Loders Creek Catchment Hydraulic Study · Version 4 – August 18 TRACKS-#45330050-v4-LODERS_CREEK_HYDRAULIC_STUDY_2015 Page 3 of 72 Executive Summary The Loders Creek catchment is

1

Loders Creek Catchment

Hydraulic Study August 2016

Version 4 – August 18 TRACKS-#45330050-v4-LODERS_CREEK_HYDRAULIC_STUDY_2015 Page 2 of 72

Title: Loders Creek Catchment Hydraulic Study

Author:

Study for: City Planning Branch

Planning and Environment Directorate

The City of Gold Coast

File Reference: WF28/44/01(P4)

TRACKS #45330050

Version history

Version Comments/Change Changed by

& date Reviewed by &

date

1.0 Draft

2.0 Update DTM

3.0 Edited

4.0 Edited

Distribution list

Name Title Directorate Branch


Executive Summary

The Loders Creek catchment is the smallest catchment (9.6km2) on the Gold Coast which experiences regional flooding. Loders Creek drains into the Broadwater system and contains small tributaries which are susceptible to breaches during heavy downpours. Loders Creek contains a small embankment dam which was constructed in the early 1970’s to mitigate flooding impacts in the lower reaches and to allow further urbanisation of the Broadwater foreshore. This Loders Creek catchment hydraulic study is the result of numerous studies undertaken over a number of years to determine a flood planning level for the catchment. This study’s output is an updated Loders Creek hydraulic model which has been used to develop a flood map for the City of Gold Coast’s City Plan 2015 designated flood level (DFL).

DHI’s MIKE software suites have been used to build the hydraulic model. MIKE21 calculates complex flows and represents floodplain storage in the 2D domain whilst MIKE11 represents flow constrictions of hydraulic structures in the 1D domain. MIKE Flood was used to combine the two dynamic software platforms of MIKE21 and MIKE11. This combination is appropriate for Loders Creek as it consists of numerous structures (weirs, culverts and bridges), as well as an embankment dam. The MIKE21 2D topographical terrain is a 5m rectangular grid created from Council’s 2012 2m Digital Terrain Model (DTM) and is of sufficient size to represent the small tributaries. This DTM is a combination of Aerial Laser Survey (ALS) data conducted in 2011-12 and bathymetric surveys from various years.

The hydraulic model of Loders Creek has been calibrated to the June 2005 historical flood event and verified against the January 2008 and January 2013 historical flood events at two ALERT station locations. The historical flood event simulations undertaken by the model produced reasonable replication of recorded water levels throughout the catchment.

This calibrated model has been used to simulate design flood events ranging from a 2 year Average Recurrence Interval (ARI) flood event to a Probable Maximum Flood (PMF). The design runs include storm durations of 0.5, 1.0, 1.5, 3.0, 4.5, 6.0, 9.0, 12.0, 18.0, 24.0, 36.0, 48.0, 72.0 hours. The hydrology of this study for both calibration and design events are sourced from the Loders Creek Hydrological Study 2014 (Ref 17). This hydrologic study has been strongly peer reviewed by leading industry experts.

The hydraulic model described in this report has been used to develop the DFL for the Loders Creek Catchment. Its results will be adopted in the 2015 City Plan Major Update 2 (Resolution G16.0726.020) as the new flood planning map.


Table of Contents

Executive Summary ............................................................................................................................. 3

1 Introduction ................................................................................................................................... 8

1.1 Overview .............................................................................................................................. 8

1.2 2003 Flood Planning Level .................................................................................................. 8

1.3 Assumptions and Limitations ............................................................................................... 8

1.4 Acknowledgement ............................................................................................................... 9

2 Background ................................................................................................................................. 10

2.1 Catchment Description ...................................................................................................... 10

2.2 Previous Studies ................................................................................................................ 12

2.3 Previous Studies Continued .............................................................................................. 13

3 Hydraulic Model Development ................................................................................................... 14

3.1 Overview ............................................................................................................................ 14

3.2 Software Modelling Choice ................................................................................................ 14

3.3 Software Version ............................................................................................................... 14

3.4 Hydrology ........................................................................................................................... 14

3.5 Hydraulic Modelling Approach ........................................................................................... 15

3.6 Datum ................................................................................................................................ 15

3.7 Hydraulic Model Extent ...................................................................................................... 16

3.8 Input Locations .................................................................................................................. 17

3.9 Tailwater Conditions .......................................................................................................... 18

3.10 Storm Surge Conditions ..................................................................................................... 18

3.11 Digital Elevation Model ...................................................................................................... 19

3.12 Bathymetric Surveys .......................................................................................................... 20

3.13 Model Parameters ............................................................................................................. 21

3.13.1 Floodplain Roughness ......................................................................................... 21

3.13.2 Eddy Viscosity ...................................................................................................... 23

3.13.3 Flooding and Drying ............................................................................................. 23

3.14 Structures .......................................................................................................................... 24

3.14.1 Hydraulic Structures Not in Model ........................................................................ 24

3.14.2 Culvert Data ......................................................................................................... 25

3.14.3 Bridge Data .......................................................................................................... 26

3.14.4 Bridge Set up ....................................................................................................... 28

4 Model Calibration and Verification ............................................................................................ 29

4.1 ALERT Stations ................................................................................................................. 29

4.2 Maximum Height Gauges and Historical Debris Mark ....................................................... 29

4.3 June 2005 Calibration ........................................................................................................ 31

4.4 January 2008 Calibration ................................................................................................... 34

4.5 January 2013 Calibration ................................................................................................... 35


5 Calibration Summary .................................................................................................................. 36

6 Design Floods .............................................................................................................................. 37

6.1 Introduction ........................................................................................................................ 37

6.2 Initial Water Level .............................................................................................................. 38

6.3 Design Run Setup .............................................................................................................. 39

6.4 Probable Maximum Flood .................................................................................................. 39

7 Analysis of Design Events ......................................................................................................... 40

7.1 Critical Duration ................................................................................................................. 40

7.2 Maximum Water Level ....................................................................................................... 40

8 Conclusion ................................................................................................................................... 41

9 Recommendations ...................................................................................................................... 42

10 References ................................................................................................................................... 43

Appendix A Semidiurnal Tidal Planes - 2014 ............................................................................ 44

Appendix B – Loders Creek Structures ........................................................................................... 45

Musgrave Avenue ....................................................................................................................... 45

Smith Street Culverts .................................................................................................................. 46

Johnston Street Bridge (BR3) ..................................................................................................... 47

Southport Primary School Pedestrian Bridge (BR4) ................................................................... 48

Baratta Street Weir (WE1) .......................................................................................................... 49

Jackman Street Weir (WE2) ....................................................................................................... 49

Queen Street Culverts (CU2) ...................................................................................................... 50

Bambarra Street Culverts (CU3) ................................................................................................. 51

Prince Street Culverts (CU4) ...................................................................................................... 52

Ward Street Culverts (CU5) ........................................................................................................ 53

Falconer Street Culvert (CU6) .................................................................................................... 54

Minnie Street Culverts (CU7) ...................................................................................................... 55

Southport Nerang Road Culverts 1 (CU8) .................................................................................. 56

Nyora Street Pedestrian Bridge (BR5) ........................................................................................ 57

Dandar Street Culverts (CU9) ..................................................................................................... 58

Kindra Street Stilling Basin (ST1) ............................................................................................... 59

Middleton Street Detention Basin (BA2) ..................................................................................... 59

Wardoo Street Culverts 1 (CU10) ............................................................................................... 60


Baratta Street Culverts (CU12) ................................................................................................... 62


Edmund Rice Drive Culverts (CU14) .......................................................................................... 64

Southport Nerang Road Culverts 2 (CU15) ................................................................................ 64

Southport Nerang Road Pedestrian Bridge (BR6) ...................................................................... 65

Dominions Road Pedestrian Bridge (BR6) ................................................................................. 65

Turpin Road Culverts (CU16) ..................................................................................................... 66


Musgrave Avenue Culverts (CU17) ............................................................................................ 67

Barrett Avenue Culverts (CU18) ................................................................................................. 68

Neville Avenue Pedestrian Bridge (BR7) .................................................................................... 69

Gold Coast Highway Bridge Northbound (BR5) .......................................................................... 70

Loders Hydraulic Study 2015 Natural Hazards Planning & Environment Directorate


LIST OF ABBREVIATIONS

AHD Australian Height Datum

AEP Annual Exceedance Probability

AFC Acceptable Flood Capacity

ALS Aerial Laser Survey

ARI Annual Recurrence Interval (similar to Return Period - years) ARR Australian Rainfall and Runoff Guidelines Engineers Australia

BOM Bureau of Meteorology

DEWS Department of Energy and Water Supply

DTM Digital Terrain Model

Assets City Assets Branch (City Infrastructure Directorate)

CoGC City of Gold Coast

GIS Geographic Information System

IFD Intensity Frequency Duration (design rainfall data)

LDG Land Development Guidelines (2005 edition)

MHG Maximum Height Gauge

MHWS Mean High Water Spring

NH Natural Hazards Team (Planning and Environment Directorate)

PAR Population at Risk

PET Planning and Environment Directorate

PMF Probable Maximum Flood

PMPDF Probable Maximum Precipitation Design Flood

QUDM Queensland Urban Drainage Manual (2007 edition)

RL Reduced Level (m) (in this report in AHD unless stated otherwise)

SDMS Stormwater Drainage Management Strategy

SDS Stormwater Drainage Study

TWL Tail-water Level (the downstream boundary for backwater analysis)



1 Introduction

1.1 Overview

The Natural Hazards team has updated its Loders Creek hydraulic model for use in the development of the City of Gold Coast’s (City) designated flood level (DFL) for the City Plan.

This report documents the most recent (at time of writing) hydraulic modelling methodology, its data sources and the calibration results for the Loders Creek Catchment.

1.2 2003 Flood Planning Level

Previously, the Danish Hydraulic Institutes software platform MIKE11 modelled the Loders Creek catchment to establish flood planning levels for the area in 2003. MIKE11 is a one-dimensional model with the ability to simulate riverine flooding by using hydrologic inputs, interpolated cross-sections and set boundary conditions. It is excellent at simulating design runs and historical rainfall events very quickly whilst producing reasonably accurate results.

In 2003, MIKE 11 simulated the then DFL scenario (which was a 1 in 100 year flood with a 1 in 100 year triangulated storm surge) and produced elevation points along Loders Creek. The elevations produced by MIKE 11 were compared to the Digital Elevation Model of the Loders catchment and any topography below the elevation point produced by MIKE 11 was considered to be flooded. The end result from the GIS interpretation produced the flood map which is contained within the 2003 Planning Scheme for the Loders catchment area. Since this time, technology has improved and the flood map for this catchment requires updating.

1.3 Assumptions and Limitations

The development of this Loders Creek Hydraulic Study had the following assumptions and limitations:

1 Information Use

The preparation of this hydraulic assessment report is based on available information at the time of writing.

The analysis and overall approach adopted by this study is specifically prepared for internal use and it is not applicable beyond this scope. For this reason, third parties are not authorised to use any contents from this report unless written approval has been obtained from City of Gold Coast Council.

City of Gold Coast believes the assessment is accurate for its intended purpose and disclaims any responsibility for any loss or damage suffered as a result of placing reliance upon information provided in this report.

2 Model Grid (DEM)

The model grid is based on the airborne laser survey conducted between July 2011 and July 2012. Any development or changes to the model grid after this date is not documented in this report.



Furthermore, the airborne laser-survey data acquisition and post-processing has been controlled to achieve a vertical accuracy of about 0.15m (rms) and horizontal accuracy of about 0.45m.

Bathymetric data is captured by hydrographical surveys conducted in 2003 and 2012.

The horizontal coordinates use Map Grid of Australia (MGA) Zone 56 projection.

The vertical coordinates are referenced to Australian Height Datum (AHD) 1992.

3 Hydraulic Model

The hydraulic model does not include the stormwater drainage system (i.e. pipe culverts, inlet pits, etc.) which may influence local flooding paths and local inundation.

Modelled bridges use the Energy Equation to determine hydraulic losses

The embankment dam within Loders Creek is modelled in MIKE 21 by the DEM and the low flow pipe in MIKE11

Cross-sections are modelled by Total Hydraulic Radius and Distributed flow coefficients

4 Hydrologic Model

Calibrated URBS model outputs are used from the 2014 Loders Hydrology Study

Catchments are routed specifically for hydraulic model input

Local Hydrographs were printed at the centroid of individual catchments for hydraulic input

1.4 Acknowledgement

The City would like to acknowledge the Bureau of Meteorology and Marine Safety

Queensland for providing calibration data for this study.



2 Background

2.1 Catchment Description

Loders Creek is located in the eastern quadrant of the Gold Coast City boundary and is part of the larger Broadwater catchment. It is approximately 7.3 km in length with a catchment area of approximately 9.6km2. Loders Creek originates in the foothills of Ashmore and winds through the suburbs of Southport and Labrador until it discharges into the reaches of the Broadwater. The catchment is heavily urbanised with some remnants of native vegetation near Southport Primary and the retardation basin in Ashmore. Most of the inflow into the creek is from stormwater drainage systems which capture runoff from surrounding urban and industrial impervious areas. The Broadwater foreshore has a coastal nature with many tourist accommodations and recreational areas. Due to its low elevation, storm surge predominately affects the Broadwater area. (Ref 1, 3)

The Loders Creek catchment has many physical mitigation measures which reduce the impacts of flooding. These physical measures consist of concrete lined channels to expedite flows to the ocean, detention basins and a low flow embankment dam which attenuates upstream rainfall runoff. Council implemented these mitigation measures due to urbanisation of the Broadwater area in the mid 1970’s and upgraded the embankment dam’s outlet pipes after the 1974 flood event. The embankment dam approximately holds 686ML of water and has a spillway crest of approximately 11.8mAHD. The crest is a graded crest which increases from 13mAHD to 18mAHD. The dam takes approximately 19 hours to empty after reaching the spillway. The concrete-lined channels constructed in the 70’s also improve the conveyance of flood waters through urbanised areas and ‘conveniently reduce the ongoing maintenance costs’ to Council (Ref 2).

Figure 1 depicts the delineation of the catchment. All areas inside the blue line contribute runoff to the Loders Creek system. This delineation has been based on LiDAR information in which all terrain elevations were calculated to allow water transportation to the outlet. The greater City of Gold Coast boundary delineation (at the top right of Figure 1) is inset to emphasize the size of the catchment in retrospect to the entire City’s boundary.



Figure 1 Loders Creek Catchment.



2.2 Previous Studies

Gold Coast City Council’s first report on Loders Creek was completed in March 1968. Titled ‘Preliminary Report - Investigation of Flooding in Loders Creek, Southport’, this report investigated the options for flood mitigation through several retardation basin schemes and included calculations of a Q40 design event storm and assessment of the June 1967 event.

Munro, Johnston and Associates Pty Ltd completed a Loders Creek Flood Study in August 1974. This major study included unit hydrographs derived using Clarke – Johnston methods for the January 1972 and January 1974 events as well as determining the Q5, Q10, Q20, Q50 and Q100 design events. The report is thorough and includes details for all calculations, including details on temporal patterns and historical information such as creek water levels during the 1967 and 1974 events. Preliminary design information of the retardation basin is included as well as extent profiles of Loders Creek if it were to experience the 1967 and Q100 events. This report specifies levels in State datum.

In April 1983, Munro Johnston and Associates Pty Ltd examined the feasibility of extending the outlet conduit of the Loders Creek Retardation Basin (Gold Coast City Council Loders Creek Retardation Basin, Report on Feasibility of Extension of Outlet Conduit, Munro, Johnston and Associates Pty Ltd, April 1983). The basin revaluation took advantage of improvements in hydrological modelling techniques developed since the original basin design in 1974. The run-off routing model RORB was used to estimate flood hydrographs and the report provides details of basin peak water levels and discharges for the PMP, Q100 and October 1972, March 1974 and March 1976 events. Plans of the retardation basin and the new discharge outlet were provided as well as its corresponding level- discharge curve.

In January 2003, Technical Services completed the Upper Loders Creek- Channel Naturalisation Feasibility Study. As part of the study, a hydrological and hydraulic assessment was undertaken of the existing channel between Olsen Avenue and Edmund Rice Drive, Southport (upstream of the Loders Creek Retardation Basin). This study assessed the impacts on flooding due to revegetating a section of Loders Creek. The affects were minimal.



2.3 Previous Studies Continued

Loders Creek Gold Coast City Council. Dam Break Analysis Report. March 2004. ##22012088

Hydraulic modelling (Mike11) was undertaken for Loders Creek to assess the impact of flooding if the embankment dam were to break. This study covers three dam break scenarios coinciding with a Probable Maximum Flood (PMF) and a dam break scenario of ‘on a sunny day’. This study found that Loders Flood Mitigation Dam does pose a significant threat to the residential properties downstream of the dam.

Gold Coast City Council. Loders Creek Catchment Study. Hydraulic Report. Flood. January 2004. Ref. 3. ##22842119

This report was prepared, as part of three reports (Ref #22012079 [17] and Ref #22012088), for a Dam Break Assessment based on Engineering Services’ request. A MIKE 11 model was built which incorporated the Loders Creek Retardation Basin and 15 hydraulic structures. The model was setup for the 20, 50, 100, 200 and 500 year ARI as well as PMF that was sourced from the hydrological study (#22012079 [17]). The Study also conducted a hydrological review and dam break study as mentioned previously.



3 Hydraulic Model Development

3.1 Overview

A MIKE flood model requires hydrologic, structural and topographic information to enable simulations of water movement. The following section describes in detail the inputs and constraints within the Loders Creek MIKE Flood hydraulic model. It also describes briefly the methodologies.

3.2 Software Modelling Choice

Due to the numerous concrete lined channels, culverts and intricate bridges incorporated within the Loders Creek catchment, a sophisticated software platform was required to model riverine flooding of Loders Creek. DHI’s MIKE Flood was chosen to model Loders Creek due to its ability to simulate complex floodplains and canal systems using hydro-dynamically coupled two-dimensional topography grids with one-dimensional hydraulic structures. Simply speaking, MIKE Flood was able to represent hydraulic structures of bridges and culverts one dimensionally in MIKE 11 whilst simulating the hydrodynamics of overland flow in MIKE 21. Once the structures and topography are specified, the two software platforms can be dynamically coupled.

3.3 Software Version

At the time of development of the Loders Creek hydraulic model, MIKE FLOOD 2014 with Service Pack 3 was the software package used. Upgrading the model to newer versions of MIKE Flood may require the MIKE 11 network file be opened and resaved or file path restructuring.

3.4 Hydrology

The hydraulic model hydrologic inputs are based on a hydrology review project undertaken by Natural Hazards in 2014 (Ref 17). The following are of note to this 2014 study:

The 2014 URBS hydrological model is acceptable to use for hydraulic model simulation due to its calibration to the January 2008, January 2013 and June 2005 flood events.

The URBS model produces inflow hydrographs from Q2 to PMP AWE2000 Temporal Patterns α (Channel Lag Parameter) = 0.2 β (Catchment Lag Parameter) = 2.0 m (catchment non-linearity parameter) = 0.8 Varying initial and continuing losses based on ARI Urbs32.exe version last edited 9/08/2009 3:31pm Rating curves developed during this study are yet to be verified with BOM A sufficient record of historical peak height or discharge data was not available to

undertake a flood frequency analysis (FFA) at any of the two stream gauging stations within the Loders Creek catchment.



3.5 Hydraulic Modelling Approach

The approach undertaken was to calibrate a hydraulic model to real flood events for the Loders Creek system using a reputable software platform, i.e. the MIKE Flood software (2014, Service Pack 3) and to simulate a combination of design flood events to attain the DFL.

MIKE Flood is capable of simulating complex flows and floodplain storage in the 2D topographical terrain (using MIKE 21 grid) and is able to provide flow constriction of hydraulic structures (using MIKE 11 structures). This combination is very useful, as the Loders floodplain consists of numerous structures (weirs, culverts and bridges) as well as the numerous river and canal systems.

The local stormwater drainage systems (i.e. the culvert pipes, inlet pits, grates etc.) are not included in this model as they have a relatively small impact on the regional flooding behaviour.

3.6 Datum

Figure 2 Map Grid of Australia

5 Horizontal Datum

The horizontal coordinates use Map Grid of Australia (MGA) Zone 56 projection.

6 Vertical Datum

The vertical coordinates are referenced to Australian Height Datum (AHD) 1992.



3.7 Hydraulic Model Extent

The following figure demonstrates the model Extent of the Loders Creek MIKE FLOOD model (red outline).

Figure 3 Loders Model Extent

The area of concern for this study is the area contained within the red line. All areas represented outside this blue line are ignored during simulations. The MIKE 21 component of the hydraulic model does this by assigning cells a value of ‘land’. For this study the land value is set at 30.



3.8 Input Locations

The Loders hydraulic model has three model boundaries: two of them are hydrologic input locations (TH_SC6 & TH_SC1) and the other is a tidal boundary. The tidal boundary is either sourced from the Gold Coast Seaway ALERT station using recorded data or by using Maritime Safety Queensland semidiurnal tidal planes. Total Hydrographs of SC6 and SC1 were chosen in the upper reaches to minimise the impact of placing a local hydrograph within an urban area.

For model stability, a hole is dug in the DEM at these boundary inflows to create a pond. This pond ensures that the model boundary never dries out and that water is able to flow into the model. Approximately three cells were modified to smooth the inflow into the model.

There are 15 local inflow locations sourced from the Loders Creek hydrological model. Figure 4 depicts these locations.

Figure 4 Hydrograph Input Locations

These 15 inflows are added into the hydraulic model via the source and sinks option in the MIKE 21 setup. A set of 4 cells are used as a reference point to distribute the flow into the system.



3.9 Tailwater Conditions

For all design runs, a constant boundary condition of Mean High Water Springs (0.66mAHD) was set (refer Appendix B for tidal planes). A constant boundary was set to ensure that a high water level occurred simultaneously with the flood peak and produced a positively estimated flood surface.

In some instances, it was necessary to increase the boundary condition linearly to the MHWS mark. This was apparent when simulating future planning scenarios of 2050, 2070 and 2100. The progressively increasing boundary condition ensured model stability and removed the ambiguity of future initial water level conditions within the estuary. As such, the boundary file was changed as per Figure 5.

Figure 5 Boundary Conditions

For Historical Event simulations, the Loders Creek MIKE Flood model used tidal elevations recordings from the Gold Coast Seaway for the corresponding event.

For the Designated Flood level, two boundary conditions were set to create a flood surface envelope. The envelope was to contain two surfaces; a 1 in 100 Flood with a 1 in 20 year storm surge and a 1 in 20 year flood with a 1 in 100 year storm surge. The two surfaces produced by these scenarios were combined together in a GIS environment. Only the maximum value from each grid cell was obtained. The final values and grid surface comprised the Designated Flood Level.

3.10 Storm Surge Conditions

Storm surge conditions were received from an external consultant for three locations. The locations of storm surge conditions were at Logan, The Seaway and The Tweed.

The information specified in this report set precedence for all boundary conditions used in the model. This study specifies that the value of MHWS is to reach 1.46mAHD by 2100 (at the Seaway). See the GHD Storm Tidy Study Final Addendum Report, February 2013 for more information of tide values and climate conditions.



3.11 Digital Elevation Model

Bathymetric data obtained in 2013 was combined with LiDAR information to create the DEM for the Loders MIKE Flood model. The following data sources were used to produce the DEM:

Aerial Laser Survey 2009/2011/2012 (GCCC_2m_DTM_Dec_2014)

Bathymetric Data from 2013

2003 Cross-section Survey Data (Bridge Decks)

The following figure depicts the DEM that is used in the Loders MIKE Flood Model.

Figure 6 DEM Grid

There are limitations when using LiDAR for DEM modelling. See ‘limitations’ Department of Environment and Resource Management. LiDAR and Orthophoto Acquisition 2009 [10] for more details.



3.12 Bathymetric Surveys

Bathymetric data has been obtained over a number of years to represent the Gold Coast waterways. The figure below graphically depicts where and when this information is used within the hydraulic model of Loders Creek.

Figure 7 Terrain Sources



3.13 Model Parameters

3.13.1 Floodplain Roughness

The following roughness values were adopted for the Loders Creek Hydraulic study.

Table 1 Typical Manning’s ‘n’ roughness values

Description Manning’s ‘n’

Grassed Channels 0.03

Water body 0.015-0.025

Paved surface 0.016-0.02

General overbank area 0.06

General open space area 0.07

Low density residential area 0.08

Heavily vegetated area 0.10

Road Crossing Channels 0.075 – 0.12

The above values represent the floodplain roughness and are based on the recommended values from:

Chapter 7 of the ARR 1998 (Ref 5) Chapter 9 of the QUDM 2008 (Ref 6) Chapter 4 of Main Road’s Road Drainage Design Manual (Ref 7) Appendix C of BCC’s Natural Channel Design Guidelines (Ref 8)

A roughness map was developed from aerial photography and Council’s GIS layers.



The Roughness for Loders Creek varies considerably from the upper reaches to the coastal boundary. Due to the open-space living arrangements in the upper estuaries of Loders Creek, light resistance and easy passages of flow primarily dominate its roughness co-efficient. Whilst intertwining through suburbs of Southport, the roughness co-efficient increases. This is due to the denser living arrangements of the community. The following figure, diagrammatically, shows the specified roughness of particular areas, which influence the passage of floodwaters in Loders Creek during a rainfall event. To ensure consistency across all hydraulic modelling on the Gold Coast, all roughness values for specific categories were applied consistently across all regional hydraulic models for the Gold Coast.

Figure 8 Loders Creek Roughness Map

The above roughness map was produced by inspecting aerial photography of the catchment and assigning values correspondingly to their respective locations. The distribution of the Manning’s ‘n’ roughness coefficient is illustrated in Figure 8 and is depictive of the grid used in the MIKE Flood model to represent the variations of roughness throughout the catchment. A global value for roughness was used within MIKE 11 structures and this was set at a Manning’s coefficient value of 30. The areas of blue outside the model extent are not considered during simulation.



3.13.2 Eddy Viscosity

The eddy viscosity value was estimated by using the following equation: ∆x and ∆y are the grid spacing values. Loders is a 5 metre rigid grid model, therefore ∆x and ∆y equal 5. The time step (∆t) was set at 1.0 seconds.

t

yxe

02.0

0.1

5502.0

e

5.0e

For the Loders Creek catchment, an Eddy velocity based viscosity value was set at ‘0.5’. This value was applied uniformly across the catchment. For events that encountered instabilities, the time-step was modified. For these events, the eddy was adapted to suit the corresponding time step (∆t).

3.13.3 Flooding and Drying

To ensure an accurate mapping extent, taking into account floodplain shape and slope, the following drying and flooding values were adopted:

Drying = 0.02m

Flooding =0.05m

The drying depth is the minimum water depth allowed in a point before it is taken out of calculation. The flooding depth is the water depth at which the point will be re-entered into the calculation. These values will affect the extent of inundation on a floodplain, but not the maximum flood surface level.



3.14 Structures

Figure 9 depicts the structures modelled in the Loders Creek hydraulic model and the respective locations of these structures.

Figure 9 Structure Locations

3.14.1 Hydraulic Structures Not in Model

A number of hydraulic structures were excluded from the model. These structures were deemed as having very little impact in regards to regional flood mapping. Generally, pipes with diameters less than 900mm were not included in the modelling as it was assumed that they would have a relatively small impact on the flooding behaviour.



3.14.2 Culvert Data

The following table specifies known attributes of the culverts located within the Loders Creek Catchment:

Table 2 Structure Details

Branch Dimensions (WxH) or (Dia) ID Upstream

Invert Downstream

Invert Length Mannings N

No. of Culverts Shape

ChirnCrescent 3m x 1.8m CU17 ChirnCresentCulverts ‐0.3 ‐0.35 43.1 0.033 3 Rectangular

BarattaSt 2.7m x 1.2m CU12BarattaStWeir 0.95 0.83 20.8 0.04 2 Rectangular

KumbariAve 2.1m x 1.8m CU13WardooStCulverts3 1.774 1.75 43.1 0.033 2 Rectangular

EdmundRiceDr 1.8m CU14EdmundRiceDr 9 8.76 32.1 0.033 2 Circular

QueenSt 3m x 2.1m CU2 QueenStCulverts 1.89 1.885 25 0.033 7 Circular

BambarraSt 3.3m x 1.8m CU3 BambarraStCulverts 2.375 2.365 30 0.033 2 Rectangular

PrinceSt 3.2m x 1.8m PrinceStCulverts 3.25 3.19 50 0.033 2 Rectangular

WardSt 3.2m x 1.8m CU5 WardStCulverts 3.53 3.48 26 0.05 2 Rectangular

MinnieSt 3m x 2.1m CU7 MinnieStCulverts 4.72 4.68 25 0.033 2 Rectangular

MargaretSt 2.1m x 1.2m CU8

SouthportNerangRdCulverts 6.301 6.25 30 0.033 4 Rectangular

DandarDr 1.2m x 0.6m CU9 DandarStCulverts 8.8 8.5 29.1 0.033 2 Rectangular

SouthportNerangRd 2.1m x 1.8m CU17 SouthportNerangRd 10.1 10 32.5 0.05 6 Rectangular

WardooSt 1.05m CU10WardooStCulverts2 11 10.9 36.3 0.033 2 Circular

LodersDam 1.8m LodersDamCul. 5.22 2.32 57 0.033 1 Circular

SmithSt 3.5m x 2.4m SmithSt ‐0.45 ‐0.5 30 0.05 5 Rectangular

FalconerSt 6.5m x1.6m Falconer_AsCon 4.105 4.073 20 0.03 1 Rectangular



3.14.3 Bridge Data

All of bridges located within the Loders Creek catchment were modelled in MIKE 11 using the energy equation. The MIKE 11 Bridge functionality uses the Energy Equation to determine the discharge and the backwater profile through the bridge. It takes into account the friction loss and contraction/expansion losses and it requires four cross sections (see Figure 10). River cross sections one and four are defined in the cross-section editor. Bridge cross sections two and three are defined through the bridge geometry in the network editor. Ideally, the distance between the bridge and the up and downstream cross-sections should be of the order b, where b is the bridge opening width. The latter is to ensure that the streamlines are parallel at section one and section four.

Figure 10 Location of up- and downstream cross section.

1: Upstream river cross section - Defined in the cross section editor. 2: Upstream bridge cross section - Defined in the network editor, bridge geometry. 3: Downstream bridge cross section - Defined in the network editor, bridge geometry. 4: Downstream river cross section - Defined in the cross section editor.

Figure 11 Definition of the bridge cross section markers.



The bridge loss factors include Channel Resistance, Contraction and Expansion Losses. The value for resistance on the bridge structure was set between markers 1 and 4 and between 5 and 3. Between markers 4 and 5 the bed resistance given in the HD editor will be used.

Opening/Contraction ratio: Choose channel contraction ration or bridge opening ratio as parameter in the loss factor tables.

Table 3 Channel Transition Energy Loss Coefficient (Ref 7)

Transition Type Contraction Coefficient

Expansion Coefficient

Gradual Channel Transition 0.1 0.3

Straight Through Bridge Transition 0.3 0.5

Square Edged Abrupt Transition 0.6 0.8

The following losses were applied in M11 culverts:

Contraction Loss = 0.3

Expansion Loss = 0.5



3.14.4 Bridge Set up

The following figure depicts the general set up for MIKE 11 bridges used in the Loders Creek hydraulic study. Note: Submergence, Overflow and Piers Options are checked.

Figure 12 MIKE11 Bridge Setup

Each bridge modelled has contained a blockage factor of 10%. This is set to account for the impact of debris on the bridge columns.

Table 4 Bridge Structure Details

Name Bridge ID Type Submergence Overflow Bridge Level

(Bottom)

Bridge Level (Top)

Musgrave Ave Bridge

BR2 Musgrave Ave Bridge (BRID28)

Energy Equation

Energy Equation

Energy Equation

2.27 3.07

Johnson St BR3 Johnston St Energy Equation

Energy Equation

Energy Equation

2.91 3.41

Gold Coast Highway

BR5 Gold Coast Highway

Energy Equation

Energy Equation

Energy Equation

2.23 2.73

Southport Primary Bridge

BR4 Southport Primary

Energy Equation

Energy Equation

Energy Equation

3.5 4



4 Model Calibration and Verification

The Loders Creek hydraulic model simulated three historical rainfall events for calibration purposes. Described below are the characteristics of the two events:

The following section details the processes undertaken to calibrate the hydraulic model to tide and two historical flood events. The process occurred in that order with the model first being calibrated to tide then to a historical rainfall event.

4.1 ALERT Stations

The Bureau of Meteorology (BOM) operates a number of flood telemetry systems, known as ALERT stations, on the Gold Coast and Logan region for flood prediction and climate data collection. These ALERT stations record water level, discharge and other meteorological data. Other telemetry stations, known as TM stations, are operated by The Marine Safety Queensland (MSQ) and Department of Environment and Resource Management (DERM). These stations generally record stream flow, water quality and tide data. Around the Biggera catchment area, both ALERT and TM stations data are available for flood and tide calibration. They are:

Loder Dam AL (540359) – 5.27 m AHD (assumed gauge zero)

Loder Creek AL (540238) – 0.13 m AHD (assumed gauge zero)

Air Sea Rescue\Marine Operation Base AL (040881)

Gold Coast Seaway TM (540001)

4.2 Maximum Height Gauges and Historical Debris Mark

City of Gold Coast maintains a number of maximum height gauges (MHG) (Table 5 Summary of Maximum Height Gauge Location and Surveyed Details.Table 5) and a database of historical debris marks. Seven MHG’s are within the hydraulic model area and Council has surveyed debris marks for the June 2005 event.

Table 5 Summary of Maximum Height Gauge Location and Surveyed Details.

ID Easting Northing Top of Gauge (m AHD)

401 537843.8 6905218.97 13.8

402 538760.9 6906562.93 5.77

404 539719.3 6906687.33 3.71

405 539624.8 6907340.75 4.24

406 540167.3 6907627.26 3.24

407 539029 6905818.67 5.95

408 538861.9 6905053.41 11.94



Figure 13 - MHG, ALERT and Debris Locations



4.3 June 2005 Calibration

A major flood occurred in South East Queensland on the 30th June 2005, where heavy rainfall caused flooding in several areas of Gold Coast. This flood event provided good data at the ALERT stations, produced numerous debris marks and several flood heights were captured at MHG locations. As such, this event was used for calibration of the Loders Creek Hydraulic Model. Note: The BoM has prepared a report for this flood event. See Ref 9 for further details.

Figure 14 June 2005 Extent

Figure 14 demonstrates the estimate peak flood extent for Loders Creek during the June 2005 event.



This figure depicts model results (blue) for the June 2005 event compared to MHG recordings (yellow).

Figure 15 Water Level Results June 2005 Calibration



The following figures show the June 2005 water level calibration results at the ALERT stations:

Figure 16 Loders Creek ALERT Station Calibration 2005

Figure 17 Loders Dam ALERT Station Calibration 2005

The water levels here are replicative of the original hydrology and its associated rating curve. The routing of total hydrographs near the dam in the hydraulic model may have diminished the catchments ability of representing (to represent) upstream storages, significant groundwater losses or attenuations of runoff formed by natural detention basins. Therefore, calibration at the dam is overestimated due to the input.



4.4 January 2008 Calibration

This Gold Coast flood event occurred on the 4th of January 2008. Good water level data was recorded at both ALERT stations for this event. The figure below shows the comparison between modelled and recorded water levels at Loders Dam and Loders Creek ALERT stations.



Good calibration is achieved at both ALERT station locations for the January 2008 event.



4.5 January 2013 Calibration

On the 26th of January 2013, another notable Gold Coast flood event occurred. This was a small flood event with the dam experiencing good data recordings. Below shows the comparison between modelled and recorded water levels at Loders Dam and Loders Creek ALERT stations.





5 Calibration Summary

When the January 2008 event occurred, the rainfall fell over the catchment more predominately in the upper reaches where the retardation basin retained most of the runoff. Good calibration is seen at the Loders Dam ALERT because of this rainfall distribution yet water levels are slightly underestimated at Loders Creek ALERT station.

Good calibration against the June 2005 event was achieved due to excellent data availability and recorded debris marks. As seen in Figure 16 and Figure 17, the water level at both ALERT stations recorded during the historical event was closely replicated by the model. This model has overestimated the flood at Loders Dam due to the change in hydrology inflows. The hydrologic inputs produce sharper peaks than previous estimates due to a revision in hydrologic parameters.

Excellent calibration is achieved for the January 2013 event despite the event severity being quite small. Responses of small inflows are seen at both locations with many fluctuations being represented. At the dam, there is a slight overestimation of the final flood wave yet a good falling limb is achieved.

Overall, model performance is quite good for the Loders Creek MIKE Flood model as the model matches well with the two newest flood events. Model performance can be improved for the June 2005 event by adjusting hydrologic parameters to smooth inflows upstream of the dam.



6 Design Floods

6.1 Introduction

Design floods are hypothetical and statistically based floods used for flood planning or for the designing of structures. They are based on a probability of occurrence and are either known as, or referred to as the:

ARI – Average Recurrence Interval or AEP – Annual Exceedance Probability

For example, a 100 year ARI or 0.1 AEP flood has an average recurrence interval of 100 years, or, the flood has a 1% probability of being equalled or exceeded in any one year.

With ARI expressed in years, the relationship is:

The AEP to ARI conversions are seen in Table 6.

Table 6 ARI and AEP Design Floods

ARI (in Years) AEP (as

Percentage)

2 39.3%

5 18.1%

10 9.5%

20 4.9%

50 2.0%

100 1.0%

200 0.5%

500 0.2%

1000 0.1%

2000 0.05%

The calibrated Loders Creek MIKE Flood hydrodynamic model was used to simulate design flood events ranging from 2 year ARI to PMF. The design runs include storm durations of 0.5, 1.0, 1.5, 3.0, 4.5, 6.0, 9.0, 12.0, 18.0, 24.0, 36.0, 48.0, 72.0, 96 and 120 hours. The hydrology of this study for both calibration and design events are sourced from the Loders Creek Hydrological Study (Ref 17)

The tailwater boundary for all design events are based on the City of Gold Coast’s - Storm Tide Study May 2012, undertaken by GHD (Ref 18).



6.2 Initial Water Level

For the design events, the following initial water level was applied to all model setups:

Creeks and canal system = 0 m AHD

It is important to note that the initial water level in the floodplain is set at 0 m AHD to ensure the storage in the system is partly full. The dam may contribute additional flow, and therefore, on the onset of a design flood the followings dam water levels were devised (Ref 18)

Table 7 - Initial Water Levels Inside Loders Dam

ARI Water Level

2 5.67

5 6.26

10 6.71

20 7.16

50 7.75

100 8.19

200 8.64

500 9.23

1000 9.68

2000 10.12



6.3 Design Run Setup

To ensure consistency, all model setups had naming conventions applied. Each model was set up so that if adjustments were made to the model, these changes would be reflected in all design events and durations. Figure 22 demonstrates the layout of the Loders Creek MIKE FLOOD files.

Figure 22 Model Naming Convention and File setup

The design runs are based on the following

Hydrological Input from 2014 hydrological study (Ref 17)

Selected Tailwater conditions

Similarly, result files from model runs were named using the following convention:

“Scenario Year”_”ARI & Duration”_”Catchment”.dfs0

6.4 Probable Maximum Flood

The model is setup for Probable Maximum Flood for the 24, 36, 48, 72 hour durations. For each event-duration, the PMP rainfall is applied to the individual temporal patterns to estimate PMF.



7 Analysis of Design Events

For Loders Creek, the following design events were simulated; Q2, Q5, Q10, Q20, Q50, Q100, Q200, Q500, Q1000, Q2000 and PMPDF. This included all durations from 30 minutes through to 72 hours. Results were stored on an external hard-drive for later use or for the flood search database.

7.1 Critical Duration

Loders Creek has the critical durations of 1.5, 3 and 4.5 hours. These durations occur at 1.5 hours at the Dam, 3 hours at the Loders Creek ALERT and 4.5 hours at the tidal boundary.

7.2 Maximum Water Level

The Maximum Water Level surfaces were generally achieved using the 3-hour duration event. The figure below depicts the maximum water level surface from the Loders Creek Hydraulic Model for a 1 in 100-year event.

Figure 23 - 2010 Q100 Surface (MHWS tailwater)


8 Conclusion

Good calibration was achieved to the 2005, 2008 and 2013 events with both calibration points (Loders Dam ALERT and Loders Creek ALERT Station), demonstrating replicable curves to that of the real event.

The calibrated model has been setup and simulated for the 2, 5, 10, 20, 50, 100, 200, 500, 1000 and 2000 year ARI design flood events. The model has also been setup and simulated for PMP flood events. These results are stored on external hard drives within the Natural Hazards team area.

The City of Gold Coast’s Designated Flood Level for the City Plan 2015, for the Loders Creek catchment, has been determined using this model. The City Plan 2015 map is the coincidental flood event of the Q100 flood with Q20 storm surge enveloped with the Q20 flood with Q100 storm surge and combined with sea level rise.

This model is the result of years of development and information accrual. This hydraulic model is representative of the environment in which the information was gathered but will require constant review and updating to take into account for any changes in its floodplain in the future.


9 Recommendations

In the event that further information for calibration purpose becomes available, the model is to be recalibrated.

Simulation times are quite significant for this model. Should technology permit faster simulation times using alternative methods of modelling, then consideration should be made to change modelling platforms.

Significant changes are planned to be made through the catchment due to the development of the Commonwealth Games Village and surrounding infrastructure. This model is to be updated with the as constructed information to allow better representation of the catchment.


10 References

1. Gold Coast City Council. Corporate GIS Layers (Catchment, Pipe Culvert, Bridge). 2. Gold Coast City Council. Investigation of Flooding in Loders Creek. Preliminary Report.

March 1968. 3. Gold Coast City Council. Loders Creek Catchment Study. Hydraulic Report. FS692.

January 2004. TRACKS-#22012085-LODERS CREEK HYDRAULIC STUDY 4. GHD. Loders Creek Dam Maintenance Plan and Manual. December 2002. TRACKS-

#14138623-LODERS CREEK DAM MAINTENANCE PLAN AND MANUAL 5. The Institution of Engineers Australia. Australian Rainfall and Runoff – A Guide to Flood

Estimation. 1998. 6. Queensland Department of Natural Resource and Water. Queensland Urban Drainage

Manual. June 2008. 7. Queensland Department of Main Roads. Road Drainage Design Manual. June 2002. 8. Brisbane City Council. Natural Channel Design Guidelines. November 2003. 9. Field Survey on 5 January 2010. 10. Department of Environment and Resource Management. LiDAR and Orthophoto

Acquisition 2009 11. Bureau of Meteorology website. http://www.bom.gov.au/hydro/flood/qld/ 12. Marine Safety Queensland website. http://www.msq.qld.gov.au/Home/Tides/ 13. Department of Environment and Resource Management website.

http://www.derm.qld.gov.au/water/monitoring/current_data/index.php 14. DHI. MIKE 11 User Manual 2014. 15. Bureau of Meteorology, Heavy Rainfall Gold Coast. June 2005. 16. Bureau of Meteorology, South East Queensland Floods. January 2008 17. Gold Coast City Council Loders Creek Hydrological Study 2014 TRACKS-#22012079-

LODERS CREEK HYDROLOGICAL STUDY 18. GHD Storm Tidy Study Final Addendum Report, February 2013 #39733283 19. Don Carroll, Loders and Biggera Retention Basin Studies, June 2014 #43295870


Appendix A Semidiurnal Tidal Planes - 2014


Appendix B – Loders Creek Structures

Musgrave Avenue

Figure B-1 Musgrave Avenue Bridge (Source: Ref 1)

Table B-1 MIKE 11 Bridge Details

Description Remarks

MIKE 11 Branch Musgrave Ave Ch. # (539710.8, 6907524.5)

Length 28.0m Eng. Services (Ref. 1)

Width (Waterway Length) 12.2m Eng. Services (Ref. 1)

Road (Left Bank/Right Bank) 3.08m AHD Surveyed (Ref. 3)

Bridge Top Level 3.07m AHD Surveyed (Ref. 3)

Bridge Bottom Level 2.27m AHD Assumed Deck is 0.8 m Thick

Table B-2 MIKE 11 Bridge Geometry (Energy Equation)

X Z

6.93 2.85

6.86 2.52

9.29 1.68

10.44 0.03

12.47 -0.53

15.63 -0.83

18.23 -1.36

22.30 -1.53

25.81 -1.68

27.37 -1.01

29.57 -0.14

31.70 0.22

33.00 1.44

X..cont Z..cont

35.12 2.80

37.66 3.07

29.25 3.09

18.54 3.08

10.22 3.07

6.93 2.85


Smith Street Culverts

Figure B-2 Smith Street Culverts and Pedestrian Bridge (Source: Ref 3)

Table B-3 MIKE 11 Culverts Details

Description Remarks

MIKE 11 Branch Smith Street Ch. # (539810.3, 6906797.9)

Dimensions 3.6m x 2.8m (3 box culverts); 3.6m x 3m (Space)

Surveyed (Ref. 3)

Width (Waterway Length) 30.4m ArcMap (Pipe_Culvert)


Culvert Invert U/S -0.80m AHD Surveyed (Ref. 3)

Culvert Invert D/S -0.73m AHD Surveyed (Ref. 3)

Table B-4 MIKE 11 Weir Details

X Z

2.83 0.00

2.83 2.71

2.84 5.42

2.85 10.83

2.87 16.25

2.88 21.66

2.90 24.94

2.91 28.23

2.93 31.51

2.95 34.79

2.95 41.41

2.96 48.03

X Z

2.97 51.59

2.98 55.16

3.00 58.72

3.01 62.28


Johnston Street Bridge (BR3)

Figure B-3 Johnston Street Bridge and Cable (Source: Ref 3)


Description Remarks

MIKE 11 Branch # Ch. # (539680.8, 6906584.8)

Length 28.0m Assumed

Width (Waterway Length) 10m Assumed





X Z

16.02 3.42

16.02 1.49

19.28 -0.65

23.18 -0.83

27.75 -0.75

31.47 -0.97

33.36 -1.09

35.51 -0.32

37.33 0.04

40.36 2.26

40.36 3.40


Southport Primary School Pedestrian Bridge (BR4)

Figure B-4 Southport Primary School Pedestrian Bridge (Source: Ref 3)


Description Remarks

MIKE 11 Branch # Ch. # (539318.5, 6906300.9)

Length 26m ArcMap (Bridge)

Width (Waterway Length) 1.8m ArcMap (Bridge)





X Z

0.00 4.04

0.00 3.72

8.64 0.47

13.06 0.17

17.93 0.28

19.30 1.07

22.94 2.42

26.32 3.89

26.32 4.02


Baratta Street Weir (WE1)

Figure B-5 Baratta Street Weir (Source: Ref 9)

Not in Model

Jackman Street Weir (WE2)

Not in Model


Queen Street Culverts (CU2)

Figure B-6 Queen Street Culverts (Source: Ref 3)

Table B-9 MIKE 11 Culvert Details

Description Remarks

MIKE 11 Branch # Ch. # (538926.9, 6906011.6)

Dimensions 1.65m Dia (7 circular culverts)

Surveyed (Ref. 3)



Culvert Invert U/S 1.89m AHD Surveyed (Ref. 3)

Culvert Invert D/S 1.85m AHD Surveyed (Ref. 3)


X Z

2.83 0.00

2.83 2.71

2.84 5.42

2.85 10.83

2.87 16.25

2.88 21.66

2.90 24.94

2.91 28.23

2.93 31.51

2.95 34.79

2.95 41.41

2.96 48.03

2.97 51.59

2.98 55.16

X Z

3.00 58.72

3.01 62.28


Bambarra Street Culverts (CU3)

Figure B-7 Bambarra Street Culverts (Source: Ref 3)


Description Remarks

MIKE 11 Branch # Ch. # (538977.7,6905342.1)

Dimensions 3.2m x 1.8m ( 2 box culverts)

Surveyed (Ref. 3)






X Z

4.5887 0

4.60116 1.17304

4.6175 1.35932

4.62061 6.7887

4.62373 6.80469

4.62996 6.83667

4.6941 7.16605

4.70033 11.5861

4.70656 11.6238

4.7133 11.6646

4.71953 14.5212

4.72576 14.5421

4.7707 14.6934

X Z

4.77693 19.9046

4.78316 19.9604

4.7995 20.1067

4.8378 20.3645

4.84091 35.7778

4.84403 35.7778

4.85026 35.7778


Prince Street Culverts (CU4)

Figure B-8 Prince Street Culverts (Source: Ref 1)


Description Remarks

MIKE 11 Branch # Ch. # (539052.4, 6905754.4)


Surveyed (Ref. 3)

Width (Waterway Length) 51.1 m ArcMap (Pipe_Culvert)

Road (Left Bank/Right Bank) m AHD Surveyed (Ref. 3)




X Z

5.1252 0

5.13358 5.36882

5.14196 5.44043

5.15873 5.58367

5.1635 5.62447

5.19703 7.15846

5.2593 7.41851

5.26349 16.9107

5.26768 16.9237

5.27606 16.9495

5.29283 17.0012

5.3455 17.1637

X Z

5.3455 17.1637

5.37903 18.6186

5.4126 18.6797

5.4221 18.9585

5.43048 23.9833

5.43886 23.9895

5.45563 24.002

5.7957 24.2558

5.82923 27.8802


Ward Street Culverts (CU5)

Figure B-9 Ward Street Culverts (Source: Ref 3)


Description Remarks

MIKE 11 Branch # Ch. # (539109.1, 6905710.1)


Surveyed (Ref. 3)






X Z

5.13 0

5.13 5.37

5.14 5.44

5.16 5.58

5.16 5.62

5.2 7.16

5.26 7.42

5.26 16.91

5.27 16.92

5.28 16.95

5.29 17

5.35 17.16

5.38 18.62

X Z

5.38 18.62

5.41 18.68

5.42 18.96

5.43 23.98

5.44 23.99

5.46 24

5.8 24.26

5.83 27.88


Falconer Street Culvert (CU6)

Figure B-10 Falconer Street Culvert (Source: Ref 3)


Description Remarks

MIKE 11 Branch # Ch. # (539144.9, 6905647.8)

Dimensions 2.05m x 7.5m (Opening) Surveyed (Ref. 3)






X Z

5.76 0

5.77 4.67

5.79 4.71

5.94 5.14

5.95 9.9

5.97 10.04

5.97 10.88

6.02 11.58

6.05 15.14

6.1 15.29

6.12 20.13

6.14 20.34

6.14 20.41

6.15 29.67

6.16 29.68

6.17 29.7

X Z

6.39 30.04

6.42 35.05

6.42 38.51

6.45 38.51


Minnie Street Culverts (CU7)

Figure B-11 Minnie Street Culverts (Source: Ref 3)


Description Remarks

MIKE 11 Branch # Ch. # (539157.2, 6905555.0)

Dimensions 3.3m x 1.7m (2 box culverts)

Surveyed (Ref. 3)






X Z

6.34 0

6.35 4.77

6.36 4.79

6.43 4.97

6.5 5.15

6.52 5.59

6.55 5.79

6.56 10.63

6.57 10.72

6.61 11.15

6.62 15.97

6.63 16.05

6.65 16.23

X Z

6.66 18.82

6.67 22.35

6.67 22.36

6.68 26.59

6.7 26.89

6.71 31.64

6.71 31.64


Southport Nerang Road Culverts 1 (CU8)

Figure B-12 Southport Nerang Road Culverts (Source: Ref 3)


Description Remarks

MIKE 11 Branch SouthportNerangRd Ch. # (539195.6, 6905409.7)

Dimensions 2.1m x 1.2m (2 box culverts), 2.5m x 2.3m (2 box culverts)

Surveyed (Ref. 3)

Width (Waterway Length) 30m and 31m ArcMap (Pipe_Culvert)





X Z

8.55 0

8.58 4.92

8.59 10.06

8.6 15.05

8.61 15.2

8.62 17.55

8.63 22

8.67 23.18

8.67 27.3

8.68 27.41

8.72 31.99

8.74 32.2

8.78 37.69

X Z

8.79 41.81

8.84 42.48

8.89 46.91

8.95 47.28

9 51.78

9.03 52.07

9.58 68.52


Nyora Street Pedestrian Bridge (BR5)

Figure B-13 Nyora Street Pedestrian Bridge (Source: Ref 1)

Not in model


Dandar Street Culverts (CU9)

Figure B-14 Dandar Street Culverts (Source: Ref 3)


Description Remarks

MIKE 11 Branch DandarSt Ch. # (538917.2, 6905047.6)

Dimensions 1.2m x 0.6m (2 box culverts)

Surveyed (Ref. 3)






X Z

9.53 0

9.54 4.97

9.54 5.19

9.54 9.57

9.58 10.14

9.59 14.94

9.59 15

9.61 15.2

9.62 18.26

9.63 18.48

9.64 20.2

9.65 20.31

9.66 23.55

9.68 23.67

9.69 28.93

X Z

9.69 33.28

9.72 33.47

9.73 34.47

9.75 34.81

9.76 39.56


Kindra Street Stilling Basin (ST1)

Figure B-15 Kindra Street Stilling Basin (Source: Ref 1)

Not in Model

Middleton Street Detention Basin (BA2)

Figure B-16 Middle Street Detention Basin (Source: Ref 9)

Not in Model


Wardoo Street Culverts 1 (CU10)

Figure B-17 Wardoo Street Culverts 1 (Source: Ref 3)


Description Remarks

MIKE 11 Branch # Ch. # (538546.0, 6904838.5)

Dimensions 1.05m Dia (2 Circular culverts)

ArcMap (Ref. 1)






X Z

12.3 0

12.32 2.36

12.38 3.76

12.39 5.15

12.39 10.45

12.4 10.7

12.4 25

12.41 25.14

12.41 30.65

12.43 31.87

12.45 35.28

12.46 36.1

12.48 48.87

12.53 53.5

X Z

12.53 53.5

12.55 56.65

12.55 56.77

12.57 67.09

12.62 67.7

12.63 71.16

12.66 72.25





Description Remarks

MIKE 11 Branch Inflow Point Ch. # (538448.6, 6905120.5)

Dimensions 1.5m Dia (2 circular culverts), 1.35m Dia (1 circular culverts

ArcMap (Ref. 1)






X Z

12.46 0

12.47 4.9

12.48 5.14

12.51 5.74

12.52 10.56

12.53 14.17

12.6 14.82

12.61 25

12.62 25.27

12.62 29.42

12.65 30.59

12.66 32.02

12.67 37.53

12.68 46.31

12.73 47.09

X Z

12.73 47.09

12.78 47.86

12.79 54.92

12.8 54.98

12.88 55.45

12.91 58.36


Baratta Street Culverts (CU12)

Figure B-19 Baratta Street Culverts (Source: Ref 3)


Description Remarks

MIKE 11 Branch BarrataSt Ch. # (538971.0, 6906297.9)

Dimensions 2.7 m x 1.2 m (2 box culverts)

ArcMap (Ref. 1)






X Z

3.1 0

3.11 3.53

3.11 7.07

3.11 14.13

3.11 19.05

3.12 23.97

3.12 27.79

3.13 28.55

3.14 29.31

3.16 30.08

3.17 30.84

3.18 31.6

3.19 32.36

3.21 33.12

3.22 33.88

X Z

3.23 34.64

3.24 35.4

3.27 36.92

3.29 38.44

3.32 39.96





Description Remarks

MIKE 11 Branch Wardoo St Ch. # (538816.0, 6906536.0)

Dimensions 2.1m x 1.8m (2 box culverts ArcMap (Ref. 1)






X Z

6.25 0

6.25 2.3

6.25 4.6

6.26 6.91

6.26 9.21

6.27 11.51

6.27 13.81

6.27 16.11

6.28 18.42

6.28 19.81

6.28 23

6.28 26.18

6.29 29.36

6.29 32.54

6.29 34.53

6.29 36.52

X Z

6.29 38.51

6.3 40.5

6.3 44.47

6.31 48.45


Edmund Rice Drive Culverts (CU14)

Figure B-21 Edmund Rice Drive Culverts (Source: Ref 3)


Description Remarks

MIKE 11 Branch EdmundRiceDr Ch. # (537784.9, 6906010.0)

Dimensions 1.8m Dia (2 circular culverts

ArcMap (Ref. 1)


Road (Left Bank/Right Bank) 12.25m AHD

Culvert Invert U/S 8.96m AHD

Culvert Invert D/S 8.76m AHD

Southport Nerang Road Culverts 2 (CU15)

Figure B-22 Southport Nerang Road Culverts 2 (Source: Ref 3)


Description Remarks

MIKE 11 Branch # Ch. # (537784.9, 6906010.0)

Dimensions 1.8m Dia (2 circular culverts

ArcMap (Ref. 1)


Road (Left Bank/Right Bank) 12m AHD

Culvert Invert U/S 10.25m AHD

Culvert Invert D/S 10.03m AHD


Southport Nerang Road Pedestrian Bridge (BR6)

Figure B-22 Southport Nerang Road Pedestrian Bridge (Source: Ref 1)

Not in model

Dominions Road Pedestrian Bridge (BR6)

Figure B-22 Dominions Road Pedestrian Bridge (Source: Ref 1)

Not in model


Turpin Road Culverts (CU16)

Figure B-23 Turpin Road Culverts (Source: Ref 1)


Description Remarks

MIKE 11 Branch ChirnParkCarPark Ch. # (539521.0, 6907620.8)

Dimensions 3.0 m x 1.8 m (3 box culverts

ArcMap (Ref. 1)

Width (Waterway Length) 169m ArcMap (Pipe_Culvert) – Approx.

Road (Left Bank/Right Bank) 2.1m AHD ALS

Culvert Invert U/S -0.51m AHD ALS - Approx

Culvert Invert D/S -0.52m AHD ALS - Approx


Musgrave Avenue Culverts (CU17)

Figure B-24 Musgrave Avenue Culverts (Source: Ref 1)


Description Remarks

MIKE 11 Branch Chirn Crescent Ch. # (539332.4, 6907589.2)

Dimensions 3m x 1.8m Box Culvert

ArcMap (Ref. 1)

Width (Waterway Length) 9m ArcMap (Pipe_Culvert)

Road (Left Bank/Right Bank) m AHD Modelled by Roughness

Culvert Invert U/S m AHD Modelled by Roughness

Culvert Invert D/S m AHD Modelled by Roughness


Barrett Avenue Culverts (CU18)

Figure B-25 Barrett Avenue Culverts (Source: Ref 1)

Time B-37 MIKE 11 Culvert Details

Description Remarks

MIKE 11 Branch ChuterAve Ch. # (539240.3, 6907528.6)

Dimensions 4.8 m x 2.1 m (3 box culverts)

ArcMap (Ref. 1)

Width (Waterway Length) 145m ArcMap (Pipe_Culvert) – Approx.

Road (Left Bank/Right Bank) 2m AHD

Culvert Invert U/S -0.3 m AHD

Culvert Invert D/S -0.35 m AHD


Neville Avenue Pedestrian Bridge (BR7)

Photo 1 Neville Avenue Pedestrian Bridge (Source: Ref 1)

Not in model


Gold Coast Highway Bridge Northbound (BR5)

Photo 2 Gold Coast Highway Bridge Northbound (Source: Ref 1)


Description Remarks

MIKE 11 Branch GoldCoastHwy Ch. # ( , )

Dimensions 12.47 x 47.65m As Constructed Drawings

Width (Waterway Length) 12.47m As Constructed Drawings

Road (Deck) 3.37m AHD As Constructed Drawings

Culvert Invert U/S N/A

Culvert Invert D/S N/A


Gold Coast Highway Southbound (BR6)


Description Remarks

MIKE 11 Branch GoldCoastHwy Ch. # (,)

Dimensions 12.47 x 47.65m As Constructed Drawings

Width (Waterway Length) 12.47m As Constructed Drawings

Road (Left Bank/Right Bank) 2.058/1.60m AHD As Constructed Drawings

Culvert Invert U/S N/A Surveyed (Ref. 3)

Culvert Invert D/S N/A Surveyed (Ref. 3)


Council of the City of Gold Coast PO Box 5042 GCMC Qld 9729 P 1300 GOLDCOAST E [email protected] W cityofgoldcoast.com.au

Documents

Loders Creek Catchment Hydraulic Study · Version 4 – August 18 TRACKS-#45330050-v4-LODERS_CREEK_HYDRAULIC_STUDY_2015 Page 3 of 72 Executive Summary The Loders Creek catchment is