Appendix J. Hydraulics Impact Assessment
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Received 21.08.2020 East Derwent Highway Upgrade Development Application Change the document title using the properties option on the Jacobs RibbonProject NameClient Name Appendix J. Hydraulics Impact Assessment Received 21.08.2020 East Derwent Highway Upgrade Hydraulic Impact Assessment IS262318 | A 14 August 2020 Department of State Growth Hydraulic Impact Assessment Department of State Growth Received 21.08.2020 Hydraulic Impact Assessment East Derwent Highway Upgrade Project No: IS262318 Document Title: Hydraulic Impact Assessment Revision: A Date: 28 April 2020 Client Name: Department of State Growth Project Manager: Clayton Johnston Author: Clayton Johnston File Name: IS262318-0000-CH-RPT-0001 Jacobs Australia Pty Limited 100 Melville St, Hobart 7000 GPO Box 1725 Hobart TAS 7001 Australia T +61 3 6221 3711 F +61 3 6221 3766 www.jacobs.com © Copyright 2019 Jacobs Australia Pty Limited. The concepts and information contained in this document are the property of Jacobs. Use or copying of this document in whole or in part without the written permission of Jacobs constitutes an infringement of copyright. Limitation: This document has been prepared on behalf of, and for the exclusive use of Jacobs’ client, and is subject to, and issued in accordance with, the provisions of the contract between Jacobs and the client. Jacobs accepts no liability or responsibility whatsoever for, or in respect of, any use of, or reliance upon, this document by any third party. Document history and status Revision Date Description Author Reviewed Approved A 28/04/2020 Draft for internal review SF AK AK B 14/08/2020 Final Draft for DSG review CJ AK AK i Received 21.08.2020 Hydraulic Impact Assessment Contents 1. Introduction............................................................................................................................................................. 5 1.1 Project Background ................................................................................................................................................................ 5 1.2 Existing Conditions ................................................................................................................................................................. 6 1.2.1 Highway trunk drainage, Debomfords Lane ................................................................................................................. 7 1.2.2 Dumbarton Drive trunk drainage...................................................................................................................................... 7 1.2.3 Llenroc Street trunk drainage ............................................................................................................................................ 8 1.2.4 Overall Context ........................................................................................................................................................................ 8 1.3 Design Intent ............................................................................................................................................................................ 9 1.4 Previous Flood Records ..................................................................................................................................................... 10 2. Assessment Criteria ............................................................................................................................................ 11 2.1 Overview .................................................................................................................................................................................. 11 2.2 Local Authority Planning Codes ..................................................................................................................................... 11 2.2.1 Context Setting ..................................................................................................................................................................... 11 2.2.2 Interpretation ........................................................................................................................................................................ 11 2.3 Flood Immunity Standards............................................................................................................................................... 12 2.3.1 Terminology ........................................................................................................................................................................... 12 2.3.2 Road Authority Standards ................................................................................................................................................ 13 2.3.3 Austroads Guidelines .......................................................................................................................................................... 13 2.3.4 Overview of Standards ....................................................................................................................................................... 14 3. Assessment Methodology ................................................................................................................................ 15 3.1 Overview .................................................................................................................................................................................. 15 3.2 Existing Conditions .............................................................................................................................................................. 15 3.2.1 Inputs and Assumptions .................................................................................................................................................... 15 3.2.2 Design Flood Events ........................................................................................................................................................... 15 3.2.3 Hydrologic Modelling Approach .................................................................................................................................... 15 3.2.3.1 Catchment and Model Development ........................................................................................................................... 15 3.2.3.2 Model Validation .................................................................................................................................................................. 17 3.2.4 Hydraulic Modelling Approach....................................................................................................................................... 17 3.2.4.1 Model and Terrain Development ................................................................................................................................... 17 3.2.4.2 Boundary Conditions .......................................................................................................................................................... 17 3.2.4.3 Roughness and Losses ....................................................................................................................................................... 18 3.2.4.4 Model Validation .................................................................................................................................................................. 18 3.2.4.5 Critical Storms ....................................................................................................................................................................... 18 3.2.4.6 Existing Case Flood Modelling Results ........................................................................................................................ 18 3.3 Proposed Drainage Design............................................................................................................................................... 19 3.3.1 Inputs and Assumptions .................................................................................................................................................... 19 3.3.2 Modelling Approach ........................................................................................................................................................... 19 3.3.3 Hydrologic Modelling Approach .................................................................................................................................... 19 ii Received 21.08.2020 Hydraulic Impact Assessment 3.3.4 Hydraulic Modelling Approach....................................................................................................................................... 20 3.3.4.1 Modelled Components ...................................................................................................................................................... 20 3.3.4.2 Model Development ........................................................................................................................................................... 21 3.3.5 Results ...................................................................................................................................................................................... 22 3.4 Water Sensitive Urban Design ......................................................................................................................................... 22 3.4.1 Water quality target reductions