Parramatta River - Ryde Sub- Catchments Flood Study and Floodplain Risk Management Plan
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Parramatta River - Ryde Sub- Catchments Flood Study and Floodplain Risk Management Plan FLOOD STUDY REPORT Revision C 29 August 2013 Parramatta River - Ryde Sub-Catchments Flood Study and Floodplain Risk Management Plan FLOOD STUDY Revision C 29 August 2013 Sinclair Knight Merz ABN 37 001 024 095 100 Christie Street St Leonards NSW 2065 Australia Postal Address PO Box 164 St Leonards NSW 2065 Australia Tel: +61 2 9928 2100 Fax: +61 2 9928 2500 Web: www.globalskm.com The SKM logo trade mark is a registered trade mark of Sinclair Knight Merz Pty Ltd. Parramatta River - Ryde Sub-Catchments Flood Study COPYRIGHT: The concepts and information contained in this document are the property of Sinclair Knight Merz Pty Ltd. Use or copying of this document in whole or in part without the written permission of Sinclair Knight Merz constitutes an infringement of copyright. LIMITATION: The sole purpose of this report and the associated services performed by Sinclair Knight Merz Pty Ltd (SKM) is to document the development and verification of the hydrologic and hydraulic models for the definition of overland flooding behaviour in the City of Ryde Parramatta River Catchments study area, in the undertaking of a flood study for this area. The focus of this flood study is on the broad overland flooding behaviour in the study area, and hence localised drainage issues may not be represented. In preparing this report, SKM has relied upon, and presumed accurate, certain information (or absence thereof) provided by the Client and other sources. Except as otherwise stated in the report, SKM has not attempted to verify the accuracy or completeness of any such information. If the information is subsequently determined to be false, inaccurate or incomplete then it is possible that our observations and conclusions as expressed in this report may change. SKM derived the data in this report from a variety of sources. The sources are identified at the time or times outlined in this report. The passage of time, manifestation of latent conditions or impacts of future events may require further examination of the proposal and subsequent data analysis, and re-evaluation of the data, findings, observations and conclusions expressed in this report. SKM has prepared this report in accordance with the usual care and thoroughness of the consulting profession, for the sole purpose of the proposal and by reference to applicable standards, procedures and practices at the date of issue of this report. For the reasons outlined above, however, no other warranty or guarantee, whether expressed or implied, is made as to the data, observations and findings expressed in this report. This report should be read in full and no excerpts are to be taken as representative of the findings. No responsibility is accepted by SKM for use of any part of this report in any other context. This report has been prepared on behalf of, and for the exclusive use of, the City of Ryde, and is subject to, and issued in connection with, the provisions of the agreement between SKM and City of Ryde. SKM accepts no liability or responsibility whatsoever for, or in respect of, any use of, or reliance upon, this report by any third party. SINCLAIR KNIGHT MERZ I:\ENVR\Projects\EN02970\Deliverables\Reports\Flood Study\EN02970 Flood Study report Rev C Final.docx PAGE i Parramatta River - Ryde Sub-Catchments Flood Study Contents 1. Introduction 4 1.1. General 4 1.2. Purpose of this Flood Study 4 2. Background on Study Area 6 2.1. Catchment Description 6 2.1.1. Archer Creek Catchment 6 2.1.2. Denistone Catchment 6 2.1.3. Charity Creek Catchment 8 2.1.4. River Catchment 8 2.1.5. Gladesville Catchment 8 2.2. History of Flooding 9 3. Review of Available Data 12 3.1. Previous Studies 12 3.2. Stormwater Asset Data Base 13 3.3. Topographic Survey 13 3.3.1. Airborne Laser Survey 13 3.3.2. Ground Survey 13 3.3.3. Design and Works as Executed Drawings 13 3.4. Spatial Data 14 3.5. Rainfall Intensity-Frequency-Duration Data 14 3.6. Data on Historic Flood Events 14 3.6.1. Historic Event Rainfall Data 14 3.6.2. Observations of Historic Floods 15 4. Hydrologic Model Development 16 4.1. Model Selection 16 4.2. Model Extent 16 4.3. Stormwater Network Details 16 4.4. Sub-Catchment Data 18 4.5. Hydrologic Parameters 18 4.6. Design Rainfall 19 4.7. Limitations of the Model 19 5. Hydraulic Model Development 20 5.1. Model Selection 20 5.2. Configuration of Hydraulic Model 20 5.2.1. Extent and Structure 20 5.2.2. Model Topography 21 SINCLAIR KNIGHT MERZ I:\ENVR\Projects\EN02970\Deliverables\Reports\Flood Study\EN02970 Flood Study report Rev C Final.docx PAGE ii Parramatta River - Ryde Sub-Catchments Flood Study 5.2.3. Stormwater Pits 21 5.2.4. Stormwater Conduits and Open Channels 21 5.2.5. Building Polygons 21 5.2.6. Property Fencelines 22 5.2.7. Surface Roughness 22 5.2.8. Footbridges and Pipe Crossings 23 5.2.9. Floodways through Existing Buildings 23 5.3. Blockages 23 5.4. Boundary Conditions and Initial Conditions 24 5.4.1. Model Inflows 24 5.4.2. Tailwater Conditions 24 5.4.3. Initial Water Levels 24 5.5. Model Verification 24 5.5.1. Comparison to Observed Flood Depths 25 5.5.2. Comparison to Previous Studies 29 5.5.3. Conclusions on Model Verification 29 6. Estimation of Design Floods 32 6.1. Simulated Design Events 32 6.2. Flood Mapping 32 6.3. Flood Planning Area 32 6.4. Provisional Flood Risk Precinct Mapping 33 6.5. Discussion on Existing Flood Behaviour 34 6.6. Sensitivity Analysis 35 6.7. Impact of Climate Change on Flooding 37 6.7.1. Impacts due to Increased Rainfall and Sea Level 37 6.7.2. Impacts due to Sea Level Rise only 37 7. Identified Flooding Hot-Spots 39 7.1. Overview 39 7.2. Cobham Avenue, Melrose Park (Archer Creek Catchment) 39 7.3. West Ryde Town Centre (Denistone Catchment) 39 7.4. Gaza Road – Station Street – Federal Road, West Ryde (Denistone Catchment) 41 7.5. Falconer Street near Wattle Street, West Ryde (Charity Creek Catchment) 42 7.6. Industrial area at Mulvihill Road and Rhodes Street, West Ryde (Charity Creek Catchment) 43 7.7. Gerrish Street – Cambridge Street – Pittwater Road, Gladesville (Gladesville Catchment) 44 7.8. Morrison Road at Gregory Street, Putney (Gladesville Catchment) 46 SINCLAIR KNIGHT MERZ I:\ENVR\Projects\EN02970\Deliverables\Reports\Flood Study\EN02970 Flood Study report Rev C Final.docx PAGE iii Parramatta River - Ryde Sub-Catchments Flood Study 7.9. Victoria Road near Gardeners Lane to Deakin Street, West Ryde (Archer Creek Catchment) 47 7.10. Belmore Street to Shepherd Street, Ryde (Charity Creek Catchment) 48 7.11. Princes Street, Putney, from Morrison Road to Waterview Street (River Catchment) 49 8. Conclusions 51 9. References 52 Appendix A Flood Depth Mapping 53 Appendix B Flood Level Mapping 54 Appendix C Flood Planning Area Mapping 55 Appendix D Peak Overland Flows 56 Appendix E Provisional Flood Risk Precinct Mapping 64 Appendix F Climate Change Impact Flood Mapping 65 SINCLAIR KNIGHT MERZ I:\ENVR\Projects\EN02970\Deliverables\Reports\Flood Study\EN02970 Flood Study report Rev C Final.docx PAGE iv Parramatta River - Ryde Sub-Catchments Flood Study Document history and status Revision Date issued Reviewed by Approved by Date approved Revision type A 20/2/2013 J Wall A Bentley 21/2/2013 PD Review B 8 April 2013 J Wall A Bentley 8 April 2013 PD Review C 22 August 2013 J Wall A Bentley 29/8/13 PD Review Distribution of copies Revision Copy no Quantity Issued to A PDF 1 Client Issue B PDF 1 Client Issue C PDF 1 Client Issue Printed: 29 August 2013 Last saved: 29 August 2013 08:01 AM I:\ENVR\Projects\EN02970\Deliverables\Reports\Flood Study\EN02970 Flood Study File name: report Rev C.docx Author: Lih Chong Project manager: Amy Bentley Name of organisation: City of Ryde Name of project: Parramatta River - Ryde Sub-Catchments Flood Study and Floodplain Risk Management Plan Name of document: Flood Study Document version: Revision C Project number: EN02970 SINCLAIR KNIGHT MERZ I:\ENVR\Projects\EN02970\Deliverables\Reports\Flood Study\EN02970 Flood Study report Rev C Final.docx PAGE v Parramatta River - Ryde Sub-Catchments Flood Study Executive Summary A flood study has been undertaken for the five drainage catchments in Ryde Local Government Area (LGA) which drain to the Parramatta River. Development in the study area is at risk to flooding during heavy rainfall events due to the nature of the urban environment and the limited capacities of the natural and built drainage network. Such events have occurred in 1984, 1986, 1988 (twice), 1989 (twice) and 1990, leading to widespread flooding and damage to properties. A number of major drainage improvement projects have been completed in the study area to alleviate the flooding problems. The storm events in May 1998 and April 2003 caused significant problems but not to the extent as those in the late 1980’s due to the drainage upgrades. However, there are numerous locations where existing development is at risk from flooding. This flood study has been commissioned by the City of Ryde (Council), with the assistance of NSW Office of Environment and Heritage, and defines the existing flood behaviour in the five catchments, being: Archer Creek; Denistone; Charity Creek; River and Gladesville. Flooding occurs primarily as overland flows in the majority of the study area, while mainstream flooding is experienced adjacent to the watercourses.