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Use of LiDAR in Floodplain Managment
1. The use of LiDAR in Floodplain Management
Surveying & Spatial Sciences Institute Conference
Brendan Nelson
General Manager – Land Use Planning
Queensland Reconstruction Authority
8 June 2012
2. Presentation Outline
LiDAR in supporting the activities of the Queensland
Reconstruction Authority
• Prepare – Floodplain Management
• Respond – Emergency Management
• Commission of Inquiry Recommendations
3. The Aim
To ensure the effective and
efficient recovery of
Queensland so that
Queensland and
Queenslanders emerge
stronger and more resilient.
We achieve this by focussing on
how we respond, recover and
prepare for natural disasters.
These are lessons that can
ensure positive change and
resilient communities .
4.
5. Floodplain Management
• 210 towns/suburbs affected by flood
• Further major flooding in 2012 – with
new highest recorded levels
• Critical infrastructure impacted
• Planning scheme review - 65% do not
contain any flood mapping
• Flooding investigation is often applicant
responsibility
• Catchments do not correlate with local
government boundaries
• New building codes will promote
resilience in houses
• Commission of Inquiry investigated
2010/2011 floods and recommended
wide-ranging changes
6. Planning for stronger, more
resilient floodplains
To assist Councils to ensure that
floodplain management is addressed
through land use planning.
Delivers a Toolkit
– Part 1 – Interim measures
– Part 2 – Long term solutions
– State-wide floodplain mapping
– Guide new flood investigations
– Specific guidance for land use An Integrated Approach across a
responses range of disciplines - Project
focuses on Land Use Planning
7. Flood Mapping – Needs to be fit for purpose
Not all parts of Qld
need a comprehensive
flood study.
CoI Final Report, March 2012, pg 54
8. IFAO Pilot Project - Dawson River Sub-basin
10m Contours LandSat Gauging Heights
Pre-cleared Stream Orders Aerial for towns
vegetation 5–9
The IFAO represents a spatial extent of Queensland Floodplains. It identifies an area
where flooding can be expected to occur. It does not represent an AEP.
9. State-wide mapping
• 129 Sub-basins across Queensland
• 118 sub-basins have been mapped
to date (within 8 months)
• In total 99.3% of the State has been
assessed for floodplains
• 26.6% identified within a floodplain
• 8,875 map pages produced to date
(A3 @1:50,000 scale)
• Using more than 35 cartographers
• Largest mapping exercise across the
country in a long time
Released publically for free
download in GIS format –
Working with DERM, the QldRA has Government Information
over a matter of months, created Website
maps covering most of Queensland.
CoI Final Report, March 2012, pg 67
14. Flood Investigation Guidance
Level 1 Level 2 Level 3
As per Part 1 Guideline Mid-level Investigation Comprehensive Flood Study
Locally Verified QldRA mapping Standard Data Inputs Detailed Data Inputs
+ + +
Flood Level Flood Frequency Analysis Computer Modelling
investigations = =
= Basic Hazard Mapping, incl. Detailed Information, incl. Hazard
Areas of Inundation + Local flood height & velocity + AEPs Mapping + AEPs
levels
• Local Governments select the combination of flood investigations appropriate for their circumstances
15. Sub-basin wide approach
Fit for purpose
across the
catchment
• Level 1
• Level 2
• Level 3
Flood studies should, ideally, be
commissioned for whole catchments.
Barron River Sub-basin CoI Final Report, March 2012, pg 56
16. LiDAR program
• QldRA recognises that the outputs of
LiDAR capture are crucial to further
investigations (Level 2 and Level 3)
• Baseline data can take 1/3 off the
cost of completed studies
• Data enables basic hazard maps to be
prepared and help inform Land Use
Planning and Emergency
Management
• Inland towns project has seen 80
towns captured
• QldRA have worked with EMQ to
capture additional 70 inland flood
risk towns this year to support
further flood investigations for CoI
response
17. Prior to the capture program best available contours were 10m.
LiDAR provides 0.25m, DEM and high quality aerial resolution
18. Councils may choose to use the
QldRA’s maps of the 2010/2011
flood [to regulate development].
CoI Final Report, March 2012, pg 66
19. IFAO (Level 1) for Roma with the
2012 actual flood event
20. Combining level 1 with detailed information
Lockyer Valley
Regional Council
• Amalgamation
of Council’s
Defined Flood
Event and
QldRA’s Interim
Floodplain
Mapping
21. Level 2 Investigations completed to date based on data
available
St George Surat Taroom Kilkivan
Mareeba Black River Quilpie
QRA actively working through another 22 Level 2 investigations
22. Where could a Level 2 be undertaken?
• Generally for populations under 5000
• Areas with low development/growth pressures
• Few structural controls impacting on flows
• Where Council resources are limited
• Contributes to sub-basin wide approach
What can a Level 2 be used for?
• Tailored to land use planning purposes
• Considers probability + consequence
• Can be prepared in-house (no
consultant/computer modelling required)
• Local verification critical
• Use planning evaluation to develop land use
strategies and planning scheme responses
23. Flood Investigation Level 2
• Capture contour information – via
LiDAR
• Obtain stream flow data
• Select flood(s) to investigate
• Perform Flood Frequency Analysis to
understand AEPs
• Map selected flood height across
town using DEM
• Apply flood slope calculated from
event data – using GIS-based
techniques
• Add velocity information It is not feasible, nor is it
• Prepare flood hazard map necessary, for sophisticated flood
mapping to be completed on a
state-wide basis.
CoI Final Report, March 2012, pg 67
24. LEVEL 2 Case Study - Mareeba – Barron River
• Fit-for-purpose flood investigation
approach – Level 2 investigation
• Tailored to land use planning purposes
• Worked with TRC using their data
• Flood historic data obtained via DNRM
• Assigned an AEP per flood occurrence to
develop hazard map for selected flood(s)
• Considers probability + consequence
• Can be prepared in-house (no computer
modelling required)
• Local verification critical
• Planning evaluation then use to inform
land use strategies and planning scheme
responses
25. Steps 1 & 2 – Flood Frequency Analysis
• Stream flow information - DERM HYDSTRA database
• Mareeba gauging station data available since 1915
• Compute AEP for all floods using basic formulae (Log Pearson III method)
• Select flood to investigate
– February 2000 flood selected for Mareeba (highest recorded of 12.4m at gauge & peak
discharge approx. 110,000ML/day) – just under AEP 1 in 100 years
– Myola gauging station downstream recorded large floods in 1911 & 1914 – including
these floods, AEP 1 in 100 year reduces to between 1 in 20 & 1 in 50 year at Myola
gauging station
Annual
Exceedence Peak Discharge Monte Carlo 90% quantile
Probability (1 in Y (ML/day) probability limits
years)
10 65045 55973 76394
20 81771 69774 99766
50 101969 84739 135053
100 115784 93527 165109
200 128366 100297 196093
500 143207 106875 241734
1000 153168 110504 279031
26. Step 3 – Mapping the Data
• LiDAR contour information obtained (0.25m contours) & mapped
• Spot flood heights from February 2000 event also included (highest recorded)
• Points of interest & cadastre overlaid
DERM Gauge Location
27. Step 4 – Initial Identification of Flood Hazard
• Land use zones of existing
planning scheme overlaid with
flood information
• Mapped 12.4m highest
recorded flood against
corresponding contour
• Also mapped 0.5m line below
flood height – for initial low
hazard zone (flood depth >
0.5m)
• Flood slope is based on linking
spot heights of highest recorded
event
28. Step 5 – Flood Hazard Map, subject to local verification
• Local verification gives additional information on key local characteristics,
such as impact of smaller watercourses
• Back water areas can be identified on the inundation map and be used for
low hazard
29. Planning Evaluation – Checklist
Checklist
1 What is the nature of the hazard in the floodplain and where does it occur?
Exposure 2 Where are existing settlements, infrastructure or other places of key social or
economic importance located within each hazard area?
3 Are the existing development commitments in the hazard areas?
4 Do these exposed places include vulnerable persons, or is the hazard (such as
flood depth or velocity) when it occurs so great that living in the area is of
significant concern?
Vulnerability 5 Is the area served by appropriate emergency management procedures?
6 Is the built form resilient to the hazard?
7 What is the community’s attitude to the hazard – are they resilient or vulnerable?
8 Is there an overriding economic or social need to continue living and working in
this area?
Tolerability 9 Are there existing or proposed structural controls for the area that will reduce the
hazard?
10 What are the community’s expectations regarding immunity and protection?
30. Develop planning scheme responses & implement non-
scheme planning measures based on Flood Hazard Map
• Land use responses:
• Add overlay code to manage
built form outcomes in risk areas
• Focus future land use zoning
(particularly rural residential and
residential zoning) away risk
areas
• Consider susceptible uses (e.g.
Nursing home)
• Implement non-scheme measures
(such as building controls) to
complement land use approach
31.
32. Imagery Acquisition Program
• 31 December 2010 – Easter 2011
• Aerial Photography for over 150 flood affected communities and 23 towns affected
by TC Yasi
• Coordinated with ADF (1 Topographic Squadron)
33. Imagery Acquisition Program
• Satellite imagery via activation of the International Charter
• First ever activation for Australia on 3rd Jan... & 2nd a month later
• 120 scenes from 12 different platforms
34. Emergency Response – St George
• 2012 flooding in St George was highest ever
• QRA were already undertaking work with
Balonne – Level 2 investigations
• QRA asked to prepared flood scenarios for
range of flood peaks based on BoM
predictions
• Flood scenarios assisted the State Disaster
Images – Lyndon Mechielson (AP)
Management Committee in announcing
evacuations to areas of the town
• Initially for a planning purpose but used also
for emergency management to illustrate
scenarios
• A low cost task in a short amount of time
with a high level of significance
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40. St George – 2012 event comparison
High correlation within town and north of
gauging stations – accurate model of
actual event
41. St George – 2012 event comparison
Less correlation in rural areas south of town & gauging stations –
due to flood slope assumptions & influence of levees
42. Commission of Inquiry Report
Final Report March 16
State Government committed to
implementing all recommendations
177 Recommendations across 17 chapters
including the following of relevance to land
use planning:-
Chapter 2 Floodplain management
Chapter 3 Planning framework
Chapter 7 Development and flood considerations
Chapter 8 Development assessment in practice
Chapter 9 Building controls
Chapter 11 Buy-backs and land swaps
43. QRA’s role in CoI response
• Qld Government has endorsed the State Gov response 7/6/12
• QRA will lead a number of recommendations based on extensive
work already completed and underway
• Prioritising where new flood studies will be initiated
• Undertaking flood investigations for up to 100 towns by end of 2012
• Finalising the Flood Model Planning Controls based on current code
• Developing the Qld Flood Portal to publish flood information
• Remaking the TSPP2/11
• Key agency in the SPP1/03 review
• Supporting many other recommendations being led by other
agencies
• Supporting Local Governments particularly those looking at specific
mitigation options
54. The Way Forward...
• There is no ‘one size fits all approach’ to disaster resilience
• The QldRA is pioneering a number of non conventional approaches to
planning and flood resilience
• Planning for disaster resilience is linked to technology and data
• LiDAR is the ‘DNA’ of many of the planning resilience projects
• Embrace and invest in technology and innovation – continuous
improvement of data quality and accessibility
• Strive for excellence and practicality rather than gold plating
• Consider open access to all mapping data – its working for the QldRA!
There’s still plenty of work to be done, but we are on our way to a
stronger more resilient Queensland
