Background Document to the Floodplain Management Plan for the Border Rivers Valley Floodplain 2020
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RURAL FLOODPLAIN MANAGEMENT PLANS Background document to the Floodplain Management Plan for the Border Rivers Valley Floodplain 2020 Water Management Act 2000 August 2020 NSW Department of Planning, Industry and Environment | dpie.nsw.gov.au Published by NSW Department of Planning, Industry and Environment dpie.nsw.gov.au Title: Background document to the Floodplain Management Plan for the Border Rivers Valley Floodplain 2020 Subtitle: Water Management Act 2000 First published: August 2020 Department reference number: INT20/8160 More information www.industry.nsw.gov.au/water Acknowledgements Floodplain management plans are being prepared under the NSW Healthy Floodplains Project, which is funded by the Australian Government’s Sustainable Rural Water Use and Infrastructure Program as part of the implementation of the Murray–Darling Basin Plan in NSW © State of New South Wales through Department of Planning, Industry and Environment 2020. You may copy, distribute, display, download and otherwise freely deal with this publication for any purpose, provided that you attribute the Department of Planning, Industry and Environment as the owner. However, you must obtain permission if you wish to charge others for access to the publication (other than at cost); include the publication in advertising or a product for sale; modify the publication; or republish the publication on a website. You may freely link to the publication on a departmental website. Disclaimer: The information contained in this publication is based on knowledge and understanding at the time of writing (August 2020) and may not be accurate, current or complete. The State of New South Wales (including the NSW Department of Planning, Industry and Environment), the author and the publisher take no responsibility, and will accept no liability, for the accuracy, currency, reliability or correctness of any information included in the document (including material provided by third parties). Readers should make their own inquiries and rely on their own advice when making decisions related to material contained in this publication. Background document to the Floodplain Management Plan for the Border Rivers Valley Floodplain 2020 Contents List of figures ................................................................................................................................. i List of tables .................................................................................................................................. ii Abbreviations ................................................................................................................................ 1 Purpose ......................................................................................................................................... 4 The Border Rivers Valley Floodplain ........................................................................................... 4 Flooding behaviour ...................................................................................................................... 9 Downstream of Yetman to Goondiwindi ................................................................................. 10 Goondiwindi to Boomi ............................................................................................................ 10 Boomi to Mungindi ................................................................................................................. 11 Key changes to the natural flooding regime ........................................................................... 11 Developing the plan .................................................................................................................... 12 Step 1: Define the floodplain boundary ..................................................................................... 14 Step 2: Identify existing flood works ......................................................................................... 19 Step 3: Review existing rural floodplain management arrangements .................................... 20 NSW Border Rivers Valley Floodplain ....................................................................................... 20 Qld Border Rivers Floodplain ..................................................................................................... 20 Border Rivers Region ................................................................................................................ 20 Step 4: Determine the floodway network .................................................................................. 22 Design floods ............................................................................................................................ 23 Modelling ................................................................................................................................... 26 Hydrologic models ................................................................................................................. 26 Hydraulic models ................................................................................................................... 27 Model calibration .................................................................................................................... 28 Hydraulic criteria for the floodway network ................................................................................ 28 Floodways ............................................................................................................................. 29 Inundation extent ................................................................................................................... 31 Step 5: Identify and prioritise floodplain assets ....................................................................... 32 Ecological assets ....................................................................................................................... 32 Identifying ecological assets .................................................................................................. 32 Flood dependency of wetlands and other floodplain ecosystems ........................................... 38 Prioritisation of ecological assets ........................................................................................... 40 Priority ecological assets........................................................................................................ 41 Cultural assets........................................................................................................................... 42 Cultural asset type—Aboriginal cultural values ...................................................................... 42 Cultural asset type – heritage sites ........................................................................................ 44 Flood dependency of Aboriginal cultural values and heritage sites ........................................ 44 NSW Department of Planning, Industry and Environment | INT20/8160 | i Background document to the Floodplain Management Plan for the Border Rivers Valley Floodplain 2020 Prioritisation of Aboriginal heritage sites ................................................................................ 45 Prioritisation of Aboriginal values ........................................................................................... 46 Step 6: Prepare a socio-economic profile ................................................................................. 47 Study area geography ............................................................................................................... 47 Data sources .......................................................................................................................... 49 Demographic profiles................................................................................................................. 49 Employment by industry ......................................................................................................... 50 Income ................................................................................................................................... 50 Economic wellbeing indicators ............................................................................................... 50 Production ............................................................................................................................. 50 Step 7: Delineate management zones ....................................................................................... 52 Description of management zones ............................................................................................ 54 Management Zone A – major discharge areas, defined floodways (MZ A) ............................. 54 Management Zone B – flood storage and discharge areas for design floods (MZ B) .............. 54 Management Zone C – flood fringe areas and existing developed areas (MZ C) ................... 55 Management Zone CU – Urban areas managed by Local Council (MZ CU) .......................... 55 Management Zone D – special environmental and cultural protection areas (MZ D) .............. 55 Hydraulic criteria ........................................................................................................................ 56 Ecological criteria ...................................................................................................................... 56 Management Zones A, B, and C ...........................................................................................