Minnegang Creek Flood Study Report - Wollongong City Council

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ABBREVIATIONSAEPAHDARIAR&RDCPIFDLEPMIKE 11Annual Exceedence ProbabilityAustralian Height DatumAverage Recurrence IntervalAustralian Rainfall and RunoffDevelopment Control PlanIntensity-frequency-durationLocal Environmental Planthe unsteady-state hydraulic model used in thisstudyNSWPMFPMPPRMNew South WalesProbable Maximum FloodProbable Maximum PrecipitationProbabilistic Rational MethodRAFTS Runoff Analysis and Flow TrainingSimulation (the hydrologic model used in thisstudy)RatHGLRational Hydraulic Grade Line (the pipedstormwater network analysis model used inthis study)SV8507-D0-001 Rev 218/10/02viii
1 IntroductionMinnegang Creek is situated approximately 8.5 km south of Wollongong. Significantflooding has previously occurred within parts of the Minnegang Creek catchment.Halliburton KBR Pty Ltd (Halliburton KBR) was engaged by Wollongong CityCouncil (Council) to undertake the preparation of a Floodplain Risk Management Planfor the Minnegang Creek catchment.The Floodplain Risk Management Plan is being developed in three stages; a FloodStudy, Floodplain Risk Management Study and Floodplain Risk Management Plan.This is consistent with the approach recommended in the NSW Government’sFloodplain Management Manual: the management of flood liable land (2001).This Flood Study, as the first stage of the above process, aims to define the existingflood behaviour in the Minnegang Creek catchment for the 20%, 5%, 2% and 1%Annual Exceedence Probability (AEP) floods as well as the Probable Maximum Flood(PMF). Flood behaviour has been defined by:• design flows• flood surface profiles• flow velocities• flood extents• flood contours.The second stage will be the preparation of a Floodplain Risk Management Study todevelop and assess possible floodplain management options to address and minimisethe impacts from flooding, investigate flood hazards and define flood damages. Thefinal stage will be the development of a cost-effective Floodplain Risk ManagementPlan recommending a program of measures for implementation within the study area.The Minnegang Creek catchment is described in Section 2 of this report. Section 3details the background to the Study, including previous studies in the area and theparties involved in this current study. Section 4 presents the details and justificationfor the adopted methodology for the hydrologic modelling of the catchment. Thehydraulic modelling procedure and results are discussed in detail in Section 5.Findings for the 1%, 2%, 5% and 20% AEP floods are presented in Section 6. ThePMF flood profile is also presented in Section 6.SV8507-D0-001 Rev 2 1-118/10/02
Page 1 and 2: Minnegang CreekFlood Study
Page 3: © Kellogg Brown & Root Pty Ltd, 20
Page 6 and 7: SummaryThis report presents the det
Page 8 and 9: The RatHGL modelling indicated that
Page 10 and 11: FIGURESSectionPageFigure 2-1 Catchm
Page 14 and 15: 2 Catchment DescriptionThe Minnegan
Page 16: Figure 2.1CATCHMENT AND STUDY AREAM
Page 20 and 21: Illawarra Flood Study investigated
Page 23 and 24: The catchment was divided into 64 s
Page 25 and 26: To determine the peak flow from the
Page 27 and 28: 5 Hydraulic Modelling5.1 INTRODUCTI
Page 29: Table 5-1 MIKE 11 river branchesBra
Page 32 and 33: elationship that is determined from
Page 34 and 35: interaction between the numerical m
Page 36 and 37: significantly affected since the ex
Page 38 and 39: Since Points A and B correspond to
Page 41 and 42: 5.9 MODEL SENSITIVITY ANALYSESSensi
Page 43 and 44: 555053.09RANCHBY AVEElevation (m AH
Page 45 and 46: Creek and pass directly over Northc
Page 47: 5.12.4 Overland flow pathsAs discus
Page 50 and 51: Table 6-1 Peak design dischargesBra
Page 52 and 53: 55.050.0PMF Flood Level1% AEP Flood
Page 58 and 59: 1% AEP velocities and flow distribu
Page 60 and 61: 2524.52423.5RL (m)231% AEP velociti
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RL (m)3433.53332.53231.53130.53029.
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Figure 5-6.Table 6-2 Piped drainage
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that handrails above these structur
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flooding within the catchment are n
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35.01% AEP flood level - blocked ca
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20.01% AEP flood level - blocked ca
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Appendix AReferencesBureau of Meteo
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Appendix BGLOSSARYSV8507-DO-001 Rev
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hydraulicshydrographhydrologyMIKE 1
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Appendix CHistorical Flood DataRECO
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Time Rain(mm)Time Rain(mm)Time Rain
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Appendix DRAFTS HYDROLOGIC MODELSV8
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MHE .5359 .3573 12.10 12.10 5.000 1
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Mannings n 0.025 0.025 0.025 0.025
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Mannings n 0.025 0.025 0.025 0.025
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MH94 67.500 15.00 1.500 2.500 .0000
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Appendix EMIKE 11 HYDRAULIC MODELSV
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EXIST ; DENISE2 ; 0.005; 0.133; 100
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22.40; 88.40;23.30; 100.00;25.10; 1
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27.26; 128.96;27.43; 137.64;28.08;
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1; 1.250;0;1.800; 1.250; 0.000; 0.0
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PIPE_10; 0.108; EXIST;57.000; 159.0
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Appendix FMIKE11 RESULTS SUMMARYThi
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BRANCH CHAINAGE PMF 1% AEP 2% AEP 5
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Minnegang Creek Flood Study Report - Wollongong City Council

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