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Use of LiDAR in Floodplain Managment


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Use of LiDAR in Floodplain Managment

  1. 1. The use of LiDAR in Floodplain Management Surveying & Spatial Sciences Institute Conference Brendan Nelson General Manager – Land Use Planning Queensland Reconstruction Authority8 June 2012
  2. 2. Presentation OutlineLiDAR in supporting the activities of the QueenslandReconstruction Authority • Prepare – Floodplain Management • Respond – Emergency Management • Commission of Inquiry Recommendations
  3. 3. The AimTo ensure the effective and efficient recovery of Queensland so that Queensland and Queenslanders emergestronger and more resilient.We achieve this by focussing onhow we respond, recover and prepare for natural disasters. These are lessons that can ensure positive change and resilient communities .
  4. 4. 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
  5. 5. Planning for stronger, moreresilient floodplainsTo assist Councils to ensure thatfloodplain management is addressedthrough 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
  6. 6. 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
  7. 7. 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.
  8. 8. 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 Informationover a matter of months, created Websitemaps covering most of Queensland.CoI Final Report, March 2012, pg 67
  9. 9. Alluvial Soils & Pre-Clear Vegetation Layer
  10. 10. 2011 Flood Event – Satellite Imagery overAlluvial Soils & Pre-Clear Vegetation Layer
  11. 11. Contours from the 1 second DEM(Best available elevation data)
  12. 12. Interim Floodplain Overlay Assessmentdetermined by DERM cartographers from all inputs
  13. 13. 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
  14. 14. Sub-basin wide approachFit for purposeacross thecatchment• 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
  15. 15. 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
  16. 16. Prior to the capture program best available contours were 10m. LiDAR provides 0.25m, DEM and high quality aerial resolution
  17. 17. Councils may choose to use theQldRA’s maps of the 2010/2011flood [to regulate development].CoI Final Report, March 2012, pg 66
  18. 18. IFAO (Level 1) for Roma with the 2012 actual flood event
  19. 19. Combining level 1 with detailed information Lockyer Valley Regional Council • Amalgamation of Council’s Defined Flood Event and QldRA’s Interim Floodplain Mapping
  20. 20. Level 2 Investigations completed to date based on dataavailable St George Surat Taroom Kilkivan Mareeba Black River Quilpie QRA actively working through another 22 Level 2 investigations
  21. 21. 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 approachWhat 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
  22. 22. 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
  23. 23. 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
  24. 24. 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
  25. 25. 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
  26. 26. 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
  27. 27. 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
  28. 28. 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?
  29. 29. 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
  30. 30. 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)
  31. 31. 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
  32. 32. 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
  33. 33. St George – 2012 event comparisonHigh correlation within town and north ofgauging stations – accurate model ofactual event
  34. 34. St George – 2012 event comparisonLess correlation in rural areas south of town & gauging stations –due to flood slope assumptions & influence of levees
  35. 35. Commission of Inquiry ReportFinal Report March 16State Government committed toimplementing all recommendations177 Recommendations across 17 chaptersincluding the following of relevance to landuse planning:-Chapter 2 Floodplain managementChapter 3 Planning frameworkChapter 7 Development and flood considerationsChapter 8 Development assessment in practiceChapter 9 Building controlsChapter 11 Buy-backs and land swaps
  36. 36. 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
  37. 37. Geoscience Qld’s Australia Floodcheck
  38. 38. National Flood Information Database
  39. 39. Flood risk information portal
  40. 40. 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