Albany Creek Flood Study Volume 1 of 2
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Albany Creek Flood Study Volume 1 of 2 Flood Study Report Disclaimer The Brisbane City Council (“Council”) has prepared this report as a general reference source only and has taken all reasonable measures to ensure that the material contained in this report is as accurate as possible at the time of publication. However, the Council makes no representation and gives no warranty about the accuracy, reliability, completeness or suitability for any particular purpose of the information and the user uses and relies upon the information in this report at its own sole risk and liability. Council is not liable for errors or omissions in this report. To the full extent that it is able to do so in law, the Council disclaims all liability, (including liability in negligence), for any loss, damage or costs, (including indirect and consequential loss and damage), caused by or arising from anyone using or relying on the information in this report for any purpose whatsoever. Flood information and studies regarding the Brisbane City Council local government area are periodically reviewed and updated by the Council. Changes may be periodically made to the flood study information. These changes may or may not be incorporated in any new version of the flood study publication. It is the responsibility of the user to ensure that the report being referred to is the most current and that the information in such report is the most up-to-date information available. This report is subject to copyright law. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968. Albany Creek Flood Study Volume 1 of 2 Prepared by Cardno Pty Ltd Prepared for Brisbane City Council July 2014 Level 11 Green Square North Tower 515 St Paul’s Terrace Fortitude Valley Qld 4006 Locked Bag 4006 Fortitude Valley Queensland 4006 Australia Telephone: (07) 3369 9822 Facsimile: (07) 3369 9722 International: +61 7 33699822 [email protected] www.cardno.com.au Notice The Brisbane City Council (“Council”) has provided this report as a general reference source only and the data contained herein should not be interpreted as forming Council policy. All reasonable measures have been taken to ensure that the material contained in this report is as accurate as possible at the time of publication. However, the Council makes no representation and gives no warranty about the accuracy, reliability, completeness or suitability for any particular purpose of the information and the user uses and relies upon the information in this report at its own sole risk and liability. Council is not liable for errors or omissions in this report. To the full extent that it is able to do so in law, the Council disclaims all liability, (including liability in negligence), for any loss, damage or costs, (including indirect and consequential loss and damage), caused by or arising from anyone using or relying on the information in this report for any purpose whatsoever. Document Control: Issue Date of Amdt Prepared By Reviewed By Approved for No. Issue (Author/s) Issue (Project Director) Initials RPEQ Number Initials RPEQ Number Initials and Signature and Signature Final July 2014 9408 Albany Creek Flood Study 2014 For Information Only – Not Council Policy Table of contents EXECUTIVE SUMMARY 1 PART A – MODEL CALIBRATION 3 1.0 INTRODUCTION 4 1.1 Purpose 4 1.2 General 4 1.3 Study Elements 5 2.0 AVAILABLE DATA 6 2.1 Hydrographic Data 6 2.1.1 Continuous Rainfall Gauges 6 2.1.2 Maximum Height Gauges (MHGs) 6 2.2 Topographic Data 6 2.3 Hydraulic Structures 7 3.0 MODEL DESCRIPTIONS 8 3.1 Introduction 8 3.2 Hydrologic Model 8 3.3 Hydraulic Model 10 4.0 CALIBRATION 12 4.1 Calibration Events 12 4.1.1 Hydrologic Model Calibration 12 4.1.2 Hydraulic Model Calibration 13 4.2 May 1996 Event 13 4.3 May 2009 Event 14 4.4 October 2010 Event 14 5.0 VERIFICATION 15 5.1 Verification Events 15 5.2 Structure Verification 15 5.3 Sensitivity to Model Parameters 17 5.4 Calibration and Verification Summary 17 PART B – DESIGN EVENT MODELLING 18 6.0 INTRODUCTION 19 7.0 MODEL DATA 20 7.1 Design Rainfall 20 7.2 Tailwater Conditions 20 7.3 Topographic and Structure Data 21 7.4 Land Use 22 8.0 DESIGN EVENT MODELLING 23 8.1 Australian Rainfall and Runoff 23 Albany Creek Flood Study 2014 i For Information Only – Not Council Policy 8.2 Duration Independent Storm (DIS) 23 9.0 HYDROLOGIC MODELLING 27 9.1 Comparison of Peak Discharges 27 9.2 Hydrologic Model Results 28 10.0 HYDRAULIC MODELLING 30 10.1 Model Setup 30 10.2 Modelling Ultimate Waterway Conditions 30 10.2.1 Existing Waterway Corridors 30 10.2.2 Minimum Riparian Vegetated Corridor 31 11.0 FINAL MODEL RESULTS 32 11.1 Flood Levels and Discharges 32 11.2 Discussion of Results 35 11.3 Flood Mapping 36 12.0 REFERENCES 37 Albany Creek Flood Study 2014 ii For Information Only – Not Council Policy LIST OF APPENDICES APPENDIX A PART A – MODEL CALIBRATION Figures A1 Extent of Study A2 Locations of Rainfall and Maximum Height Gauges A3 RAFTS Model A4 Cumulative Rainfall, May 1996 A5 Cumulative Rainfall, May 2009 A6 Cumulative Rainfall, October 2010 A7 IFD Chart, May 1996 A8 IFD Chart, May 2009 A9 IFD Chart, October 2010 A10 RAFTS vs TUFLOW Hydrograph at Mouth, May 1996 A11 RAFTS vs TUFLOW Hydrograph at Mouth, May 2009 A12 RAFTS vs TUFLOW Hydrograph at Mouth, October 2010 A13 Albany Creek Catchment Land Uses – 1996 A14 Albany Creek Catchment Land Uses – 2009/2010 A15 Albany Creek Catchment Land Uses – Ultimate A16 Impact of Manning’s n on 100 Year Flood Levels A17 Flood Frequency Analysis – Albany Creek Road A18 Comparison of Peak Discharges – Albany Creek Road A19 Comparison of 100 Year ARI Water Surface Profiles A20 Result Output Locations Tables A1 RAFTS Model Details – 1996 A2 RAFTS Model Details – 2010 A3 RAFTS Model Details – Ultimate APPENDIX B HYDRAULIC STRUCTURE REFERENCE SHEETS APPENDIX C ADDENDUM REPORT – CLIMATE CHANGE ANALYSIS APPENDIX D PEER REVIEW OF ALBANY CREEK FLOOD MODELS Albany Creek Flood Study 2014 iii For Information Only – Not Council Policy LIST OF TABLES Table 2.1: Continuous Rainfall Data Table 2.2: Maximum Height Gauge Data Table 2.3: Hydraulic Structure Details Table 3.1: Land Use Types Table 3.2: Old Northern Road Culvert Crossings Table 3.3: Manning’s n Values Table 4.1: Peak Flood Levels – May 1996 Event Table 4.2: Peak Flood Levels – May 2009 Event Table 4.3: Peak Flood Levels – October 2010 Event Table 5.1: Comparison of Hydraulic Model Structure Losses Table 7.1: South Pine River Peak Flood Levels at Albany Creek Mouth Table 7.2: Hydraulic Structure Blockages due to Fencing Table 8.1: Design Event Frequency Table 8.2: Duration Independent Storm Factors Table 9.1: Time of Concentration Calculations Table 9.2: Comparison of 100 Year Peak Discharges Table 9.3: RAFTS Model 100 Year Peak Discharges Table 9.4: 100 Year Peak Discharges – RAFTS and TUFLOW Table 11.1: Peak Flood Levels – Ultimate Scenario Table 11.2: Peak Discharges – Ultimate Scenario Table 11.3: CRC-FORGE Rainfall Depths Table 11.4: Peak Flood Levels – Ultimate Scenario Table 11.5: Peak Discharges – Ultimate Scenario Albany Creek Flood Study 2014 iv For Information Only – Not Council Policy EXECUTIVE SUMMARY Albany Creek is located in the northern part of Brisbane. The catchment is split between the Brisbane City Council (BCC) and Moreton Bay Regional Council (MBRC) local government areas. The total area of the catchment is approximately 888 hectares. The creek outlets into the South Pine River just downstream of Leitchs Crossing at Brendale. Brisbane City Council (BCC) commissioned Cardno to carry out a flood study of Albany Creek, comprising: · an XP-RAFTS hydrologic model; and · a TUFLOW 1D/2D hydraulic model. BCC defined the study area for the hydraulic model to be downstream of Streisand Drive in McDowall, and Country Club Drive and Sunningdale Court in Albany Creek, as shown in Figure A1 (in Appendix A). Based on the available rainfall and maximum height gauge (MHG) data, the following three events were selected for the calibration of the hydrologic and hydraulic models: · May 1996; · May 2009; and · October 2010. Good agreement was generally achieved at all MHGs for all calibration events, with differences between the recorded and calculated flood levels within ±250 mm. The calibrated hydrologic and hydraulic models were used to analyse flood events with an average recurrence interval (ARI) from 2 years to 2,000 years. Design event modelling was carried out using the Australian Rainfall and Runoff temporal patterns. In addition, flood discharges for design events were estimated by undertaking a flood frequency analysis to determine flows in Albany Creek for a range of recurrence events. The discharges determined from the flood frequency analysis were then compared to the discharges calculated using duration independent storms synthesised as proposed in Morris (1996). Factors were derived for the synthetic storms to provide the best possible agreement between the peak flows predicted by the synthetic storms and the peak flows predicted by the flood frequency analysis. The hydraulic model was used to determine the peak flood levels along the creek for two scenarios: · existing waterway conditions; and Albany Creek Flood Study 2014 1 For Information Only – Not Council Policy · ultimate waterway conditions, including waterway corridors and a minimum vegetated riparian corridor. Maps are contained in Volume 2, showing: · peak flood levels and extent of inundation for the 2 to 100 year ARI flood events; and · peak flood depths for the 2 to 100 year ARI flood events.