Lower Wimmera Flood Investigation

Lower Wimmera – Site Visit and Data Collation Report January 2017 Wimmera CMA Lower Wimmera Flood Investigation DOCUMENT STATUS Version Doc type Reviewed by Approved by Distributed to Date issued Final Report Ben Tate Ben Tate Abdul Aziz 05/05/2015 Final Report Ben Tate Ben Tate Abdul Aziz 31/01/2017 PROJECT DETAILS Project Name Lower Wimmera Flood Investigation Client Wimmera CMA Client Project Manager Abdul Aziz Water Technology Project Manager Ben Tate Report Authors Ben Hughes Job Number 3795-01 Report Number R01 Document Name Site Visit, Inception and Data Collation Report Cover Photo: Dimboola Weir – The weir structure was replaced after damage caused during the January 2011 flood event (Photo captured during the site visit) Copyright Except where otherwise noted, this document is licensed under the Creative Commons Attribution 4.0 License. You are free to re-use the information contained within this report on the condition that you credit Water Technology as the author. All logos and branding are excluded from this license. © Water Technology Pty Ltd 15 Business Park Drive Notting Hill VIC 3168 Telephone (03) 8526 0800 Fax (03) 9558 9365 ACN No. 093 377 283 ABN No. 60 093 377 283 3795-01 / R01 Final - 31/01/2017 ii Wimmera CMA Lower Wimmera Flood Investigation TABLE OF CONTENTS 1. Background ................................................................................................................... 1 2. Project Purpose ............................................................................................................. 1 2.1 Overview .................................................................................................................................. 1 2.2 Project Scope ........................................................................................................................... 1 3. Site Visit ........................................................................................................................ 3 4. Available information .................................................................................................... 4 4.1 Overview .................................................................................................................................. 4 4.2 Streamflow gauges .................................................................................................................. 4 4.2.1 Overview .................................................................................................................................. 4 4.2.2 Wimmera River at Horsham (Walmer) .................................................................................... 6 4.2.3 Norton Creek at Lower Norton .............................................................................................. 10 4.2.4 Wimmera River at Quantong................................................................................................. 11 4.2.5 Wimmera River US Dimboola ................................................................................................ 12 4.2.6 Wimmera River at Lochiel Railway Bridge ............................................................................. 14 4.2.7 Wimmera River at Tarranyurk ............................................................................................... 15 4.2.8 Wimmera River at Jeparit ...................................................................................................... 16 4.2.9 Gauge Summary .................................................................................................................... 16 4.3 Previous Studies .................................................................................................................... 17 4.3.1 Wimmera River and Yarriambiack Creek Flow Modelling Study4 ......................................... 17 4.3.2 Horsham Bypass Hydrology and Hydraulic Investigation ...................................................... 19 4.3.3 East Horsham Flood Plan ....................................................................................................... 23 4.3.4 Horsham Flood Study ............................................................................................................ 24 4.3.5 Dimboola Flood Study ........................................................................................................... 25 4.3.6 Jeparit Flood Study ................................................................................................................ 26 4.4 January 2011 .......................................................................................................................... 30 4.4.1 Rainfall ................................................................................................................................... 30 4.4.2 Stream Flows ......................................................................................................................... 32 4.4.3 Inundation ............................................................................................................................. 33 4.5 Observed peak flood heights and extents ............................................................................. 34 4.6 Topographic data and feature survey ................................................................................... 36 4.6.1 LiDAR Comparison ................................................................................................................. 38 4.6.2 LiDAR Verification .................................................................................................................. 47 4.6.3 Discussion .............................................................................................................................. 49 4.7 Structure Details .................................................................................................................... 50 4.7.1 VicRoads ................................................................................................................................ 50 4.7.2 VicTrack ................................................................................................................................. 52 4.7.3 Weir Structures ...................................................................................................................... 54 5. Modelling Approach .................................................................................................... 56 5.1 Hydrology .............................................................................................................................. 56 5.1.1 Calibration ............................................................................................................................. 57 5.1.2 Design .................................................................................................................................... 57 5.2 Hydraulics .............................................................................................................................. 57 3795-01 / R01 Final - 31/01/2017 iii Wimmera CMA Lower Wimmera Flood Investigation 6. Recommendations ....................................................................................................... 58 6.1 Event Selection ...................................................................................................................... 58 6.2 Survey Data ............................................................................................................................ 58 Appendix A Data Register ..................................................................................................... 59 Appendix B Site visit photos .................................................................................................. 60 LIST OF FIGURES Figure 2-1 Original and extended study area ................................................................................. 2 Figure 4-1 Streamflow gauges relevant to the study area ............................................................. 5 Figure 4-2 Gauge record at Wimmera River at Horsham (Walmer) showing flow and the Thiess Quality Code .................................................................................................................. 7 Figure 4-3 January 2011 hydrograph recorded at the Wimmera River at Horsham (Walmer) streamflow gauge .......................................................................................................... 8 Figure 4-4 Wimmera River at Horsham (Walmer) gauge and Western Highway January 2011 measurement locations................................................................................................. 9 Figure 4-5 Wimmera River at Horsham streamflow gauge rating curve and measurements ..... 10 Figure 4-6 Wimmera River at Horsham current and previous rating curves ............................... 10 Figure 4-7 Gauge record at Norton Creek at Lower Norton showing water level and limit of extrapolated section of the rating curve ..................................................................... 11 Figure 4-8 Gauge record at Wimmera River at Quantong showing gauge level and Thiess Quality Codes ........................................................................................................................... 12 Figure 4-9 Wimmera River at US Dimboola rating curve and gaugings ....................................... 13 Figure 4-10 Wimmera River at US Dimboola flows and Thiess Quality Codes ............................... 13 Figure

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