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Integrated Water Management Plan
Noosa Marketplace : 2-20 HOFMANN DRIVE
Integrated Water
Management Plan
Noosa Marketplace : 2-20 HOFMANN
DRIVE
V190428
Prepared for
Blueprint
15 May 2019
15 May 2019 Cardno i
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Full text of sections 2 to 30 (of 107)
Section 2
Integrated Water Management Plan
Noosa Marketplace : 2-20 HOFMANN DRIVE
Contact Information Document Information
Cardno (Qld) Pty Ltd Prepared for Blueprint
ABN 57 051 074 992
Project Name Noosa Marketplace : 2-20
HOFMANN DRIVE
Level 11
515 St Paul’s Terrace
File Reference V190428_IWMP_V3.docx
Fortitude Valley QLD 4006
Australia Job Reference V190428
www.cardno.com Date 15 May 2019
Phone +61 7 3369 9822
Version Number 3
Fax +61 7 3369 9722
Author(s):
Lisa Holden Effective Date 15/05/2019
Engineer
Approved by:
Helen Doherty Date Approved 15/05/2019
Senior Engineer
Document History
Version Effective Date Description of Revision Prepared by Reviewed by
1 17/04/2019 DRAFT LMH TH
2 18/04/2019 FINAL LMH TH
3 15/05/2019 Final Updated Dev Drawings ZM/LH HD
& MUSIC model
© Cardno 2019. Copyright in the whole and every part of this document belongs to Cardno and may not be used, sold, transferred, copied or reproduced in
whole or in part in any manner or form or in or on any media to any person other than by agreement with Cardno.
This document is produced by Cardno solely for the benefit and use by the client in accordance with the terms of the engagement. Cardno does not and
shall not assume any responsibility or liability whatsoever to any third party arising out of any use or reliance by any third party on the content of this
document.
V190428 | 15 May 2019 | Commercial in Confidence ii
Section 3
Integrated Water Management Plan
Noosa Marketplace : 2-20 HOFMANN DRIVE
Table of Contents
1 Introduction 3
2 Site Description and Proposed Development 4
2.1 Site Description 4
2.2 Land Encumbrances 4
2.3 Proposed Development 5
2.4 Lawful Points of Discharge 5
3 Hydrology 6
3.1 Background 6
3.2 Model Setup 6
4 Stormwater Quantity Management 11
4.1 Background 11
4.2 Model Setup 11
4.3 Model Results 12
5 Stormwater Quality Management 14
5.1 Stormwater Quality Objectives 14
5.2 Proposed Stormwater Quality Treatment 15
5.3 Construction Phase Water Quality Management 19
5.4 Maintenance 19
6 Hydraulic Analysis 20
6.1 Introduction 20
6.2 Model Setup 20
6.3 Modelled Events 20
6.4 Results 20
7 Conclusions 24
Appendices
Appendix A – Development Layout
Appendix B - Flooding Results
Appendix C – Treatment Devices
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Tables
RAFTS Catchments ................................................................................................................. 8
Table 3-2 Initial and Continuing Losses for RAFTS Modelling ................................................................ 8
Rational Method Verification .................................................................................................... 9
Peak Flows (m3/s) .................................................................................................................. 10
Local Catchment Parameters ................................................................................................ 11
Table 4-2 Proposed Detention Storage Tank Characteristics ................................................................ 12
Table 4-3 Peak XP-RAFTS Discharge ................................................................................................... 12
Table 4-4 Rainwater Tank Storage Volume .......................................................................................... 13
Table 5-1 Rainwater Tanks MUSIC Details ........................................................................................... 16
Rainfall Runoff Parameters for Commercial Source Nodes .................................................. 16
Pollutant Export Parameters for Commercial Source Nodes ................................................ 16
Catchment Areas and Proposed Stormwater Treatment ....................................................... 18
MUSIC Model Results ............................................................................................................ 19
Table 6-1 Existing Flood Level (mAHD) ................................................................................................. 22
Table 6-2 Developed Flood Level (mAHD) ............................................................................................ 22
Table 6-3 Flooding Impacts (m) ............................................................................................................. 23
Figures
Figure 2-1 Subject Site Location 4
Figure 2-2 Existing Site Drainage (Noosa Council Enterprise Mapping System) 5
Figure 3-1 RAFTS Catchments 6
Figure 5-2 MUSIC Model Layout 17
Figure 5-3 MUSIC Model Catchments 18
Figure 6-1 Locations of Interest 21
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Section 5
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1 Introduction
Cardno has been engaged by Blueprint to prepare an Integrated Water Management Report to support the
Development Application (DA) for the proposed Noosa Marketplace. The site is located within the Noosa
Council local government area on Lots SP222982 and SP246584, addressed at 20 and 2-18 Hofmann Drive
respectively shown in Figure 2-1 below.
This report provides engineering advice to address issues relating to stormwater quantity and quality, as well
as flooding of the subject site.
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2 Site Description and Proposed Development
2.1 Site Description
The site has an area of approximately 3.58 ha, of which approximately 1.4 ha will be developed into retail
outlets and associated commercial use. The development is to be zoned as ‘Shire Business Centre’ in
accordance with the Noosa Plan Zones 2016. The subject site is bounded by existing commercial/light
industrial use to the west, Hofmann Drive to the east, with Eenie Creek Road running alongside the northern
boundary. Currently, the area is densely grassed, with a general fall towards the southern boundary. Existing
levels vary from RL 9.0 mAHD at the northwest corner of the site, to RL 6.0 mAHD on the southern boundary.
Located nearby is the Noosa Civic Shopping Centre to the east. Figure 2-1 shows the site locality/boundary.
Figure 2-1 Subject Site Location
2.2 Land Encumbrances
Both lots are subject to a number of easements and covenants. Located on the northern boundary of the
subject site, and adjoining the eastern edge alongside Hofmann Drive, is an environmental covenant to
preserve native vegetation on site. Running through the site from north to south is a drainage easement
designed to capture overland flow from the wider catchments and discharge into the downstream
environmental reserve. Finally, located to the south of the site, on the eastern boundary is an environmental
covenant to preserve native vegetation. It is noted that this land cannot be cleared or used to treat stormwater
flows discharging from the site. The existing easement and covenant plan is located in the development
drawings (Appendix A). It is assumed that the easements noted above will be modified to suit the proposed
development as required.
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2.3 Proposed Development
The proposed development involves the construction of a mixed use marketplace development. This will
include 24 tenancies, with associated car parking and roadways for loading facilities.
2.4 Lawful Points of Discharge
The lawful point of discharge for the site is the 4 by 1200 mm x 600 mm RCBCs under Hofmann Road, located
adjacent to the South East boundary on Lot 5 SP222982. Flows leaving the site will drain south along the
eastern side of the site into these pipes, (circled below). Existing site drainage is shown in Figure 2-2.
Figure 2-2 Existing Site Drainage (Noosa Council Enterprise Mapping System)
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3 Hydrology
3.1 Background
Situated to the north and north-west of the subject site is an external catchment covering an area of
approximately 7.18 ha. As mentioned previously, the lawful point of discharge for the site is to the south into
an existing drainage network. Based on the Noosa Council Enterprise Mapping system, the subject site is not
located in the flood hazard area for a 1% AEP event. Although records indicate that the site is outside the flood
hazard area, a detailed hydrological and hydraulic investigation has been undertaken to determine the effects
of the proposed development on flood levels in the area and to ensure that the proposed development does
not result in negative impacts on adjacent properties.
3.2 Model Setup
3.2.1 Catchment delineation
Local catchments were calculated by interrogation of the DEM and drainage lines. The catchment boundaries
are shown in Figure 3-1.
Figure 3-1 RAFTS Catchments
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3.2.2 Rainfall Parameters
Rainfall parameters input to RAFTS were sourced using ARR 2016 BOM IFD values.
3.2.3 RAFTS Parameters
Catchment characteristics are shown in Table 3-1. For the purposes of this hydrological model, land uses were
defined as per existing use. Catchment slopes were determined using drainage lines for each catchment.
Manning’s values were set to 0.045 for pervious areas and 0.015 for impervious areas as per Chapter 4.1 of
the Noosa Planning Scheme-Policy 5-Engineering Design Standards. Initial and continuing losses were set
using the ARR data hub depending on the event that was being modelled as shown in Table 3-2. While ARR
2016 sets out a method for determining initial and continuing losses for events and catchments, the adopted
approach is considered to be conservative. A lag time of 1 minute was applied to the model between the
upstream and downstream boundaries of the site to best represent existing conditions.
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RAFTS Catchments
Catchment Total Area Percentage Impervious Vectored Slope Catchment Manning’s 'n'
ID (ha) (%) (%) Perv/Imperv
1 2.31 95 2.96 0.045/0.015
2 0.77 95 5.10 0.045/0.015
3 0.60 95 5.20 0.045/0.015
4 0.69 95 3.36 0.045/0.015
5 1.17 50 3.39 0.045/0.015
6 0.34 0 1.81 0.045/0.015
7 0.18 0 1.22 0.045/0.015
8 1.15 95 1.34 0.045/0.015
9 0.46 95 1.56 0.045/0.015
10 0.88 50 1.41 0.045/0.015
11 0.09 50 0.31 0.045/0.015
12 0.06 95 0.84 0.045/0.015
13 0.14 5 1.86 0.045/0.015
14 0.53 5 2.07 0.045/0.015
15 0.54 0 0.78 0.045/0.015
16 0.16 5 0.09 0.045/0.015
17 0.45 0 2.48 0.045/0.015
18 0.17 35 3.58 0.045/0.015
19 0.14 0 1.52 0.045/0.015
20 0.42 5 1.28 0.045/0.015
21 1.53 95 0.92 0.045/0.015
Table 3-2 Initial and Continuing Losses for RAFTS Modelling
AEP Event Initial and Continuing Losses
1% 0mm IL/2mm/h CL
2% 5mm IL/2mm/h CL
5% 5mm IL/2mm/h CL
10% 10mm IL/2mm/h CL
20% 10mm IL/2mm/h CL
39% 10mm IL/2mm/h CL
A range of design storms were modelled with 10 differing temporal patterns and multiple durations as per ARR
2016. The maximum median storm was then used as the peak design flow.
3.2.4 Rational Method Verification
The peak flows determined using RAFTS were compared with peak flows determined using the Rational
Method. Catchments 2 and 3 were chosen for this comparison due to having clearly defined drainage lines
and catchment boundaries. C10 values were sourced using Table 4.5.3 of the Queensland Urban Drainage
Manual 2017. The results of this verification are shown in Table 3-3 below for the 1% AEP event. It was found
that the RAFTS model produced higher peak flows than the Rational Method for Catchments 2 and 3. The
RAFTS flows were therefore considered acceptable.
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Rational Method Verification
Parameter Value
Catchment 2 Catchment 3
C10 0.70 0.70
tc (min) 10.68 9.07
I (1yr,10min) 102 102
A (ha) 0.77 0.60
Rational Method Flow (m3/s) 0.46 0.38
RAFTS Peak Flow (m3/s) 0.74 0.58
Difference (m3/s) 0.29 0.20
3.2.5 Results
Peak flows for each of the sub catchments are listed in Table 3-4 for the 1% AEP event. The critical storm
duration for 1%, 2% and 5% AEP events was determined to be 15 minutes, while, for the 39% and 20% AEP
events, the times of concentration was 25 minutes. For the 10% AEP event, the time of concentration was 20
minutes. This difference in time of concentration was considered to be typical for models run with ARR 2016
rainfall patterns. In addition to the peak flows coming from each catchment, the peak total flow from the site
was found to be 1.84 m3/s in the 1% AEP event.
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Peak Flows (m3/s)
Catchment ID Peak Flow (m3/s)
1 2.19
2 0.74
3 0.58
4 0.67
5 0.87
6 0.18
7 0.09
8 1.06
9 0.44
10 0.57
11 0.05
12 0.06
13 0.10
14 0.31
15 0.14
16 0.02
17 0.24
18 0.13
19 0.08
20 0.21
21 1.38
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YS Cardno Integrated Water Management Plan
“ Noosa Marketplace : 2-20 HOFMANN DRIVE
Table 3-4 Peak Flows (m*/s)
CatchmentID Peak Flow (m°/s)
1 2.19
2 0.74
3 0.58
4 0.67
5 0.87
6 0.18
7 0.09
8 1.06
9 0.44
10 0.57
11 0.05
12 0.06
13 0.10
14 0.31
15 0.14
16 0.02
17 0.24
18 0.13
19 0.08
20 0.21
a1 1.38
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4 Stormwater Quantity Management
4.1 Background
Using XP-RAFTS, the hydrological model developed above was modified to represent the proposed
development. The model was then used to determine the effects that the proposed development would have
on the stormwater discharge (peak flow rates) coming from the subject site. It is anticipated that, as a result of
the development, peak flow rates will increase. As such, recommendations will be made to ensure peak flows
from the site are equal to or less than those for existing conditions. Detention storage on site will be achieved
through a proposed detention tank system.
4.2 Model Setup
4.2.1 Catchment Parameters
Catchment parameters for the existing and developed local catchment hydrology are shown in Table 4-1. The
existing scenario is as per the hydrological model described above. The changes made for the developed
scenario involved updating the percentage impervious values to represent the proposed development. These
changes are shown in the table below.
Local Catchment Parameters
Catchment Parameters Existing vs Developed
Percentage Percentage
Catchment ID Area (ha) Impervious Existing Impervious Vectored Slope (%)
(%) Developed (%)
1 2.31 95 95 2.96
2 0.77 95 95 5.10
3 0.60 95 95 5.20
4 0.69 95 95 3.36
5 1.17 50 95 3.39
6 0.34 0 75 1.81
7 0.18 0 75 1.22
8 1.15 95 95 1.34
9 0.46 95 95 1.56
10 0.88 50 50 1.41
11 0.09 50 50 0.31
12 0.06 95 95 0.84
13 0.14 5 95 1.86
14 0.53 5 95 2.07
15 0.54 0 75 0.78
16 0.16 5 20 0.09
17 0.45 0 95 2.48
18 0.17 35 35 3.58
19 0.14 0 100 1.52
20 0.42 5 60 1.28
21 1.53 95 95 0.92
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4.2.2 RAFTS Parameters
Catchment information was input to the RAFTS model and analysed using the same critical duration events
that were found in the existing conditions hydrological model. The same lag time of 1 minute was used in the
developed case scenario between the upstream and downstream boundaries of the site catchment.
As the runoff from the external catchments was assumed to be conveyed by the drainage easement on the
eastern side of the site, only the peak runoff from the site itself was considered for the assessment of non-
worsening compared to existing conditions. As expected, the proposed development results in an increase in
peak runoff from the site, with a peak flow of 3.3 m3/s discharging from the site for the 1% AEP event without
any mitigation measures. This is an increase of approximately 1.5 m3/s when compared to the existing
scenario.
4.2.3 Stormwater Detention
Increases in impervious area within the proposed development have resulted in an increase in local catchment
stormwater discharges. A rainwater detention tank is therefore proposed to maintain peak stormwater
discharges to values equal to or less than existing conditions. The design characteristics for the proposed tank
are shown in 0. These values can be altered subject to detailed design to ensure satisfactory performance.
Proposed Detention Storage Tank Characteristics
Table 4-2
Attribute Value
Discharge Pipe Diameter 1 by 750 mm dia
Minimum Volume 1500 m3
Three additional rainwater tanks are proposed for the development as part of the stormwater quality treatment
train. These tanks are 50kL, 25kL and 2kL respectively in volume and are discussed in the following section
of this report. These tanks have been excluded from this modelling as they are assumed to be full at the
commencement of the rainfall event. In addition, they would have little impact upon runoff during larger AEP
events.
4.3 Model Results
The proposed storage system was incorporated in the XP-RAFTS model which was run for the same events
as discussed previously. The peak discharges from the site for pre-development conditions and for post-
development conditions, with the rainwater storage included are shown in Table 4-3.
Table 4-3 Peak XP-RAFTS Discharge
Peak Flow Rate
Event Pre-Development Peak Discharge (m3/s) Post-Developed (Mitigated) Peak Discharge (m3/s)
(AEP) (Site Only) (Site Only)
1% 1.84 1.25
2% 1.48 1.14
5% 1.31 0.93
10% 0.97 0.88
20% 0.80 0.76
39% 0.68 0.66
As shown above, the proposed tank results in a decrease in peak discharges from the site for all AEP events
modelled in the mitigated developed scenario. Table 4-4 shows the storage volume for each modelled event.
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Table 4-4 Rainwater Tank Storage Volume
AEP Event Volume (m3)
1% 1413
2% 1278
5% 1056
10% 1012
20% 912
39% 840
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5 Stormwater Quality Management
The incorporation of Water Sensitive Urban Design (WSUD) features and the development of a Stormwater
Quality Management Plan will ensure that the quality of the stormwater discharging from the site does not
negatively influence receiving environments. The site of the proposed development drains south towards Eenie
Creek.
Noosa Plan Table 7-1 outlines the specific outcomes, acceptable solutions and probable solutions for the
Noosa Plan Water Sensitive Design Code (WSDC) (Noosa Shire Local Government, 2018). This table
recommends the adoption of the Water Quality Objectives outlined in the State Planning Policy 2017 (SPP)
(Department of Infrastructure, Local Government and Planning, 2017) for Queensland as the target objectives.
5.1 Stormwater Quality Objectives
5.1.1 Operational Phase
The stormwater quality design objectives applicable to the site, as outlined in Table B of the State Planning
Policy (SPP) (Department of Infrastructure, Local Government and Planning, 2017) are:
> Total Suspended Solids (TSS) 80% removal of mean annual load from unmitigated development.
> Total Phosphorous (TP) 60% removal of mean annual load from unmitigated development.
> Total Nitrogen (TN) 45% removal of mean annual load from unmitigated development.
> Gross Pollutants > 5mm 90% removal of mean annual load from unmitigated development.
5.1.2 Construction Stage
The construction phase stormwater quality design objectives applicable to the site are outlined in Table A of
the DILGP State Planning Policy (Department of Infrastructure, Local Government and Planning, 2017).
The release values for stormwater captured in a sediment basin are not to exceed the following limits:
> Total Suspended Solids (TSS): 50 mg/L
> pH: 6.5 – 8.0
Appropriate erosion and sediment control measures will be required to be designed, constructed and operated
in accordance with the SPP 2017 guidelines during the construction phase of the development.
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5.2 Proposed Stormwater Quality Treatment
5.2.1 Summary
The proposed stormwater quality treatment for the site consists of Ocean Guards (OG) on all inlets, two
Jellyfish (JF) treatment systems and three rainwater tanks. The rainwater tanks are shown in Figure 5-1. It can
be noted that the tank locations are indicative and are intended only to show the roof areas to be drained to
the tanks. The actual tank locations will be determined during the detailed design.
The specifications of the Ocean Guard and Jellyfish components are in Appendix C.
The characteristics of the rainwater tanks are outlined in 0.
Figure 5-1 MUSIC Model Tank Locations
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Table 5-1 Rainwater Tanks MUSIC Details
Parameter Tank 1 Tank 2 Tank 3
Volume below overflow pipe (kL) 50 25 2.0
Depth above overflow (m) 0.2 0.2 0.2
Surface Area (sq m) 10 5 5
Initial Volume (kL) 10 10 1
Overflow pipe Diameter (mm) 50 50 50
Max Drawdown Height (m) 2 2 0.4
Annual Demand (kL/yr) 3910 1500 40
Distribution PET - Rain PET - Rain PET - Rain
5.2.2 MUSIC Model
A MUSIC (Ver. 6.3) model was set up to determine the efficiency of the stormwater quality treatment train
proposed for the development. The meteorological data adopted for the site was from the Cooroy Composite
weather station as recommended in the MUSIC Modelling Guidelines – Version 1.0 2010 (Water By Design,
2010), for the 11 year period from 01/01/1973 through to 31/12/1983.
The MUSIC source node characteristics were based on the values for commercial developments, as outlined
in the MUSIC Modelling Guidelines (Water By Design, 2010). The adopted source node characteristics are
summarised in Table 5-2 and Table 5-3 . The MUSIC model layout is shown in Figure 5-2 with catchments
shown in Figure 5-3.
Rainfall Runoff Parameters for Commercial Source Nodes
Parameter Value
Rainfall threshold (mm) 1
Soil storage capacity (mm) 18
Initial storage (% capacity) 10
Field capacity (mm) 80
Infiltration capacity coefficient a 243
Infiltration capacity exponent b 0.6
Initial depth (mm) 50
Daily recharge rate (%) 0
Daily baseflow rate (%) 31
Daily deep seepage rate (%) 0
Pollutant Export Parameters for Commercial Source Nodes
Parameter Surface Type TSS mg/L TP mg/L TN mg/L
Roof 0 0 0
Baseflow
Roads 0.78 -0.6 0.32
Roof 1.30 -0.89 0.37
Stormflow
Roads 2.43 -0.30 0.37
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Figure 5-2 MUSIC Model Layout
The development area was divided into two catchments based on preliminary drainage design. These
catchments were then subdivided into their surface types of roofs and roads. The properties of these
catchments are outlined in Table 5-4, with the respective catchments depicted in Figure 5-3.
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Catchment Areas and Proposed Stormwater Treatment
Area (ha) % Impervious MUSIC Node Proposed Treatment
Catchment 1
Roof 0.91 100 Commercial OG, JF
Road 0.81 90 Commercial OG, JF
Catchment 2
Roof 0.35 100 Commercial OG, JF
Road 0.80 90 Commercial OG, JF
Figure 5-3 MUSIC Model Catchments
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5.2.3 MUSIC Model Results
The results from the MUSIC modelling are presented in Table 5-5. As demonstrated by this table, the water
quality objectives have been satisfied for all pollutants.
MUSIC Model Results
Mean Annual Load (kg/yr)
Parameter % Removal Target (%)
Sources Residual
Total Suspended Solids 9820 852 91.3 80
Total Phosphorus 19.2 7.46 61.2 60
Total Nitrogen 134 63.4 52.7 45
Gross Pollutants 969 7.26 99.3 90
5.3 Construction Phase Water Quality Management
The construction phase of the development requires erosion and sediment control measures to be put in place
to ensure that there is not a significant increase in the pollutant loads discharging from the site. During the
construction phase an erosion and sediment control plan will be developed ensuring that the construction
stage stormwater quality objectives are met. When appropriate, implemented erosion and sediment controls
will be removed, generally as a minimum when 80% site cover has been achieved.
Further erosion and sediment control measures will be implemented in accordance with Council requirements
and in consideration of the Best practice guidelines for the control of stormwater pollution from building sites
(Healthy Waterways, 2002).
5.4 Maintenance
Maintenance of the stormwater quality devices is to be carried out by Body Corporate. During the construction
phase, erosion and sediment control devices will be maintained by the developer.
The maintenance requirements of any proprietary products installed are to be carried out in accordance with
manufacturer’s guidelines.
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6 Hydraulic Analysis
6.1 Introduction
The site is not affected by regional or tidal flooding. The level of Mean High Water Spring Tide (MHWS) in the
nearby Noosa River at Tewantin is RL 0.61 mAHD (Maritime Safety Queensland, 2015). Due to the site being
at a level of approximately RL 9.0 mAHD, only local flows from the surrounding sub-catchments were
considered for this hydraulic investigation.
6.2 Model Setup
To determine the effects of the proposed development, a TUFLOW model was developed. The inputs into the
model are outlined below;
> Hydrological (flow) information;
> Topography (LiDAR);
> Key drainage infrastructure (1D);
> Land uses;
> Key drainage infrastructure; and
> Model boundary conditions.
Flow information for the TUFLOW model was obtained from the hydrological modelling described earlier in this
report.
LIDAR topographical data was obtained from the Department of Natural Resources, Mines and Energy
(DERM), and was used as the key input to represent the existing scenario. This LIDAR data was then modified
in the TUFLOW model using ‘2d-z shapes’ to represent the changes as a result of the development.
Drainage infrastructure details were sourced from Noosa Council’s Enterprise Mapping System. Upgraded
drainage infrastructure was sized and input into the developed scenario hydraulic model.
The boundary conditions for the model consisted of ‘local’ inflows from each of the surrounding sub-
catchments, as described above, as well as a standing tail water level of RL 4.1 mAHD. This water level was
set to ensure that the environmental reserve downstream of the proposed development did not cause unsteady
flow conditions at the point of discharge. A sensitivity analysis of the standing tail water level was conducted
by setting the water level to RL 5.1 mAHD. This analysis found that by raising the standing tail water level, the
maximum flood levels on the site do not increase. This shows that the flooding behaviour on the site is not
sensitive to tail water conditions and as a result the assumed tail water conditions can be deemed adequate.
6.3 Modelled Events
The 39, 20, 10, 5, 2 and 1% AEP events were modelled to assess potential negative impacts on surrounding
properties as a result of the proposed development. An initial existing conditions scenario (E01) was run to
establish the current flood levels. A number of developed scenarios were run to determine the optimum
developed scenario. Scenario D05 was used to simulate the changes resulting from the proposed
development. All events were run with the tail water level set to RL4.1 mAHD, as noted above.
6.4 Results
Results from the hydraulic modelling are presented in the following sections. The flood levels were reviewed
for both the existing and developed scenarios. Results at a number of key locations have been tabulated.
These locations were mainly on the boundary of the subject site and on roadways as shown in Figure 6-1.
V190428 | 15 May 2019 | Commercial in Confidence 20
Section 23
Integrated Water Management Plan
Noosa Marketplace : 2-20 HOFMANN DRIVE
Figure 6-1 Locations of Interest
6.4.2 Pre- Development Scenario
Initial modelling of the existing scenario (pre-development) shows that, in all AEP events modelled, Hofmann
Drive, as well as Eenie Creek Road, experience inundation from flood waters. In the 2% AEP event, Hofmann
Drive is inundated to a depth of 200 mm and up to 300 mm in the 1% AEP event. Similarly, at P3 (refer to
Figure 6-1) along Eenie Creek Road is inundated to a depth of 250 mm in the 2% and 1% AEP events. This
section of the road is a flow path and conveys runoff from an external catchment to the north of the road. The
road is not part of the floodplain. Despite this location being inundated by floodwaters, the maximum 1% AEP
water surface level at the northern boundary is approximately 1.8 metres below the Eenie Creek Road
pavement level. It is important to recognise that these conditions exist as part of the pre-development scenario.
At Point 1, located within the existing vegetation covenant area, flood depths of up to 1 metre occur in the
1% AEP event. Within the environmental reserve at the legal point of discharge, a depth of approximately
800 mm occurs in the 1% AEP event.
Table 6-1 and Figure 6-1 show the modelled existing conditions flood levels on the site, while the figures in
Appendix B show the corresponding flood extents.
V190428 | 15 May 2019 | Commercial in Confidence 21
Section 24
Integrated Water Management Plan
Noosa Marketplace : 2-20 HOFMANN DRIVE
Table 6-1 Existing Flood Level (mAHD)
Existing Flood Level (mAHD)
Location 39% AEP 20% AEP 10% AEP 5% AEP 2% AEP 1% AEP
P1 8.95 8.96 8.99 9.03 9.08 9.10
P2 8.38 8.38 8.39 8.41 8.43 8.44
P3 9.85 9.85 9.85 9.86 9.87 9.87
P4 8.35 8.35 8.35 8.37 8.39 8.39
P5 N/A N/A N/A N/A N/A N/A
P6 6.80 6.84 6.85 6.86 6.88 6.89
P7 4.53 4.57 4.59 4.60 4.64 4.68
P8 4.46 4.50 4.51 4.52 4.55 4.57
P9 6.64 6.67 6.67 6.68 6.69 6.71
P10 8.79 8.80 8.80 8.82 8.84 8.85
*N/A meaning that the point of interest is out of the flood waters or located on a development building
6.4.3 Post- Development Scenario
For the current modelling, the development footprint has been set at a nominal level of RL 10.0 mAHD to form
a complete blockage of the flowpath. A service road is proposed to be located around the northern edge of
the development area. The level of this road will be set in detailed design phases of this project, along with
further refinement of the design.
For the post development scenario, an upgrade to the existing 1200 mm x 300 mm RCBC underneath Hofmann
Drive is required due to the increased flows along the eastern boundary of the site. It is proposed to upgrade
this culvert to a 2400 mm x 600 mm RCBC. Within the developed scenario, the existing bank of 4 x 2400 mm
x 800 mm RCBCs at the discharge point was tentatively modelled with an additional barrel. This was done to
ensure that peak flows leaving the site would discharge into the environmental reserve effectively. The
requirement for the additional barrel will be confirmed by more detailed modelling to be undertaken for the final
design.
A 750 mm RCP is proposed to connect to the existing 750 mm RCP entering the site off Commerce Court.
This pipe conveys flows around the development footprint and discharges upstream of the 2400 mm x 600 mm
RCBC under the access road connecting to the roundabout on Hofmann Road.
The peak 1% AEP flood level at the north-west corner of the site (P1) is approximately RL 9.3 mAHD, dropping
to 8.8 mAHD at (P4). The flow path around the north-eastern corner of the development area has a crest at
8.5 mAHD at the north eastern corner of the site and thereby acts as the hydraulic control for flood waters.
The floodplain to the north of the development detains floodwaters and drains via a field inlet connected to the
750 mm RCP through the site via a 450 mm RCP. This drainage feature allows the area to the north to drain
after a flood event. The modelled post-development flood levels are shown in Table 6-2.
Table 6-2 Developed Flood Level (mAHD)
Developed Flood Level (mAHD)
Location 39% AEP 20% AEP 10% AEP 5% AEP 2% AEP 1% AEP
P1 8.81 8.96 9.07 9.14 9.27 9.33
P2 8.48 8.60 8.63 8.68 8.76 8.8
P3 9.85 9.85 9.85 9.86 9.87 9.87
P4 8.48 8.60 8.63 8.68 8.76 8.80
P5 N/A N/A N/A N/A N/A N/A
P6 6.79 6.80 6.82 6.84 6.86 6.87
P7 4.50 4.53 4.53 4.55 4.56 4.56
P8 4.44 4.46 4.46 4.47 4.48 4.49
P9 6.64 6.65 6.66 6.67 6.69 6.69
P10 N/A N/A N/A N/A N/A N/A
*N/A meaning that the point of interest is out of the flood waters or located on a development building
V190428 | 15 May 2019 | Commercial in Confidence 22
Section 25
Integrated Water Management Plan
Noosa Marketplace : 2-20 HOFMANN DRIVE
6.4.4 Impacts of Development
The impacts to peak flood levels at the reporting points are summarised in Table 6.3. As outlined above, the
proposed development forms a partial blockage of the flow path and hence increases the peak flood levels
North of the development area within the Eenie Creek Road reserve. The flood level increases do not extend
beyond the site boundary to the west of the site.
To the north of the site, increases in flood level in the order of 600 mm extend beyond the site boundary.
However, these increases occur only within the road reserve in a bush land area that is inaccessible to the
public. Water levels remain approximately 800 mm below the level of the road pavement in the 1% AEP event.
In the existing case, flood depths of up to 1 metre already exist at this location with the existing topography
acting as a detention basin. Therefore, the proposed development further enhances this natural function with
no actionable nuisance.
Due to the enhancement of the natural detention basin by the development, reductions in peak flood levels
during the 1% AEP event are indicated along a significant section of Hofmann Drive, as shown in Figure B13
App B. Flood impact mapping for all events modelled is shown in Appendix B with all results indicating a
reduction in peak flood levels along Hofmann Drive.
Table 6-3 Flooding Impacts (m)
Flooding Impacts (m)
Location 39% AEP 20% AEP 10% AEP 5% AEP 2% AEP 1% AEP
P1 -0.14 -0.01 0.08 0.10 0.18 0.23
P2 0.11 0.23 0.24 0.27 0.33 0.36
P3 0.00 0.00 0.00 0.00 0.00 0.00
P4 0.14 0.25 0.28 0.32 0.37 0.41
P5 N/A N/A N/A N/A N/A N/A
P6 0.00 -0.04 -0.03 -0.02 -0.02 -0.02
P7 -0.03 -0.04 -0.06 -0.06 -0.08 -0.13
P8 -0.03 -0.04 -0.05 -0.05 -0.07 -0.09
P9 0.00 -0.02 -0.01 -0.01 -0.01 -0.02
P10 N/A N/A N/A N/A N/A N/A
*N/A meaning that the point of interest is out of the flood waters or located on a development building
V190428 | 15 May 2019 | Commercial in Confidence 23
Section 26
Integrated Water Management Plan
Noosa Marketplace : 2-20 HOFMANN DRIVE
7 Conclusions
Hydraulic modelling has demonstrated that the proposed development will have minimal impacts on the flood
levels within surrounding areas.
The majority of the flood level increases resulting from the proposed development are contained within the
development area with the exception of the Eenie Creek Road reserve.
Due to the development increasing storage in a natural flood storage area, reductions in flood depths along a
200 metre section of Hofmann Drive from the site access to Rene Street are anticipated.
RAFTS and MUSIC modelling has demonstrated that the proposed development can satisfy stormwater
quantity and quality requirements as per the SPP 2017, through the use of proprietary devices. On-site
stormwater detention is required to ensure that peak discharges from the site are not worsened. A detention
tank with a minimum volume of 1500 m3 is proposed.
Further detailed modelling of the stormwater quantity, quality requirements and flooding may be necessary
during the Operational Works stage once detailed design is completed.
V190428 | 15 May 2019 | Commercial in Confidence 24
Section 27
Integrated Water Management Plan
Noosa Marketplace : 2-20 HOFMANN DRIVE
Noosa Marketplace : 2-20 HOFMANN
DRIVE
APPENDIX
DEVELOPMENT LAYOUT
V190428 | 15 May 2019 | Commercial in Confidence 25
Section 28
noosa marketplace
Hofmann Drive, Noosaville QLD 4556 EE
NIE
C RE
EK
RO
AD
Development Snapshot
ADDRESSES (LOT & PLAN): LOT.1 - SP222982: 2-20 HOFMANN
DRIVE, LOT.4 - SP2465848: 2-18 HOFMANN DRIVE, NOOSA QLD BUILDING 03
SITE AREA: 35, 762m² LOT 1
SP222982
SITE COVER:
(PROPOSED): - 13, 560m²
PLOT RATIO:
(PROPOSED): - 0.37
LOT 4
SP246584
IVE
BUILDING HEIGHT:
(BUILDING 1): 7, 200m
DR
T
S STREE
(BUILDING 2): 4, 800m
HOFMANN
(BUILDING 3): 13, 845m
(BUILDING 4): 15, 000m
SANDER
AREAS:
BLDG
BUILDING 1 - 04
NLA: 3, 010m²
GFA: 3, 020m²
EXISTING LARGE
BUILDING 2 - FORMAT RETAIL
NLA: 270m² LEO ALL BLDG
EY ROAD
GFA: 275m² 02
BUILDING 3 -
NLA: 7, 550m²
GFA: 7, 960m²
BUILDING 4 -
NLA: 1, 710m²
GFA: 1, 950m²
TOTAL NLA: 12, 540m²
TOTAL GFA: 13, 205m²
CARPARKS PROVIDED: 356
BIKE RACKS: 22
BUILDING
01
DRAWING LIST
EET
A-DA-0000 TITLE SHEET 1 14.05.19
TION STR
A-DA-0001 SITE CONTEXT - EXISTING 1 14.05.19
A-DA-0002 SITE CONTEXT - PROPOSED 1 14.05.19
PRODUC
A-DA-0010 OVERALL SITE PLAN 3 14.05.19 NOOSA CIVIC
A-DA-0011 EASEMENT PLAN 1 14.05.19 CARPARK
A-DA-0100 OVERALL GROUND FLOOR PLAN 1 14.05.19
A-DA-1100 MARKETPLACE PRECINCT GROUND FLOOR PLAN 1 14.05.19
A-DA-1101 MIXED-USE PRECINCT GROUND FLOOR PLAN 1 14.05.19
HOFMA
A-DA-1200 MARKETPLACE PRECINCT SECTIONS 1 14.05.19
A-DA-1201 MARKETPLACE PRECINCT BUILDING SECTIONS 1 14.05.19
NN
A-DA-1203 MIXED-USE PRECINCT BUILDING SECTIONS 1 14.05.19
DRIVE
A-DA-1205 MIXED-USE PRECINCT BUILDING SECTIONS 1 14.05.19 NOOSA CIVIC SHOPPING
CENTRE
A-DA-1206 MIXED-USE PRECINCT BUILDING SECTIONS 1 14.05.19
A-DA-1300 MARKETPLACE PRECINCT BUILDING ELEVATIONS 1 14.05.19
A-DA-1301 MARKETPLACE PRECINCT BUILDING ELEVATIONS 1 14.05.19
A-DA-1303 MIXED-USE PRECINCT BUILDING ELEVATIONS 1 14.05.19
A-DA-1304 MIXED-USE PRECINCT BUILDING ELEVATIONS 1 14.05.19
A-DA-7000 PERSPECTIVE 1 14.05.19
A-DA-7001 PERSPECTIVE 1 14.05.19
A-DA-7002 PERSPECTIVE 1 14.05.19
A-DA-7003 PERSPECTIVE 1 14.05.19
Rev. Date Description Iss. Appr. Do not scale this drawing. Verify all dimensions on site before commencing Project Status Drawing Title
NOOSA MARKETPLACE
any work. Copyright © 2019 Buchan. This drawing remains the property of
1 14.05.19 FINAL ISSUE AJ PS
The Buchan Group Australia Pty Ltd. Reproduction in whole or in part without
prior consent is forbidden. Date Plotted
14/05/2019 10:54:07 AM
File
LOT.1 - SP222982: 2-20 HOFMANN DRIVE, LOT.4 - SP2465848: Date Issued
14.05.19
TITLE SHEET
2-18 HOFMANN DRIVE, NOOSA QLD Scale
As indicated
Project Number @A1 Drawing Number Revision Brisbane Studio
0 10 20 40 60M
+ 61 7 3859 9222 / buchangroup.com.au
716159 A-DA-0000 1
Section 29
Existing Site Photos
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The text continues on section 31.