Council archive · source document
Final Engineering services report _62 Lake Macdonald Drive · OPW25/0057
Very large file (27.0 MB): the whole original can take several minutes to open, especially on a phone. Text is quick to read.
Original PDF page 1, section 1. The text section number identifies this passage in the reader.
Report
Client: Noosa Shire Council
Project: Engineering Services Report
Location: 62 Lake Macdonald Drive, Cooroy
covey.com.au
233467 | M25-1037Rpt – April 2025
62 Lake Macdonald Drive, Cooroy – Engineering Services Report
See the original
The page text is free to read. Viewing or downloading an original file needs an account.
Log in to see the originalFull text of sections 2 to 48 (of 57)
Section 2
Report Review
Document No. Revision Prepared By Reviewed By Date Issued
M25-1037Rpt A S.Kohn | C.Temmerman P.Gintrac April 2025
Report Distribution
Document Revision Method of Delivery Issued To
Noosa Shire Council
M25-1037Rpt A Electronic
([email protected])
© Copyright Covey Associates Pty Ltd (2025).
This document is the property of Covey Associates Pty Ltd. This document and the information contained in it are solely for the
use of the authorised recipient and this document may not be used, copies of reproduced in whole or part for any purpose other
than that for which it was supplied by Covey Associates Pty Ltd. Covey Associates Pty Ltd makes no representation, undertakes
no duty and accepts no responsibility to any third party who may use or rely upon this document or the information contained in
it.
COPYRIGHT NOTICE: Parts of this document contain material originally prepared by:
This material is the intellectual property and copyright of Covey Associates Pty Ltd.
Samuel Kohn Christopher Temmerman Peter Gintrac
Author: Samuel Kohn Author: Christopher Temmerman Review: Peter Gintrac
Civil Designer Senior Civil Designer Senior Civil Engineer
ADEng DipEngSpatSci BEng(Civil)
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page i
233467 | M25-1037Rpt – Issue A – April 2025
Section 3
TABLE OF CONTENTS
1.0 INTRODUCTION 1
2.0 PROJECT INFORMATION 1
2.1 SITE LOCATION 1
2.2 TOPOGRAPHY AND DRAINAGE 1
2.3 POTENTIAL LAND-USE / DEVLOPMENT POTENTIAL 1
3.0 CIVIL ENGINEERING ASSESSMENT 2
3.1 BULK EARTHWORKS 2
3.2 EROSION AND SEDIMENT CONTROL (ESC) AND ENVIRONMENTAL MANAGEMENT 3
3.3 ROAD HIERARCHY AND PATHWAYS 4
3.4 EXTERNAL ACCESS AND AGRESS POINTS 4
3.5 INTERNAL STREETS 6
3.6 STREET LIGHTING, ELECTRICAL AND TELECOMMUNICATIONS 6
3.7 PATHWAYS AND CYCLEWAYS 6
3.8 FLOODING AND STORMWATER 6
3.8.1 Flood Hazard Assessment 6
3.8.2 Localised Flooding 6
3.8.3 Stormwater Network Design 7
3.8.4 Stormwater Detention Modelling 7
3.9 STORMWATER QUALITY 7
3.9.1 Water Quality and Treatment Objectives 8
3.9.2 Catchment Description 8
3.9.3 Scenario Method 9
3.9.4 Music Modelling 10
3.10 Water and Sewerage 10
4.0 CONCLUSION 10
LIST OF FIGURES
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page ii
233467 | M25-1037Rpt – Issue A – April 2025
Section 4
LIST OF FIGURES
Figure 1: Site Locality Plan ................................................................................................................................................ 2
Figure 2: Lake Macdonald Drive / Dianella Court Intersection ......................................................................................... 4
Figure 3: Channelised right-turn treatment with a short turn slot [CHR(S)] .................................................................... 5
Figure 4: Lake Macdonald Drive / Dianella Court Intersection Sight Distances ............................................................... 5
Figure 5: Flood Hazard / Defined Flood Event .................................................................................................................. 7
Figure 6: Stormwater Drainage Catchments..................................................................................................................... 9
L
LIST OF TABLES
Table 1: SISD Analysis........................................................................................................................................................ 5
Table 2: Pollutant Reduction Targets for South East Queensland .................................................................................... 8
Table 3: MUSIC Source Node Characteristic ..................................................................................................................... 9
Table 4: Proposed Bioretention Basin Design for Development Sub-Catchments ......................................................... 10
Table 5: Catchment A MUSIC Model Results .................................................................................................................. 10
LIST OF APPENDICES
APPENDIX A Flood Hazard Assessment – HydraLogic dates 4 September 2024
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page iii
233467 | M25-1037Rpt – Issue A – April 2025
Section 5
1.0 INTRODUCTION This Engineering Services Report (ESR) is to provide information as to the development potential and servicing of the defined property (62 Lake Macdonald Drive, Cooroy) on behalf of Noosa Shire Council. This report identifies engineering aspects associated with a proposed development and may form the basis of future works and supporting documentation for the commencement of a development application with Noosa Shire Council. 2.0 PROJECT INFORMATION 2.1 SITE LOCATION The site is located on the corner of Lake Macdonald Drive and Dianella Court, at Cooroy with an overall site area of approximately 3.54 ha. The real property description is Lot 105 on SP118458. The total site currently consists of a storage shed, vegetation and open space. The proposed development application is for lot reconfiguration for residential purposes. Adjoining land used to the site include: • South Undeveloped vegetated, low-density allotments and road reserve • East Low-density residential • West Cooroy Cemetery Refer to Figure 1 – Site Locality Plan. 2.2 TOPOGRAPHY AND DRAINAGE The site is approximately 3.54 ha in size and approximately half of the site on the northern side has been cleared with remnant pine plantation covering most of the southern half of the site. This is not protected vegetation and is to be cleared as part of the site contaminated land remediation works. The site generally grades north, east and south from a high point of approximately RL 128 on the western boundary down to approximately RL 103 at the north-east corner of the site. There is a small external catchment (1/SP118458) of approximately 0.35 ha. Roughly half of this catchment will be cut- off by the proposed swale drain on the eastern boundary of the proposed balance lot. The other half will flow through proposed lot 3, matching what occurs in the existing case scenario until lot 3 is developed. It is expected that this flow will then be cut-off and piped within lot 3, to its nominated point of discharge. 2.3 POTENTIAL LAND-USE / DEVLOPMENT POTENTIAL The land parcel will be divided into three (3) community use lots and one (1) balance lot, including associated road and drainage reserve. The balance lot will be provided as a provision for the future expansion of the Cooroy Cemetery that currently operates on the adjacent land. The ultimate case for the development utilised for engineering design is a maximum expected yield of 130 units with a mix of one-, two- and three-bedroom units spread across the three community use lots. It is assumed that these units and/or buildings will have a maximum of three stories. For further details, refer to the Operational Works Plans. 62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 1 233467 | M24-1037Rpt – Issue A – April 2025
Section 6
Figure 1: Site Locality Plan
(Image courtesy of Nearmap.com)
3.0 CIVIL ENGINEERING ASSESSMENT
This Section provides preliminary details on the civil infrastructure required to complete the development.
3.1 BULK EARTHWORKS
The bulk earthworks for the development are expected to comprise of two phases.
Phase 1 will consist of:
• Excavation and export off site of contaminated soil in the northern section of the site. If economical, screening of
the contaminated soil may occur on site to minimise the volume of soil required to be exported. Any clean material
resulting from the screening will be reused and spread on site.
• Clearing and grubbing of the existing vegetation in the southern section of the site. Extent of vegetation to be
mulched and re-used or exported is to be determined on site during construction.
• Topsoil for the balance of the site to be stripped and stockpiled for reuse and site stabilization activities.
Phase 2 will consist of cut to fill of residual soil to meet the proposed design levels and layout. Any excess cut may be
respread over the allotments, and topsoil respread upon completion. It is not expected that any imported fill will be
required to meet the desired ground levels.
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 2
233467 | M24-1037Rpt – Issue A – April 2025
Section 7
The site: • Does not contain Acid Sulfate Soil overlays. • Does contain Landslide Hazard, moderate to high overlays. Geotechnical testing has been undertaken on the site and a Geotechnical Investigation Report has been prepared by Core Consultants. The residual soil consists mostly of sandy-clay (eastern side) and silty-clay (central and western areas). Both the silty and sandy clay soil samples tested are non-dispersive. The report recommends temporary batter slopes up to 3.0 m vertical height could be battered at 1V:2H in the firm residual clay soils, and 1V:1H in the stiff (or stiffer) residual clay soils and weathered rock. For permanent fill batters: • 1V:3H in the firm residual soils. • 1V:2H in the future controlled fill and stiff (or stronger) residual soils and extremely weathered materials. • 1V:1H in the highly weathered, very low strength sandstone. The depth of topsoil and contaminated material across the site has been interpolated from the test pit data provided in the Geotechnical and Contaminated Land Remediation reports. This data has been used to model the surface used to approximate the required stripping and excavation volumes that are shown on the design plans. 3.2 EROSION AND SEDIMENT CONTROL (ESC) AND ENVIRONMENTAL MANAGEMENT In accordance with the contractual obligations and Environmental Legislation requirements, the Civil Contractor performing the site remediation and civil earthworks are responsible for the management of site runoff. The contractor is to ensure the capture and treatment of stormwater flows during construction activities and up to the time the site is suitably stabilised in accordance with legislative requirements. The contractor is to engage a Registered Professional Engineer Queensland (RPEQ) with suitable Erosion and Sediment Control experience or Certified Professional in Erosion and Sediment Control (CPESC) to provide site ESC plans for submission with the Construction Management Plan to Council. Throughout construction activities, the contractor is to engage regular (to be determined by Council) CPESC inspections and reporting. Construction stormwater runoff is to be captured and directed to High Efficiency Sediment (HES) basins for treatment prior to leaving the site. Lots 1, 2 and 3 and any disturbed areas of balance Lot 100 are to be stabilized through the application of topsoil and seeding with ongoing maintenance suitable to ensure adequate grass coverage of the site. Further earthworks activities and ESC requirements associated with the future built form of each lot is to be documented and approved through future Operational Works applications. 62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 3 233467 | M24-1037Rpt – Issue A – April 2025
Section 8
3.3 ROAD HIERARCHY AND PATHWAYS All roads, pathways and frontage work within the subject site are to be designed and constructed in accordance with the relevant provisions of Noosa Council Planning Scheme Policy SC6.7 - Engineering Design Standards, and in accordance with any specific requirements through an application process. There has been no Traffic Impact Assessment completed to date - road hierarchy and potential requirements have been determined based on the Noosa Planning Scheme requirements and intersection form provided by Noosa Council. 3.4 EXTERNAL ACCESS AND AGRESS POINTS The proposed development is accessed via a new road connection from Dianella Court. To service the development, an upgrade to the intersection of Dianella Court and Lake Macdonald Drive would be required. The proposed and existing roads are classified as follows in the Noosa Plan: • Lake Macdonald Drive Urban Residential Collector (current) • New Internal Road (Road 1) Local “Lane” Lake Macdonald Drive at the Dianella Court intersection is currently a two-lane road with approximately 3.0 m wide through lanes. The shoulder width at the intersection is approximately 2.0 m wide and tapers to back to zero width. There is no right turning lane provision for Dianella Court or the opposing Wilgee Court. Refer to Figure 2 for the existing intersection arrangement. Figure 2: Lake Macdonald Drive / Dianella Court Intersection (Image courtesy of Nearmap.com) The proposed upgraded intersection will include a right turn lane on Lake Macdonald Drive into Dianella Court and form an Urban CHR(S) intersection in accordance with Austroads Guide to Road Design Part 4A, refer to Figure 3. The proposed intersection will require widening on the development side of Lake Macdonald Drive to accommodate the added right turn lane and extension of the 2.0 m wide shoulder. The proposed design includes a raised planted 62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 4 233467 | M24-1037Rpt – Issue A – April 2025
Section 9
traffic island with a cut-through pedestrian crossing on the western leg and a painted chevron median to the eastern
leg in accordance with Noosa Shire Council specifications and standard drawings.
Figure 3: Channelised right-turn treatment with a short turn slot [CHR(S)]
(Image courtesy of Guide to Road Design Part 4A)
A sight distance analysis has been prepared, based on the proposed geometry of the upgraded intersection. The
following parameters have been used to determine the minimum Safe Intersection Sight Distance (SISD) in accordance
with Austroads Part 4A (Normal Design Domain):
• Lake Macdonald Drive (LMD) design speed of 70 km/h
• General minimum reaction time (Rt) of 2 seconds
• LMD Eastbound downgrade correction of + 7 m
• LMD Westbound downgrade correction of + 11 m
Table 1 and Figure 4 provides results of the sight distance analysis which indicates that compliance has been met or
exceeded.
Table 1: SISD Analysis
Direction SISD Grade Correction SISD Corrected SISD Achieved Compliance
LMD Eastbound 151 m +7m 158 m 212 m Y
LMD Westbound 151 m + 11 m 162 m 375 m Y
Figure 4: Lake Macdonald Drive / Dianella Court Intersection Sight Distances
(Image courtesy of Nearmap.com)
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 5
233467 | M24-1037Rpt – Issue A – April 2025
Section 10
3.5 INTERNAL STREETS The road reserve width of the proposed internal roadway is 23.0 m wide, which includes a 10.0 m vegetated buffer on the eastern side and a 6.775 m verge on the western side (new lot frontage side). The geometric design of the internal development roads is to be nominal 6.0 m wide with a 1.0 m widening applied to the inside curve of the initial bend, and 0.5 m widening to the inside curves of the ‘S’ bend. The road is generally in accordance with the Noosa Plan Engineering Design Standards policy and Austroads Guide to Road Design. 3.6 STREET LIGHTING, ELECTRICAL AND TELECOMMUNICATIONS Street lighting installations on roads, within the development and where proposed along external road frontages of the development, will be designed and erected in accordance with the Council’s Planning Scheme Policy SC6.7 and Australian Standards AS1158. Underground electrical and telecommunications connections will need to be provided to each proposed allotment. A review of the existing electricity and comms is outside the scope of this report. Street lighting, electrical and telecommunications are to be designed and assessed through an individual Operation Works application. 3.7 PATHWAYS AND CYCLEWAYS A 2.0 m wide shared pathway is proposed for the length of the new internal road, with connectivity to the existing path network along Lake Macdonald Drive. The proposed widening of Lake Macdonald Dr will include the re-alignment of the existing path and cut-through pedestrian crossing at the proposed traffic island. This ensures existing path connectivity is maintained. 3.8 FLOODING AND STORMWATER There has been no Flood Impact Assessment completed within the scope of this report. Council has provided a Flood Hazard Assessment completed by HydraLogic dated 4 September 2024 in support of the development, for further information refer to Appendix A. 3.8.1 Flood Hazard Assessment The Flood Hazard Assessment identifies the intersection has a 10 % AEP flood immunity, while less frequent events overtop the roadway with varying levels of flood hazard classification and lengths of inundation. A sensitivity analysis of the culverts under Lake Macdonald Drive demonstrated that should a significant blockage of the culverts occur during a major rainfall event, the depths of inundation across the culvert would not be expected to significantly change. 3.8.2 Localised Flooding Except for a localised area on the north-eastern corner of the site (within the proposed drainage reserve), all levels are above the Council flood inundation mapping. Refer to Figure 5 for further details. Minimum lot levels will be based on the latest Council flood mapping. 62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 6 233467 | M24-1037Rpt – Issue A – April 2025
Section 11
Stormwater flows generally flow to the intersection of Lake Macdonald Drive through a pipe network and overland flow, the developed case redirects flows via the proposed road corridor with suitable contained road flow capacity up to and including the 1 % AEP as a minimum. Figure 5: Flood Hazard / Defined Flood Event (Image courtesy of Noosa Council Mapping) 3.8.3 Stormwater Network Design Stormwater design has been undertaken in accordance with the Noosa Plan Engineering Design Standards (2020) and Queensland Urban Drainage Manual 2017 (QUDM). The design was undertaken utilising 12D design software package and the rational method to meet the requirements for a minor and major storm event. Refer to Appendix A for the Operational Works Plans for the proposed stormwater design. Lots 1 & 2 (Catchment A) will discharge to the existing stormwater network via the proposed bioretention basin. Lot 3 (Catchment B) will discharge to the currently undeveloped Pear Tree Lane reserve and subsequently sheet flow to an existing drainage reserve (900 SP176968). Refer to Figure 6 for details. 3.8.4 Stormwater Detention Modelling No hydrologic modelling was undertaken to determine the detention requirements for each residential lot (if any). The developer(s) of the individual lots must seek approval from Noosa Shire Council for any stormwater detention infrastructure that may be required to facilitate the development of each lot. Stormwater detention infrastructure must be contained within the lot that it serves. 3.9 STORMWATER QUALITY Stormwater quality is to be controlled through the construction of a bioretention basin located on proposed Lot 900. The bioretention basin will have all piped stormwater flows directed to the basin, discharging to a sediment forebay. 62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 7 233467 | M24-1037Rpt – Issue A – April 2025
Section 12
The basin is sized suitably to meet the water quality requirements identified in the following sections. The bioretention
basin is not designed as a water quantity (detention) device, detention requirement is to be determined and provided
on a lot-by-lot basis to suit the proposed future built forms.
The bioretention basin outlet pipe system is sized to direct flow from the 10 % AEP event into the existing Council
piped network. The existing Council network in turn, caters for the 10 % AEP flows.
For less frequent rainfall events, flows above the 10 % AEP will outlet the bioretention basin through the overflow
weir.
3.9.1 Water Quality and Treatment Objectives
This section will demonstrate how the proposed stormwater quality management strategy complies with the
requirements of the Noosa Plan (2020) and the SPP (2017) in terms of demonstrating how the relevant stormwater
pollutant reduction objectives will be met.
Stormwater runoff generated from the site must achieve the required pollutant reduction targets and be
demonstrated in MUSIC. Table 2: Pollutant Reduction Targets for South East Queensland quantifies the reduction
objectives required under the NSC Water Quality and Drainage Code (NSC, 2020) and the Queensland State Planning
Policy (SPP, 2017).
Table 2: Pollutant Reduction Targets for South East Queensland
Pollutant Type Reduction Objective
Total Suspended Solids (TSS) 80% reduction in average annual load of pollutants
Total Phosphorus (TP) 60% reduction in average annual load of pollutants
Total Nitrogen (TN) 45% reduction in average annual load of pollutants
Gross Pollutants (GP) 90% reduction in average annual load of pollutants
3.9.2 Catchment Description
The development site will be divided into three (3) lots and one (1) balance lot, including road reserve and drainage
reserve. The proposed drainage reserve will contain a bioretention basin which will exclusively treat Catchment A as
shown in Figure 6.
Catchment A:
The proposed treated Catchment A includes Lots 1 and 2, the proposed road reserve areas which drain to the
bioretention basin in lot 900. Ultimately, this yields the total treatable area of 1.66 ha in the associated MUSIC model.
Catchment B:
The developer of Lot 3 is to ensure its stormwater treatment independently complies with the relevant stormwater
quality guidelines. Any future stormwater treatment infrastructure proposed for Lot 3 is to be contained within the
allotment. It is assumed that a stormwater treatment area will be provided in the lower (southern) corner of the site.
An outlet pipe will be provided as a point of discharge.
Catchment C:
This catchment encompasses the balance lot which is to remain unchanged with no stormwater treatment proposed.
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 8
233467 | M24-1037Rpt – Issue A – April 2025
Section 13
Figure 6: Stormwater Drainage Catchments
3.9.3 Scenario Method
The proposed development was modelled using split catchment source nodes. Three (3) urban residential source
nodes were identified, comprising of road, ground cover and roof nodes. Sub-catchments were derived from the
proposed stormwater drainage plans.
Although the exact quantity of dwellings cannot be confirmed, it is expected that the average density of dwellings/ha
within Lots 1 and 2 will be approximately 65 dwellings/ha and should be roughly between the 40 dwellings/ha and 80
+ dwellings/ha impervious fraction recommendations in Table 3.5 of the MUSIC Modelling Guidelines – South East
Queensland Version 1.0 (WBD, 2010). The nominated fraction impervious for each source node modelled in MUSIC
was therefore:
• Road source node: 40% impervious
• Ground cover source node: 70% impervious
• Roof source node: 100% impervious
The roof area has conservatively been estimated to be approximately 90% of the lot area, with the remaining 10%
categorised as ground cover.
The ~20m wide access reserves that extend from Road 1 to the balance lot 100 have been included in the Road node.
40% fraction impervious has been adopted within the access reserves to allow for future driveway and path accesses.
This matches the impervious percentage within the Road 1 reserve.
Table 3: MUSIC Source Node Characteristic
Source Node Road Ground Cover Roof Total
Catchment Sub-Catchment Area (ha) Area (ha) Area (ha) Area (ha)
A N/A 0.73 0.09 0.85 1.67
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 9
233467 | M24-1037Rpt – Issue A – April 2025
Section 14
The stormwater runoff from the proposed stormwater treatment catchments will be treated by one (1) bioretention
basin prior to discharge into the existing stormwater drainage network. Table 4 outlines bioretention basin details for
the proposed stormwater treatment train for the Catchment ‘A’.
Table 4: Proposed Bioretention Basin Design for Development Sub-Catchments
Filter Media Extended
Surface Area Filter Area
Catchment Sub-Catchment Depth Detention Depth
(m²) (m²)
(m) (m)
A N/A 180 180 0.7 0.3
3.9.4 Music Modelling
MUSIC modelling of the proposed catchments was performed to ensure the nominated treatment strategy achieves
the required pollutant reduction objectives. The target reductions in stormwater pollutants are based on comparing
an unmitigated scenario with no treatment on-site and the mitigated scenario with stormwater treatment measures
incorporated onto the site. Table 5 provides the modelling results for the treated catchment ‘A’. The MUSIC modelling
demonstrates that compliance has been met or exceeded for the objectives required by the Noosa Plan (2020) and
the SPP (2017) for TSS, TP, TN, and GP.
Table 5: Catchment A MUSIC Model Results
Reduction Target
Unmitigated Mitigated
Pollutant Achieved Reduction Compliance
(kg/yr) (kg/yr)
(%) (%)
TSS 2950 576 80.5 80 Y
TP 6.3 1.68 73.4 60 Y
TN 42.2 20.1 52.5 45 Y
GP 467 0 100 90 Y
3.10 Water and Sewerage
A sewer and water connection to the existing Unitywater networks will be provided for each of the proposed
allotments. A network analysis has been prepared for the proposed development. Refer to the “Water Supply and
Sewer Network Analysis” report by Covey Associates for further details.
4.0 CONCLUSION
The development of the 62 Lake Macdonald Drive site is proposed to provide 3 Community Use Lots and 1 Balance Lot
to support (if resolved by Council) the development of a maximum 130 units and future expansion of the Cooroy
Cemetery. Current Council resolution is for the development of Lot 1 for Community Housing only, no defined use has
been determined for Lot 2 or Lot 3.
The stormwater management proposal as outlined in this report achieves the water quality and treatment objectives
required under the Noosa Plan and Queensland Urban Drainage Manual 2017 (QUDM) by effectively treating
stormwater runoff where required.
A combination of underground and overland drains has been used to achieve the required stormwater quantity
outcomes for the development site, including stormwater connections for each allotment and external catchment
management.
Each allotment is provided with a sewer and water connection point to the existing Unitywater network. A water and
sewer network analysis has been prepared to support the connections, refer to the associated report.
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 10
233467 | M24-1037Rpt – Issue A – April 2025
Section 15
The engineering risks include:
• The unknowns regarding the final extent of contaminated material on site and the exact quantity which will
require off-site disposal. This factor can have significant impacts on the cost of construction.
• Connecting to existing Unitywater infrastructure requires crossing existing services. The depth of existing
water, electrical and communications services are assumed only and must be located (vacuum excavation
potholing) prior to construction which can affect the proposed design.
Please contact this office should further information be required.
62 Lake Macdonald Drive, Cooroy – Engineering Services Report Page 11
233467 | M24-1037Rpt – Issue A – April 2025
Section 16
APPENDIX A 62 Lake Macdonald Drive, Cooroy – Engineering Services Report 233467 | M25-1037Rpt – Issue A – April 2025
Section 17
Flood Hazard Assessment
Intersection of Lake Macdonald Dr
and Dianella Crt
Cooroy
September 2024
Section 18
The information contained in this report is subject to the disclaimers and definitions below.
This document has been prepared solely for the benefit of Noosa Council and is issued in confidence for the purposes only
for which it is supplied. Unauthorised use of this document in any form whatsoever is prohibited. No liability is accepted by
HydraLogic or any employee, contractor, or sub-consultant of HydraLogic with respect to its use by any other person. This
document may not be used, copied or reproduced in whole or part for any purpose other than that for which it was supplied
by HydraLogic.
This disclaimer shall apply notwithstanding that the document may be made available to other persons for an application
for permission or approval to fulfil a legal obligation.
© HydraLogic 2024
Document Control Sheet
Flood Hazard Assessment Intersection of Lake Macdonald Dr and Dianella Crt
Report Title
Cooroy
Affected Properties 62 Lake Macdonald Dr Cooroy
RP Description Lot 105 SP118458
Prepared For Noosa Council
Date 04 September 2024
Report Status Final v1.0
Author(s) Damian McGarry
Qualification BE Civil RPEQ MIEAust
Company HydraLogic
Phone 07 5444 7444
Certified by Damian McGarry
Industry Accreditation RPEQ No. 06045
Signed
Distribution Glen Conforti
C:\Users\Damian\Dropbox\002_HydraLogic\001_Projects\030_NSC\010_General Enquiries\029_Cooroy
Document Path:
Subdivision\006_Report\001_Draft\Flood Hazard Assessment Report Cooroy Subdivision dm 002.docx
Section 19
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
CONTENTS
Executive Summary ................................................................................................................................. 1
1 Introduction .................................................................................................................................... 1
2 Available Data ................................................................................................................................. 3
3 Site Characteristics .......................................................................................................................... 4
3.1 Catchment Characteristics..................................................................................................... 4
4 Hydraulic Modelling ........................................................................................................................ 6
4.1 Model setup........................................................................................................................... 6
4.1.1 Model boundaries ............................................................................................................. 6
4.2 Future climate ....................................................................................................................... 6
4.3 Model Roughness .................................................................................................................. 7
4.4 Validation............................................................................................................................... 7
5 Flood Hazard ................................................................................................................................. 11
6 Sensitivity Analysis ........................................................................................................................ 17
6.1 Manning’s n roughness sensitivity ...................................................................................... 17
6.2 Culvert blockage sensitivity ................................................................................................. 19
7 Hydraulic Performance ................................................................................................................. 22
8 Summary of findings ..................................................................................................................... 23
Appendices .............................................................................................................................................. 1
i
Section 20
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
FIGURES
Figure 1 - 50% AEP design discharge comparison................................................................................... 7
Figure 2 - 10% AEP design discharge comparison................................................................................... 8
Figure 3 - 2% AEP design discharge comparison..................................................................................... 8
Figure 4 - 1% AEP design discharge comparison..................................................................................... 8
Figure 5 - 1% AEP (2100) design discharge comparison ......................................................................... 9
Figure 6 - 0.2% AEP design discharge comparison.................................................................................. 9
Figure 7 - General flood hazard curves ................................................................................................. 11
Figure 8 - Duration of inundation Reference Point 1............................................................................ 13
Figure 9 - Duration of inundation Reference Point 2............................................................................ 13
Figure 10 - Sensitivity analysis +/- 25% Manning's n 2% AEP at Reference Pt A .................................. 17
Figure 11 - Sensitivity analysis +/- 25% Manning's n 1% AEP at Reference Pt A .................................. 18
Figure 12 - Sensitivity analysis +/- 25% Manning's n 0.2% AEP at Reference Pt A ............................... 18
Figure 13 - Sensitivity analysis 25% culvert blockage for 10% AEP at Reference Pt A ......................... 19
Figure 14 - Sensitivity analysis 50% culvert blockage for 2% AEP at Reference Pt A............................ 20
Figure 15 - Sensitivity analysis 50% culvert blockage for 1% AEP at Reference Pt A............................ 20
Figure 16 - Sensitivity analysis 50% culvert blockage for 0.2% AEP at Reference Pt A ........................ 21
ii
Section 21
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
EXECUTIVE SUMMARY
This report presents the findings of a flood hazard assessment undertaken for the road intersection
of Lake Macdonald Dr and Dianella Crt in Cooroy.
This report describes the configuration of the local high resolution flood model and summarises the
hydraulic performance of the intersection under a range of design flood conditions with Annual
Exceedance Probabilities of between 50% AEP and 0.2 % AEP.
Detailed ground and feature survey provided by Murray & Associates (see Appendix A) shows three
pipe culvert cells passing beneath Lake Macdonald Dr from the southeast corner of the intersection
with Dianella Ct to the northwest corner of the intersection adjacent to Wilgee Ct. Two of pipe
culverts are shown to be 1050 mm diameter and the third is 1350 mm diameter.
For the 10% AEP design flood event the intersection is not inundated and hence no flood hazard
exists within the trafficable road corridor. For the 2% AEP design flood event, shallow inundation at
the peak of the flood event introduces a low (H1) flood hazard classification across the intersection
with areas of higher classification where flow across the road concentrates and returns to the main
waterway, see Map 5. The flood hazard classifications are similar for the 1% AEP design flood event,
however, a more prominent corridor of higher (H5) flood hazard exists across the intersection, see
Map 6.
The duration of inundation across the intersection for the 2% AEP and 1% AEP design flood events is
anticipated to be less than 1.5 hours. The actual duration of inundation will vary for each major
rainfall event experienced in the local catchment; however, the approximate duration of the design
flood event provides a reasonable indication of the duration of inundation which is also consistent
with the size of the upstream catchment that contributes flood flows to the intersection location.
The intersection is flood free and trafficable for events up to the 10% AEP.
Detailed flood modelling of the catchment and subject intersection has demonstrated the capacity
of the existing culverts provides 10% AEP design flood immunity to the intersection. For larger and
rarer flood events of less than 2% AEP the model results show the intersection will experience water
over the road to depths of less 0.3 m for a 1% AEP flood event for relatively short durations of less
than 1.5 hours.
The flood modelling has also demonstrated that should a significant blockage of the culverts occur
during a major rainfall flood event the depths of inundation across the culvert would not be
expected to significantly change, however, the inundation across the intersection would persist for
longer periods.
The hydraulic performance of the intersection culverts is summarised in Table E -1 below.
E1
Section 22
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
Table E 1 - Hydraulic performance of intersection culverts
Discharge Depth Velocity Water
AEP surface
Culverts Weir Weir Weir elevation*
(%) (1 in x) (m3/s) (m3/s) (m) (m/s) (m AHD)
0.2 500 11.1 18.8 0.16 1.79 103.8
1 (2100) 100 (2100) 10.7 15.8 0.14 1.69 103.77
1 100 10.3 8.2 0.07 1.36 103.67
2 50 10.1 5.7 0.05 1.21 103.6
10 10 8.7 0 0.00 0.00 103.3
50 2 3.7 0 0.00 0.00 102.5
* Upstream face
E2
Section 23
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
1 INTRODUCTION
Noosa Council approached HydraLogic to provide a summary of the design flood conditions at the
intersection of Lake Macdonald Drive and Dianella Court in Cooroy.
The crossing is portrayed as being inundated in Council’s strategic planning and disaster
management maps.
The watercourse and catchment associated with the culvert crossing at this location lie within the
2018 Six Mile Creek flood model prepared by WMA Water for Noosa Council.
An initial review of the flood model results revealed the local tributary was only defined in the flood
study model to determine design flood inflows to the main branch of Six Mile Creek downstream of
Cooroy township. The road culvert crossings along this local tributary were not defined in the flood
model.
To enable a detailed summary of the design flooding conditions of the intersection to be prepared a
higher resolution flood model was developed for the local tributary. This local flood model includes a
higher resolution digital terrain model and the pipe culverts at Lake Macdonald Dr, Curlew Cresent,
and Swift Drive.
This report describes the configuration of the local high resolution flood model and summarises the
hydraulic performance of the intersection under a range of design flood conditions with Annual
Exceedance Probabilities of between 50% AEP and 0.2 % AEP.
The intersection and local catchment are shown in Map 1.
1
Section 24
LAKE MACDONALD DR DIANELLA CT INTERSECTION FLOOD ASSESSMENT vd > NOOSA Council (_] Study area [__] Cooroy Subdivision [_] Model catchment Cadastre Watercourses [) Model Catchment QLD Globe Imagery 0 100 200 m = Hydral_ogic Date Created : 03.09.2024 Created by : DGM Projection : EPSG:28356 GDA94 / MGA zone 56 Scale at A3 Map Ref 1: 5,000 i 1 Map Series Location
Section 25
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
2 AVAILABLE DATA
Table 2-1 presents a summary of the data utilised to inform this investigation.
Table 2-1 Available Data
Data Source Comments
2022 LiDAR Digital Elevation
Topographic details Provided by Noosa Council
Model
2018 Six Mile creek Flood Study
Catchment Boundaries
2022 DEM
Determined from aerial image
Land Use Google Satellite
assessment
Watercourse flow hydrographs
Hydrologic design flood runoff extracted from flood model
hydrographs results from the 2018 Six Mile
Creek Flood Study
Watercourse stage hydrographs
Hydraulic tailwater boundary extracted from flood model
hydrographs results from the 2018 Six Mile
Creek Flood Study
Contour & Detail Survey of
Lot 105 on SP 118458 Dated 05.04.24
Survey and infrastructure plans 62 Lake McDonald Drive, Job number 100988 DTM
Cooroy prepared by Murray & See Appendix A
Associates
Issue A
62 Lake Macdonald Drive, Cooroy Dated 10.01.24
Road upgrade details
prepared by Covey Associates Ptd Job number 233467 C250 – 252
Ltd See Appendix B
3
Section 26
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
3 SITE CHARACTERISTICS
The subject site is the intersection of Lake Macdonald Dr and Dianella Ct in Cooroy.
Detailed ground and feature survey provided by Murray & Associates shows three pipe culvert cells
passing beneath Lake Macdonald Dr from the southeast corner of the intersection with Dianella Ct
to the northwest corner of the intersection adjacent to Wilgee Ct. Two of pipe culverts are shown to
be 1050 mm diameter and the third is 1350 mm diameter.
The Swift Drive culvert is a 1350 mm diameter and the Curlew Crs crossing is a 750 mm diameter.
Invert levels for these pipe culverts were determined from the 2022 digital elevation model (DEM).
3.1 Catchment Characteristics
Upstream of the subject site, the local catchment extends to the southeast and northeast and covers
an area of approximately 70 hectares. The catchment is comprised of three sub-tributaries. The
larger two of these sub-tributaries have a confluence downstream of Swift Dr and Curlew Crs. A third
minor tributary drains from southwest and joins the main tributary watercourse approximately 450
m upstream of the subject site. There is also a minor inflow to the main tributary from the north just
upstream of the subject site. The tributary waterway corridor is well defined by adjacent elevated
topography.
4
Section 27
LAKE MACDONALD DR
DIANELLA CT
INTERSECTION
FLOOD ASSESSMENT
SY
ae a
[__] Cooroy Subdivision
(__] Study area
{__] Upstream catchment
Cadastre
~—— Watercourses
[) Model Catchment
DEM 2022 (mAHD)
Hi 93
[J 112
[| 126
[J 140
Hg 155
QLD Globe Imagery
0
|
Hydral_ogic
Date Created : 03.09.2024
Created by : DGM
Projection : EPSG:28356 GDA94 / MGA zone 56
Scale at A3
1: 5,000
Digital
Elevation
Model
Map
Series
Section 28
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
4 HYDRAULIC MODELLING
4.1 Model setup
To determine the potential flooding conditions of the Lake Macdonald Dr and Dianella Crt
intersection a high-resolution HEC RAS (Version 6.5) 2D flood model was developed for the local
catchment and watercourse.
The terrain base for the flood model was a 2022 digital elevation model provided by Noosa Council
derived from aerial laser survey (LiDAR).
The flood model included the entire contributing local catchment area upstream of the subject site
and extended approximately 450 m downstream to a confluence with another minor tributary.
A 2D model grid spacing of 5 m was adopted to ensure the accuracy of the terrain representation
throughout the waterway corridor. The 5 m grid was tested against a 2m grid and produced
consistent results.
Breaklines were incorporated to improve the model’s representation of significant changes in
surface elevation, land use and flow paths.
4.1.1 Model boundaries
To maintain consistency with the Six Mile Creek flood model, tailwater boundary conditions and
upstream tributary flows were extracted from the model and applied to the high-resolution local
flood model.
The downstream boundary of the local flood model was established as a time varying water level
hydrograph. Upstream of the subject site time varying discharge hydrographs were also extracted
from the Six Mile Creek flood model at five reference locations and used as inflow boundaries in the
local model, see Map 3.
Design tailwater level and instream flow hydrographs were extracted from the Six Mile Creek flood
model results for the following design flood events:
50% AEP (1 in 2 AEP)
10% AEP (1 in 10 AEP)
1% AEP (1 in 100 AEP)
1% AEP (1 in 100 AEP) 2100
0.2% AEP (1 in 500 AEP)
4.2 Future climate
As a part of the Six Mile Creek flood study, the Cooroy Creek flood model adopted a climate
change/variability rainfall allowance of a 20% increase in rainfall intensity at year 2100.
6
Section 29
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
4.3 Model Roughness
The observed land uses for the 2D model surface for the existing catchment condition is shown in
Map 3.
The corresponding Manning’s n surface roughness values for each surface type are presented in
Table 4-1.
Table 4-1 Flood model surface roughness
Catchment Surface Assumed
Manning’s n
Openspace 0.08
Residential 0.12
Rural residential 0.06
Waterway 0.12
Roads 0.015
4.4 Validation
Design discharge hydrographs were exported from the local high-resolution flood model results
immediately upstream of the intersection and compared to design discharges extracted from the
Cooroy Creek flood model.
Design discharge hydrographs show good consistency across all flood events. Refer to Figure 1 to
Figure 6.
Figure 1 - 50% AEP design discharge comparison
7
Section 30
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
Figure 2 - 10% AEP design discharge comparison
Figure 3 - 2% AEP design discharge comparison
Figure 4 - 1% AEP design discharge comparison
8
Section 31
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
Figure 5 - 1% AEP (2100) design discharge comparison
Figure 6 - 0.2% AEP design discharge comparison
9
Section 32
LAKE MACDONALD DR
DIANELLA CT
INTERSECTION
FLOOD ASSESSMENT
oa NOOSA
Council
@ Sensitivity Ref Pt copy
(__] Study area
[_] Model catchment
{__] Cooroy Subdivision
Cadastre
--- Breaklines
— Inflow locations
—— Regional tailwater boundary|
[) Model catchment
Study Area Landuse
(HN Openspace
[__] Residential
[__] Roads
[] Rural Res
Waterway
QLD Globe Imagery
0 100 200 m
kz €6=—CSCS
Hydra
Date Created : 03.09.2024
Created by : DGM
Projection : EPSG:28356 GDA94 / MGA zone 56
Scale at A3 Map Ref
1: 5,000 iy 3
Map Local Flood Model
Series Configuration
Section 33
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
5 FLOOD HAZARD
Australian Rainfall and Runoff (ARR) A Guide to Flood Estimation, Book 6 – Flood Hydraulics
presents a series of general flood hazard curves based on depth and velocity, see Figure 7. The flood
hazard classifications of H1 to H6 describe the six classifications of flood hazard detailed in Table 5-1.
The depth velocity flood hazard classification limits are presented in Table 5-2.
Figure 7 - General flood hazard curves
Table 5-1 Flood hazard classifications
Flood Hazard Description
Classification
H1 Generally safe for vehicles, people and buildings
H2 Unsafe for small vehicles
H3 Unsafe for vehicles, children and the elderly
H4 Unsafe for vehicles and people
Unsafe for vehicles and people. All building types vulnerable to structural damage. Some
H5 less robust
building types vulnerable to failure.
H6 Unsafe for vehicles and people. All building types considered vulnerable to failure.
Table 5-2 Depth and Velocity Vulnerability Threshold Classification Limits
11
Section 34
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
Flood Hazard Classification limit Limiting still water depth Limiting velocity
Classification (D and V in combination) (D) (V)
m2/s m m/s
H1 D*V ≤ 0.3 ≤ 0.3 ≤ 2.0
H2 D*V ≤ 0.6 ≤ 0.5 ≤ 2.0
H3 D*V ≤ 0.6 ≤ 1.2 ≤ 2.0
H4 D*V ≤ 1.0 ≤ 2.0 ≤ 2.0
H5 D*V ≤ 4.0 ≤ 4.0 ≤ 4.0
H6 D*V > 4.0 - -
Flood hazards for the subject site intersection have been determined for the 10% AEP, 2% AEP, and
1% AEP design flood events in accordance with the guidance in ARR Book 6 and are presented in
Map 4 to Map 6.
For the 10% AEP design flood event the intersection is not inundated and hence no flood hazard
exists within the trafficable road corridor, see Map 4. For the 2% AEP design flood event, shallow
inundation at the peak of the flood event introduces a H1 flood hazard classification across the
intersection with areas of higher classification where flow across the road concentrates and returns
to the main waterway, see Map 5. The flood hazard classifications are similar for the 1% AEP design
flood event, however, a more prominent corridor of higher H5 flood hazard exists across the
intersection, see Map 6.
Depth hydrographs were extracted from two reference points to determine the approximate
duration of inundation that could be anticipated for inundation of the intersection. The depth
hydrographs for the reference points shown on Map 6 are presented in Figure 8 and Figure 9. The
figures show the duration of inundation for the 2% AEP and 1% AEP design flood events to be less
than 1.5 hours. The actual duration of inundation will vary for each major rainfall event experienced
in the local catchment; however, the approximate duration of the design flood event provides a
reasonable indication of the duration of inundation which is also consistent with the size of the
upstream catchment that contributes flood flows to the intersection location.
The intersection is flood free and trafficable for events up to the 10% AEP.
12
Section 35
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
Figure 8 - Duration of inundation Reference Point 1
Figure 9 - Duration of inundation Reference Point 2
13
Section 36
45 4 40 4 35 4 3.0 4 25 4 Depth (m) 20 4 15 4 10 4 Os 4 H6 - unsafe for vehicles and people. All building types considered vulnerable to failure. HS - unsafe for vehicles and people. All buildings vulnerable to structural damage. Some less robust building types vulnerable to failure. H4 - unsafe for people and vehicles. H8 - unsafe for vehicles, children and the elderly = He - unsafe for small vehicles 0.0 0 H1- generally safe | for people, vehicles and buildings 9 10 20 3.0 Velocity (m/s) 40 5.0 LAKE MACDONALD DR DIANELLA CT INTERSECTION FLOOD ASSESSMENT v.¢ NOOSA | #®& Council Cadastre () Study area Hazard 10% AEP [J H1 [| H2 [#3 [] H4 [] H5 [] H6 QLD Globe Imagery 0 10 20 30 40m EZ) Hydral_ogic Date Created : 03.09.2024 Created by : DGM Projection : EPSG:28356 GDA94 / MGA zone 56 Scale at A3 Map Ref 1: 900 Map 10% AEP Series Flood Hazard
Section 37
LAKE MACDONALD DR DIANELLA CT INTERSECTION FLOOD ASSESSMENT SY 1 ae NOOSA Cadastre () Study area Hazard Classification [J H1 [| H2 [#3 [] H4 [] H5 [] H6 QLD Globe Imagery 45, -| H6- unsafe for vehicles and people Alll building types considered vulnerable to failure. 0 10 20 30 40m EZ) 3.0 + H5 - unsafe for vehicles and people. All buildings vulnerable to structural damage. Some less robust building types. Depth (m) 25 7 vuinerable to failure Hydral_ogic 20 4 Date Created : 03.09.2024 . Created by : DGM H4 - unsafe Projection : EPSG:28356 GDA94 / MGA zone 56 15 4 forpeople ° and vehicles: Scale at A3 Map Ref 1.0 +) H3 - unsafe» for vehicles, children and the elderly os 4 = H2 - unsafe for small vehicles H1- generally safe ee for people, vehicles and buildings 00 10 20 3.0 40 5.0 Velocity (m/s) 1: 900 Map 2% AEP Series Flood Hazard 00
Section 38
4.5 4 46-unsafe for vehicles and people. ° All building types considered vulnerable to failure. 35 4 3.0 7 HS - unsafe for vehicles and people. All buildings vulnerable to structural damage. Some less robust building types 25 7 \uinerable to failure Depth (m) 20 4 H4 - unsafe J for people 15 1 and vehicles [J H1 [] H2 [J 43 [| 4 [] H5 [__] H6 QLD Globe Imagery 0 10 LAKE MACDONALD DR DIANELLA CT INTERSECTION FLOOD ASSESSMENT SY 7 ae NOOSA @ Road Reference Pt Cadastre (_] Study area Hazard001 copy EZ) Hydral_ogic Date Created : 03.09.2024 Created by : DGM Projection : EPSG:28356 GDA94 / MGA zone 56 20 30 40m 1.0 + H3-unsafe» for vehicles, children and the elderly os 4 — He - unsafe for small vehicles H1- generally safe | pumas for people, vehicles and buildings 7 00 0.0 10 20 3.0 40 5.0 Velocity (m/s) Scale at A3 Map Ref 1: 900 6 Map 1% AEP Series Flood Hazard
Section 39
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
6 SENSITIVITY ANALYSIS
To test the sensitivity of the high-resolution local flood model to modest changes in adopted
parameter values, two sensitivity tests were conducted. A reference point (A) was adopted at the
road entrance to Dianella Crt where hydrographs were extracted from the flood model and
compared to the base case results. See Map 3 for reference point location.
6.1 Manning’s n roughness sensitivity
The first sensitivity test was conducted using a +/- 25% variation in the adopted Manning’s n surface
roughness value for the model. The adopted Manning’s n surface roughness values are shown in
Table 4-1.
Water level (Depth) hydrographs were extracted from the results of each sensitivity analysis at
reference point A and compared to the base case results for the 2% AEP, 1% AEP, and 0.2% AEP
design flood events. See Figure 10 to Figure 12.
The results show the design flood levels at the intersection are not sensitive to reasonable changes
in the adopted Manning’s n surface roughness.
Figure 10 - Sensitivity analysis +/- 25% Manning's n 2% AEP at Reference Pt A
17
Section 40
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
Figure 11 - Sensitivity analysis +/- 25% Manning's n 1% AEP at Reference Pt A
Figure 12 - Sensitivity analysis +/- 25% Manning's n 0.2% AEP at Reference Pt A
18
Section 41
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
6.2 Culvert blockage sensitivity
The second sensitivity test assumed an amount of blockage of the available waterway area of the
three pipe culverts which pass beneath the subject site intersection. A blockage factor was applied
based on the Australian Rainfall and Runoff Book 6 Chapter 6 guidelines. An assumed Debris
Potential (DP) of medium was adopted and an L10 value of 1.5 m assumed. The smaller culvert pipe
diameter of 1050 mm was applied as the inlet width (W) control dimension. Based on guidelines a
blockage factor of 25% was applied to the 50% AEP and 10% AEP flood event, and 50% to the 2%
AEP, 1% AEP, and 0.2% AEP flood events.
Water level (Depth) hydrographs were extracted from the results of each sensitivity analysis at
reference point A and compared to the base case results for the 10% AEP, 2% AEP, 1% AEP, and 0.2%
AEP design flood events. See Figure 13 to Figure 16.
The results show that shallow inundation to a depth of approximately 100 mm is introduced at
reference point A for the 10% AEP design flood event, see Figure 13. For the 2% AEP, 1% AEP, and
0.2% AEP design flood events inundation depths across the intersection at reference point A
increase by approximately 120 mm to 150 mm with the durations of inundation also increasing to
between 2 hours and 6 hours respectively.
The results demonstrate that for flood events with AEPs less than 10% flooding conditions across the
intersection do not change significantly in depth, however, durations of inundation may be
extended.
Figure 13 - Sensitivity analysis 25% culvert blockage for 10% AEP at Reference Pt A
19
Section 42
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
Figure 14 - Sensitivity analysis 50% culvert blockage for 2% AEP at Reference Pt A
Figure 15 - Sensitivity analysis 50% culvert blockage for 1% AEP at Reference Pt A
20
Section 43
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
Figure 16 - Sensitivity analysis 50% culvert blockage for 0.2% AEP at Reference Pt A
21
Section 44
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
7 HYDRAULIC PERFORMANCE
The hydraulic performance of the waterway crossing intersection is summarised in Table 7-1.
The hydraulic performance is based on the adopted flood model parameters and does not include
potential significant blockage of the culverts.
Table 7-1 - Hydraulic performance of intersection culverts
Discharge Depth Velocity Water
AEP surface
Culverts Weir Weir Weir elevation*
(%) (1in x) (m3/s) (m3/s) (m) (m/s) (m AHD)
0.2 500 11.1 18.8 0.16 1.79 103.8
1 (2100) 100 (2100) 10.7 15.8 0.14 1.69 103.77
1 100 10.3 8.2 0.07 1.36 103.67
2 50 10.1 5.7 0.05 1.21 103.6
10 10 8.7 0 0.00 0.00 103.3
50 2 3.7 0 0.00 0.00 102.5
* Upstream face
22
Section 45
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
8 SUMMARY OF FINDINGS
Detailed flood modelling of the catchment and subject intersection has demonstrated the capacity
of the existing culverts provides 10% AEP design flood immunity to the intersection. For larger and
rarer flood events of less than 2% AEP the model results show the intersection will experience water
over the road to depths of less 0.3 m for a 1% AEP flood event for relatively short durations of less
than 1.5 hours.
The flood modelling has also demonstrated that should a significant blockage of the culverts occur
during a major rainfall flood event the depths of inundation across the culvert would not be
expected to significantly change, however, the inundation may persist for longer periods.
23
Section 46
Flood Hazard Assessment
Intersection of Lake Macdonald Dr and Dianella Crt
APPENDICES
Appendix A - Contour & Detail Survey prepared by Murray & Associates
Section 47
gul
ly p Ele
it Pit ct.
OP
E 4 M 19 rcp d300
conc. path
N 7 9159 3502 rcp d375 gul
ly p
RL 0791 2.19
7 it conc. path
10 5
2.9 5.51
74 4
TE
103
.
00
0
rcp d60
LI 10
4.
SV
00
TE
ma ma ma
il il il rc p
co
bo
bo
x x bo
x ath d1
conc.
nc
35
d/way
.
ma .p
conc.
rc
d/way
il nc si g
p
TE . 00 rcp 0
conc.
bo EP T WM WM TE co
pa
d/way
x L E
10 5 d
conc.
00 "D i n
104
d6
d/way
WM
00
th
EP W M an
1
106 .
.
e
ASSOCIATES
rcp 1050
MURRAY &
03 . 00
75
. 00 lla
d6
FH L EP d1 00
L FH conc. path 05 Ct "
SURVEYORS & TOWN PLANNERS
104
0
107 .00
rc p
SV TE
WM
kerb & channel FH
ath edge of bitumen IVE gul SV
c. p LAKE MACDONALD DR ly p rcp
rcp d
EP it
00
c on d30
#1 road centerline 0
d6
513 gul
375
54 tre fiel
rcp d600 ly p
1 d4 e pit d SV SMH si g it
rcp
00 edge of bitumen EP "g i n
#9 ve
conc. path
ACN 075 543 154
con
690 1 trans
5 2 8 .9 6 E P LI gul way"
c
bank '05" f or L ly p LI
me it
107 .
5 2 °2 4
0
r
. pa
108 . 0 00
gr o
th
. 00
d60
tre
109 . 0
00 mo undw
107 EP EP Section 48
62°51'50" d5 e nito ate
rcp
#5 #9 148.142 00 ring r
690 we
211
1 4 tre
e ll
tre tre tre tre d300
d5 e
110 .00
tre tre
e d5 e e fiel
d
00 d4 e
00 s 00 d8
00 p it
tre d5 e
00 tre
tre d4 e d1 e
00 tre tre 00
d4 e 0
road cent
.00 d4 e d4 e
00 tr 11 1 00 00 tre
e tre tre
d5 e
d4 e d3 e 00
kerb & chan
00 tre d4 e tre 00
reline
00
d4 e
nel
d4 e
Murray Building,15-17 Currie St. Nambour Ph.(07)5441 2188 P.O. Box 246
00 tr 00
OP e tre
e
kerb & channel
d4 e
E 4 M 17 00 tre . 00 108
. 00
rcp d450
N 7 9139 8243 d4 e 112
00
Branch Offices at Maroochydore Caboolture Chinchilla Roma Gympie & Emerald
RL 0790 3.91 tre
10 1 0 tre
8.1 9.91 d4 e
38 4 00 d6 e
00 tre
gr o . 00
tre
rcp d45
109 d3 e
00
0
d4 e
3 .00 mo undw
00 11 nito ate
line of small trees
tre tre SM
H
PP
tre ring r
CP
BM
SW
AV
ELP
d6 e d5 e
EPL
EMH
00 we 00
EPIT
d4 e
00 ll MH
tre 0
tre e
1
. 00
d5 . 00 04 . 0
d4 e 00 110
00
105
tre . 00 tre
Air Valve
d4 e 114 TE
00 d5 e 00
ba 00 1
6.
Bench Mark
Power Pole
fiel
d EP
L
Control Point
nk SP
Electricity Pit
tre 10 p it 176
Electricity Pillar
d5 e 96
Elect. Light Pole
00 27 8
Electricity Manhole
1 0 8 °5 0 00
9.3 '1 tre 1.
11
DIA
41 0" d5 e
00
S
FH
SV
N
SMH
GAS
GATE
SWMH
00
GRATE
E
5. .00
11 107
Sign
Gate
LL
tre
A
d5 e
Fire Hydrant
00 clu
fenceline
of m p
C
Scower Valve
tre t re clu
es
Sewer Manhole
28
Stormwater Grate
d6 e of m p SP
Gas Infrastructure
00 00 t re 176
es 96
OU
The text continues on section 49.
Used in these records
Final Engineering services report _62 Lake Macdonald Drive.pdfRelated documentApplication case desk ↗
About this file
- File size
- 27.0 MB (very large file)
- File type
No other editions are linked here.
Original file
Log in to download the original file
The download may take a few minutes. On mobile data, it is best to wait for Wi-Fi.