BARDWELL CREEK 2D FLOOD STUDY REVIEW FINAL REPORT MARCH 2019 Level 2, 160 Clarence Street Sydney, NSW, 2000 Tel: (02) 9299 2855 Fax: (02) 9262 6208 Email: [email protected] Web: www.wmawater.com.au BARDWELL CREEK 2D FLOOD STUDY REVIEW FINAL REPORT MARCH 2019 Project Project Number Bardwell Creek 2D Flood Study Review 118004 Client Client’s Representative Bayside Council Debbie Fransen Pulak Saha Authors Prepared by Ben Oakley Richard Dewar Rhys Hardwick Jones Date Verified by 1 March 2019 Revision Description Distribution Date 1 Draft Report Bayside Council 13 Sep 2018 2 Draft Report for Public Exhibition Bayside Council 2 Nov 2018 3 Final Draft Bayside Council 8 Feb 2019 4 Final Bayside Council 1 Mar 2019 BARDWELL CREEK 2D FLOOD STUDY REVIEW TABLE OF CONTENTS PAGE LIST OF ACRONYMS ................................................................................................................. i FOREWORD ............................................................................................................................... i EXECUTIVE SUMMARY ............................................................................................................ ii 1. INTRODUCTION ........................................................................................................ 1 2. BACKGROUND ......................................................................................................... 2 2.1. Study Area ................................................................................................................ 2 2.1.1. Bardwell Creek ................................................................................................ 3 2.1.2. Wolli Creek ...................................................................................................... 3 2.1.3. M5 Motorway East ........................................................................................... 3 2.1.4. East Hill Railway Noise Wall ............................................................................ 3 2.2. Historical Flooding .................................................................................................... 3 2.2.1. Notable Features in Bardwell Creek................................................................. 6 2.2.2. Notable Features in Wolli Creek ...................................................................... 6 2.3. Previous Studies ....................................................................................................... 7 2.3.1. Wolli Creek, Bardwell Creek and Bonnie Doon Flood Study ............................ 7 2.3.2. Southern Bardwell Creek Drainage Study ........................................................ 7 2.3.3. Northern Bardwell Creek Piped Drainage and Overland Flow Analysis ............ 8 2.3.4. Update of Wolli Creek Pipe Drainage and Overland Flow Study ...................... 8 2.3.5. Cooks River Flood Study ................................................................................. 8 2.3.6. Wolli Creek Flood Study .................................................................................. 9 2.3.7. Overland Flow Flood Study for Hurstville, Mortdale and Peakhurst Wards..... 10 2.4. Community Consultation ......................................................................................... 11 3. AVAILABLE DATA .................................................................................................. 13 3.1. Overview ................................................................................................................. 13 3.2. Data Sources .......................................................................................................... 13 3.3. Topographic Data ................................................................................................... 14 3.4. Hydraulic Structures ................................................................................................ 15 3.5. Cross-Section Survey ............................................................................................. 16 3.6. WestConnex Stage 2: New M5 ............................................................................... 16 3.7. Pit and Pipe Data .................................................................................................... 17 3.8. Lusty Street Detention Tank .................................................................................... 17 3.9. NSW Tidal Planes Analysis ..................................................................................... 17 3.10. Historical Flood Level Data ..................................................................................... 18 3.11. Historical Rainfall Data ............................................................................................ 23 3.11.1. Overview ................................................................................................. 23 3.11.2. Rainfall Stations ............................................................................................. 24 3.11.3. Analysis of Daily Rainfall Data ....................................................................... 25 3.11.4. Analysis of November 1984 Rainfall Event .................................................... 26 3.11.5. Analysis of December 1992 Rainfall Event .................................................... 26 3.11.6. Analysis of February 1993 Rainfall Event ...................................................... 27 3.11.7. Analysis of January 1996 Rainfall Event ........................................................ 27 3.11.8. Analysis of October 2014 Rainfall Event ........................................................ 28 3.12. Design Rainfall Data ............................................................................................... 29 4. MODELLING METHODOLOGY ............................................................................... 30 4.1. Overview ................................................................................................................. 30 4.2. Hydrologic Model .................................................................................................... 30 4.3. Hydraulic Model ...................................................................................................... 30 4.4. Flood Frequency Analysis ....................................................................................... 31 4.5. Historical Event Calibration and Validation .............................................................. 32 5. HYDROLOGIC MODEL SETUP ............................................................................... 33 5.1. Introduction ............................................................................................................. 33 5.2. Sub-catchment delineation...................................................................................... 33 5.3. Impervious Surface Area ........................................................................................ 33 5.4. Rainfall Losses and WBNM Lag Parameters .......................................................... 34 6. HYDRAULIC MODEL SETUP .................................................................................. 35 6.1. TUFLOW ................................................................................................................ 35 6.2. Boundary Locations ................................................................................................ 35 6.2.1. Inflows ........................................................................................................... 35 6.2.2. Downstream Boundaries ................................................................................ 35 6.3. Surface Roughness ................................................................................................ 36 6.4. Hydraulic Structures ................................................................................................ 37 6.4.1. Buildings ........................................................................................................ 37 6.4.2. Fencing and Obstructions .............................................................................. 37 6.4.3. Bridges and Culverts ..................................................................................... 37 6.4.4. Surface and Sub-Surface Drainage Network ................................................. 38 6.4.5. Inlet Pits ......................................................................................................... 38 6.4.6. Road Kerbs and Gutters ................................................................................ 38 6.4.7. Pedestrian Underpasses Underneath M5 ...................................................... 39 6.4.8. Gross Pollutant Trap (GPT) ........................................................................... 39 6.4.9. Turrella Weir and Footbridge ......................................................................... 39 6.4.10. Sewer Line (SWSOOS) ................................................................................. 39 6.4.11. Hillcrest Avenue – Levee and Pipes............................................................... 40 6.5. Calibration Debris Blockage Assumptions ............................................................... 40 7. MODEL CALIBRATION ........................................................................................... 42 7.1. Objectives ..............................................................................................................