PATERSON RIVER FLOOD STUDY VACY TO HINTON PUBLIC EXHIBITION September 2016 Level 2, 160 Clarence Street Sydney, NSW, 2000 Tel: 9299 2855 Fax: 9262 6208 Email: [email protected] Web: www.wmawater.com.au PATERSON RIVER FLOOD STUDY SEPTEMBER, 2016 Project Project Number Paterson River Flood Study 114084 Client Client’s Representative Maitland City Council Ian Shillington (MCC) Port Stephens Council Michael Osborne (PS) Dungog Council Paul Minnet (DSC) Author Prepared by Dan Morgan Rhys Hardwick Jones Date Verified by 5 September 2016 Revision Description Distribution Date 1 Draft Report Council clients, OEH, SES May 2016 2 Draft Report Council clients, OEH, SES July 2016 3 Draft Report Public Exhibition September 2016 PATERSON RIVER FLOOD STUDY TABLE OF CONTENTS PAGE TERMINOLOGY USED IN REPORT ........................................................................................... i FOREWORD .............................................................................................................................. ii EXECUTIVE SUMMARY ........................................................................................................... iii 1. INTRODUCTION ........................................................................................................ 7 1.1. Background ................................................................................................ 7 1.2. Objectives ................................................................................................... 7 2. BACKGROUND ......................................................................................................... 8 2.1. Study Area .................................................................................................. 8 2.2. Historical Flooding ...................................................................................... 8 3. AVAILABLE DATA .................................................................................................. 10 3.1. Topographic Data ..................................................................................... 10 3.2. Bathymetric Survey................................................................................... 10 3.3. Levee Survey............................................................................................ 10 3.4. Flood Level Survey ................................................................................... 10 3.5. Stream Gauges ........................................................................................ 11 3.6. Rainfall Stations ........................................................................................ 14 3.7. Suitable Events for Calibration and Verification ........................................ 17 3.8. Design Rainfall ......................................................................................... 20 3.9. Previous Studies ....................................................................................... 20 4. COMMUNITY CONSULTATION ............................................................................... 22 4.1. Information Brochure and Survey ............................................................. 22 4.2. Community Responses ............................................................................. 22 5. APPROACH ............................................................................................................. 24 6. HYDROLOGICAL MODEL ....................................................................................... 25 6.1. Introduction ............................................................................................... 25 6.2. Sub-catchment delineation ....................................................................... 25 6.3. Impervious Surface Area .......................................................................... 25 6.4. Model Parameters .................................................................................... 26 6.5. Rainfall Losses ......................................................................................... 26 7. HYDRAULIC MODEL ............................................................................................... 27 7.1. Introduction ............................................................................................... 27 7.2. TUFLOW Hydraulic Model ........................................................................ 27 7.3. Boundary Locations .................................................................................. 27 7.4. Mannings ‘n’ Roughness .......................................................................... 29 7.5. Rivers ....................................................................................................... 30 7.6. Levees, Roads and Railway ..................................................................... 30 7.7. Hydraulic Structures ................................................................................. 30 8. CALIBRATION ......................................................................................................... 32 8.1. Objectives ................................................................................................. 32 8.2. Methodology ............................................................................................. 32 8.3. Rainfall Losses (WBNM) ........................................................................... 33 8.4. Stream Routing Parameter (WBNM) ......................................................... 33 8.5. Manning’s ‘n’............................................................................................. 33 8.6. Calibration Results.................................................................................... 34 9. FLOOD FREQUENCY ANALYSIS ........................................................................... 39 9.1. Overview .................................................................................................. 39 9.2. Gauges and Rating Curve ........................................................................ 39 9.3. Methodology ............................................................................................. 39 10. DESIGN EVENT MODELLING ................................................................................. 43 10.1. Overview .................................................................................................. 43 10.2. Upstream Inflows ...................................................................................... 43 10.3. Critical Duration ........................................................................................ 44 10.4. Losses ...................................................................................................... 44 10.5. Coincident Hunter River Flooding ............................................................. 44 10.6. Hunter River Inflows and Tailwater ........................................................... 45 10.7. Design Flood Modelling Results................................................................ 46 11. SENSITIVITY ANALYSIS ......................................................................................... 59 11.1. Overview .................................................................................................. 59 11.2. Climate Change ........................................................................................ 59 11.3. Sensitivity Analysis Results ...................................................................... 60 12. RECOMMENDATIONS ............................................................................................ 63 13. REFERENCES ......................................................................................................... 64 LIST OF APPENDICES APPENDIX A: Glossary of Terms APPENDIX B: Calibration Figures APPENDIX C: Design Flood Mapping APPENDIX D: Preliminary Planning Maps with 20% Increase in Rainfall Intensity LIST OF DIAGRAMS Diagram 1: Flood Study Process ............................................................................................... 24 Diagram 2: Provisional “L2” Hydraulic Hazard Categories (Reference 1) .................................. 51 LIST OF PHTOGRAPHS Photo 1 – Phoenix Park Road 2015 .......................................................................................... 22 Photo 2 – Morpeth Bridge 2015 ................................................................................................ 22 Photo 3 - Dunmore Bridge 2015 ................................................................................................ 22 Photo 4 - Dunmore Bridge 2015 ................................................................................................ 22 Photo 5 – Martins Creek during 2015 flood ............................................................................... 22 Photo 6 – Martins Creek after 2015 flood .................................................................................. 22 Photo 7 – Paterson Road Bridge ............................................................................................... 30 Photo 8 – Vacy Bridge .............................................................................................................. 30 Photo 9 – Road Culverts Mindaribba ......................................................................................... 31 LIST OF TABLES Table 1 – BOM Flood Classifications 9 Table 2 – Historical Flood Events 9 Table 3 – Stream Gauges 11 Table 4 – Peak Stage Heights (m) 13 Table 5 - Continuous