Minnegang Creek Flood Study Report - Wollongong City Council

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The RatHGL modelling indicated that the capacity of the pipe d drainage system islargely restricted by the capacities of the stormwater inlets. Further, in some locations,surcharging of the system occurs due to the inadequate depth of the existingstormwater system.In accordance with Council’s Conduit Blockage Policy, culverts were modelled asfully blocked. The Jane Avenue bridge was modelled with 25% bottom up blockage.Handrails above the culverts and on the bridge were modelled as 100% blocked. Floodprofiles and extents are based on the worst-case blockage scenario as well as clearculverts. Flood profiles were also developed for the case of clear culverts todemonstrate the upstream afflux resulting from blockage of each structure.SV8507-DO-001 Rev 218/10/02iv
CONTENTSSection Page Section PageFOREWORDSUMMARYFIGURESTABLESABBREVIATIONSiiiviviiviii5.3 Extent of modelling 5-165.4 Model construction 5-165.5 Model stability 5-215.6 Boundary conditions 5-215.7 Initial conditions 5-235.8 Calibration and verification 5-245.9 Model sensitivity analyses 5-295.10 Critical storm duration analysis 5-325.11 Hydraulic modelling downstream ofnorthcliffe drive 5-325.12 Modelling of the existing piped drainagesystem 5-331 INTRODUCTION 1-12 CATCHMENT DESCRIPTION 2-23 BACKGROUND 3-74 HYDROLOGIC MODELLING 4-94.1 Introduction 4-94.2 Model selection 4-94.3 Model construction 4-94.4 Rainfall data 4-114.5 Calibration 4-124.6 Model sensitivity analysis 4-134.7 Future development conditions 4-135 HYDRAULIC MODELLING 5-155.1 Introduction 5-155.2 Model selection 5-156 FINDINGS 6-366.1 Results of the mike 11 modelling 6-376.2 Results of the rathgl modelling 6-516.3 Culvert structures 6-526.4 Results downstream of northcliffe drive6-536.5 Impact of council’s conduit blockagepolicy 6-536.6 Future development conditions 6-55APPENDICESABCDEFReferencesGlossaryHistorical flood dataRAFTS hydrological modelMIKE 11 hydraulic modelMIKE 11 results summarySV8507-D0-001 Rev 218/10/02v
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 10 and 11: FIGURESSectionPageFigure 2-1 Catchm
Page 12 and 13: ABBREVIATIONSAEPAHDARIAR&RDCPIFDLEP
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
Page 62 and 63:
RL (m)3433.53332.53231.53130.53029.
Page 64 and 65:
Figure 5-6.Table 6-2 Piped drainage
Page 66 and 67:
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
Page 74 and 75:
Appendix AReferencesBureau of Meteo
Page 76 and 77:
Appendix BGLOSSARYSV8507-DO-001 Rev
Page 78 and 79:
hydraulicshydrographhydrologyMIKE 1
Page 80 and 81:
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
Page 91 and 92:
Mannings n 0.025 0.025 0.025 0.025
Page 93 and 94:
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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