Coomera River Catchment
Hydrological Study
August 2014
1
Title: Coomera River Catchment Hydrological Study
Author:
Study for: City Planning Branch
Planning and Environment Directorate
File Reference: WF19/44/(P1)
TRACKS #45484061-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 Coomera River 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 hydrological models to a consistent standard. 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 recommendations and includes Monte Carlo methodologies for comparative analysis.
The main objective of this study is to develop a hydrological model for the Coomera River 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, 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 Coomera River catchment was developed using the current land uses, topographic data sets and best available industry standard modelling approaches. The hydrological study undertaken by NH team has been reviewed by WRM, Council’s Peer Review Group (PRG) and Don Carroll Project Management.
Calibration and verification data for 30 historical flood events between 1954 and 2013 were sourced for this study from the Bureau of Meteorology (BoM). From the available data, five events (January 2013, February 2010, January 2008, June 2005 and March 2004) were selected for calibration and another three events (February 1990, January 1974 and June 1967) were selected for verification.
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 rates were calibrated for each event. Table below shows the set of model parameters adopted for all calibration, verification and design event simulations:
Parameter Adopted Value α (Channel lag) 0.12 (Catchment lag) 1.2 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 Canungra Army TM, Clagiraba Road ALERT and Oxenford Weir ALERTs 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 for all calibration events.
Peak Discharge (m3/s)
Event Canungra Army TM Clagiraba Rd AL Oxenford Weir AL
Modelled Recorded Modelled Recorded Modelled Recorded Jan 2013 541 527 1047 * 1779 1819 Feb 2010 568 446 1179 * 2237 2203 Jan 2008 801 733 1222 * 1352 * Jun 2005 150 * 269 255 850 790 Mar 2004 383 368 620 571 755 798 * Station appears to have malfunctioned during the event
The calibrated URBS model was then used to estimate the design flood discharges throughout the Coomera River catchment using the Design Event Approach (DEA). The design rainfall data including Intensity Frequency Duration (IFD), Temporal Patterns (TP), Areal Reduction Factor (ARF), rainfall spatial distribution and design rainfall losses adopted in this study were recommended by WRM, Council’s Peer Review Group (PRG) and Don Carroll Project Management.
A Flood Frequency Analysis (FFA) was undertaken using annual peak discharges at Canungra Army TM for 51 years (1962–2013) 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 Coomera River catchment has been estimated using the DEA, FFA, TPT MC and CRC–CH MC methodologies. The peak design discharges for different ARIs at Canungra Army TM estimated by these methods are shown in the table below:
ARI Design Peak Discharge @ Canungra Army TM (m3/s) (Year) DEA FFA TPT MC CRC-CH MC 2 121 113 254 220 5 280 273 370 318 10 396 393 467 404 20 539 528 562 515 50 726 734 694 678 100 883 915 806 868
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The comparison table shows very good agreements between the DEA and FFA estimates and good agreements among DEA, TPT MC and CRC-CH MC estimates for ARIs 10 years and above. Consequently the design hydrographs estimated in this study using the Design Event Approach is considered robust and it will provide the most appropriate input to the hydraulic models to be used for flood planning and flood management studies in the Coomera River catchment.
The Tables below show the final peak design discharges at different locations within Coomera River catchment for the 2 year ARI to PMPDF 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 Canungra Army TM. However the design discharges estimated in the table below are based on adopted ARF for the total catchment area1.
Design Peak Discharge (m3/s) ARI Canungra Oxenford Pacific Hwy Catchment (Year) Clagiraba AL Army TM Weir AL Coomera Outlet 2 113 207 391 406 551 5 264 490 840 865 1118 10 374 706 1152 1186 1507 20 513 960 1488 1536 1944 50 694 1287 1988 2049 2548 100 844 1550 2333 2395 2932 200 896 1667 2544 2615 3239 500 1021 1903 2926 3007 3729 1000 1111 2054 3065 3143 3997 2000 1218 2254 3362 3443 4379 PMPDF 2839 5301 7997 8263 10599
Design Peak Discharge (m3/s) ARI Beechmont Pacific Hwy Pacific Hwy GC Hwy (Year) TM Saltwater Ck Coombabah Ck Coombabah Ck 2 18 72 27 66 5 35 142 62 134 10 49 191 83 174 20 65 242 108 221 50 86 327 149 311 100 104 367 167 346 200 120 407 191 397 500 135 457 217 449 1000 166 685 338 666 2000 182 753 371 730 PMPDF 354 1153 584 1107
1 Adoption of an ARF for the total catchment is appropriate for deriving inflows for a hydraulic model of the lower Coomera 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 Kinhill Cameron McNamara (1979) ...... 10 1.3.2 WBM Oceanics (1988) ...... 10 1.3.3 Kinhill Cameron McNamara (May 1992) ...... 10 1.3.4 Kinhill Cameron McNamara (January 1993) ...... 11 1.3.5 Kinhill Pty Ltd (Jun 1998) ...... 11 1.3.6 Bureau of Meteorology (July 1998) ...... 11 1.3.7 Gutteridge Haskins & Davey (February 2000) ...... 11 1.3.8 Gold Coast City Council (April 2001) ...... 11 1.4 Limitation Statement ...... 12 1.5 Acknowledgement ...... 12 2. Catchment Description ...... 13 2.1 General ...... 13 2.2 Drainage Characteristics ...... 15 2.3 Land Use ...... 18 3. Methodology ...... 19 4. Available Data ...... 21 4.1 Topographic Data ...... 21 4.2 Land Use Data ...... 21 4.3 Rainfall Data ...... 21 4.4 River Height Data ...... 28 4.5 Rating Tables ...... 28 4.5.1 Canungra Army TM ...... 29 4.5.2 Clagiraba Road ALERT ...... 31 4.5.3 Oxenford Weir ALERT ...... 32 5. Model Development ...... 33 5.1 Model Description ...... 33 5.2 Model Configuration ...... 34 5.2.1 Land Use ...... 34 5.2.2 Sub-catchments...... Error! Bookmark not defined. 6. Model Calibration and Verification ...... 39 6.1 Selection of Calibration and Verification Events ...... 39 6.2 Calibration Methodology ...... 39 6.3 Assignment of Rainfalls and Temporal Patterns ...... 40
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6.4 Adopted Model Parameters ...... 40 6.5 Initial and Continuing Losses ...... 40 6.6 Calibration Results ...... 41 6.6.1 General Comments ...... 41 6.6.2 January 2013 ...... 41 6.6.3 February 2010 ...... 42 6.6.4 January 2008 ...... 42 6.6.5 June 2005 ...... 42 6.6.6 March 2004...... 42 6.7 Verification Results ...... 43 6.7.1 February 1990 ...... 43 6.7.2 January 1974 ...... 43 6.7.3 June 1967 ...... 43 7. Flood Frequency Analysis ...... 44 7.1 Method of Analysis ...... 44 7.2 Available data ...... 44 7.3 Annual Peak Discharge Analysis ...... 44 8. Design Flood Estimation ...... 46 8.1 Methodology ...... 46 8.2 Frequent to Large Design Events (up to and including 100 Year ARI) ...... 49 8.2.1 Rainfall Depth Estimation ...... 49 8.2.2 Aerial Reduction Factors ...... 51 8.2.3 Temporal Patterns ...... 51 8.2.4 Spatial Distribution ...... 55 8.2.5 Rainfall Losses ...... 55 8.2.6 Design Discharge ...... 55 8.3 Rare Design Events (200 to 2000 Year ARI) ...... 57 8.3.1 Rainfall Depth Estimation ...... 57 8.3.2 Aerial Reduction Factors ...... 57 8.3.3 Temporal Patterns ...... 57 8.3.4 Spatial Distribution ...... 60 8.3.5 Losses ...... 60 8.3.6 Design Discharges ...... 60 8.4 Extreme Design Events - Probable Maximum Precipitation Design Flood (PMPDF) ...... 62 8.4.1 Rainfall Depth Estimation ...... 62 8.4.2 Aerial Reduction Factors ...... 62 8.4.3 Temporal Patterns ...... 62 8.4.4 Spatial Distribution ...... 62 8.4.5 Losses ...... 62 8.4.6 Design Discharges ...... 62 8.5 Joint Probability Approach ...... 64
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8.5.1 TPT ...... 64 8.5.2 CRC-CH ...... 66 9. Comparison ...... 68 10. Conclusion ...... 72 11. Recommendation ...... 73 12. Reference ...... 74 13. Appendix A: URBS Model Sub-catchment Areas and Land Uses ...... 76 14. Appendix B: URBS Catchment Definition File ...... 78 15. Appendix C: Calibration and Verification Plot ...... 83
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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 discharge estimation and documentation vary significantly.
To provide a consistent basis for floodplain management and local government planning, the Council commissioned WRM Water & Environment (WRM) in December 2007 to undertake a major study to review and update its hydrological models to a consistent standard of methodology and documentation. Coomera, Nerang, Logan-Albert, Pimpama, Worongary, Mudgeeraba, Loder, Biggera, Tallebudgera and Currumbin catchment’s hydrological models are included in this study.
A comprehensive review of data, previous hydrological models and associated reports for the above 10 catchments covering the City were 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 Coomera River catchment using the URBS modelling software in August 2009. The model was calibrated against three historical events (January 2008, June 2005 and March 2004) and verified against three historical events (February 1990, January 1974 and June 1967). A Flood Frequency Analysis (FFA) was undertaken at Canungra Army TM Station using 46 years (1962 – 2008) of recorded data. The calibrated model was then used to estimate the design discharges from the 2 year Average Recurrence Interval (ARI) to Probable Maximum Precipitation Design Flood (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 is again reviewed by Don Carroll in 2013/14. At the time of this review the following modelling tasks were undertaken as per Don Carroll Project Management recommendations:
The January 2013 event should be included in the calibration dataset. Review the fraction of sub-catchment forested factor F. Adjustment be made to design rainfalls in the upper Coomera catchment. Redo the FFA for 51 years (additional 5 years) of recorded data at Canungra Army TM. Extend the modelling to include Monte Carlo methodologies to address the Queensland Floods Commission of Inquiry Recommendation.
This report describes the development of URBS hydrological model, calibration, FFA, Monte Carlo simulation and design events simulation for the Coomera River catchment.
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1.2 Study Objective and Scope
The main objective of this study is to develop a hydrological model for Coomera River catchment using the URBS model as the preferred city wide 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 then to be used to estimate the design flood discharges using a consistent methodology. The scope of work for the Coomera River catchment is as follows:
Review the existing models and data, Update the existing model to a standard consistent with other updated models, Review and update model calibration and verification, Undertake an FFA at Canungra Army TM, Undertake Monte Carlo simulations, Estimate the design peak discharges and extreme event discharges at key locations throughout the catchment using current industry standard methodologies and 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 Coomera River catchment. Brief descriptions of the most relevant of these studies are presented below:
1.3.1 Kinhill Cameron McNamara (1979) Kinhill Cameron McNamara built a RORB runoff-routing model for the Coomera River catchment in 1979. The model was calibrated against the 1974 and 1976 recorded flood data at Canungra Army TM. The calibrated model was then used to derive the design flood hydrographs at various locations within the catchment using design rainfall depths provided by the Bureau of Meteorology.
1.3.2 WBM Oceanics (1988) WBM used the RORB runoff-routing model to derive flood hydrographs along the Coomera River and the Cordery and Webb unit hydrograph method to drive flood hydrographs along the tributaries. In this study, the RORB model was calibrated against January 1974 flood data. Design flood hydrographs were derived using the calibrated model.
1.3.3 Kinhill Cameron McNamara (May 1992) There were significant differences between the design flood hydrographs previously derived for the Coomera River catchment by Kinhill Cameron McNamara (1979) and WBM Oceanics (1988). Kinhill Cameron McNamara was commissioned by the Albert Shire Council in 1992 to update their previous work and resolve the differences in results between Kinhill and WBM studies.
In this study, the RORB model was calibrated using stream gauge data recorded at Canungra Army TM for the June 1967, January 1974 and February 1976 flood events.
The peak design discharge estimated by this study for Coomera River catchment was lower than Kinhill and WBM studies. On the other hand the peak design discharges for Coombabah Creek, Oaky Creek and Saltwater Creek estimated by this study were higher than Kinhill and WBM studies.
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1.3.4 Kinhill Cameron McNamara (January 1993) Kinhill Cameron McNamara were again commissioned by the Albert Shire Council to review why the design flood discharges that were estimated previously appeared to be low when compared with the recorded data for the 1974 flood. Kinhill reviewed the design rainfall, temporal patterns, recorded data, and the adopted methodology but did not find any apparent reasons to revise their previous results.
1.3.5 Kinhill Cameron McNamara (November 1995) Coomera River Flood Studies – Final Report in two volumes brings together the hydrology and hydraulic studies undertaken by Kinhill Cameron McNamara on behalf of Albert Shire Council and the Gold Coast City Council during 1992 to 1995.
1.3.6 Kinhill Pty Ltd (Jun 1998) Kinhill Pty Ltd are commissioned by Witheriff Nyst Lawyers on behalf of Gold Coast City Council to undertake a detailed review of the Coomera River catchment hydrology, especially for large flood events, taking into account the recent findings of a study by Australian Water Engineering Pty Ltd (AWE) to update design rainfall data for the Gold Coast city area. Kinhill used their previously calibrated RORB model for this study. Council’s current flood planning levels in the Planning Scheme is based on this hydrological study.
1.3.7 Bureau of Meteorology (July 1998) GHD (2000) refers to a Coomera River Flood Forecasting URBS model development undertaken by the Bureau of Meteorology (BoM) in July 1998. However, the BoM report is not available for review in this study.
1.3.8 Gutteridge Haskins & Davey (February 2000) Gutteridge Haskins & Davey (GHD) was commissioned by GCCC to undertake a hydrological study of the Coomera River catchment for Council’s flood planning purposes. GHD built a URBS model using available data and calibrated the model against 13 historical flood events that occurred between June 1967 and May 1996. GHD used two quite different rating curves at Canungra Army TM for their model calibration. Department of Natural Resources & Mines (DNRM) rating Table 9 was used for calibration events that occurred between June 1967 and February 1976 event, and a modified DNRM rating Table 12 was used for calibration events that occurred after February 1976. Separate sets of calibration parameters (α, and m as well as initial and continuing losses) were derived for each of the 13 calibration events, and then a single set of weighted average parameter values were recommended and used for design discharge estimation. It is noted that the design discharges estimated by GHD in this study were significantly lower than the equivalent estimates made in the Kinhill (1998) study.
1.3.9 Gold Coast City Council (April 2001) GCCC undertook an internal review of the Kinhill (1998) and GHD (2000) studies to address the uncertainties regarding the rating table at Canungra Army TM, the reasons for the significant differences between GHD and Kinhill model results and the poor agreement between hydrologic model and flood frequency analysis results in the GHD report.
After this review, GHD’s URBS model was updated using a single rating curve at Canungra Army TM for all calibration events. DNRM rating Table 12 as modified by BoM was adopted for the updated model. Better agreement was achieved between flood frequency analysis and the updated model results. The design discharges estimated by the updated URBS model were considerably lower than the equivalent estimates from the Kinhill’s RORB model. The review recommended that the updated URBS model be used for Council’s future flood planning purposes. However, this recommendation is yet to be adopted by GCCC. The Council still uses Kinhill’s RORB model design discharges for flood planning and hydraulic impact assessment purposes.
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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 City of Gold Coast. The result of this study is accurate only for its intended purposes.
1.5 Acknowledgement
The assistance provided by the Bureau of Meteorology, and Mr Jeff Perkins 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 for model calibration and verification.
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2. Catchment Description
2.1 General
Coomera River catchment is one of the largest catchment in the Gold Coast. It has an area of about 441 km2. The major tributaries of Coomera River are Back Creek, Clagiraba Creek, Guanaba Creek, Wongawallan Creek, Howard Creek, Running Creek, Tamborine Creek, Yaun Creek, Oakey Creek, Saltwater Creek, Coombabah Creek and Brygon Creek.
The Coomera River rises in the McPherson Ranges and flows north from the Queensland-New South Wales border through the Department of Defence’s Canungra Land Warfare Training Area, Upper Coomera, Oxenford, Coomera, Santa Barbara, Sanctuary Cove and then east to the Broadwater via Hope Island. Before entering the Broadwater, the Coomera River splits into two branches. The two branches are known as North Arm and South Arm which form the Southern Moreton Bay Islands.
There are two major hydraulic structures along the Coomera River. One is the Pacific Highway Bridge which is located about 12.5 km upstream of Broadwater and the other is the Oxenford Weir which is located about 4.5 km upstream of Pacific Highway. The tidal influence extends up to the downstream side of Oxenford Weir. Figure 1 shows the Coomera River and its major tributaries.
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Figure 1 - Coomera River and its Tributaries
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2.2 Drainage Characteristics
The Coomera River is about 84.3 km long. It is quite steep along its upstream reaches. The slope gradually reduces through the middle to lower reaches and becomes flat at the Broadwater. The catchment elevations range from approximately 1,145.0 mAHD in the McPherson Ranges to less than 2.0 mAHD at the Paradise Point near the Broadwater and the channel bed elevation varies approximately from 510.0 mAHD to -6.0 mAHD. The average channel slope from the upstream extent of the River to the Broadwater is approximately 0.38%. Figure 2 shows the longitudinal profile of the main River.
Figure 2 - Coomera River, Longitudinal Profile
Back Creek is one of the major upstream tributaries of the Coomera River. It rises in Beaudesert near Mackenzie Road and joins the Coomera River at the downstream side of JMcD Sharp Bridge on the Nerang Beaudesert Road. Back Creek is about 23.0 km long and has a catchment area of 52.6 km2. The average channel slope from the upstream extent of the creek to the confluence of Coomera River is approximately 1.53%. Figure 3 shows the longitudinal profile of Back Creek.
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Figure 3 – Back Creek, Longitudinal Profile
There are two other major tributaries in the lower catchment of the Coomera River, namely Saltwater Creek and Coombabah Creek. Saltwater Creek, which has a catchment area of 30.4 km2, flows through Nerang Forest Reserve, Pacific Pines, Maudsland, Oxenford, Helensvale, Hope Island and finally meets the Coombabah Creek at Paradise Point. The length of this creek is about 17.0 km and the average channel slope from the upstream extent of the creek to the confluence of Coombabah Creek is approximately 0.09%. Figure 4 shows the longitudinal profile of Saltwater Creek.
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Figure 4 – Saltwater Creek, Longitudinal Profile
Coombabah Creek has a catchment area of 51.1 km2, flows through Nerang Forest Reserve, Pacific Pines and Coombabah Conservation Park. It meets the Coomera River at the confluence of Hope Island Canal and Coomera River. The Coombabah Creek is about 20.0 km long. The average channel slope from the upstream extent of the Creek to the confluence of Coomera River is approximately 0.09%. Figure 5 shows the longitudinal profile of Coombabah Creek.
Figure 5 – Coombabah Creek, Longitudinal Profile
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2.3 Land Use
Approximately the three quarters of the Coomera River catchment is rural, mostly forested and rural residential developments. The rest of the catchment is urban, comprising residential, high density residential, commercial and industrial. Land use data are discussed further in Sections 4.2 and 5.2.1 .
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3. Methodology
The hydrologic modelling of the Coomera River catchment is 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 (GHD, 2000) and RORB (Kinhill, 1998) models, Review catchment and sub-catchments boundaries using the latest DTM and drainage network data, Review the Sub-catchment IFD’s upstream of Canungra, Review and update the Rating Tables at Canungra Army TM, Oxenford Weir AL and Clagiraba Road AL, Review available rainfall and stream gauging data, Review the existing land use data and update the model based on Council’s land use plan and latest Air photo.
Model construction - the specific tasks included: Update the URBS model configuration, Review and update the sub-catchment delineation using Council’s Master DTM (November 2007), DNRM DEM, DNRM Drainage Layer, Council’s Waterways Layer (2006), Council’s Open Drain Layer (August 2007) and Council’s Pipe Culvert Layer (August 2007); Generate a catchment network file with appropriate output locations and calibration points, Update the model to reflect the 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 Canungra Army TM, 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) and 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,
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Undertake the Flood Frequency Analyses (FFA) at Canungra Army TM, 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 and 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) 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 and a digital elevation model were 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 are 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 mainly collected from the BoM. BoM has sourced this data from a variety of rainfall stations and data types including pluvio and daily stations for the period 1954 to 2013. The rainfall data used in the previous Kinhill (1979, 1992, 1993 and 1998), WBM (1988) and GHD (2000) studies were not available at the time of this study. Table 1 to Table 4 and Figure 6 to Figure 7 show the rainfall and river height stations, those are currently in operation in and around Coomera River catchment.
The following is of note with regard to the rainfall stations:
The rainfall station coverage within the Coomera River catchment is very good. Stations indicated by TM or ALs are automatic stations. TM stations are connected to the public telephone network and polled regularly by computer during periods of rain. AL 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 1 – Currently available Rainfall and River Height Stations Operating CBM No AWRC No Station Name Rain/River Agency 540400 - Upper Springbrook AL RN Council 40607 - Springbrook RN BoM 540581 - Springbrook TM RN DNRM 40848 - Lower Springbrook AL RN BoM/Council 540054 146907 Little Nerang Dam AL RN/RV Seqwater 540612 - Little Nerang Dam HW TM RN/RV Seqwater 540287 - Tallai AL Repeater RN Council 40882 - Nubinbah AL RN BoM/Council 540438 146926 Nubinbah Valley AL RN/RV Council 540437 146015 Nubinbah Valley TM RN/RV DNRM 40584 146904 Hinze Dam RV BoM/Seqwater 540374 146921 Hinze Dam AL-B RV Seqwater 540610 146033 Hinze Dam HW TM RN/RV Seqwater 40160 - Nerang RN BoM 40846 146905 Clearview AL RN/RV Council 40416 146002 Clearview TM RN/RV DNRM 540319 146914 Carrara AL RN/RV Council 540428 - Molendinar AL RN Council 540353 - Mt Nimmel AL RN Council 540453 146928 Bonogin Ck AL RV Council 540352 - Bonogin AL RN Council 540597 146929 Worongary Ck AL RN/RV Council 540440 146927 Neranwood AL RN/RV Council 540399 146020 Mudgeeraba Ck TM RV DNRM 540254 146912 Mudgeeraba AL RN/RV Council 540253 146801 Boobegan Ck Lock AL RN/RV Council 540318 146913 Evandale AL RN/RV Council 40684 146903 Evandale RV BoM 540360 146917 Biggera Ck Dam AL RN/RV Council 540359 146918 Loder Ck Dam AL RN/RV Council 540238 146802 Loder Creek AL RN/RV Council 40190 - Southport RN BoM 40881 146911 Air Sea Rescue AL RN/RV Council 40764 - Gold Coast Seaway RN BoM 540001 146800 Gold Coast Tide TM RV MSQ 40981 146924 Burleigh Waters AL RN/RV Council 540564 146811 Lake Orr AL RV Council 540565 146812 Lake Orr Weir TW AL RV Council 40417 - Miami RN BoM 540497 - Upper Tallebudgera AL RN Council 540366 146919 Tallebudgera Ck Dam AL RN/RV Council 540356 146908 Tallebudgera Ck Rd AL RN/RV Council RN – Rainfall Station, RV – River Height Station, Council – Council of the City of Gold Coast, AL – ALERT, TM – Telemetry, MSQ – Marine Safety Queensland, DNRM – Department of Natural Resources and Mines
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Table 2 – Currently available Rainfall and River Height Stations (Continued) Operating CBM No AWRC No Station Name Rain/River Agency 540355 146095 Tallebudgera Ck Rd TM RV DNRM 540320 146915 Coplicks Bridge AL RN/RV Council 540252 146803 Oyster Ck AL RN/RV Council 540577 146814 Tallebudgera Ck Mouth AL RN/RV Council 540640 146814 Currumbin Ck AL RN/RV Council 540354 - Tomewin AL RN Council 40899 - Tomewin - Tallowood RN BoM 540070 146920 Nicolls Bridge AL RV Council 540368 146012 Nicolls Bridge TM RV DNRM 40717 - Coollangatta RN BoM 58158 - Murwillumbah RN BoM 40845 - Binna Burra AL RN BoM/Council 540584 - Illinbah TM RN DNRM 40376 - Tyungun AL RN BoM 540290 146805 Canungra Army AL RN/RV Council 540228 146010 Canungra Army TM RV DNRM 40844 - Beechmont AL RN BoM/Council 540230 146014 Beechmont TM RN/RV DNRM 40197 - Mt Tamborine RN BoM 40335 - Mt Tamborine AL RN BoM 540291 146808 Clagiraba Road AL RN/RV Council 40341 - Wongawallan AL RN BoM 40166 - Oxenford RN BoM 540292 146807 Oxwnford Weir AL RN/RV Council 40516 - Coomera RN BoM 540269 146804 Monterey Keys AL RN/RV Council 540293 146810 Coomera Shores AL RN/RV Council 40345 - Luscombe AL RN BoM 540376 146922 Hotham Creek AL RN/RV Council 540377 146923 Stewarts Road AL RN/RV Council 540408 146925 Norwell AL RN/RV Council 540294 146809 Kerkin Road AL RN/RV Council 540295 146806 Steiglitz Wharf AL RN/RV Council 40932 - Darlington AL RN BoM 40931 - O'Reillys AL RN SRRC 40413 - Central Kerry RN BoM 40936 145915 Lumeah AL RN/RV SRRC 540303 145101 Lumeah TM RV DNRM 540480 145930 Nindooinbah Dam AL RN/RV Seqwater 540614 145108 Nindooinbah Dam HW TM RN/RV Seqwater 540375 145103 Cainbable Creek TM RV DNRM 540559 - Nindooinbah TM RN DNRM 40937 145916 Benobble AL RN/RV SRRC SRRC – Scenic Rim Regional Council
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Table 3 – Currently available Rainfall and River Height Stations (Continued) Operating CBM No AWRC No Station Name Rain/River Agency 540073 145107 Benobble TM RV DNRM 40930 - Laheys Lookout AL RN SRRC 40544 145907 Bromfleet RN/RV BoM/DNRM 40938 145917 Bromfleet AL RN/RV LCC 40738 145102 Bromfleet TM RN/RV DNRM 40761 145913 Wolffdene AL RN/RV LCC 540598 145006 Bahrs Scrub AL RN/RV LCC 40723 145905 Beenleigh RV BoM 540644 145807 Beenleigh AL RN/RV LCC 40042 - Cannungra RN BoM 40832 145003 Forest Home TM RN/RV DNRM 540580 - Upper Burnett Ck TM RN DNRM 540407 145018 Maroon Dam TM RV DNRM 540475 145806 Maroon Dam AL RN/RV Seqwater 40677 145100 Maroon Dam RN/RV Seqwater 540229 145021 Maroon Dam HW TM RN/RV Seqwater 540591 145099 Maroon Dam TW TM RV Seqwater 40942 - Palen Creek AL RN SRRC 540578 - Mt Barney TM RN DNRM 540436 145027 Ward Road TM RN/RV DNRM 40946 145923 Rathdowney AL RN/RV SRRC 40754 145020 Rathdowney TM RN/RV DNRM 540579 - Upper Running Ck TM RN DNRM 40943 145920 Dieckmans Bridge AL RN/RV SRRC 540074 145010 Dieckmans Bridge TM RN/RV DNRM 40539 145900 Dulbolla RV BoM 40933 - Foxley AL RN BoM 40944 145921 Rudds Lane AL RN/RV BoM 540402 145026 Tramway Lane TM RN/RV DNRM 540555 - Tamrookum TM RN DNRM 40948 - Knapps Peak AL RN BoM 40865 - Cannon Cove TM RN BoM 40941 - Kooralbyn AL RN SRRC 40945 145922 Round Mountain AL RN/RV SRRC 40714 145008 Round Mountain TM RN/RV DNRM 540270 145024 Bromelton Weir HW TM RN/RV Seqwater 540271 145025 Bromelton Weir TW TM RV Seqwater 40983 - Beaudesert Drumley ST RN BoM 40939 145918 Beaudesert AL RN/RV SRRC 540607 145034 Bromelton Dam HW TM RN/RV Seqwater 540481 145929 Bromelton Dam AL RN/RV Seqwater 540541 - Walker Road TM RN DNRM 540538 - Undullah Road TM RN DNRM LCC – Logan City Council
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Table 4 – Currently available Rainfall and River Height Stations (Continued) Operating CBM No AWRC No Station Name Rain/River Agency 40876 - Wilsons Peak AL RN BoM 540207 - Wilsons Peak AL-P RN Seqwater 540582 - Bryn Euryn TM RN DNRM 40947 145924 Croftby AL RN/RV SRRC 40841 145011 Croftby TM RN/RV DNRM 40729 145908 Boonah RV BoM 40949 145925 Boonah AL RN/RV SRRC 540510 145932 Coulson AL RN/RV SRRC 540509 145031 Coulson TM RN/RV DNRM 540615 145033 Wyarallong Dam HW TM RN/RV Seqwater 540512 145933 Wyarallong Dam AL RN/RV Seqwater 540530 145934 Wyarallong Dam RV BoM 40934 - Romani AL RN LCC 540590 145030 Cedar Grove Weir HW TM RN/RV Seqwater 40940 145919 Yarrahappini AL RN/RV LCC 40762 145014 Yarrahappini TM RN/RV DNRM 540214 145023 South MaClean TM RV Seqwater 540515 145935 South MaClean TW TM RV Seqwater 40542 145901 MaClean Bridge RN/RV BoM 40935 145914 MaClean Bridge AL RN/RV LCC 540596 - Logan Village AL RN/RV LCC 40665 145903 Waterford RV BoM 40878 145912 Waterford AL RN/RV LCC 540234 - Stretton(Gowan Rd) AL RN LCC 540674 145809 Bayes Road AL RV LCC 540675 145808 Schmidts Road AL RN/RV LCC 540233 - Underwood (Millers Rd) AL RN LCC 540079 145801 Slacks Ck (Reserve Pk) AL RN/RV LCC 540235 - Hillcrest (Wine Glass) AL RN LCC 40964 - Regents Park RN AQUAGEN 40854 - Logan City RN BoM 540078 145800 Marsden (First Ave) AL RN/RV LCC 540237 - Bega Road Quarry AL RN LCC 540091 145802 Slacks Ck (Loganlea Rd) AL RN/RV LCC 540255 - Carbrook AL RN LCC 540645 145806 Parklands AL RN/RV LCC 40709 145904 Eagleby RV BoM 540236 145803 Carbrook (Riedel Road) AL RN/RV LCC 540380 - Mt Cotton West AL RN Seqwater 540381 - Priestdale AL RN Seqwater 540382 - Rochedale South AL RN Seqwater 540384 145927 Leslie Harrison Dam AL RN/RV Seqwater 540611 145035 Leslie Harrison Dam HW TM RN/RV Seqwater
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Figure 6 – Location of Rainfall and River Height Stations (Source BoM)
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Figure 7 – Location of Rainfall and River Height Stations (Source BoM)
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4.4 River Height Data
Currently six River Height stations are in operation within the Coomera River catchment. Table 5 shows the station details and Figure 6 shows the locations. The following is of note with regard to the river height stations:
Only Canungra Army TM has good historical record (1962 to date) Clagiraba Road AL, Oxenford Weir AL, Monterey Keys AL and Coomera Shores AL have recorded data for last 10+ years. Canungra Army TM and Beechmont TM have rating table based on gauged discharges. Beechmont TM, Canungra Army TM, Clagiraba Road AL and Oxenford Weir ALs are non-tidal. Monterey Keys and Coomera Shores ALs are tidal.
Table 5 – River Height Stations within Coomera River Catchment
Max Catch Rating Gauged Station ment Period of Operation Table Height No. Station Name Area From To Source (m) (km2) 146014A Beechmont TM 7.00 05/06/1971 Now DNRM 0.474 146010A Canungra Army TM 97.35 01/10/1962 Now DNRM 4.936 146808 Clagiraba Rd AL 173.00 01/08/2000 Now BoM - 146807 Oxenford Weir AL 298.00 01/08/2000 Now MIKE 11 - 146804 Monterey Keys AL 24.23 29/05/2000 Now - - 146810 Coomera Shores AL 432.00 29/05/2002 Now Dependent - 146800 Gold Coast Tide TM -
4.5 Rating Tables
The following sub-sections discuss the rating tables adopted for Canungra Army TM, Clagiraba Road AL and Oxenford Weir AL stations. The following is of note with regards to the rating tables for the other gauging stations in the Coomera River catchment:
The Beechmont station is located at Beechmont on Back Creek, which is a tributary of Coomera River. This station commands a catchment area of only 7.0 km2 and has less than 5 model sub-catchments in the upstream. Therefore, this station is not selected for model calibration. The water levels at Coomera Shores and Monterey Keys stations are influenced by the tide and do not have reliable rating tables. Therefore, these stations are selected only to calibrate the travel times predicted by the model. A rating table for the Coast Tide station was not available. The recorded height data from the Coast Tide station is assumed to represent the height at the mouth of Coomera River and used to select the appropriate dependent rating table for Coomera Shores AL station.
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4.5.1 Canungra Army TM The Canungra Army TM is located at Canungra on the mainstream of the Coomera River. This station, which is owned and operated by the Department of Natural Resources and Mines (DNRM), has been operational since October 1962. The station commands a catchment area of about 97.35 km2. The reliability of the rating table at this station is very important for accurate estimation of design discharges along the Coomera River.
Because of its importance, the reliability of the rating table at the Canungra Army TM has been the subject of several previous investigations, including Kinhill Cameron McNamara (1992), BoM (1998) and GHD (2000). The Kinhill Cameron McNamara (1992) study adopted the DNRM rating Table 9 for this station and the BoM (1998) study adopted a modified DNRM Table 12. GHD (2000), after an extensive review which included the use of a 2-dimensional hydraulic model for the river reach of interest, adopted DNRM Table 9 for model calibration of events up to 1975 (same as Kinhill, 1992) and BoM’s modified DNRM Table 12 for calibration events after 1975 (same as BoM, 1998). The GHD (2000) design flood discharge estimates for the lower Coomera River are up to 40% lower than the equivalent Kinhill (1992) estimates. To reconcile the differences in design discharge estimates between the two studies, an internal review of the two studies was undertaken by GCCC in 2001. After this review, GCCC (2001) recommended that the modified DNRM Table 12 as the most appropriate and should be used for all calibration events.
The Canungra Army TM rating table was further reviewed in this study. The study team visited the site and commissioned a cross sectional survey of the river reaches upstream and downstream of the gauging station. Figure 8 shows the location of the surveyed cross sections. A hydraulic model (HEC-RAS) incorporating the surveyed cross-sections was used to assess the appropriateness of the different rating tables available for this station. It is noted that the HEC-RAS modelling was based on uniform flows and manning’s ‘n’ values for the study reach.
Figure 9 shows the DNRM Table 9, Table 12 Table 15.01, Table 12 modified by BoM and the Table generated from the HEC-RAS results. It also shows the stream gauging undertaken by DNRM for the gauge site. Table 12 and Table 15.01 are identical. It is of note that all DNRM tables are extrapolated beyond the maximum gauged height of 4.33 m.
Based on the review of all available data and information, it was decided to adopt the modified DNRM Table 12 for the following reasons:
. The adopted rating table fits well to the gauged data; . For extrapolations beyond the maximum gauged height (4.33 m) the adopted table is the closest of all tables to the HEC-RAS model results; . The adopted table produces the most consistent results at downstream (Clagiraba Road and Oxenford Weir) gauging stations; and . The recorded hydrograph at Canungra for the June 1967 event cannot be reproduced by the URBS model even with zero initial and continuing losses if the DNRM rating Table 9 is used because the rated discharges calculated using this rating table are too high.
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Figure 8 – Canungra Army TM and Surveyed Cross Sections
Figure 9 – Adopted and Available Rating Tables @ Canungra Army TM
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4.5.2 Clagiraba Road ALERT The only available rating table for the Clagiraba Road ALERT station has been developed by BoM based on their model calibration results. In the absence of better data, and because of the consistency of results produced when compared with upstream (Canungra) and downstream (Oxenford Weir) stations, the BoM derived rating table is adopted in this study for this station. Figure 10 shows the adopted rating table for the Clagiraba Road station.
Figure 10 - Adopted Rating Table @ Clagiraba Road ALERT
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4.5.3 Oxenford Weir ALERT Oxenford Weir ALERT station is located just upstream of Oxenford Weir. The water level at this station is not influenced by the tide. A rating table for this station is not available from the BoM or any other sources. Hence, a rating table for this station was developed using the results from the Council’s Coomera River MIKE 11 model simulation. Figure 11 shows the adopted rating table for the Oxenford Weir ALERT station.
Figure 11 – Adopted Rating Table @ Oxenford Weir AL
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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. 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 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 to lump 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 initial and continuing loss model and the proportional loss model. The initial and continuing loss model was adopted for Coomera River 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 Coomera River Catchment corresponding to different land classifications as adopted by the City of Gold Coast.
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Table 6 – Coomera River Catchment 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.
The sub-catchment delineation developed by GHD (2000) was used as the ‘starting point’ for the current study. In their study, GHD divided the total catchment into 40 sub-catchments. This study refined the GHD catchment subdivision and increased the number of sub-catchments to 59 using Council’s Master Digital Terrain Model (November 2007), Waterways Layer (2006), Open Drain Layer (August 2007) Pipe Culvert Layer (August 2007), Air Photo (2005) and DNRM’s Digital Elevation Model, Drainage Layer (April 2008), and Ortho-photo maps of the Gold Coast. Figure 12 shows the sub-catchment delineation and drainage paths of Coomera River Catchment. Table 7 and Table 8 show the sub-catchment areas and land uses.
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Figure 12 – Coomera River Catchment – Sub-catchment Delineation and Drainage Path
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Table 7 – Coomera River Catchment – Sub-catchment Areas and Land Uses Sub-Catchment Area (km2) UL UM UH UR UF 1 13.44 0 0 0 0 1 2 17.24 0 0 0 0.17 0.83 3 14.59 0 0 0 0.79 0.21 4 4.64 0 0 0 0.81 0.19 5 2.62 0 0 0 0.71 0.29 6 3.38 0 0 0 0.94 0.06 7 10.32 0 0 0 0.69 0.31 8 0.96 0 0 0 0.91 0.09 9 5.49 0 0 0 0.83 0.17 10 6.62 0 0 0 0.53 0.47 11 11.48 0.01 0 0.01 0.49 0.49 12 6.57 0 0 0 0.09 0.91 13 3.99 0 0 0 0.01 0.99 14 7.01 0 0 0 0.37 0.63 15 6.79 0 0 0 1 0 16 15.98 0 0 0 0.31 0.69 17 7.36 0 0 0 0 1 18 10.53 0 0 0 0.11 0.89 19 4.97 0 0 0 0.03 0.97 20 3.66 0 0 0 0 1 21 6.62 0 0 0 0.13 0.87 22 10.1 0 0 0 0.12 0.88 23 6.03 0 0.01 0.04 0.28 0.67 24 6.71 0 0 0.06 0.48 0.46 25 4.44 0 0 0.11 0.77 0.12 26 5.61 0 0 0 0.41 0.59 27 1.86 0 0 0.31 0.61 0.08 28 9.65 0.04 0 0.1 0.35 0.51 29 4.57 0 0 0.29 0.71 0 30 14.82 0 0 0 0.45 0.55 31 4.12 0 0 0.69 0.13 0.18 32 11.31 0 0 0.07 0.71 0.22 33 6.57 0.03 0 0.07 0.68 0.22 34 13.51 0 0 0.67 0.04 0.29 35 7.64 0 0 0.06 0.49 0.45 36 6 0 0 0.04 0.33 0.63 37 3.72 0 0 0.11 0.67 0.22 38 4.93 0 0 0.17 0.74 0.09 39 13.36 0 0.01 0.18 0.6 0.21 40 1.73 0.05 0.18 0.54 0.22 0.01 41 4.01 0.01 0.01 0.37 0.58 0.03 42 3.57 0.06 0.2 0.31 0.41 0.02 43 7.01 0.03 0.14 0.22 0.46 0.15 44 7.65 0.08 0.08 0.53 0.31 0
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Table 8 - Coomera River Catchment – Sub-catchment Areas and Land Uses (Continued) Sub-Catchment Area (km2) UL UM UH UR UF 45 8.04 0.02 0.1 0.22 0.28 0.38 46 2.7 0.01 0 0.3 0.53 0.16 47 7.13 0.03 0.09 0.35 0.5 0.03 48 8.36 0 0.06 0.56 0.06 0.32 49 7.46 0 0.13 0.6 0.11 0.16 50 13.69 0.03 0.1 0.28 0.16 0.43 51 8.86 0.1 0.06 0.39 0.39 0.06 52 3.35 0 0.23 0.33 0.42 0.02 53 3.12 0.17 0.06 0.32 0.45 0 54 12.37 0 0.08 0.11 0.26 0.55 55 8.62 0.01 0.1 0.32 0.46 0.11 56 5.77 0.02 0.09 0.53 0.27 0.09 57 12.15 0 0.16 0.55 0.16 0.13 58 9.2 0.02 0.18 0.69 0.11 0 59 7.74 0.21 0.28 0.03 0.04 0.44
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6. Model Calibration and Verification
6.1 Selection of Calibration and Verification Events
Coomera River catchment rainfall and river height data for 30 historical flood events between February 1954 and January 2013 were available for this study. These data were provided by the 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 9 shows the selected calibration and verification events for Coomera River catchment. These events cover a wide range of flood discharges including the June 1967 and January 1974 events which have been the subject of detailed investigations in previous modelling studies.
Table 9 - Selected Calibration and Verification Events Event Calibration Verification
January 2013 February 2010 January 2008 June 2005 March 2004 February 1990 January 1974 June 1967
6.2 Calibration Methodology
The emphasis of the model calibration was achieving the best possible fit between the modelled and recorded discharge hydrographs at key locations along the Coomera River and its tributaries for the selected calibration events. For these locations, the calibration attempted to match the modelled and recorded flood peaks and volumes, time of peak and the shape of the hydrographs. The calibrated model was then verified by comparing the model predictions against the discharge hydrographs recorded at 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. 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.
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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 nearest 4 rainfall stations to the sub-catchment centroid. This method ensures that all of the available data were used and that the most appropriate rainfall temporal pattern was assigned to each sub-catchment. Table 10 shows the weighted average rainfall at the selected locations for different events.
Table 10 – Weighted Average Rainfall at Selected Location Beechmont Canungra Clagiraba Oxenford Monterey Coombabah Coomera
Event AL Army TM Rd AL Weir AL Keyes AL Shores AL
(mm) (mm) (mm) (mm) (mm) (mm) (mm)
Jan 13 314 584 578 561 265 300 530 Feb 10 260 285 307 325 274 264 319 Jan 08 288 280 246 215 125 143 204 Jun 05 257 260 267 289 402 432 301 Mar 04 177 195 181 169 129 133 163 Feb 90 164 177 169 172 131 128 168 Jan 74 891 769 851 906 665 675 884 Jun 67 553 547 555 564 447 489 550
6.4 Adopted Model Parameters
Table 11 shows the global catchment and channel parameters adopted for Coomera River catchment for all calibration and verification events.
Table 11 - Adopted Parameters for Calibration and Verification Parameter Adopted Value α (Channel Lag) 0.12 (Catchment Lag) 1.2 m (Catchment non-linearity) 0.65 n 1 F F*0.5
6.5 Initial and Continuing Losses
Table 12 shows the adopted initial and continuing losses for each of the calibration and verification events. The adopted initial losses (20 – 140 mm) are generally consistent for all calibration and verification events. The adopted continuing losses (0.5 – 4.0 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 12 – Adopted Initial and Continues Losses Initial Loss Continues Loss Event IL (mm) CL (mm/hr) Jan 2013 100 1.0 Feb 2010 90 4.0 Jan 2008 35 0.5 Jun 2005 140 2.5 Mar 2004 30 2.0 Feb 1990 20 2.0 Jan 1974 25 0.5 Jun 1967 80 0.5
6.6 Calibration Results
6.6.1 General Comments Good calibration was achieved for the Coomera River catchment. A single set of model parameters were adopted for all five calibration events. The quality of available rainfall data for all events was good. Table 13 shows the comparison of modelled and recorded peak discharges at the key locations for the calibration events.
Table 13 – Modelled and Recorded Peak Discharge at key locations for Coomera River Catchment, Calibration Events Peak Discharge (m3/s)
Event Canungra Army TM Clagiraba Rd AL Oxenford Weir AL
Modelled Recorded Modelled Recorded Modelled Recorded Jan 2013 541 527 1047 * 1779 1819 Feb 2010 568 446 1179 * 2237 2203 Jan 2008 801 733 1222 * 1352 * Jun 2005 150 * 269 255 850 790 Mar 2004 383 368 620 571 755 798 *Station appears to have malfunctioned during the event
Calibration results for individual events are discussed below:
6.6.2 January 2013 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 which is the highest 24 hour rainfall total in Australia.
Table 13 and Figure 16, Figure 17 and Figure 18 in Appendix C: Calibration and Verification Plotshow the comparison of the modelled and recorded discharges at Canungra Army TM, Oxenford Weir AL and Coomera Shores AL respectively. The plots show good match between modelled and recorded discharges in terms of shape, peak, timing and volume of the hydrograph at Canungra Army Tm and Oxenford Weir AL. However the modelled and recorded discharge plots at Coomera Shores AL show a reasonable match in terms of shape and timing of the hydrograph.
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It is of note that Clagiraba Road AL started malfunctioning during the event since 27/01/2013 at 07:45 am.
6.6.3 February 2010 Ex-Tropical Cyclone Olga tracked eastward across the southern border areas of Queensland, heavy rainfall resulted, producing falls in excess of 200 mm throughout the South East region by 9 am on the 7th February. The heaviest rainfalls were recorded at the base of Mount Tamborine with up to 450 mm in 12 hours.
Table 13 above and Figure 19, Figure 20 and Figure 21 in the Appendix C: Calibration and Verification Plot show the modelled and recorded discharges at Canungra Army TM, Oxenford Weir AL and Coomera Shores AL respectively. A reasonable match has been achieved between modelled and recorded discharges at Canungra Army TM and a very good match has been achieved at Oxenford Weir AL for this event. The plot at Coomera Shores AL shows good match between modelled and recorded discharges in terms of shape and timing of peak of the hydrographs.
It is of note that Clagiraba Road AL was malfunctioning during this event.
6.6.4 January 2008 Heavy rainfall occurred overnight on 04 January 2008 in the Gold Coast hinterland area. Recorded rainfall from 32 pluvio and 5 daily stations within and adjacent to Coomera River catchment were used for the calibration. This event started at 9:00 am on 02 January 2008 and continued until 5:00 pm on 08 January 2008.
Table 13 and Figure 22 and Figure 23 in the Appendix C: Calibration and Verification Plot show the comparison of the modelled and recorded discharges at Canungra Army TM and Coomera Shores AL respectively for January 2008 flood event. The calibration plots show good match between modelled and recorded discharges in terms of shape, peak, timing and volume of the hydrographs at Canungra Army TM. At Coomera Shores AL the comparison plot shows very good match between modelled and recorded discharges in terms of shape and timing of peak of the hydrographs.
Clagiraba Road AL and Oxenford Weir ALs were malfunctioning during this event.
6.6.5 June 2005 Intense rainfall burst commenced in Gold Coast from 27 June 2005 to 30 June 2005. Heaviest rainfall occurred on the 29th overnight and the following day morning.
Table 13, Figure 24, Figure 25 and Figure 26 show the comparison between the modelled and recorded discharges at Clagiraba Road AL, Oxenford Weir AL and Coomera Shores AL respectively for June 2005 flood event. Comparison plots show a very good match between modelled and recorded discharges in terms of shape, peak, volume and timing of peak at Clagiraba Rd AL and Oxenford Weir AL. There is also good agreement in the shape and the time of peak of the modelled and recorded hydrographs at Coomera Shores AL.
Canungra Army TM was malfunctioning during this event.
6.6.6 March 2004 Table 13 above and Figure 27, Figure 28 and Figure 29 in the Appendix C: Calibration and Verification Plotshow the comparison between modelled and recorded discharges at Canungra Army TM, Clagiraba Road AL, Oxenford Weir AL respectively for March 2004 flood event. An excellent match between modelled and recorded discharges was achieved for all three stations for this event.
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6.7 Verification Results
The calibrated URBS model was then tested using the verification events viz. February 1990, January 1974 and June 1967 flood events adopting the same global parameters as for the calibration events. It is noted that recorded data for the verification events were only available for the Canungra Army TM station.
Table 14 shows the modelled and recorded peak discharges at Canungra Army TM station for the verification events.
Table 14 - Modelled and Recorded Peak Discharge at key locations for Coomera River Catchment, Verification Events Peak Discharge (m3/s)
Event Canungra Army TM Clagiraba Rd AL Oxenford Weir AL
Modelled Recorded Modelled Recorded Modelled Recorded Feb 1990 289 289 510 * 811 * Jan 1974 572 453 1159 * 2013 * Jun 1967 560 517 1023 * 1395 * *Data not available
6.7.1 February 1990 Table 14 above and Figure 30 in the Appendix C: Calibration and Verification Plotshow the modelled and recorded discharges at Canungra Army TM for the February 1990 event. Good match between modelled and recorded discharges is achieved for this event.
6.7.2 January 1974 Table 14 above and Figure 31 in the Appendix C: Calibration and Verification Plot show the modelled and recorded discharges at Canungra Army TM for the January 1974 event. A reasonable match between modelled and recorded discharges is achieved for this event.
6.7.3 June 1967 Table 14 above and Figure 32 in the Appendix C: Calibration and Verification Plot show the modelled and recorded discharges at Canungra Army TM for the June 1967 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 within the Coomera River catchment was available at the Canungra Army TM Gauging Station (GS-146010A). Therefore, design flood discharges in the Coomera River at Canungra Army TM 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 Canungra Army TM were available from DNRM for the period 1962 to 2013 (51 years). The recorded annual peak gauge heights were then converted to annual peak discharges using the rating table adopted for this study (Section 4.5.1 ).
7.3 Annual Peak Discharge Analysis
Figure 13 and Table 15 show the flood frequency distribution and the FFA estimated design peak discharges respectively at the Canungra Army TM gauging station.
Figure 13 - Flood Frequency Analysis @ Canungra Army TM (GS - 146010A)
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Table 15 - FFA Estimated Peak Design Discharge @ Canungra Army TM FFA Estimated Peak Discharge (m3/s) 95% 5% ARI Confidence Fitted Confidence (Year) Limit Value Limit 2 93 113 137 5 225 273 331 10 314 393 494 20 396 528 703 50 492 734 1095 100 553 915 1514
The FFA estimated design discharges in this study are compared to other methodologies and other studies in Section 9 of this report.
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8. Design Flood Estimation
The calibrated URBS model was used to estimate the design flood discharges throughout the Coomera River catchment using the design rainfall data described in Section 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 has undertaken 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 recommended methodology is summarized in Table 16 and adopted in this study.
It should be noted that this methodology was later modified for other catchments under investigation where it was found that design flow estimates between the 100 year and the 500 year ARI were anomalous due to IFD interpolation and temporal pattern issues. No such anomalies were found with this study and thus the original methodology as recommended by WRM and reviewed by Council’s PRG was adopted.
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Table 16 - 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 duration ≥ 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. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 47 of 92 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 . Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 48 of 92 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 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 Gold Coast 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. In addition, at the time of review in 2013 it has been identified that the design rainfall intensities at the upstream of Canungra Army TM are lower than those downstream in the lower Coomera catchment. It is counter intuitive given the high altitude of the Canungra catchment (elevation typically 400 mAHD) and the pronounced orographic effects evident for other hinterland catchments across the Gold Coast. To address this issue Don Carroll Project Management recommended scaling the IFD in the upper Coomera catchments up to 500 year ARI (Carroll 2013, 12.18 ). The anomaly occurred because of interpolation in an area with very strong rainfall gradients and one which adjoins the Logan catchment whose intensities are typically half those of the hinterland catchments. Application of this scaling factor resulted in design intensities similar to those for the Nerang catchment to Clearview – which is considered reasonable. Figure 14 shows the anomaly in which the sub-area rainfall intensities for the 1 in 100 year ARI 9 hour storm are similar to those for the Nerang and Coomera catchment. Height Contours based on average sub-area elevation are also shown for comparative purpose on the same figure. As per Don Carroll Project Management’s recommendation, the sub-area rainfall intensities highlighted in yellow are scaled up as per Table 17 below: Table 17 – Sub-area Rainfall Intensity Scaling Factor for Upper Coomera Catchments ARI Scaling (Years) Factor (%) 2 0 5 0 10 5 20 10 50 15 100 25 200 25 500 25 The average rainfall intensities for each duration and ARI are then converted to rainfall depths. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 49 of 92 Figure 14 – 1 in 100 Year 9 Hour Sub-area Rainfall Intensities with Sub-area Average Elevation for Coomera and Nerang catchment Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 50 of 92 8.2.2 Areal Reduction Factors The point design rainfall estimates at the centroid of each sub-area are 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 is 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 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 are adopted in this study for durations shorter than 24 hours. Table 18 shows the adopted ARFs for design event simulation. For design event simulation the ARF calculation is based on total catchment area and for comparison with FFA results the ARF calculation is based on the catchment area upstream of Canungra Army TM gauging station. Table 18 - Adopted Areal Reduction Factors for Coomera River Catchment Areal Reduction Factor Catchment U/S of Storm Duration (Hour) Total Catchment Area Canungra Army TM (441 km2) (97.35 km2) 72 0.949 0.975 48 0.933 0.963 36 0.919 0.953 24 0.896 0.935 18 0.896 0.935 12 0.896 0.935 9 0.896 0.935 6 0.896 0.935 4.5 0.896 0.935 3 0.896 0.935 1.5 0.896 0.935 1 0.896 0.935 0.5 0.896 0.935 8.2.3 Temporal Patterns A sub-duration burst inconsistency within the Council’s temporal patterns (AWE, 2000) has been identified recently. These temporal patterns developed by AWE (2000), adopted by Council in 2000, produces design rainfalls that contain sub-bursts of greater ARI than storm burst duration itself. 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 burst rainfalls that have a greater ARI than the equivalent design rainfalls given by the 6 hour, 12 hour, 24 hour and 48 hour storm temporal patterns. Further this problem is evident 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 and large design discharges for Gold Coast catchments. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 51 of 92 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. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 52 of 92 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 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 53 of 92 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 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 54 of 92 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 16. 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 3.0 5 40 1.5 10 30 0.75 20 20 0.3 50 0 0.0 100 0 0.0 8.2.6 Design Discharge Table 21 and Table 22 show the design discharges and critical storm durations respectively at key locations throughout the Coomera River 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 Beechmont TM Back Creek 18 35 49 65 86 104 Canungra Army TM Coomera River 113 264 374 513 694 844 Clagiraba RD AL Coomera River 207 490 706 960 1287 1550 Oxenford Weir AL Coomera River 391 840 1152 1488 1988 2333 Pacific Highway Coomera River 406 865 1186 1536 2049 2395 Coomera Shores AL Coomera River 424 896 1232 1617 2107 2455 Pacific Highway Saltwater Creek 72 142 191 242 327 367 Pacific Highway Coombabah Ck 27 62 83 108 149 167 Gold Coast Highway Coombabah Ck 66 134 174 221 311 346 River Mouth Coomera 551 1118 1507 1944 2548 2932 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 55 of 92 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 Beechmont TM Back Creek 24.0 9.0 9.0 4.5 1.5 1.5 Canungra Army TM Coomera River 36.0 24.0 12.0 12.0 9.0 9.0 Clagiraba RD AL Coomera River 36.0 24.0 12.0 12.0 9.0 9.0 Oxenford Weir AL Coomera River 36.0 24.0 24.0 9.0 9.0 9.0 Pacific Highway Coomera River 36.0 24.0 24.0 12.0 9.0 9.0 Coomera Shores AL Coomera River 36.0 24.0 24.0 12.0 9.0 12.0 Pacific Highway Saltwater Creek 24.0 9.0 4.5 4.5 1.0 1.0 Pacific Highway Coombabah Ck 12.0 9.0 9.0 4.5 1.5 1.5 Gold Coast Highway Coombabah Ck 12.0 9.0 9.0 4.5 1.5 1.5 River Mouth Coomera 36.0 36.0 24.0 12.0 9.0 9.0 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 56 of 92 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 given in the Table 23 and Section 8.2.1 : 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 (ARFs) 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 inTable 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 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 57 of 92 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 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 58 of 92 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 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 59 of 92 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 16. 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 0.0 500 0.0 0.0 1000 0.0 0.0 2000 0.0 0.0 8.3.6 Design Peak Discharges Table 27 and Table 28 show the design discharges and critical storm durations respectively at key locations throughout the Coomera River 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 Beechmont TM Back Creek 120 135 166 182 Canungra Army TM Coomera River 896 1021 1111 1218 Clagiraba RD AL Coomera River 1667 1903 2054 2254 Oxenford Weir AL Coomera River 2544 2926 3065 3362 Pacific Highway Coomera River 2615 3007 3143 3443 Coomera Shores AL Coomera River 2711 3126 3258 3573 Pacific Highway Saltwater Creek 407 457 685 753 Pacific Highway Coombabah Ck 191 217 338 371 Gold Coast Highway Coombabah Ck 397 449 666 730 River Mouth Coomera 3239 3729 3997 4379 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 60 of 92 Table 28 – Critical Storm Duration at Key Locations, 200 to 2000 Year ARI Critical Storm Duration (Hrs) 200 500 1000 2000 Location Stream Name Year Year Year Year ARI ARI ARI ARI Beechmont TM Back Creek 1.5 1.5 1.5 1.5 Canungra Army TM Coomera River 6.0 9.0 4.5 4.5 Clagiraba RD AL Coomera River 6.0 6.0 4.5 4.5 Oxenford Weir AL Coomera River 9.0 9.0 6.0 6.0 Pacific Highway Coomera River 9.0 12.0 9.0 9.0 Coomera Shores AL Coomera River 12.0 12.0 9.0 9.0 Pacific Highway Saltwater Creek 1.0 1.0 1.0 1.0 Pacific Highway Coombabah Ck 1.5 1.5 1.5 1.5 Gold Coast Highway Coombabah Ck 3.0 3.0 1.5 1.5 River Mouth Coomera 12.0 12.0 9.0 9.0 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 61 of 92 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 were also adopted. 8.4.2 Areal Reduction Factors Areal reduction factors were already included in the GSDM and GTSMR methodology (BoM 2003a and BoM 2003b) so additional ARFs were 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 were also adopted. 8.4.4 Spatial Distribution Rainfall spatial distributions were 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 0.0 mm/hr were adopted for all the durations of PMPDF. 8.4.6 Design Peak Discharges Table 29 shows the PMPDF discharge and critical storm duration at key locations throughout the Coomera River catchment. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 62 of 92 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) Beechmont TM Back Creek 354 1.5 Canungra Army TM Coomera River 2839 9.0 Clagiraba RD AL Coomera River 5301 4.5 Oxenford Weir AL Coomera River 7997 9.0 Pacific Highway Coomera River 8263 9.0 Coomera Shores AL Coomera River 8676 12.0 Pacific Highway Saltwater Creek 1153 1.5 Pacific Highway Coombabah Ck 584 1.5 Gold Coast Highway Coombabah Ck 1107 3.0 River Mouth Coomera 10599 12.0 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 63 of 92 8.5 Joint Probability Approach The Joint Probability Approach (JPA) is also known as Monte Carlo simulation technique has been under development for last few years. 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 TPT methodology the BOM burst IFD tables are used. On the other hand the event based IFD tables derived from the raw pluviographs are used in CRC-CH. 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 Gold Coast region Don Carroll has 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. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 64 of 92 Table 30 shows the adopted parameters and losses for TPT. Table 30 - Adopted Parameters and Losses for TPT Adopted Parameters and Losses α 0.12 β 1.2 m 0.65 n 1 F F*0.5 CL (mm/hr) 0.1 Min IL (mm) 0 Stdv IL (mm) 20 Mean IL (mm) 20 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 Beechmont TM 37 52 66 81 102 118 131 155 173 205 Canungra TM 254 370 467 562 694 806 915 1047 1188 1361 Clagiraba AL 474 692 869 1047 1292 1491 1699 1921 2164 2488 Oxenford AL 786 1110 1383 1630 2013 2273 2558 2960 3297 3945 M1 Coomera 797 1136 1418 1671 2065 2316 2596 3031 3350 4005 Coomera S AL 828 1169 1450 1713 2106 2381 2670 3084 3411 4049 M1 Salt W CK 176 215 258 316 389 448 507 599 684 824 GC Hway Coomb 149 190 225 277 339 398 441 525 601 729 River Mouth 1048 1434 1770 2084 2576 2890 3230 3812 4302 5122 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 65 of 92 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 Beechmont TM 4.5 4.5 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Canungra TM 9.0 12.0 12.0 9.0 12.0 9.0 9.0 9.0 12.0 9.0 Clagiraba AL 9.0 12.0 9.0 9.0 12.0 9.0 9.0 12.0 12.0 9.0 Oxenford AL 9.0 12.0 12.0 12.0 12.0 12.0 9.0 12.0 12.0 9.0 M1 Coomera 12.0 12.0 12.0 12.0 12.0 9.0 9.0 12.0 12.0 9.0 Coomera S AL 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 9.0 M1 Salt W CK 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 GC Hway Coomb 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 River Mouth 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 12.0 9.0 8.5.2 CRC-CH The adopted steps in CRC-CH can be summarized as below: Storm core duration is selected from an exponential or gamma probability distribution fitted to the available pluvio data of the area. A conditional distribution in the form of IFD is established. Temporal patterns are randomly selected based on multiplicative cascade model. 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 0.12 β 1.2 m 0.65 n 1 F F*0.5 CL (mm/hr) 0.1 Min IL (mm) 0 Stdv IL (mm) 30 Mean IL (mm) 30 Max IL (mm) 100 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 66 of 92 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 Beechmont TM 52 77 97 124 170 194 257 Canungra TM 220 318 404 515 678 868 1099 Clagiraba AL 507 721 921 1175 1565 1902 2496 Oxenford AL 981 1396 1778 2236 2875 3599 4437 M1 Coomera 988 1400 1787 2237 2980 3613 4516 Coomera S AL 992 1404 1779 2235 2903 3637 4441 M1 Salt W CK 172 242 297 365 474 568 628 GC Hway Coomb 156 219 272 329 416 521 618 River Mouth 1109 1543 1937 2454 3186 3983 4847 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 Canungra Army TM gauging station only. JPA estimated design discharges in this study are compared with other methodologies and other studies in section 9 of this report. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 67 of 92 9. Comparison In the current study peak design discharges at Canungra Army TM Gauging Station (GS) were 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) methodologies. Figure 15 shows the peak design discharge for different ARIs at Canungra Army TM GS as estimated by DEA, FFA, TPT MC and CRC-CH MC approach. As the comparison was made at Canungra Army TM GS so the adopted ARF for all estimations are based on catchment area only upstream of Canungra Army TM GS. Figure 15 - Peak Design Discharge comparison plot for different modelling approaches Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 68 of 92 Table 35 shows the peak design discharges at Canungra Army TM 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 Canungra Army TM GS Peak Design Discharge @ Canungra Army TM (m3/s) ARI Current Study Kinhill 1995 GHD 2000 (Year) DEA FFA TPT MC CRC-CH MC DEA FFA DEA FFA 2 121 113 254 220 - 116 - - 5 280 273 370 318 420 323 426 375 10 396 393 467 404 560 539 515 610 20 539 528 562 515 850 812 658 770 50 726 734 694 678 990 1270 734 880 100 883 915 806 868 1120 1696 842 - The following is of note with regards to Figure 15 and Table 35: The agreement between DEA and FFA estimates of the current study is excellent. Good agreement between DEA, TPT MC and CRC-CH MC estimates for ARI 10 and above of the current study are achieved. The agreement between the DEA and the FFA estimates in the current study is better when compared to the Kinhill 1995 and GHD 2000 studies. The FFA in the current study is based on a longer (1962 - 2013) period of recorded data. The peak design discharges estimated in this study are generally lower than the discharges estimated by Kinhill 1995 and GHD 2000 study. The followings are of note with regards to current and previous studies: In the Kinhill 1995 study the design rainfall depths for different ARIs are calculated using the methodology described in Australian Rainfall and Runoff 1987. The rainfall depths are determined at Canungra near the centre of the catchment and assumed uniformly distributed over the catchment. The spatial variation and the areal reduction factors are not considered in this study. However the current study shows the spatial variation is significant in Coomera catchment. The details of these variations are discussed in section 8.2.1 of this report. The spatial variation and the areal reduction factor have a substantial impact on peak design discharges. The Kinhill study also used a different rating table at the Canungra Army TM station. The details of the rating table are discussed in section 4.5.1 . In the GHD 2000 study, the spatial variation in design rainfall intensity is accounted in the model by dividing the catchment into three regions. The design rainfall intensities for each region are determined from the maps prepared by Australian Water Engineering (AWE 1998). The rainfall intensity in each region is then converted to rainfall depth and assigned to each sub area within that region. An areal reduction factor was not applied for design rainfalls in the GHD study. However the current study revealed that the entire catchment divided into three regions was not adequate to address the issue of spatial distribution. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 69 of 92 In the current study the design rainfall intensities for every sub-area within the catchment were calculated using updated AWE maps. In the AWE 1998 study the skew coefficient for Gold Coast was adopted as zero. During this study, WRM updated Council’s IFD utility by introducing a skew coefficient as per section 1, book II volume 1 of IEAust (1998). The rainfall intensities in the sub-catchments upstream of Canungra Army TM are scaled up as per section 8.2.1 . The rainfall intensity in each sub-area is then converted to rainfall depth and an areal reduction factor is applied to estimate the sub- area design rainfall depth. The current study identified the sub-duration inconsistencies in AWE 2000 temporal patterns and these patterns are filtered by WRM according to the methodology outlined in Australian Rainfall and Runoff (1998) and BoM (1991). The filtered AWE 2000 temporal patterns, removed the sub-duration burst inconsistencies, were adopted in the current study. The unfiltered patterns produce unrealistically long critical storm durations and higher peak discharges. A sensitivity analysis was undertaken to assess the impact of sub-duration burst inconsistencies on the critical storm durations and the design peak discharges. The analysis revealed that the critical storm duration at Canungra Army TM station for 100 year ARI design event using ARR 1987, AWE 2000 and filtered AWE 2000 temporal patterns are 24 hours, 72 hours and 9 hours respectively. Critical storm duration of 24 hours or 72 hours is unrealistically long for Canungra Army TM station whereas the critical storm duration of 9 hours is considered more realistic. The adopted rating table at Canungra Army TM station is another important reason that causes differences in design discharges in the different studies. The 1995 Kinhill study adopted the DNRM rating Table 9 for model calibration. GHD 2000 study adopted DNRM rating Table 9 for calibration events up to June 1983 and DNRM rating Table 12 for calibration events after June 1983. However during this study a comprehensive investigation has been carried out to find the most appropriate rating table at this station. The investigation included a site visit, detailed cross sectional survey both upstream and downstream of the station and hydraulic modelling of the area of interest. The DNRM rating Table 12 as modified by BoM in 1998 is found the most appropriate and is adopted for this study. The RORB hydrological model developed in the Kinhill study were calibrated against three historical events. A single set of model parameters were adopted for all three calibration events, only the rainfall losses were adjusted to achieve the best possible fit between the modelled and recorded hydrographs. In the GHD study, the URBS model was calibrated against thirteen historical events. The model parameters and the losses were different for each calibration event. The average of calibration model parameters and the loss values were calculated and adopted for the design event simulations. In the current study the URBS model is developed based on current land uses, calibrated and verified against eight major historical events. Calibration events included four significant recent events in January 2013, February 2010, January 2008 and June 2005 with a good coverage of rainfall and stream flow data. A single set of model parameters are adopted for all calibration/verification events, only the rainfall losses are adjusted to achieve the best possible fit between the modelled and recorded hydrographs. Good calibrations are achieved for January 2013, February 2010, January 2008, June 2005 and March 2004 historical events. The calibrated model is then verified against February 1990, January 1974 and June 1967 historical events satisfactorily. A FFA of peak annual discharges at Canungra Army TM station was carried out in all three studies. In the Kinhill study, there were 26 years of recorded data, in the GHD study there were 35 years of recorded data and in the current study there were 51 years of recorded data for the analysis. It is also noted that the previous studies did not include the January 2013, January 2008 and June 2005 events which are quite significant for the FFA Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 70 of 92 In the current study a detailed Joint Probability Analysis (JPA) for Total Probability Theorem Monte Carlo (TPT MC) and Cooperative Research Centre – Catchment Hydrology Monte Carlo (CRC-CH MC) has been undertaken for the Coomera River catchment. The design discharges estimated by the current study Design Event Approach (DEA) are supported by FFA, TPT MC and CRC-CH MC. The peak design discharges at Canungra Army TM for 1 in 100 year ARI are 883 m3/s, 915 m3/s, 806 m3/s and 868 m3/s estimated by Current study DEA, FFA, TPT MC and CRC-CH MC respectively. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 71 of 92 10. Conclusion An URBS hydrological model for Coomera River 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, February 2010, January 2008, June 2005 and March 2004 historical events and verified against February 1990, January 1974 and June 1967 historical events. The calibrated model was then used to estimate the design flood discharges at different locations within the Coomera River catchment for 2, 5, 10, 20, 50, 100, 200, 500, 1000 and 2000 year ARI and PMP design flood events. The design discharges estimated by the model have been compared and reconciled with FFA estimates of design discharges at Canungra Army TM gauging station. The FFA was undertaken for 51 (1962-2013) years of recorded data. A 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 Coomera River catchment is robust – it is supported by Flood Frequency Analysis and Joint Probability Analysis. The output of this study can be used as input to the hydraulic modelling for further studies of Coomera River catchment. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 72 of 92 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. Coomera River catchment URBS model design rainfall and temporal pattern be reviewed after the next release of Australian Rainfall and Runoff. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 73 of 92 12. Reference 12.1 Kinhill (1992) Coomera River Flood Hydrology Report prepared by Kinhill Cameron McNamara Pty Ltd for Albert Shire Council, May 1992 12.2 Kinhill (1995) Coomera River Flood Studies Report prepared by Kinhill Cameron McNamara Pty Ltd for Gold Coast City Council, November 1995 12.3 Kinhill (1998) Coomera River Revised Hydrology Report prepared by Kinhill Pty Ltd for Gold Coast City Council, June 1998 12.4 GHD (2000) Coomera River Hydrological Model Report Prepared by Gutteridge Haskins & Davey Pty Ltd for Gold Coast City Council, February 2001 12.5 GCCC (2001) Coomera Hydrology Update Report prepared by Gold Coast City Council for Gold Coast City Council, April 2001 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 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 74 of 92 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 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 75 of 92 13. Appendix A: URBS Model Sub-catchment Areas and Land Uses Table 36 - Coomera Sub-catchment Areas and Land Uses Sub-Catchment Area (km2) UL UM UH UR UF 1 13.44 0 0 0 0 1 2 17.24 0 0 0 0.17 0.83 3 14.59 0 0 0 0.79 0.21 4 4.64 0 0 0 0.81 0.19 5 2.62 0 0 0 0.71 0.29 6 3.38 0 0 0 0.94 0.06 7 10.32 0 0 0 0.69 0.31 8 0.96 0 0 0 0.91 0.09 9 5.49 0 0 0 0.83 0.17 10 6.62 0 0 0 0.53 0.47 11 11.48 0.01 0 0.01 0.49 0.49 12 6.57 0 0 0 0.09 0.91 13 3.99 0 0 0 0.01 0.99 14 7.01 0 0 0 0.37 0.63 15 6.79 0 0 0 1 0 16 15.98 0 0 0 0.31 0.69 17 7.36 0 0 0 0 1 18 10.53 0 0 0 0.11 0.89 19 4.97 0 0 0 0.03 0.97 20 3.66 0 0 0 0 1 21 6.62 0 0 0 0.13 0.87 22 10.1 0 0 0 0.12 0.88 23 6.03 0 0.01 0.04 0.28 0.67 24 6.71 0 0 0.06 0.48 0.46 25 4.44 0 0 0.11 0.77 0.12 26 5.61 0 0 0 0.41 0.59 27 1.86 0 0 0.31 0.61 0.08 28 9.65 0.04 0 0.1 0.35 0.51 29 4.57 0 0 0.29 0.71 0 30 14.82 0 0 0 0.45 0.55 31 4.12 0 0 0.69 0.13 0.18 32 11.31 0 0 0.07 0.71 0.22 33 6.57 0.03 0 0.07 0.68 0.22 34 13.51 0 0 0.67 0.04 0.29 35 7.64 0 0 0.06 0.49 0.45 36 6 0 0 0.04 0.33 0.63 37 3.72 0 0 0.11 0.67 0.22 38 4.93 0 0 0.17 0.74 0.09 39 13.36 0 0.01 0.18 0.6 0.21 40 1.73 0.05 0.18 0.54 0.22 0.01 41 4.01 0.01 0.01 0.37 0.58 0.03 42 3.57 0.06 0.2 0.31 0.41 0.02 43 7.01 0.03 0.14 0.22 0.46 0.15 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 76 of 92 Sub-Catchment Area (km2) UL UM UH UR UF 44 7.65 0.08 0.08 0.53 0.31 0 45 8.04 0.02 0.1 0.22 0.28 0.38 46 2.7 0.01 0 0.3 0.53 0.16 47 7.13 0.03 0.09 0.35 0.5 0.03 48 8.36 0 0.06 0.56 0.06 0.32 49 7.46 0 0.13 0.6 0.11 0.16 50 13.69 0.03 0.1 0.28 0.16 0.43 51 8.86 0.1 0.06 0.39 0.39 0.06 52 3.35 0 0.23 0.33 0.42 0.02 53 3.12 0.17 0.06 0.32 0.45 0 54 12.37 0 0.08 0.11 0.26 0.55 55 8.62 0.01 0.1 0.32 0.46 0.11 56 5.77 0.02 0.09 0.53 0.27 0.09 57 12.15 0 0.16 0.55 0.16 0.13 58 9.2 0.02 0.18 0.69 0.11 0 59 7.74 0.21 0.28 0.03 0.04 0.44 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 77 of 92 14. Appendix B: URBS Catchment Definition File COOMERA RIVER URBS Model {Model built by reviewed by (2009/10) and (2013/14) } MODEL: SPLIT USES: L, U, F*0.5 DEFAULT PARAMETERS: alpha=0.12 m=0.65 beta=1.2 n=1.0 CATCHMENT DATA FILE = Coomera_00.csv Rain #1 L = 3.66 Route Thru #2 L = 4.97 Add Rain #2 L = 4.73 Route Thru #3 L = 4.47 Add Rain #3 L = 5.41 Store. Rain #4 L = 3.85 Get. Route Thru #5 L = 1.83 Add Rain #5 L = 1.17 Store. Rain #6 L = 2.2 Store. Rain #7 L = 3.64 Get. Route Thru #8 L = 0.70 Add Rain #8 L = 0.77 Get. Route Thru #9 L = 2.68 Add Rain #9 L = 2.67 Store. Rain #10 L = 3.71 Get. Route Thru #11 L = 3.96 Add Rain #11 L = 4.02 Store. Rain #12 L = 2.21 Get. Print.Canungra {X = 518,768.38, Y = 6,900,176.22} {Contribution from Sc1 to SC12} Route Thru #13 L = 1.86 Add Rain #13 L = 1.77 Store. Rain #14 L = 3.08 Store. Rain #15 L = 4.08 Print.Beechmon {X = 518,511.35 , Y = 6,888,960.98} {Contribution from Sc15 only} Route Thru #16 L = 4.79 Add Rain #16 L = 5.68 Get. Route Thru #17 L = 2.93 Add Rain #17 L = 1.97 Store. Rain #18 L = 4.48 Get. Route Thru #19 L = 1.33 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 78 of 92 Add Rain #19 L = 1.34 Get. Route Thru #20 L = 1.64 Add Rain #20 L = 1.01 Store. Rain #21 L = 2.47 Get. Route Thru #22 L = 1.99 Add Rain #22 L = 2.63 Print.Clagirab {X = 524,934.10 , Y = 6,904,683.34} {Contribution from } Store. Rain #23 L = 3.05 Route Thru #24 L = 1.6 Add Rain #24 L = 3.18 Get. Route Thru #25 L = 2.12 Add Rain #25 L = 1.86 Store. Rain #26 L = 2.4 Get. Route Thru #27 L = 0.92 Add Rain #27 L = 0.57 Store. Rain #28 L = 3.16 Get. Route Thru #29 L = 1.68 Add Rain #29 L = 2.82 Store. Rain #30 L = 4.31 Store. Rain #31 L = 2.08 Get. Route Thru #32 L = 1.64 Add Rain #32 L = 2.23 Get. Route Thru #33 L = 1.13 Add Rain #33 L = 1.25 Store. Rain #35 L = 2.37 Store. Rain #36 L = 2.57 Get. Route Thru #37 L = 1.73 Add Rain #37 L = 0.79 Store. Rain #34 L = 4.75 Get. Route Thru #38 L = 2.01 Add Rain #38 L = 2.30 Get. {Factor = 2.5} {***************************} Route Thru #39 L = 3.21 Add Rain #39 L = 1.45 Print.Oxenford {X = 528,835.67, Y = 6,914,159.15} Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 79 of 92 {SC 1-39} Route Thru #40 L = 1.49 Store. Rain #40 L = 0 Print.LH_SC40 {X = 528,061.89, Y = 6,914,286.33} {Contribution from Sc40 only} Get. Route Thru #40 L = 2.08 Store. Rain #41 L = 0 Print.LH_SC41 {X = 527,732.42, Y = 6,915,304.04} {Contribution from Sc41 only} Route Thru #41 L = 1.92 Get. Route Thru #42 L = 0.79 Store. Rain #42 L = 0 Print.LH_SC42 {X = 529,763.15, Y = 6,915,616.33} {Contribution from Sc42 only} Get. Route Thru #42 L = 0.97 Store. Rain #43 L = 0 Print.LH_SC43 {X = 528,299.39, Y = 6,917,537.14} {Contribution from Sc43 only} Route Thru #43 L = 4.83 Get. Print.Pac_Hwy {X = 530,496.32, Y = 6,916,250.37} Route Thru #44 L = 2.98 Store. Rain #44 L = 0 Print.LH_SC44 {X = 533,178.00, Y = 6,916,909.17} {Contribution from Sc44 only} Get. Route Thru #44 L = 2.37 Store. Rain #45 L = 0 Print.LH_SC45 {X = 530,567.56, Y = 6,919,651.71} {Contribution from Sc45 only} Route Thru #45 L = 2.15 Route Thru #46 L = 2.14 Store. Rain #46 L = 0 Print.LH_SC46 {X = 531,939.56, Y = 6,918,477.24} {Contribution from Sc46 only} Get. Route Thru #46 L = 2.03 Route Thru #44 L = 0.79 Get. Route Thru #47 L = 1.21 Store. Rain #47 L = 0 Print.LH_SC47 {X = 534,928.57, Y = 6,919,728.85} {Contribution from Sc47 only} Get. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 80 of 92 Print.CoomeraS {X = 534,928.57 , Y = 6,919,728.85} Route Thru #47 L = 1.04 Route Thru #49 L = 2.72 Store. Rain #49 L = 0 Print.LH_SC49 {X = 537,556.32, Y = 6,917,726.78} {Contribution from Sc49 only} Get. Route Thru #49 L = 0.84 Store. Rain #53 L = 0 Print.LH_SC53 {X = 535,951.35, Y = 6,916,871.03} {Contribution from Sc53 only} Route Thru #53 L = 1.63 Get. Store. Rain #50 L = 4.47 Route Thru #51 L = 0.78 Add Rain #51 L = 0 Print.TH_SC51 {X = 530,764.87, Y = 6,913,138.46} {Contribution from Sc50-51} Route Thru #51 L = 3.98 Route Thru #52 L = 1.70 Store. Rain #52 L = 0 Print.LH_SC52 {X = 533,419.35, Y = 6,915,680.84} {Contribution from Sc52 only} Get. Route Thru #52 L = 1.61 Route Thru #58 L = 3.77 Store. Rain #54 L = 4.26 Route Thru #55 L = 0.25 Store. Rain #55 L = 1.41 Get. Route Thru #55 L = 1.45 Route Thru #56 L = 1.48 Add Rain #56 L = 2.45 Print.TH_SC56 {X = 534,172.94, Y = 6,911,780.26} {Contribution from Sc54-56} Route Thru #57 L = 1.70 Store. Rain #57 L = 0 Print.LH_SC57 {X = 534,767.20, Y = 6,913,150.82} {Contribution from Sc57 only} Get. Route Thru #57 L = 1.52 Store. Rain #59 L = 0 Print.LH_SC59 {X = 536,427.06, Y = 6,911,287.8} Route Thru #59 L = 2.50 Route Thru #58 L = 2.94 Get. Route Thru #58 L = 3.08 Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 81 of 92 Store. Rain #58 L = 0 Print.LH_SC58 {X = 537,532.11, Y = 6,915,421.62} {Contribution from Sc58 only} Get. Get. Route Thru #58 L = 1.79 Get. Route Thru #49 L = 1.48 Print.Coast {X = 538,799.31, Y = 6,916,532.81} Store. Rain #48 L = 0 Print.LH_SC48 {X = 537,582.57 , Y = 6,920,209.4} Route Thru #48 L = 2.88 Get. Print.LH_SC48_Out {X = 538,845.38, Y = 6,921,459.14} {Contribution total from all sub-areas} END OF CATCHMENT DATA. Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 82 of 92 15. Appendix C: Calibration and Verification Plot Figure 16 - January 2013 Calibration @ Canungra Army TM Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 83 of 92 Figure 17 - January 2013 Calibration @ Oxenford Weir AL Figure 18 - January 2013 Calibration @ Coomera Shores AL Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 84 of 92 Figure 19 - February 2010 Calibration @ Canungra Army TM Figure 20 - February 2010 Calibration @ Oxenford Weir AL Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 85 of 92 Figure 21 - February 2010 Calibration @ Coomera Shores AL Figure 22 - January 2008 Calibration @ Canungra Army TM Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 86 of 92 Figure 23 - January 2008 Calibration @ Coomera Shores AL Figure 24 - June 2005 Calibration @ Clagiraba Road AL Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 87 of 92 Figure 25 - June 2005 Calibration @ Oxenford Weir AL Figure 26 - June 2005 Calibration @ Coomera Shores AL Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 88 of 92 Figure 27 - March 2004 Calibration @ Canungra Army TM Figure 28 - March 2004 Calibration @ Clagiraba Road AL Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 89 of 92 Figure 29 - March 2004 Calibration @ Oxenford Weir AL Figure 30 - February 1990 Verification @ Canungra Army TM Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 90 of 92 Figure 31 - January 1974 Verification @ Canungra Army TM Figure 32 - June 1967 Verification @ Canungra Army TM Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 91 of 92 Council of the City of Gold Coast PO Box 5042 GCMC Qld 9729 P 1300 GOLDCOAST E [email protected] W cityofgoldcoast.com.au Coomera River Catchment – Hydrological Study, August 2014 TRACKS-#45484061-v1 Page 92 of 92