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Item 3 Attachment 1
Noosa Shire
Flood
Management
Plan
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DR
“The direction for future
flood management
initiatives in Noosa.”
PO Box 141 Tewantin QLD 4565
P (07) 5329 6500 | F (07) 5329 6501
[email protected]
www.noosa.qld.gov.au
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Full text of the other 41 sections
Section 2
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© Noosa Council 2016
General enquires: 8.30 am – 5.00 pm Monday to Friday (excluding public holidays)
By telephone: (07) 53296500 (including after-hours emergencies)
By email: [email protected]
Fax: (07) 53296501
Street Address: 9 Pelican Street, TEWANTIN
Postal Address: PO Box 141, TEWANTIN QLD 4565
www.noosa.qld.gov.au
Disclaimer
This document has been developed by Noosa Shire Council’s Strategic Planning Unit with input from across Council’s other business units.
Information contained in this document is based on available information at the time of writing. All figures and diagrams are indicative only and
should be referred to as such. This is a strategic document which deals with technical matters in a summary way only. Council or its officers accept
no responsibility for any loss occasioned to any person acting or refraining from acting in reliance upon any material contained in this document.
Acknowledgements
Council wishes to thank all interested stakeholders who have taken the time and energy to help guide the development of this plan. Council would
particularly like to thank HydraLogic for their valued assistance with helping to prepare the plan and background information.
Noosa Council | Flood Management Plan | Page 2
Section 3
Contents Exectuive Summary................................................................................... 5
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1. Introduction................................................................................. 6
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2. Flooding in Noosa........................................................................ 7
3. History of Flooding in Noosa..................................................... 10
4. Flood Management in Noosa..................................................... 13
5. Flood Studies.............................................................................. 15
5.1 Noosa River Catchment Flood Studies........................................................ 15
5.1.1 Noosa River Flood Study ....................................................................................... 15
5.1.2 Emerging Issues and Concerns for the Noosa River .......................................... 16
5.1.3 Noosa Daintree Estate............................................................................................. 17
5.1.4 Ringtail Creek........................................................................................................... 18
5.1.5 Lake Entrance Boulevard........................................................................................ 18
5.2 Kin Kin Creek............................................................................................... 18
5.3 Six Mile Creek............................................................................................... 19
5.3.1 Lake Macdonald....................................................................................................... 19
5.3.2 Cooroy Creek........................................................................................................... 19
5.3.3 Cooroora Creek........................................................................................................ 20
5.4 Coastal and Storm Tide Studies................................................................... 21
5.5 Key initiatives – Flood studies..................................................................... 21
6. Flood Mapping............................................................................ 22
6.1 Noosa Planning Scheme Flood Hazard Area............................................... 22
6.1.1 2016 Planning Scheme Amendment - Flood Hazard Area .............................. 22
6.2 2014 Disaster Management Flood Maps ..................................................... 23
6.3 Online flood mapping resources.................................................................. 23
6.4 GridFlow flood extent estimation................................................................ 23
6.5 Key initiatives – Flood mapping.................................................................. 24
7. Flood Records and Survey.......................................................... 25
7.1 Historical Flood records .............................................................................. 25
7.2 Flood Gauges................................................................................................ 26
7.2.1 Maximum Height Gauges....................................................................................... 26
7.2.2 Radio Telemetry Gauges......................................................................................... 26
7.3 Flood Studies Survey.................................................................................... 27
7.3.1 Ground survey.......................................................................................................... 27
Section 4
Contents 7.3.2 Bathymetric Survey ................................................................................................ 27
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7.3.3 Waterway Crossing Survey .................................................................................... 28
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7.4 Key initiatives – Flood records and survey.................................................. 28
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8. Flood Search Information ......................................................... 29
8.1 Key initiatives – Flood Search Information................................................. 29
9. Planning and Policy.................................................................... 30
9.1 Noosa Planning Scheme............................................................................... 30
9.2 Climate Change............................................................................................ 31
9.3 Key initiatives – Planning and policy.......................................................... 32
10. Disaster Management ................................................................ 33
10.1 Disaster Management Preparations............................................................. 33
10.1.1 Disaster management flood maps......................................................................... 33
10.1.2 Disaster management triggers................................................................................ 34
10.1.3 Disaster management redundancy........................................................................ 34
10.1.4 Real-time flood monitoring.................................................................................... 35
10.2 Disaster Management Activations............................................................... 35
10.2.1 Trained staff resources............................................................................................. 35
10.2.2 Overall understanding of flood specific procedures........................................... 36
10.3 Community Awareness................................................................................. 36
10.4 Flood Mitigation........................................................................................... 36
10.5 Key initiatives – Disaster management........................................................ 37
11. Implementation and Review...................................................... 38
Glossary................................................................................................... 39
Section 5
Executive Summary
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The purpose of the flood management plan is to provide A Capacity Assessment was carried out to review the
a key strategic document to facilitate a consistent organisation’s flood management capacity across these
understanding within the community and the organisation core areas. The Capacity Assessment established a
of Council’s flooding resources and direction for future series of performance targets and recommended some
flood management in Noosa. The Plan and its supporting desired outcomes to achieve these targets with the aim of
documents act as a central reference for communicating increasing the overall flood management capability of the
Council’s existing knowledge and capacity in flood organisation. Key outcomes have been carried forward into
management and as a guide for directing future investment this plan.
and implementation of actions towards improving the
community’s understanding and resilience to flood risks. The plan also provides the background context of flooding
in Noosa, summarises Council’s flooding resources,
The overall aim is that the Noosa community and council identifies emerging issues and concerns within the
are well informed about flood risk and well prepared for catchment, waterways and floodplains and establishes key
significant flood events. This can be achieved by Noosa initiatives to address these.
Council, residents and businesses having access to best
available flood information including past, present and The plan has been developed as a whole of council
future flooding conditions; ensuring flood resources are initiative with input from the various council business
up to date, reflect local conditions and take account of areas. The implementation plan will be reviewed and
existing and future climate; ensuring flood management updated annually for consideration in annual operational
and disaster management activities are well coordinated planning and budget processes. Council looks forward to
and communicated across all stakeholders; and ensuring working with other tiers of government, local businesses,
services are delivered that help protect the community, community organisations and individual residents to
improve community resilience and improve public access implement this Plan.
to information.
The plan identifies three core areas:
1. Flooding Resources - information such as flood
studies, mapping , records, survey and flood searches
2. Planning and policy in Council’s planning scheme,
building controls and other strategic and operational
plans, and development assessment
3. Disaster management - how Council prepares for and
responds to a flood event, community awareness and
flood mitigation works.
Noosa Council | Flood Management Plan | Page 5
Section 6
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Introduction
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Flooding affects large areas of Noosa Shire and can have The elements which comprise the Flood Management Plan
considerable consequences for people and property. and the process for preparing it are shown in the diagram
Council recognises that in order to reduce the risks below. This has involved the collation of flood studies,
of flooding to communities, assets, economies and mapping and records into an online flood information
environments it is important that lessons from the past repository to improve access to flooding resources;
and advances in knowledge and technology are recorded, preparation of a background report overviewing the
effectively communicated and applied. Long term planning historical context of flooding in Noosa, Council’s flooding
and prioritising having regard to both current and future resources, and emerging issues; and a capacity assessment
climate conditions is important for improving community of where the organisation is currently at in terms of its
flood resilience. flood management capabilities.
The Flood Management Plan seeks to improve the Council Based on the findings, the flood management plan has been
and community’s understanding, preparedness and established, including a set of core areas and key initiatives
resilience to flood risk. It provides the basis for coordinated for each core area. These have guided the development of
decision making, investment, information sharing and the five year implementation plan.
record keeping.
Noosa Council | Flood Management Plan | Page 6
Section 7
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The contributing catchments of Six Mile Creek are
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predominantly rural land uses and bushland with
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watersheds originating from the relatively steep hillsides
of the area and often inundating low lying property and
roadways. The Six Mile Creek watercourse and floodplain
intersects several significant hinterland road networks,
Flooding in such as Louis Bazzo Drive, Pomona Kin Kin Road and
Noosa Queens St Cooran.
Flooding in Six Mile Creek is solely the result of rainfall
The Noosa Council local government area is divided by runoff and local terrain and features. The waterways of Six
catchments contributing eastwards to the Noosa River or Mile Creek are unaffected by any tidal conditions.
westward towards the Mary River. Approximately two
Flood levels in the Noosa River are determined by heavy
thirds of the Noosa River catchment lies within the Shire
rainfalls generating catchment runoff which drain into
boundary with the remainder extending to the north
the Noosa River system. Elevated water levels in Laguna
above Lake Cootharaba and draining from the sands of the
Bay, principally due to storm surge, can cause flooding
Cooloola National Park within Gympie Regional Council.
in the lower reaches and also impede the discharge of
Refer to Figure 2.
rainfall derived floodwaters from the river. Local flooding
Six Mile Creek flows northwest from the southern refers to flooding along the upper reaches of creeks and
boundary of the Shire and is the largest waterway draining waterways. Local flooding is caused by heavy rainfalls
the western portion of the Shire towards the Mary River. over local upstream catchment areas and may not be
The Six Mile Creek catchment to Cooran is over 185 km2 associated with flooding from the river.
in area, bordered by Mount Tinbeerwah to the east, Black
Mountain to the south and the Kin Kin Creek catchment
to the north. Six Mile Creek includes two significant
tributaries of Cooroy Creek and Cooroora Creek and the
Lake Macdonald water supply dam owned and operated
by SEQWater. The dam was built in 1965 and its ungated
spillway raised in 1980 to increase the dam’s storage
capacity. The hinterland settlements of Cooroy, Pomona,
Lake Macdonald and Cooran were founded adjacent to the
local water courses of the area and hence have inherited
some vulnerability to flooding.
Noosa Council | Flood Management Plan | Page 7
Section 8
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Downstream of Tewantin, peak flood levels are governed The Noosa River catchment is large and much of it is
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by storm surge flooding; upstream of Tewantin, peak flood relatively flat. The two large lakes along the river, Lakes
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levels are governed by freshwater river flooding behaviour. Cootharaba and Cooroibah, provide large storage areas
which also slow down the flow of flood water on its way
to the river mouth. Lakes Cootharaba and Cooroibah exert
a significant effect on river flooding behaviour along the
Noosa River. Floodwaters generated from catchment areas
upstream of these lakes spread out across the waterbody
Figure 2: Map of major waterways and catchments.
Noosa Council | Flood Management Plan | Page 8
Section 9
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as they drain through the lake. The lakes provide a Apart from regular ocean tides, storm surges affect
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significant amount of temporary storage for passing water levels in Laguna Bay and flood levels in the lower
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floodwaters. Downstream of the lakes the temporary reaches of Noosa River. Increased water levels in Laguna
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storage of floodwaters: reduce peak water levels and Bay result in coastal waters flowing into the Noosa
discharges; slows the rate of rise of floodwaters (flood River and its lakes, with an associated increase in water
levels typically rise for 1-2 days at Tewantin before levels. Storm tide flooding can inundate normally dry
peaking); and assist with maintaining elevated flood land and affect property even without the contribution
levels and discharges for a relatively long period of of additional rainfall generated flooding in the River.
time (eg. at Tewantin, the February 1992 flood level The magnitude of a storm surge is determined by
remained over 1.5 m AHD for 45 hours). a combination of factors which include: inverted
barometric pressure; wind setup; and wave setup. These
Flooding behaviour along the Noosa River, especially affects are cumulative and are added to the normal tidal
its lower more populated reaches, is characterised conditions at the time. The combined water level from
by relatively low flood depths with generally slow all of these is referred to as the storm tide. Offshore
moving floodwaters which may persist for extended storm tide gauges are used to record storm tide levels.
periods which increase inconvenience and nuisance. The nearest gauge to Noosa River is located offshore of
Fortunately, relatively long ‘warning times’ are available Mooloolaba.
in which downstream residents can be alerted to the
severity and timing of impending flooding and can In a similar manner to flood studies, storm tide studies
undertake necessary actions to reduce damage to their are undertaken to estimate the potential magnitude of
goods and possessions. storm surges for a range of statistical frequencies. Whilst
generally conducted separately, results of a storm tide
With respect to the consequences of flooding, the main study are included as a possible boundary condition in
issues along the Noosa River relate to the modest level of the flood studies to reflect circumstances when the two
flood damage and the nuisance and inconvenience that events (i.e. storm surge and rainfall flooding) occur at
flooding causes urban communities. As noted above, the same time. It is a complex science to consider the
flood hazard and risk to life and limb are generally low coincidence of storm surges and extreme rainfall events.
along the Noosa River system.
The future of flooding in Noosa is unpredictable. Severe
Normal water levels in the lower Noosa River estuary weather events that bring flooding will occur. However,
display tidal characteristics and reflect the semi-diurnal recent research into the world’s changing climate
nature (i.e. there are two high tides and two low tides in suggests that over time factors such as increased ocean
every period of 24 hours 50 minutes) of water levels in water levels and increased frequencies of severe weather
Laguna Bay. Water levels in the river will rise and fall may result in an overall increase in the magnitude and
in response to the tide levels. These affects are greatest frequency of significant flood events. As a community
at the mouth and progressively dissipate upstream with with a large proportion of its residents located near the
only relatively minor tidal fluctuations evident in Lake coast and adjacent to waterways it is imperative that
Cootharaba. these factors be considered in our long term planning
for the region.
Noosa Council | Flood Management Plan | Page 9
Section 10
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“Some of the earliest references to flooding in the region date back
History of to the late 1800’s.”
Flooding in Noosa
Like all areas of Australia, Noosa’s heritage includes Shortly after this time a communal agricultural
thousands of years of Aboriginal history. However, settlement began around Lake Weyba in the lower Noosa
little is known of significant weather events and their River area made up of Brisbane people dispossessed by
impact on the lives of the traditional inhabitants of the the 1893 floods.
area prior to the arrival of European settlers. The local
modern history of the region is often interspersed with A handful of historical flood levels recorded in March
severe weather events resulting in shipwrecks and the 1955 represent the commencement of “official” flood
search and rescue of their survivors. It wasn’t until the records held by the Noosa Council. These records were
mid-1800’s that official surveys and reconnaissance of further supplemented following a significant flood event
the area were conducted. These early expeditions were in February 1968.
seeking access to the region’s timber and the River offered
a useful means for transporting timber to the coast for
shipping to Brisbane.
The clearing of large areas of timber within the catchment
and its replacement with orchards, pastures and sugar
cane would have introduced the first significant man
made change to the runoff characteristics of the river
system. Cleared catchments typically have faster runoff
rates and combined with the inherent disturbance to the
ground cleared catchments will often lose large amounts
of topsoil due to erosion. The eroded soil is transported
into local waterways and water bodies often smothering
aquatic ecosystems and reducing their depth and
subsequent capacity to convey flood waters.
Some of the earliest references to flooding in the region
date back to the late 1800’s. During the “Brisbane” floods
of 1893 there are recounts of rain falling for nine days
during which Lake Cootharaba rose by two metres.
February 1931 Milk Delivery Noosa Council Library Archives
Noosa Council | Flood Management Plan | Page 10
Section 11
Whilst still sparse the recorded water levels in the lakes and
the River from this event remain the highest on record.
The early 1970’s saw a series of successive flood events
impact upon South East Queensland. Cyclones in 1972
(Daisy), 1974 (Wanda) and 1976 (David) delivered
rainfall and flooding across the region and storm surges
to exposed coastal areas. These events impacted heavily
upon the development of Noosa Sound. As a result of
this and negotiations between the Noosa Council and the
state government walls and groynes were put in place to
protect the beach and Noosa Sound. Many of these walls February 1992 Gympie Terrace Noosa Council Library Archives
are still in place today and continue to serve residents and
the community.
depths of 744mm in 24 hours and 960mm over 72 hours
The following two decades were relatively uneventful with were recorded. These values correlate as an extreme weather
regards to flooding however in February 1992 a complex event with the severity of the rainfall being estimated as
meteorological event produced a low pressure trough being equivalent to a storm with a statistical recurrence
convergence zone in the wake of a departing cyclone (TC interval of up to 1 in 4,000 years1.
Damon).
The February 1992 flood event inundated some 540 lots,
Coastal sea levels were elevated by the storm surge effects 156 of them above floor level, and caused some $1.3
of the cyclone however; fortunately these coincided with million damage (1995$). The average damage bill for urban
lower seasonal tides. Across the catchment large volumes communities along the Noosa River system was calculated
of rainfall fell over relatively short durations. Rainfall in 1995 as being approximately $250,000 per annum2.
February 1931 Anderson’s House, Noosa Council Library Archives
1
Table 2.7 Flooding in the Noosa River Catchment 1995, updated 2001
2
Table 4.2 Flooding in the Noosa River Catchment 1995, updated 2001
Noosa Council | Flood Management Plan | Page 11
Section 12
In August 2007, in association with an upper trough More recent severe weather events that have impacted
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system and an east coast low (ECL) several rainfall stations more broadly upon south east Queensland such as the
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in Noosa recorded rainfall depths of greater than 650mm 2011 Brisbane Floods, 2013 ex TC Oswald and 2015 ex TC
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in 24 hours. Marcia have not resulted in significant flooding conditions
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within Noosa Shire. However; many low lying areas of
The flood levels reached in the Noosa River were the Noosa Shire are prone to flooding from small to medium
highest since 1992 and the third highest on record. This sized rainfall events. These locations are subjected to more
caused significant flooding in Lake Cooroibah and Lake regular nuisance flooding that does not generate significant
Cootharaba and moderate flooding at Tewantin. The loss to the community.
Bureau of Meteorology reported that this particularly rare
event broke many monthly records for August with some Upon reflection, Noosa Shire has been relatively fortunate
daily totals being the highest on record for any month. The to not have borne the brunt of some of the broader region’s
most statistically significant rainfall intensity was recorded more significant flood events. However, the historical
at Coops Corner TM in the river headwaters above Lake records are relatively short and the Shire’s coastal proximity,
Cootharaba. In only a 3 hour period a total of 415mm river estuaries and flood plains provide good reason to be
of rainfall was recorded. Water levels in the Lakes and at vigilant in determining and managing the risks associated
Tewantin remained elevated above minor flood levels for with flooding.
3 to 4 days.
February 1992 Gympie Terrace Noosa Council Library Archives
Noosa Council | Flood Management Plan | Page 12
Section 13
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Flood Management in Noosa
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The overall aim for this flood management plan
process is that the Noosa community and council are
well informed about flood risk and well prepared for
significant flood events. This can be achieved through
the following desired outcomes –
•
•
Flood resources are up to date, reflect local
conditions and take account of existing and future
climate;
Flood management and disaster management
activities are well planned, coordinated and
• Noosa Council, residents and businesses have communicated across all stakeholders ;
access to best available flood information for the • Services are delivered that help protect the
region; community, improve community resilience and
• Information on past, present and future flooding improve public access to information.
conditions is available and utilised to inform
Council works with the community to manage flood
planning and decision making;
risks and build community resilience in a number of
ways.
Noosa Council | Flood Management Plan | Page 13
Section 14
Flood management priorities have been considered under three core areas -
The following core principles describe the purpose of each core area and provide focus to the key initiatives and
actions arising from this plan.
1. Flooding Resources
Core principle 1: To make flood mapping accessible, informative and relevant
Core principle 2: To understand existing and future flooding conditions
Core principle 3: To learn from the past
2. Planning and policy
Core principle 4: To plan for existing and future climate conditions
Core principle 5: To improve public access to information
3. Disaster management
Core principle 6: To improve community resilience
Core principle 7: To prepare for flood events
Core principle 8: To protect our communities
Noosa Council | Flood Management Plan | Page 14
Section 15
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Flood Studies
Noosa Council has a suite of flood studies which cover 5.1.1 Noosa River Flood Study
most of the major waterways and floodplains of the region.
The age and origin of these studies varies from catchment The first major flood study of the Noosa River was
to catchment however, prior to de-amalgamation the completed in 1995 by consultants John Wilson and Partners
(JWP)3. The model is comprised of two separate modelling
Sunshine Coast Council had attempted to standardise
components. The first being the hydrology model which
some of the model approaches and generate a suite of
determines the amount of runoff generated from rainfall
relatively consistent flood studies across the region.
falling on contributing catchments; and the second being
the hydraulic model which determines the depth, extent and
The following sub-sections present a brief summary of the
speed of the runoff (i.e. the flood waters) as they flow along
flood studies available for each of the major catchments
the main waterway corridor(s) of the river. The original
and waterways of the Shire. Further details and documents
flood study utilised a combination of RAFTS hydrological
associated with each of the studies discussed here can be
modelling and one dimensional (1D) MIKE11 hydraulic
found via the Council’s Flood Information Repository modelling. 1D modelling refers to the basic “spine and rib”
established as part of this Plan. structure of the model. The spine being the waterway and
the ribs being linear cross sections of the terrain and river
The community can assess information from this repository
bed profile spaced along the River.
through an online flood search request.
Calibration of the original flood study models was
5.1 Noosa River Catchment Flood primarily limited to a single historical event recorded in
Studies February 1992. The event was considered a major flood
event with a reasonable selection of recorded flood levels
The Noosa River catchment covers approximately 106,000 for calibration. Another major flood event had occurred
hectares and extends from the Cooloola National Park in in 1968 however records for this event were sparse and
the north to the coastal township of Peregian in the south. in some cases determined to have been unreliable and
inconsistent with other relative historical records. Other
The catchment accounts for approximately half of Noosa significant historical events which occurred within the
Council local government area. catchment and river system in the early to mid 1970’s were
determined to have been too minor for calibration.
3
Noosa River Flood Study Noosa River Flood Study, by John Wilson & Partners Pty Ltd and Lawson & Treloar Pty Ltd, May 1995.
Noosa Council | Flood Management Plan | Page 15
Section 16
Three other minor historical events (January 1976, May Existing climate scenarios are used to inform the disaster
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1985 and June 1985) were used for model verification. management mapping for the Noosa River. This model
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continues to utilise the combination of RAFTS hydrological
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The findings of this study and subsequent associated
modelling and MIKE11 hydraulic modelling that was
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investigations have formed the basis of planning and
established by JWP in 1995.
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decision making in the River for almost 20 years.
In late 2013, prior to de-amalgamation and as part of a 5.1.2 Emerging Issues and Concerns for the
region-wide flood hazard mapping project, the Sunshine Noosa River
Coast Council (SCC) revised and re-ran the design event 5.1.2.1 Foreshore Erosion and Flood Velocity
temporal patterns for all flood models within the Noosa Distributions
Council area.
Several locations along the foreshores of the lower Noosa
The revised design rainfall patterns represent Duration River and Weyba Creek are currently experiencing shoreline
Independent Storm (DIS) patterns derived from Australian erosion. In some locations the erosion is threatening
Rainfall and Runoff (AR&R) Intensity Frequency and infrastructure, reducing accessibility and impacting upon the
Duration (IFD) curves for this region. amenity of the shoreline. Council is seeking to understand
the origin of the erosive forces which are contributing to
For the Noosa River the SCC 2013 update also included
the modifications to cross section depths for the river the shoreline erosion with the view of developing further
bathymetry near to the river mouth (as applied in the 1995 mitigation plans and works to reduce these forces and where
model) and the inclusion of dynamic tailwater boundary possible to rehabilitate these sites.
conditions for Laguna Bay.
Unfortunately, the 1D structure of the original Noosa
The dynamic tide boundary assumed the probability of the River Flood Study was only suitable for providing a
river flood matched the probability of the storm tide with broad understanding of the anticipated extents of flood
the peak of the storm tide timed to coincide with the peak inundation from a variety of flood events and provided
of the rainfall. limited insight into the distribution of flood velocities
across the river and adjacent floodplains.
The SCC 2013 model updates included model scenarios for
both existing and future climates. Future climate scenarios Whilst still valid, 1D modelling is rapidly being replaced
were used as the basis for the 2016 amendment to the by 2D modelling which allows improved representation
Planning Scheme Overlay’s flood hazard area. of the terrain surfaces and a more contiguous modelling
approach. 2D models are typically favoured in locations
with relatively flat waterway gradients and adjacent flood
plains, such as in the lower reaches of the Noosa River
system. Contemporary desktop computing capabilities
have also increased the useability of 2D models. 2D models
provide greater insight into the flow paths and associated
flow velocities of waterways and floodplains. The original
1D hydraulic flood model was unable to provide any
reliable flow path or flood velocity information. Hence, to
address the need to better understand the erosive processes
associated with flow velocities within the River an upgraded
2D hydraulic flood model has been commenced.
Noosa Council | Flood Management Plan | Page 16
Section 17
The development of a 2D hydraulic model of the River and Sunshine Coast Council commissioned consultants, Projex
its associated floodplains will also provide an insight into Partners, to undertake a detailed flood investigation4 of the
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the anticipated overbank flood flow velocities. Knowledge site. Subsequently the Sunshine Coast Council undertook
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of the anticipated overbank flood flow velocities will assist a follow up study to develop a detailed (TUFLOW) flood
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Council and local builders and developers with identifying model of the Daintree Estate reach and determine flood
locations suitable for applying the national Standard for mitigation options for the estate. The results of this model
the construction of buildings in flood hazard areas. It will form the basis for the current disaster management
also provide a more accurate estimation of design flood mapping.
velocities in high velocities locations where the Standard
Recent flood mitigation works have significantly improved
does not apply. Knowledge of the anticipated magnitude of
the flood immunity of affected properties. The Daintree
flood flow velocities is important in structural calculations
Estate flood model has been amended to include these
for designing buildings, walls and fences located within
works. The resulting inundation extents for the 1% AEP
flood prone areas.
(future climate) scenario form the basis of the 2016 Flood
To address the deficiencies of the original 1D flood Hazard Area Planning Scheme amendment.
study required it to be upgraded to a contemporary 2D
modelling approach. Where possible, improvements to the
calibration and extents of the flood modelling are being
pursued although there are relatively limited additional
flood records available.
The completion of the upgraded Noosa River flood model
will provide an improved understanding of the distribution
of both tidal velocities and flood flow velocities throughout
the waterway and associated floodplains of the lower
reaches of the Noosa River.
The updated modelling will allow for variations in the shape
of the river’s bathymetry to be modelled to determine the
sensitivity of the waterway’s velocity distributions to these 5.1.4 Ringtail Creek
changes. This will assist with understanding if natural or
In 2002 consultants Lawson and Treloar were commissioned
man-made changes to the shape of the river can have a
to undertake the Ringtail Creek Hydraulic Investigation5.
demonstrable effect on flow velocities and erosive forces
The flood models adopted for this investigation were
along the foreshore.
RAFTS for hydrological modelling and DELFT-FLS for 2D
5.1.3 Noosa Daintree Estate hydraulic modelling.
Noosa Daintree Estate is a 97 lot residential estate Anticipated inundation extents for a 100 year ARI local
constructed in circa 2000. The estate has been subject to catchment event combined with a 20 year ARI Regional
significant flooding on three occasions, with the most catchment event were used to inform the existing flood
severe impacts occurring from an event on the 24th hazard area of the Planning Scheme Natural Hazards
February 2012. Overlay map.
4
Noosa Daintree Estate Report 1 July 2013 by Projex Partners for Sunshine Coast Regional Council
5
Ringtail Creek Hydraulic Investigation, Lawson and Treloar Pty Ltd 2002
Noosa Council | Flood Management Plan | Page 17
Section 18
Between 2003 to 2005 additional investigations were 5.2 Kin Kin Creek
undertaken to assess the impacts of proposed developments
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in the catchments. In 2002 consultants Lawson and Treloar were commissioned
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to investigate the flooding characteristics for the Kin Kin
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5.1.5 Lake Entrance Boulevard Township7. This investigation prepared a flood model
using the Delft FLS 2D hydraulic modelling software.
Following flooding resulting from the February 2012 rain
event, Sunshine Coast Council engaged Projex Partners6 to In 2013 the Sunshine Coast Council commissioned Water
review a number of areas within the Sunshine Coast region Technology Pty Ltd8 to undertake an update of the 2002
affected by this flooding. The objective of the exercise was Kin Kin Flood Model. The earlier Delft FLS 2D model was
to provide a review for each affected area and subsequent converted to an updated TUFLOW model. The updated
recommendations for Council’s consideration on possible TUFLOW model has a model grid size resolution of 5m.
further investigation requirements and possible future The model is described as a sub-model covering a relatively
rectification/mitigation measures. small extent of Kin Kin Creek and extending approximately
2km downstream and approximately 600m upstream of
The review of the drainage regime and approved flood study Kin Kin township.
established that the drainage system has been constructed
in accordance with the development approvals and that The hydraulic model is also described as being “partially”
the existing Finished Floor Levels are above the previously calibrated as it has demonstrated some calibration to
calculated and approved Q100 flood level. historical peak flood debris levels and flood profiles
however has not been informed by calibrated hydrologic
The February 2012 rain event caused significant flooding
inflows and/or downstream water surface elevation
to some properties within the estate. It appears that this
boundary conditions. The 2013 investigation also included
flooding was a result of the excessive flows created by the
rain event and potentially exacerbated by downstream consideration of the potential impact on anticipated
tailwater conditions within the receiving downstream flood levels of re-vegetation within the waterway corridor
channel, as well as the impact of Eumundi-Noosa Road immediately upstream of Kin Kin township.
allowing water to back up. The 2013 Sunshine Coast Council flood hazard mapping
The February 2012 rain event has been calculated by project utilised the updated Kin Kin Flood Model to
Sunshine Coast Council to exceed a 1 in 100 year generate a suite of flood results for existing and future
recurrence interval. climate scenarios.
Future climate scenarios were used as the basis for the 2016
amendment to the Planning Scheme flood hazard area.
Existing climate scenarios are used to inform the disaster
management mapping for Kin Kin township.
6
Lake Entrance Boulevard Report by Projex Partners for Sunshine Coast Regional Council, August 2012
7
Kin Kin Flood Study by Lawson and Treloar Pty Ltd 2002
8
Kin Kin Flood Model Revision and Revegetation Hydraulic Impact Assessment, Water Technology Pty Ltd 2013
Noosa Council | Flood Management Plan | Page 18
Section 19
5.3 Six Mile Creek 5.3.2 Cooroy Creek
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Currently Council’s flooding information for the main In 2013 the Sunshine Coast Council commissioned Water
A F
watercourse and floodplain of Six Mile Creek is limited to Technology11 to develop hydrologic and hydraulic models
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the findings of the Six Mile Creek Flood Study Upgrade9 for the township of Cooroy. The primary purpose of this
undertaken by Sunshine Coast Council in 2013 as a study was to prepare and calibrate a hydrologic (XP-
part of their regional flood hazard mapping project. The RAFTS) and hydraulic model (TUFLOW) for the greater
flood model utilised by the Sunshine Coast Council was Cooroy township area such that Council could then use
based upon an existing flood model originally developed the model to undertake further analyses.
in 2001 by JWP10 to investigate a dam break scenario at
Lake Macdonald. This base model utilises coarse, sparsely The hydrologic model included the analysis of the greater
spaced cross section data and does not include details of catchment areas that contribute to the Cooroy Township
local road crossings. This 15 year old base model is a one as well as immediate surrounds. Specifically, this included
dimensional hydraulic model which utilises the MIKE 11 Cooroy Creek, Six Mile Creek Left Branch, Cudgerie
modelling platform. Creek as well as tributaries and sections of the Six Mile
Creek main branch. The hydraulic model developed as
The SCC 2013 model updates for Six Mile Creek include part of this study extends approximately 1km upstream of
model scenarios for both existing and future climates. the Bruce Highway downstream to approximately 500m
Future climate scenarios were used as the basis for the downstream of the confluence of the Six Mile Creek main
2016 amendment to the Planning Scheme flood hazard branch and Six Mile Creek left branch. The model includes
area. Existing climate scenarios are used to inform the
24 separate hydraulic structures located throughout the
disaster management mapping for the Noosa River.
model area.
5.3.1 Lake Macdonald In late 2013 Hydrology and Water Management
Consulting Pty Ltd (HWMC) was engaged12 by Sunshine
In 2001 consultants JWP were engaged to determine flood
Coast Council to undertake further updates to the Cooroy
levels downstream of the dam as a result of severe flooding
flood model previously prepared by Water Technology.
combined with embankment failure. The model is a one
The results of this model form the basis for the current
dimensional hydraulic model which utilises the MIKE 11
disaster management mapping.
modelling platform.
In a 2007 update of a Failure Impact Assessment, the Recent upgrades to the Bruce Highway have delivered
MIKE11 model was extended a further 15km downstream flood mitigation benefits to some properties immediately
in accordance with Department of Natural Resources and downstream of the highway. The Cooroy flood study
Water (NRW) guidelines and recommendation from the model has been amended to include these works and
Sunwater Dam Safety Review. the resulting inundation extents for the 1% AEP (future
climate) scenario form the basis of the 2016 amendment
This model has ultimately been adopted as the basis for to the Planning Scheme flood hazard area.
the Six Mile Creek flood study upgrade undertaken by
Sunshine Coast Council in 2013. Cross sections in the
lower 15km extension of the model were sourced from 5m
contour plans.
9
Six Mile Creek Flood Study Upgrade Final Report By Sunshine Coast Council February 2014
10
Noosa Shire Council Lake MacDonald Dam Break Flood Study by John Wilson and Partners June 2001
11
Cooroy Flood Study by Water Technology, July 2013
Noosa Council | Flood Management Plan | Page 19
Section 20
5.3.3 Cooroora Creek Following the February 2012 flood, SCC carried out survey
to record peak flood levels reached during this event and
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The main watercourse flowing through the town of
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these were used in the investigation for model calibration.
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Pomona is Cooroora Creek, with several of its tributaries
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also flowing through the township. HWMC’s analysis of the rainfall intensities recorded at the
Pomona rain gauge for the February 2012 event, estimates
During the evening of February 24, 2012, Pomona was that this event was equivalent to approximately a 500 year
subject to a major flood event which impacted homes, Average Recurrence Interval (ARI) event.
businesses and infrastructure across the region. During
this event, the township was inundated by flows from The design event results of the HWMC flood study model
Cooroora Creek and its various tributaries. form the basis of the disaster management mapping for
Pomona based upon existing climate conditions.
Following the event, the Sunshine Coast Council engaged
the consulting engineering firm, Projex Partners Pty Ltd, Recent flood mitigation works have included house/land
to undertake a flood investigation study13. This study resumptions and removal, earthworks and channelising of
reviewed the history of previous flood studies in the region, local drainage in and around Rifle Street.
undertook a site inspection and made recommendations
regarding future works. One of these recommendations The Cooroora Creek flood study model has been amended
was to complete local and regional flood modelling so as to to include these works and the resulting inundation extents
provide accurate design flood levels through the township. for the 1% AEP (future climate) scenario form the basis of
the 2016 amendment to the Planning Scheme flood hazard
In 2013, prior to de-amalgamation, the Sunshine Coast area.
Council commissioned Hydrology and Water Management
Consulting Pty Ltd (HWMC) to setup and calibrate a Additional model runs for minor (2 year ARI), moderate
detailed flood model14 that was suitable for defining (10 year ARI) and extreme (500 year ARI) flood events,
flooding characteristics within all significant flow paths which include the recent mitigation works, are required to
through the Pomona Township and local surrounds. update the disaster management map series for Pomona.
12
Cooroy Mitigation Options Review by Hydrology and Water Management Consulting, December 2013.
13
Rifle Street, Pomona Drainage Report by Projex Partners for Sunshine Coast Regional Council 2012
14
Pomona Flood Study by Hydrology and Water Management Consulting, December 2013
Noosa Council | Flood Management Plan | Page 20
Section 21
5.4 Coastal and Storm Tide Studies 5.4.1.2 NDRP Storm Tide Hazard Interpolation
Study (GHD)
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5.4.1.1 Sunshine Coast Storm Tide Study (Aurecon
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2013) The NDRP Storm Tide Hazard Interpolation Study15 was
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undertaken by GHD on behalf of the Department of
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The Sunshine Coast Storm Tide Study was commissioned Science, Information Technology, Innovation and the Arts
by the Sunshine Coast Council prior to de-amalgamation (DSITIA). DSITIA were seeking information on the risk of
and completed by Aurecon in December 2013. storm tide hazards across the State that would identify the
As a part of the Storm Tide Study a new Noosa River relative likelihood of specific communities being subjected
TUFLOW (Classic) model was prepared using a detailed to dangerous inundation events.
nested 2D grid and drawing on available survey and The principal requirement of this study was to identify,
bathymetric data, along with the latest available LiDAR based on a consistent methodology using data from
survey. Model calibration was undertaken to demonstrate existing studies, the Average Recurrence Interval (ARI, or
tidal and storm tide performance at selected locations. Return Period event) for a range of ocean water levels for
each coastal LGA area. The minimum ARI levels required
The Noosa River TUFLOW Storm Tide model covers a large
were the 20, 50, 100, 500 and 1000 y ARI event, plus the
computational area which includes the inter-tidal lakes in
estimated Probable Maximum Level.
the upper estuary. A relatively coarse 40 m computation
grid was adopted to represent bathymetric and hydraulic This was a state wide study with reference to Noosa and the
conditions over much of the model area. However, for Sunshine Coast.
the Noosa River entrance and the estuarine areas around
Noosa Heads, Noosaville and Tewantin higher resolution 5.5 Key initiatives – Flood studies
was adopted to ensure model and mapping detail was
adequately represented. Accordingly, the model has been The implementation plan will include initiatives that aim
prepared as a nested 2D2D model so that these areas could to –
be modelled as higher resolution, but ensuring the dynamic • Prepare a flood study of Six Mile Creek using latest
interactions between the entrance areas and the upper lakes flood modelling techniques and standards that are
were maintained. The urbanised areas around the inlet were consistent with other flood models for the region.
modelled using a fine grid of 5 m. The nested high resolution
• Upgrade of the Noosa River Model to a contemporary
grid is 6.7 km by 5 km and covers the area from the estuary
2D modelling platform and cover the major
inlet upstream to just north of Tewantin and south toward
watercourses and floodplains to and beyond Kin Kin.
the entrance to Lake Weyba.
• Explore foreshore erosion within the lower reaches of
The river channels between the lakes, particularly the Noosa River using the Noosa River Model.
upstream of Tewantin and between Lake Cootharaba and
Lake Cooroibah, are relatively narrow and were poorly • Include flood mitigation modelling for Daintree
represented at 40 m resolution. To address this, nested Estate, Cooroy Creek and Cooroora Creek for all
1D channels were introduced to represent the hydraulic design flood events in Council’s Flood Information
conveyance characteristics of these channels. Repository.
• Review the custodianship and management of
Council’s flood study data (including spatial flood
data files) with the view of establishing a clear point of
contact with regards to flooding information.
15
NDRP Storm Tide Hazard Interpolation Study Report by GHD
for Department of Science, Information Technology, Innovation and the Arts, May 2013
Noosa Council | Flood Management Plan | Page 21
Section 22
6
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Flood Mapping
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Flood maps are the visible product of flood studies and 6.1 Noosa Planning Scheme Flood
flood records. They are a critical tool for communicating Hazard Area
the findings of a flood analysis and/or an historical level
of inundation. Flood maps are often published for public Noosa Planning Scheme’s current Natural Hazard Landslide
access and are commonly used for regulatory purposes and Flooding Overlay series (OM1.3 to OM 9.3)16 depicts a
associated with Planning Scheme overlays. flood inundation extent for the Noosa River estuary from
Lake Cootharaba to the River mouth, Kin Kin township
Flood mapping is also critical for disaster planning (pre an (Kin Kin Creek) and some sections of creek branches in
event) and disaster management during an event. Flood Cooroy. These overlay maps typically represent a 1% AEP
mapping can also be used in development assessment to flood event based upon current climate conditions.
determine the potential exposure of a development site
to mapped flood conditions beyond those presented in a The Noosa River estuary Flood Hazard Area was derived
regulatory overlay. from the Noosa River Flood Study by JWP 1995. The Kin
Kin Flood Hazard area was derived from the Kin Kin Flood
Flood maps are a snap shot of a chosen scenario of flood Study by Lawson and Treloar 2002.
related conditions. Hence a series of flood maps may be
required to adequately cover the needs of the intended The Cooroy Flood Hazard Areas were derived from the
user. Cooroy Flood Study by Lawson and Treloar 2002.
Noosa Council possess flood maps for: administering the 6.1.1 2016 Planning Scheme Amendment -
Planning Scheme (Noosa Plan); disaster management Flood Hazard Area
planning and response; and development assessment.
In late 2013, prior to de-amalgamation and as part of a
flood hazard mapping project, the Sunshine Coast Council
(SCC) revised and re-ran the design event temporal
patterns for all flood models within the Noosa Council
area.
16
As amended 16 September 2013
NoosaNoosa
Council
Council
| Flood
| Flood
Management
Management
Plan |Plan
Page| Page
22 22
Section 23
The revised design rainfall patterns represent Duration • Major (100 year ARI); or
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Independent Storm (DIS) patterns derived from Australian
• Extreme (500 year ARI).
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Rainfall and Runoff (AR&R) Intensity Frequency and
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Duration (IFD) curves for this region. The Disaster Management Flood Map series cover all
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locations where Council possesses flood models and need
The SCC 2013 update also included the modifications to be updated periodically to reflect changes within the
to cross section depths for the river bathymetry near to catchments and upgrades to flood models.
the river mouth (as applied in the 1995 model) and the
inclusion of dynamic tailwater boundary conditions for 6.3 Online flood mapping resources
Laguna Bay.
Three forms of flood mapping can be accessed via Council’s
The dynamic tide boundary assumed the probability of the website. These include:
river flood matched the probability of the storm tide with
the peak of the storm tide timed to coincide with the peak • River and Storm Tide flood map series prepared
of the rainfall. by Sunshine Coast Council and accessible via the
Disaster and Emergencies and Get Ready web pages
The SCC 2013 model updates included model scenarios for (http://www.noosa.qld.gov.au/river-and-storm-tide-
both existing and future climates. flood-maps)
• Noosa Plan’s Natural Hazard Landslide and Flooding
Future climate scenarios were used as the basis for the 2016
Overlay series (OM1.3 to OM 9.3); and
amendment to the Planning Scheme flood hazard area.
• Council’s online interactive mapping portal. The portal
The results of the SCC 2013 model updates also form the currently presents three flood inundation layers:
basis of the current flood mapping and design event flood
1. Flood 100y Inundation Info – depicts the limit of
levels for the Noosa River.
flood inundation mapping derived from related flood
studies for a location.
6.2 2014 Disaster Management Flood
Maps 2. Flood 100y Inundation Area – depicts a flood
inundation extent polygon (non transparent) for the
The 2014 Disaster Management Flood Map series are 100 year (1% AEP) flood inundation based upon
based upon the flood inundation extents derived from the current climate conditions and derived from the
SCC 2013 flood model updates. Flood inundation extents Noosa River Flood Study, JWP 1995.
have been projected onto a digital elevation model of the
3. Proposed Flood Hazard Overlay 2014 – depicts the
ground surface derived from aerial laser survey.
proposed amendment to the Planning Scheme as
Disaster management flood maps are based upon existing advertised for public consultation. Public consultation
climate conditions. ended in October 2015.
4. Final Flood Hazard Overlay 2016 Amendment
Each flood map series references the relative magnitude of
(Pending Minister’s Approval).
the flood event as either:
• Minor (2 year ARI);
• Moderate (10 year ARI);
Noosa Council | Flood Management Plan | Page 23
Noosa Social Strategy | Page 23
Section 24
6.4 GridFlow flood extent estimation The absolute flood levels and flood flow velocities
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determined by the GridFlow analysis are not suitable for
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The GridFlow flood extent estimation project was setting minimum floor levels or for estimating flood flow
A
conducted by the Sunshine Coast Council across all forces. More detailed, local calculations and observations
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catchments of the Sunshine Coast. would be required to inform these values. GridFlow flood
extents may be a useful trigger for highlighting potentially
The project’s aim was to prepare a preliminary estimate of
flood sensitive locations that are beyond the limits of
flood inundation extents for a 1% AEP flood event, for all
existing flood models.
identified water courses.
The analysis process utilised to determine the preliminary
6.5 Key initiatives – Flood mapping
flood extent was based upon GIS algorithms which
The implementation plan will include initiatives that aim
determined contributing catchment areas at regular
to –
increments along a waterway and then estimated flood
discharge for each location using standard Rational • Review the flood hazard area mapping for the Ringtail
Method computations. Creek sub-catchment (Cooroibah area) following
completion of the Noosa River Flood Study Upgrade.
A flood extent was then estimated at each location by
• Update disaster management flood mapping series to
applying the computed flood discharge to the standard
reflect flood mitigation works and completion of the
Mannings equation based upon a cross section derived
Noosa River Model Upgrade.
from a Digital Elevation Model (DEM). The resulting
flood extent provides a preliminary estimate for flood • Prepare and maintain flood mapping layers showing
inundation extents. These estimated flood extents do not flood levels, flood extents and associated minimum
consider local channel features or structures which may floor levels for existing and future climate.
influence the actual extents of inundation. • Include 1% AEP flood contour mapping and associated
minimum floor levels mapping, 1%AEP flood extents
In the absence of more detailed local flood modelling the
and depths to Council’s mapping system for officer
GridFlow flood estimation method is a useful first-pass for
assess.
identifying locations that may be subject to potential flood
inundation from a 1% AEP flood event.
Noosa Council | Flood Management Plan | Page 24
Section 25
7
Flood records
and survey
The collection and archiving of flood records is a task 7.1 Historical Flood records
undertaken to assist future generations by continuing to
improve the understanding of the flood characteristics Noosa Council has a relatively short history of flood
of an area. Records of historical floods are an important records for the region. The majority of the region’s highest
reference to support planning and decision making. The recorded flood levels were obtained following the February
validity of a flood model is often determined by a model’s 1992 flood event. Prior to this a sparse selection of records
ability to reproduce the recordings of an historical event. exists for the major flood event of 1968 and other significant
events throughout the 1970’s.
The capture and storage of flood levels is predominantly
a spatial mapping exercise. However, it is important that It is often difficult to confirm the accuracy and reliability of
these records be maintained in conjunction with design historical flood levels. Flood levels are often recorded from
flood levels derived from flood studies to ensure anomalies the remnants of vegetation debris, water stains, damage to
in either data set are recognised (and explored), and to infrastructure and occasionally from anecdotal references.
maintain a context of reference between actual recorded These records offer a limited insight into the nature of each
event levels and those proposed as design levels. In doing flood event and may be influenced by local conditions,
so it is also important to maintain access to all available survey datums and other physical changes which may have
historical flood records (not just the highest). This will occurred in the floodway. For these reasons some caution
enable further consideration of the frequency of flooding is required when interpreting historical records.
at a location.
Determining the frequency of flooding from a series of
historic flood records requires some consistency in the
collection of records to ensure the events recorded reflect
the full nature of flooding experienced over periods of time
at a location.
Noosa Council | Flood Management Plan | Page 25
Section 26
7.2 Flood Gauges 7.2.2 Radio Telemetry Gauges
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To improve the confidence in flood records Council has Radio telemetry gauges (also referred to as ALERT stations)
A
established a network of flood gauges throughout the utilise sensors and electronic systems to continuously
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major waterways of the area. Council manages two types measure water levels and rainfall and transmit these
of flood gauges; these being: Maximum Height Gauges readings in real-time to a stakeholder organisation via
(MHGs) and Radio Telemetry Gauges. radio signals.
7.2.1 Maximum Height Gauges The Bureau of Meteorology (BoM) in partnership with
Noosa Council and other State agencies maintain and
Maximum Height Gauges (MHGs) are simple peak water operate a network of ALERT rainfall and river height
level recording stations located throughout the region gauges throughout the Noosa Council local government
close to waterways. Noosa Council currently manages area. These rainfall and river height stations are used for
46 MHGs. During times of inundation water surrounds flood warning and forecasting operations in the Bureau’s
the MHG and fills the inside of the gauge via small holes Flood Warning Centre located in Brisbane and are also
drilled into the base of the gauge outer housing. When the monitored locally to assist with disaster management
flood waters recede from around the gauge water remains activities during flood events.
trapped in the cups up to the peak level reached. This
water will remain in the gauge for 2-3 weeks depending There are currently eight water level ALERT stations and
upon evaporation. These water levels are recorded during 12 rainfall ALERT stations. Some stations monitor both
an inspection of the gauge following a flood event. MHGs rainfall and water levels whilst others may only monitor
have no moving parts or electrical circuits and hence either rainfall or water level.
offer a robust and reliable means of accurately recording
the peak flood level for a given location. Some periodic
maintenance is required to ensure the MHGs remain
functional and accessible.
Rainfall and water level data is collected by stakeholder organisations via the BoM’s Enviromon software.
Noosa Council | Flood Management Plan | Page 26
Section 27
7.3 Flood Studies Survey 7.3.2 Bathymetric Survey
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Flood studies will generally be informed by a flood model Bathymetric survey is information relating to river and lake
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of the area under investigation. Flood models are typically bed surfaces. Bathymetric survey is typically undertaken
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computer based simulations of the terrain and other below normal water surface levels. Detailed bathymetric
landform features combined with algorithms to translate survey was been collected for the lower reaches of the
rainfall into runoff and flooding conditions. To create Noosa River in 201017. This survey was collected using a
an accurate flood model of a location requires survey combination of depth sonar readings and GPS tracking
information of the terrain and any significant features to map the bed surface of the river. Sandy coastal river
which may influence the flow of flood waters. There are estuaries like the Noosa River are dynamic systems that are
typically three types of survey data required for flood continuously changing due to freshwater flows and tidal
models. These being: ground survey; bathymetric survey currents. This survey offers a snap shot in time of the river
and waterway crossings survey. bed during ambient (non flood) flow conditions.
7.3.1 Ground survey Standard ALS survey techniques do not capture terrain
surfaces below water levels although specialised equipment
Ground survey data for flood models was traditionally and processes continue to be developed in this field. In
collected as a series of cross sections surveyed across semi- 2013 a pilot study was conducted on the Sunshine Coast
regular intervals along a waterway and capturing ground as a collaboration between the Queensland Government,
levels which extend across the flood plain. The collection CRC for Spatial Information (CRCSI) and the Department
of cross section survey over large areas is labour intensive of Climate Change and Energy Efficiency (DCCEE). The
and returns a relatively limited portrayal of the terrain. aim of the pilot study was to provide useful evidence to
More contemporary survey methods utilise aerial laser inform future data gathering by considering the methods
scanning (ALS) also referred to as LiDAR. ALS survey and technology available and the relationship between
is undertaken from a specialised aircraft and sensor the accuracy of the bathymetry and our confidence in the
equipment and provides a detailed record of surface levels modelling outputs. The pilot study found that the current
capable of capturing dozens of readings per square metre technology of bathymetric LIDAR was not recommended
across entire catchment areas. ALS data sets are extensive for streams, estuaries and lakes but may be an efficient
and offer a detailed assessment of visible surfaces capable method for near-shore coastal areas.
of generating an accurate representation of the terrain and
other features from potentially billions of surface point The collection of additional bathymetric survey of the
records. Noosa River is recommended to supplement existing
survey of the River’s bed profile to help monitor and
ALS data sets for a location are generated periodically by understand changes over time and potential impacts.
government agencies and private suppliers. A 2016 series of
ALS data has been captured for Noosa and post processing
of this data is underway.
17
Lower Noosa River Hydrographic Survey Definium Survey 2010
Noosa Council | Flood Management Plan | Page 27
Section 28
7.3.3 Waterway Crossing Survey 7.4 Key initiatives – Flood records and
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survey
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Waterway crossing survey provides details of structures
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such as bridges and culverts that cross waterways. The The implementation plan will include initiatives that aim
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crossing survey will confirm the available waterway area to –
beneath a structure and other critical dimensions such as
the thickness of the deck of the structure and the elevation • Collect peak flood level records along Kin Kin Creek
of the road surface above which inundation of the crossing for a variety of flood events to improve flood model
will occur. Accurate waterway crossing survey is important calibration in this location.
for determining the influence a crossing may have on local • Install MHG gauges along Kin Kin Creek adjacent to
flood levels and for planning for disaster management Dr Pages Road and along Cooroora Creek and Cooroy
responses during flood events. Creek.
Structure survey for Noosa River was undertaken by • Review existing radio telemetry flood gauge network
Aurecon in 2011 on behalf of Sunshine Coast Council. and prioritise potential locations for additional gauges.
The survey includes a collection of 30 annotated sketches • Complete additional bathymetric survey of the Noosa
of structure dimensions and relevant flood related River to supplement existing survey of the River’s bed
infrastructure elevations. Selections of other structure profile to help monitor and understand changes over
details are available for some estates and other significant time and potential impacts.
crossings throughout the catchments.
• Develop a guideline for collecting and storing flood
related field data
• Establish a regular maintenance program and
procedures for maintaining the Council’s Maximum
Height Gauges (MHGs).
•
C onfirm triggers and
procedures for reading
and maintaining Council’s
network of Maximum Height
Gauges.
• Incorporate all available
historical flood level data
into an accessible GIS
environment.
Noosa Council | Flood Management Plan | Page 28
Section 29
8
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Flood Search
Information
It was a key recommendation of the 2012 Queensland 8.1 Key initiatives – Flood Search
Floods Commission of Inquiry to make relevant flooding Information
information more publicly accessible. Making flooding
information available to the public and more specifically • Provide an automated flood search certificate system
professional consultants improves consistency between for generating and issuing certificates.
development applications and Council’s information • Prepare advice regarding the process for applying for
resources that will be used to assess applications. Council flood study information via Council’s website.
Noosa Council currently provides a level of service with • Establish a standard agreement for consultants to sign
regards to making flooding information accessible to when requesting access to Council flood study data
the public. Property searches for Flood Information files.
can be purchased from Council and some limited flood
inundation mapping is currently available online for
planning purposes via the Council’s Interactive Mapping
Portal.
As flooding information becomes more readily accessible
local governments are progressing towards the on-demand
publication of property searches for flood information.
The automation of preparing property searches for flood
information would improve consistency and potentially
reduce overheads for Council. It is recommended that the
public have on demand access to detailed property specific
flooding information via the organisation’s website.
Noosa Council | Flood Management Plan | Page 29
Section 30
9
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Planning
and Policy
Whilst flood studies, flood mapping and flood data 9.1 Noosa Planning Scheme
collection inform our understanding of the flooding
characteristics of the region it is the organisation’s planning The most visible application of planning and policy for
and policy positions that define the response. flooding is presented from within the Noosa Planning
Scheme (The Noosa Plan 2006). The Planning Scheme
Council’s Development Assessment Unit is responsible for includes provisions in the Natural Hazards Overlay Code
the assessment of development applications and supporting for:
information such as flood models and associated reporting
• minimum floor levels;
which may be submitted by an applicant in response to the
provisions of the Planning Scheme. • filling and excavations in flood hazard areas;
• storage of hazardous materials with regards to
Flood management covers a diverse range of responsibilities
flooding;
and council stakeholders and hence it remains important
for these functions to be overseen and coordinated by • design requirements for flood resilience with regards
a clearly identifiable representative or a collective of to flood immunity relating to essential infrastructure,
representatives which may meet under the banner of an community uses, subdivisions, residential and non-
internal flooding working group. Such representation residential buildings
would serve to rationalise competing demands from • disaster management and evacuation;
across the organisation, actively promote the sharing of
• ensuring development on the floodplain does not
information, and identify opportunities for mutual benefit
impact on the floodplain characteristics and flood
whilst avoiding duplication and conflicts.
capacity or downstream properties; and
• considering current and future climate conditions.
The Natural Hazard: Landslide and Flooding Overlay
series of maps depict a Flood Hazard Area for flood prone
locations. The flood hazard area typically represents the
extents of a 1% AEP flood event. Developments proposed
within the flood hazard area of the Overlay are required
to address the relevant provisions of the Natural Hazard
Overlay Code and respond to the requirements outlined in
Planning Scheme Policy 01.
Noosa Council | Flood Management Plan | Page 30
Section 31
Requirements for minimum floor levels to achieve 9.2 Climate Change
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acceptable standards of flood immunity are presented in
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the Detached House Code and the Building Works Code. Along with other levels of government, Councils have
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a responsibility for planning and preparing for natural
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The planning scheme provisions also reflect the State hazard risks within the community, and this includes
Planning Policy for Safety and resilience to hazards. longer term climate related risks associated with flooding,
extreme storms, coastal erosion, and changes to rainfall
Council is under some pressure to allow basement carparks
and temperature.
that can be mechanically pumped in a flood event, as
different to the current position of required underground The increasing severity of natural hazards and future
carparks to be gravity fed. While Council has made liability risks means council needs to be taking steps to
some allowance for commercial basement carparks to be understand the risks to the community, infrastructure and
mechanically pumped, it is not recommended that this be assets and identifying solutions for the short, medium and
allow for residential developments where resident’s cars long term.
are at risk. Nonetheless consideration should be given to
new technologies for basement flood prevention and the Current projections by 2100 indicate:
scheme should ensure that it is written in a way that does
• A projected regional sea level rise of 0.8m. This is
not stifle the adoption of innovative solutions.
expected to contribute to an increase in the frequency
Council has commenced work on a new planning scheme and severity of coastal flooding, increase in tidal
for Noosa Shire which is expected to include similar detailed extremes and increased coastal erosion
policy positions around flooding and best available flood • A southward shift in tropical cyclone activity
mapping as per the current scheme that takes account of
• Fewer cyclones but an increase in the intensity of
current and future climate. The new scheme should ensure
cyclones and extreme storm events of up to 10%.
flood management outcomes are consistent with broader
policy outcomes and principles for the Shire as set out in • More heatwaves: The number of days over 35 degrees
this Plan. is projected to increase by an additional 30 days per
annum by 2100.
Improvements in the consistency between development
• Accelerated coastal erosion
application and assessment processes can be gained by
providing clear guidance on preferred or acceptable • Permanent inundation of low lying areas
methods and parameters for undertaking flooding analysis • Increased areas impacted by storm surge and king
in this region. As for most studies of natural processes tides
numerous assumptions are required to be made in order
• Property and infrastructure may not be constructed to
to simulate the characteristics of the natural environment.
cope with increasingly frequent and extreme weather
These characteristics can change from region to region and
events.
some parameters may be subject to professional judgement
and local preferences. Where possible, it is recommended
that guidance be provided to outline acceptable (or
recommended) standards for common parameters
required in flood analysis.
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The increasing risks of climate related hazards will likely 9.3 Key initiatives – Planning and
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affect council in the areas of— policy
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• Litigation and legal liability
The implementation plan will include initiatives that aim
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• Community expectations to –
• Land use planning and development • Review planning scheme provisions with regards
• Asset and infrastructure planning, design and to flooding to ensure alignment and outcomes are
management consistent with principles adopted via this Flood
Management Plan.
• Financial sustainability.
• In conjunction with the preparation of a new planning
The 2016 Planning Scheme flood hazard area overlay scheme prepare a planning scheme policy outlining
includes parameters which reflect future climate conditions preferred methods and parameters for flood studies
for 2100. These parameters include an increase in rainfall and flood management.
intensity for severe weather events and increases in mean
• Include as part of the planning scheme flood hazard
sea levels over time. To reflect these conditions the design
mapping the areas of maximum flow velocities to
rainfall temporal patterns have been increased by 20%18
assist with development assessment and building and
and mean sea levels raised by 800mm19. These values are
infrastructure design.
consistent with current recommendations and industry
practice for Queensland communities. • Enforce council’s position requiring gravity fed
carparks for new residential development and ensure
Council has commenced the preparation of a Climate there is improved clarity on this in the new planning
Change Adaptation Plan for Noosa Shire. The plan scheme.
will focus on climate related hazards such as flooding, • Establish an internal flooding working group to
storm surge, extreme storm events, coastal erosion and help coordinate flood management functions across
permanent inundation from sea level rise. It will also council and to assist with facilitating council wide
look at adaptation for bushfire hazard and biodiversity input into developing planning provisions and council
conservation. The plan will identify the coastal hazards, guidelines related to flooding.
risks, and vulnerable areas and assets. It will investigate
• Support members of the flood working group by
actions to help minimise the exposure of new assets to
offering professional development opportunities
future damages (eg building extra flood resilience into new
related to planning and policy with regards to flooding.
roads and bridges) and options for improving the resilience
of existing assets and communities. • Prepare a climate change adaptation plan that
addresses future flood hazard risk and the likely
The outcomes of the Climate Change Adaptation Plan will associated consequences for vulnerable communities
be important for informing policy responses for the new and infrastructure and identifies future options for
planning scheme, as well as community, infrastructure and discussion with the community.
financial planning.
18
Increasing Queensland’s resilience to inland flooding in a changing climate: Final Report on the Inland Flooding Study. A joint project of
Department of Environment and Resource Management, Department of Infrastructure and Planning and Local Government Association of
Queensland. 2010
19
The projected sea-level rise of 0.8 metres by the year 2100 is based on climate modelling and probable scenarios of world development
presented in the Forth Assessment Report released in 2007. See IPCC, 2007: Climate Change 2007: Synthesis Report. Contribution of Working
Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, Pachauri, R.K and
Reisinger, A.(eds.)]. IPCC, Geneva, Switzerland, 104 pp.
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10
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Disaster
Management
10.1 Disaster Management Preparations 10.1.1 Disaster management flood maps
Disaster management preparation refers to the capacity Noosa Council has prepared a series of flood inundation
of the organisation to prepare for a disaster management maps which depict Minor, Moderate, Major and Extreme
activation related to flooding. Typical preparations include: flood events. These maps represent flood study findings
for current climate design flood events with average
• the production of a series of flood inundation maps
recurrence intervals of 2 years, 10 years, 100 years and 500
which depict a range of flood events across vulnerable
years respectively.
areas;
• the establishment of observable triggers which The disaster management flood map series include
may inform the activation of disaster management references to radio telemetry water level gauges associated
responses; with the mapped waterways. Anticipated design event
flood levels at each gauge’s location have been referenced
• ensuring adequate redundancies exist for critical
from the relevant studies and are presented on the maps
systems and reference material; and
as a series of flood totems. Real-time water level readings
• the training of relevant officers in being able to monitor transmitted from the gauges to the BoM’s Enviromon
real-time flood information (rainfall and water levels) system can be cross referenced to the flood totems to
via the Bureau of Meteorology (BoM) Enviromon visually determine the equivalent design flood event for
system or equivalent. each gauge location. The description of this design event
as either a Minor, Moderate, Major and Extreme flood
Council has disaster management plans in place for
event can then be used in communications throughout the
Cooran, Kin Kin, Pomona and Daintree Estate.
disaster management stakeholders and the community.
For this process to function, relevant officers need to
be capable of accessing and extracting real-time flood
information from the BoM’s Enviromon system.
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Council provides online access to a series of River and To provide correct advice during a flood event on the
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Storm Tide maps (in PDF format) for communicating current triggers and consequences requires each flood
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the progression of potential flood extents and the relative gauge to be maintained and calibrated to transmit accurate
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depth of potential flooding within the inundation extents. incremental signals. Also, once received by the Enviromon
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These maps are not linked to any identifiable triggers which system, these signals then need to be translated into
might be used to inform disaster management activation meaningful rainfall depths or water levels which can then
responses. be related to real world conditions. All gauges will require
periodic maintenance to ensure they are functioning as
The organisation also possess a series of flood maps expected. In addition to the maintenance of mechanical/
depicting flooding from a variety of flood trigger levels digital infrastructure of each gauge the numerical
and covering all major waterways and at risk communities. translations embedded into the Enviromon system should
These maps have been developed following a series of flood also be periodically checked.
study upgrades undertaken by the Sunshine Coast Council
prior to de-amalgamation. These flood maps should be Council has identified flood triggers for some telemetry
presented online. gauges to inform disaster management activation levels.
These triggers currently correspond to the design event
10.1.2 Disaster management triggers flood levels anticipated at each telemetry gauge location for
the 2 year (minor), 10 year (moderate), 100 year (Major)
Setting disaster management triggers is a two stage process.
and 500 year (Extreme) average recurrence interval flood
The first stage being the correlation of the recorded (real-
events.
time) water level (or rainfall intensity) for a gauge site with
an equivalent design flood event reference (i.e. Minor, It is recommended that flood triggers to be set for all
Moderate, Major or Extreme). This reference enables the telemetry gauges and that corresponding on-ground
magnitude of the event to be quantified and communicated responses and impacts be identified for each trigger level.
effectively. The second stage is then to be able to communicate
the likely consequences to the community of each of the 10.1.3 Disaster management redundancy
design event levels. Consequences may include inundated
roads, inundated properties, isolated communities etc. To effectively advise on flood related conditions during
The identification of possible/likely consequences from a flood event requires access to readings or observations
each level of flood event can be informed by desktop of current water levels and the ability to translate these
analysis and anecdotal advice received from individuals readings into meaningful advice to other stakeholders.
in the community and stakeholders within Council and Standard procedures for monitoring river/creek water
associated emergency services. Appropriate responses to levels and catchment rainfall are dependent upon the
each of the consequences identified are the responsibility functionality of each of the rainfall and river height gauges,
of each emergency services agency. the ability to receive signals from each gauge, the ability
to translate these readings into meaningful references and
For efficiency of providing timely advice and the ability to communicate these references to a broader
communications during a flood event it is recommended stakeholder group. To fulfil these standard procedures
that the flood triggers and associated consequences be requires a number of critical systems to be functional.
determined prior to an event.
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Available flooding information should be fully redundant The Enviromon system and its traditional interface are not
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in the event of a disruption to access to council’s network considered to be user friendly and have not been designed
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however it can be dependent on other technology. It is for infrequent or intuitive use. Hence, a number of local
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recommended that redundancy options and alternate governments have begun to explore additional software
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operating procedures for each system associated with flood systems that provide greater accessibility, interpretation
monitoring and for providing flood advice to the LDMG and warning capabilities of Enviromon collected data.
be developed to reinforce the process of providing flood Such systems may improve user access and the quality of
advice in the event of a failure to one of these systems. advice provided during flood events. It is recommended
that Council consider options to utilise additional
10.1.4 Real-time flood monitoring software options to enhance the functionality and improve
accessibility to Enviromon readings.
To fulfil an advisory role with regards to flooding
during a disaster management activation will require
10.2 Disaster Management Activations
an understanding of the real-time conditions being
experienced in the waterways and catchments within A local disaster coordination centre will typically be
the Council area. The standard procedure/system for activated prior to an impending flood event based upon
obtaining this information is currently via the Bureau of advice received from the Bureau of Meteorology (BoM).
Meteorology’s Enviromon system which is hosted within However, during the event it will be expected that local
Council and can be accessed via Council’s internal network conditions are being monitored by council officers
or by remote login to a stand-alone PC. supporting the coordination centre and that forecasts from
the BoM are also being interpreted with regards to local
Varying levels of user proficiency are required to access
conditions. This requires a good working knowledge of
and manage the Enviromon system. It is recommended
available flood map products and the BoM’s Enviromon
that a broad user base be trained in a basic proficiency
system by a sufficient number of trained officers to be able
which would enable them to independently login to
to cover a rotating shift over at least 24 hours.
Enviromon and view relevant rainfall or water level
readings for gauges within the Council area. A smaller 10.2.1 Trained staff resources
subset of this user group should also be trained in more
advanced management of the Enviromon system. It is Interpreting real-time flood information requires a basic
also recommended that a single point of contact (with a understanding of hydrology (rainfall runoff) and hydraulics
hierarchy of alternative contacts) should also be established (water conveyance) and the ability to translate observed
to ensure coordinated management of the Enviromon or forecasted information into expected outcomes based
system and communications with Bureau of Meteorology upon the know characteristics of local catchments and
(BoM). waterways. Varying levels of understanding of hydrologic
concepts such as rainfall intensity and duration, runoff
A basic working knowledge of Enviromon amongst times of concentration and rainfall volume would be
sufficient staff from across the organisation is required expected. Similarly varying levels of understanding of
to be able to cover a rotating shift over at least 24 hours. hydraulic concepts such as rate of rise, backwater effects,
This assumes an eight hour shift with a one hour handover flood waves and tailwater conditions would be expected.
between shifts. To cover these shifts without duplication
therefore requires a total of four trained staff.
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In addition to the interpretation of real-time information At least three officers in Council should possess this overall
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staff would be expected to be capable of effectively understanding. It is recommended that to provide relevant
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communicating an accurate interpretation to the officers with these understandings the flood specific
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stakeholders of a disaster coordination centre. The procedures be documented in a simple guideline.
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organisation should have 4 trained officers who can
provide interpretation of real-time flood information via 10.3 Community Awareness
monitoring software such as BoM’s Enviromon or other
accessible sources. It is generally accepted that a community’s resilience to
flooding can be significantly improved, in lieu of flood
It is also recommended that officers actively participate mitigation, via improved community awareness. Improved
in disaster management training exercises to familiarise community awareness of potential flooding conditions can
themselves with the protocols and expectations of a improve preparedness, reduce loss and avoid inappropriate
disaster coordination centre. Flood-specific training could actions during a flood event that may expose residents to
be conducted independently of other broader disaster further risk. A dedicated community awareness program aims
management training opportunities to further refine to promote awareness of flood risks and strategies to manage
specific flooding related skills. or minimise these risks. For instance, initiatives could include
awareness for drivers attempting flooded crossings.
10.2.2 Overall understanding of flood specific
procedures Council’s website includes some general information
related to promoting an awareness of flooding. The
In addition to possessing a basic technical competency in website includes a brief description of types of flooding
hydrologic concepts and a general understanding of local and references to a variety of flood mapping resources
disaster management practices, it is also recommended that including river and storm maps and flood specific layers
relevant officers possess an overall understanding of their displayed within Council’s Interactive Mapping portal.
role and flooding specific procedures/services expected
The organisation periodically promotes flood related
to be provided during a flood event. This may include
services and messages to the community. It is recommended
confirming an understanding of: how to prepare a situation
the organisation to undertake a dedicated community
report; the frequency expected to provide advice; the format
awareness program at least every two years.
of the advice provided; the sources of reference to inform
advice; and knowing who to provide the advice to.
10.4 Flood Mitigation
Flood mitigation represents an infrastructure response to
improving community flood resilience. As with all capital
works programs, the delivery of flood mitigation requires
long term planning and prioritisation. Prioritisation of
mitigation options and investment may be influenced by
considering who the main beneficiaries of the works are and
how the works are to be funded. Flood mitigation works may
include upgrades to culverts, bridges and road elevations to
improve the flood immunity of a roadway or to improve the
conveyance of flood waters and reduce the potential for flood
waters to back up and cause damage or nuisance.
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Council has recently undertaken flood mitigation works in • Review the gauge translations in Enviromon every
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Pomona (2016) and near Daintree Estate (2015) to improve two years to ensure accurate real world conditions are
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the resilience of the local communities and residents who being reported.
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had been affected by recent flood events. Flood mitigation
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• Review standard procedures for receiving and
works for Ashgrove Drive Cooroy are currently underway
providing flood advice with the view to identify critical
in association with the Bruce Highway upgrade.
systems within this process. Identify redundancy
There is currently no documented strategy for flood options and alternative procedures in the event of
mitigation for this council. A flood mitigation strategy possible failures to critical systems.
helps to documents mitigation opportunities prioritises • Establish a user group with basic proficiency in the
these works and includes an implementation plan for their operation of the Enviromon system and a user group
delivery. It should act as a road map for future investment with advanced proficiency in the system.
in flood mitigation activities and facilitate improved
• Explore options to utilise additional software to
communications across all related stakeholders regarding
enhance the functionality and improve accessibility to
site selection and prioritisation of works.
Enviromon readings.
Forecasted increases in mean sea levels and rainfall
Disaster Activation
intensities associated with future climate scenarios may
require broad scale mitigation works to be considered if • Provide basic competency training in hydrologic
existing standards of service for trafficability and flood and hydraulic characteristics of the Noosa Council
immunity are to be maintained. A flood mitigation strategy catchments and waterways.
may also consider non-structural responses which opt to
• Provide specific flood disaster management training
redefine standards of service for vulnerable locations.
to relevant council officers or stakeholders to further
It is recommended that a flood mitigation strategy to be refine specific flooding related skills.
prepared including a detailed implementation plan for
• Ensure basic training has been provided to flood
prioritising and costing potential actions.
related officers on the procedures to follow during a
flood event.
10.5 Key initiatives –
Disaster management Community awareness
• Prepare and deliver a community flood awareness
The implementation plan will include initiatives that aim
program.
to achieve the following–
Flood mitigation
Disaster preparation
• Prepare a project scope outlining the desired structure
• Determine flood trigger levels for vulnerable
and outcomes for a Flood Mitigation Plan.
communities or vulnerable infrastructure items with
one (or more) of the Council’s radio telemetry gauges • Incorporate relevant recommendations from the
and document the likely associated consequences. Flood Mitigation Plan into Council’s overall 10 year
capital works program.
• Undertake regular maintenance of all radio telemetry
gauges.
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Implementation
and Review
Council aims to achieve the key initiatives of the Flood
Management Plan over a 5 year implementation period.
An implementation plan will be developed, that describes
priority actions and identifies responsibilities and
timeframes.
Progress on the Flood Management Plan will be reviewed
and reported to Council annually. The implementation
plan will be updated to reflect the review process.
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Glossary
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These definitions are taken from within this document and
from the Queensland Floods Commission of Inquiry Final
Report Queensland Floods (2012)
Annual Exceedance Probability (AEP) means the
chance of a flood of a given or larger size occurring in any
Defined flood event (DFE) is the flood event adopted by
a local government for the management of development in
a particular locality.
Defined flood level (DFL) is the level of a flood that
would occur during a defined flood event (DFE).
one year, usually expressed as a percentage. For example,
if a peak flood discharge of 500m3/s has an AEP of 5%, Flood map is a map which depicts the extent of a
it means that there is a 5% chance (1 in 20 chance) of a particular flood or floods, for example the 1% AEP flood
500m3/s or larger event occurring in any one year (see or a historical flood.
ARI).
Flood study is a scientific investigation into flooding in a
Australian Height Datum (AHD) means a common particular area, usually the catchment of a river system. It
national surface level datum approximately corresponding may involve hydrologic and hydraulic investigations and a
ton mean sea level. statistical analysis of the frequency with which floods have
occurred in the past.
Average Recurrence Interval (ARI) means the long
term average number of years between the occurrence Flow velocity means the flow rate of water over an area
of a flood as big as, or larger than, the selected event. For and is measured in cubic metres per second (m3/s) or
example, floods with a discharge as great as, or greater cumecs.
than, the 20 year ARI flood event will occur on average
Hydraulic studies/investigations (with respect
once every 20 years. ARI is another way of expressing the
to flood studies) means an analysis that estimates the
likelihood of occurrence of a flood event (see AEP).
behaviour of flood flow (that is, flow rate, velocity, depth
Building controls are standards that regulate the and extent of inundation) as it passes through a floodplain
construction of buildings, as distinct from planning (see flood study).
controls that regulate where buildings are constructed.
Hydrologic model (runoff routing model) uses rainfall
These standards can be found in the Building Code of
data and estimates of the proportion of the rainfall which
Australia and the Queensland Development Code, or in
turns into runoff and the time which the runoff from each
planning instruments.
part of the catchment takes to flow into the stream to
estimate flow in the stream over time.
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Hydrologic study/investigation (with respect to flood
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studies) means a study aimed at determining rainfall and
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associated stream flows in a range of scenarios (see flood
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study).
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Hydrology is the term given to the study of the rainfall
and runoff process; in particular, the evaluation of peak
flows, flow volumes and the derivation of hydrographs for
a range of floods.
Overlay means an extra layer of assessment in planning
schemes. The provisions of an overlay code are usually
triggered by overlay maps that depict extra information to
the information on the zoning maps.
Planning scheme is a local planning instrument for
regulating development in Queensland. Planning schemes
regulate what development must be assessed before it can
be undertaken, the type of assessment required and the
criteria used in an assessment in each council region. They
also contain codes with which self-assessable development
must comply.
Bathymetric survey is information relating to river
and lake bed surfaces. Bathymetric survey is typically
undertaken below normal water surface levels. (see chapter
7 of this document)
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