Tallebudgera Creek Catchment
Hydrological Study
July 2014
1
Title: Tallebudgera Creek Catchment Hydrological Study
Author:
Study for: City Planning Branch
Planning and Environment Directorate
File Reference: WF46/44/(P1)
TRACKS-#45381530-v1
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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
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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
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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.
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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 ...... 16 4.1 Topographic Data ...... 16 4.2 Land Use Data ...... 16 4.3 Rainfall Data ...... 16 4.4 Gauge Height Data ...... 19 4.5 Rating Tables ...... 19 4.5.1 Tallebudgera Creek Dam ...... 19 4.5.2 Tallebudgera Creek Road ...... 20 4.5.3 Coplicks Bridge...... 22 4.6 Storage Data ...... 22 5. Model Development ...... 26 5.1 Model Description ...... 26 5.2 Model Configuration ...... 27 5.2.1 Land Use ...... 27 6. Model Calibration and Verification ...... 31 6.1 Selection of Calibration and Verification Events ...... 31 6.2 Calibration Methodology ...... 33 6.3 Assignment of Rainfalls and Temporal Patterns ...... 34 6.4 Adopted Model Parameters ...... 34 6.5 Initial and Continuing Losses ...... 34
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6.6 Calibration Results ...... 35 6.6.1 General Comments ...... 35 6.6.2 January 2013 Event...... 35 6.6.3 January 2008 Event...... 36 6.6.4 June 2005 Event...... 36 6.6.5 February 2004 Event ...... 36 6.7 Verification Results ...... 36 6.7.1 April 1990 Event ...... 37 6.7.2 February 1990 Event ...... 37 7. Flood Frequency Analysis ...... 38 7.1 Method of Analysis ...... 38 7.2 Available data ...... 38 7.3 Annual Peak Discharge Analysis ...... 38 8. Design Flood Estimation ...... 40 8.1 Methodology ...... 40 8.2 Frequent to Large Design Events (up to and including 100 Year ARI) ...... 43 8.2.1 Rainfall Depth Estimation ...... 43 8.2.2 Areal Reduction Factors ...... 43 8.2.3 Temporal Patterns ...... 44 8.2.4 Spatial Distribution ...... 47 8.2.5 Rainfall Losses ...... 47 8.2.6 Design Peak Discharge ...... 47 8.3 Rare Design Events (200 to 2000 Year ARI) ...... 49 8.3.1 Rainfall Depth Estimation ...... 49 8.3.2 Areal Reduction Factors ...... 49 8.3.3 Temporal Patterns ...... 49 8.3.4 Spatial Distribution ...... 52 8.3.5 Losses ...... 52 8.3.6 Design Discharges ...... 52 8.4 Extreme Design Events - Probable Maximum Precipitation Design Flood (PMPDF) ...... 54 8.4.1 Rainfall Depth Estimation ...... 54 8.4.2 Areal Reduction Factors ...... 54 8.4.3 Temporal Patterns ...... 54 8.4.4 Spatial Distribution ...... 54 8.4.5 Losses ...... 54 8.4.6 Design Discharges ...... 54 8.5 Joint Probability Approach ...... 55 8.5.1 TPT ...... 55 8.5.2 CRC-CH ...... 57 9. Comparison ...... 58
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10. Conclusion ...... 61 11. Recommendations ...... 62 12. Reference ...... 63 13. Appendix A: URBS Model Sub-catchment Areas and Land Uses ...... 65 14. Appendix B: URBS Catchment Definition File ...... 66 15. Appendix C: Calibration and Verification Plot ...... 70
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1. Introduction
1.1 Background
Over recent years, the Council of the City of Gold Coast developed numerous hydrological models of its catchments and waterways. These models were developed by Council’s staff and various consultants, using a range of different approaches and assumptions. The standard of these models, with respect to their configuration, calibration, use for design peak discharge estimation and documentation varies significantly.
In December, 2007 the Council commissioned WRM Water & Environment (WRM) to undertake a major study to review the City’s hydrological models and develop consistent peer reviewed methodology and documentation standards. This methodology and standards were then to be applied to ten major catchments throughout the city viz. Coomera, Nerang, Logan-Albert, Pimpama, Worongary, Mudgeeraba, Loder, Biggera, Tallebudgera and Currumbin.
A comprehensive review of data, previous hydrological models and associated reports for the above 10 catchments was undertaken prior to the commencement of model updates. This review assessed all aspects of model development, calibration and use for the estimation of design discharges. Based on the review, a set of recommendations were provided to update the 10 models in a consistent manner across the city area using the latest data and modelling approaches. Details of the model review and its findings are given in Section 12.10 of this report.
Based on WRM recommendations, Council upgraded the hydrological model for Tallebudgera Creek catchment using the URBS modelling software in August 2009. The model was calibrated against three historical events (January 2008, June 2005 and February 2004) and verified against two historical events (April 1990 and February 1990). A Flood Frequency Analysis (FFA) was undertaken for Tallebudgera Creek Road Gauging Station (GS) using 38 years (1970 – 2008) of recorded data. The calibrated model was then used to estimate the design discharges from the 2 year ARI to PMPDF.
This model was reviewed by WRM and Council’s Peer Review Group (PRG) in 2009/10. The PRG included Erwin Weinmann from Monash University and Dr Bill Weeks from the Department of Transport and Main Roads.
The upgraded model was again reviewed by Don Carroll Project Management in 2013. At the time of review the following modelling tasks were undertaken, as per Don Carroll’s recommendations:
The January 2013 event should be included in the calibration dataset. Review the fraction of sub-catchment forested factor F. Redo the FFA for 43 years (1970 - 2013) of recorded data at Tallebudgera Creek Road GS. Extend the modelling to include Monte Carlo methodologies to address the Queensland Floods Commission of Inquiry Recommendation.
This report describes the development of the URBS hydrological model, calibration, FFA, Monte Carlo simulation and design event simulation for the Tallebudgera Creek catchment.
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1.2 Study Objective and Scope
The main objective of this study is to develop a hydrological model for the Tallebudgera Creek catchment using the URBS model as the preferred citywide common modelling software platform. The model should be calibrated and verified against available data, and fully documented to a consistent standard. Once this objective is achieved, the calibrated model is to be used to estimate the design flood discharges using a consistent methodology. The scope of work for the Tallebudgera Creek catchment modelling study is as follows:
Review the existing models and data. Update the existing model to a consistent standard. Review and update model calibration and verification. Undertake an FFA at Tallebudgera Creek Road GS. Undertake Monte Carlo simulations. Estimate the design discharges and extreme event discharges at key locations throughout the catchment using current industry standard methodologies. Document the adopted methodology, tasks and results to a consistent manner.
1.3 Previous Studies
A number of hydrological modelling studies have been previously carried out for the Tallebudgera Creek catchment. Brief descriptions of the most relevant of these studies are presented below:
1.3.1 WBM (1995) WBM Oceanics Australia undertook a detailed flood study for Tallebudgera Creek catchment in 1995 for Gold Coast City Council. As part of the study, WBM developed a XP-RAFTS hydrological model for the catchment and calibrated the model for February 1972, January 1974, March 1987, April 1988, and February 1990 flood events. A FFA was carried out based on rated peak annual discharges at the Tallebudgera Creek Road (GS 146095A). The calibrated model was then used to estimate the design discharges at different locations within the catchment for 5, 10, 20, 50 and 100 year ARI events.
1.3.2 GCCC (2001) A hydrological study of Tallebudgera Creek catchment was undertaken by Gold Coast City Council (GCCC) in 2001. In this study, a URBS hydrological model was developed and calibrated for March 1999, December 1991, February 1990, April 1988, May 1987, April 1984, June 1983, February 1976, January 1974, April 1972 and February 1972 flood events. FFA was also carried out for thirty years of recorded data (1970 – 1999) at Tallebudgera Creek Road (GS 146095A). The calibrated model was then used to estimate the design discharges for 5, 10, 20, 50, 100, 200 and 500 year ARI at key locations within the catchment.
The Designated Flood Level (DFL) adopted in Current Planning Scheme 2003 version 1.2, amended in November 2011, is based on this study.
1.3.3 GHD (2003) Gutteridge Haskins & Davey (GHD) Pty Ltd was commissioned by GCCC to undertake a Risk Assessment study for Tallebudgera Creek Dam in May 2001. As part of the study GHD updated the RAFTS hydrological model previously developed by WBM Oceanics Australia (1995). The temporal patterns, the Intensity Frequency Distribution (IFD) data and the dam information contained in the model were checked and updated as necessary.
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1.3.4 GHD (2003) GHD prepared the Tallebudgera Creek Dam - Risk Assessment Addendum report for Gold Coast Water in July 2003. In this study, GHD developed a more comprehensive flood consequence model for different dam break scenarios however the hydrological analysis undertaken in GHD 2001 was kept unchanged.
1.3.5 GHD (2004) Another hydrological assessment of the Tallebudgera dam was undertaken by GHD in 2004. However, the report or the details of the study were not available for review during the current study.
1.3.6 GHD (2007) GHD undertook a detailed study for the Tallebudgera Creek Dam upgrade in July 2007. As part of this study, GHD reviewed the hydrology previously undertaken by GHD (2004). This review yielded no significant variation to the 2004 flood hydrology and the inflow hydrographs.
1.4 Limitation Statement
The following limitations apply to this report:
This report is prepared based on available data and information at the time of this study. The analysis and approach adopted in this study is specifically prepared for internal use only. Use of this report by any external entity is prohibited unless a written approval is obtained from the Council. The result of this study is accurate only for its intended purposes.
1.5 Acknowledgement
The assistance provided by the Bureau of Meteorology, and in particular, for this study is gratefully acknowledged. The Bureau provided the copies of their URBS hydrological models used for flood forecasting purposes and all the historical rainfall and stream flow data used in this study for model calibration and verification.
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2. Catchment Description
2.1 General
The Tallebudgera Creek catchment has a catchment area of 97.6 km2 and is one of the City’s major catchments. It has a main stream length of approximately 32 km running in a generally north-easterly direction. The headwaters of Tallebudgera Creek are located at the base of Springbrook, at approximately 958 mAHD. The creek has six major tributaries, including Mount Cougal Creek (7.51 km2), Petsch Creek (7.95 km2), Syndicate Creek (3.75 km2), Unnamed Creek (7.83 km2), Guineas Creek (12.31 km2) and Oyster Creek (3.57 km2).
The upper reaches of the catchment are steep and are covered by thick forest, the middle reaches are flatter and are covered by forest and rural developments and the lower reaches are flat and are fully urbanised.
Figure 1 shows the locality map of Tallebudgera Creek catchment. The only significant storage in the catchment is the Tallebudgera Creek Dam. The dam commands a catchment area of about 33 km2 and was built in 1949-1950.
Figure 1 - Locality Map, Tallebudgera Creek Catchment
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Table 1 shows the catchment area, the main creek length and the average channel slope at four key locations along the creek. The average creek slope upstream of the Tallebudgera dam is about 2.04%. Note that the average channel slope has been calculated using the equal area slope method (QUDM Figure 5.05.4).
Table 1 – Tallebudgera Creek Catchment Characteristics
Upstream Upstream Upstream Key Location Catchment Area Channel Length Average Channel 2 (km ) (km) Slope (%)
Tallebudgera Ck Dam 33.3 11.6 2.043
Tallebudgera Ck Road 56.4 17.9 0.870
Coplicks Bridge 72.2 22.6 0.299
Catchment Outlet 97.6 32.1 0.249
2.2 Land Use
Approximately 81% of the Tallebudgera Creek catchment is rural, mostly forested with some pastured areas and rural residential development. The remainder of the catchment is urban, comprising residential, high density residential, commercial and industrial areas. Land use data are discussed in sections 4.2 and 5.2 .
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3. Methodology
The hydrologic modelling of the Tallebudgera Creek catchment was undertaken using an approach and methodology consistent with the other catchments in the Gold Coast City area. The study adopted a systematic approach and consisted of the following steps:
Comprehensive review of the existing model and data - the specific tasks included: Review all previous studies. Review the existing URBS model. Review stage-storage and storage-discharge characteristics of the Tallebudgera Creek Dam. Review catchment and sub-catchments boundaries using the latest DTM and drainage network data. Review Tallebudgera Creek Dam and Coplicks Bridge rating curves and development of dependent rating curves for Tallebudgera Creek Road and Coplicks Bridge gauging stations. Review available rainfall and stream gauging data. Review existing land use data.
Model construction - the specific tasks included: Update the URBS model configuration. Update the Tallebudgera Creek Dam, Tallebudgera Creek Road and Coplicks Bridge rating curves. Generate a catchment (network) file and assign appropriate output locations and calibration points. Update model to reflect current land use in the catchment.
Model calibration and verification – the specific tasks included: Select calibration and verification events. Process rainfall and stream flow data for the selected calibration and verification events. Undertake rainfall analysis of all selected events to create sub-catchment specific rainfall sequences to generate rainfall definition files for the URBS model. Calibrate/verify the URBS model results against historical recorded data.
Flood Frequency Analysis – the specific tasks included: Analyse the available annual peak height data at Tallebudgera Creek Road GS. Convert recorded peak levels to discharge using the adopted rating table. Undertake the FFA to fit a Log-Pearson Type III distribution for an annual series of rated peak flood discharge at this location. Monte Carlo framework – the specific tasks included: Setup and run the model for Monte Carlo Total Probability Theorem (TPT). Setup and run the model for Monte Carlo Cooperative Research Centre for Catchment Hydrology (CRC-CH).
Design discharge estimation – the specific tasks included: Estimate the design rainfalls and loss rates for storm events ranging from 2 year ARI to PMPDF. Undertake the design event model runs for storm durations from 30 minutes to 72 hours for all ARIs and PMPDF. Undertake Flood Frequency Analyses (FFA) at Tallebudgera Creek Road GS.
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Reconcile design event results based on FFA. Estimate the design discharges at key locations throughout the catchment for flood events ranging from 2 year ARI to PMPDF. Verify the design discharges against Monte Carlo simulation results. Finalise the design discharges.
Prepare the study report – the specific tasks included: Document the adopted methodology, tasks and results.
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4. Available Data
4.1 Topographic Data
A 5m grid Digital Terrain Model (DTM November 2007) which covers most of the City area was available for this study. Unfortunately, these data do not cover the upper reaches of the catchment which is outside the City boundary. Topographic data for the upper reaches were available from 5m and 10m contour maps held by the Council. In addition, a digital drainage network layer was available from the Department of Natural Resources and Mines (DNRM) for better definition of the drainage paths within the catchment.
4.2 Land Use Data
The land use data used for the catchment were based on the latest GIS layers available from Council’s Infrastructure Planning Coordination Unit. The GIS layers contain Land Use, Domain and Local Area Plan data for the City of Gold Coast. Aerial photos and cadastre data were also used to supplement the above GIS data.
4.3 Rainfall Data
Rainfall data used in this study were provided by the Bureau of Meteorology (BoM). The BoM data was sourced from a variety of rainfall stations and data types including pluvio and daily stations. Table 2 shows the rainfall stations for which available data were supplied by BoM. The BoM flood warning map for rainfall and river height stations is shown in Figure 2.
The following is of note with regard to the rainfall stations:
The rainfall station coverage within the Tallebudgera Creek catchment is very good. There are six stations within the catchment. Stations indicated by the letters TM or ALERTs are automatic stations. TM stations are connected to the public telephone network and polled regularly by computer during periods of rain. ALERT stations communicate by radio and report every 1mm of rain to the local base station and the Flood Warning Centre in BoM. Daily stations are manual and report the rainfall amount received in 24 hours to 9:00am each day.
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Table 2 – Rainfall Data Availability for Tallebudgera Creek Catchment Station No Station Name Station Type Station Owner 540352 Bonogin Ck AL ALERT City of Gold Coast
040981 Burleigh Waters AL ALERT City of Gold Coast/BoM
040717 Coolangatta AWS AWS BoM
540320 Coplicks Bridge AL ALERT City of Gold Coast
040609 Elanora Water Treatment TM DNRM
540054 Little Nerang Dam AL ALERT City of Gold Coast
040417 Miami Daily BoM
540353 Mt Nimmel AL ALERT City of Gold Coast
540254 Mudgeeraba AL ALERT City of Gold Coast/BoM
540399 Mudgeeraba Ck TM TM DNRM
040558 Natural Bridge Daily BoM
040584 Hinze Dam Daily City of Gold Coast/BoM
040847 Hinze Dam AL ALERT City of Gold Coast/BoM
040882 Numinbah AL ALERT City of Gold Coast/BoM
540438 Numinbah Valley AL ALERT City of Gold Coast
540437 Numinbah Valley TM TM DNRM
54025200 Oyster Creek AL ALERT City of Gold Coast
040607 Springbrook AL ALERT BoM
540581 Springbrook TM TM DNRM
540400 Upper Springbrook AL ALERT City of Gold Coast
040848 Lower Springbrook AL ALERT City of Gold Coast/BoM
540287 Tallai AL ALERT City of Gold Coast
540497 Upper Tallebudgera AL ALERT City of Gold Coast
540366 Tallebudgera Ck Dam AL ALERT City of Gold Coast
540356 Tallebudgera Ck Rd AL ALERT City of Gold Coast
540355 Tallebudgera Ck Rd TM TM DNRM
58067 Tomewin (Border Gate) TM BoM
540354 Tomewin AL ALERT City of Gold Coast
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Figure 2 – Location of Rainfall and River Height Stations in South Coast (Source BoM)
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4.4 Gauge Height Data
Currently, six stream gauging stations are in operation within the Tallebudgera Creek catchment. Table 3 shows the detail of these stations. Figure 2 shows the station’s location. The following is of note with regard to the stream gauging stations:
Only Tallebudgera Creek Road ALERT station has reliable historical record (1970 to date). Tallebudgera Creek Dam ALERT, Coplicks Bridge ALERT and Oyster Creek ALERT stations have recorded data for the last 10+ years. Only Tallebudgera Creek Road TM station has a rating curve based on gauged discharges.
Table 3 – Gauge Height Data Availability for Tallebudgera Creek Catchment
Max Catch Rating Gauged Station ment Period of Operation Table Height No. Station Name Area From To Source (m) (km2) Tallebudgera GHD 540366 33.3 20-01-05 Now - Ck Dam AL (2007) Tallebudgera DNRM 146095A 56.4 04-06-70 Now 4.0 Ck Rd TM Table 22 Tallebudgera DNRM 540356 56.4 13-05-03 Now 4.9 Ck Rd AL Table 22 540320 Coplicks Br AL 72.2 15-02-01 Now BoM - 540252 Oyster Ck AL 3.6 14-05-97 Now BoM - Tallebudgera 540577 97.6 11-09-14 Now - - Ck Mouth AL
4.5 Rating Tables
Rating tables for Tallebudgera Creek Dam AL, Tallebudgera Creek Road AL, Coplicks Bridge AL and Oyster Creek ALs are available from BoM. Only Tallebudgera Creek Road TM has a rating table from DNRM based on gauged discharges. Of these, the quality of Oyster Creek rating table is poor. Further, this station is located within a small tributary of Tallebudgera Creek and is affected by tide levels. For these reasons, the Oyster Creek station is not included in the model calibration. A rating table for Tallebudgera Creek Dam is also available from the GHD (2007) study. The available rating tables for the Tallebudgera Creek stations are discussed below.
4.5.1 Tallebudgera Creek Dam Tallebudgera Creek Dam ALERT has recorded heights for the June 2005 and January 2008 flood events. BoM has adopted two different rating tables for this station for those two events. BoM’s 2005 and 2008 rating tables provided ratings up to a gauge height of 2m and 4m respectively. The GHD (2007) rating table provides ratings up to a gauge height of 7.75m.
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There are no gauging data for this station. The GHD (2007) rating table is based on a hydraulic analysis of the outflow from the dam. The BoM rating tables appear to be based on a correlation between their URBS model results and recorded gauge heights during 2005 and 2008 flood events. The GHD (2007) table has been adopted in this study. Figure 3 shows the available and adopted rating tables for Tallebudgera Creek Dam.
Adopted and Available Rating Tables @ Tallebudgera Ck Dam 9 GHD 2007 ‐ Adopted BoM June 2005 BoM Jan 2008 8 7 6 (m)
5 4 Height 3 2 1 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Discharge (m3/s)
Figure 3 - Available and Adopted Rating Tables at Tallebudgera Ck Dam
4.5.2 Tallebudgera Creek Road The Tallebudgera Creek Road gauging station has recorded level data since June 1970. Rating tables for this station were available from the BoM and the DNRM. DNRM Table 20 and Table 22 were analysed during this study and two separate rating tables were also available from BoM – one used for the 2005 flood event and another based on a modified version of DNRM Table 20. The DNRM rated this station up to a gauge height of 4m (195.5m3/s) during the March 1987 event. A hydraulic analysis of the Tallebudgera Creek Road rating table was undertaken using Council’s existing Mike 11 model. The rating table generated from the MIKE 11 analysis was then compared with the DNRM Table 20, DNRM Table 22 and DNRM Table 20 as modified by BoM. A very good match was observed between the MIKE 11 generated table, the DNRM Table 22 and the DNRM Table 20. The DNRM gauged data up to May 2013 were also compared against Table 22. Figure 5 shows the comparison plot between the DNRM gauged data and rating Table 22. Consequently the DNRM Table 22 was adopted for this study.
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Adopted and Available Rating Tables @ Tallebudgera Ck Rd 12.0
10.0
8.0 (m)
6.0 Height 4.0
2.0 Table 22 ‐ Adopted Table 20 Modified by BoM Table 20 MIKE 11 0.0 0 500 1000 1500 2000 2500 3000 Discharge (m3/s)
Figure 4 - Available and Adopted Rating Tables @ Tallebudgera Creek Road GS (146003B)
Figure 5 – Comparison Plot between Gauging and Rating Table 22 (Source, DNRM)
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4.5.3 Coplicks Bridge Two rating tables used by BoM for the June 2005 and January 2008 flood events are available for the Coplicks Bridge gauging station. Water levels at this station are influenced by the tidal variations. BoM rating tables do not take into account the effect of tidal levels. Accordingly, a hydraulic analysis using Council’s existing Mike 11 model was undertaken to develop a set of dependent rating tables for this station for the full range of expected tidal and surge fluctuations (-0.5 to 2.3 mAHD). Modelling results indicate that Tallebudgera Creek at Coplicks Bridge overflow the creek banks at a water level of approximately 3.5 m AHD (at a discharge of about 250-300 m3/s). This overflow bypasses the gauging station and is not accounted for in the rating tables. Based on the hydraulic modelling results, a set of dependent rating tables were developed. These dependent rating tables were adopted for water levels up to 3.5 mAHD and the BoM January 2008 table was adopted for the higher water levels. It is of note that the adopted rating table does not accurately pick up the bypass flows during large flood events and therefore the accuracy of the adopted table for high flow is suspect. Figure 6 shows the available and adopted rating tables at Coplicks Bridge.
Figure 6 – Adopted and Available Rating Table at Coplicks Bridge
4.6 Storage Data
Table 4 shows the details of the Tallebudgera Creek Dam. The low level outlets of the dam are sealed, and therefore, all outflows from the dam occur via the spillway. Table 5 shows the storage-surface, area-elevation and spillway characteristics of the dam sourced from GHD (2007). Figure 7 shows the storage-surface area-elevation relationships for the Tallebudgera Creek Dam sourced from GHD (2001). Figure 8 and Figure 9 show the spillway on the right bank looking from the upstream and downstream sides respectively.
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Table 4 – Tallebudgera Creek Dam Details Parameter Value / Description Type of dam Homogenous earth fill with concrete core wall Uncontrolled ogee type (Concrete gravity spillway with Type of Spillway post tensioned anchors) Height of dam 11.8 m Length of the embankment 100 m Dam crest level 48.52 m AHD Spillway levels 42.24 m AHD and 45.59 m AHD Full supply level 42.24 m AHD Full supply storage capacity 360 ML (at 42.24 mAHD) Storage at dam crest level 2081 ML (at 48.52 mAHD) Catchment area 33.3 m2
Table 5 – Tallebudgera Creek Dam Storage Characteristics Water Depth Reservoir Total Elevation Storage Above Above Storage Capacity Discharge (m AHD) Spillway (1000 x m3) Spillway (m) (1000 x m3) (m3/s) 36.6 0 0 0 0 38.1 0 20 0 0 39.6 0 80 0 0 41.1 0 190 0 0 42.24 0 318 0 0 42.5 0.26 348 29 8 43 0.76 421 103 43 43.5 1.26 506 188 95 44 1.76 591 273 162 44.5 2.26 704 386 243 45 2.76 836 517 337 45.5 3.26 967 649 441 45.59 3.35 991 673 463 46 3.76 1116 798 562 46.5 4.26 1276 958 704 47 4.76 1436 1118 861 47.5 5.26 1575 1257 1031 48 5.76 1700 1382 1206 48.5 6.26 1825 1507 1384 49 6.76 1950 1632 1570 49.5 7.26 2075 1757 1765 50 7.76 2200 1882 1967
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Figure 7 – Tallebudgera Creek Dam Stage Surface Area - Stored Volume Relationship
Figure 8 – Tallebudgera Creek Dam Spillway – View from the Upstream
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Figure 9 – Tallebudgera Creek Dam – View from the Downstream
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5. Model Development
5.1 Model Description
URBS is a networked (i.e. sub-catchment based) runoff-routing model that estimates flood hydrographs by routing rainfall excess through a module representing the catchment storage followed by channel routing to the sub-catchment outlet. In URBS, the storages are arranged to represent the drainage network of the catchment. The distributed nature of storage within the catchment is represented by a separate series of concentrated storages for the main stream and for major tributaries to provide a degree of physical realism. The storages in the model are generally non-linear, but linear storages can be used.
The model provides a number of options for conceptualising the rainfall-runoff process. Rainfall excess is first estimated from rainfall data using one of several available techniques (i.e. loss models) before being applied to the runoff-routing component of the model to compute the surface runoff hydrograph. Base flow, if significant, is estimated separately and added to the surface runoff hydrograph to provide the total catchment hydrograph. The model can easily incorporate the effects of land use change, construction of reservoirs, changes to channel characteristics and other changes in the catchment.
The model provides different options for runoff routing. The user is given the option of lumping the catchment runoff and channel flow components into a single routing component or modelling them as separate routing components. The latter option (i.e. the ‘split’ model) was adopted for this study.
In the split model the rainfall excess for each sub-catchment is first determined by subtracting losses from the rainfall hyetograph. The rainfall excess is then routed through conceptual catchment storage to determine the local runoff hydrograph for the sub-catchment. The storage - discharge relationship for catchment routing is:
2 A (1 F) m Scatch Q (1 U ) 2
Where 3 Scatch is the catchment storage (m h/s); is the catchment lag parameter; A is the area of sub-catchment (km2); U is the fraction urbanisation of sub-catchment; F is the fraction of sub-catchment forested; and m is the catchment non-linearity parameter.
In the above equation, β is determined during model calibration and is a global parameter. The local runoff hydrograph is then combined with runoff from the upstream sub-catchment and routed through channel storage to obtain the outflow hydrograph for the sub-catchment. Channel routing is based on the non-linear Muskingum model. The channel routing storage- discharge relationship is given by:
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n * L n Schnl f ( x Qu ( 1 x ) Qd ) S c Where 3 Schnl is the channel storage (m h/s); α is channel lag parameter f is reach length factor; L is reach length (km);
Sc is channel slope (m/m); 3 QU is inflow at upstream end of reach includes catchment inflow (m /s); 3 Qd is outflow at downstream end of the channel reach (m /s); x is Muskingum translation parameter; n is Muskingum non-linearity parameter (exponent); and n is Manning's 'n' or channel roughness.
In the above equation α and f are the principal calibration parameters. Note also that α is a global parameter, whereas f can be varied for each channel reach. URBS allows the user to select one of several standard loss models. The two primary loss models are the initial and continuing loss model and the proportional loss model. The initial and continuing loss model was adopted for Tallebudgera Creek Catchment Hydrological Study. This model assumes that there is an initial loss of ‘il’ mm before any rainfall becomes runoff. After this, a continuing loss rate of ‘cl’ mm/hr is applied to the rainfall, subject to the limit of the soil infiltration capacity (IFmax). The loss rates can be specified ‘globally’ to the entire catchment or ‘individually’ to each sub-catchment.
Full details of the URBS model and its features are given in the URBS User Manual (Carroll, 2012).
5.2 Model Configuration
5.2.1 Land Use Table 6 shows the major land use categories of the Tallebudgera Creek catchment corresponding to different land classifications, as adopted by the City of Gold Coast.
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Table 6 - Tallebudgera Creek Land Use Categories
URBS Model Land Use Classification Gold Coast City Council Classifications
Forest UF (Forested) o o Forest/Grassland o Grassland _ Urban/Suburban o Grazing o Open _ Ground o Recreation (Facilities & Sub/Urban UR (Rural Land) Parks) o Rural _ Residential o Tourism _ Recreation Park o Vacant _ Land o Waste _ Disposal o Access _ Restriction Strip o Commercial o Constructed Waterway _ Lake o Industrial o Marina a UH (High Density Urban) o Residential Choice o Tourism _ Accommodation o Transport (Rail, Road & Paved Areas) o Utilities _ Infrastructure o Water o Wetlands UM (Medium Density Urban) o Detached Dwelling Park Living UL (Low Density Urban) o o Tourism _ Caravan Park o Highly Disturbed _ Under UL/UM/UH b Development o Urban Residential a - Roads are included in this category b - Appropriate classification selected based on the aerial photos and site inspections
Out of five different land uses, four relate to the amount of urbanisation and forestation in the catchment, affecting both imperviousness (losses) and the routing characteristics.
Figure 10 shows the sub-catchment delineation of Tallebudgera Creek catchment for URBS. The model consists of 36 sub-catchments. Table 7 shows the sub-catchment areas and the land uses. Tallebudgera Creek Dam is located in sub-catchment 11.
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Figure 10 – Tallebudgera Creek URBS Model – Sub-catchment Delineation
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Table 7 - Tallebudgera Creek Sub-catchment Areas and Land Uses Sub- Sub- catchment catchment UL UM UH UR UF ID Area (km2) (km2) (km2) (km2) (km2) (km2) 1 2.1 0 0 0.013 0 2.087 2 2.27 0 0 0.043 0 2.227 3 4.38 0 0 0.197 0 4.184 4 4.14 0 0 0.168 1.602 2.371 5 3.24 0 0 0.072 0.818 2.350 6 2.62 0 0 0.183 0 2.437 7 2.84 0 0 0.133 0.802 1.905 8 2.05 0 0 0.021 1.820 0.210 9 3.57 0.030 0 0.169 1.107 2.263 10 2.21 0 0 0.021 0.521 1.668 11 3.87 0.557 0 0.175 0.623 2.516 12 4.53 0.037 0 0.185 0.205 4.103 13 4.31 0.681 0 0.059 2.997 0.573 14 3.64 0.001 0 0.118 1.399 2.122 15 3.6 0.006 0 0.344 1.547 1.703 16 3.75 0.004 0 0.259 1.139 2.348 17 3.32 0.055 0 0.219 1.495 1.550 18 1.25 0 0 0.167 1.058 0.025 19 4.27 0.000 0 0.128 0.621 3.520 20 3.56 0.006 0 0.190 1.342 2.022 21 3.58 0.031 0 0.248 1.968 1.333 22 3.13 0.087 0 0.444 2.544 0.055 23 1.16 0.001 0 0.069 0.272 0.818 24 0.88 0.002 0 0.015 0.085 0.779 25 1.37 0.006 0 0.061 1.275 0.027 26 1.55 0.018 0 0.070 1.298 0.164 27 0.38 0.020 0 0.081 0.279 0 28 1.65 0.005 0 0.252 1.374 0.020 29 1.4 0.160 0.002 0.590 0.620 0.028 30 1.08 0.011 0 0.097 0.283 0.688 31 1.7 0 0.536 0.202 0.878 0.084 32 0.58 0 0.142 0.431 0.007 0 33 4.18 0 1.018 1.879 1.283 0 34 1.37 0 0.052 1.212 0.036 0.070 35 2.21 0 0 1.116 0.895 0.199 36 5.82 0.127 0 4.943 0.477 0.274 Total 97.6 1.8 1.7 14.6 32.7 46.7
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6. Model Calibration and Verification
6.1 Selection of Calibration and Verification Events
Tallebudgera Creek catchment rainfall and stream height data for 28 historical flood events between 1954 and 2013 were available for this study from BoM. However, the quality, quantity and coverage of the available data for these events varied significantly. Data coverage for older events was poor and considered unsatisfactory for good calibration. Therefore, the model calibration and verification events were selected, as much as possible, from the most recent flood events. Table - 8 shows the selected calibration and verification events for the Tallebudgera Creek catchment. These events cover a wide range of flood discharges.
Table - 8 Selected Calibration and Verification Events Event Calibration Verification
January 2013
January 2008
June 2005
February 2004
April 1990
February 1990
Table 9 and Table 10 show the available rainfall and stream flow data for the selected calibration and verification events.
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Table 9 - Available Rainfall Data for Calibration and Verification
Station Feb Apr Feb Jun Jan Jan Station Name No 1990 1990 2004 2005 2008 2013 540352 Bonogin Ck AL 040981 Burleigh Waters AL 040717 Coolangatta 040717 Coolangatta AWS 540320 Coplicks Bridge AL 040609 Elanora Water Treatment 040524 Little Nerang Dam 540054 Little Nerang Dam AL 040417 Miami 040417 Miami 540353 Mt Nimmel AL 540254 Mudgeeraba AL 040606 Mudgeeraba Water 040558 Natural Br 040550 Natural Bridge 040162 Numinbah 040882 Numinbah AL 040162 Numinbah State 7002 Numinbah Tm 540252 Oyster Creek AL 040607 Springbrook AL 040700 Springbrook 040534 Springbrook 040192 Springbrook 040848 Springbrook Lower AL 040750 Springbrook Tm 7001 Springbrook Tm 540287 Tallai AL 540497 Upper Tallebudgera AL 040196 Tallebudgera 540366 Tallebudgera Ck Dam AL 540356 Tallebudgera Ck Rd AL 040899 Tallowood 58067 Tomewin (Border Gate) 540354 Tomewin AL 540400 Upper Springbrook AL
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Table 10 - Available Stream Flow Data for Calibration and Verification
Station Station Name Feb-90 Apr-90 Feb-04 Jun-05 Jan-08 Jan-13
540366 Tallebudgera Ck Dam AL 146095a Tallebudgera Ck Rd TM 540356 Tallebudgera Ck Rd AL 540320 Coplicks Br AL 540252 Oyster Ck AL
6.2 Calibration Methodology
The emphasis of the model calibration is to achieve the best possible fit between the modelled and recorded discharge hydrographs at key locations along the Tallebudgera Creek for the selected calibration events. For these locations, the calibration attempted to match the modelled and recorded flood peaks and volumes, and also the shape of the hydrographs. The calibrated model was then verified by comparing the model predictions against the rated discharge hydrographs available from various gauging stations for the selected verification events. A single set of global parameters (α, β, m and n) were adopted for all calibration events. In addition, uniform initial and continuing losses (IL and CL) were applied for the whole catchment for each event. The model parameters were adjusted to achieve the best calibration (i.e. achieve best timing and hydrograph shape) across all events. Initial and continuing losses were adjusted to match the commencement of the rising limb of the hydrograph and the hydrograph volume respectively. Where necessary, the reach length factors (f) were changed in the model to represent the differences in channel routing characteristics. Figure 11 shows the channel reaches for which reach length factors other than 1 have been applied.
Figure 11 – Location where Reach Length Factor other than 1
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6.3 Assignment of Rainfalls and Temporal Patterns
Rainfall depth and temporal pattern for each sub-catchment in the model were generated from the available pluviograph and daily rainfall data using an inverse distance squared method using the four nearest rainfall stations to the sub-catchment centroid. This method ensures that all of the available data are used and that the most appropriate rainfall temporal pattern is assigned to each sub-catchment. Table 11 below shows the weighted average rainfall at the selected locations for different events.
Table 11 – Weighted Average Rainfall at Selected Location Tallebudgera Ck Dam Tallebudgera Ck Rd Coplicks Br Event (mm) (mm) (mm)
Jan 2013 657 303 235 Jan 2008 384 267 215 Jun 2005 538 573 552 Feb 2004 230 211 165 Apr 1990 385 381 380 Feb 1990 277 213 168
6.4 Adopted Model Parameters
Table 12 shows the global catchment and channel parameters adopted for Tallebudgera Creek catchment for all calibration and verification events.
Table 12 - Adopted Parameters for Calibration and Verification Parameter Adopted Value α (Channel Lag) 0.11 (Catchment Lag) 1.6 m (Catchment non-linearity) 0.65 n 1 F F*0.5
6.5 Initial and Continuing Losses
Table 13 shows the adopted initial and continuing losses for each of the calibration and verification events. The adopted initial losses (30 – 120 mm) are generally consistent for all calibration and verification events. The adopted continuing losses (0.1 – 3.5 mm/hr) are also quite reasonable for all the events. The Table also shows that there is a strong positive correlation between the initial loss and continuing loss.
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Table 13 – Adopted Initial and Continues Losses Initial Loss Continues Loss Event IL (mm) CL (mm/hr) Jan 2013 120 3.5 Jan 2008 30 0.1 Jun 2005 100 1.5 Feb 2004 70 1.0 Apr 1990 30 2.5 Feb 1990 120 2.5
6.6 Calibration Results
6.6.1 General Comments Good calibration was achieved for the Tallebudgera Creek catchment. A single set of model parameters were adopted for all four calibration events. The quality of available rainfall data for all events was also good. Table 14 shows the comparison of recorded and modelled peak discharges at the key gauging stations for the calibration events.
Table 14 – Modelled and Recorded Peak Discharge at key locations for Tallebudgera Creek Catchment, Calibration Events Tallebudgera Ck Dam AL Tallebudgera Ck Rd AL Coplicks Bridge AL Peak Discharge Peak Discharge Peak Discharge Event (m3/s) (m3/s) (m3/s)
Modelled Recorded Modelled Recorded Modelled Recorded Jan 2013 244 200 378 384 446 432 Jan 2008 423 389 668 741 664 * Jun 2005 274 * 585 553 647** 482 Feb 2004 133 *** 229 230 238 *** *Station appears to have malfunctioned during the event **The peak discharge did not account the bypass at this location ***Data not available
Calibration results for individual events are discussed below:
6.6.2 January 2013 Event Intense rainfall occurred between 22 January 2013 and 29 January 2013 due to Ex-Tropical Cyclone Oswald. The Upper Springbrook gauging station recorded 744 mm in 24 hours to 9 am on the 28 January, 2013. This is the highest 24 hour rainfall total in Australia. Recorded rainfall data from Upper Springbrook, Tomewin, Little Nerang Dam, Mount Nimmel, Tallebudgera Creek Dam, Coplicks Bridge, Oyster Creek and Burleigh Water ALERTs were used for this calibration.
Table 14 above, Figure 14, Figure 15 and Figure 16 in the Appendix C: Calibration and Verification Plot show the comparison of the modelled and recorded discharges at Tallebudgera Creek Dam, Tallebudgera Creek Road and Coplicks Bridge Gauging Stations respectively. The plots show a good match between modelled and recorded discharges in terms of shape, peak, timing and volume of the hydrograph. It is of note that Tallebudgera Creek Road GS
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malfunctioned during the event, from 08:00pm on 26/01/2013 and Coplicks Bridge GS malfunctioned from 3:00am on 27/01/2013.
6.6.3 January 2008 Event Heavy rainfall occurred overnight on 04 January, 2008 in the Gold Coast hinterland area. Recorded rainfall data from Upper Springbrook, Lower Springbrook, Natural Bridge, Mount Nimmel, Tomewin, Tallowood, Tallebudgera Creek Dam, Tallebudgera Creek Road, Bonogin, Creek, Coplicks Bridge and Oyster Creek ALERTs are used for this calibration.
Table 14 above, Figure 17 and Figure 18 in Appendix C: Calibration and Verification Plot show the comparison of the modelled and recorded discharges at Tallebudgera Creek Dam and Tallebudgera Creek Road GS respectively for the January 2008 flood event. The calibration plots show a good match between modelled and recorded discharges in terms of shape, peak, timing and volume of the hydrograph. Coplicks Bridge AL appeared malfunctioning during the event since 03/01/2008 at 4:30 pm.
6.6.4 June 2005 Event An intense rainfall burst commenced in Gold Coast from 27 June 2005 to 30 June 2005. The heaviest rainfall occurred overnight on the 29th June and the following morning. Recorded rainfall from Lower Springbrook, Mount Nimmel, Tomewin, Tallowood, Tallebudgera Creek Dam, Tallebudgera Creek Road, Bonogin, Coplicks Bridge, Oyster Creek and Miami ALERTs are used for this calibration. at the key gauging stations for the calibration events.
Table 14 above and Figure 19, Figure 20 and Figure 21 in Appendix C: Calibration and Verification Plot show the comparison between the modelled and recorded discharges at Tallebudgera Creek Dam, Tallebudgera Creek Road and Coplicks Bridge GS respectively for the June 2005 flood event. Comparison plot at Tallebudgera Creek Dam shows a good match between modelled and recorded discharges in terms of shape and timing of the hydrographs. However, the peak does not match as it seems that the station was malfunctioning during the event on 30/06/2005 at 9:00 am and missed the second peak of the flood. The agreement between modelled and recorded discharges at Tallebudgera Creek Road GS is excellent. The shape and timing of the peak between modelled and recorded discharges at Coplicks Bridge GS are good. The recorded peak at this station is low because the rating table does not pick up the flows bypassing this station.
Overall very good calibration is achieved for this event.
6.6.5 February 2004 Event Recorded rainfall from Natural Bridge, Lower Springbrook, Mount Nimmel, Mudgeeraba, Bonogin, Tomewin, Tallowood, Tallebudgera Creek Road, Coplicks Bridge and Oyster Creek ALERTs are used for this calibration.
Table 14 above and Figure 22 in Appendix C: Calibration and Verification Plot show the comparison between modelled and recorded discharges at Tallebudgera Creek Road GS for the February 2004 flood event. An excellent match between modelled and recorded discharges was achieved for this event.
6.7 Verification Results
The calibrated URBS model was then simulated and verified against the recorded data for the April 1990 and February 1990 flood events using the same global parameters as derived for the calibration events. Table 15 shows the recorded and modelled peak discharges at Tallebudgera Creek Road gauging station for the verification events. Note that recorded data at the Camberra station are available only for the April 1972 and February 1972 events.
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Table 15 - Modelled and Recorded Peak Discharge at Tallebudgera Creek Road GS Tallebudgera Ck Dam AL Tallebudgera Ck Rd AL Coplicks Bridge AL Peak Discharge Peak Discharge Peak Discharge Event (m3/s) (m3/s) (m3/s)
Modelled Recorded Modelled Recorded Modelled Recorded Apr 1990 90 * 167 167 189 * Feb 1990 296 * 426 401 454 * *Data not available
6.7.1 April 1990 Event
Table 15 above and Figure 23 in Appendix C: Calibration and Verification Plot show the modelled and recorded discharges at Tallebudgera Creek Road GS for the April 1990 event. A good match between modelled and recorded discharges is achieved for this event.
6.7.2 February 1990 Event
Table 15 above and Figure 24 in the Appendix C: Calibration and Verification Plot show the modelled and recorded discharges at Tallebudgera Creek Road GS for the February 1990 event. Good match between modelled and recorded discharges is achieved for this event.
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7. Flood Frequency Analysis
7.1 Method of Analysis
Sufficient recorded annual peak discharge data was available from the Tallebudgera Creek Road Gauging Station (GS-146095A). Therefore, design flood discharges in the Tallebudgera Creek at Tallebudgera Creek Road GS were estimated by flood frequency analysis (FFA) using all available data. The methodology recommended in Book 4, Section 2 of Australian Rainfall and Runoff (1987) was used to fit a Log-Pearson Type III distribution to an annual series of recorded peak flood discharge at this location.
7.2 Available data
Annual peak gauge heights at the Tallebudgera Creek GS were available from DNRM for the period 1970 to 2013 (43 years). The recorded annual peak gauge heights were then converted to annual peak discharges using the rating table adopted for this study (Section 4.5.2 ).
7.3 Annual Peak Discharge Analysis
Figure 12 and Table 16 show the flood frequency distribution and the FFA estimated design peak discharges respectively at the Tallebudgera Creek Road gauging station.
Figure 12 - Flood Frequency Analysis @ Tallebudgera Creek Road Gauging Station
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Table 16 - FFA Estimated Peak Design Discharge @ Tallebudgera Creek Road GS FFA Estimated Peak Discharge (m3/s) 95% 5% ARI Confidence Fitted Confidence (Year) Limit Value Limit 2 159 184 213 5 255 303 360 10 317 393 487 20 368 490 652 50 420 634 958 100 448 758 1285 200 466 897 1728
FFA estimated design discharges in this study are compared with other methodologies and other studies in Section 9 of this report.
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8. Design Flood Estimation
The calibrated URBS model was then used to estimate the design flood discharges throughout the Tallebudgera Creek catchment using the design rainfall data described in Sections 8.2 , 8.3 and 8.4 . Design flood discharges were estimated for a range of storm durations including 0.5, 1.0, 1.5, 3.0, 4.5, 6.0, 9.0, 12.0, 18.0, 24.0, 36.0, 48.0 and 72 hours for the 2, 5, 10, 20, 50, 100, 200, 500, 1000 and 2000 year ARI events and for the Probable Maximum Precipitation Design Flood (PMPDF).
8.1 Methodology
WRM Water & Environment undertook a review of available design rainfall and associated procedures to determine the design rainfall data (IFD, Temporal Patterns, Areal Reduction Factors, Rainfall Spatial Distributions and Design Rainfall Losses) to be used for the City of Gold Coast area (12.13 ). The review recommended the methodology for use in design event hydrological modelling for catchments within the City of Gold Coast. The recommended methodology is summarized in Table 17 and it has been adopted in this study. During the course of this study, parallel studies for other catchments throughout the Gold Coast identified that methodology set out in Table 17 produced anomalous design results for ARI’s greater than 100 years. This was caused by the abrupt change in temporal patterns from the 100 year to the 200 year design bursts and secondly, inconsistencies found between the CRC- FORGE design rainfall intensities and those derived by AWE for the Gold Coast. For the Tallebudgera and Currumbin studies, these anomalies were not evident and, accordingly, the original procedure, as developed by WRM and presented in Table 17, was adopted.
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Table 17 - Summary of Recommended Methodology for Design Event Analysis Design Flood ARI Range Available Parameter Comment Recommendation (Years) Sources/Methods
Rainfall depth ≤100 ARR 1987 Industry standard approach.
AWE 1998 recommended for Gold Coast catchments. AWE 1992
recommended for Logan River catchment. Both methods use standard AWE 1998 a / AWE 1992 Uses same methodology as ARR 1987 with additional data. methodology with a longer period of recorded data.
Based on analysis of daily data. Adopted for Hinze Dam hydrology (HDA 2007) for events from 10 to CRCFORGE 2000 year ARI.
BoM Pilot Study Data was provided by BoM for investigation of Hinze Dam hydrology, but is no longer available.
ARR 1987 Industry standard approach. >100 - 500
AWE 1998 and AWE 1992 recommended for Gold Coast and Logan River AWE 1998 a / AWE 1992 Uses same methodology as ARR 1987 with additional data. catchments respectively for durations < 24 hours.
Based on analysis of daily data. Adopted for Hinze Dam hydrology (HDA 2007) for events from 10 to Recommended for durations ≥ 24 hours. Smoothen the transition between CRCFORGE 2000 year ARI. the two methods (i.e. between 12 and 24 hour depths).
Based on analysis of daily data. Adopted for Hinze Dam hydrology (HDA 2007) for events from 10 to Recommended. However, short duration rainfalls (< 24 hrs) subject to >500 - 2000 CRCFORGE 2000 year ARI. substantial uncertainty. Detailed investigation may be warranted where this ARI range is of critical interest.
Interpolate between No explicit methodology is available to estimate rainfall depths for events of this magnitude. Section 2000 - < PMP Recommended. CRCFORGE & PMP 3.6.3 of ARR 1999 provides a methodology for interpolation. methods.
PMPDF GSDM (≤ 6 hours) Industry standard approach. Recommended. GTSMR (> 6 hours)
Areal Reduction Factors <2000 ARR 1987 Based on United States data.
CRC ARF Derived from regional data for durations ≥ 24 hours. Recommended. Adopt 24 hour duration ARFs for durations less than 24 hours. Verify using flood frequency analysis where possible.
Interpolate between Interpolate as recommended by ARR 1999 Section 3.6 using CRCFORGE and PMP rainfalls which are 2000 - PMP GSDM (≤ 6 hours) Industry standard approach. Recommended. GTSMR (> 6 hours) Industry standard approach. Recommended for Logan River catchment. Temporal Pattern ≤100 ARR 1987 Uses same methodology as ARR 1987 with additional data. Alternative patterns derived for ARI > 30 Use of filtered AWE (2000) patterns recommended for Gold Coast years (but only recommended for sensitivity analysis). AWE 2000 patterns have been filtered by WRM catchments. Note these patterns do not cover the Logan River catchment. AWE 2000 to eliminate sub-duration inconsistencies. Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1-TALLEBUDGERA_CREEK_CATCHMENT_HYDROLOGICAL_STUDY__AUGUST_2014 Page 41 of 76 Design Flood ARI Range Available Parameter Comment Recommendation (Years) Sources/Methods UWS 2006 Uses same methodology as ARR 1987 & AWE 2000 with additional data. Recommended. Use 24 hour patterns for 12 and 18 hour events and use >100 - GSDM (≤ 6 hours) Recommended. Use 24 hour patterns for 12 and 18 hour events and use PMP Industry standard approach. GTSMR (> 6 hours) 6 hour pattern for the 9 hour event. Spatial Distribution ≤100 AWE 1998 a Estimate design rainfall at the centroid of each model sub-catchment and apply ARF based on whole Recommended. catchment, as recommended in ARR 1987. >100 – 2000 CRCFORGE Estimate CRCFORGE rainfall at the centroid of each model sub-catchment. Recommended. >2000 - PMP GSDM (≤ 6 hours) Adopt PMP spatial distribution for events greater than 2000 year ARI as recommended by ARR 1999. Recommended. GTSMR (> 6 hours) Very little Queensland data used in recommended loss values for Queensland. Suggests Initial losses Rainfall Losses ≤100 ARR 1987 in the range 15-35mm and a continuing loss rate of 2.5mm/hr. Recommends adoption of median values from catchment-specific model calibration. Comprehensive study based on data for 48 Queensland catchments. Estimated the median initial and Recommended. Adopt 38mm for initial loss and median continuing loss Ilahee 2005 continuing loss rates for eastern Queensland catchment to be 38mm and 1.52mm/hr respectively. values from catchment specific model calibration. Interpolate losses between 100 year ARI and PMP Design Flood using approach recommended by >100 - PMP ARR 1999 Adopt minimum values from catchment-specific model calibration, as recommended by ARR 1999. Recommended . Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1-TALLEBUDGERA_CREEK_CATCHMENT_HYDROLOGICAL_STUDY__AUGUST_2014 Page 42 of 76 8.2 Frequent to Large Design Events (up to and including 100 Year ARI) 8.2.1 Rainfall Depth Estimation Design rainfall intensities at the centroid of each sub-area were determined using the Council’s Intensity Frequency Distribution utility program (WRM 2008b 12.11 ) for storm durations up to 72 hours for all ARIs up to and including 100 years. The average rainfall intensities for each duration and ARI were then converted to rainfall depths. The IFD calculation parameters were originally based on ‘Review of Gold Coast Rainfall Data’ (AWE, 1998 12.6 ). The AWE study produced a revised set of design rainfall intensity maps and F2 and F50 factor maps for the City of Gold Coast area. These maps replaced Maps 1.5, 6.5 and Map 8 and 9, Volume 2 of IEAust (1998) for the City area. In the AWE 1998 study the skew coefficient for Gold Coast was adopted as zero. WRM updated Council’s IFD utility by introducing a skew coefficient as per section 1, book II volume 1 of IEAust (1998) in 2008. 8.2.2 Areal Reduction Factors The point design rainfall estimates at the centroid of each sub-area were converted to average values for each sub-area using Areal Reduction Factors (ARFs). The Queensland Extreme Rainfall Estimation Project (EREP, Hargraves c.2004)) developed the following relationship between ARF, catchment area and storm duration for Queensland catchments: ARF = 1 – 0.226 X (Area0.1685 – 0.8306 X log (Duration)) X Duration-0.3994 Where ARF = Areal Reduction Factor Area = Catchment Area in Km2 and Duration = Storm Duration in Hours The derivation of the EREP ARF equation was based on daily rainfall data. Hence, the applicability of ARFs derived from the above equation for durations shorter than 24 hours is uncertain. For consistency with the approach adopted in two recent major dam design studies in the study area, namely the Hinze Dam upgrade study in the Nerang River catchment (HDA, 2007) and Wyaralong Dam design study in the Logan River catchment (Sunwater, 2007), the 24 hour ARFs were adopted in this study for durations shorter than 24 hours. Table 18 shows the adopted ARFs for design event simulation. The ARF calculation for design event simulation was based on total catchment area, and for comparison with FFA results, the ARF calculation was based on the catchment area upstream of Tallebudgera Creek Road gauging station. TRACKS-#45381530-v1- TALLEBUDGERA_CREEK_CATCHMENT_HYDROLOGICAL_STUDY__AUGUST_201 4 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 43 of 76 Table 18 - Adopted Aerial Reduction Factors for Tallebudgera Creek Catchment Aerial Reduction Factor Catchment U/S of Storm Duration (Hour) Total Catchment Tallebudgera Ck Rd GS Area(97.6 km2) (56.4 km2) 72 0.975 0.982 48 0.963 0.972 36 0.953 0.963 24 0.935 0.948 18 0.935 0.948 12 0.935 0.948 9 0.935 0.948 6 0.935 0.948 4.5 0.935 0.948 3 0.935 0.948 1.5 0.935 0.948 1 0.935 0.948 0.5 0.935 0.948 8.2.3 Temporal Patterns A sub-duration inconsistency within the temporal patterns currently adopted by Council (AWE, 2000) has been identified recently. These temporal patterns developed by AWE (2000), which have been adopted by Council since 2000, produces design rainfalls that contain bursts of higher ARI than the ARI of the design burst itself for a given duration. For instance at a number of locations the 72 hour storm temporal pattern has within it 6 hour, 12 hour, 24 hour and 48 hour design rainfalls that are larger than the equivalent design rainfalls given by the 6 hour, 12 hour, 24 hour and 48 hour burst temporal patterns. Further this problem is present for the full range of ARI’s from 2 to 100 years. The inconsistencies within the AWE (2000) temporal patterns produce unrealistically long critical storm durations for Gold Coast catchments. As part of WRM’s study, the sub-duration/burst inconsistencies within the AWE (2000) patterns were filtered and smoothened by adjusting the longer duration storm temporal patterns according to the methodology outlined in Australian Rainfall and Runoff (1998) and BoM (1991). The filtering and smoothing were undertaken until the inconsistencies were removed for all ARI’s up to 100 years, whilst maintaining the basic shape and integrity of the patterns. Table 19 shows the adopted temporal patterns for ARI’s up to and including 100 years. TRACKS-#45381530-v1- TALLEBUDGERA_CREEK_CATCHMENT_HYDROLOGICAL_STUDY__AUGUST_201 4 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 44 of 76 Table 19 - Adopted Temporal Patterns for All Storm Durations and ARI’s up to 100 Years PERIOD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 10 MINUTE DURATION in 2 PERIODS OF 5 MINUTES ARI<=30 0.399 0.601 ARI>30 0.459 0.541 15 MINUTE DURATION in 3 PERIODS OF 5 MINUTES ARI<=30 0.322 0.452 0.226 ARI>30 0.339 0.408 0.253 20 MINUTE DURATION in 4 PERIODS OF 5 MINUTES ARI<=30 0.195 0.36 0.261 0.184 ARI>30 0.204 0.338 0.269 0.189 25 MINUTE DURATION in 5 PERIODS OF 5 MINUTES ARI<=30 0.159 0.31 0.225 0.177 0.129 ARI>30 0.166 0.296 0.218 0.187 0.133 30 MINUTE DURATION in 6 PERIODS OF 5 MINUTES ARI<=30 0.139 0.266 0.202 0.156 0.124 0.113 ARI>30 0.139 0.256 0.195 0.17 0.12 0.12 45 MINUTE DURATION in 9 PERIODS OF 5 MINUTES ARI<=30 0.084 0.102 0.112 0.199 0.153 0.12 0.094 0.072 0.064 ARI>30 0.086 0.097 0.104 0.201 0.153 0.122 0.094 0.077 0.066 1 HOUR DURATION in 12 PERIODS OF 5 MINUTES ARI<=30 0.055 0.082 0.095 0.11 0.104 0.178 0.08 0.073 0.062 0.057 0.055 0.049 ARI>30 0.059 0.075 0.084 0.113 0.11 0.177 0.079 0.066 0.062 0.06 0.058 0.057 1.5 HOUR DURATION in 18 PERIODS OF 5 MINUTES ARI<=30 0.034 0.048 0.067 0.073 0.121 0.082 0.061 0.06 0.057 0.053 0.043 0.052 0.044 0.044 0.042 0.041 0.04 0.038 ARI>30 0.044 0.047 0.064 0.068 0.11 0.088 0.056 0.061 0.06 0.053 0.048 0.053 0.044 0.043 0.042 0.041 0.04 0.038 2 HOUR DURATION in 24 PERIODS OF 5 MINUTES ARI<=30 0.028 0.034 0.046 0.095 0.08 0.052 0.068 0.056 0.044 0.041 0.037 0.035 0.032 0.03 0.033 0.041 0.033 0.036 0.033 0.032 0.029 0.031 0.028 0.026 ARI>30 0.034 0.034 0.052 0.087 0.068 0.048 0.062 0.054 0.048 0.044 0.036 0.038 0.034 0.034 0.035 0.039 0.033 0.037 0.035 0.033 0.032 0.032 0.027 0.024 3 HOUR DURATION in 12 PERIODS OF 15 MINUTES ARI<=30 0.066 0.121 0.158 0.097 0.073 0.068 0.059 0.078 0.111 0.062 0.055 0.052 ARI>30 0.072 0.117 0.158 0.091 0.075 0.071 0.064 0.074 0.105 0.061 0.059 0.053 4.5 HOUR DURATION in 18 PERIODS OF 15 MINUTES ARI<=30 0.088 0.061 0.045 0.071 0.048 0.055 0.035 0.075 0.117 0.086 0.046 0.032 0.04 0.037 0.03 0.046 0.052 0.036 ARI>30 0.077 0.066 0.047 0.07 0.049 0.056 0.04 0.065 0.109 0.079 0.048 0.04 0.039 0.037 0.034 0.049 0.056 0.039 6 HOUR DURATION in 12 PERIODS OF 30 MINUTES ARI<=30 0.058 0.061 0.073 0.096 0.172 0.066 0.135 0.077 0.064 0.045 0.099 0.054 ARI>30 0.061 0.069 0.074 0.102 0.153 0.072 0.122 0.082 0.068 0.048 0.098 0.051 PERIOD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 45 of 76 Adopted Temporal Patterns for All Storm Durations and ARI’s up to 100 Years (Continued) PERIOD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 9 HOUR DURATION in 18 PERIODS OF 30 MINUTES ARI<=30 0.038 0.043 0.026 0.034 0.049 0.045 0.061 0.071 0.085 0.074 0.117 0.067 0.058 0.052 0.037 0.029 0.069 0.045 ARI>30 0.037 0.044 0.03 0.038 0.056 0.045 0.058 0.069 0.082 0.072 0.112 0.067 0.057 0.054 0.041 0.029 0.069 0.04 12 HOUR DURATION in 24 PERIODS OF 30 MINUTES ARI<=30 0.032 0.025 0.026 0.028 0.031 0.032 0.035 0.044 0.051 0.04 0.046 0.074 0.047 0.097 0.058 0.053 0.044 0.033 0.037 0.025 0.03 0.045 0.036 0.031 ARI>30 0.033 0.025 0.028 0.033 0.039 0.035 0.038 0.042 0.047 0.038 0.047 0.072 0.044 0.095 0.055 0.049 0.044 0.038 0.038 0.025 0.031 0.042 0.033 0.029 18 HOUR DURATION in 18 PERIODS OF 1 HOUR ARI<=30 0.035 0.027 0.023 0.047 0.049 0.071 0.09 0.144 0.05 0.078 0.07 0.057 0.063 0.052 0.042 0.034 0.039 0.029 ARI>30 0.036 0.027 0.022 0.048 0.052 0.068 0.095 0.14 0.05 0.076 0.067 0.048 0.065 0.052 0.044 0.037 0.042 0.031 24 HOUR DURATION in 24 PERIODS OF 1 HOUR ARI<=30 0.033 0.02 0.025 0.02 0.024 0.038 0.049 0.054 0.038 0.051 0.061 0.068 0.115 0.031 0.065 0.079 0.042 0.036 0.026 0.03 0.024 0.034 0.02 0.017 ARI>30 0.034 0.017 0.025 0.019 0.025 0.036 0.051 0.055 0.034 0.053 0.062 0.069 0.122 0.03 0.064 0.078 0.037 0.034 0.024 0.029 0.022 0.033 0.025 0.022 30 HOUR DURATION in 15 PERIODS OF 2 HOURS ARI<=30 0.039 0.036 0.031 0.039 0.042 0.057 0.063 0.099 0.082 0.171 0.13 0.068 0.046 0.039 0.058 ARI>30 0.051 0.047 0.039 0.036 0.038 0.057 0.06 0.098 0.079 0.179 0.119 0.068 0.041 0.035 0.053 36 HOUR DURATION in 18 PERIODS OF 2 HOURS ARI<=30 0.035 0.025 0.028 0.034 0.036 0.069 0.04 0.047 0.058 0.034 0.152 0.089 0.077 0.118 0.059 0.037 0.034 0.028 ARI>30 0.039 0.031 0.028 0.036 0.032 0.065 0.036 0.043 0.059 0.036 0.143 0.099 0.083 0.109 0.065 0.037 0.032 0.027 48 HOUR DURATION in 24 PERIODS OF 2 HOURS ARI<=30 0.024 0.022 0.023 0.023 0.032 0.034 0.025 0.036 0.027 0.037 0.035 0.055 0.135 0.089 0.062 0.034 0.053 0.087 0.035 0.041 0.028 0.023 0.02 0.02 ARI>30 0.028 0.025 0.024 0.021 0.03 0.032 0.021 0.036 0.027 0.035 0.035 0.058 0.118 0.093 0.067 0.041 0.059 0.086 0.033 0.041 0.025 0.023 0.021 0.021 72 HOUR DURATION in 18 PERIODS OF 4 HOURS ARI<=30 0.063 0.029 0.042 0.073 0.047 0.034 0.092 0.117 0.168 0.061 0.042 0.039 0.039 0.034 0.032 0.031 0.029 0.028 ARI>30 0.065 0.034 0.042 0.067 0.045 0.033 0.08 0.111 0.169 0.068 0.048 0.039 0.038 0.035 0.034 0.033 0.03 0.029 PERIOD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 46 of 76 8.2.4 Spatial Distribution The design rainfalls for durations from 30 minutes to 72 hours for all ARI’s up to and including 100 years were estimated at the centroid of each model sub-catchment as described in Section 8.2.1. This is in accordance with the methodology described in Table 17. 8.2.5 Rainfall Losses The Initial Loss (IL) and Continuing Loss (CL) for design event simulations up to 100 year ARI were adopted as per Table 20 below: Table 20 - Adopted Initial and Continuing Loss Rates ARI Adopted Loss (Years) IL (mm) CL (mm/hr) 2 50 3.5 5 40 3.0 10 30 3.0 20 25 3.0 50 20 2.5 100 10 2.0 8.2.6 Design Peak Discharge Table 21 and Table 22 show the design discharges and critical storm durations respectively at key locations throughout the Tallebudgera Creek catchment for ARI’s up to 100 years. It is of note that for all design event simulations the applied ARF was calculated based on total catchment area. Table 21 - Peak Design Discharge at Key Locations, 2 to 100 Year ARI Peak Design Discharge (m3/s) 2 5 10 20 50 100 Location Stream Name Year Year Year Year Year Year ARI ARI ARI ARI ARI ARI Tallebudgera Ck Dam AL Tallebudgera Ck 120 215 273 339 421 492 Tallebudgera Ck Rd AL Tallebudgera Ck 178 323 410 507 629 737 Coplicks Br AL Tallebudgera Ck 187 348 440 547 686 805 Oyster Ck AL Oyster Ck 12 20 24 29 36 41 Catchment Outlet Tallebudgera Ck 194 346 440 547 690 816 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 47 of 76 Table 22 - Critical Storm Duration at Key Locations, 2 to 100 Year ARI Critical Storm Duration (Hrs) 2 5 10 20 50 100 Location Stream Name Year Year Year Year Year Year ARI ARI ARI ARI ARI ARI Tallebudgera Ck Dam AL Tallebudgera Ck 12.0 12.0 9.0 9.0 9.0 9.0 Tallebudgera Ck Rd AL Tallebudgera Ck 12.0 12.0 9.0 9.0 9.0 9.0 Coplicks Br AL Tallebudgera Ck 12.0 12.0 9.0 9.0 9.0 9.0 Oyster Ck AL Oyster Ck 9.0 9.0 3.0 3.0 3.0 3.0 Catchment Outlet Tallebudgera Ck 24.0 12.0 12.0 12.0 12.0 12.0 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 48 of 76 8.3 Rare Design Events (200 to 2000 Year ARI) 8.3.1 Rainfall Depth Estimation The design rainfall depths for the rare events were estimated using the guidelines listed in Table 23 below: Table 23 - Design Rainfall Depth Estimation Event Storm Duration Adopted Methodology 200 to 500 Year ARI Up to 12 hours Updated AWE 1998 Interpolated between updated AWE 18 hours 1998 and CRC Forge 24 to 72 hours CRC Forge (Hargraves, 2004) 1000 to 2000 Year ARI Up to 72 hours CRC Forge 8.3.2 Areal Reduction Factors The Areal Reduction Factors (ARF) were applied to 200, 500, 1000 and 2000 Year ARI design rainfalls as described in the Section 8.2.2 . 8.3.3 Temporal Patterns The design rainfall temporal patterns for the rare design events were sourced from ‘The Estimation of Probable Maximum Precipitation in Australia: Generalised Short Duration Method’ (GSDM, BoM, 2003a) and the ‘Generalised Tropical Storm method (GTSMR, BoM, 2003b)’ as outlined in. Table 24. Table 25 shows the adopted rainfall temporal patterns for rare to extreme design events. Table 24 - Design Rainfall Temporal Patterns Event Storm Duration Adopted 200 to 2000 Year ARI Up to 6 hours GSDM 9 Hours Extrapolated from GSDM 12 and 18 Hours Extrapolated from GTSMR 24 to 72 hours GTSMR Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 49 of 76 Table 25 - Adopted Design Rainfall Temporal Patterns for 200 to 2000 Year ARI PERIOD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 30 MINUTE DURATION in 6 PERIODS OF 5 MINUTES Area 100Km2 0.204 0.237 0.205 0.172 0.124 0.059 Area 500Km2 0.204 0.237 0.205 0.172 0.124 0.059 1 HOUR DURATION in 12 PERIODS OF 5 MINUTES Area 100Km2 0.081 0.123 0.121 0.116 0.108 0.097 0.088 0.084 0.073 0.051 0.038 0.021 Area 500Km2 0.081 0.123 0.121 0.116 0.108 0.097 0.088 0.084 0.073 0.051 0.038 0.021 1.5 HOUR DURATION in 18 PERIODS OF 5 MINUTES Area 100Km2 0.051 0.068 0.085 0.083 0.077 0.076 0.072 0.068 0.065 0.061 0.056 0.055 0.05 0.042 0.032 0.027 0.019 0.013 Area 500Km2 0.051 0.068 0.085 0.083 0.077 0.076 0.072 0.068 0.065 0.061 0.056 0.055 0.05 0.042 0.032 0.027 0.019 0.013 3 HOUR DURATION in 12 PERIODS OF 15 MINUTES Area 100Km2 0.081 0.123 0.121 0.116 0.108 0.097 0.088 0.084 0.073 0.051 0.038 0.021 Area 500Km2 0.081 0.123 0.121 0.116 0.108 0.097 0.088 0.084 0.073 0.051 0.038 0.021 4.5 HOUR DURATION in 18 PERIODS OF 15 MINUTES Area 100Km2 0.051 0.068 0.085 0.083 0.077 0.076 0.072 0.068 0.065 0.061 0.056 0.055 0.05 0.042 0.032 0.027 0.019 0.013 Area 500Km2 0.051 0.068 0.085 0.083 0.077 0.076 0.072 0.068 0.065 0.061 0.056 0.055 0.05 0.042 0.032 0.027 0.019 0.013 6 HOUR DURATION in 12 PERIODS OF 30 MINUTES Area 100Km2 0.081 0.123 0.121 0.116 0.108 0.097 0.088 0.084 0.073 0.051 0.038 0.021 Area 500Km2 0.081 0.123 0.121 0.116 0.108 0.097 0.088 0.084 0.073 0.051 0.038 0.021 9 HOUR DURATION in 9 PERIODS OF 1 HOUR Area 100Km2 0.117 0.160 0.152 0.146 0.130 0.110 0.089 0.063 0.036 Area 500Km2 0.121 0.159 0.146 0.143 0.136 0.113 0.089 0.061 0.035 12 HOUR DURATION in 12 PERIODS OF 1 HOUR Area 100Km2 0.080 0.112 0.113 0.112 0.114 0.116 0.086 0.077 0.067 0.053 0.043 0.027 Area 500Km2 0.087 0.111 0.111 0.101 0.108 0.118 0.098 0.082 0.067 0.050 0.042 0.026 18 HOUR DURATION in 12PERIODS OF 1.5 HOUR Area 100Km2 0.074 0.104 0.105 0.113 0.121 0.133 0.084 0.072 0.06 0.057 0.049 0.031 Area 500Km2 0.091 0.100 0.099 0.092 0.107 0.139 0.108 0.078 0.061 0.053 0.044 0.029 24 HOUR DURATION in 8 PERIODS OF 3 HOUR Area 100Km2 0.119 0.141 0.168 0.223 0.125 0.074 0.097 0.053 Area 500Km2 0.143 0.129 0.109 0.238 0.178 0.069 0.085 0.050 36 HOUR DURATION in 12 PERIODS OF 3 HOURS Area 100Km2 0.053 0.034 0.070 0.089 0.055 0.062 0.107 0.094 0.185 0.132 0.076 0.043 Area 500Km2 0.033 0.046 0.052 0.098 0.074 0.053 0.115 0.177 0.131 0.091 0.060 0.069 PERIOD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 TRACKS-#45381530-v1-TALLEBUDGERA_CREEK_CATCHMENT_HYDROLOGICAL_STUDY__AUGUST_2014 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 50 of 76 Adopted Design Rainfall temporal patterns for 200 to 2000 Year ARI Events (Continued) PERIOD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 48 HOUR DURATION in 16 PERIODS OF 3 HOURS Area 100Km2 0.062 0.039 0.019 0.040 0.058 0.054 0.065 0.114 0.148 0.076 0.050 0.089 0.081 0.032 0.028 0.043 Area 500Km2 0.062 0.048 0.022 0.042 0.059 0.052 0.085 0.093 0.140 0.079 0.037 0.110 0.071 0.025 0.040 0.033 72 HOUR DURATION in 24 PERIODS OF 3 HOURS Area 100Km2 0.044 0.053 0.077 0.125 0.064 0.010 0.034 0.071 0.083 0.039 0.025 0.008 0.006 0.017 0.022 0.028 0.015 0.059 0.094 0.048 0.033 0.020 0.011 0.013 Area 500Km2 0.037 0.056 0.074 0.068 0.046 0.013 0.022 0.035 0.115 0.042 0.018 0.015 0.009 0.040 0.021 0.061 0.027 0.051 0.096 0.081 0.025 0.030 0.007 0.012 PERIOD 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 TRACKS-#45381530-v1-TALLEBUDGERA_CREEK_CATCHMENT_HYDROLOGICAL_STUDY__AUGUST_2014 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 51 of 76 8.3.4 Spatial Distribution The design rainfalls for durations from 30 minutes to 72 hours for all ARIs between 200 and 2000 Year were estimated at the centroid of each model sub-catchment as described in Section 8.3.1 . This is in accordance with the methodology described in Table 17. 8.3.5 Losses The Initial Loss (IL) and the Continuing Loss (CL) for design event simulations for 200 to 2000 year ARI were adopted as per Table 26 below: Table 26 – Adopted Initial and Continuing Losses for 200 to 2000 Year ARI ARI Adopted Loss (Years) IL (mm) CL (mm/hr) 200 0.0 1.5 500 0.0 0.5 1000 0.0 0.0 2000 0.0 0.0 8.3.6 Design Discharges Table 27 and Table 28 below show the design discharges and critical storm durations respectively at key locations throughout the Tallebudgera Creek catchment for 200 to 2000 year ARI events. Table 27 - Design Discharge at Key Locations, 200 to 2000 Year ARI Peak Design Discharge (m3/s) 200 500 1000 2000 Location Stream Name Year Year Year Year ARI ARI ARI ARI Tallebudgera Ck Dam AL Tallebudgera Ck 555 653 843 937 Tallebudgera Ck Rd AL Tallebudgera Ck 860 1010 1274 1407 Coplicks Bridge AL Tallebudgera Ck 930 1092 1332 1462 Oyster Ck AL Oyster Ck 50 58 76 83 Catchment Outlet Tallebudgera Ck 960 1139 1284 1421 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 52 of 76 Table 28 – Critical Storm Duration at Key Locations, 200 to 2000 Year ARI Critical Storm Duration (hours) 200 500 1000 2000 Location Stream Name Year Year Year Year ARI ARI ARI ARI Tallebudgera Ck Dam AL Tallebudgera Ck 4.5 4.5 3.0 3.0 Tallebudgera Ck Rd AL Tallebudgera Ck 4.5 4.5 3.0 3.0 Coplicks Bridge AL Tallebudgera Ck 6.0 6.0 4.5 4.5 Oyster Ck AL Oyster Ck 3.0 3.0 3.0 3.0 Catchment Outlet Tallebudgera Ck 24.0 36.0 9.0 36.0 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 53 of 76 8.4 Extreme Design Events - Probable Maximum Precipitation Design Flood (PMPDF) 8.4.1 Rainfall Depth Estimation PMP rainfall depths for durations up to 6 hours were estimated using the methodology given in the Estimation of Probable Maximum Precipitation in Australia: Generalised Short Duration Method (GSDM, BoM 2003a). The PMP rainfall depths for 24 to 72 hour durations were estimated using the standard methodology given in the Generalised Tropical Storm Method (GTSMR, BoM 2003b). The PMP depths for 12 and 18 hour durations were obtained by extrapolating the GTSMR estimates and the PMP depths for 9 hour duration were estimated by extrapolating the GSDM estimates. A smooth transition between GSDM and GTSMR estimates was also adopted. 8.4.2 Areal Reduction Factors Areal Reduction Factors are already included in the GSDM and GTSMR methodology (BoM 2003a and BoM 2003b) so the additional ARFs are not required to apply on individual sub-area rainfall. 8.4.3 Temporal Patterns The temporal patterns for durations up to 6 hours were obtained from the GSDM and the durations from 24 to 72 hours were obtained from the GTSMR methodology. The temporal patterns for the 12 and 18 hour durations were extrapolated from the GTSMR and the temporal patterns for the 9 hour duration were extrapolated from the GSDM. A smooth transition between GSDM and GTSMR estimates was also adopted. 8.4.4 Spatial Distribution Rainfall spatial distributions are already included in the GSDM and GTSMR rainfall depth estimation methodology. 8.4.5 Losses An initial loss (IL) of 0.0 mm and continuing loss (CL) of 0.1 mm/hr were adopted for all the durations of PMPDF. 8.4.6 Design Discharges Table 29 shows the PMPDF discharge and critical storm duration at key locations throughout the Tallebudgera Creek catchment. Table 29 - Design Discharge and Critical Storm Duration at Key Locations for PMPDF PMPDF Location Stream Name Peak Design Critical Discharge Storm Duration (m3/s) (hours) Tallebudgera Ck Dam AL Tallebudgera Ck 1830 3.0 Tallebudgera Ck Rd AL Tallebudgera Ck 2979 3.0 Coplicks Bridge AL Tallebudgera Ck 2930 9.0 Oyster Ck AL Oyster Ck 146 3.0 Catchment Outlet Tallebudgera Ck 3146 12.0 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 54 of 76 8.5 Joint Probability Approach The Joint Probability Approach (JPA) is also known as Monte Carlo simulation technique has been under development for past few years culminating in a publication by the ARR in 2013. There are two Monte Carlo techniques available: the Total Probability Theorem (TPT) developed by Nathan, Weinmann and Kuczera (Laurenson et al. 2005) and Cooperative Research Centre – Catchment Hydrology (CRC-CH) developed by Rahman (et al. 2001 and 2002a). The TPT methodology is based on current critical storm duration approach however the CRC-CH methodology is based on design storms of variable storm durations. In the TPT methodology the BOM burst IFD tables are used whereas event based IFD tables derived from the raw pluviographs are used in the CRC-CH methodology. Don Carroll Project Management developed a relationship between the complete storm IFD table and the burst IFD table for Gold Coast region as part of Council’s Hydrological Study Review in April 2013 (12.18 ). The following relationships are established based on raw pluvio data from the BOM. q r Ie = p D T Ib Where I is intensity (mm/hour) D is duration (hours) T is ARI (years) b is burst e is event and p, q and r are constant. For the Gold Coast region Don Carroll Project Management recommended the following values: p = 0.1 x 12D24 – 0.25 q = 0.6 x (1 – p) r = - 0.025 The mean duration is 0.9 x 12D241.56 where 12D24 is the 2 year 24 hour burst intensity. It is of note that both approaches have some limitations. The TPT is developed for large to extreme floods and its applications for more frequent events are questionable. The CRC-CH often applied in the derivation of design flow estimates up to large floods so this approach is not robust in the estimation of rare and extreme floods. In this study the TPT and CRC-CH Monte Carlo simulations are undertaken only to verify the results of Design Event Approach. 8.5.1 TPT The adopted steps in TPT can be summarized as below: Choose a range of storm durations around the critical storm duration from the Design Event Approach (DEA). Generate thousands of rainfall bursts through stratified sampling of the rainfall frequency curve. Randomly select a temporal pattern from the database obtained from the pluvio data. Apply random initial loss and fixed continuing loss. Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 55 of 76 Table 30 shows the adopted parameters and losses for TPT. Table 30 - Adopted Parameters and Losses for TPT Adopted Parameters and Losses α 0.11 β 1.6 m 0.65 n 1 F F*0.5 CL (mm/hr) 2.5 Min IL (mm) 0 Stdv IL (mm) 30 Mean IL (mm) 30 Max IL (mm) 100 Table 31 shows the peak design discharge at key locations within the catchment estimated by TPT Monte Carlo simulations for 2 year to 2000 year ARI. Table 31 - Design Discharge at Key Locations, 2 to 2000 Year ARI estimated by TPT 3 TPT MC Peak Design Discharge (m /s) 2 5 10 20 50 100 200 500 1000 2000 Location Year Year Year Year Year Year Year Year Year Year ARI ARI ARI ARI ARI ARI ARI ARI ARI ARI Talle Ck Dam 159 231 297 368 463 532 631 725 809 888 Talle Ck Rd 237 340 436 531 660 769 893 1035 1173 1305 Coplicks Br 261 370 477 574 705 828 952 1114 1252 1445 Oyster Ck AL 17 23 28 33 39 46 53 62 72 81 Outlet 249 358 449 552 671 782 903 1090 1253 1453 Table 32 shows the critical storm duration at key locations within the catchment estimated by TPT Monte Carlo simulations for 2 year to 2000 year ARI. Table 32 - Critical Storm Duration at Key Locations, 2 to 2000 Year ARI estimated by TPT TPT MC Critical Storm Duration (hours) 2 5 10 20 50 100 200 500 1000 2000 Location Year Year Year Year Year Year Year Year Year Year ARI ARI ARI ARI ARI ARI ARI ARI ARI ARI Talle Ck Dam 4.5 12.0 12.0 9.0 12.0 9.0 9.0 9.0 9.0 4.5 Talle Ck Rd 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 6.0 4.5 Coplicks Br 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 6.0 36.0 Oyster Ck AL 4.5 3.0 3.0 3.0 4.5 3.0 3.0 3.0 3.0 4.5 Outlet 12.0 12.0 9.0 12.0 18.0 12.0 18.0 24.0 36.0 36.0 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 56 of 76 8.5.2 CRC-CH The adopted steps in CRC-CH can be summarized as below: The event duration is selected from an exponential or gamma probability distribution fitted to the available pluvio data, A conditional distribution in the form of IFD is established, Temporal patterns are randomly selected based on multiplicative cascade model or optionally from a database populated with temporal patterns from historical storms and Thousands of combinations of the design inputs are generated and routed through the runoff routing model. Table 33 shows the adopted parameters and losses for CRC-CH Table 33 - Adopted Parameters and Losses for CRC-CH Adopted Parameters and Losses α 0.11 β 1.6 m 0.65 n 1 F F*0.5 CL (mm/hr) 2.5 Min IL (mm) 0 Stdv IL (mm) 30 Mean IL (mm) 30 Max IL (mm) 100 Table 34 shows the peak design discharge at key locations within the catchment estimated by CRC-CH Monte Carlo simulations for 2 year to 2000 year ARI. Table 34 - Design Discharge at Key Locations, 2 to 2000 Year ARI estimated by CRC-CH 3 CRC-CH MC Peak Design Discharge (m /s) 2 5 10 20 50 100 200 Location Year Year Year Year Year Year Year ARI ARI ARI ARI ARI ARI ARI Talle Ck Dam AL 144 209 266 327 442 528 657 Talle Ck Rd AL 202 293 371 463 596 799 903 Coplicks Br AL 213 308 390 483 617 812 950 Oyster Ck AL 23 32 39 47 62 74 86 Outlet 222 322 399 499 616 784 932 It is of note that all the design discharges estimated in Section 8, the ARF calculation is based on total catchment area and for comparison with the other approaches in section 9 the ARF calculation is based on the catchment area upstream of Tallebudgera Creek Road gauging station only. The JPA estimated design peak discharges in this study are compared with other methodologies and other studies in Section 9 of this report. Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 57 of 76 9. Comparison In the current study the peak design discharge at Tallebudgera Creek Road Gauging Station (GS) was estimated using the Design Event Approach (DEA), Flood Frequency Analysis (FFA), Total Probability Theorem Monte Carlo (TPT MC) and Cooperative Research Centre – Catchment Hydrology Monte Carlo (CRC-CH MC) simulations. Figure 13 shows the peak design discharge for different ARIs at Tallebudgera Creek Road GS as estimated by DEA, FFA, TPT MC and CRC-CH MC approach. As the comparison is made at Tallebudgera Creek Road GS so the adopted ARF for all estimations were based on catchment area upstream of Tallebudgera Creek Road GS. Figure 13 - Peak Design Discharge comparison plot for different modelling methodologies Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 58 of 76 Table 35 shows the peak design discharges at Tallebudgera Creek Road GS estimated by different modelling approaches for different ARIs from the current and previous studies. Table 35 - Peak Design Discharge estimated by different modelling approach from current and previous studies at Tallebudgera Ck Rd GS Peak Design Discharge (m3/s) ARI Current Study GCCC 2001 GHD 2001 WBM 1995 (Year) DEA FFA TPT MC CRC-CH MC DEA FFA DEA DEA FFA 2 182 184 237 202 - - - - - 5 327 303 340 293 441 284 - 321 335 10 415 393 436 371 565 339 - 397 446 20 512 490 531 463 687 403 - 530 549 50 633 634 660 596 793 503 - 667 671 100 741 758 769 799 902 594 683 817 755 200 868 897 893 903 - - 769 - - The following is of note with regards to Figure 13 and Table 35: The agreement between DEA and FFA estimates of the current study is excellent. The agreements between DEA, TPT MC and CRC-CH MC estimates of the current study are very good. The agreement between the DEA and the FFA estimates in the current study is better when compared to the GCCC 2001 and WBM 1995 studies. The FFA in the current study is based on a longer (1970 - 2013) period of recorded data. The peak design discharges estimated in this study are generally lower than the discharges estimated by GCCC 2001 and WBM 1995 studies. The differences in design peak discharges are likely due to the following reasons: Areal Reduction Factors were not applied to the design rainfalls in the GCCC 2001 study. WBM 1995 used ARR 87 temporal patterns and GCCC 2001 used AWE 2000 temporal patterns. WBM filtered the ARR 87 temporal patterns to remove the sub-duration inconsistencies but the inconsistencies were not removed completely. On the other hand AWE 2000 temporal patterns had significant sub-duration inconsistencies and these were not filtered in GCCC 2001 study. In the current study a sensitivity analysis were undertaken and it was found that temporal patterns with sub-duration inconsistencies generated unrealistically long critical storm durations and higher design peak discharges in the Gold Coast region. In the current study the AWE 2000 temporal patterns were filtered and smoothened by adjusting the longer duration storm temporal patterns according to the methodology outlined in Australian Rainfall and Runoff (1998) and BoM (1991). The filtering and smoothing were undertaken until the sub-duration inconsistencies were completely removed for all ARI’s up to 100 years, whilst maintaining the basic shape and integrity of the patterns (WRM 2008c 12.12 ). The filtered temporal patterns generate realistic critical storm durations and lower design peak discharges than the ARR 87 and AWE 2000 Temporal patterns. Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 59 of 76 The previous studies did not attempt reconciliation between model estimates and the FFA results Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 60 of 76 10. Conclusion An URBS hydrological model for Tallebudgera Creek catchment has been developed, calibrated and verified successfully using the best available data and current industry standard modelling practices. The model was calibrated for January 2013, January 2008, June 2005 and February 2004 historical events and verified against April 1990 and February 1990 historical events. The calibrated model was then used to estimate the design flood discharges at different locations within Tallebudgera Creek catchment for 2, 5, 10, 20, 50, 100, 200, 500, 1000 and 2000 year ARI and PMP design flood events. The design discharges predicted by the model have been compared and reconciled with FFA estimated design discharges at Tallebudgera Creek Road gauging station. A FFA was undertaken for 43 years (1970 to 2013) of recorded data. Joint Probability Analysis for Total Probability Theorem Monte Carlo and Cooperative Research Centre – Catchment Hydrology Monte Carlo simulations were also undertaken to verify the results of current Design Event Approach. In conclusion, the current Design Event hydrological study for Tallebudgera Creek catchment is robust – it is supported by Flood Frequency Analysis and Monte Carlo simulations. The output of this study can be used as input to the hydraulic modelling for flood planning and flood studies of Tallebudgera Creek catchment. Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 61 of 76 11. Recommendation The following recommendations are made: The model calibration should be revisited and reviewed when a significant storm event occurs and the data are available. Tallebudgera Creek catchment URBS model design rainfall and temporal pattern be reviewed after the next release of Australian Rainfall and Runoff. Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 62 of 76 12. Reference 12.1 GCCC (2001) Tallebudgera and Currumbin Creeks Flood Risk Management Study - Interim Hydrology Report prepared by Don Carroll for Gold Coast City Council, February 2001 12.2 WBM (1995) Currumbin Creek and Tallebudgera Creek Flood Study Report prepared by WBM for Gold Coast City Council, August 1995 12.3 GHD (2007) Tallebudgera Creek Dam Upgrade – Detailed Design Report prepared by GHD for Gold Coast City Council, July 2007 12.4 GHD (2001) Tallebudgera Dam – Report on Risk Assessment Prepared by GHD for Gold Coast City Council, May 2001 12.5 GHD (2003) Tallebudgera Dam – Risk Assessment Addendum Report prepared by GHD for Gold Coast Water, July 2003 12.6 AWE (1998) Review of Gold Coast Rainfall Data Volume 1 Report prepared by Australian Water Engineering Pty Ltd for Gold Coast City Council, May 1998 12.7 AWE (2000) Review of Gold Coast Rainfall Data Volume 3 Temporal Patterns Report prepared by Australian Water Engineering Pty Ltd for Gold Coast City Council, October 2000 12.8 Pilgrim (2000) Peer Review Gold Coast Rainfall Temporal Patterns Report prepared by D H Pilgrim & Associates Pty Ltd for Gold Coast City Council, October 2000 12.9 UWS (2006) Design Temporal Patterns in the Gold Coast Region Report prepared by the University of Western Sydney for Gold Coast City Council, August 2006 12.10 WRM (2008a) Summary Findings of the Review of Hydrological Models for the Gold Coast City Catchments Report prepared by WRM Water & Environment Pty Ltd for Gold Coast City Council, March 2008 12.11 WRM (2008b) GCCC IFD Utility Modifications Report prepared by WRM Water & Environment Pty Ltd for Gold Coast City Council, July 2008 12.12 WRM (2008c) Revision of Design Rainfall Temporal Patterns for Gold Coast Catchments Report prepared by WRM Water & Environment Pty Ltd for Gold Coast City Council, October 2008 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 63 of 76 12.13 WRM (2008d) Design Event Hydrology Report prepared by WRM Water & Environment Pty Ltd for Gold Coast City Council, August 2008 12.14 BoM (2003) Guide to the Estimation of Probable Maximum Precipitation: Generalised Tropical Storm Method Report prepared by the Hydro Meteorological Advisory Service, Australian Government Bureau of Meteorology, November 2003 12.15 BoM (2003) The Estimation of Probable Maximum Precipitation in Australia: Generalised Short Duration Method Report prepared by the Hydro Meteorological Advisory Service, Australian Government Bureau of Meteorology, June 2003 12.16 Carroll (2012) URBS – A Rainfall Runoff Routing Model for Flood Forecasting and Design, Software v5.00 Manual developed by D G Carroll, December 2012 12.17 Hargraves (2004) Extreme Rainfall Estimation Project, CRC FORGE and ARF Techniques, Queensland and Border Locations Report prepared by Gary Hargraves, Water Assessment & Planning Resource Science Centre, Circa 2004 12.18 Carroll (2013) Review and Update of The City of Gold Coast’s Hydrological Models Report prepared by D G Carroll for The City of Gold Coast, April 2013 12.19 Kuczera (2006) Joint Probability and Design Storms at the Cross Roads Report prepared by George Kuczera for Australian Journal of Water Resources, Vol 10 No 1, 63-80 12.20 Rahman (2001) Monte Carlo Simulation of Flood Frequency Curves from Rainfall Technical report prepared for CRC-CH 12.21 Mirfenderesk (2013) Comparison between Design Event and Joint Probability Hydrological Modelling Report prepared by Hamid Mirfenderesk for FMA National Conference, May 2013 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 64 of 76 13. Appendix A: URBS Model Sub-catchment Areas and Land Uses Table 36 - Tallebudgera Sub-catchment Areas and Land Uses Sub Catchment Area UL UM UH UR UF ID (km2) (km2) (km2) (km2) (km2) (km2) 1 2.10 0.00 0.00 0.01 0.00 0.99 2 2.27 0.00 0.00 0.02 0.00 0.98 3 4.38 0.00 0.00 0.04 0.00 0.96 4 4.14 0.00 0.00 0.04 0.39 0.57 5 3.24 0.00 0.00 0.02 0.25 0.73 6 2.62 0.00 0.00 0.07 0.00 0.93 7 2.84 0.00 0.00 0.05 0.28 0.67 8 2.05 0.00 0.00 0.01 0.89 0.10 9 3.57 0.01 0.00 0.05 0.31 0.63 10 2.21 0.00 0.00 0.01 0.24 0.75 11 3.87 0.14 0.00 0.05 0.16 0.65 12 4.53 0.01 0.00 0.04 0.05 0.91 13 4.31 0.16 0.00 0.01 0.70 0.13 14 3.64 0.00 0.00 0.03 0.38 0.58 15 3.60 0.00 0.00 0.10 0.43 0.47 16 3.75 0.00 0.00 0.07 0.30 0.63 17 3.32 0.02 0.00 0.07 0.45 0.47 18 1.25 0.00 0.00 0.13 0.85 0.02 19 4.27 0.00 0.00 0.03 0.15 0.82 20 3.56 0.00 0.00 0.05 0.38 0.57 21 3.58 0.01 0.00 0.07 0.55 0.37 22 3.13 0.03 0.00 0.14 0.81 0.02 23 1.16 0.00 0.00 0.06 0.23 0.71 24 0.88 0.00 0.00 0.02 0.10 0.89 25 1.37 0.00 0.00 0.04 0.93 0.02 26 1.55 0.01 0.00 0.04 0.84 0.11 27 0.38 0.05 0.00 0.21 0.73 0.00 28 1.65 0.00 0.00 0.15 0.83 0.01 29 1.40 0.11 0.00 0.42 0.44 0.02 30 1.08 0.01 0.00 0.09 0.26 0.64 31 1.70 0.00 0.32 0.12 0.52 0.05 32 0.58 0.00 0.25 0.74 0.01 0.00 33 4.18 0.00 0.24 0.45 0.31 0.00 34 1.37 0.00 0.04 0.89 0.03 0.05 35 2.21 0.00 0.00 0.51 0.40 0.09 36 5.82 0.02 0.00 0.85 0.08 0.05 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 65 of 76 14. Appendix B: URBS Catchment Definition File TALLEBUDGERA CREEK URBS MODEL {Model built by and reviewed by (2009) and (2013)} MODEL: SPLIT USES: L, U, F*0.5 DEFAULT PARAMETERS: alpha=0.11 m=0.65 beta=1.6 n=1.0 CATCHMENT DATA FILE = Talle_00.csv RAIN #1 L = 1.56 STORE. RAIN #2 L = 1.13 GET. ROUTE THRU #3 L = 0.92 ADD RAIN #3 L = 1.02 ROUTE THRU #4 L = 1.37 ADD RAIN #4 L = 1.42 STORE. RAIN #5 L = 1.02 GET. ROUTE THRU #5 L = 1.73 STORE. RAIN #6 L = 1.24 ROUTE THRU #7 L = 1.69 STORE. RAIN #7 L = 1.25 GET. ROUTE THRU #7 L = 0.15 ROUTE THRU #8 L = 0.94 STORE. RAIN #8 L = 0.8 GET. ROUTE THRU #8 L = 0.48 GET. ROUTE THRU #9 L = 0.62 ADD RAIN #9 L = 1.04 STORE. RAIN #10 L = 1.48 GET. ROUTE THRU #11 L = 1.03 ADD RAIN #11 L = 0.84 PRINT. DAM_IN {X=535584.07, Y=6883073.67} DAM ROUTE VBF = 0 NUMBER = 18 {Volume Before Flow = 0 when the dam is full at start of the simulation} 0 0 29 8.2 103 42.8 188 95.1 273 162.2 386 243 517 336.7 649 441.2 673 462.5 798 562 958 703.6 1118 860.8 1257 1031.2 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 66 of 76 1382 1205.8 1507 1383.5 1632 1569.9 1757 1764.6 1882 1967.1 PRINT.TalleDam {X=535584.07, Y=6883073.67, Tallebudgera Creek Dam data book Volume 2 of 2 by GHD on May 2001 - pages 38 and 39 + Appendix D2: Spillway and Tailwater Rating Curves} ROUTE THRU #12 L = 0.98 STORE. RAIN #12 L = 0 PRINT. LH_SC12 {X=536370.43, Y=6883413.42} GET. ROUTE THRU #12 L = 0.79 STORE. RAIN #13 L = 1.17 ROUTE THRU #14 L = 1.03 ADD RAIN #14 L = 0 PRINT. TH_SC13-14 {X=537078.92, Y=6882618.42} ROUTE THRU #14 L = 1.44 GET. ROUTE THRU #15 L = 0.86 STORE. RAIN #15 L = 0 PRINT. LH_SC15 {X=537580.67, Y=6884383.44} GET. ROUTE THRU #15 L = 1.47 STORE. RAIN #16 L = 0 PRINT. LH_SC16 {X=539283.28, Y=6883451.43} ROUTE THRU #16 L = 2.49 GET. ROUTE THRU #17 L = 1.1 STORE. RAIN #17 L = 0 PRINT. LH_SC17 {X=539532.53, Y=6886170.24} GET. ROUTE THRU #17 L = 1.11 PRINT. TALLEBUD {X=539575.05, Y=6886781.66} Factor = 3.0 {******************} ROUTE THRU #18 L = 0.68 STORE. RAIN #18 L = 0 PRINT. LH_SC18 {X=539950.21, Y=6887095.92} GET. ROUTE THRU #18 L = 0.5 STORE. Factor = 1.0 {******************} RAIN #19 L = 1.62 ROUTE THRU #20 L = 1.16 STORE. RAIN #20 L = 0.39 GET. PRINT. TH_SC19-20 {X=539010.73, Y=6887234.51} ROUTE THRU #20 L = 1.51 GET. Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 67 of 76 Factor = 3.0 {******************} ROUTE THRU #21 L = 1.09 STORE. RAIN #21 L = 0 PRINT. LH_SC21 {X=540736.71, Y=6887487.13} GET. ROUTE THRU #21 L = 1.35 ROUTE THRU #22 L = 1.16 PRINT.COPLICKS {X=542126.46, Y=6887983.20, COPLICKS BRIDGE ALERT} STORE. RAIN #22 L = 0 PRINT.LH_SC22 {X=542126.46, Y=6887983.20} GET. ROUTE THRU #22 L = 1.58 STORE. Factor = 1.0 {******************} RAIN #23 L = 1.4 STORE. RAIN #24 L = 1.29 GET. ROUTE THRU #25 L = 0.7 STORE. RAIN #25 L = 0 GET. PRINT. TH_SC23-25 {X=540957.68, Y=6885608.07} ROUTE THRU #25 L = 1.22 STORE. RAIN #26 L = 0 PRINT. LH_SC26 {X=541795.62, Y=6884650.97} ROUTE THRU # 26 L = 1.73 GET. ROUTE THRU #27 L = 0.38 STORE. Factor = 3.0 {******************} RAIN #27 L = 0 PRINT. LH_SC27 {X=541911.63, Y=6886353.57} GET. ROUTE THRU #27 L = 0.69 STORE. RAIN #28 L = 0 PRINT. LH_SC28 {X=542296.82, Y=6885415.19} ROUTE THRU # 28 L = 1.27 GET. ROUTE THRU #29 L = 0.65 STORE. RAIN #29 L = 0 PRINT. LH_SC29 {X=542673.04, Y=6886936.48} GET. ROUTE THRU #29 L = 0.81 ROUTE THRU #32 L = 0.56 STORE. RAIN #32 L = 0 PRINT. LH_SC32 {X=543178.09, Y=6888003.31} GET. ROUTE THRU #32 L = 0.23 Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 68 of 76 STORE. Factor = 1.0 {******************} RAIN #30 L = 0.97 ROUTE THRU #31 L = 0.73 ADD RAIN #31 L = 0 PRINT. TH_SC30-31 {X=543621.09, Y=6887024.43} Factor = 3.0 {******************} ROUTE THRU #31 L = 0.65 ROUTE THRU #32 L = 0.48 GET. ROUTE THRU #32 L = 0.58 GET. ROUTE THRU #33 L = 1.02 STORE. RAIN #33 L = 0 PRINT. LH_SC33 {X=543622.92, Y=6888999.42} GET. ROUTE THRU #33 L = 4.29 STORE. Factor = 1.0 {******************} RAIN #34 L = 0 PRINT. LH_SC34 {X=541018.97, Y=6888824.69} ROUTE THRU #34 L = 1.13 Factor = 6.0 {******************} ROUTE THRU #35 L = 0.94 STORE. RAIN #35 L = 0 PRINT.LH_SC35 {X=543230.22, Y=6890543.63} GET. ROUTE THRU #35 L = 2.01 PRINT.OYSTER TH {X=543230.22, Y=6890543.63 OYSTER CREEK ALERT} GET. ROUTE THRU #36 L = 1.34 STORE. RAIN #36 L = 0 PRINT. LH_SC36 {X=544226.20, Y=6891322.12} GET. ROUTE THRU #36 L = 1.25 PRINT. TH_OUT {X=545156.52, Y=6892077.23} END OF CATCHMENT DATA Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 69 of 76 15. Appendix C: Calibration and Verification Plot Figure 14 - January 2013 Calibration @ Tallebudgera Ck Dam Gauging Station Figure 15 - January 2013 Calibration @ Tallebudgera Ck Rd Gauging Station Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 70 of 76 Figure 16 - January 2013 Calibration @ Coplicks Bridge Gauging Station Figure 17 - January 2008 Calibration @ Tallebudgera Creek Dam Gauging Station Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 71 of 76 Figure 18 - January 2008 Calibration @ Tallebudgera Creek Road Gauging Station Figure 19 - June 2005 Calibration @ Tallebudgera Creek Dam Gauging Station Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 72 of 76 Figure 20 - June 2005 Calibration @ Tallebudgera Ck Rd Gauging Station Figure 21 - June 2005 Calibration @ Coplicks Bridge Gauging Station Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 73 of 76 Figure 22 - February 2004 Calibration @ Tallebudgera Ck Road Gauging Station Figure 23 - April 1990 Verification @ Tallebudgera Creek Road Gauging Station Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 74 of 76 Figure 24 - February 1990 Verification @ Tallebudgera Creek Road Gauging Station Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 75 of 76 Council of the City of Gold Coast PO Box 5042 GCMC Qld 9729 P 1300 GOLDCOAST E [email protected] W cityofgoldcoast.com.au Tallebudgera Creek Catchment – Hydrological Study, July 2014 TRACKS-#45381530-v1 Page 76 of 76