Tallebudgera Creek Catchment Hydrological Study
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Tallebudgera Creek Catchment Hydrological Study July 2014 1 Title: Tallebudgera Creek Catchment Hydrological Study Author: Study for: City Planning Branch Planning and Environment Directorate The City of Gold Coast File Reference: WF46/44/(P1) TRACKS-#45381530-v1 Version history Changed by Reviewed by & Version Comments/Change & date date 1.0 Draft Review Review Review Review Distribution list Name Title Directorate Branch Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 2 of 76 Executive Summary The Natural Hazards (NH) team of the City Planning Branch has undertaken a comprehensive hydrological study of the Tallebudgera Creek catchment. The Council of the City of Gold Coast (Council) commissioned WRM Water and Environment Pty Ltd (WRM) to undertake a study to review and update its hydrological models to a consistent standard in December 2007. WRM assessed all aspects of model development, calibration, estimation of design discharges and provided a set of recommendations (12.10 ), including a recommendation to update all the hydrological models across the city. Furthermore, - Monte Carlo methodologies have since become available and it was considered necessary to contrast these methods with the standard Design Event Approach (DEA). This study addresses the WRM recommendation and includes Monte Carlo methodologies for comparative analysis. The main objective of this study is to develop a hydrological model for the Tallebudgera Creek catchment using the URBS modelling software, calibrate and verify the model against historical flood data, verify the modelling results against Flood Frequency Analysis (FFA) and Joint Probability Analysis (JPA). Finally, the study aims to estimate the design flood discharges for events ranging from 2 year Average Recurrence Interval (ARI) to the Probable Maximum Precipitation Design Flood (PMPDF) and document all the works to a consistent standard. In this study, the URBS model for the Tallebudgera Creek catchment was developed using the current land uses, topographic data sets and best available industry standard modelling approaches. The hydrological study undertaken by Council’s NH team has been reviewed by WRM, Council’s Peer Review Group (PRG) and Don Carroll Project Management. Calibration and verification data for 28 historical flood events between 1954 and 2013 were sourced for this study from the Bureau of Meteorology (BoM). From the available data, four events (January 2013, January 2008, June 2005 and February 2004) were selected for calibration and another two events (April 1990 and February 1990) were selected for verification. The selection of calibration and verification events was based on the quality of recorded data sets. The calibration attempted to match the modelled and recorded flood peaks, volumes, shapes and timing of the hydrographs. A single set of model parameters was adopted for all calibration, verification and design events. Rainfall losses were adjusted to achieve the best possible hydrograph shapes and flood volumes. A uniform initial loss and a continuing loss rate were adopted for each event. The table below shows the set of model parameters adopted for all calibration, verification and design event simulations: Parameter Adopted Value α (Channel lag) 0.11 (Catchment lag) 1.6 m (Catchment non-linearity) 0.65 N (Muskingum non-linearity) 1 F (Fraction of sub-catchment forested) F*0.5 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 3 of 76 Good agreement was achieved between modelled and rated discharges from recorded levels at Tallebudgera Creek Road Gauging Station (GS) for all calibration events. For the purpose of this report, rated discharges from recorded levels are labelled as recorded discharges. The table below shows the modelled and recorded peak discharges at Tallebudgera Creek Road GS for all calibration events. Peak Discharge @ Tallebudgera Ck Rd GS (m3/s) Flood Event Modelled Recorded January 2013 378 384 January 2008 668 741 June 2005 585 553 February 2004 229 230 The calibrated URBS model was then used to estimate the design flood discharges throughout the Tallebudgera Creek catchment using DEA. The design rainfall data including Intensity Frequency Duration (IFD) tables, temporal patterns (TP), Areal Reduction Factor (ARF), rainfall spatial distribution and design rainfall losses, adopted in this study were recommended by WRM and Council’s Peer Review Group (Table 17 - Summary of Recommended Methodology for Design Event Analysis) and Don Carroll Project Management. A Flood Frequency Analysis (FFA) was undertaken using annual peak discharges for Tallebudgera Creek Road GS. Forty three (43) years (1970 – 2013) of recorded data were available at the time of this study. The methodology recommended in Book 4, Section 2 of Australian Rainfall and Runoff (1987) viz. fit a Log-Pearson Type III distribution, was used for this study. Joint Probability Analyses (JPA) were undertaken using both the Total Probability Theorem Monte Carlo (TPT MC) methodology and Cooperative Research Centre – Catchment Hydrology Monte Carlo (CRC-CH MC) methodology. The design peak flood discharges throughout the Tallebudgera Creek catchment have been estimated using the DEA, FFA, TPT MC and CRC–CH MC methodologies. The peak design discharges for different ARIs at Tallebudgera Creek Road GS estimated by these methods are shown in the table below: ARI Design Peak Discharge @ Tallebudgera Creek Road GS (m3/s) (Year) DEA FFA TPT MC CRC-CH MC 2 182 184 237 202 5 327 303 340 293 10 415 393 436 371 20 512 490 531 463 50 633 634 660 596 100 741 758 769 799 200 868 897 893 903 The comparison table shows good agreement between the DEA, FFA, TPT MC and CRC-CH MC estimates. Consequently, the design hydrographs estimated in this study using the Design Event Approach are considered robust and will provide the most appropriate input to the Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 4 of 76 hydraulic models to be used for flood planning and flood management studies in the Tallebudgera Creek catchment. The table below shows the final peak design discharges at different locations within Tallebudgera Creek catchment for the 2 year ARI to PMP design flood events. It is of note that the design peak discharges estimated in the above comparison table are based on adopted ARF for the catchment area, only upstream of Tallebudgera Creek Road GS. However the design discharges estimated in the table below are based on adopted ARF for the total catchment area1. ARI Design Peak Discharge (m3/s) Talle Ck Dam Talle Ck Rd Coplicks Br Oyster Ck Catchment (Year) AL AL AL AL Outlet 2 120 178 187 12 194 5 215 323 348 20 346 10 273 410 440 24 440 20 339 507 547 29 547 50 421 629 686 36 690 100 492 737 805 41 816 200 555 860 930 50 960 500 653 1010 1092 58 1139 1000 843 1274 1332 76 1284 2000 937 1407 1462 83 1421 PMPDF 1830 2979 2930 146 3146 1 Adoption of an ARF for the total catchment is appropriate for deriving inflows for a hydraulic model of the lower Tallebudgera catchment. Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 5 of 76 Table of Contents Executive Summary ............................................................................................................................. 3 1. Introduction ................................................................................................................................... 9 1.1 Background .......................................................................................................................... 9 1.2 Study Objective and Scope ............................................................................................... 10 1.3 Previous Studies ................................................................................................................ 10 1.3.1 WBM (1995) ............................................................................................................. 10 1.3.2 GCCC (2001)............................................................................................................ 10 1.3.3 GHD (2003) .............................................................................................................. 10 1.3.4 GHD (2003) .............................................................................................................. 11 1.3.5 GHD (2004) .............................................................................................................. 11 1.3.6 GHD (2007) .............................................................................................................. 11 1.4 Limitation Statement .......................................................................................................... 11 1.5 Acknowledgement ............................................................................................................. 11 2. Catchment Description ............................................................................................................... 12 2.1 General .............................................................................................................................. 12 2.2 Land Use ........................................................................................................................... 13 3. Methodology ................................................................................................................................ 14 4. Available Data .............................................................................................................................