Minnegang Creek Flood Study Report - Wollongong City Council

Minnegang CreekFlood Study

MINNEGANG CREEKFLOOD STUDYFinal ReportPrepared for:WOLLONGONG CITY COUNCIL41 Burelli St, Wollongong NSW 2500Telephone (02) 4227 7111, F ascimile (02) 4227 7277Prepared by:Kellogg Brown & Root Pty LtdABN 91 007 660 317Level 9, 201 Kent Street, Sydney NSW 2000Telephone (02) 9911 0000, Facsimile (02) 9241 2900October 2002SV8507-DO-001 Rev 2

© Kellogg Brown & Root Pty Ltd, 2004Limitations StatementThe sole purpose of this report and the associated services performed by Kellogg Brown & Root Pty Ltd (KBR) is toprepare a Flood Study in accordance with the scope of services set out in the contract between KBR and WollongongCity Council (‘the Client’). That scope of services was defined by the requests of the Client, by the time andbudgetary constraints imposed by the Client, and by the availability of access to the site.KBR derived the data in this report primarily from visual inspections, examination of records in the public domainand interviews with individuals with information about the area. The passage of time, manifestation of latentconditions or impacts of future events may require further exploration at the site and subsequent data analysis, and reevaluationof the findings, observations and conclusions expressed in this report.In preparing this report, KBR has relied upon and presumed accurate certain information (or absence thereof) relativeto the site provided by government officials and authorities, the Client and others identified herein. Except asotherwise stated in the report, KBR has not attempted to verify the accuracy or completeness of any such information.No warranty or guarantee, whether express or implied, is made with respect to the data reported or to the findings,observations and conclusions expressed in this report. Further, such data, findings, observations and conclusions arebased solely upon site conditions and information (including that supplied by the Client) in existence at the time ofthe investigation.This report has been prepared on behalf of and for the exclusive use of the Client, and is subject to and issued inconnection with the provisions of the agreement between KBR and the Client. KBR accepts no liability orresponsibility whatsoever for or in respect of any use of or reliance upon this report by any third party.SV8507-D0-001 Rev 218/10/02

ForewordThe NSW State Government’s Flood Prone Land Policy is directed at providingsolutions to existing flooding problems in developed areas and ensuring that newdevelopment is compatible with the flood hazard and does not create additionalflooding problems in other areas.Under the policy, the management of flood liable land is the responsibility of localgovernment. The State Government subsidises flood mitigation works to alleviateexisting flooding problems and provides specialist technical advice to assist councilsin the discharge of their floodplain management responsibilities.The policy provides for technical and financial support by the State Governmentthrough five sequential stages. These stages are:• Data collection: determines the availability of data and defines data requirements.• Flood Study: determines the nature and extent of the flood risk.• Floodplain Risk Management Study: evaluates management options for thefloodplain in respect of both existing and proposed developments.• Floodplain Risk Management Plan: involves formal adoption by Council of aplan of management for the floodplain.• Implementation of the Plan: includes undertaking property modification andflood mitigation works to protect existing development, implementing appropriateflood response procedures, increasing community awareness and the use of policydocuments such as Local Environmental Plans to ensure development and land useis compatible with the flood hazard.SV8507-DO-001 Rev 218/10/02i

SummaryThis report presents the details and findings of the Flood Study carried out for theMinnegang Creek catchment. The Floodplain Risk Management Study and Plan willbe undertaken following the completion of this Flood Study.Existing flood behaviour within the Minnegang Creek catchment has been determinedbased on hydrologic and hydraulic modelling for the 20%, 5%, 2% and 1% AnnualExceedence Probability (AEP) events, as well as the Probable Maximum Flood (PMF)event. Flood behaviour has been defined in terms of design flows, flood surfaceprofiles, flow velocities, flood extents and flood contours.Hydrologic modelling of the catchment was undertaken using RAFTS v5.1(WP Software, 1996). The hydraulic modelling component of the study wasundertaken using MIKE 11 v3.20 (Danish Hydraulic Institute, 1998), an unsteady statehydraulic model. RatHGL v4.2 (WP Software, 1997) was used to complement theMIKE 11 model in assessing the capacity of the existing piped drainage system in thecatchment.HYDROLOGYThe 90 ha Minnegang Creek catchment was divided into 64 sub-catchments. RAFTSwas used to determine a runoff hydrograph from each of these sub-catchments foreach design storm event. Design storm events were defined using Intensity FrequencyDuration (IFD) data for the Wollongong area. The Probable Maximum Precipitation(PMP) was derived in accordance with Generalised Short - Duration Method asdescribed in Bulletin 53 (Bureau of Meteorology, 1994).Due to the absence of historical streamflow data within the Minnegang Creekcatchment, calibration of the RAFTS model was not possible. Instead, the flows fromthe RAFTS model were compared to estimates made using the Probabilistic RationalMethod (PRM). Design flow rates derived by each method were similar. Anassessment of the sensitivity of the RAFTS model to the adopted parameters foundthat reasonable variations to the adopted parameters would not significantly alter theresults.To assess the effect that future development may have on flooding within thecatchment, land zoning presented in Council’s Local Environmental Plan (LEP)(1990) was considered as part of the study. An increase in developed conditions to themaximum allowable under the provisions of the LEP led to an increase in the totalflow in Minnegang Creek of less than 0.2%. Council’s Urban Consolidation Policydoes not apply to the Minnegang Creek catchment. It was therefore assumed that theeffects of future development on flooding within the catchment are negligible andhence future development conditions were not modelled in the hydraulic modelling ofthe catchment.SV8507-DO-001 Rev 218/10/02ii

HYDRAULICSThe MIKE 11 model included Minnegang Creek, the tributary from Gordon Crescent,the tributary from Melinda Grove, the three minor branches draining the area betweenRanchby Avenue and Hilltop Avenue and the minor branch draining the area betweenCanberra Road and Minnegang Creek. Boundary conditions identified in the modelwere discharges and water levels. The runoff hydrographs from RAFTS were enteredas discharges into the MIKE 11 hydraulic model. The tailwater levels at thedownstream end of the model were derived from the Lake Illawarra Flood Study(Lawson and Treloar, 2000).VERIFICATIONVerification of the combined RAFTS and MIKE 11 model results was undertaken forthe historical event of 17 August 1998. Rainfall data was obtained from the SydneyWater owned gauge located at the Berkeley Sports and Social Club. Runoffhydrographs were generated in the RAFTS model using the historical rainfall datarecorded at five minute increments. These hydrographs were routed through the MIKE11 hydraulic model and the resulting peak water levels were compared to the recordedflood levels for the event.The results of this verification indicated that the MIKE 11 model is accuratelyreproducing the response of the catchment to 17 August 1998 event. However, itshould be noted that this event is considered to have an Average Recurrence Interval(ARI) of approximately 2 years. During the August 1998 flood event, the higherrainfalls were recorded further north of the Minnegang Creek catchment. Ideally,calibration of the hydraulic model would be carried out using a historical event ofsimilar magnitude to the design events (such as the 1% AEP event) to be modelled.This was not possible due to the lack of historical data corresponding to large rainfallevents in the catchment.SENSITIVITYAn assessment of the sensitivity of the MIKE 11 model found that the results for the1% AEP design event did not vary significantly as a result of changes to the modellingparameters. The adopted tailwater level did not significantly affect flood levelsupstream of Northcliffe Drive.CRITICAL STORM DURATIONThe critical storm duration for the catchment, based on the peak flow rates generatedby the RAFTS modelling, was found to be the 2 hour storm for each AEP eventmodelled. This duration was verified by modelling the 1% AEP event for 30, 60 and90 minute durations, as well as the 2, 3 and 6 hour durations in MIKE 11. Thisshowed that the 2 hour storm was leading to the critical flood levels in the catchment.DESIGN EVENTS MODELLEDThe hydraulic modelling of design events was subsequently undertaken for the 20%,5%, 2% and 1% AEP events and the PMF event to determine the flood behaviour forexisting conditions in the catchment. The MIKE 11 modelling has enabled theexisting flood behaviour in the catchment to be described in terms of flood profiles,flood extents and flood surface contours, peak discharges and depth-averagedvelocities.SV8507-DO-001 Rev 218/10/02iii

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

FIGURESSectionPageFigure 2-1 Catchment and study area 2-4Figure 2-2 Zoning boundaries 2-5Figure 2-3 Minnegang Creek and tributaries 2-6Figure 4-1 RAFTS model layout 4-10Figure 5-1 MIKE 11 construction 5-18Figure 5-2 17 August 1998 event flood profile 5-27Figure 5-3 17 August 1998 event flood extents 5-28Figure 5-4 Hydraulic roughness sensitivity 5-30Figure 5-5 Tailwater levels sensitivity 5-31Figure 5-6 RatHGL model layout 5-35Figure 6-1 Design Flood Profiles - Minnegan Branch 6-38Figure 6-2 Design Flood Profiles - Melinda Branch 6-40Figure 6-3 Design Flood Profiles - Lakehts2 Branch 6-41Figure 6-4 1% AEP Flood Contours 6-42Figure 6-5 2% AEP Flood Contours 6-43Figure 6-6 5% AEP Flood Contours 6-44Figure 6-7 20% AEP Flood Contours 6-45Figure 6-8 Velocity and flow distributions - Minnegan 0.402 6-46Figure 6-9 Velocity and flow distributions - Minnegan 0.616 6-47Figure 6-10 Velocity and flow distributions - Minnegan 0.835 6-48Figure 6-11 Velocity and flow distributions - Minnegan 1.545 6-49Figure 6-12 Velocity and flow distributions - Melinda 0.328 6-50Figure 6-13 1% AEP flood profilesLake Heights Road culvert 6-57Figure 6-14 1% AEP flood profilesBarina Park detention basin 6-58Figure 6-15 1% AEP flood profiles - Jane Avenue bridge 6-59Figure 6-16 1% AEP flood profilesNorthcliffe Drive and Illawarra Yacht Club culverts 6-60SV8507-D0-001 Rev 218/10/02vi

TABLESSectionPageTable 4 -1 Adopted losses in RAFTS model(and range of losses considered) 4-11Table 4 -2 Summary of rainfall intensities 4-12Table 4 -3 Comparison of RAFTS and PRM flows (m 3 /s) 4-13Table 5 -1 MIKE 11 river branches 5-17Table 5 -2 Typical Manning’s n values used in the hydraulic model 5-21Table 5 -3 Tailwater levels adopted for hydraulic modelling 5-22Table 5 -4 Recorded flood levels for the 17 August 1998 event 5-25Table 5 -5 Comparison of modelled results withrecorded flood levels for the 17 August 1998 event 5-26Table 5 -6 RatHGL manhole inlet capacities 5-34Table 6 -1 Peak design discharges 6-38Table 6 -2 Piped drainage system capacities 6-52Table 6 -3 Culvert structures 6-52Table 6 -4 Culvert capacities 6-53SV8507-D0-001 Rev 218/10/02vii

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

2 Catchment DescriptionThe Minnegang Creek catchment is located approximately 8.5 km south ofWollongong, in the suburb of Lake Heights. The catchment rises from the northernshore of Lake Illawarra to the intersection of Lake Heights Road and Flagstaff Road.The catchment location is shown in Figure 2-1. The majority of the 90 ha catchment ischaracterised by steep rolling hills. However, the creek is relatively flat for severalhundred metres from the shore of Lake Illawarra.Approximately 80% of the catchment is developed, mostly with low densityresidential housing. The remaining 20% is either recreational or cleared open space.The area is located in the City of Wollongong Local Government Area (LGA) and istherefore subject to the provisions of the City of Wollongong Local EnvironmentalPlan (LEP) 1990 (as amended to 9 March 2001).The majority of land in the catchment is zoned 2(a) - Low Density Residential. BarinaPark and most other areas of open space within the catchment are zoned PublicRecreation, Zone 6(a). On the shores of Lake Illawarra, land is zoned PrivateRecreation, Zone 6(b). The small commercial property on the corner of Buena VistaAvenue and Lake Heights Road is zoned Neighbourhood Business, Zone 3(b). Otherzones that occur within the catchment are Zone 2(b) - Medium density residential,Zone 5(c) - Special uses (Main roads) and Zone 9(b) - Reservation zone (land reservedfor roads). Figure 2-2 shows the zoning of land within the catchment boundaries.The creek system consists of a combination of natural open watercourses and pipeddrains. Minnegang Creek flows from the north west of the catchment to the south eastwhere it discharges into Lake Illawarra. Minnegang Creek has two main tributaries.The first flows from the north of the catchment, follows Melinda Grove and thenpasses under Gilgandra Street, confluencing with Minnegang Creek upstream ofMirrabooka Road. The second tributary commences in the south west, from GordonCrescent and flows under Ranchby Avenue, confluencing with Minnegang Creekupstream of Lake Heights Road. Figure 2-3 shows the location of Minnegang Creekand its tributaries within the catchment.There are also minor branches of Minnegang Creek draining the area between HilltopAvenue and No 30 Ranchby Avenue, the area between Claremont Avenue and No 46Ranchby Avenue and the area between No 7 Canberra Road and Minnegang Creek.Minnegang Creek is approximately 2 km long. The average slope of the creek bed inthe upper catchment is approximately 5%. The lower catchment is flatter, andMinnegang Creek has an average slope of 2% for the final 1 km before it passes underNorthcliffe Drive, to enter Lake Illawarra in the vicinity of Griffin Bay.SV8507-D0-001 Rev 2 2-218/10/02

The upper creek and major contributing drainage systems consist of approximately1 km of natural watercourse and approximately 1.6 km of piped trunk drainage. Thepiped system discharges into the natural watercourse, which flows over the final0.9 km of Minnegang Creek.In some locations, Minnegang Creek and its larger tributaries are piped underresidential properties with little or no provision for overland flow. The properties inthese areas have been identified as having suffered, or at risk of, flood damage. Areasspecifically affected are:• where Minnegang Creek passes under Lake Heights Road and Barina Road• where Minnegang Creek’s tributary passes under Gilgandra Street• where Minnegang Creek exits Barina Park• where Minnegang Creek passes under Mirrabooka Road and Weringa Avenue.SV8507-D0-001 Rev 2 2-318/10/02

Figure 2.1CATCHMENT AND STUDY AREAMinnegang Creek Flood Study

3 BackgroundData collection was an important stage in the preparation of the Flood Study. Councilprovided Halliburton KBR with the following information:• catchment map;• aerial photographs of the catchment from 1982 and 1993;• plans of the catchment with recorded flood levels and photographs from stormevents on 14 December 1985, 23 October 1987, December 1990 and 17 August1998;• rainfall data, at five minutes intervals for the storm event on 17 August 1998 fromthree rain gauges. These gauge stations were: Berkeley B44 (Berkeley Sports andSocial Club), Port Kembla SPS 176 (Foreshore Rd, Port Kembla) and ManlyHydraulics Laboratory Port Kembla gauge;• plans showing proposed works associated with the retrofitting of the detentionbasin within Barina Park;• construction plans for Northcliffe Drive from Griffin St to Margaret St,Warrawong.• Intensity Frequency Duration (IFD) data for Wollongong;• 1:2000 cadastral information for the catchment including cadastral boundaries,zoning, easements, water courses and natural surface contours at 2 m intervals;• a copy of the City of Wollongong Local Environmental Plan 1990 (as amended to9 March 2001);• a copy of the Lake Illawarra Flood Study (June 2000) prepared by Lawson andTreloar for Council;• a copy of Council’s Drainage Design Code (1998); and• a copy of Council’s Blockage Policy (2001).The following information was sourced from the Bureau of Meteorology:• daily rainfall for 23 October 1987 and 14 December 1985 storm events; and• antecedent conditions for July and August 1998 storm events and average rainfallfor these months at Northcliffe Drive, Berkeley.No previous flood studies have been carried out within the Minnegang Creekcatchment. However, Lawson and Treloar Pty Ltd (2000) carried out a flood study ofLake Illawarra, covering a catchment area of approximately 235 km 2 . The LakeSV8507-D0-001 Rev 2 3-718/10/02

Illawarra Flood Study investigated flooding of Lake Illawarra to evaluate peak floodlevels for a range of design rainfall events under existing catchment and lakeconditions. The results for flooding within Lake Illawarra at Griffin Bay have beenused to derive the tailwater levels for the Minnegang Creek catchment.Three surveys of the catchment were carried out as part of the flood study. G.A.Goodman Surveys Pty Ltd completed the first two of these surveys. The first survey,completed in July 2000, comprised three parts:• a detailed survey of the open channel sections of Minnegang Creek, with surveyedcross sections perpendicular to the direction of flow;• a detailed survey of Barina Park; and• identification of pit/culvert locations within the catchment.The second survey, completed in January 2001, provided more details of the pipeddrainage system, including conduit type and size, invert levels and surface levels ofthe manholes and pipe connectivity. Cross sections and weir profiles along theoverland flow paths were also taken to allow the hydraulic modelling of the catchmentto be completed in more detail.The final survey was completed by Council’s surveyors. It provided further groundlevel information for the area of the catchment downstream of Northcliffe Drive. Italso provided definition of the bridge over Minnegang Creek between Denise St andJane Ave. Finally, the survey provided spot ground levels at the locations of recordedhistorical flood levels.Appendix C contains information on the rain gauge locations near the MinnegangCreek catchment, as well as historical rainfall and flood height data that was used inthe preparation of the flood study.SV8507-D0-001 Rev 2 3-818/10/02

4 Hydrologic Modelling4.1 INTRODUCTIONThe first phase of modelling necessary for the determination of flooding behaviourwithin a catchment is the hydrologic component, which defines the relationshipbetween rainfall and runoff. Hydrologic modelling of the Minnegang Creekcatchment was undertaken to develop runoff hydrographs from design rainfall data forinput into the hydraulic model.This section discusses the methodology associated with the hydrologic modelling ofthe Minnegang Creek catchment using the computer-based RAFTS (Runoff Analysisand Flow Training Simulation) v5.1 hydrologic model (WP Software, 1996). Furtherdetails of the RAFTS model developed for the catchment are provided in Appendix D.4.2 MODEL SELECTIONRAFTS is a widely accepted hydrologic model for urban and rural catchments. Itcalculates design discharges for specified AEP events and storm durations byproducing and combining runoff hydrographs from each specified sub-catchment.RAFTS uses empirical rainfall runoff relationships to produce the runoff hydrographs.It is possible to extract local or total flow hydrographs for each sub-catchment. Theexported RAFTS hydrographs were routed through the catchment using the MIKE 11hydraulic model of the catchment, as discussed in Section 5.For most sub-catchments in the model, a local hydrograph was exported for eachevent. However, due to the layout of the hydraulic model, some sub-catchments withinRAFTS are not located on the branches of the hydraulic model. The local hydrographfor these sub-catchments could therefore not be entered directly into the hydraulicmodel. Hence for these sub-catchments the flows were routed in RAFTS using link lagtimes to a nearby sub-catchment, and a total hydrograph exported to MIKE 11.4.3 MODEL CONSTRUCTION4.3.1 Catchment and sub-catchment boundariesThe overall catchment boundary was determined from the map of the MinnegangCreek catchment provid ed by Council. With consideration of the requirements of thehydraulic model, sub-catchment boundaries were determined from the 1:2000 contourand cadastral maps and the 1982 and 1993 aerial photographs of the catchment. Theadopted catchment boundary and RAFTS sub-catchments are shown in Figure 4-1.SV8507-D0-001 Rev 2 4-918/10/02

The catchment was divided into 64 sub-catchments. Each sub-catchment within theRAFTS model was split into a pervious area and an impervious area. The imperviousarea of the sub-catchment was determined by measuring the area of roads anddeveloped area within each sub-catchment. The roads were considered to be 95%impervious and developed areas (largely med ium density residential) to be 40%impervious.4.3.2 Hydraulic roughnessThe hydraulic roughness of each sub-catchment is represented by a Manning’s nvalue. Based on recommendations outlined in the RAFTS User Manual (WPSoftware, 1994), the following roughness values have been adopted for use in themodel:• 0.015 - impervious areas (typical of asphalt or rough concrete surface)• 0.025 - pervious areas (typical of short grass)4.3.3 Rainfall lossesRainfall losses for the catchment were entered into the RAFTS model us ing theinitial/continuing loss method. This requires that an initial loss be estimated tosimulate the initial wetting of the catchment when no runoff is generated. A constantcontinuing loss accounts for infiltration once the initial loss process is com pleted. Inadopting the rainfall loss values for the Minnegang Creek catchment, considerationwas given to the catchment topography, underlying soil types, recommended valuesgiven in Australian Rainfall and Runoff (AR&R) (Institution of Engineers, 1987), theRAFTS User Manual (WP Software, 1994) and previous experience in theWollongong area.Losses were varied between the minimum and maximum values shown in Table 4-1 todetermine the sensitivity of the model to rainfall losses. It was found that the flowswere only affected to a minor amount (

4.4 RAINFALL DATACouncil’s intensity-frequency-duration (IFD) data for the Wollongong area was usedfor storm durations of 30 minutes, 60 minutes, 2 hours, 3 hours and 6 hours. Theintensities for the 90 minute storm events were derived in RAFTS using the IFDcoefficients for Wollongong. Temporal patterns for all storm durations were generatedby RAFTS in accordance with methods described in AR&R (1987). Table 4-2 providesa summary of the rainfall intensities used for the hydrological modelling.Table 4-2 Summary of rainfall intensitiesRainfall intensity (mm/hr)AEP30 minuteduration60 minuteduration90 minuteduration2 hourduration3 hourduration6 hourduration20% 84.0 58.9 46.6 38.9 30.3 19.85% 107.1 76.2 60.5 51.2 40.4 26.92% 124.3 89.0 71.1 60.5 48.0 32.21% 137.2 98.7 79.2 67.5 53.8 36.3PMP 460 340 260 260 210 138The Probable Maximum Precipitation (PMP) was derived in accordance with theGeneralised Short - Duration Method as described in Bulletin 53: The estimation ofProbable Maximum Precipitation in Australia (Bureau of Meteorology, 1994). Thedesign temporal pattern in Bulletin 53 was used in RAFTS for the PMP events.4.5 CALIBRATIONDue to the absence of any streamflow gauging stations within the Minnegang Creekcatchment, it was not possible to calibrate the RAFTS model to match recordeddischarges. However, flood levels at various points in the catchment were availablefor four historical events. Verification of the combined RAFTS hydrologic model andMIKE 11 hydraulic model against historical flood levels is discussed in detail inSection 5.In the absence of calibration data, the Probabilistic Rational Method (PRM) was usedto check the flows obtained from the RAFTS model. The PRM, as detailed in AR&R(1987) is a simple hydrologic method that estimates the peak flow from a catchmentusing the average design rainfall intensity (for a particular critical duration and AEP),the catchment area and a runoff coefficient.The PRM was derived for rural catchments, which means that the imperviouspercentage assumed in the calculation is low. To allow a valid comparison betweenthe RAFTS flows and the PRM flows, the RAFTS model was modified so that eachsub-catchment area was pervious (with 5% imperviousness) to represent theMinnegang Creek catchment in an undeveloped (rural) state.PRM estimates of the flow for the entire catchment were determined for the 1%, 5%and 20% AEP events. These were then compared to the peak flow determined forthese events using RAFTS.SV8507-D0-001 Rev 2 4-1218/10/02

To determine the peak flow from the entire catchment, lag times were added betweeneach node in the RAFTS model. Some links between sub-catchments originallyincluded lag times as discussed in Section 4.2. For the remaining sub-catchments, lagtimes were estimated for this calibration process to be between one and two minutes.The lag times were not calculated more accurately as the routing of hydrographs fromthese sub-catchments was carried out in the hydraulic model. The one and two minutelag estimates compared well to those subsequently calculated in the hydraulicmodelling of the catchment.Table 4-3 shows the comparison between the peak flow from RAFTS and the PRMflows. It shows that the flows from RAFTS compare well with the PRM flows.Table 4-3 Comparison of RAFTS and PRM flows (m 3 /s)AEP RAFTS 1 min lag RAFTS 2 min lag PRM1% 35.7 28.4 34.45% 28.3 22.2 24.820% 21.7 17.2 15.2The time of concentration for PRM calculations as summarised in Table 4-3 was 43minutes. RAFTS flows were calculated for a range of storm durations, ranging from30 minutes to 3 hours. The peak flow in each case resulted from the 2 hour stormevent.4.6 MODEL SENSITIVITY ANALYSISThe robustness of the RAFTS model was checked by considering the flows fordifferent parameter sets. The parameters used in the RAFTS model, such as rainfalllosses, imperviousness and Manning’s n value, were varied to assess the sensitivity ofthe model to the chosen parameters. The sensitivity analyses were carried outassuming a lag time of 1 minute between each sub-catchment, so that total flows ateach sub-catchment and thus for the entire catchment could be considered.The changes in the predicted flow at each sub-catchment were approximately 5% to20%, for the various changes in the model parameters. The model was more sensitiveto changes in parameters for the 20% AEP event than for the 1% AEP event,particularly for changes to the rainfall losses. For the 5% AEP event, flows were up to40% lower than the adopted flows if higher rainfall losses were adopted in the model.However, it is considered that the adopted losses are reasonable for the catchment andthe flows resulting from these losses are conservative.The sensitivity analysis indicates that reasonable variations to the adopted parameterswould not significantly alter the results and thus the parameters discussed inSection 4.3 should be adopted for the modelling. Total flows at each sub-catchmentfrom the sensitivity analyses are shown in Appendix D.4.7 FUTURE DEVELOPMENT CONDITIONSTo assess the effects that future development may have on flooding within thecatchment, land zoning presented in Council’s Local Environmental Plan (1990) wasconsidered. Urban consolidation as defined in Council’s Urban Consolidation PolicySV8507-D0-001 Rev 2 4-1318/10/02

only affects land around specific railway stations and therefore the Minnegang Creekcatchment is not affected by the policy. The effectiveness of any on-site stormwaterdetention (OSD) policies, in relation to future development within the catchment, willbe assessed in the Floodplain Risk Management StudyMost areas within the catchment are fully developed within their respective land zoneentitlements. The large undeveloped area south east of Flagstaff Road and HilltopAvenue is zoned Low Density Residential - Zone 2(a) and hence could be developedin the future. In order to ascertain the impact on existing flooding within thecatchment, the RAFTS model was modified so that the sub-catchments in thiscurrently undeveloped area were considered fully developed. Residentialdevelopment, with an imperviousness of 40%, was assumed for these areas. Existingroads in these sub-catchments were retained with a percentage imperviousness of95%. The resulting modelled flows were then compared to the flows based on existingdevelopment conditions.For storm durations of 90 minutes and 2 hours, the developed conditions led to anincrease of flows in individual sub-catchments of less than 5%, whilst the increase inthe total flow in Minnegang Creek was less than 0.2%. It was therefore assumed thatthe effects of future development on flooding within the catchment are negligible andhence future development conditions were not included in the hydraulic modelling.Hydrographs from RAFTS, at critical locations along Minnegang Creek have beenincluded in Appendix D for both the existing and future development conditions.SV8507-D0-001 Rev 2 4-1418/10/02

5 Hydraulic Modelling5.1 INTRODUCTIONHydraulic modelling of the Minnegang Creek catchment was undertaken to translatethe runoff hydrographs generated by RAFTS into the flood levels, flow distributionsand flow velocities necessary to adequately describe the existing flooding behaviourwithin the catchment.This section discusses the methodology associated with the hydraulic modellingundertaken as part of the study, including model selection, model construction,selection of boundary conditions and verification of the model with historical floodevents.5.2 MODEL SELECTIONThe range of hydraulic models available can be broadly grouped into two categories:steady state and unsteady state. Steady state models, such as HEC-RAS (HydrologicEngineering Centre, 1997), perform hydraulic calculations based on a fixed startingwater level and assume that discharge through the model remains constant at all times.This invariably results in the coincidence of peak flows at a confluence, which islikely to overestimate the true discharge at that point. Unsteady hydraulic models, onthe other hand, allow for the use of time-varying boundary conditions, which forcesthe model to more closely simulate actual conditions in a catchment by accounting forthe timing of peak discharges contained within full runoff hydrographs.For this study, the MIKE 11 v3.20 (Danish Hydraulic Institute, 1998) one dimensionalimplicit finite difference model for unsteady flow computation was selected, primarilyfor its ability to account for the difference in timing of peak discharges in MinnegangCreek and its tributaries. A further advantage of MIKE 11 over a steady state model isits ability to model the effects of dynamic storage, which results in the attenuation of aflood hydrograph as it is routed along a river channel. Dynamic storage refers to thestorage volume inherent along any open channel reach, which is generally small wherechannel cross sections are steep and narrow but can be significant where a moreextensive channel floodplain exists. It is considered that dynamic storage will have asignificant role in the natural attenuation of flows in the lower part of the MinnegangCreek catchment, which further justifies the use of MIKE 11 for this particular study.To complement the hydraulic modelling of the overland flow paths within thecatchment with an assessment of the capacity of the exist ing piped drainage system,RatHGL v4.2 (WP Software, 1997) was used to model the piped drainage system.RatHGL is an urban stormwater piped network analysis and design program thatmodels peak flows, and can be linked with RAFTS for direct import of peak designSV8507-D0-001 Rev 2 5-1518/10/02

flows for the full range of storm frequencies. The modelling of the piped drainagesystem is discussed further in Section 5.12.5.3 EXTENT OF MODELLINGAlthough the RAFTS model was required to cover the entire catchment areacontributing to generation of runoff, the extent of the MIKE 11 model was limited tothose areas requiring detailed investigation as part of the study, including:• Minnegang Creek, from its headwaters upstream of Ranchby Avenue to LakeIllawarra;• The tributary from Gordon Crescent, under Ranchby Avenue and confluencingimmediately upstream of Lake Heights Road;• The tributary from Melinda Grove, under Gilgandra Street and confluencing at thesouthern end of Barina Park;• The three minor branches draining the undeveloped area between Ranchby Avenueand Hilltop Avenue; and• The minor branch draining the area between Canberra Road and Minnegang Creek.In addition to these overland flow paths, two branches of the catchment’s pipeddrainage system were also incorporated into the MIKE 11 model. The first branchruns from the grated inlet pit at the southern end of Barina Park, under MirrabookaRoad and discharges into Minnegang Creek at an outlet downstream of WeringaAvenue. Since this grated inlet pit forms the low -level outlet to the existing detentionbasin in Barina Park, the incorporation of this reach of pipe was necessary so that theoutlet behaviour of the basin could be adequately simulated. The second branchconveys a section of Minnegang Creek from the eastern end of the vacant lot betweenLake Heights Road and Barina Avenue, linking into the first piped drainage branchapproximately 20m downstream of the grated inlet pit in Barina Park.5.4 MODEL CONSTRUCTIONA total of 20 river branches, 137 cross sections, 14 culverts and 14 weirs were used inthe MIKE 11 model to describe the topography of the catchment and existingstructures to a suitable level of detail.Figure 5-1 shows the construction of the MIKE 11 model that represents thecatchment in its existing condition. A full listing of river branches, cross sections,culverts and weirs used in the MIKE 11 model is provided in Appendix E.5.4.1 River branchesRiver branches are used to define the various flow paths in the model. For this study,branches describe three main types of flow path:• overland flow paths• weir flow over roadways with a culvert crossing• a branch of the piped drainage system.The river branches used are listed in Table 5-1.SV8507-D0-001 Rev 2 5-1618/10/02

Table 5-1 MIKE 11 river branchesBranch nameMINNEGANLAKEHTS2MELINDARANCHBY1RANCHBY2RANCHBY3RANCH BY4BARINAKARRABAHGILGANDDENISE1DENISE2DENISE3CANBERRALAKEWEIRNORWEIRILLAWEIRJANEWEIRPIPE_1PIPE_10DescriptionMinnegang Creek, from its headwaters upstream of Ranchby Avenue to LakeIllawarraThe tributary from Gordon Crescent, under Ranchby Avenue and confluencingwith MINNEGAN immediately upstream of Lake Heights RoadThe tributary from Melinda Grove, under Gilgandra Street and confluencingwith MINNEGAN at the southern end of Barina ParkThe minor branch draining the undeveloped area between No. 14 RanchbyAvenue and Hilltop AvenueThe minor branch draining the undeveloped area between No. 30 RanchbyAvenue and Hilltop AvenueThe minor branch draining the undeveloped area between No. 42 RanchbyAvenue and Hilltop AvenueThe minor branch draining the area between No. 51 Ranchby Avenue and theLAKEHTS2 tributaryThe overland flow path along Barina Avenue, which joins Minnegang Creek atthe eastern side of Barina ParkThe overland flow path along Karrabah Crescent, which joins MELINDA at thebottom of Melinda GroveThe overland flow path along Gilgandra Street, which joins MELINDA at thenorthern side of Barina ParkThe overland flow path from Trevor Avenue, across Denise Street andconfluencing with MINNEGANThe overland flow path from Trevor Avenue, joining DENISE1 at Denise StreetThe overland flow path from Denise Street, confluencing with MINNEGANThe overland flow path from Canberra Road, across Denise Street andconfluencing with MINNEGANThe overflow path for flows in excess of the culvert capacity at the MinnegangCreek crossing under Lake Heights RoadThe overflow path for flows in excess of the culvert capacity at the MinnegangCre ek crossing under Northcliffe DriveThe overflow path for flows in excess of the culvert capacity at the MinnegangCreek crossing under the carpark access road adjacent to the Lake IllawarraYacht ClubThe overflow path for flows in excess of the capacity underneath the bridgebetween Jane Avenue and Denise StreetMajor piped stormwater line beginning within Barina Park to outlet downstreamof Weringa AvenueMajor piped stormwater line beginning just downstream of Lake H eights Roadand joining PIPE_1 within Barina ParkSV8507-D0-001 Rev 2 5-1718/10/02

The hydraulic characteristics of each flow path are represented by cross sections andstructures located along each branch in the model.5.4.2 Cross sectionsCross sections through the overland flow system within the Minnegang Creekcatchment were generally in the form of survey strings created by G.A. GoodmanSurveys in accordance with survey briefs provided to Council by Halliburton KBR.This meant that cross sections did not have to be extracted from existing contour data,thus increasing the level of detail of the model.Cross sections within Barina Park were extracted from a full detailed survey of thepark performed by G.A. Goodman Surveys as part of the July 2000 survey. Crosssection locations were determined such that the full extents of the park and variation innatural surface levels were incorporated into the cross sections. This ensured the mostaccurate representation of the detention storage available within the park in the MIKE11 model.Cross sections along the section of piped drainage system are located at manholesconnecting the lengths of pipe. These manholes include gully pits, grated inlet pits,junction pits and headwalls. Invert levels and surface (overflow) levels for eachmanhole were obtained primarily from the January 2001 survey of the catchment.Identification of cross sections in the model is done by way of assigning a chainagecorresponding to the location of a cross section along the branch. Typically, theupstream cross section on a branch was set to Chainage 0.000 (in kilometres), withchainages increasing downstream. Chainages assigned along weir branches were setto the corresponding cross section chainages on the main branch where the weirbranch splits and then rejoins.5.4.3 StructuresCulvertsCulvert details for the Minnegang Creek crossings under Lake Heights Road andNorthcliffe Drive, specifically culvert sizes, lengths and invert levels, were sourcedfrom the two surveys of the catchment. A third culvert, located underneath a carparkaccess road adjacent to the Lake Illawarra Yacht Club, was also incorporated into themodel. The stage/discharge relationship for each culvert is automatically calculatedby MIKE 11 based on the geometry of the culvert and the adjacent cross sections.WeirsCross sections with the potential to act as weirs were identified from a field inspectionby Halliburton KBR carried out in July 2000 and entered into th e MIKE 11 model asbroad-crested weirs. Weir locations generally consist of cross sections along aroadway crown that effectively form a control point for flow, ponding water on oneside of the road until the weir level is exceeded. A weir was also located along theembankment crest of the Barina Park detention basin, which forms the high leveloutlet for the basin. All weirs used in the model were defined as broad-crested weirsand their hydraulic characteristics described in terms of a stage/flow -widthSV8507-D0-001 Rev 2 5-1918/10/02

elationship that is determined from the geometry of the cross section at the weirlocation. MIKE 11 then calculates the appropriate discharge to associate with eachstage of flow based on the stage/flow- width relationship and the adjacent crosssections.BridgeThe concrete pedestrian bridge between Jane Ave and Denise Street was modelled inMIKE 11 as a weir and irregular culvert. The weir was defined as a broad-crestedweir, using a profile along the centre of the bridge structure. The culvert was definedusing the irregular culvert option in MIKE 11, which requires a depth-widthrelationship. This was determined from the survey of the creek carried out byCouncil’s surveyors in December 2001.Link channelsLink channels were used to provide a connection between branches of the pipeddrainage system and the corresponding overland flow path. This function of MIKE 11connects the invert levels of cross sections between the two branches with a shortlength channel. The use of link channels effectively allows interaction between thetwo systems, so that the overland system carries flows in excess of the piped systemcapacity, and the piped system accepts flows from the overland system when andwhere sufficient capacity is available. The geometry of each link channel isindividually specified, and is dependent on the hydraulic characteristics of theinteraction being modelled.5.4.4 Roughness coefficientsOne of the most important parameters used in the hydraulic model is the Manning’s nvalue, which provides a description of the surface roughness or hydraulic resistance toflow. Rather than making a more simplistic distinction between the main channel andoverbank areas, MIKE 11 allows variation of Manning’s n values at any point within across section. This makes it possible to more accurately define the hydrauliccharacteristics of each cross section, rather than estimating an average value for alumped series of different surfaces. This is especially practical in the urbanised areasof the catchment, where a single cross section may incorporate a residential block,roadway sections and grassed areas as well as a creek channel and floodplain.Manning’s n values for each cross section were derived from field inspections of thestudy area, photographs from the detailed survey, recognised hydraulics referencetexts and previous experience on projects of this nature. Typical Manning’s n valuesused in the MIKE 11 model are shown in Table 5-2.The methodology outlined in French (1986) was adopted in order to estimate anappropriate Manning’s n value to characterise the flow behaviour through residentialproperties, which is subject to obstructions and abrupt changes in flow direction over arange of different surfaces. This involves selection of a basic ‘n’ value for a uniform,straight and regular channel, and adjusting this value using correction factors to takeaccount of vegetation, channel irregularity, obstructions and channel alignment.Following this procedure, estimates of ‘n’ for flow paths through residential propertiesranged from 0.09 to 0.15. From this, it was considered that 0.15 was an overlySV8507-D0-001 Rev 2 5-2018/10/02

conservative estimate given the range of other values used in the catchment. A valueof 0.1 was adopted as a reasonable estimate for the Manning’s n roughness in thissituation. This is supported by work on previous studies, including the Upper NararaCreek Flood Study (Kinhill, 1993), that used values ranging between 0.08 and 0.12.Table 5-2 Typical Manning’s n values used in the hydraulic modelDescriptionManning’s n valueRoad and driveway surfaces 0.018Short length grass 0.035Long length grass 0.04 – 0.06Main creek channel 0.04 – 0.07Vegetated overbank areas 0.05 – 0.08Residential blocks (including structures and gardens) 0.1A sensitivity analysis has been undertaken to gauge the impact that the adoptedManning’s n values have on the MIKE 11 results, including the value chosen torepresent the resistance to flow through residential blocks. Further details of thisanalysis are presented in Section 5.95.5 MODEL STABILITYModel stability is usually an issue requiring consideration when dealing with unsteadymodels that simulate time-varying flow behaviour. Instabilities are the result of thesolution scheme failing to balance the complex mathematical equations used by themodel between computation points and/or over the selected computational time step.Selection of an appropriate time step to be used for flow computations is critical in thedevelopment of a stable model. The process must consider not only the desiredresolution of the results and model run time but also the geometry and construction ofthe model and the finite difference solution scheme used by MIKE 11. In order tosatisfy the demands of the model construction, a time step of 0.01 minutes wasadopted. This is an extremely small time step over which to perform calculations,which has ramifications in terms of increased run times. The requirement for a timestep this small is the result of closely spaced cross sections within the model,particularly around culverts and weirs, and the overall steepness of the catchment.However, tolerating this time step, in terms of increased run times, has the advantageof increasing the resolution of the model.The other major source of instabilities in the model were caused by branches dryingout, which causes major problems for the equations in the model which are attemptingto balance the properties of flow between two points. This was dealt with byintroducing a small slot below the invert level of every cross section in the model,which essentially allows each section to retain a small volume of water. A highroughness value within the slot ensures that the conveyance is extremely low andinsignificant compared to the conveyance above the level of the slot.5.6 BOUNDARY CONDITIONSBoundary conditions provide the necessary interface between the numerical hydraulicmodel and the conditions external to the model. They allow MIKE 11 to simulate theSV8507-D0-001 Rev 2 5-2118/10/02

interaction between the numerical model, which would otherwise operate as a closedsystem, and the surrounding environment. Continuing simulation of these interactionscan be achieved in MIKE 11 by the specification of time-varying boundary conditions.In a hydrodynamic modelling situation such as this, boundary conditions are generallyspecified as either water levels to simulate tailwater levels, or discharges to simulaterunoff entering the model.5.6.1 Tailwater levelsFor this study, Lake Illawarra has been adopted as the downstream boundary of theMIKE 11 model. Due to the steepness of the catchment, it is unlikely that backwatereffects caused by elevated lake levels would propagate far up Minnegang Creek,meaning that the flooding behaviour of the majority of the catchment is likely to beinsensitive to the adopted tailwater level. However, it is recognised that flooding ofthe lower part of the catchment, especially the area around Northcliffe Drive, maydisplay some sensitivity to lake levels. For this reason, it was considered appropriateto look at a range of possible tailwater levels rather than adopt a single value, such as amean high water level, for all design events.Tailwater levels were derived from the Lake Illawarra Flood Study (Lawson andTreloar, 2000). For the purposes of this study, a lake level of corresponding AEP tothe flood event in the Minnegang Creek catchment has been adopted. The levelscorrespond to a point located approximately 750m south east of the mouth ofMinnegang Creek within Griffins Bay, and are summarised in Table 5-3.Table 5-3 Tailwater levels adopted for hydraulic modellingAnnual exceedence probabilityLake level (m AHD)20% 1.405% 1.812% 2.031% 2.30PMF 3.24It is appropriate to note that a particular lake level and flood event of correspondingAEP are not necessarily related, and that the design event that contributed to each wasdetermined quite independently of the other. Furthermore, there is likely to be somevariation in the critical storm durations due to the significant difference in contributingcatchment areas. In reality, the determination of a flood level in Lake Illawarracorresponding to a particular flood event in Minnegang Creek is a problem ruled bythe joint probability of the two events occurring at the same time. It could, however,be argued that matching lake level and flood event AEPs leads to an overestimation oflake level (and is therefore conservative) since the peak flood levels in Lake Illawarrawould still be building as the critical storm duration for the Minnegang Creekcatchment is reached. In order to gauge the impact that the adopted tailwater levelshave on the MIKE 11 results, a sensitivity analysis has been undertaken to compareflood levels along the lower reaches of Minnegang Creek. Further details of thisanalysis are presented in Section 5.9.SV8507-D0-001 Rev 2 5-2218/10/02

5.6.2 DischargesMIKE 11 also requires that boundary conditions, in the form of runoff hydrographs,be specified at the upstream extent of all model branches that are not otherwiseconnected at a junction. For this study, additional hydrographs have been specified atappropriate locations within the model in order to increase the definition of the modeland thus more accurately simulate the flooding response of the catchment. Thus, flowhydrographs for local sub-catchments generated by the RAFTS model were inserted atthe corresponding locations within the MIKE 11 model.5.7 INITIAL CONDITIONSInitiating the simulation of a design event in MIKE 11 is not as simple as starting therun and letting water flow into the model via the runoff hydrographs defined in theboundary conditions, since this will result in instabilities arising from the wetting ofpreviously dry branches. This problem is amplified by the fact that runoffhydrographs are spatially distributed throughout the model. This theoretically allowsa dry computation point to exist downstream of a wet point, before the flow has timeto translate down the branch, which introduces further instabilities into the model.In order to avoid these start-up instabilities, it was necessary to use two base flow runsto wet the model and establish a steady state prior to introducing a design event. Thefirst base flow run was used to establish a steady flow through the model. Thisinvolved:• high initial water levels throughout the catchment, sufficient to flood the entirecatchment;• constant discharges of 0.1 m 3 /s in all model branches; and• a time-varying lake level, reducing from the initial high water level down to 1.0mAHD.Reducing the lake level at a controlled rate allowed water to slowly drain out of themodel, avoiding instabilities that result from rapidly increasing or decreasing waterlevels. The conditions at the end of this run were then used as initial conditions to ‘hotstart’ a second base flow run to establish the model tailwater level as the lake levelcorresponding to the AEP of each design event. This involved:• constant discharges of 0.05 m 3 /s in all model branches; and• a time-varying lake level, increasing from 1.0m AHD to the tailwater levelcorresponding to each design event (ranging from 1.40m AHD for the 20% AEPdesign event to 3.24m AHD for the PMF event).A separate run was undertaken for each design event to be modelled, creatingconditions that were then used to “hot start” each event run.When running the design events, it was necessary to modify the input hydrographs atthe upstream extent of all branches in order to maintain the stability of the modelestablished during the base flow runs. To do this, base flows of 0.05 m 3 /s weremaintained in the hydrographs until they were exceeded by flood flows. While earlyflood levels are likely to be elevated by this technique, peak flood levels are notSV8507-D0-001 Rev 2 5-2318/10/02

significantly affected since the excess flows will have drained away by the time thepeak occurs.5.8 CALIBRATION AND VERIFICATIONThe ideal situation for the calibration and verification of any hydraulic model is forrecorded flood levels from historical events to be available at various locations withinthe catchment, along with corresponding gauged peak flows and rainfall data. Thefirst phase of calibration would involve running the rainfall data for one of thesehistorical events through the hydrologic model. Comparison of the resulting runoffhydrographs with recorded gauged flows would enable the appropriate rainfall lossesto be established, such that the excess rainfall depth over the catchment matched therecorded volume of runoff. This would ensure that the total amount of runoff in themodel corresponds to the actual volume of runoff from the rainfall event. The secondphase of calibration would involve routing the runoff hydrographs from the calibratedhydrologic model through the hydraulic model and fine tuning the model parametersuntil the modelled flood levels correspond to the peak levels recorded during thatevent.However, due to the absence of any streamflow gauging stations within theMinnegang Creek catchment, it was not possible to calibrate the hydrologic andhydraulic models in this way. Although recorded flood levels (peak heights) for fourhistorical events (17 August 1998, December 1990, 23 October 1987 and 14December 1985) were available, the lack of gauged flow data places a major limitationon the degree of verification possible. In addition, rainfall data for the storm eventscontributing to the four historical flood events proved difficult to source. Continuousrainfall data (five minute increments) suitable for use in the RAFTS model was onlyavailable for the 17 August 1998 event. The only rainfall data available for the otherthree historical events were daily rainfall totals. Although it would be possible todevelop a temporal pattern to apply to these daily depths, in order to produce a rainfall“event” to model in RAFTS, it was not considered to be appropriate due to the lack ofgauged flow data that could serve to check the validity of the adopted temporalpatterns.5.8.1 Verification with the 17 August 1998 eventAlthough it would be possible to reproduce the recorded flood levels for the 17 August1998 event based on the corresponding rainfall data, there would be no way todetermine whether the appropriate rainfall losses were established in the RAFTSmodel. Thus, fine tuning the MIKE 11 model could simply be compensating for anincorrect volume of runoff in the model. This process would be likely to lead to theadoption of unrealistic parameter values in the MIKE 11 model. Although the modelwould be “calibrated” for this particular event, it would be highly unlikely to simulatethe appropriate catchment response to design events. Accordingly, there would be nophysical basis for using those parameters to estimate the flood behaviour for designevents. For this reason, calibration of the hydrologic and hydraulic models has notbeen undertaken.However, due to the importance of confirming that the MIKE 11 model is at leastproviding a realistic simulation of the catchment response to rainfall, a limitedverification procedure was undertaken for the 17 August 1998 event.SV8507-D0-001 Rev 2 5-2418/10/02

This involved:• generating runoff hydrographs with the RAFTS model using historical rainfall datasourced from Council (the rainfall record for this event and the resultinghydrograph where Minnegang Creek enters Lake Illawarra are shown inAppendix C);• routing the hydrographs through the MIKE 11 model; and• comparing the resulting peak water levels with the recorded flood levels.Peak flood levels for this event were recorded at four locations within the catchment,all of which lie along Minnegang Creek. Table 5-4 lists the recorded flood levels andprovides a description of each location.Table 5-4 Recorded flood levels for the 17 August 1998 eventPoint Location Peak water level (m AHD)A Immediately upstream of the Lake Heights Road culvert 29.58BAt the boundary of No. 68 Barina Avenue and No. 71 LakeHeights RoadC At the boundary of No. 63 Mirrabooka Road and No. 94Weringa Avenue27.6819.79D Behind the rear boundary of No. 61 Denise Street 4.93The tailwater level in the MIKE 11 model was set at 1.2m for this verification basedon the level of Lake Illawarra in August 1998 as recorded in the Lake Illawarra FloodStudy (Lawson and Treloar, 2000).5.8.2 Limitations of the procedureIt is important to realise the limitations of this procedure, as described in the previoussection, and the way in which the assumptions that are inherent in the development ofthe hydraulic model affect the comparison. The issue of blockage introducesadditional complexity to the procedure. The MIKE 11 modelling assumes that allflow paths are clear of debris and, while the partial or full blockage of culverts can bemodelled, for this exercise all culverts were treated as unblocked since it is difficult topredict the degree of blockage likely to occur during any given rainfall event.It is also relevant to note the relative magnitude of the 17 August 1998 event, whichwas considered to have an Average Recurrence Interval (ARI) of approximately2 years according to an analysis performed by AWT Environmental MeasurementServices. When developing a hydraulic model with the intention of simulating largeflood events (such as the 1% AEP event and PMF event to be simulated for thisstudy), it is desirable to be able to calibrate or verify the model with a historical eventof similar magnitude. This would ensure that the fu ll range of stages within each crosssection that will be flooded during the design events is subject to the verification,rather that just the lower stages. Unfortunately, this was not possible due to the lackof historical data corresponding to large rainfall events within the catchment.5.8.3 Results of the procedureThe results of the verification procedure are presented in Table 5-5.SV8507-D0-001 Rev 2 5-2518/10/02

Since Points A and B correspond to cross section locations in the MIKE 11 model,flood levels for these points have been determined directly from the model output.Flood levels for Points C and D have been determined by interpolation between crosssections in the model, taking into account the ground surface level at Points C and D.Table 5-5 Comparison of modelled results with recorded flood levels for the 17 August1998 eventPointRecorded peak water level(m AHD)Modelled peak water level(m AHD)Difference(m)A 29.58 29.34 -0.24B 27.68 27.99 +0.31C 19.79 19.73 -0.06D 4.93 4.99 -0.06The flood profile for Minnegang Creek obtained from the MIKE 11 model for the 17August 1998 event is shown in Figure 5-2. The recorded flood levels for the event arealso shown on Figure 5-2. The flood extents for the 17 August 1998 event are shownin Figure 5-3.5.8.4 Discussion of resultsThe results at Points A and B, where MIKE 11 has predicted a lower flood level atPoint A but a higher level at Point B, suggest that the culvert at Lake Heights Roadcould have been partially blocked during the 17 August 1998 event. Partial blockagewould result in afflux upstream of the culvert, elevating the flood level at Point A.Partial blockage would also attenuate the flow downstream of the culvert, resulting ina lower flood level at Point B. As highlighted earlier, full or partial blockage of theculverts has not been considered for this procedure due to the difficulty in predictingthe degree of blockage. Therefore, if there was some blockage of the culverts duringthe historical event, the model will predict a flood level lower than the recorded peaklevel at Point A and higher than the recorded peak level at Point B.Points C and D lie between model cross sections. Therefore, the flood levels at thesepoints have been interpolated. Interpolation was based on the depth of water atadjacent cross sections. However the interpolation may account for some of thediscrepancy between the modelled and recorded flood levels at these two locations.5.8.5 Summary of the verificationThe verification procedure outlined above has served to confirm that the MIKE 11model, constructed to represent existing conditions in the catchment, is appropriatelysimulating the response of the catchment to the 17 August 1998 event.The differences between the recorded and modelled flood levels can be explained by:• interpolation of modelled levels between surveyed cross sections; or• blockage scenarios, which could reasonably have occurred during the 1998 event.It should be noted that the implications of culvert blockage in the catchment wasaddressed in accordance with Council’s Conduit Blockage Policy during themodelling of design events in the catchment.SV8507-D0-001 Rev 2 5-2618/10/02

5553.259Elevation (m AHD)5045403530252053.0947.72 48.06847.62 RANCHBY 47.753 AVE42.10241.9540.30139.8438.95938.4435.26134.7732.1931.8030.54630.2329.34129.3429.5827.3426.93LAKE HEIGHTS CULVERT28.01526.3027.99727.98927.6825.7725.4128.02127.7827.92627.5827.51926.98BARINA AVE27.15526.9826.44625.7926.44624.4026.44624.15BARINA PARK DETENTION BASINEMBANKMENT26.44626.3326.5326.3322.08221.58MIRRABOOKA RD20.91220.6620.8220.6119.7919.0119.27615-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Chainage (km)35Flood level30Invert levelChainageElevation (m AHD)252015105019.2519.01WERINGA AVE17.33617.0616.82216.7113.73412.8013.52812.8010.82410.0710.5189.3610.0868.71JANE AVE BRIDGE9.9029.0768.548.548.4577.508.3617.476.1995.245.6294.84-51.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.14.8993.884.9853.954.934.2753.223.6322.653.1381.982.5911.612.4580.882.3021.08Recorded flood level2.2090.60NORTHCLIFFE DR CULVERT2.2010.402.2010.550.57 2.196ILLAWARRA YACHT CLUB CULVERT0.45 2.1851.2640.40Chainage (km)Figure 5-217 AUGUST 1998 EVENT FLOOD PROFILEMINNEGAN BRANCHMinnegang Creek Flood Study

5.9 MODEL SENSITIVITY ANALYSESSensitivity analyses were undertaken as part of the modelling process in order togauge the impact of the adopted hydraulic roughness parameters and tailwater levelson the flood levels predicted by the MIKE 11 model.5.9.1 Hydraulic roughnessHydraulic roughness, in terms of Manning’s n values, is specified in MIKE 11 in twoways. Firstly, a global roughness factor is set as a default value, which applies to allcross sections in the model. This can then be modified at any point on any crosssection by specifying a relative resistance factor. The MIKE 11 model developed forthis study is based on a global roughness factor of 0.01, which allows the requiredrelative resistances to be determined quite easily. In order to carry out a sensitivityanalysis on the hydraulic roughness, the global roughness parameter was varied whilethe relative resistance factors remained unchanged. This shows the effect of varyingthe roughness at all cross sections in the model.Figure 5-4 shows the results of this analysis on the modelled 1% AEP flood levels inMinnegang Creek, for global roughness values of 0.007 (70% of the base value) and0.02 (200% of the base value). As expected, the former scenario resulted in a decreasein flood levels, although this attenuating effect was small and limited to those sectionsof Minnegang Creek confined to a formalised channel and relatively unaffected byhydraulic structures. The latter scenario resulted in a significant increase in floodlevels, however, again this was limited to those sections of the creek confined to aformalised channel.Although the results of this analysis serve to illustrate that there is a moderate degreeof sensitivity to the adopted roughness values, the original estimates of the Manning’sn values are considered appropriate for the Minnegang Creek catchment based onprevious experience on projects of this nature. The results of the verificationprocedure also indicate that global roughness values are appropriate.The results of the analysis also demonstrate that localised sections of increasedhydraulic roughness, which could be caused by obstructions to the flow, have thepotential to significantly elevate flood levels in the catchment. This is to be expectedand should be given due consideration in the course of developing floodplainmanagement options for the catchment.In addition to checking the sensitivity of the model to variations in the globalroughness, the value adopted to represent the roughness of residential properties wasvaried while keeping the global roughness constant. This revealed that adopting themore conservative value of 0.15 had little impact on resulting flood levels, whichfurther justified the use of what was considered a more reasonable value of 0.1.5.9.2 Tailwater levelsA separate sensitivity analysis was undertaken to determine the impact of the adoptedtailwater level in Lake Illawarra on the modelled flood levels in Minnegang Creek forthe 1% AEP design event. The tailwater levels used for the comparison were the 50%AEP flood level of 1.11m AHD and the PMF flood level of 3.24m AHD. Figure 5-5shows the results of the analysis.SV8507-D0-001 Rev 2 5-2918/10/02

555053.09RANCHBY AVEElevation (m AHD)4540353047.7247.6241.9539.8438.4434.7731.8030.23LAKE HEIGHTS CULVERTBARINA AVEBARINA PARK DETENTIONBASIN EMBANKMENTMIRRABOOKA RD2527.3426.9326.3025.7725.4127.7827.5826.9826.9825.7924.4024.1526.6126.8126.612021.5820.6620.6119.0115-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Chainage (km)Elevation (m AHD)3530252015105019.01WERINGA AVE17.0616.7112.8012.8010.079.368.71JANE AVE BRIDGE8.548.547.507.475.244.843.883.222.651.981.610.881.081% AEP flood levelGlobal roughness: 0.02Global roughness: 0.007U/s of properties: n=0.15Invert levelChainage0.60NORTHCLIFFE DR CULVERT0.400.550.57ILLAWARRA YACHT CLUB CULVERT0.450.40-0.05-51.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1Chainage (km)Figure 5-4HYDRAULIC ROUGHNESS SENSITIVITYMINNEGAN BRANCHMinnegang Creek Flood Study

555053.09RANCHBY AVEElevation (m AHD)4540353047.7247.6241.9539.8438.4434.7731.80LAKE HEIGHTS CULVERT30.23BARINA AVEBARINA PARK DETENTIONBASIN EMBANKMENTMIRRABOOKA RD2527.3426.9326.3025.7725.4127.7827.5826.9826.9825.7924.4024.1526.6126.8126.612021.5820.6620.6119.0115-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Chainage (km)35Base caseElevation (m AHD)3025201510519.01WERINGA AVE17.0616.7112.8012.8010.079.368.71JANE AVE BRIDGE8.548.547.507.47PMF tailwater level50% AEP tailwater levelInvert levelChainageNORTHCLIFFE DR CULVERTILLAWARRA YACHT CLUB CULVERT05.244.843.883.222.651.981.610.881.080.600.400.550.570.450.40-0.05-51.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1Chainage (km)Figure 5-5TAILWATER LEVELS SENSITIVITYMINNEGAN BRANCHMinnegang Creek Flood Study

The results show that the adopted tailwater level has very little effect on floodingwithin the catchment. Impacts are limited to the lower reaches of Minnegang Creekwhere the lake level encroaches on cross sections before the rainfall event hastranslated downstream.As discussed previously in Section 5.6.1, the use of tailwater levels represented byflood levels in Lake Illawarra of a corresponding AEP to the design rainfall event inthe Minnegang Creek catchment is a conservative approach. As shown by thesensitivity analysis, the major implications of overestimating the tailwater level for thecatchment are in terms of predicting increased flood levels in the lower part of thecatchment. This is especially true over the region bounded by Northcliffe Drive andLake Illawarra. The hydraulic modelling of this particular region is discussed infurther detail in Section 5.11, in terms of the limitations of the MIKE 11 model, andthe interpretation of results for this section of the catchment.5.10 CRITICAL STORM DURATION ANALYSISThe critical storm duration for the catchment, based on the peak flow rates generatedby the RAFTS modelling, was found to be the 2 hours for each flood event modelled.In order to verify the RAFTS result, since the critical storm duration is moreappropriately determined from a comparison of peak flood levels in the catchment, thestorm durations modelled in RAFTS were also modelled in MIKE 11. Accordingly,the 30 minute, 60 minute, 90 minute, 2 hour, 3 hour and 6 hour storm durations for the1% AEP event were modelled. The subsequent analysis of the results showed that the2 hour storm duration was generating the critical flood levels in the catchment.This is considered a reasonably long critical duration given the size of the MinnegangCreek catchment. However, this can be attributed to the design rainfall temporalpatterns in AR&R (IEAust 1987), which often lead to a critical duration of 2 hours forsmall catchments.The 2 hour duration was adopted as the design storm duration for the modelling of allflood events. Thus, the findings presented in Section 6 reflect the results from themodelling of the 2 hour storm for all flood events.5.11 HYDRAULIC MODELLING DOWNSTREAM OF NORTHCLIFFE DRIVEThe accuracy of the hydraulic modelling downstream of Northcliffe Drive has beenaffected by the complexity of flow behaviour in this area.Ground surface levels along Northcliffe Drive and within the Illawarra Yacht Clubcarpark are very flat and fall away towards the east. Once flood levels in MinnegangCreek overtop the Northcliffe Drive culvert, some of the flow will continue southfollowing the alignment of Minnegang Creek. The remaining flow will follow thesurface grade of Northcliffe Drive eastward to the low point in Howard Fowles Park.Here, flows from Minnegang Creek combine with those from the unnamed creek tothe east of the Park. Without extending the hydraulic and hydrologic analysis toinclude this adjacent catchment, which is beyond the scope of this study, it is notpossible to accurately determine flood levels in this area.As flows build toward the peak discharge associated with the design storm events, themajority of the higher flood flows will generally follow the alignment of MinnegangSV8507-D0-001 Rev 2 5-3218/10/02

Creek and pass directly over Northcliffe Drive, re-entering the creek immediatelydownstream of the road. This results in two-dimensional flood behaviour, creating aflood surface that is not horizontal as flows diverge and either travel eastwardstowards the low point along Northcliffe Drive or continue south along MinnegangCreek.One-dimensional models such as MIKE 11 describe the water surface level at eachcross section by computation of a horizontal surface. Cross section extents shouldtherefore be minimised to help maintain an approximately horizontal water surface.However, the flat topography sloping away from Minnegang Creek would require themodel cross sections in this area to be extended into the adjacent catchment to containthe predicted flo od levels.These conflicting requirements create a problem as the horizontal surface computedby MIKE 11 to describe the water surface level at each cross section needs to be fullycontained within the extent of the cross section. If this does not occur, and theiterations begin to calculate a water level that exceeds the natural surface level at oneor both of the cross section extents, MIKE 11 will automatically enclose the crosssection with a vertical extension. The modelled cross sections have been finished atthe extent of the surveyed cross sections as a compromise between the conflictingrequirements referred to above.For the above reasons, the flood extents in the area downstream of Northcliffe Driveas presented in Section 6 should be viewed with caution. Flooding in this area can alsobe attributed to flood events in Lake Illawarra. Thus the results presented in the LakeIllawarra Flood Study (Lawson and Treloar, 2000) should also be used inunderstanding flooding mechanisms in this part of the catchment.5.12 MODELLING OF THE EXISTING PIPED DRAINAGE SYSTEMRatHGL was used to determine the capacity of the existing piped drainage system inthe catchment, as the full extent of the system was not modelled in MIKE 11. Thepiped section of Minnegang Creek was modelled in RatHGL from its upstream extent,between Lake Heights Rd and Barina Ave, to its outlet, downstream of Weringa Ave.All branches of the system joining this piped section of Minnegang Creek were alsomodelled.SV8507-D0-001 Rev 2 5-3318/10/02

Figure 5-6 shows the extent of the stormwater system modelled in RatHGL.RatHGL models peak flows at a point for a given storm frequency. The stormwaterpipe system was modelled for the 1%, 2%, 5%, 20%, 50% and 100% AEP designevents. The peak local flow in each subcatchment for each of these events wasdetermined from the RAFTS hydrologic model and entered into the RatHGL model.The peak total flow for Minnegang Creek upstream of the piped system was entered asthe peak flow at the upstream end of the piped drainage system.5.12.1 Hydraulic lossesThe configuration of the pipes entering each pit was determined from the survey of thepiped system. Pit losses were generally assigned using standard pit configurationspresented in RatHGL, which are based on pit loss calculations by Hare and Missouri(WP Software, 1996). For non-standard configurations, such as pits with three inletpipes, pit losses were calculated using the “generalised manhole loss equation” optionin RatHGL. The loss is evaluated as per Hare/O’Loughlin’s equation for generalisedconnectivity at a manhole (WP Software, 1996). Losses were also specified manuallyfor the headwall at the upstream end of the Minnegang branch, based on an entranceloss coefficient (k e ) of 0.5 (Concrete Pipe Association of Australasia, 1991).To estimate friction loss in the pipes, a Colebrook White pipe roughness of 0.6mmwas used to represent the concrete pipes in all links. This is a conservative figure,representative of a pipe network in poor condition. RatHGL uses the Darcy-WeisbachFormula to calculate the head loss in each pipe resulting from friction losses(WP Software, 1996). For the pipe downstream of the grated pit in Barina Park, aninter-nodal loss was also specified in RatHGL to model the effect of the orifice platewithin the pipe at this location.5.12.2 Inlet capacityEach manhole and junction in the model was assigned a constant inlet capacity, aslisted in Table 5-6.Table 5-6 RatHGL manhole inlet capacitiesInlet typeRatHGL Inlet Capacity (m 3 /sec)Kerb inlet 0.1Kerb and grate inlet 0.15Grated sag inlet 0.2Concrete/steel cover 0.0Junction pit 0.0The initial results of the RatHGL modelling indicated that the capacity of most of thepiped drainage system is restricted by the capacities of the stormwater inlets.5.12.3 Pipe capacityTo determine the capacity of the pipes, the stormwater pits in the system wereassumed to have an unlimited inlet capacity. The results from the RatHGL model arediscussed in Section 6.2.SV8507-D0-001 Rev 2 5-3418/10/02

5.12.4 Overland flow pathsAs discussed in Section 6.2, the capacity of the piped system is inadequate in manylocations. In these locations flow in excess of the pipe capacity travels along overlandflow paths until the next inlet to the piped drainage system is reached. Flow then eitherenters the system, if there is sufficient capacity at this location or will continueoverland.These overland flow paths were included in the MIKE 11 model in most areas of thecatchment. Roads in the catchment are likely to act as other flow paths. In theselocations, flow in excess of the capacity of the piped system will be contained withinthe kerb and gutters along the road. These flows will continue within the road until thelow point of the road is reached. Flows will then overtop the kerb and follow overlandflow paths between properties or along drainage easements through the catchment toMinnegang Creek.SV8507-D0-001 Rev 2 5-3518/10/02

6 Findings6.1 RESULTS OF THE MIKE 11 MODELLINGFlood profiles for the 20%, 5%, 2% and 1% AEP events and the PMF event are shownin Figure 6-1 to Figure 6-3. A summary of the flood levels obtained at each crosssection for each event is tabulated in Appendix F.Flood surface contours for the 1%, 2%, 5% and 20% AEP events are shown in Figures6-4, 6-5, 6-6 and 6-7 respectively. Flows that are fully contained within roads havenot been shown on the flood extents.These figures reflect the results of modelling undertaken in line with Council’sConduit Blockage policy. Further discussion of the impact of the Conduit Blockagepolicy is presented in Section 6.5.It should be noted that in some locations there are discrepancies between the predictedflood levels and the natural surface contours. These discrepancies can be attributed tothe fact that two different data sources have been used. The predicted flood levels arebased on the three detailed surveys of the catchment, as described in Section 3,whereas the natural surface contours are derived from the topographic map and aerialphotography of the catchment. The natural surface contours from the maps areexpected to be accurate to within ±1.0 m in the vertical plane. Where conflicts werefound to occur, the surveyed data was used in preference to the natural surfacecontours.6.1.1 DischargesPeak discharges at various locations throughout the catchment, for the range of designevents modelled, are presented in Table 6-1. Refer to Figure 5-1 for chainagelocations. A more detailed summary of the modelled discharges is contained inAppendix F. Discharges listed in Table 6-1 and Appendix F result from the applicationof the Blockage Policy to all structures, which creates a worst case scenario forflooding in the catchment.It should be noted that the attenuation in flows downstream of Northcliffe Drive, asdemonstrated by the difference in peak discharges between MINNEGAN 1.782 and2.042, is a result of the constrictions presented to flow by the culverts within theIllawarra Yacht Club carpark and the Northcliffe Drive culvert. Further discussion ofthe modelled results downstream of Northcliffe Drive is provided in Section 6.4.SV8507-D0-001 Rev 2 6-3718/10/02

Table 6-1 Peak design dischargesBranchChainagePeak discharge (m 3 /s)20% AEP 5% AEP 2% AEP 1% AEP PMFMINNEGAN 0.428 5.2 6.6 7.3 8.2 15.1MINNEGAN 0.808* 7.2 15.1 19.3 23.5 51.4MINNEGAN 1.178 8.2 15.4 20.5 26.2 68.0MINNEGAN 1.782 9.7 16.8 22.2 27.4 82.0MINNEGAN 2.042 9.4 16.5 21.7 26.8 85.5LAKEHTS2 0.439 2.2 3.0 3.4 3.8 7.1MELINDA 0.356 2.9 3.7 4.0 4.5 8.3* Note that MINNEGAN 0.808 is located along the spillway of the detention basin in Barina Park, so thatthe discharge at this point represents flow overtopping the embankment.6.1.2 VelocitiesThe velocities of the flood flows are required when determining hazard categories foreach design event. MIKE 11 produces depth-averaged velocities, based on a simpleflow divided by cross sectional area relationship. The average velocities for each crosssection for each design event are tabulated in Appendix F.In the upper parts of the catchment, where the flow is largely contained within thechannel, and there is no significant flow in overbank areas of the creek, the averagevelocity is representative of velocities ac ross the cross section. Where flow does spillout of the channel into overbank areas, there is a greater range of velocities within thecross section. The range of velocities should be considered when determining hazards.At representative cross sections, the distribution of the flow across the width of thecross section has been calculated. Figures 6-8 to 6-12 show indicative velocities andpercentage of flow between nodal points at each of these cross section locations. It canbe seen that at all these locations, the majority of the flow is contained within the mainchannel. Velocities are highest within this channel area and are reduced due to edgeeffects at the outermost extents of the flow.SV8507-D0-001 Rev 2 6-3818/10/02

55Elevation (m AHD)50454035302553.0947.7247.62 RANCHBY AVE41.9539.8438.4434.7731.8030.2327.3426.93LAKE HEIGHTS CULVERT26.3025.7725.4127.7827.5826.98BARINA AVE26.9825.7924.4024.15BARINA PARK DETENTIONBASIN EMBANKMENT26.3326.5326.33MIRRABOOKA RD2021.5820.6620.6119.0115-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0Chainage (km)Elevation (m AHD)35302520151050WERINGA AVE19.0117.0616.7112.8012.8010.079.368.71JANE AVE BRIDGE8.548.547.507.475.244.84-51.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.13.883.222.651.981.610.881.08PMF Flood Level1% AEP Flood Level2% AEP Flood Level5% AEP Flood Level20% AEP Flood LevelInvert levelChainage0.60NORTHCLIFFE DR CULVERT0.400.55ILLAWARRA 0.57 YACHT CLUB CULVERT0.450.40-0.05Chainage (km)Figure 6-1DESIGN FLOOD PROFILESMINNEGAN BRANCHMinnegang Creek Flood Study

55.050.0PMF Flood Level1% AEP Flood Level2% AEP Flood Level5% AEP Flood Level20% AEP Flood LevelInvert levelChainage24.1544.7824.8740.7026.4940.7828.5029.9131.4031.2433.5550.0645.0KARRABAH CRESElevation (m AHD)40.00.0000.0450.1020.1170.2120.2740.2820.3280.3840.4270.4670.514GILGANDRA ST35.030.025.020.0-0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6Chainage (km)Figure 6-2DESIGN FLOOD PROFILESMELINDA BRANCHMinnegang Creek Flood Study

55.050.0PMF Flood Level1% AEP Flood Level2% AEP Flood Level5% AEP Flood Level20% AEP Flood LevelInvert levelChainage27.3433.4641.0337.0749.0145.040.0Elevation (m AHD)35.035.6230.030.7525.020.00.0000.1360.2430.2890.3450.4150.463-0.1 0.0 0.1 0.2 0.3 0.4 0.5Chainage (km)Figure 6-3DESIGN FLOOD PROFILESLAKEHTS2 BRANCHMinnegang Creek Flood Study

1% AEP velocities and flow distribution2% AEP velocities and flow distribution353534.534.5RL (m)3433.5331.3 m/s6%2.3 m/s81%1.5 m/s12%RL (m)3433.5331.2 m/s6%2.2 m/s82%1.4 m/s12%32.532.5323231.531.531-10 -5 0 5 10 15 20 25Offset (m)31-10 -5 0 5 10 15 20 25Offset (m)5% AEP velocities and flow distribution20% AEP velocities and flow distributionRL (m)3534.53433.53332.51.2 m/s5%2.1 m/s83%1.4 m/s12%RL (m)3534.53433.53332.51.5 m/sLowHazard8%1.HighHazard2.1 m/s81%1.1 m/s5%LowHazard1.3 m/s11%1.9 m/s85%1.3 m/s11%323231.531.531-10 -5 0 5 10 15 20 25Offset (m)31-10 -5 0 5 10 15 20 25Offset (m)LowHazardHighHazardLowHazardFigure 6-8VELOCITY AND FLOW DISTRIBUTIONSMINNEGAN 0.402Minnegang Creek Flood Study

1% AEP velocities and flow distribution2% AEP velocities and flow distribution3030RL (m)29.52928.50.7 m/s29%1.1 m/s68%0.8 m/s3%RL (m)29.52928.50.7 m/s29%1.1 m/s68%0.8 m/s3%282827.527.52735 45 55 65 75 85Offset (m)2735 45 55 65 75 85Offset (m)305% AEP velocities and flow distribution3020% AEP velocities and flow distribution29.529.5RL (m)2928.50.7 m/s26%1.0 m/s71%0.7 m/s3%RL (m)2928.50.5 m/s21%0.9 m/s77%0.6 m/s3%282827.527.52735 45 55 65 75 85Offset (m)2735 45 55 65 75 85Offset (m)Figure 6-9VELOCITY AND FLOW DISTRIBUTIONSMINNEGAN 0.616Minnegang Creek Flood Study

2524.52423.5RL (m)231% AEP velocities and flow distribution0.5 m/s 1.0 m/s 1.1 m/s 1.4 m/s 1.0 m/s3% 21% 26% 26% 24%22.52221.52120.52020 30 40 50 60 70 80 90 100 110Offset (m)RL (m)2% AEP velocities and flow distribution2524.52423.50.5 m/s 0.9 m/s 1.0 m/s 1.3 m/s 1.0 m/s2% 20% 26% 28% 23%2322.52221.52120.52020 30 40 50 60 70 80 90 100 110Offset (m)5% AEP velocities and flow distribution20% AEP velocities and flow distribution2524.52524.5RL (m)2423.52322.5220.4 m/s1%0.8 m/s 1.0 m/s 1.2 m/s 1.0 m/s19% 27% 30% 23%RL (m)2423.52322.5220.6 m/s 0.9 m/s 1.3 m/s 1.1 m/s8% 21% 41% 30%21.521.5212120.52020 30 40 50 60 70 80 90 100 110Offset (m)20.52020 30 40 50 60 70 80 90 100 110Offset (m)Figure 6-10VELOCITY AND FLOW DISTRIBUTIONSMINNEGAN 0.835Minnegang Creek Flood Study

1% AEP velocities and flow distribution2% AEP velocities and flow distribution14141212RL (m)10860.8 m/s1%2.1 m/s39%2.1 m/s57%1.1 m/s3%RL (m)10860.7 m/s1%2.0 m/s39%2.0 m/s58%1.1 m/s2%442200 5 10 15 20 25 30 35Offset (m)00 5 10 15 20 25 30 35Offset (m)5% AEP velocities and flow distribution20% AEP velocities and flow distribution14141212RL (m)10861.9 m/s39%2.0 m/s59%1.0 m/s2%RL (m)10861.9 m/s38%2.0 m/s61%442200 5 10 15 20 25 30 35Offset (m)00 5 10 15 20 25 30 35Offset (m)Note: FRP - Flood Risk Precinct (see Section 6.1.2)Figure 6-11VELOCITY AND FLOW DISTRIBUTIONSMINNEGAN 1.545Minnegang Creek Flood Study

RL (m)3433.53332.53231.53130.53029.5291.0 m/s2%1% AEP velocities and flow distribution1.4 m/s43%2.0 m/s44%1.1 m/s14%40 50 60 70 80 90 100Offset (m)RL (m)3433.53332.53231.53130.53029.5290.9 m/s2%2% AEP velocities and flow distribution1.4 m/s43%1.6 m/s45%1.1 m/s14%40 50 60 70 80 90 100Offset (m)5% AEP velocities and flow distribution20% AEP velocities and flow distribution343433.533.53333RL (m)32.53231.5310.9 m/s2%1.4 m/s45%1.5 m/s45%1.1 m/s13%RL (m)32.53231.5311.4 m/s41%1.7 m/s48%1.1 m/s11%30.530.5303029.529.52940 50 60 70 80 90 100Offset (m)2940 50 60 70 80 90 100Offset (m)Figure 6-12VELOCITY AND FLOW DISTRIBUTIONSMELINDA 0.328Minnegang Creek Flood Study

6.2 RESULTS OF THE RATHGL MODELLINGThe RatHGL modelling indicates that the capacity of most of the piped drainagesystem is restricted by the capacities of the stormwater inlets.To determine the capacity of the pipes, the stormwater pits in the system wereassumed to have an unlimited inlet capacity. The capacity of the piped drainagesystem, assuming the inlet capacities of the system were not limiting, is presented inTable 6-2. The layout and naming of the pipe system is shown inSV8507-D0-001 Rev 2 6-5118/10/02

Figure 5-6.Table 6-2 Piped drainage system capacitiesPipe branch Pipe Diameter (m) Capacity (m 3 /s) Capacity in ARIPipe 1 0.450 0.6 2 yearsPipe 1 0.600 1.4 2 yearsPipe 1 0.900 0.9 1 yearPipe 1 1.350 3.7 1 yearPipe 2 0.450 0.6 2 yearsPipe 3 0.375 0.4 1 yearPipe 4 0.375 0.6 100 yearsPipe 5 0.375 0.5 5 yearsPipe 6 0.375 0.04 1 yearPipe 7 0.375 0.1 50 yearsPipe 8 0.375 1.0 2 yearsPipe 8 0.600 0.6 2 yearsPipe 8 0.675 1.8 5 yearsPipe 9 0.375 0.7 20 yearsPipe 10 1.200 1.6 1 yearPipe 11 0.375 0.5 5 yearsPipe 12 0.375 0.3 1 yearPipe 13 0.375 0.3 2 yearsPipe 14 0.375 0.05 1 yearPipe 15 0.375 0.3 100 yearsPipe 16 0.375 0.3 20 yearsIn some locations, surcharging of the system occurs due to the close proximity of thepipe obvert to the surface level and the high pit losses occurring at these manholes.This results in a reduced capacity for this section of the system.Even for events with small return periods, the capacities of the minor branches of thesystem are limited by small pipe diameters and by the very low grades at which thepipes are laid.6.3 CULVERT STRUCTURESTable 6-3 lists the culvert structures through which Minnegang Creek passes.Table 6-3 Culvert structuresCulvert location Structure details U/S invertlevel (m)D/S invertlevel (m)Length(m)U/S weirlevel (m)Lake HeightsRoadNorthcliffeDriveIllawarra YachtClub carpark1200 mm diameter RCP 26.82 26.18 21.8 29.43-cell box culvert(1.9m x 1.25m / 1.8m x1.25m / 1.9m x 1.25m)0.65 0.47 19 2.102 x 1650mm diameter RCP 0.48 0.43 7.3 2.45SV8507-D0-001 Rev 2 6-5218/10/02

The culvert capacities were calculated by considering different combinations ofheadwaters and tailwaters at each culvert, to determine the maximum capacity throughthe culvert. No blockage of the culverts was assumed for these calculations. Culvertflows are based on the MIKE 11 results and were verified using Culvhyd, a culvertdesign and analysis program.Table 6-4 presents the flow in each culvert and the flow over the weir at each culvertlocation from MIKE 11 for the 1%, 2%, 5% and 20% AEP events.Table 6-4 Culvert capacitiesCulvert locationFlow in culvert (m 3 /s)(Weir flow)20% AEP 5% AEP 2% AEP 1% AEPLake Heights Road 5.15.35.45.4(1.6)(5.8)(7.8)(10.5)Northcliffe Drive 7.44.81.71.1Illawarra YachtClub carpark(9.7)9.7(0.0)(13.4)11.7(0.9)(16.6)12.4(4.7)(20.9)10.6(11.3)The capacity of the Northcliffe Drive culvert during the design events is significantlylower than the calculated full flow capacity. This can be explained by considering thedifference in the headwater and tailwater levels at this culvert. In all the design events,the headwater and tailwater are essentially at the same level. This means that there islittle head differ ence available to force water to pass through the culvert. Downstreamof the Illawarra Yacht Club carpark culvert there is a larger difference between theheadwater and tailwater levels in all events, and hence the flow through the culvert ishigher.6.4 RESULTS DOWNSTREAM OF NORTHCLIFFE DRIVEIn each of the modelled events, the predicted flood levels overtop Northcliffe Drive.Analysis of the results shows that these elevated flood levels are mainly due to theculvert within the Illawarra Yacht Club carpark. As the road surface level at thisculvert is higher than the level of Northcliffe Drive, water builds up behind theIllawarra Yacht Club culvert and then overtops Northcliffe Drive. This reduces theflow through the Northcliffe Drive culvert due to the small differences in theheadwater and tailwater levels at the culvert.The flood extents for each design event in the area downstream of Northcliffe Drivehave been plotted to the full extent of each cross section when the natural surfacelevels remain lower than the predicted flood level. This is consistent with themodelling approach for this area as discussed in Section 5.11.6.5 IMPACT OF COUNCIL’S CONDUIT BLOCKAGE POLICYCouncil’s Conduit Blockage Policy requires that a 100% blockage factor be applied toall structures with a major diagonal opening of less than 6 m, or 25% bottom upblockage where this dimension is greater than 6 m. The Blockage Policy also requiresSV8507-D0-001 Rev 2 6-5318/10/02

that handrails above these structures be modelled with a 100% bloc kage factor. In linewith this policy, the profiles and extents as presented in Section 6.1 reflect the worstcaseblockage scenario within the catchment.The culvert structures under Lake Heights Road, Northcliffe Drive and IllawarraYacht Club required a 100% blockage factor. As the clear diagonal opening under theJane Avenue bridge is greater than 6 m , the bridge was modelled with 25% blockage.The sections of the piped stormwater drainage system included in the MIKE 11 modelwere also modelled with a 100% blockage factor. This included the outlet to theBarina Park detention basin. Handrails in the catchment are located over the threeculverts and on the Jane Ave bridge. All these handrails were modelled as 100%blocked.For the Minnegang Creek catchment, the worst-case blockage scenario occurs whenall structures within the creek are blocked in accordance with the Blockage Policy.This results in higher peak flood levels within Minnegang Creek than any othercombination of blocked and unblocked culverts.The impact of the blockage policy is shown in Figure 6-13 to 6-16. These figuresshow the difference in flood levels in Minnegang Creek between the no blockage andworst-case blockage scenarios for the 1% AEP flood event at each structure. Theimplications of blockage and the resulting flow diversions for each of the structureswithin the catchment are discussed below.6.5.1 Lake Heights Road culvertThe profile for the Lake Heights Road culvert indicates that some attenuation of flowsoccurs under normal flow conditions. When blocked, flow builds up behind the culvertuntil it overtops Lake Heights Road. This results in a higher peak flow over the weirthan the combined flow through the culvert and weir. The higher flow results in higherflood levels downstream of the culvert until the detention basin in Barina Park. Floodlevels are increased for a distance of approximately 100 m upstream of the culvert dueto water ponding behind the blocked culvert.The Lake Heights Road culvert is located at the low point of Lake Heights Road.Therefore, any flow that does not pass through the culvert, will build up behind theculvert until the road is overtopped. Flow will then follow the alignment of the culvertto pass over the road and rejoin Minnegang Creek. Therefore, no diversions of flowoccur to adjacent to sub-catchments.6.5.2 Barina Park detention basinThe capacity of the Barina Park detention basin is inadequate to detain flood flows inall design events. However, blockage of the outlet leads to higher flows passing overthe basin embankment than for the unblocked outlet. This leads to increased floodlevels downstream of the basin. Flood levels upstream of the basin are not increasedsignificantly over the unblocked outlet levels as the levels upstream of theembankment in the unblocked case are limited by the level of the embankment.Flow diversions to adjacent sub-catchments do not occur due to blockage of the outletto the basin. The flows leave the basin over an increased width of the embankment andthen follow a similar alignment to flows resulting from the unblocked case. It isSV8507-D0-001 Rev 2 6-5418/10/02

important to note that blockage of the outlet has implications in terms of the drainingof Barina Park following a storm event. In the case of the outlet being blocked, watercan only leave the basin through infiltration until the blockage can be cleared. Thiscould affect the availability of the playing fields in Barina Park to the public. This willbe further investigated in the Floodplain Risk Management Study.6.5.3 Jane Avenue bridgeThe Jane Avenue bridge was modelled in MIKE 11 with 25% bottom up blockage.This leads to a significant increase in flood levels upstream of the structure. The affluxdue to the blockage extends upstream for a distance of approximately 250 m. Theincreases in flood levels due to blockage at this location are sensitive to the blockagefactor applied to the structure. Flood levels downstream of the bridge are slightlyincreased by blockage of the bridge over the unblocked case.Blockage of the Jane Avenue bridge does not lead to flow diversions to adjacent subcatchments.At the location of the bridge, the channel is deep with steep banks and cancontain the increased flood levels upstream of the bridge, without diversions of theflow occurring.6.5.4 Northcliffe Drive and Illawarra Yacht Club culvertsBlockage of the Illawarra Yacht Club culvert would impact flood levels forapproximately 400 m upstream. As discussed earlier, the constriction posed by thisculvert under all flood conditions creates backwater effects that significantly impactthe capacity of the Northcliffe Drive culvert. Consequently, blockage of theNorthcliffe Drive culvert has negligible impact on upstream flood levels.Blockage of the Northcliffe Drive and Illawarra Yacht culverts do not lead to flowdiversions due to the location of these culverts at the downstream end of thecatchment. It is also relevant to note that if Lake Illawarra is flooded, then the culvertsat Northcliffe Drive and in the Yacht club carpark are submerged by floodwaters fromthe lake and blockage is not an issue.6.6 FUTURE DEVELOPMENT CONDITIONSAs previously discussed, RAFTS modelling of the catchment based on futuredevelopment conditions showed that increases in flow rates compared to those basedon existing development conditions were negligible.Future development conditions were modelled by considering areas of the catchmentthat could be developed further within the current land zoning. The large undevelopedarea south east of Flagstaff Road and Hilltop Avenue could be developed in the future.All other areas within the catchment are fully developed within their respective landzone entitlements.Future development was modelled by increasing the impervious area in the RAFTSmodel for the sub-catchments covering the area identified with potential for futuredevelopment. Developed conditions led to an increase of flows in individual subcatchmentsof less than 5%, whilst the increase in the total flow in Minnegang Creekwas less than 0.2%. It was therefore assumed that the effects of future development onSV8507-D0-001 Rev 2 6-5518/10/02

flooding within the catchment are negligible and hence future development conditionswere not modelled in MIKE 11.SV8507-D0-001 Rev 2 6-5618/10/02

40.01% AEP flood level - blocked case1% AEP flood level - unblocked caseInvert levelChainage35.0LAKE HEIGHTS ROAD CULVERT30.2326.9327.3431.8030.0Elevation (m AHD)25.026.3025.7725.4120.00.4020.4540.5250.5290.5540.5760.59615.00.4 0.5 0.6Chainage (km)Figure 6-131% AEP FLOOD PROFILESLAKE HEIGHTS ROAD CULVERTMinnegang Creek Flood Study

35.01% AEP flood level - blocked case1% AEP flood level - unblocked caseInvert levelChainage30.019.0125.7920.6620.61BARINA PARKDETENTION BASIN0.6160.6450.6720.7160.7580.7800.8030.8080.81319.0124.4024.1521.5826.3326.5326.3326.9826.9827.580.8350.8790.8870.9961.00925.0Elevation (m AHD)20.015.010.00.6 0.7 0.8 0.9 1.0Chainage (km)Figure 6-141% AEP FLOOD PROFILESBARINA PARK DETENTION BASINMinnegang Creek Flood Study

25.01% AEP flood level - blocked case1% AEP flood level - unblocked caseInvert levelChainage20.015.017.06Elevation (m AHD)16.7112.8012.80JANE AVE BRIDGE10.010.071.0571.0661.0867.507.478.718.548.549.361.1311.2251.2671.3081.3351.3391.3821.4065.00.01.0 1.1 1.2 1.3 1.4Chainage (km)Figure 6-151% AEP FLOOD PROFILESJANE AVE BRIDGEMinnegang Creek Flood Study

20.01% AEP flood level - blocked case1% AEP flood level - unblocked caseInvert levelChainage15.010.05.0Elevation (m AHD)7.475.244.84NORTHCLIFFE DRIVE CULVERT0.881.080.600.400.550.570.450.401.4061.5131.5451.5841.6311.682-0.051.981.612.653.223.881.7471.8181.8361.9021.9601.9801.9882.0172.029ILLAWARRA YACHT CLUB CULVERT0.0-5.01.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1Chainage (km)Figure 6-161% AEP FLOOD PROFILESNORTHCLIFFE DRIVE AND ILLAWARRAYACHT CLUB CULVERTSMinnegang Creek Flood Study

Appendix AREFERENCESSV8507-DO-001 Rev 218/10/02

Appendix AReferencesBureau of Meteorology (December 1994), Bulletin 53: The Estimation of Probable MaximumPrecipitation in Australia: Generalised Short - Duration Method, Australian Government PublishingService, CanberraConcrete Pipe Association of Australasia (1991), Hydraulics of Precast Concrete Conduits: Pipes and boxculverts, Concrete Pipe Association of Australasia, SydneyDanish Hydraulic Institute (1995), Mike 11 Version 3.11 User Manual, 1st Edition, Danish HydraulicInstituteDanish Hydraulic Institute (1998), Mike 11 Version 3.20 - numerical model, Danish Hydraulic InstituteFrench, Richard (1986), Open-channel hydraulics, McGraw Hill, New YorkHydrologic Engineering Center (1997), HEC-RAS River Analysis System, US Army Corps of Engineers,CaliforniaInstitution of Engineers (1987), Australian Rainfall and Runoff - A Guide to Flood Estimation, Institutionof Engineers, AustraliaKinhill (1993), Upper Narrara Creek Flood Study, prepared for Gosford City CouncilLawson and Treloar Pty Ltd (2000), Lake Illawarra Flood Study, Lawson and Treloar Pty Ltd, SydneyNew South Wales Government (January 2001), Floodplain Management Manual: the management offlood liable land, New South Wales Government.Verwey A (1994), Linkage of Physical and Numerical Aspects of Models Applied in EnvironmentalStudies in Selected papers - the use of one dimensional models in flood plain managementWP Software (January 1994), RAFTS-XP Runoff Analysis & Flow Training Simulation with XPGraphical Interface - User’s Manual, WP Software, ACTWP Software (1996), RAFTS-XP Runoff Analysis & Flow Training Simulation - numerical model, WPSoftware, ACTWP Software (January 1996), XP-RatHGL Rational Formula Hydrology and Hydraulic Grade LineIncorporating the EXPERT User Environment, WP Software, ACTWP Software (1997), XP-RatHGL Rational Formula Hydrology and Hydraulic Grade Line - computerprogram, WP Software, ACTWollongong City Council (1990, amended 9 March 2001), City of Wollongong Local EnvironmentalPlan 1990, Wollongong City Council, Wollongong.Wollongong City Council (1998), Drainage Design Code, Wollongong City Council, Wollongong.Wollongong City Council (2001), Conduit Blockage Policy, Wollongong City Council, Wollongong.SV8507-DO-001 Rev 2 A-118/10/02

Wollongong City Council (2001), Draft Development Control Plan - Managing Our Flood Risks,Wollongong City Council, WollongongSV8507-DO-001 Rev 2 A-218/10/02

Appendix BGLOSSARYSV8507-DO-001 Rev 218/10/02

Appendix BGLOSSARYAnnual Exceedence Probability (AEP)Australian Height Datum (AHD)Average Recurrence Interval (ARI)cadastral basecatchmentdischargefloodfloodplainthe chance of a flood of a given or larger sizeoccurring in any one year, usually expressed asa percentage.a common national surface level datumapproximately corresponding to mean sealevel.the long-term average number of years betweenthe occurrence of a flood as big as or largerthan the selected event, eg. floods with adischarge as great as or greater than the 20 yearARI flood event will occur on average onceevery 20 years. ARI is another way ofexpressing the likelihood of occurrence of aflood event.information in map and/or digital formshowing the extent and usage of land includingstreets, lot boundaries, water course.the land area draining through the main stream,as well as tributary streams, to a particular site.It always relates to a specific location.the rate of flow of water measured in terms ofvolume per unit time.relatively high stream flow which overtops thenatural or artificial banks in any part of astream, river, estuary, lake or dam and/oroverland runoff before entering a watercourseand/or coastal inundation resulting for superelevated sea levels and/or waves overtoppingcoastline defences.area of land which is subject to inundation byfloods up to the probable maximum flood eventie flood prone land.SV8507-DO-001 Rev 2 B-118/10/02

hydraulicshydrographhydrologyMIKE 11peak dischargeterm given to the study of water flows inwaterways; in particular, the evaluation of flowparameters such as water level and velocity.a graph which shows how the discharge orstage/flood level at any particular locationchanges with time during a flood.term given to the study of the rainfall andrunoff processes; in particular, the evaluationof peak flows, flow volumes and the derivationof hydrographs for a range of floods.the unsteady one dimensional hydraulic modelused for this study.the maximum discharge occurring during aflood event.Probable Maximum Flood (PMF) the largest possible flood that couldconceivably occur at a particular location. ThePMF defines the extent of flood prone land, iethe floodplain.Probable Maximum Precipitation (PMP)RAFTSRatHGLrunoffstagethe greatest depth of precipitation for a givenduration meteorologically possible over a givensize storm at a particular location at a particulartime of the year, with no allowance made forlong-term climatic trends. It is the primaryinput to the estimation of the probablemaximum flood.the hydrologic model used for this study(Runoff Analysis & Flow TrainingSimulation).urban stormwater drainage piped networkanalysis and design program used to analysethe pipe system for this study.the amount of rainfall which actually ends upas streamflow.equivalent to water level. Measured withreference to a specified datum.SV8507-DO-001 Rev 2 B-218/10/02

Appendix CHISTORICAL FLOOD DATASV8507-DO-001 Rev 218/10/02

Appendix CHistorical Flood DataRECORDED FLOOD LEVELSFigure C-1 is a catchment plan with recorded flood levels for the following storm events:• 14 December 1985• 23 October 1987• December 1990• 17 August 1998RAIN GAUGE LOCATIONSFour rain gauge stations are located in the vicinity of the Minnegang Creek catchment. The gauges andthe organisations that operate them are as follows:• Berkeley B44 gauge (Sydney Water)• Port Kembla SPS 176 gauge (Sydney Water)• Port Kembla (Manly Hydraulics Laboratory)• Station 68110 Northcliffe Drive, Berkeley (Bureau of Meteorology)The first three of these gauges are continuously monitoring stations. Rainfall is available in five minuteincrements at each of the stations. Rainfall is only available in daily increments for the Bureau ofMeteorology station.The locations of these gauges in relation to the Minnegang Creek catchment are shown in Figure C-2.SV8507-DO-001 Rev 2 C-118/10/02

RAINFALL - 17 AUGUST 1998 CALIBRATION EVENTRainfall from the Berkeley B44 gauge was used for the generating hydrographs for the 17 August 1998storm event. This gauge was chosen as it is the closest gauge to the Minnegang Creek catchment of thecontinuously monitoring gauges listed above. The rainfall recorded at this gauge, for this event is asfollows:Gauge Name: Berkeley B44 (Sports and Social Club)Data Source: Sydney WaterTime of Collection: 9:00am on the 17/8/98 to 9:00am on the 18/8/98Time Rain(mm)Time Rain(mm)Time Rain(mm)Time Rain(mm)Time Rain(mm)9:05 1 11:50 0.5 14:35 0.5 17:20 1.5 20:05 49:10 1 11:55 0.5 14:40 0.5 17:25 0.5 20:10 39:15 0.5 12:00 0 14:45 0.5 17:30 1.5 20:15 1.59:20 0.5 12:05 0.5 14:50 0.5 17:35 1 20:20 1.59:25 0.5 12:10 0.5 14:55 1 17:40 1.5 20:25 19:30 1.5 12:15 0.5 15:00 0.5 17:45 0.5 20:30 0.59:35 0 12:20 1.5 15:05 0.5 17:50 0.5 20:35 09:40 1 12:25 1 15:10 0.5 17:55 0 20:40 0.59:45 1 12:30 1.5 15:15 1.5 18:00 0.5 20:45 0.59:50 1 12:35 1 15:20 0.5 18:05 1 20:50 0.59:55 0.5 12:40 1 15:25 0.5 18:10 1 20:55 110:00 1.5 12:45 1 15:30 0.5 18:15 1 21:00 1.510:05 1 12:50 1 15:35 0.5 18:20 2 21:05 0.510:10 1.5 12:55 0.5 15:40 0.5 18:25 2 21:10 110:15 1 13:00 1 15:45 0.5 18:30 1 21:15 0.510:20 1 13:05 0 15:50 0 18:35 0 21:20 0.510:25 0 13:10 0 15:55 0.5 18:40 0.5 21:25 0.510:30 1 13:15 0.5 16:00 0.5 18:45 1 21:30 0.510:35 0.5 13:20 0 16:05 0.5 18:50 2 21:35 110:40 0.5 13:25 0.5 16:10 1 18:55 1 21:40 0.510:45 1 13:30 0 16:15 0.5 19:00 1.5 21:45 0.510:50 1 13:35 0.5 16:20 1 19:05 0.5 21:50 1.510:55 0.5 13:40 0.5 16:25 0.5 19:10 1 21:55 0.511:00 0.5 13:45 0 16:30 0.5 19:15 1 22:00 0.511:05 1 13:50 0.5 16:35 0.5 19:20 1 22:05 111:10 0.5 13:55 0.5 16:40 0.5 19:25 1 22:10 0.511:15 1.5 14:00 0 16:45 0.5 19:30 3 22:15 0.511:20 1 14:05 0.5 16:50 1 19:35 4 22:20 011:25 0.5 14:10 0.5 16:55 0.5 19:40 7.5 22:25 0.511:30 1 14:15 0.5 17:00 1 19:45 4.5 22:30 011:35 0.5 14:20 0.5 17:05 1 19:50 6.5 22:35 011:40 1 14:25 0 17:10 1 19:55 4 22:40 011:45 0.5 14:30 0.5 17:15 1 20:00 6 22:45 0SV8507-DO-001 Rev 2 C-218/10/02

Time Rain(mm)Time Rain(mm)Time Rain(mm)Time Rain(mm)Time Rain(mm)22:50 0 0:55 0 3:00 2 5:05 0.5 7:10 022:55 0 1:00 0 3:05 0.5 5:10 0 7:15 023:00 0 1:05 0 3:10 1 5:15 0 7:20 023:05 0.5 1:10 0 3:15 0.5 5:20 0 7:25 023:10 0 1:15 0 3:20 1 5:25 0 7:30 123:15 0 1:20 0.5 3:25 0.5 5:30 0 7:35 0.523:20 0 1:25 0 3:30 0.5 5:35 0.5 7:40 123:25 0 1:30 0.5 3:35 0.5 5:40 0.5 7:45 0.523:30 0 1:35 0.5 3:40 1 5:45 0.5 7:50 123:35 0 1:40 0.5 3:45 0.5 5:50 0.5 7:55 123:40 0 1:45 0 3:50 1 5:55 0 8:00 0.523:45 0 1:50 1 3:55 1 6:00 0.5 8:05 123:50 0 1:55 1 4:00 2 6:05 0 8:10 0.523:55 0 2:00 1 4:05 1 6:10 1 8:15 0.50:00 0 2:05 0 4:10 1 6:15 0.5 8:20 00:05 0 2:10 0 4:15 0 6:20 1 8:25 00:10 0.5 2:15 1 4:20 1 6:25 0 8:30 0.50:15 0 2:20 0.5 4:25 0.5 6:30 0.5 8:35 00:20 0 2:25 0.5 4:30 2.5 6:35 0 8:40 00:25 0.5 2:30 0.5 4:35 1 6:40 0 8:45 00:30 0.5 2:35 0.5 4:40 1 6:45 0 8:50 00:35 0 2:40 1 4:45 1 6:50 0.5 8:55 00:40 0 2:45 0.5 4:50 0.5 6:55 0.5 9:00 0.50:45 0.5 2:50 0.5 4:55 1 7:00 0 9:05 00:50 0 2:55 1 5:00 0.5 7:05 0.5 TOTAL 205 mmRUNOFF HYDROGRAPH - 17 AUGUST 1998 CALIBRATION EVENTA plot of the runoff hydrograph for this event at the downstream extent of Minnegang Creek is shownbelow. This was determined from the RAFTS model of the catchment.0.80.70.6Runoff Hydrograph: 17 - 18 August 1998 Calibration EventFlow (m3/s)0.50.40.30.20.107:00 9:00 11:00 13:00 15:00 17:00 19:00 21:00 23:00 1:00 3:00 5:00 7:00 9:00 11:00Time (hrs)SV8507-DO-001 Rev 2 C-318/10/02

Figure C-1HISTORIC FLOOD LEVELSMinnegang Creek Flood Study

Appendix DRAFTS HYDROLOGIC MODELSV8507-DO-001 Rev 218/10/02

Appendix DRafts Hydrologic ModelRAFTS MODEL PARAMETERSSUMMARY OF CATCHMENT AND RAINFALL DATALink Catch. Area Slope % Impervious Pern B LinkLabel #1 #2 #1 #2 #1 #2 #1 #2 #1 #2 No.(hectares) (%) (%)MH001A .4108 .2787 13.30 13.30 5.000 100.0 .025 .015 .0036 .0002 1.000MH60 .6230 .3034 15.20 15.20 5.000 100.0 .025 .015 .0042 .0002 1.001MH54 .4386 .2964 15.20 15.20 5.000 100.0 .025 .015 .0035 .0002 1.002MH56 .3978 .3429 10.90 10.90 5.000 100.0 .025 .015 .0039 .0003 2.000MH53 .6717 .6275 11.00 11.00 5.000 100.0 .025 .015 .0051 .0004 1.003MH50 .5894 .5306 13.60 13.60 5.000 100.0 .025 .015 .0043 .0003 3.000MH50A .9635 .8440 8.000 8.000 5.000 100.0 .025 .015 .0073 .0005 1.004MH52 .00670 .1273 13.80 13.80 5.000 100.0 .025 .015 .0004 .0001 1.005MH46 .8128 .7289 14.30 14.30 5.000 100.0 .025 .015 .0050 .0003 4.000MH48 .3367 .4625 13.50 13.50 5.000 100.0 .025 .015 .0032 .0003 4.001MH52C 1.508 .4316 10.70 10.70 5.000 100.0 .025 .015 .0079 .0003 1.006MH43 .5782 .7181 7.200 7.200 5.000 100.0 .025 .015 .0059 .0005 5.000MH41 1.509 1.440 10.00 10.00 5.000 100.0 .025 .015 .0082 .0006 5.001MH21 .9294 1.276 10.00 10.00 5.000 100.0 .025 .015 .0064 .0005 6.000MHA 1.196 .4206 19.80 19.80 5.000 100.0 .025 .015 .0052 .0002 7.000MH30 .5908 .3418 15.60 15.60 5.000 100.0 .025 .015 .0040 .0002 7.001MH29 .00399 .0758 9.200 9.200 5.000 100.0 .025 .015 .0004 .0001 7.002MHB 2.190 .6472 20.00 20.00 5.000 100.0 .025 .015 .0070 .0003 8.000MH28 .5164 .3002 15.00 15.00 5.000 100.0 .025 .015 .0038 .0002 8.001MH27 .00361 .0686 7.500 7.500 5.000 100.0 .025 .015 .0004 .0001 8.002MH27A .6769 .2537 10.80 10.80 5.000 100.0 .025 .015 .0052 .0002 7.003MH26A 2.999 .8244 12.00 12.00 5.000 100.0 .025 .015 .0107 .0004 9.000MH26 .2229 .1860 9.600 9.600 5.000 100.0 .025 .015 .0031 .0002 9.001MH25 .00393 .0748 8.900 8.900 5.000 100.0 .025 .015 .0004 .0001 9.002MH24 .9714 .3994 6.200 6.200 5.000 100.0 .025 .015 .0083 .0004 10.00MH23 .00435 .0826 7.100 7.100 5.000 100.0 .025 .015 .0005 .0002 10.00MHC 6.268 3.007 3.500 3.500 5.000 100.0 .025 .015 .0291 .0014 5.002MHD .6056 .8400 9.200 9.200 5.000 100.0 .025 .015 .0053 .0004 5.003SV8507-DO-001 Rev 2 D-118/10/02

MHE .5359 .3573 12.10 12.10 5.000 100.0 .025 .015 .0044 .0003 5.004MH31 .3018 .3845 10.10 10.10 5.000 100.0 .025 .015 .0035 .0003 11.00MH32 .00797 .1515 5.200 5.200 5.000 100.0 .025 .015 .0007 .0002 11.00MH36 .0138 .2622 7.300 7.300 5.000 100.0 .025 .015 .0008 .0003 11.00MH67 2.017 1.795 8.100 8.100 5.000 100.0 .025 .015 .0106 .0007 11.00Dummy1 .00100 .000 .0010 .0000 5.000 .0000 .025 .00 .0181 .0000 5.005MH68 .0207 .3934 2.800 2.800 5.000 100.0 .025 .015 .0017 .0005 5.006MH69A 2.299 .2507 10.00 10.00 5.000 100.0 .025 .015 .0102 .0002 1.007MH70 .7560 .0704 12.00 12.00 5.000 100.0 .025 .015 .0052 .0001 1.008MH78 .7643 .9238 8.100 8.100 5.000 100.0 .025 .015 .0064 .0005 1.009MH62 .6121 .7124 5.500 5.500 5.000 100.0 .025 .015 .0069 .0005 12.00MH72 .6112 .7302 15.00 15.00 5.000 100.0 .025 .015 .0042 .0003 13.00MH76 .00498 .0946 8.500 8.500 5.000 100.0 .025 .015 .0005 .0002 13.00MH77 .8444 .9552 7.600 7.600 5.000 100.0 .025 .015 .0070 .0005 12.00Dummy2 .00100 .000 .0010 .0000 5.000 .0000 .025 .00 .0181 .0000 1.010MH79 1.112 1.005 8.900 8.900 5.000 100.0 .025 .015 .0074 .0005 1.011MH80 .0199 .3790 10.90 10.90 5.000 100.0 .025 .015 .0008 .0003 1.012MHF .6472 .3568 11.80 11.80 5.000 100.0 .025 .015 .0049 .0003 1.013MH87 .1994 .5179 5.700 5.700 5.000 100.0 .025 .015 .0038 .0004 14.00MH96 .2775 .3876 2.900 2.900 5.000 100.0 .025 .015 .0063 .0005 15.00MH94 .00323 .0614 7.000 7.000 5.000 100.0 .025 .015 .0004 .0001 16.00MH95 .00621 .1180 1.800 1.800 5.000 100.0 .025 .015 .0011 .0004 15.00MH98 1.838 1.386 10.50 10.50 5.000 100.0 .025 .015 .0089 .0005 14.00MH100 .1699 .3365 12.50 12.50 5.000 100.0 .025 .015 .0024 .0002 14.00MC1 .4072 .1728 11.40 11.40 5.000 100.0 .025 .015 .0039 .0002 1.014MH104 .4496 .8207 12.40 12.40 5.000 100.0 .025 .015 .0039 .0004 17.00MC2 2.125 .4192 16.70 16.70 5.000 100.0 .025 .015 .0076 .0002 1.015MC3 1.422 .6976 5.700 5.700 5.000 100.0 .025 .015 .0105 .0005 1.016MH114 .5957 .5694 10.40 10.40 5.000 100.0 .025 .015 .0050 .0003 18.00MH115 .00836 .1589 7.000 7.000 5.000 100.0 .025 .015 .0007 .0002 18.00MH110 1.273 1.293 5.900 5.900 5.000 100.0 .025 .015 .0098 .0007 18.00S055 .8054 .9036 7.000 7.000 5.000 100.0 .025 .015 .0071 .0005 19.00MC4 2.210 .3424 7.200 7.200 5.000 100.0 .025 .015 .0118 .0003 19.00Dummy3 .00100 .000 .0010 .0000 5.000 .0000 .025 .00 .0181 .0000 1.017MH132 .5472 .6736 12.00 12.00 5.000 100.0 .025 .015 .0044 .0004 20.00MH134 .00629 .1194 5.600 5.600 5.000 100.0 .025 .015 .0006 .0002 20.00MHG 1.866 .3656 7.000 7.000 5.000 100.0 .025 .015 .0110 .0003 20.00Dummy4 .00100 .000 .0010 .0000 5.000 .0000 .025 .00 .0181 .0000 1.018SV8507-DO-001 Rev 2 D-218/10/02

MODEL SENSITIVITYThe following tables present the results of the sensitivity analysis carried out to assess the robustness ofthe RAFTS model to the chosen model parameters. This analysis was carried out for the 1% and 20%AEP events for the catchment, assuming a 1 minute lag time between all sub-catchments. The followingtwo tables present the results of the analysis for a range of parameters.The flows at MHG represent the total flow from the catchment for each of the 1% and 20% AEP events.Table D1 1% AEP flood eventMannings n 0.025 0.025 0.025 0.025 0.02 0.05% impervious 5 5 5 10 5 5Initial loss 15 35 10 15 15 15Continuing loss 2.5 2.5 0 2.5 2.5 2.5MC1 32.12 29.44 32.85 33.09 33.55 28.51MC2 32.80 30.09 33.56 33.77 34.20 29.38MC3 33.25 30.51 34.02 34.20 34.61 29.99MC4 35.06 32.17 35.92 35.89 36.23 32.31MH001A 0.50 0.50 0.50 0.52 0.52 0.41MH100 3.08 2.82 3.14 3.23 3.29 2.65MH101 0.94 0.93 0.95 1.00 1.02 0.79MH104 0.85 0.85 0.86 0.90 0.93 0.72MH110 3.23 3.04 3.28 3.42 3.51 2.66MH111 3.01 2.83 3.06 3.20 3.29 2.46MH114 0.76 0.75 0.77 0.81 0.83 0.65MH115 0.88 0.86 0.89 0.92 0.94 0.74MH132 0.82 0.81 0.83 0.87 0.89 0.69MH134 0.90 0.89 0.91 0.95 0.96 0.75MH21 1.36 1.32 1.38 1.46 1.51 1.16MH23 0.87 0.82 0.88 0.93 0.96 0.72MH24 0.82 0.77 0.83 0.87 0.90 0.67MH25 2.65 2.53 2.68 2.81 2.88 2.26MH26 2.60 2.50 2.64 2.77 2.84 2.22MH26A 2.34 2.26 2.37 2.49 2.57 1.99MH27 2.54 2.53 2.57 2.64 2.67 2.14MH27A 5.21 5.19 5.28 5.37 5.49 4.52MH28 2.50 2.49 2.53 2.61 2.64 2.10MH29 2.24 2.23 2.27 2.33 2.36 1.93MH30 2.20 2.19 2.23 2.29 2.32 1.88MH31 0.47 0.47 0.48 0.50 0.51 0.39MH32 0.11 0.11 0.11 0.12 0.12 0.09MH36 0.19 0.19 0.19 0.20 0.20 0.16MH41 2.54 2.41 2.58 2.69 2.76 2.14MH42 2.48 2.35 2.51 2.63 2.70 2.08MH43 0.79 0.76 0.80 0.85 0.87 0.66MH46 1.15 1.15 1.17 1.22 1.24 0.98MH47 1.30 1.29 1.31 1.36 1.38 1.10MH48 1.62 1.62 1.64 1.69 1.71 1.42MH50 0.77 0.77 0.78 0.81 0.83 0.65SV8507-DO-001 Rev 2 D-318/10/02

Mannings n 0.025 0.025 0.025 0.025 0.02 0.05% impervious 5 5 5 10 5 5Initial loss 15 35 10 15 15 15Continuing loss 2.5 2.5 0 2.5 2.5 2.5MH50A 4.45 4.38 4.50 4.62 4.72 4.04MH52 4.52 4.44 4.58 4.68 4.78 4.10MH52C 7.92 7.70 8.02 8.16 8.28 7.05MH53 2.72 2.69 2.75 2.80 2.85 2.49MH54 1.51 1.50 1.53 1.55 1.57 1.37MH56 0.51 0.51 0.52 0.54 0.55 0.42MH59 1.18 1.18 1.20 1.22 1.25 1.05MH60 1.11 1.11 1.13 1.16 1.17 0.96MH61 0.86 0.86 0.87 0.89 0.91 0.73MH62 0.77 0.73 0.79 0.83 0.85 0.63MH67 19.29 17.45 19.74 20.54 21.03 15.85MH68 19.47 17.63 19.93 20.74 21.22 16.03MH69A 27.66 25.34 28.27 28.96 29.50 23.55MH70 27.93 25.60 28.55 29.23 29.76 23.85MH72 0.93 0.92 0.94 0.98 1.00 0.78MH76 0.99 0.99 1.00 1.04 1.06 0.83MH77 29.56 27.13 30.23 30.77 31.23 25.63MH78 28.48 26.16 29.13 29.79 30.29 24.49MH79 30.19 27.69 30.88 31.32 31.75 26.33MH80 30.26 27.76 30.96 31.40 31.83 26.41MH87 0.86 0.75 0.87 0.89 0.91 0.69MH94 0.46 0.41 0.47 0.49 0.51 0.36MH95 0.43 0.38 0.44 0.46 0.47 0.33MH96 0.37 0.32 0.37 0.38 0.40 0.28MH98 1.95 1.77 1.99 2.07 2.12 1.64MH99 2.01 1.83 2.06 2.13 2.17 1.70MHA 1.57 1.56 1.59 1.66 1.69 1.35MHB 1.95 1.95 1.98 2.06 2.09 1.63MHC 16.19 14.62 16.61 17.32 17.81 13.05MHD 17.13 15.47 17.56 18.24 18.78 13.85MHE 17.53 15.82 17.96 18.68 19.21 14.23MHF 30.48 27.95 31.17 31.59 32.01 26.66MHG 35.72 32.78 36.60 36.51 36.82 33.15Table D2 20% AEP flood eventMannings n 0.025 0.025 0.025 0.025 0.02 0.05% impervious 5 5 5 10 5 5Initial loss 15 35 10 15 15 15Continuing loss 2.5 2.5 0 2.5 2.5 2.5MC1 19.90 11.55 20.68 20.54 20.82 17.61MC2 20.24 11.85 21.08 20.88 21.15 18.04MC3 20.49 12.04 21.34 21.11 21.36 18.35SV8507-DO-001 Rev 2 D-418/10/02

Mannings n 0.025 0.025 0.025 0.025 0.02 0.05% impervious 5 5 5 10 5 5Initial loss 15 35 10 15 15 15Continuing loss 2.5 2.5 0 2.5 2.5 2.5MC4 21.42 12.76 22.34 21.94 22.16 19.50MH001A 0.33 0.21 0.33 0.34 0.34 0.28MH100 2.02 1.16 2.07 2.10 2.14 1.69MH101 0.63 0.39 0.64 0.66 0.67 0.54MH104 0.58 0.36 0.59 0.60 0.61 0.49MH110 2.17 1.21 2.22 2.29 2.36 1.71MH111 2.03 1.13 2.08 2.16 2.20 1.60MH114 0.52 0.32 0.53 0.55 0.56 0.43MH115 0.59 0.36 0.60 0.61 0.62 0.49MH132 0.56 0.34 0.57 0.58 0.59 0.47MH134 0.61 0.37 0.62 0.63 0.64 0.51MH21 0.94 0.55 0.96 1.00 1.02 0.76MH23 0.59 0.31 0.61 0.63 0.65 0.47MH24 0.56 0.30 0.57 0.60 0.61 0.44MH25 1.81 1.04 1.84 1.91 1.94 1.47MH26 1.78 1.03 1.81 1.88 1.92 1.45MH26A 1.61 0.94 1.64 1.71 1.75 1.30MH27 1.67 1.09 1.70 1.71 1.74 1.46MH27A 3.40 2.26 3.46 3.52 3.56 3.05MH28 1.65 1.07 1.68 1.69 1.71 1.44MH29 1.46 0.96 1.49 1.51 1.53 1.30MH30 1.44 0.95 1.46 1.48 1.50 1.27MH31 0.31 0.20 0.32 0.33 0.33 0.26MH32 0.07 0.04 0.07 0.08 0.08 0.06MH36 0.13 0.08 0.13 0.13 0.13 0.11MH41 1.73 0.98 1.76 1.83 1.87 1.39MH42 1.69 0.95 1.72 1.78 1.82 1.35MH43 0.54 0.30 0.55 0.58 0.59 0.43MH46 0.77 0.47 0.78 0.80 0.81 0.65MH47 0.85 0.53 0.86 0.88 0.89 0.73MH48 1.07 0.67 1.09 1.10 1.12 0.94MH50 0.52 0.33 0.53 0.54 0.54 0.44MH50A 2.94 1.81 2.99 3.05 3.09 2.58MH52 2.98 1.83 3.03 3.09 3.13 2.63MH52C 5.08 3.13 5.18 5.27 5.33 4.52MH53 1.77 1.13 1.81 1.82 1.83 1.60MH54 0.95 0.63 0.97 0.98 0.99 0.88MH56 0.34 0.21 0.34 0.35 0.36 0.28MH59 0.78 0.51 0.79 0.80 0.81 0.70MH60 0.73 0.47 0.74 0.74 0.75 0.64MH61 0.56 0.37 0.57 0.58 0.59 0.50MH62 0.53 0.28 0.54 0.57 0.58 0.41MH67 12.45 7.21 12.95 13.11 13.45 10.12SV8507-DO-001 Rev 2 D-518/10/02

Mannings n 0.025 0.025 0.025 0.025 0.02 0.05% impervious 5 5 5 10 5 5Initial loss 15 35 10 15 15 15Continuing loss 2.5 2.5 0 2.5 2.5 2.5MH68 12.56 7.27 13.05 13.22 13.56 10.21MH69A 17.47 10.10 18.13 18.17 18.44 14.86MH70 17.62 10.18 18.29 18.31 18.57 15.02MH72 0.62 0.39 0.63 0.64 0.65 0.53MH76 0.66 0.42 0.67 0.68 0.69 0.57MH77 18.56 10.70 19.25 19.17 19.47 16.05MH78 17.96 10.37 18.64 18.62 18.87 15.38MH79 18.88 10.90 19.59 19.48 19.80 16.43MH80 18.93 10.93 19.64 19.53 19.85 16.48MH87 0.56 0.31 0.57 0.59 0.60 0.45MH94 0.31 0.16 0.32 0.33 0.34 0.24MH95 0.29 0.15 0.29 0.31 0.32 0.22MH96 0.25 0.13 0.25 0.26 0.27 0.19MH98 1.29 0.71 1.33 1.35 1.38 1.05MH99 1.33 0.74 1.37 1.40 1.43 1.09MHA 1.05 0.68 1.07 1.09 1.10 0.91MHB 1.31 0.84 1.33 1.35 1.36 1.11MHC 10.76 6.13 11.14 11.38 11.70 8.43MHD 11.16 6.46 11.56 11.81 12.11 8.87MHE 11.33 6.59 11.79 11.99 12.27 9.09MHF 19.02 11.01 19.73 19.62 19.93 16.60MHG 21.75 13.07 22.69 22.24 22.45 19.91SUMMARY RAFTS OUTPUT1% AEP 2 HOUR STORM EVENTLink Average Init. Loss Cont. Loss Excess Rain Peak Time LinkLabel Intensity #1 #2 #1 #2 #1 #2 Inflow to Lag(mm/h) ( mm ) (mm/h) ( mm ) (m^3/s) Peak (mins)MH001A 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .5126 35.00 .0000MH60 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.200 35.00 .0000MH54 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.748 35.00 .0000MH56 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .5445 35.00 .0000MH53 67.500 15.00 1.500 2.500 .0000 115.62 133.50 3.240 35.00 .0000MH50 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .8346 34.00 .0000MH50A 67.500 15.00 1.500 2.500 .0000 115.62 133.50 5.344 35.00 .0000MH52 67.500 15.00 1.500 2.500 .0000 115.62 133.50 5.439 35.00 .0000MH46 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.140 34.00 .0000MH48 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.752 34.00 .0000MH52C 67.500 15.00 1.500 2.500 .0000 115.62 133.50 8.506 35.00 .0000MH43 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .9270 35.00 .0000SV8507-DO-001 Rev 2 D-618/10/02

MH41 67.500 15.00 1.500 2.500 .0000 115.62 133.50 3.026 35.00 .0000MH21 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.606 35.00 .0000MHA 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.197 35.00 .0000MH30 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.889 35.00 .0000MH29 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.946 35.00 .0000MHB 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.066 35.00 .0000MH28 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.673 35.00 .0000MH27 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.726 35.00 .0000MH27A 67.500 15.00 1.500 2.500 .0000 115.62 133.50 5.356 35.00 .0000S005 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .2502 34.00 .0000MH26A 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.617 35.00 .0000MH26 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.920 35.00 .0000MH25 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.977 35.00 .0000S007 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .3794 35.00 .0000MH24 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .9540 35.00 .0000MH23 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.017 35.00 .0000MHC 67.500 15.00 1.500 2.500 .0000 115.62 133.50 19.146 35.00 .0000MHD 67.500 15.00 1.500 2.500 .0000 115.62 133.50 20.203 35.00 .0000MHE 67.500 15.00 1.500 2.500 .0000 115.62 133.50 20.859 35.00 .0000MH31 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .5133 34.00 1.500MH32 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .6075 36.00 2.000MH36 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .7585 38.00 1.000MH67 67.500 15.00 1.500 2.500 .0000 115.62 133.50 3.118 35.00 .0000Dummy1 67.500 15.00 .0000 2.500 .0000 115.62 .000 23.978 35.00 .0000MH68 67.500 15.00 1.500 2.500 .0000 115.62 133.50 24.287 35.00 .0000MH69A 67.500 15.00 1.500 2.500 .0000 115.62 133.50 34.470 35.00 .0000MH70 67.500 15.00 1.500 2.500 .0000 115.62 133.50 35.074 35.00 .0000MH78 67.500 15.00 1.500 2.500 .0000 115.62 133.50 36.296 35.00 .0000MH62 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .9258 35.00 2.000MH72 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.012 34.00 .5000MH76 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.084 35.00 1.000MH77 67.500 15.00 1.500 2.500 .0000 115.62 133.50 3.129 36.00 .0000Dummy2 67.500 15.00 .0000 2.500 .0000 115.62 .000 39.331 35.00 .0000MH79 67.500 15.00 1.500 2.500 .0000 115.62 133.50 40.833 35.00 .0000MH80 67.500 15.00 1.500 2.500 .0000 115.62 133.50 41.124 35.00 .0000MHF 67.500 15.00 1.500 2.500 .0000 115.62 133.50 41.861 35.00 .0000MH87 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .5367 34.00 .0000MH96 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .4602 35.00 .5000SV8507-DO-001 Rev 2 D-718/10/02

MH94 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .0532 32.00 .5000MH95 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .5908 35.00 .0000MH98 67.500 15.00 1.500 2.500 .0000 115.62 133.50 3.377 35.00 .0000MH100 67.500 15.00 1.500 2.500 .0000 115.62 133.50 3.750 35.00 .0000MC1 67.500 15.00 1.500 2.500 .0000 115.62 133.50 46.038 35.00 .0000MH104 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .9547 34.00 .0000MC2 67.500 15.00 1.500 2.500 .0000 115.62 133.50 48.797 35.00 .0000MC3 67.500 15.00 1.500 2.500 .0000 115.62 133.50 50.171 35.00 .0000MH114 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .8469 34.00 .0000MH115 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .9784 34.00 .0000MH110 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.721 35.00 .0000S055 67.500 15.00 1.500 2.500 .0000 115.62 133.50 1.220 35.00 1.000MC4 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.838 36.00 .0000Dummy3 67.500 15.00 .0000 2.500 .0000 115.62 .000 55.665 35.00 .0000MH132 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .9084 34.00 .5000MH134 67.500 15.00 1.500 2.500 .0000 115.62 133.50 .9972 35.00 .0000MHG 67.500 15.00 1.500 2.500 .0000 115.62 133.50 2.412 35.00 .0000Dummy4 67.500 15.00 .0000 2.500 .0000 115.62 .000 58.077 35.00 .0000HYDROGRAPHSThe following hydrographs from selected locations along Minnegang Creek are presented for the 1%AEP, 2 hour storm event for existing and future development conditions. It can be seen that futuredevelopment has a negligible effect on the resulting flows in Minnegang Creek.6Future and Existing Conditions - MH27AFlow (m3/s)5432Existing conditionsFuture conditions100 50 100 150 200Time (mins)SV8507-DO-001 Rev 2 D-818/10/02

Future and Existing Conditions - MHCFuture and Existing Conditions - MH69A2540Flow (m3/s)201510Existing conditionsFuture conditionsFlow (m3/s)3530252015Existing conditionsFuture conditions510500 50 100 150 200Time (mins)00 50 100 150 200Time (mins)Future and Existing Conditions - MC2Future and Existing Conditions - Dummy 4607050Existing conditions60Existing conditionsFlow (m3/s)403020Future conditionsFlow (m3/s)50403020Future conditions101000 50 100 150 200Time (mins)00 50 100 150 200Time (mins)SV8507-DO-001 Rev 2 D-918/10/02

Appendix EMIKE 11 HYDRAULIC MODELSV8507-DO-001 Rev 218/10/02

Appendix EMIKE 11 HYDRAULIC MODELConverted from RDF file:C:\MIKE11~1\DATA\SV8507\MC_EX.RDFConversion started: 22-FEB-2002 17:13:00Cross Section Data Base Name;MC_01;20; River Branch(es) ==============================Topo ID ; River Name ; Upstr Km; Dwstr Km; Dx-Max;Upstream connection; Downstream connectionEXIST ; MINNEGAN ; 0.000; 2.048; 10000.000;MINNEGAN ; 0.000; MINNEGAN ; 2.048;EXIST ; LAKEWEIR ; 0.529; 0.554; 10000.000;MINNEGAN ; 0.529; MINNEGAN ; 0.554;EXIST ; MELINDA ; 0.000; 0.514; 10000.000;MELINDA ; 0.000; MINNEGAN ; 0.780;EXIST ; RANCHBY1 ; 0.000; 0.098; 10000.000;RANCHBY1 ; 0.000; MINNEGAN ; 0.137;EXIST ; RANCHBY2 ; 0.000; 0.104; 10000.000;RANCHBY2 ; 0.000; MINNEGAN ; 0.220;EXIST ; RANCHBY3 ; 0.000; 0.104; 10000.000;RANCHBY3 ; 0.000; MINNEGAN ; 0.285;EXIST ; RANCHBY4 ; 0.000; 0.107; 10000.000;RANCHBY4 ; 0.000; LAKEHTS2 ; 0.345;EXIST ; LAKEHTS2 ; 0.000; 0.463; 10000.000;LAKEHTS2 ; 0.000; MINNEGAN ; 0.525;EXIST ; CANBERRA ; 0.000; 0.231; 10000.000;CANBERRA ; 0.000; MINNEGAN ; 1.747;EXIST ; KARRABAH ; 0.000; 0.043; 10000.000;KARRABAH ; 0.000; MELINDA ; 0.117;EXIST ; GILGAND ; 0.000; 0.058; 10000.000;GILGAND ; 0.000; MELINDA ; 0.282;EXIST ; DENISE1 ; 0.005; 0.234; 10000.000;DENISE1 ; 0.005; MINNEGAN ; 1.131;SV8507-DO-001 Rev 2 E-118/10/02

EXIST ; DENISE2 ; 0.005; 0.133; 10000.000;DENISE2 ; 0.005; DENISE1 ; 0.160;EXIST ; DENISE3 ; 0.000; 0.039; 10000.000;DENISE3 ; 0.000; MINNEGAN ; 1.308;EXIST ; BARINA ; 0.000; 0.307; 10000.000;BARINA ; 0.000; MINNEGAN ; 0.672;EXIST ; NORWEIR ; 1.960; 1.980; 10000.000;MINNEGAN ; 1.960; MINNEGAN ; 1.980;EXIST ; PIPE_1 ; 0.000; 0.332; 10000.000;PIPE_1 ; 0.000; MINNEGAN ; 1.086;EXIST ; ILLAWEIR ; 2.029; 2.037; 10000.000;MINNEGAN ; 2.029; MINNEGAN ; 2.037;EXIST ; PIPE_10 ; 0.000; 0.177; 10000.000;MINNEGAN ; 0.596; PIPE_1 ; 0.026;EXIST ; JANEWEIR ; 1.335; 1.339; 10000.000;MINNEGAN ; 1.335; MINNEGAN ; 1.339;14; Broad Crested Weir(s) ==============================River name ; Chainage; Structure id ;Head loss factors pos;;; Head loss factors neg;;; Valve reg; No levels;Level ; Width ;LAKEWEIR ; 0.542; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;29.65; 0.00;29.68; 6.30;29.86; 17.72;29.95; 23.74;30.15; 32.91;30.78; 50.00;30.79; 57.10;30.81; 65.31;31.19; 78.06;31.23; 78.97;MINNEGAN ; 0.057; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 8;47.87; 0.00;SV8507-DO-001 Rev 2 E-218/10/02

48.10; 10.30;48.26; 14.30;48.60; 20.30;49.00; 26.20;49.10; 29.00;49.30; 30.00;49.70; 35.00;MINNEGAN ; 0.658; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 6;27.26; 0.00;27.31; 5.00;27.36; 18.50;27.77; 37.00;28.60; 50.00;30.00; 50.00;MINNEGAN ; 0.883; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;20.80; 0.00;20.86; 10.30;20.97; 20.50;21.10; 31.40;21.17; 36.10;21.36; 46.20;21.54; 56.30;21.64; 59.40;21.75; 62.35;24.00; 68.00;MINNEGAN ; 1.003; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;19.15; 0.00;19.20; 5.00;19.30; 21.60;19.64; 37.40;20.55; 59.30;21.50; 75.00;SV8507-DO-001 Rev 2 E-318/10/02

22.40; 88.40;23.30; 100.00;25.10; 120.00;26.00; 120.00;MELINDA ; 0.278; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;31.50; 0.00;31.53; 5.00;31.56; 9.56;31.80; 21.56;32.34; 36.24;32.88; 49.44;33.14; 54.39;33.41; 59.11;33.95; 60.00;36.00; 60.00;RANCHBY1 ; 0.049; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;45.01; 0.00;45.05; 5.00;45.09; 9.80;45.15; 10.00;45.31; 20.00;45.40; 25.00;45.50; 30.00;45.60; 40.00;46.00; 45.00;48.00; 45.00;RANCHBY2 ; 0.048; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;41.29; 0.00;41.30; 4.40;41.40; 8.90;41.80; 20.70;42.10; 28.20;SV8507-DO-001 Rev 2 E-418/10/02

42.50; 36.30;42.70; 40.80;42.90; 45.00;43.20; 45.00;43.40; 45.00;RANCHBY3 ; 0.053; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;41.65; 0.00;41.70; 5.00;41.76; 6.00;41.85; 12.00;42.00; 30.00;42.27; 40.00;42.50; 50.00;42.70; 61.00;43.00; 70.00;45.00; 70.00;NORWEIR ; 1.971; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;1.91; 0.00;1.92; 10.00;1.93; 20.00;1.95; 40.00;1.98; 72.75;2.27; 97.94;2.64; 97.49;3.11; 111.40;3.57; 124.00;3.88; 142.23;MINNEGAN ; 0.808; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 8;26.53; 0.00;26.66; 17.67;26.78; 58.53;26.82; 83.40;SV8507-DO-001 Rev 2 E-518/10/02

27.26; 128.96;27.43; 137.64;28.08; 140.07;28.72; 142.50;ILLAWEIR ; 2.033; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;2.45; 0.00;2.49; 19.94;2.55; 56.05;2.60; 83.14;2.76; 90.24;2.93; 97.35;2.95; 115.03;3.06; 115.96;3.10; 115.97;3.12; 115.97;MINNEGAN ; 0.606; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;27.78; 0.00;27.90; 10.00;28.02; 17.70;29.10; 35.00;29.26; 52.00;29.50; 54.00;30.00; 73.00;30.60; 88.60;30.80; 91.50;33.10; 91.50;JANEWEIR ; 1.337; EXIST ;0.50; 1.00; 1.00; 0.50; 1.00; 1.00; 0; 10;11.66; 0.00;11.77; 11.35;11.88; 15.41;11.99; 16.91;12.72; 22.34;SV8507-DO-001 Rev 2 E-618/10/02

12.83; 30.14;13.88; 36.31;14.93; 41.61;15.98; 46.40;17.03; 51.18;0; Special Weir(s) ==============================0; Culvert(s) ==============================0; Q=f(t) structure(s) ==============================0; Q=Qa * f(Zb) structure(s) ==============================0; Q/H boundari(es) ==============================0; Dam Break structure(s) ==============================0; Catchment(s) ==============================0; Control Structure(s) ==============================0; User Defined structure(s) ==============================14; Culvert(s) (Q/H relations calculated) ==============================River name ; Chainage; Topo-ID;US x section; DS x section;Invert U/S; Invert D/S; Length; Manning's n; No Cul.; Valve Reg; Closed/Open4 Coefficients Pos ;;;; 4 Coefficients Neg ;;;;Shape (1:Rectangular 2:Circular 3:Irregular); Cul_Dep (= -1 if Q/h Rel not ok)Dimension array ;;;;;;;;No of irregular DimensionsDepth;Width;MINNEGAN; 0.541; EXIST;529.000; 554.000;26.820; 26.380; 23.000; 0.015; 1; 0; 0;0.50; 1.00; 0.00; 1.00; 0.50; 1.00; 0.00; 1.00;2; 1.200;1.200; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;MINNEGAN; 1.971; EXIST;1960.000; 1980.000;0.650; 0.470; 19.000; 0.015; 3; 0; 0;0.50; 1.00; 0.00; 1.00; 0.50; 1.00; 0.00; 1.00;SV8507-DO-001 Rev 2 E-718/10/02

1; 1.250;0;1.800; 1.250; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;MINNEGAN; 2.033; EXIST;2029.000; 2037.000;0.480; 0.430; 7.000; 0.015; 2; 0; 0;0.50; 1.00; 0.00; 1.00; 0.50; 1.00; 0.00; 1.00;2; 1.500;1.500; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_1; 0.016; EXIST;5.000; 26.000;22.720; 21.960; 19.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 0.750;0.750; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_1; 0.052; EXIST;26.000; 78.000;21.910; 20.420; 50.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 1.350;1.350; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_1; 0.104; EXIST;78.000; 131.000;20.370; 18.760; 50.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 1.350;1.350; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_1; 0.168; EXIST;131.000; 205.000;SV8507-DO-001 Rev 2 E-818/10/02

18.710; 17.360; 72.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 1.350;1.350; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_1; 0.221; EXIST;205.000; 236.000;17.310; 16.760; 30.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 1.350;1.350; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_1; 0.284; EXIST;236.000; 332.000;16.710; 15.450; 94.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 1.350;1.350; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_10; 0.021; EXIST;0.000; 41.000;25.460; 24.690; 40.000; 0.011; 1; 0; 0;0.50; 1.00; 0.00; 1.00; 0.50; 1.00; 0.00; 1.00;2; 1.200;1.200; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_10; 0.049; EXIST;41.000; 57.000;24.640; 24.300; 15.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 1.350;1.350; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;SV8507-DO-001 Rev 2 E-918/10/02

PIPE_10; 0.108; EXIST;57.000; 159.000;24.250; 22.150; 100.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 1.200;1.200; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;PIPE_10; 0.168; EXIST;159.000; 177.000;22.100; 21.910; 17.000; 0.011; 1; 0; 0;0.50; 1.00; 2.00; 1.00; 0.50; 1.00; 2.00; 1.00;2; 1.200;1.200; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;0;MINNEGAN; 1.337; EXIST;1335.000; 1339.000;9.850; 9.850; 2.000; 0.020; 1; 0; 0;0.50; 1.00; 0.00; 1.00; 0.50; 1.00; 0.00; 1.00;3; 1.700;0.010; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000; 0.000;7;0.00; 0.00;0.08; 2.15;0.12; 2.72;0.86; 4.12;1.42; 6.89;2.34; 10.23;0.86; 10.23;SV8507-DO-001 Rev 2 E-1018/10/02

Appendix FMIKE 11 RESULTS SUMMARYSV8507-DO-001 Rev 218/10/02

Appendix FMIKE11 RESULTS SUMMARYThis appendix is to be read in conjunction with Figure 5-1PEAK WATER LEVEL (mAHD)BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 0.000 53.79 53.57 53.53 53.50 53.43MINNEGAN 0.053 48.29 48.20 48.19 48.18 48.15MINNEGAN 0.061 48.00 47.92 47.90 47.90 47.87MINNEGAN 0.137 42.41 42.31 42.28 42.26 42.21MINNEGAN 0.137 42.41 42.31 42.28 42.26 42.21MINNEGAN 0.167 40.99 40.79 40.73 40.68 40.57MINNEGAN 0.220 39.49 39.29 39.25 39.21 39.13MINNEGAN 0.220 39.49 39.29 39.25 39.21 39.13MINNEGAN 0.285 36.13 35.77 35.70 35.65 35.53MINNEGAN 0.285 36.13 35.77 35.70 35.65 35.53MINNEGAN 0.402 32.68 32.47 32.43 32.40 32.34MINNEGAN 0.454 31.07 30.83 30.80 30.77 30.71MINNEGAN 0.525 30.63 30.36 30.33 30.30 30.22MINNEGAN 0.525 30.63 30.36 30.33 30.30 30.22MINNEGAN 0.529 30.63 30.36 30.32 30.29 30.22MINNEGAN 0.529 30.63 30.36 30.32 30.29 30.22MINNEGAN 0.554 29.11 28.70 28.63 28.58 28.45MINNEGAN 0.554 29.11 28.70 28.63 28.58 28.45MINNEGAN 0.576 28.97 28.62 28.56 28.51 28.40MINNEGAN 0.596 28.94 28.60 28.54 28.49 28.38MINNEGAN 0.596 28.94 28.60 28.54 28.49 28.38MINNEGAN 0.616 28.71 28.40 28.36 28.32 28.22MINNEGAN 0.645 28.20 27.93 27.90 27.86 27.78MINNEGAN 0.672 27.82 27.54 27.50 27.46 27.37MINNEGAN 0.672 27.82 27.54 27.50 27.46 27.37MINNEGAN 0.716 27.44 27.06 27.03 26.98 26.89MINNEGAN 0.758 27.44 27.06 27.03 26.98 26.89MINNEGAN 0.780 27.43 27.06 27.03 26.98 26.89MINNEGAN 0.780 27.43 27.06 27.03 26.98 26.89SV8507-DO-001 Rev 2 F-118/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 0.803 27.43 27.05 27.02 26.98 26.88MINNEGAN 0.813 26.67 26.54 26.51 26.49 26.43MINNEGAN 0.835 23.09 22.81 22.75 22.67 22.42MINNEGAN 0.835 23.09 22.81 22.75 22.67 22.42MINNEGAN 0.879 22.04 21.62 21.56 21.48 21.21MINNEGAN 0.887 21.93 21.56 21.49 21.42 21.14MINNEGAN 0.887 21.93 21.56 21.49 21.42 21.14MINNEGAN 0.996 20.29 19.85 19.79 19.72 19.50MINNEGAN 0.996 20.29 19.85 19.79 19.72 19.50MINNEGAN 1.009 20.08 19.68 19.62 19.55 19.41MINNEGAN 1.009 20.08 19.68 19.62 19.55 19.41MINNEGAN 1.057 18.06 17.74 17.68 17.62 17.51MINNEGAN 1.066 17.43 17.16 17.12 17.07 16.98MINNEGAN 1.086 15.09 14.29 14.14 14.01 13.79MINNEGAN 1.086 15.09 14.29 14.14 14.01 13.79MINNEGAN 1.131 14.81 13.97 13.85 13.73 13.56MINNEGAN 1.131 14.81 13.97 13.85 13.73 13.56MINNEGAN 1.225 13.03 11.86 11.66 11.43 11.02MINNEGAN 1.267 12.82 11.69 11.50 11.27 10.86MINNEGAN 1.308 12.64 11.57 11.39 11.17 10.77MINNEGAN 1.308 12.64 11.57 11.39 11.17 10.77MINNEGAN 1.335 12.57 11.53 11.35 11.13 10.76MINNEGAN 1.335 12.57 11.53 11.35 11.13 10.76MINNEGAN 1.339 10.68 9.68 9.54 9.38 9.11MINNEGAN 1.339 10.68 9.68 9.54 9.38 9.11MINNEGAN 1.382 10.04 9.05 8.91 8.75 8.49MINNEGAN 1.406 9.74 8.85 8.72 8.58 8.38MINNEGAN 1.513 7.84 6.97 6.78 6.58 6.24MINNEGAN 1.545 7.13 6.26 6.11 5.94 5.66MINNEGAN 1.584 6.56 5.74 5.61 5.41 4.95MINNEGAN 1.631 5.86 5.09 4.92 4.76 4.32MINNEGAN 1.682 4.98 4.37 4.19 4.01 3.68MINNEGAN 1.747 4.46 3.71 3.58 3.43 3.20MINNEGAN 1.747 4.46 3.71 3.58 3.43 3.20MINNEGAN 1.818 4.05 3.26 3.13 3.00 2.82MINNEGAN 1.836 3.91 3.18 3.06 2.94 2.78MINNEGAN 1.902 3.61 2.99 2.91 2.83 2.73SV8507-DO-001 Rev 2 F-218/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 1.960 3.36 2.90 2.85 2.80 2.72MINNEGAN 1.960 3.36 2.90 2.85 2.80 2.72MINNEGAN 1.980 3.35 2.89 2.85 2.80 2.72MINNEGAN 1.980 3.35 2.89 2.85 2.80 2.72MINNEGAN 1.988 3.35 2.89 2.85 2.80 2.72MINNEGAN 2.017 3.34 2.88 2.84 2.79 2.72MINNEGAN 2.029 3.32 2.88 2.84 2.79 2.72MINNEGAN 2.029 3.32 2.88 2.84 2.79 2.72MINNEGAN 2.037 3.24 2.31 2.04 1.82 1.44MINNEGAN 2.037 3.24 2.31 2.04 1.82 1.44MINNEGAN 2.048 3.24 2.30 2.03 1.81 1.40LAKEWEIR 0.529 30.63 30.36 30.32 30.29 30.22LAKEWEIR 0.554 29.11 28.70 28.63 28.58 28.45MELINDA 0.000 50.14 50.11 50.10 50.10 50.09MELINDA 0.045 44.93 44.88 44.87 44.86 44.85MELINDA 0.102 41.32 41.21 41.19 41.18 41.15MELINDA 0.117 41.32 41.21 41.19 41.17 41.14MELINDA 0.117 41.32 41.21 41.19 41.17 41.14MELINDA 0.212 33.96 33.84 33.82 33.80 33.76MELINDA 0.274 31.95 31.85 31.83 31.80 31.74MELINDA 0.282 31.45 31.38 31.37 31.36 31.35MELINDA 0.282 31.45 31.38 31.37 31.36 31.35MELINDA 0.328 30.21 30.11 30.10 30.09 30.06MELINDA 0.384 28.79 28.69 28.68 28.67 28.65MELINDA 0.427 27.44 27.06 27.03 26.98 26.89MELINDA 0.467 27.43 27.06 27.03 26.98 26.89MELINDA 0.514 27.43 27.06 27.03 26.98 26.89RANCHBY1 0.000 48.25 48.17 48.16 48.15 48.12RANCHBY1 0.045 45.34 45.25 45.24 45.23 45.21RANCHBY1 0.053 45.04 45.00 44.99 44.99 44.97RANCHBY1 0.098 42.41 42.31 42.28 42.26 42.21RANCHBY2 0.000 43.86 43.85 43.84 43.84 43.84RANCHBY2 0.044 41.77 41.64 41.62 41.60 41.56RANCHBY2 0.052 41.67 41.57 41.55 41.54 41.49RANCHBY2 0.104 39.49 39.29 39.25 39.21 39.13RANCHBY3 0.000 47.68 47.63 47.63 47.62 47.60RANCHBY3 0.049 41.94 41.85 41.83 41.81 41.78SV8507-DO-001 Rev 2 F-318/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPRANCHBY3 0.057 41.61 41.55 41.54 41.53 41.52RANCHBY3 0.104 36.13 35.77 35.70 35.65 35.53RANCHBY4 0.000 42.08 42.02 42.01 42.00 41.98RANCHBY4 0.008 41.84 41.79 41.79 41.78 41.77RANCHBY4 0.057 36.83 36.75 36.74 36.73 36.70RANCHBY4 0.107 33.89 33.75 33.73 33.71 33.66LAKEHTS2 0.000 49.31 49.25 49.24 49.23 49.22LAKEHTS2 0.136 41.52 41.42 41.40 41.39 41.36LAKEHTS2 0.243 37.55 37.48 37.47 37.46 37.44LAKEHTS2 0.289 36.11 36.02 36.00 35.97 35.90LAKEHTS2 0.345 33.89 33.75 33.73 33.71 33.66LAKEHTS2 0.345 33.89 33.75 33.73 33.71 33.66LAKEHTS2 0.415 31.34 31.18 31.16 31.15 31.06LAKEHTS2 0.463 30.63 30.36 30.33 30.30 30.22CANBERRA 0.000 23.57 23.56 23.56 23.55 23.55CANBERRA 0.080 11.79 11.69 11.67 11.66 11.62CANBERRA 0.101 9.97 9.76 9.71 9.68 9.60CANBERRA 0.155 8.11 8.02 7.99 7.97 7.93CANBERRA 0.231 4.46 3.71 3.58 3.43 3.20KARRABAH 0.000 43.12 43.09 43.07 43.06 43.03KARRABAH 0.021 42.23 42.18 42.17 42.17 42.15KARRABAH 0.043 41.32 41.21 41.19 41.17 41.14GILGAND 0.000 34.87 34.83 34.83 34.82 34.81GILGAND 0.053 31.47 31.40 31.39 31.38 31.35GILGAND 0.058 31.45 31.38 31.37 31.36 31.35DENISE1 0.005 30.53 30.47 30.46 30.45 30.42DENISE1 0.055 23.55 23.49 23.48 23.47 23.45DENISE1 0.160 17.92 17.81 17.80 17.79 17.76DENISE1 0.160 17.92 17.81 17.80 17.79 17.76DENISE1 0.170 17.91 17.81 17.79 17.78 17.75DENISE1 0.234 14.81 13.97 13.85 13.73 13.56DENISE2 0.005 32.52 32.48 32.47 32.47 32.45DENISE2 0.073 24.89 24.87 24.87 24.86 24.86DENISE2 0.133 17.92 17.81 17.80 17.79 17.76DENISE3 0.000 16.84 16.81 16.80 16.80 16.79DENISE3 0.039 12.64 11.57 11.39 11.17 10.77BARINA 0.000 38.73 38.70 38.70 38.69 38.68SV8507-DO-001 Rev 2 F-418/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPBARINA 0.018 37.83 37.80 37.80 37.79 37.78BARINA 0.046 36.52 36.47 36.47 36.46 36.45BARINA 0.078 33.65 33.58 33.57 33.56 33.54BARINA 0.181 31.10 31.03 31.02 31.02 31.00BARINA 0.307 27.82 27.54 27.50 27.46 27.37NORWEIR 1.960 3.36 2.90 2.85 2.80 2.72NORWEIR 1.980 3.35 2.89 2.85 2.80 2.72PIPE_1 0.000 27.44 27.06 27.03 26.98 26.89PIPE_1 0.005 27.44 27.06 27.03 26.98 26.89PIPE_1 0.005 27.44 27.06 27.03 26.98 26.89PIPE_1 0.026 22.51 22.51 22.51 22.51 22.51PIPE_1 0.026 22.51 22.51 22.51 22.51 22.51PIPE_1 0.078 23.09 22.81 22.75 22.67 22.42PIPE_1 0.078 23.09 22.81 22.75 22.67 22.42PIPE_1 0.131 21.93 21.56 21.49 21.42 21.14PIPE_1 0.131 21.93 21.56 21.49 21.42 21.14PIPE_1 0.205 20.29 19.81 19.75 19.67 18.20PIPE_1 0.205 20.29 19.81 19.75 19.67 18.20PIPE_1 0.236 20.08 19.69 19.62 19.54 19.41PIPE_1 0.236 20.08 19.69 19.62 19.54 19.41PIPE_1 0.332 15.09 14.29 14.14 14.01 13.79ILLAWEIR 2.029 3.32 2.88 2.84 2.79 2.72ILLAWEIR 2.037 3.24 2.31 2.04 1.82 1.44PIPE_10 0.000 28.94 28.60 28.54 28.49 28.38PIPE_10 0.041 25.07 25.07 25.07 25.07 25.07PIPE_10 0.057 24.68 24.68 24.68 24.68 24.68PIPE_10 0.159 22.57 22.57 22.57 22.57 22.57PIPE_10 0.177 22.51 22.51 22.51 22.51 22.51JANEWEIR 1.335 12.57 11.53 11.35 11.13 10.76JANEWEIR 1.339 10.68 9.68 9.54 9.38 9.11LMH69 0.000 27.44 27.06 27.03 26.98 26.89LMH69 0.003 27.43 27.06 27.03 26.98 26.89LMH70 0.000 23.09 22.81 22.75 22.67 22.42LMH70 0.003 23.09 22.81 22.75 22.67 22.42LMH70A 0.003 21.93 21.56 21.49 21.42 21.14LMH70B 0.000 20.29 19.81 19.75 19.67 18.20LMH70C 0.000 20.08 19.69 19.62 19.54 19.41SV8507-DO-001 Rev 2 F-518/10/02

PEAK DISCHARGE (m 3 /s)BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 0.026 1.86 1.09 0.97 0.89 0.69MINNEGAN 0.057 2.93 1.71 1.52 1.41 1.10MINNEGAN 0.099 3.02 1.74 1.54 1.43 1.07MINNEGAN 0.152 8.34 4.61 4.10 3.77 2.93MINNEGAN 0.193 8.33 4.48 4.00 3.65 2.86MINNEGAN 0.253 13.53 7.26 6.47 5.87 4.54MINNEGAN 0.343 15.15 8.15 7.26 6.61 5.14MINNEGAN 0.428 15.09 8.16 7.26 6.63 5.19MINNEGAN 0.490 14.74 8.09 7.19 6.57 5.16MINNEGAN 0.527 21.85 11.77 10.50 9.40 7.14MINNEGAN 0.541 0.30 0.30 0.30 0.30 0.30MINNEGAN 0.565 32.85 16.14 14.30 12.83 9.76MINNEGAN 0.586 32.74 16.24 14.38 12.89 9.74MINNEGAN 0.606 33.43 16.71 14.78 13.23 9.87MINNEGAN 0.631 33.34 16.82 14.87 13.30 9.85MINNEGAN 0.658 38.48 18.92 16.74 14.94 10.91MINNEGAN 0.694 41.15 20.10 17.72 15.70 11.42MINNEGAN 0.737 39.73 19.27 16.14 13.86 8.43MINNEGAN 0.769 39.42 18.62 16.02 13.17 6.68MINNEGAN 0.791 51.41 23.41 19.42 14.93 7.24MINNEGAN 0.808 51.40 23.54 19.34 15.06 7.22MINNEGAN 0.824 51.45 23.62 19.37 15.14 7.28MINNEGAN 0.857 52.27 23.96 19.26 15.26 7.41MINNEGAN 0.883 53.98 24.18 20.16 14.79 7.57MINNEGAN 0.941 58.56 24.94 20.08 14.98 7.50MINNEGAN 1.003 60.68 24.19 19.91 14.97 7.44MINNEGAN 1.033 61.08 24.42 19.78 14.95 7.50MINNEGAN 1.061 61.08 24.49 19.69 14.91 7.51MINNEGAN 1.076 62.09 24.70 19.82 15.01 7.62MINNEGAN 1.108 62.08 24.81 19.45 14.86 7.62MINNEGAN 1.178 67.97 26.18 20.49 15.42 8.22MINNEGAN 1.246 67.96 25.89 20.50 15.36 8.15MINNEGAN 1.288 67.94 25.61 20.45 15.36 8.10MINNEGAN 1.322 71.77 25.87 20.91 15.76 8.49MINNEGAN 1.337 54.15 25.69 20.87 15.74 8.49MINNEGAN 1.361 71.76 25.67 20.84 15.73 8.49SV8507-DO-001 Rev 2 F-618/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 1.394 71.75 25.73 20.81 15.72 8.50MINNEGAN 1.460 71.74 25.84 20.71 15.68 8.50MINNEGAN 1.529 71.73 25.97 20.50 15.56 8.49MINNEGAN 1.565 73.85 26.45 20.78 15.72 8.70MINNEGAN 1.608 73.84 26.48 20.87 15.76 8.67MINNEGAN 1.656 73.83 26.46 20.95 15.80 8.63MINNEGAN 1.715 73.81 26.17 21.00 15.82 8.65MINNEGAN 1.782 82.03 27.36 22.21 16.80 9.68MINNEGAN 1.827 82.01 27.11 22.01 16.66 9.51MINNEGAN 1.869 82.00 27.17 21.82 16.53 9.47MINNEGAN 1.931 81.98 27.14 21.52 16.38 9.41MINNEGAN 1.971 0.03 0.13 0.39 0.85 0.85MINNEGAN 1.984 85.54 27.24 21.88 16.65 9.43MINNEGAN 2.002 85.52 27.04 21.79 16.57 9.44MINNEGAN 2.023 85.51 26.93 21.75 16.52 9.44MINNEGAN 2.033 0.06 0.85 0.85 0.85 0.85MINNEGAN 2.042 85.50 26.84 21.71 16.49 9.44LAKEWEIR 0.542 31.47 15.58 13.82 12.42 9.50MELINDA 0.023 0.80 0.45 0.40 0.37 0.28MELINDA 0.073 1.86 1.08 0.96 0.88 0.68MELINDA 0.110 1.85 1.10 0.98 0.90 0.71MELINDA 0.164 5.04 2.92 2.60 2.39 1.88MELINDA 0.243 4.98 2.85 2.54 2.35 1.86MELINDA 0.278 7.00 3.82 3.36 3.06 2.45MELINDA 0.305 8.43 4.59 4.02 3.71 2.96MELINDA 0.356 8.35 4.49 4.03 3.65 2.92MELINDA 0.405 8.30 4.53 4.06 3.68 2.88MELINDA 0.447 9.45 5.27 4.77 4.48 3.59MELINDA 0.490 9.43 3.71 2.73 2.07 1.12RANCHBY1 0.023 3.27 1.84 1.64 1.52 1.20RANCHBY1 0.049 3.26 1.84 1.64 1.52 1.19RANCHBY1 0.076 4.28 2.43 2.16 1.99 1.56RANCHBY2 0.022 0.37 0.22 0.19 0.17 0.13RANCHBY2 0.048 5.19 2.78 2.46 2.27 1.82RANCHBY2 0.078 5.25 2.82 2.49 2.27 1.81RANCHBY3 0.024 0.60 0.33 0.29 0.27 0.21RANCHBY3 0.053 1.57 0.80 0.71 0.66 0.53SV8507-DO-001 Rev 2 F-718/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPRANCHBY3 0.081 1.66 0.85 0.75 0.70 0.57RANCHBY4 0.004 2.54 1.36 1.21 1.10 0.85RANCHBY4 0.032 2.54 1.41 1.26 1.15 0.89RANCHBY4 0.082 2.53 1.46 1.30 1.19 0.90LAKEHTS2 0.068 1.48 0.82 0.74 0.68 0.53LAKEHTS2 0.189 4.70 2.53 2.25 2.01 1.50LAKEHTS2 0.266 4.64 2.48 2.21 1.99 1.45LAKEHTS2 0.317 4.62 2.49 2.22 2.00 1.41LAKEHTS2 0.380 7.02 3.78 3.37 3.02 2.12LAKEHTS2 0.439 7.06 3.79 3.37 3.03 2.16CANBERRA 0.040 1.59 0.88 0.80 0.73 0.58CANBERRA 0.091 1.58 0.92 0.83 0.76 0.60CANBERRA 0.128 1.58 0.93 0.84 0.77 0.60CANBERRA 0.193 4.47 2.27 2.03 1.84 1.44KARRABAH 0.010 0.86 0.48 0.43 0.39 0.30KARRABAH 0.032 0.85 0.48 0.43 0.39 0.30GILGAND 0.026 1.29 0.73 0.65 0.59 0.45GILGAND 0.055 1.28 0.71 0.65 0.60 0.46DENISE1 0.030 0.83 0.48 0.43 0.39 0.30DENISE1 0.107 0.82 0.50 0.45 0.41 0.31DENISE1 0.165 1.78 1.02 0.92 0.84 0.65DENISE1 0.202 5.78 3.25 2.91 2.66 2.09DENISE2 0.039 0.96 0.57 0.51 0.46 0.36DENISE2 0.103 0.96 0.56 0.51 0.46 0.35DENISE3 0.019 1.47 0.81 0.73 0.66 0.52BARINA 0.009 1.78 0.99 0.88 0.80 0.62BARINA 0.032 1.78 1.00 0.89 0.81 0.63BARINA 0.062 2.70 1.52 1.36 1.23 0.94BARINA 0.130 2.69 1.58 1.41 1.28 0.99BARINA 0.244 2.74 1.62 1.45 1.33 1.02NORWEIR 1.971 85.55 27.42 21.95 16.72 9.50PIPE_1 0.003 2.90 1.49 1.33 1.21 0.99PIPE_1 0.016 0.30 0.30 0.30 0.30 0.30PIPE_1 0.052 0.60 0.60 0.60 0.60 0.60PIPE_1 0.104 0.60 0.60 0.60 0.60 0.60PIPE_1 0.168 0.60 0.60 0.60 0.60 0.60PIPE_1 0.221 0.60 0.60 0.60 0.60 0.60SV8507-DO-001 Rev 2 F-818/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPPIPE_1 0.284 0.60 0.60 0.60 0.60 0.60ILLAWEIR 2.033 85.50 26.84 21.71 16.49 9.44PIPE_10 0.021 0.30 0.30 0.30 0.30 0.30PIPE_10 0.049 0.30 0.30 0.30 0.30 0.30PIPE_10 0.108 0.30 0.30 0.30 0.30 0.30PIPE_10 0.168 0.30 0.30 0.30 0.30 0.30JANEWEIR 1.337 17.62 0.00 0.00 0.00 0.00LMH69 0.002 2.85 1.46 1.29 1.16 0.96LMH70 0.002 0.05 0.04 0.04 0.04 0.02LMH70A 0.002 0.07 0.03 0.04 0.04 0.02LMH70B 0.002 0.06 0.03 0.02 0.02 0.00LMH70C 0.002 0.04 0.04 0.03 0.04 0.03SV8507-DO-001 Rev 2 F-918/10/02

PEAK VELOCITY (m/s)BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 0.000 1.167 0.948 0.910 0.876 0.797MINNEGAN 0.026 0.526 0.399 0.375 0.358 0.307MINNEGAN 0.053 0.536 0.396 0.371 0.353 0.302MINNEGAN 0.057 1.378 1.210 1.178 1.155 1.079MINNEGAN 0.061 1.116 0.963 0.953 0.941 0.853MINNEGAN 0.099 0.626 0.568 0.546 0.533 0.479MINNEGAN 0.137 0.665 0.613 0.590 0.571 0.523MINNEGAN 0.137 1.364 1.271 1.223 1.189 1.088MINNEGAN 0.152 1.574 1.460 1.396 1.353 1.224MINNEGAN 0.167 1.775 1.640 1.555 1.498 1.333MINNEGAN 0.193 1.514 1.386 1.330 1.293 1.173MINNEGAN 0.220 0.939 0.890 0.851 0.827 0.768MINNEGAN 0.220 2.476 2.226 2.147 2.095 1.949MINNEGAN 0.253 2.128 1.832 1.757 1.693 1.550MINNEGAN 0.285 2.197 1.779 1.693 1.622 1.452MINNEGAN 0.285 2.646 2.109 2.006 1.921 1.731MINNEGAN 0.343 2.418 1.942 1.850 1.776 1.594MINNEGAN 0.402 2.323 1.855 1.768 1.701 1.534MINNEGAN 0.428 1.738 1.521 1.492 1.479 1.468MINNEGAN 0.454 1.826 1.567 1.602 1.547 1.477MINNEGAN 0.490 0.235 0.202 0.202 0.203 0.203MINNEGAN 0.525 0.121 0.079 0.072 0.066 0.053MINNEGAN 0.525 0.179 0.113 0.103 0.097 0.097MINNEGAN 0.527 0.233 0.154 0.142 0.130 0.107MINNEGAN 0.529 0.346 0.248 0.232 0.217 0.185MINNEGAN 0.529 0.000 0.014 0.015 0.016 0.016MINNEGAN 0.541 0.382 0.405 0.410 0.410 0.411MINNEGAN 0.554 0.531 0.326 0.313 0.307 0.275MINNEGAN 0.554 1.450 1.218 1.191 1.139 0.928MINNEGAN 0.565 0.934 0.726 0.692 0.655 0.552MINNEGAN 0.576 0.692 0.513 0.482 0.454 0.391MINNEGAN 0.586 0.680 0.488 0.459 0.433 0.370MINNEGAN 0.596 0.672 0.473 0.443 0.417 0.353MINNEGAN 0.596 0.680 0.480 0.450 0.423 0.355MINNEGAN 0.606 2.419 2.011 1.971 1.931 1.813MINNEGAN 0.616 0.977 0.743 0.708 0.682 0.620SV8507-DO-001 Rev 2 F-1018/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 0.631 0.865 0.649 0.613 0.586 0.510MINNEGAN 0.645 0.841 0.614 0.576 0.547 0.460MINNEGAN 0.658 2.202 1.822 1.756 1.714 1.600MINNEGAN 0.672 1.687 1.373 1.379 1.397 1.374MINNEGAN 0.672 1.824 1.526 1.512 1.510 1.443MINNEGAN 0.694 0.948 0.758 0.731 0.715 0.645MINNEGAN 0.716 0.754 0.592 0.575 0.549 0.537MINNEGAN 0.737 0.333 0.203 0.179 0.164 0.160MINNEGAN 0.758 0.246 0.144 0.124 0.116 0.116MINNEGAN 0.769 0.295 0.174 0.152 0.130 0.089MINNEGAN 0.780 0.373 0.223 0.195 0.166 0.091MINNEGAN 0.780 0.478 0.279 0.238 0.188 0.100MINNEGAN 0.791 0.489 0.344 0.297 0.242 0.135MINNEGAN 0.803 0.511 0.448 0.394 0.338 0.209MINNEGAN 0.808 1.493 1.450 1.368 1.309 1.166MINNEGAN 0.813 3.819 2.811 2.597 2.370 1.813MINNEGAN 0.824 1.737 1.472 1.402 1.281 0.985MINNEGAN 0.835 1.130 0.999 0.958 0.872 0.669MINNEGAN 0.835 1.130 0.996 0.957 0.870 0.665MINNEGAN 0.857 0.977 0.927 0.855 0.791 0.627MINNEGAN 0.879 0.936 0.752 0.737 0.750 0.603MINNEGAN 0.883 1.701 1.483 1.593 1.631 1.459MINNEGAN 0.887 1.008 0.798 0.786 0.798 0.537MINNEGAN 0.887 1.008 0.799 0.786 0.794 0.510MINNEGAN 0.941 1.028 0.839 0.767 0.679 0.578MINNEGAN 0.996 1.115 0.935 0.848 0.724 0.665MINNEGAN 0.996 1.115 0.917 0.832 0.710 0.664MINNEGAN 1.003 2.483 2.024 1.922 1.758 1.567MINNEGAN 1.009 1.457 1.039 0.963 0.869 0.691MINNEGAN 1.009 1.457 1.037 0.962 0.869 0.690MINNEGAN 1.033 1.551 1.101 1.024 0.929 0.748MINNEGAN 1.057 1.659 1.184 1.098 1.000 0.819MINNEGAN 1.061 2.243 1.672 1.563 1.439 1.191MINNEGAN 1.066 3.481 2.847 2.723 2.577 2.192MINNEGAN 1.076 2.099 1.670 1.570 1.442 1.160MINNEGAN 1.086 1.502 1.170 1.096 0.996 0.789MINNEGAN 1.086 1.501 1.167 1.094 0.995 0.786SV8507-DO-001 Rev 2 F-1118/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 1.108 1.652 1.401 1.354 1.275 1.086MINNEGAN 1.131 1.837 1.786 1.785 1.778 1.755MINNEGAN 1.131 2.359 2.231 2.222 2.209 1.974MINNEGAN 1.178 1.844 1.465 1.388 1.293 1.129MINNEGAN 1.225 1.701 1.135 1.065 0.963 0.785MINNEGAN 1.246 1.530 1.024 0.964 0.879 0.740MINNEGAN 1.267 1.391 0.931 0.874 0.804 0.705MINNEGAN 1.288 1.244 0.849 0.809 0.760 0.606MINNEGAN 1.308 1.150 0.785 0.745 0.715 0.548MINNEGAN 1.308 1.172 0.792 0.752 0.722 0.557MINNEGAN 1.322 1.175 0.658 0.589 0.509 0.345MINNEGAN 1.335 1.163 0.560 0.484 0.395 0.249MINNEGAN 1.335 0.878 0.560 0.484 0.395 0.249MINNEGAN 1.337 3.775 2.916 2.750 2.549 2.143MINNEGAN 1.339 1.692 1.464 1.348 1.208 0.950MINNEGAN 1.339 2.183 1.464 1.348 1.208 0.950MINNEGAN 1.361 2.387 1.499 1.359 1.186 0.863MINNEGAN 1.382 2.633 1.537 1.371 1.165 0.791MINNEGAN 1.394 2.536 1.737 1.609 1.447 1.112MINNEGAN 1.406 2.445 1.998 1.959 1.925 1.889MINNEGAN 1.460 2.725 2.225 2.146 2.009 1.725MINNEGAN 1.513 3.077 2.510 2.380 2.110 1.599MINNEGAN 1.529 2.765 1.993 1.851 1.688 1.392MINNEGAN 1.545 2.544 1.666 1.524 1.415 1.246MINNEGAN 1.565 2.538 1.740 1.634 1.484 1.231MINNEGAN 1.584 2.493 1.810 1.737 1.537 1.198MINNEGAN 1.608 2.711 1.903 1.799 1.604 1.351MINNEGAN 1.631 2.971 2.015 1.863 1.681 1.561MINNEGAN 1.656 2.152 1.807 1.746 1.641 1.363MINNEGAN 1.682 1.688 1.631 1.632 1.606 1.215MINNEGAN 1.715 1.534 1.390 1.362 1.292 1.038MINNEGAN 1.747 1.443 1.272 1.187 1.095 0.924MINNEGAN 1.747 1.517 1.316 1.225 1.132 1.026MINNEGAN 1.782 1.624 1.144 1.051 0.943 0.964MINNEGAN 1.818 1.695 0.996 0.904 0.793 0.840MINNEGAN 1.827 1.548 0.972 0.871 0.746 0.693MINNEGAN 1.836 1.424 0.950 0.840 0.704 0.586SV8507-DO-001 Rev 2 F-1218/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMINNEGAN 1.869 1.550 0.926 0.818 0.682 0.556MINNEGAN 1.902 1.699 0.905 0.797 0.661 0.525MINNEGAN 1.931 0.672 0.339 0.288 0.232 0.183MINNEGAN 1.960 0.432 0.210 0.175 0.141 0.088MINNEGAN 1.960 0.000 0.003 0.006 0.007 0.010MINNEGAN 1.971 0.021 0.014 0.012 0.087 0.199MINNEGAN 1.980 0.002 0.001 0.001 0.001 0.002MINNEGAN 1.980 0.279 0.130 0.109 0.088 0.054MINNEGAN 1.984 0.305 0.142 0.120 0.096 0.060MINNEGAN 1.988 0.337 0.157 0.132 0.106 0.066MINNEGAN 2.002 0.431 0.209 0.176 0.141 0.088MINNEGAN 2.017 0.600 0.317 0.267 0.212 0.131MINNEGAN 2.023 0.696 0.390 0.334 0.271 0.170MINNEGAN 2.029 0.830 0.507 0.446 0.373 0.241MINNEGAN 2.029 0.002 0.010 0.011 0.010 0.010MINNEGAN 2.033 0.130 0.349 0.411 0.452 0.520MINNEGAN 2.037 0.003 0.007 0.009 0.011 0.034MINNEGAN 2.037 0.614 0.571 0.647 0.718 1.288MINNEGAN 2.042 0.621 0.559 0.629 0.690 1.129MINNEGAN 2.048 0.627 0.547 0.611 0.663 1.005LAKEWEIR 0.529 0.411 0.283 0.264 0.247 0.211LAKEWEIR 0.542 2.139 1.804 1.755 1.709 1.613LAKEWEIR 0.554 1.383 1.162 1.134 1.090 0.904MELINDA 0.000 1.305 1.009 0.959 0.919 0.815MELINDA 0.023 1.156 0.894 0.851 0.814 0.720MELINDA 0.045 2.431 1.889 1.791 1.716 1.518MELINDA 0.073 0.794 0.626 0.592 0.567 0.504MELINDA 0.102 0.529 0.424 0.401 0.386 0.344MELINDA 0.110 0.403 0.340 0.326 0.317 0.291MELINDA 0.117 0.586 0.502 0.485 0.474 0.443MELINDA 0.117 0.751 0.640 0.619 0.604 0.563MELINDA 0.164 0.765 0.638 0.614 0.597 0.553MELINDA 0.212 0.633 0.517 0.497 0.483 0.446MELINDA 0.243 0.501 0.439 0.422 0.412 0.382MELINDA 0.274 0.565 0.501 0.468 0.458 0.428MELINDA 0.278 1.605 1.324 1.291 1.291 1.291MELINDA 0.282 1.881 1.470 1.406 1.351 1.226SV8507-DO-001 Rev 2 F-1318/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPMELINDA 0.282 2.225 1.745 1.650 1.597 1.454MELINDA 0.305 1.585 1.254 1.182 1.145 1.043MELINDA 0.328 1.216 0.958 0.907 0.879 0.803MELINDA 0.356 1.365 1.065 1.016 0.972 0.886MELINDA 0.384 1.561 1.225 1.160 1.100 0.991MELINDA 0.405 0.977 0.798 0.810 0.838 0.811MELINDA 0.427 0.882 0.831 0.805 0.807 0.821MELINDA 0.447 0.641 0.595 0.549 0.508 0.627MELINDA 0.467 0.517 0.619 0.553 0.442 0.677MELINDA 0.490 0.529 0.417 0.403 0.377 0.275MELINDA 0.514 0.332 0.333 0.291 0.218 0.166RANCHBY1 0.000 0.819 0.665 0.639 0.621 0.622RANCHBY1 0.023 0.722 0.681 0.676 0.674 0.610RANCHBY1 0.045 0.718 0.713 0.735 0.735 0.643RANCHBY1 0.049 1.367 1.209 1.170 1.143 1.084RANCHBY1 0.053 1.286 1.022 0.977 0.951 0.869RANCHBY1 0.076 0.975 0.874 0.839 0.817 0.750RANCHBY1 0.098 0.771 0.661 0.636 0.620 0.572RANCHBY2 0.000 0.615 0.513 0.496 0.480 0.439RANCHBY2 0.022 0.104 0.088 0.087 0.086 0.082RANCHBY2 0.044 0.677 0.566 0.546 0.547 0.542RANCHBY2 0.048 1.567 1.361 1.313 1.295 1.245RANCHBY2 0.052 1.476 1.252 1.210 1.338 1.350RANCHBY2 0.078 0.798 0.713 0.688 0.671 0.630RANCHBY2 0.104 1.624 1.446 1.391 1.358 1.268RANCHBY3 0.000 1.861 1.406 1.328 1.269 1.131RANCHBY3 0.024 0.155 0.134 0.130 0.127 0.109RANCHBY3 0.049 0.210 0.148 0.144 0.141 0.134RANCHBY3 0.053 1.190 1.104 1.104 1.103 1.103RANCHBY3 0.057 1.160 0.973 0.946 0.926 0.886RANCHBY3 0.081 0.421 0.337 0.324 0.314 0.292RANCHBY3 0.104 0.449 0.341 0.324 0.315 0.289RANCHBY4 0.000 1.958 1.475 1.400 1.340 1.193RANCHBY4 0.004 1.102 0.874 0.840 0.813 0.749RANCHBY4 0.008 0.767 0.623 0.602 0.585 0.752RANCHBY4 0.032 0.752 0.647 0.641 0.651 0.611RANCHBY4 0.057 0.737 0.624 0.616 0.628 0.586SV8507-DO-001 Rev 2 F-1418/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPRANCHBY4 0.082 0.643 0.550 0.521 0.520 0.495RANCHBY4 0.107 0.587 0.479 0.444 0.439 0.421LAKEHTS2 0.000 0.697 0.601 0.572 0.803 0.657LAKEHTS2 0.068 0.307 0.268 0.262 0.264 0.247LAKEHTS2 0.136 0.658 0.547 0.531 0.532 0.534LAKEHTS2 0.189 0.856 0.705 0.681 0.667 0.634LAKEHTS2 0.243 1.526 1.238 1.227 1.168 1.105LAKEHTS2 0.266 1.476 1.245 1.204 1.161 1.047LAKEHTS2 0.289 2.534 2.261 2.196 2.105 1.812LAKEHTS2 0.317 1.309 1.064 1.022 0.978 0.849LAKEHTS2 0.345 1.444 1.103 1.052 1.006 0.880LAKEHTS2 0.345 1.989 1.534 1.455 1.396 1.212LAKEHTS2 0.380 1.859 1.624 1.575 1.534 1.358LAKEHTS2 0.415 2.571 2.488 2.574 2.579 2.358LAKEHTS2 0.439 0.193 0.169 0.164 0.151 0.149LAKEHTS2 0.463 0.073 0.073 0.071 0.067 0.066CANBERRA 0.000 0.417 0.416 0.416 0.416 0.416CANBERRA 0.040 1.080 0.890 0.872 0.866 0.804CANBERRA 0.080 0.332 0.333 0.333 0.334 0.334CANBERRA 0.091 0.761 0.616 0.593 0.576 0.532CANBERRA 0.101 0.484 0.390 0.374 0.362 0.333CANBERRA 0.128 0.420 0.374 0.360 0.351 0.321CANBERRA 0.155 0.737 0.586 0.584 0.581 0.579CANBERRA 0.193 0.328 0.295 0.307 0.313 0.298CANBERRA 0.231 0.209 0.194 0.246 0.250 0.238KARRABAH 0.000 1.584 1.307 1.227 1.161 1.001KARRABAH 0.010 1.717 1.359 1.277 1.211 1.047KARRABAH 0.021 1.873 1.408 1.325 1.258 1.088KARRABAH 0.032 0.302 0.260 0.252 0.248 0.235KARRABAH 0.043 0.168 0.147 0.144 0.142 0.135GILGAND 0.000 1.874 1.444 1.373 1.316 1.158GILGAND 0.026 1.180 0.845 0.790 0.745 0.641GILGAND 0.053 0.855 0.587 0.552 0.522 0.433GILGAND 0.055 0.496 0.387 0.364 0.351 0.318GILGAND 0.058 0.356 0.294 0.279 0.272 0.254DENISE1 0.005 0.740 0.617 0.595 0.714 0.698DENISE1 0.030 0.648 0.557 0.535 0.516 0.471SV8507-DO-001 Rev 2 F-1518/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPDENISE1 0.055 0.576 0.486 0.592 0.447 0.405DENISE1 0.107 0.236 0.217 0.214 0.212 0.204DENISE1 0.160 0.156 0.168 0.158 0.153 0.145DENISE1 0.160 0.296 0.300 0.288 0.280 0.268DENISE1 0.165 0.263 0.255 0.240 0.229 0.210DENISE1 0.170 0.770 0.617 0.592 0.572 0.527DENISE1 0.202 0.713 0.649 0.641 0.640 0.604DENISE1 0.234 1.532 1.333 1.320 1.328 1.239DENISE2 0.005 0.571 0.522 0.658 0.652 0.454DENISE2 0.039 0.597 0.520 0.506 0.496 0.471DENISE2 0.073 0.641 0.560 0.546 0.557 0.510DENISE2 0.103 0.250 0.238 0.232 0.230 0.224DENISE2 0.133 0.155 0.150 0.146 0.145 0.142DENISE3 0.000 1.573 1.398 1.318 1.162 1.060DENISE3 0.019 0.205 0.115 0.110 0.108 0.098DENISE3 0.039 0.108 0.064 0.061 0.060 0.054BARINA 0.000 0.960 0.761 0.729 0.702 0.635BARINA 0.009 0.946 0.752 0.720 0.694 0.628BARINA 0.018 0.932 0.743 0.712 0.686 0.622BARINA 0.032 1.229 0.976 0.932 0.898 0.810BARINA 0.046 2.242 1.751 1.666 1.597 1.421BARINA 0.062 2.012 1.554 1.483 1.420 1.261BARINA 0.078 1.589 1.230 1.174 1.126 1.000BARINA 0.130 1.916 1.481 1.396 1.318 1.149BARINA 0.181 2.441 1.807 1.682 1.549 1.306BARINA 0.244 0.637 0.464 0.428 0.498 0.489BARINA 0.307 0.387 0.294 0.271 0.301 0.304NORWEIR 1.960 0.437 0.210 0.176 0.142 0.088NORWEIR 1.971 0.616 0.310 0.262 0.836 0.836NORWEIR 1.980 0.279 0.131 0.110 0.088 0.057PIPE_1 0.000 0.333 0.180 0.168 0.163 0.143PIPE_1 0.003 0.331 0.179 0.166 0.162 0.142PIPE_1 0.005 0.329 0.178 0.165 0.161 0.141PIPE_1 0.005 0.026 0.010 0.010 0.012 0.008PIPE_1 0.016 0.843 0.810 0.807 0.803 0.794PIPE_1 0.026 0.000 0.000 0.000 0.000 0.000PIPE_1 0.026 0.000 0.000 0.000 0.000 0.000SV8507-DO-001 Rev 2 F-1618/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPPIPE_1 0.052 0.290 0.292 0.292 0.292 0.292PIPE_1 0.078 0.006 0.004 0.004 0.004 0.002PIPE_1 0.078 0.054 0.038 0.031 0.027 0.037PIPE_1 0.104 0.317 0.334 0.335 0.338 0.351PIPE_1 0.131 0.006 0.002 0.003 0.003 0.001PIPE_1 0.131 0.078 0.076 0.075 0.078 0.052PIPE_1 0.168 0.340 0.357 0.357 0.354 0.351PIPE_1 0.205 0.008 0.004 0.003 0.003 0.000PIPE_1 0.205 0.069 0.047 0.041 0.036 0.008PIPE_1 0.221 0.207 0.234 0.234 0.235 0.235PIPE_1 0.236 0.002 0.002 0.001 0.001 0.001PIPE_1 0.236 0.080 0.051 0.049 0.046 0.041PIPE_1 0.284 0.370 0.354 0.351 0.348 0.342PIPE_1 0.332 0.007 0.031 0.034 0.035 0.035ILLAWEIR 2.029 0.830 0.506 0.446 0.373 0.241ILLAWEIR 2.033 1.480 1.460 1.370 1.263 1.074ILLAWEIR 2.037 1.251 1.686 1.601 1.414 1.142PIPE_10 0.000 0.112 0.076 0.077 0.062 0.078PIPE_10 0.021 0.519 0.496 0.492 0.488 0.481PIPE_10 0.041 0.000 0.000 0.000 0.000 0.000PIPE_10 0.049 0.267 0.267 0.267 0.267 0.267PIPE_10 0.057 0.000 0.000 0.000 0.000 0.000PIPE_10 0.108 0.243 0.243 0.243 0.243 0.243PIPE_10 0.159 0.000 0.000 0.000 0.000 0.000PIPE_10 0.168 0.105 0.105 0.105 0.105 0.105PIPE_10 0.177 0.000 0.000 0.000 0.000 0.000JANEWEIR 1.335 0.285 0.000 0.000 0.000 0.000JANEWEIR 1.337 2.148 0.000 0.000 0.000 0.000JANEWEIR 1.339 0.536 0.026 0.026 0.026 0.026LMH69 0.000 2.854 1.462 1.288 1.162 0.956LMH69 0.002 0.205 0.109 0.103 0.104 0.096LMH69 0.003 2.854 1.462 1.288 1.162 0.956LMH70 0.000 0.050 0.042 0.041 0.039 0.016LMH70 0.002 0.056 0.037 0.037 0.037 0.018LMH70 0.003 0.050 0.042 0.041 0.039 0.016LMH70A 0.000 0.072 0.032 0.036 0.042 0.015LMH70A 0.002 0.455 0.296 0.495 0.304 0.265SV8507-DO-001 Rev 2 F-1718/10/02

BRANCH CHAINAGE PMF 1% AEP 2% AEP 5% AEP 20% AEPLMH70A 0.003 0.072 0.032 0.036 0.042 0.015LMH70B 0.000 0.057 0.030 0.018 0.024 0.000LMH70B 0.002 0.616 0.496 0.470 0.456 0.000LMH70B 0.003 0.057 0.030 0.018 0.024 0.000LMH70C 0.000 0.039 0.042 0.024 0.033 0.035LMH70C 0.002 0.097 0.145 0.080 0.077 0.083LMH70C 0.003 0.039 0.042 0.024 0.033 0.035SV8507-DO-001 Rev 2 F-1818/10/02