy
requirements, when undertaking
state interest review of local
planning instruments.
Regional DSDMIP Medium
LU3.2
5.4 9.5.6
13.5
As part of reviewing Local
Floodplain Management Plans
and any proposed local planning
scheme amendments, investigate
implications of flood risk for regional
land use, land supply and outcomes
under ShapingSEQ.
Regional DSDMIP High
4.5 Community awareness and resilience (CAR) actions
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
CAR1
4.3 11.6.3.1
13.7
Work with local governments to
establish or utilise an existing
community awareness and
resilience working group to
facilitate coordinated awareness
and resilience activities within the
Brisbane River floodplain.
Regional QRA High
CAR2.1
4.1
4.2
4.3
11.6.3 13.7 Develop regional reference material
including a compendium of current
activities and learnings, toolkit
of activities and guidelines for
communication and engagement.
Regional QRA High
CAR2.2
4.3 11.6.5
13.7
Evaluate community awareness
and resilience activities relating
to flood, and share learnings from
the evaluation to inform continual
improvement in suitability and
effectiveness.
Regional IGEM Medium
CAR2.3
4.1
4.2
4.3
9.2
9.3
11.6.3
13.7
In strong collaboration with local
governments, develop regional
guidance for delivering consistency
in local provision of online flood
awareness mapping, property-scale
flood information, place-based
installations, and community facing
language and messaging.
Regional QRA High
61
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
CAR3
4.1
4.3
11.6.4.8
13.7
Support, identify and upskill
community leaders as part of a
community led program to assist
with disseminating information,
resilience planning and activities,
and communication of local
conditions.
Local Local
governments
Low
4.6 Landscape management (LM) actions
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
LM1
8.2 7.5
13.3
Coordinate and share
landscape management
information within a
consistent regional
framework.
Regional DNRME High
LM2
8.1 7.5
13.3
In collaboration with local
governments, coordinate,
conduct and share
landscape management
research, in particular
broad scale revegetation
and catchment hydrology.
Regional DES Medium
LM3
8.1 7.5
13.3
Undertake local
geomorphological studies
to identify key catchment
processes and issues,
and assess current
conditions and pressures.
Local DES Medium
LM4
8.1
8.3
7.5
13.3
Using the outcomes from
LM2, update hydrology
and hydraulic modelling
to reflect research
results and prioritise
locations for landscape
management within the
catchment.
Local DES Medium
LM5
8.2
8.3
7.5
13.3
Update catchment and
receiving water quality
modelling to estimate
other (non-flood) benefits
to waterways.
Regional DNRME Medium
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Brisbane River Strategic Floodplain Management Plan
4.7 Building design and construction (BC) actions
ID Relevant
Strategies in
the Strategic
Plan
Technical
Evidence
Report page
references
Description Implementation Lead agency Priority
BC1
6.1
6.2
12.3 Consider the
development of a
working group to
manage future updates
and amendments to
the resilient building
materials database.
Regional HPW Medium
BC2
6.1
6.2
12.3 Investigate arrangements
that allow resilient design
to be considered as a
flood risk management
measure.
Regional HPW Medium
BC3
6.1
6.2
12.3 Consider creation of a
development guideline
similar to MP3.5 to
provide a standard for
construction of buildings
in ‘flood resilient areas’.
Regional HPW Medium
BC4
6.1
6.2
12.3 Provide feedback
to the Australian
Building Codes Board
to include guidance
on the principles
and performance
requirements of flood
resilient materials.
Regional HPW Medium
4.8 Local Floodplain Management Plans
Preparation of the Local Floodplain Management Plans by the four local governments in the floodplain,
represents the fourth and final phase of the Brisbane River Flood Studies. The Local Floodplain
Management Plans will provide a more detailed level of assessment of flood risks and floodplain
management responses to address community specific issues and opportunities.
Guidance for local governments in preparing Local Floodplain Management Plans has been provided
in Section 13.8 of the Technical Evidence Report. Funding support has been made available to all four
local governments as part of the 2017-18 Natural Disaster Resilience Program.
63
The
Queensland Strategy for Disaster Resilience
(QSDR) and
Strategic Policy Framework for
Riverine Flood Risk Management and Community
Resilience
(SPF) sets the key objectives, guiding
principles and implementation framework for
flood risk management and resilience activities
in Queensland.
These key policies provide context for the
implementation and monitoring of this Strategic
Plan through the principles of catchment-
scale collaboration, shared responsibility,
multi-disciplinary approaches, and locally-led
implementation.
As the lead agency responsible for disaster
recovery, resilience and mitigation policy in
Queensland, QRA has a strong interest in
ensuring the flood risk management initiatives
and actions under this Strategic Plan draw from
and achieve the objectives of these policies
to help make Queensland the most disaster
resilient state in Australia.
Implementation and monitoring
arrangements
Key to the successful implementation of this
Strategic Plan is the ongoing commitment of
the four local governments and state agencies
to provide updates on the progress of future
actions, and to ensure alignment with the
outcomes, strategies and actions identified
in this Strategic Plan. This will require local
governments and state agencies to continue to
work together to discuss and resolve issues and
opportunities that may arise. The project partners
are committed to working together and will
continue to convene on a regular basis as part of
the overall monitoring and reporting of actions
and outcomes of this Strategic Plan.
QRA will play a support and coordination role to
maintain the collaborative approach required for
ongoing implementation of this Strategic Plan.
It will ensure alignment with various policies,
plans and activities that this Strategic Plan
interfaces with such as ShapingSEQ, and other
disaster resilience policies and projects. QRA will
also provide a reporting function to Queensland
Government on the progress of implementation
of this Strategic Plan.
Consistent with the intent of the QSDR and SPF,
QRA will also play a regional-scale coordination
and facilitation role to support catchment-scale
collaboration between partners. QRA will Chair
half-yearly stakeholder meetings with partners to
monitor the progress of the recommendations,
and facilitate ongoing lines of communication.
These meetings will provide an opportunity for
stakeholders to formally update one another
on the development of Local Floodplain
Management Plans being delivered as the final
phase of the project.
64
Brisbane River Strategic Floodplain Management Plan
Appendices
Appendix A – Glossary of terms
All-hazards approach This approach assumes that the functions and activities applicable
to one hazard are most likely applicable to a range of hazards
and consequently planning captures the functions and activities
applicable to all hazards.
Annual Exceedance Probability The chance that a flood will reach or exceed a particular level in any
given year. For example a 1% (1 in 100) AEP.
Average Annual Damage The cost incurred by flooding on an annual basis for a nominated
development situation, when averaged over an extended period of
time. This takes account of the probability of smaller more frequent
floods, as well as very rare but catastrophic floods.
Backflow prevention device Structures installed within stormwater systems (usually at the
downstream end) that prevents backflow of elevated river levels into
the stormwater pipes (and hence inundation of lands that are lower
than the natural riverbank). Backflow prevention devices have been
installed at a number of locations around Brisbane since 2011.
Catchment Action Plan Strategic documents outlining action and initiatives targeting works
across a whole-of-catchment. A number of catchment action plans
have been developed for parts of the Brisbane River catchment by
the Resilient Rivers Initiative.
Community resilience A community’s ability to rapidly accommodate and recover from
the impacts of hazards, restore essential structures and desired
functionality, and adapt to new circumstances. Community resilience
is closely linked to the awareness of the community regarding
flooding and the potential for impacts and damages from different
sizes of events.
Brisbane River Catchment
Flood Studies
The full package of investigations of the Brisbane River carried
out on behalf of the Queensland Government since 2013 covering
data collection, hydrological and hydraulic modelling, the Strategic
Floodplain Management Plan and Local Floodplain Management
Plans.
Exposure The land use and population that exists within the floodplain, and
hence is exposed to flood hazards.
Filling of land An increase in ground level to elevate the land in an attempt to
reduce the frequency of flood inundation. Filling of land within
sensitive parts of a floodplain, such as flood conveyance areas, may
worsen flood conditions elsewhere.
Flood conveyance Where the vast majority of flood water flows through a floodplain,
and is typically deep and fast flowing during big flood events. Even
partial blockage of flood conveyance areas would likely cause
significant redistribution of flood flow, or significant increase in
flood levels.
65
Flood fringe Parts of the floodplain that are farthest from the main river channel
and flood conveyance areas. It is the remainder of the floodplain
once flood conveyance and flood storage areas have been defined.
Removal of flood fringe areas from the floodplain would have little
overall impact on flood behaviour.
Flood function Floodplains are differentiated based on flood behaviour or
floodplain function during events. This includes flood conveyance
areas, flood storage areas and flood fringes.
Flood risk management
outcomes
The desired outcomes achieved through delivering the strategies
and recommendations of this Strategic Plan in achieving the overall
shared vision for the Brisbane River floodplain.
Flood storage Parts of the floodplain that fill up with floodwaters during a
flood and temporarily detain the floodwaters, thereby slowing
the progress of the flood and potentially lowering peak levels
downstream.
Flood Study Brisbane River Catchment Flood Study (Flood Study), comprising
hydrologic and hydraulic modelling and assessment of the Brisbane
River.
Habitable floor Consistent with Building Code of Australia, Volume 2, Part 1.1, for
residential properties - the habitable floor level should be taken at
the lowest entrance point to the property or the lowest habitable
floor area. Habitable areas are used for normal domestic activities
and;
(a) include a bedroom, living room, lounge room, music room,
television room, kitchen, dining room, sewing room, study,
playroom, family room, home theatre and sunroom
(b) exclude a bathroom, laundry, pantry, lobby, clothes drying room,
vehicle parking area or storage.
For other land uses, a habitable area refers to that used for offices
or to store valuable possessions susceptible to flood damage in the
event of a flood.
Hydraulic behaviour Where and how flood waters flow across a floodplain. This includes
flood depths, levels, velocities and flows.
Hydraulic Risk / Potential
Hydraulic Risk
A combination of the likelihood of a flood event and the hazard
level occurring. This is defined over a broad spectrum of likelihoods
and hazards via a two-dimensional risk matrix. This represents the
flood risk independent of use or occupancy of the land. Refer to
Appendix C for further information.
Hydrologic and hydraulic
models
Computer modelling of rainfall and surface runoff to simulate real
world flood conditions and therefore estimate likely flood extents
and flood behaviour for theoretical future conditions and events.
These models are calibrated to historical events to ensure they
provide an adequate representation of actual conditions.
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Brisbane River Strategic Floodplain Management Plan
Integrated catchment planning
/ management
Integrated Catchment Management (ICM) is a well recognised
practice that aims to improve and integrate the management of
land, water and related biological resources in order to achieve
the sustainable and balanced use of these resources. Integrated
Catchment Planning is a term used in the context of this Strategic
Plan to describe holistic multi-disciplinary planning, consideration
of other planning activities in the local context, and identification of
mutually beneficial outcomes.
Landscape management Includes land-based activities such as targeted catchment and
riparian revegetation, rural land management practices and Water
Sensitive Urban Design.
Localised flooding / overland
flow
Flooding generated from rainfall occurring over a local area only.
Localised flooding is concentrated in small creeks and ephemeral
waterways, while overland flow is the surface runoff following
rainfall, concentrated in natural lower lying areas and swales across
the landscape. Flooding is usually ‘flashy’ with peaks occurring
shortly after rainfall.
‘no worsening’ of flood risk Development including filling and land form change, when assessed
against the full range of flood event AEP’s outlined this Strategic Plan:
• does not result in an increase in flood hazard conditions
(flood levels, flood velocities, evacuation conditions and
capability, flood hazard categories and potential hydraulic risk
categories) for surrounding properties
• does not increase the level of flood risk of surrounding
properties
• does not result in a total impact from cumulative filling across
the floodplain of greater than 10mm
• does not alter the flood hydrographs, and timing of the flood
wave/s
• does not impact on flood warning times.
Queensland Emergency Risk
Management Framework
A new framework developed in 2017 by QFES, for assessment and
management of risks from natural hazards.
Re-engaging floodplain Removal of artificial structures within a floodplain that create a
barrier to the natural flow of waters across a floodplain. This could
include levees, road embankments and flood gates.
Reference gauge The flood gauge that is used by flood warning authorities to
announce predicted flood levels for a general locality.
Regionally consistent
approaches and understanding
The same methods, definitions and terms used to assess and
describe flooding across the region. This applies to consistent
definition and consideration of hydraulic behaviour, flood damages,
land use planning, disaster management requirements, language
and messaging to the community and stakeholders.
Relative time to inundation
mapping
Mapping of relative time to inundation (> 0.3m) for properties
exposed to inundation once the flood level at the reference gauge
exceeds the minor flood level.
67
Risk-based land use planning The principle of land use allocation based on ensuring that only uses
appropriate to the level of risk are placed on that land.
Riverine flooding Flooding within large river systems where floods increase and break
out of the riverbanks to inundate adjacent floodplains. Flooding is
generated from rainfall across the broad catchment area. It may take
many hours, or even days, for peak flood levels to occur as rainfall
slowly drains from the catchment.
ShapingSEQ Queensland Government’s Regional Plan for South East Queensland
(2017).
Tangible damages / intangible
damages
Tangible damages are flood damages that can be measured in
economic terms such as financial loss. Intangible damages cannot
be directly linked to financial measures and include impacts such as
stress and anxiety, as well as loss of life.
Technical Evidence Report The Technical Evidence Report that supports this Strategic Plan.
The Technical Evidence Report was developed over the course of 18
months as a series of milestone reports covering key work packages
of the floodplain management assessment process.
Temporary flood barriers Artificial walls that are temporarily erected to prevent inundation of
flood waters into some sections of a floodplain. These can include
interlocking vertical or inclined panels or flexible water-filled tubes.
Tolerability Tolerability is the community’s readiness to bear the risk of flooding,
after risk treatment. Risk tolerance can be influenced by legal or
regulatory requirements, as well a community’s awareness and
experience of floods, knowledge of previous flooding history,
what type of uses are exposed, extent of social and community
cohesiveness. A range of demographic and socio-economic
characteristics of a community may also affect current and future
community views on flood risk.
Vulnerability A measure of the sensitivity of the land use and/or population
exposed to flooding. Vulnerability can relate to physical, socio-
economic, mobility or flood-awareness factors.
Whole-of-catchment approach Consideration of processes and interactions occurring throughout
the whole Brisbane River Catchment, rather than just in discrete
locations, such as within local government boundaries. Natural
processes do not recognise governance boundaries, so management
of land, water and environmental values needs to occur on a more
holistic catchment scale.
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Brisbane River Strategic Floodplain Management Plan
Appendix B – Acronyms and abbreviations
AAD Average Annual Damage
AEP Annual Exceedance Probability
ARR Australian Rainfall and Runoff
Bureau Bureau of Meteorology
BCC Brisbane City Council
CAP Catchment Action Plan
CSIRO Commonwealth Scientific Investigation Research Organisation
DES / EHP Department of Environment and Science (replacing Environment and Heritage Protection)
DEWS Department of Energy and Water Supply
DLG Department of Local Government
DNRME Department of Natural Resources, Mines and Energy
DSDMIP Department of State Development, Manufacturing, Infrastructure and Planning
EDQ Economic Development Queensland
HLW Healthy Land and Water
DHPW Department of Housing and Public Works
HR (Potential) Hydraulic Risk
ICC Ipswich City Council
IGEM Inspector General of Emergency Management
IPCC Inter-governmental Panel on Climate Change
LFMP Phase 4 (Local Floodplain Management Plan)
LVRC Lockyer Valley Regional Council
QAO Queensland Audit Office
Q-CAS Queensland Climate Adaptation Strategy
QERMF Queensland Emergency Risk Management Framework
SEQ South East Queensland
QFCoI Queensland Floods Commission of Inquiry
QFES Queensland Fire and Emergency Services
QRA Queensland Reconstruction Authority
RCP Relative Concentration Pathway (8.5 or 4.5)
SFMP Phase 3 (Strategic Floodplain Management Plan) (this Strategic Plan)
SPP State Planning Policy
SRC Somerset Regional Council
TER Technical Evidence Report
WSUD Water Sensitive Urban Design
69
Appendix C – Potential Hydraulic
Risk Matrix
The concept of Potential Hydraulic Risk (HR) is used
throughout this Strategic Plan to represent the
hydraulic behaviour of floods and their likelihood
of occurring in the Brisbane River floodplain.
Potential Hydraulic Risk is one of the inputs
used to determine overall flood risk from riverine
flooding. It represents the risk resulting from the
flood conditions (likelihood of the flood occurring,
and the depths and velocities of the floodwaters)
independent of the actual use or development of
the land within the floodplain.
Flood risk considers a range of factors in addition
to potential hydraulic risk and is best suited to be
determined at the local level to reflect local context.
It does not replace local government risk mapping
and is not comparable to local government risk
categorisations.
Potential Hydraulic Risk has been derived through
consideration of different flood event likelihoods,
and the corresponding depths and velocities across
the floodplain.
Consideration was given to a wide range of flood
likelihoods, from the more frequent to the very rare
events. Seven flood likelihoods are incorporated
into the Potential Hydraulic Risk matrix developed
for the Brisbane River catchment, namely:
• 1 in 10 AEP
• 1 in 20 AEP
• 1 in 50 AEP
• 1 in 100 AEP
• 1 in 500 AEP
• 1 in 2000 AEP
• 1 in 100,000 AEP
For each flood event, the floodwaters have also
been classified based on their ‘flood hazard’. This
is determined by considering the flood depth and
flood velocity in combination, as recommended
by AIDR Guideline 7-3, Flood Hazard - Supporting
document for the implementation of Australian
Disaster Resilience Handbook 7 Managing the
Floodplain: A Guide to Best Practice in Flood
Risk Management in Australia (AIDR, 2017). This
results in six classifications of flood hazard for
each flood likelihood:
• H1 – generally safe for people, vehicles
and buildings.
• H2 – unsafe for small vehicles.
• H3 – unsafe for vehicles, children and the
elderly.
• H4 – unsafe for people and vehicles.
• H5 – unsafe for vehicles and people. All
buildings vulnerable to structural damage.
Some less robust building types vulnerable
to failure.
• H6 – unsafe for vehicles and people. All
building types considered vulnerable to
failure.
The Potential Hydraulic Risk has been determined
by grouping flood likelihoods and hazards in to
five bands of similar and relative ‘risk’, ranging
from HR1 (highest potential risk) to HR5 (lowest
potential risk). These potential hydraulic risk
bands have been derived using the established
risk matrix approach based on the combination
of likelihood and hazard as described above. A
gradation of potential hydraulic risk is captured
across both increasing flood likelihood and
increasing hazard categories. For example,
combinations of low likelihood, such as a 0.001%
(1 in 100,000) AEP event, and low consequence
70
Brisbane River Strategic Floodplain Management Plan
produce the lowest potential risk. Whereas,
combinations of high likelihood, such as a 10% (1
in 10) AEP event, and high consequence produce
the highest potential risk. Areas of the floodplain
that are subject to other combinations of likelihood
and hazard are considered to experience potential
hydraulic risk across the full spectrum of risk
between these two extremes.
For any given likelihood, the potential hydraulic
risk becomes greater as the hazard increases.
For a 10% (1 in 10) AEP event, the potential
hydraulic risk will be higher for areas with higher
hazard levels (e.g. H5 or H6) than areas with
lower hazard areas (e.g. H1). The same applies
for a given hazard category, as the likelihood of
flooding increases the potential hydraulic risk will
also increase.
The potential hydraulic risk does not increase
in equal increments as the level of hazard and
likelihood increase. Consideration should be
given to the level of consequence associated
with different hazard and likelihood categories.
Hazard categories of H3 to H6 represent areas
of the floodplain that pose a serious threat to
people’s lives and therefore the level of potential
hydraulic risk in these areas should be considered
more significant. Similarly, areas of the floodplain
that experience frequent flooding will also have a
higher potential hydraulic risk. Conversely, areas
of the floodplain subject to flooding from only
extremely rare events, such as the 0.001% (1
in 100,000) AEP), are considered to have a low
potential hydraulic risk regardless of the level
hazard as the per cent chance of this flood event
occurring in any given year is so remote.
This potential hydraulic risk classification is
further described in Section 4.2. of the TER
and has been represented using a risk matrix
to illustrate the combinations of hazards and
likelihoods resulting in each potential hydraulic
risk band.
This classification is then used to spatially map
the floodplain, grouped by HR category, as shown
in Figure 4-6 in Section 4.2.7 of the TER.
Potential hydraulic risk mapping of the lower
Brisbane River floodplain has the following
limitations:
• It represents flooding from the major
rivers and tributaries only, based on the
design flood events identified in the Flood
Study. The risk mapping does not reflect
flooding from local sub-catchments,
creeks and overland flowpaths, or other
scenarios such as erosion or changes in
geomorphology; and
• It does not take into consideration non-
hydraulic risk factors. A comprehensive
assessment of flood risk (beyond potential
hydraulic risk) should also consider non-
hydraulic flood risk factors, outside of this
Strategic Plan such as:
• land use or development exposure to
flooding
• vulnerability of the community at risk
• specific challenges associated with
evacuation or isolation during flooding
• the community’s tolerability to risk
• risks associated with loss of essential
services during a flood.
Potential hydraulic risk, as defined in this
Strategic Plan, does not represent the total flood
risk and should not be interpreted as such. The
limitations outlined above should be taken into
account when applying this potential hydraulic
risk outside of the parameters of the Strategic
Plan.
71
Appendix D – Reference list
ABCB. 2012a Construction of buildings in flood
hazard areas. Version 2012.2. Australian Building
Codes Board. Available at http://www.hpw.qld.gov.
au/SiteCollectionDocuments/ABCBFloodStandard.
pdf
ABCB. 2012b Construction of buildings in flood
hazard areas – Information Handbook (non
mandatory). Version 2012.3. Australian Building
Codes Board. Available at https://www.abcb.gov.
au/-/media/Files/Resources/Education-Training/
Handbook-Flood-2012.pdf
AIDR. 2017 Managing the Floodplain: A Guide
To Best Practice in Flood Risk Management in
Australia, Handbook 7, Australian Institute of
Disaster Resilience.
Australian Research Council (ARC). 2016 The Big
Flood: When Will it Happen Again. Final Report.
Australian Government ARC Linkage Project (ARC
LP 120200093 2013-2016) available at www.
thebigflood.com.au
Ball, J. et al. 2016. Australian Rainfall and
Runoff [ARR16]: A Guide to Flood Estimation,
Commonwealth of Australia.
Bates, B. et al. 2016 Climate Change
Considerations, Chapter 6 in Book 1 of Australian
Rainfall and Runoff - A Guide to Flood Estimation,
Commonwealth of Australia.
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