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WORKING FOR YOUR PROJECTS SUCCESS STORM WATER MANAGEMENT PLAN 79-83 Eumundi Noosa Road & 26 Headland Drive, Noosaville CLIENT: Capital Prudential MULTI TOWNHOUSE/UNIT DEVELOPMENT
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Full text of sections 2 to 29 (of 74)
Section 2
Document Status
Document Type Author Checked by Date Issued Revision
Report Tom Harrington Sean Richardson 19 July 2023
Report Tom Harrington Sean Richardson 11 August 2023 A
Report Tom Harrington Sean Richardson 29 Sept 2023 B
Project Details
Project Name 79-83 Eumundi Noosa Road & 26 Headland Dr,
Noosaville
Client Capital Prudential
Authors Tom Harrington
Checked by Sean Richardson
SCG Consulting Engineer reference 33132(SWMP).RevB
Section 3
Table of Contents
1.0 INTRODUCTION ................................................................................................................................... 3
2.0 EXISTING SITE DESCRIPTION ......................................................................................................... 4
3.0 PROPOSED DEVELOPMENT ............................................................................................................. 5
4.0 EXISTING DRAINAGE.......................................................................................................................... 5
4.1 Existing Drainage Infrastructure ............................................................................................................. 5
4.2 Existing Drainage Patterns ........................................................................................................................ 6
4.3 Lawful Point of Discharge ........................................................................................................................... 7
5.0 STORMWATER QUALITY .................................................................................................................. 8
5.1 State Planning Policy and Water by Design Assessment ................................................................. 8
5.2 Construction Phase ....................................................................................................................................... 9
5.2.1 Silt and Sediment Erosion ...................................................................................................................................... 9
5.3 Completed Development.......................................................................................................................... 10
5.3.1 Water Quality Objectives ..................................................................................................................................... 10
5.3.2 Sources of Contaminants ..................................................................................................................................... 10
5.3.3 Proposed Treatment Measures ......................................................................................................................... 12
5.3.4 Pollutant Modelling ................................................................................................................................................ 12
6.0 STORMWATER QUANTITY ............................................................................................................ 15
6.1 Drains Analysis ............................................................................................................................................ 15
6.1.1 Existing Catchments .............................................................................................................................................. 16
6.1.2 Existing Site ............................................................................................................................................................... 16
6.1.3 Proposed Site ............................................................................................................................................................ 17
6.1.4 Peak Flow Comparison ......................................................................................................................................... 18
6.1.5 Peak Flow Mitigation (OSD) ............................................................................................................................... 18
6.2 Proposed Drainage .................................................................................................................................... 22
6.3 Downstream Infrastructure Consideration ...................................................................................... 22
7.0 FLOODING ........................................................................................................................................... 22
8.0 CONCULSION ...................................................................................................................................... 23
APPENDIX A – Detailed Site Survey ........................................................................................................ 24
SCG Consulting Engineers Page 1 SCG Ref: 33132(SWMP).RevB
Section 4
APPENDIX B – Proposed Development Plans ..................................................................................... 25 APPENDIX C – Noosa Council Drainage Infrastructure Plan .......................................................... 26 APPENDIX D – Concept Stormwater Management Plan .................................................................. 27 SCG Consulting Engineers Page 2 SCG Ref: 33132(SWMP).RevB
Section 5
1.0 INTRODUCTION
SCG Consulting Engineers have been commissioned by Capital Prudential to complete a Stormwater
Management Plan (SWMP) for a residential development at Lots 75-77 RP 71151 & Lot 3 SP 208257,
79-83 Eumundi Noosa Road & 26 Headland Drive, Noosaville.
The proposed development involves the construction of 38 townhouse/apartment dwellings. The
objective of this (SWMP) is to demonstrate that the following measures will be incorporated into the
design and construction of the development:
• Maintain stormwater quality – Protect receiving waters (during and post construction)
• Manage stormwater peak flow rates of runoff and existing flow path characteristics
• Protect against flooding
• Adopt Water Sensitive Urban Design (WSUD) principles throughout
• Implement Stormwater Harvesting and re-use for landscaping.
This report should be read in conjunction with our detailed site stormwater management plans
(Appendix D) Drawing No. SCG 33132 – SW1.1, SW1.2 & SW1.3 & SW1.4
The proposed development has been assessed against the following guidelines and planning documents:
• Queensland Urban Drainage Manual 2017 (QUDM)
• Water Sensitive Urban Design (WSUD) – Technical Design, Guidelines for South East
Queensland
• Noosa Plan 2020
• AS/NZS 3500.3:2018 – Plumbing and Drainage Part 3 – Stormwater Drainage
• State Planning Policy 2017
• Sunshine Coast Stormwater Management Guidelines VI - 2020.
SCG Consulting Engineers Page 3 SCG Ref: 33132(SWMP).RevB
Section 6
2.0 EXISTING SITE DESCRIPTION
The site is described as Lots 75-77 RP 71151 & Lot 3 SP 208257 and is located within Noosa Shire
Council and is approximately 6,318m2 in area. Access to the existing sites is off Eumundi Noosa Road,
which bounds the western property boundaries, refer to Figure 2.1, for a locality plan and Appendix A
for a detailed site survey. Each Lot currently contains a detached residential dwelling located to the
front portions of the site. 71 & 81 Eumundi Road also contains a shed located beyond each dwelling.
The rear of each site is covered by short grass and scattered trees.
The site generally falls from the front boundary on Eumundi Noosa Road (Approx. RL 13.5-14.5 AHD)
in an eastern direction down towards the rear boundary (Approx. RL 7.75-10.5 AHD). Surface grades
for the majority of the site are in the order of 5-7%. A Council stormwater inter-allotment drainage
system runs adjacent to the eastern (rear) boundary of the site which contains a series of pipes, varying
in size and are contained in the downstream properties within an existing easement.
Council infrastructure also runs along Headland Drive to the south of the site.
Figure 2.1 – Locality Plan
SCG Consulting Engineers Page 4 SCG Ref: 33132(SWMP).RevB
Section 7
3.0 PROPOSED DEVELOPMENT
A residential development is proposed for the allotment comprising of 38 townhouse/apartment
dwellings.
The proposed development plans are detailed in Blackwood Architecture and Design drawings 202327,
Drawings DA1.01 thru to DA1.19 (refer Appendix B.) The development includes the following
features: -
• 10 visitor and 40 private carparking spaces
• Bin storage and washdown areas
• Dual property driveway access to Eumundi Noosa Road and Headland Drive
• Bio retention/detention basin for stormwater quality and quantity
• Rainwater harvesting tanks for stormwater re-use
• Landscaping areas across the site
• Padmount transformer.
4.0 EXISTING DRAINAGE
4.1 Existing Drainage Infrastructure
Data obtained from Noosa Council’s Interactive Mapping, accompanied with a detailed site survey
prepared by Bennet & Bennet confirms the following drainage infrastructure: -
• A series of gully pits located on the eastern boundaries (rear) connected to an underground
pipe network within a drainage easement of the downstream properties
• A series of underground pipes varying in size (225mm to 375mm) located within the
drainage easement of the downstream properties
• An underground drainage network in Headland Drive with pipe sizes varying in size (600-
675mm) located in the road reserve
• Existing kerb adaptor connections to Headland Drive.
Refer to figure 4.1 for the existing stormwater drainage patterns, Appendix A for the detailed site survey
and Appendix C for Noosa Council Drainage Infrastructure.
SCG Consulting Engineers Page 5 SCG Ref: 33132(SWMP).RevB
Section 8
Figure 4.1 – Existing Drainage Paths & Infrastructure
4.2 Existing Drainage Patterns
Data obtained from Noosa Council’s Interactive Mapping, accompanied with a detailed site survey
prepared by Bennet & Bennet confirms the following drainage patterns: -
Roofwater runoff
1. A visual site inspection of the Eumundi Noosa Rd street frontage found that there was no kerb
outlets for Lots 75-77. Therefore it is assumed that roofwater runoff from the existing buildings
is discharged to the ground or to the existing underground drainage infrastructure at the rear of
the site.
2. The roof water from the existing building located at 26 Headland Drive is discharged to the kerb
& channel on Headland Drive via kerb adaptors.
Surface Runoff
1. Surface runoff from the existing surface on Lots 75,76 & part of 77 RP71151 generally falls in
an easterly direction towards the rear boundary and into the existing inter-allotment drainage
system.
2. Surface runoff from Lot 6 SP208257 and a portion of Lot 77 RP71151 generally falls in a south-
easterly direction towards the Headland Drive Road Reserve.
SCG Consulting Engineers Page 6 SCG Ref: 33132(SWMP).RevB
Section 9
4.3 Lawful Point of Discharge
The lawful point of discharge is described in Section 3.9.1 of QUDM 2017. The ‘Lawful Point of
Discharge Test’ may be helpful in assessing whether a lawful point of discharge exists at a particular
location. As defined in QUDM 2017 the criteria for determining the lawful point of discharge are: -
1. Will the proposed development alter the site’s stormwater discharge characteristics in a
manner that may substantially damage a third party property (see section 3.6).
• If not, then no further steps are required to obtain tenure for a lawful point of
discharge (assuming any previous circumstances and changes were lawful).
• If there is a reasonable risk of such damage, then consider issue (2) or (3).
2. Is the location of the discharge from the development site under the lawful control of the
local government or other statutory authority from whom permission to discharge has
been received? This will include a park, watercourse, drainage or road reserve,
stormwater registered drainage easement, or land held by local government (including
freehold land).
Note: The regulatory authority (in its capacity as land holder) is likely to require
information about the potential impact of the site’s stormwater discharge characteristics
on third party properties (particularly those downstream of the proposed discharge point)
before it will consent to the discharge entering its land.
• If so, then no further steps are required to obtain tenure for a lawful point of
discharge.
• If not, then consider issue (3). A land owner or regulator may require that the
developer obtain an authority to discharge as described in (3) in order for the
stormwater to ultimately flow to a location described in (2).
3. An authority to discharge over affected properties will be necessary. In descending order
of certainty, an authority may be in the form of:
• Dedication of a drainage reserve or park
• A registered easement for stormwater discharge/works
• Written discharge approval.
Note: Some authorities may not accept a written approval from a current land owner
because a subsequent purchaser will not be bound by the previous owner’s letter or
contract (refer to Section 3.10).
SCG Consulting Engineers Page 7 SCG Ref: 33132(SWMP).RevB
Section 10
If the proposed development maintains pre-development flow conditions, the lawful points of discharge
for the subject site is into the existing inter-allotment stormwater drainage infrastructure within Lots
102, 107, and 108 SP 106085 and Starboard Avenue, east of the site, and the Headland Drive stormwater
infrastructure. The proposed lawful point of discharge is considered to be compliant with the criteria
outlined in QUDM 2017 see below: -
1. The proposed development stormwater discharge will not alter the existing site’s
stormwater discharge characteristics.
2. The location of the proposed discharge point is under the lawful control of the local
government.
3. Authority to discharge over affected properties will not be required as the proposed
development will discharge as per existing drainage conditions.
5.0 STORMWATER QUALITY
In the absence of adequate controls, urban development can increase both stormwater runoff volumes
and peak discharge rates. In addition, this urban development has the potential for increased creek
erosion and the stressing of in-stream aquatic ecosystems. The use of stormwater detention or retention
systems aims at reducing these threats by limiting property flooding to acceptable levels and also
filtering stormwater runoff through a vegetated soils media layer, thus reducing the threats caused by
urban development.
The following factors have been identified as potential contributors which can adversely affect
stormwater quality draining from the site:-
• Silt and sediment erosion
• Gross Pollutants
• Hydrocarbon runoff
• Nutrient runoff
5.1 State Planning Policy and Water by Design Assessment
The proposed development has been assessed against the State Planning Policy 2017 and the Water By
Design (Stormwater Quality Deemed to Comply Solutions – 2010).
The proposed residential development involves a land area greater than the trigger value of 2500m2 for
stormwater quality measures as required in the State Planning Policy 2017 and the Water By Design -
SCG Consulting Engineers Page 8 SCG Ref: 33132(SWMP).RevB
Section 11
Stormwater Quality Deemed to Comply Solutions - 2010. Therefore, stormwater quality treatment is
warranted for the proposed development.
5.2 Construction Phase
Sediment generated during the construction phase shall be controlled in accordance with a site specific
Erosion and Sediment Control (ESC) Plan and kept on site throughout construction.
5.2.1 Silt and Sediment Erosion
A potential for sediment mobilisation/transportation exists during and beyond the construction of the
proposed development. This can elevate turbidity levels of stormwater runoff.
A RUSLE assessment of the site confirms proposed development is a Low Risk for soil loss (< 150
Tonnes).
Potential Causes
• Stormwater scour and erosion of excavated or stripped surfaces and stockpiled soils.
• Wind borne transportation of sediments.
• Disturbance/breakup of soil profile via vehicular traffic followed by stormwater scour
and erosion.
• Transportation of sediments from site via excavation vehicles.
Mitigating Measures
• Construction of silt fences around the development site located to cut off all runoff.
• Construction of a sediment basin throughout construction at a low point of the
development site.
• Provide 80-100mm crushed rock (no fines) hardstand under all vehicle paths expected
during construction. Generally, this would be provided from the existing crossover and
extended to a distance within the site that would accommodate the maximum delivery
vehicle length expected.
• Provide rumble grates at exit points from the site for passing earthmoving vehicles.
• Where possible maintain existing landscaping/grasses downslope from construction areas
to act as buffer/silt trap.
• Install temporary downpipes from completed roof structures and ensure runoff passes
through silt fences.
• Minimise concentrating surface flows.
• Place silt barriers around council stormwater pits that the site drains to.
• Cover soil stockpiles with hessian or similar.
SCG Consulting Engineers Page 9 SCG Ref: 33132(SWMP).RevB
Section 12
5.3 Completed Development
We are proposing to use a combination of active and passive stormwater treatment measures. Active
measures will include bio-retention basins, water storage tanks for re-use and passive measures via gross
pollutant inserts into stormwater pits across the site.
For the proposed development we have proposed incorporate Water Sensitive Urban Design (WSUD)
principles stormwater harvesting has been proposed for stormwater re-use for communal landscaping.
The proposed water re-use tank has been sized in accordance with the Sunshine Coast Council Flooding
and Stormwater Management Guidelines adopting 1kl per 25m2 of communal landscaping area water
tank for stormwater re-use have been incorporated into the proposed development.
5.3.1 Water Quality Objectives
Water quality objectives for South East Queensland are outlined in the State Planning Policy 2017 and
are displayed in Table 5.1. These reductions are achieved by adopting best practice techniques in
accordance with the abovementioned guidelines.
Table 5.1: Minimum Mean Annual Load Reductions
POLLUTANT / ISSUE MINIMAL MEAN ANNUAL LOAD REDUCTIONS
Total Suspended Solids (TSS) 80%
Total Phosphorous (TP) 60%
Total Nitrogen (TN) 45%
Gross Pollutants (GP) 90%
5.3.2 Sources of Contaminants
Gross Pollutants
Gross pollutants include litter, grit and heavier sediments which can be mobilised from within or from
neighbouring sites.
Potential Causes
• Unsecured refuse areas.
• Un-landscaped areas prone to stormwater scour.
• Insufficient drainage for surface runoff from within the site.
• Wind Bourne transportation.
SCG Consulting Engineers Page 10 SCG Ref: 33132(SWMP).RevB
Section 13
Mitigating Measures
• Well established refuse areas with ample storage bins. Fenced off where deemed
necessary.
• Provision of ample litter bins across the commercial footprints of the site. Particularly in
any outdoor dining or areas of congregation.
• Promotion of stormwater surface runoff through landscaped areas or similar sediment
buffering strips/traps.
• Provide stormwater pits outside paved areas that receive runoff from areas prone to gross
pollutants with surrounding buffering measures, such as stone pitching.
• Provide gross pollutant inserts into stormwater pits within paved areas that receive runoff
from areas prone to gross pollutants.
Hydrocarbon Runoff:
Hydrocarbons can be mobilised and transported in stormwater runoff from the site. This can contaminate
stormwater runoff compromising Water Quality Objectives.
Potential Causes
• Leaks from parked vehicles within the completed development.
• Washing of vehicles within the completed development.
Mitigating Measures
• Fall driveways and parking areas towards adjacent landscaped strips, vegetated swales
and the bioretention bed.
Nutrient Runoff:
Nutrients such as Nitrogen and Phosphorus can be mobilised and transported in Stormwater runoff from
the site. This can compromise Water Quality Objectives.
Potential Causes
• Runoff from hard surfaces within the site.
• Detergents used in car washing and similar activities.
• Fertilisers used in propagation of landscaped areas.
• Embodied nutrients contained in silt (topsoil) runoff.
• Embodied nutrients contained in runoff.
SCG Consulting Engineers Page 11 SCG Ref: 33132(SWMP).RevB
Section 14
Mitigating Measures
• Fall vehicles pavement areas towards landscaping areas and the bioretention bed.
• Implement management plan for landscaping propagation. Use stable organically bound
fertilizers cultivated immediately prior to turf placement. Mulch over areas of exposed
topsoil.
• Construction of silt fences during construction and maintained beyond completion of
landscaping.
• Drain stormwater runoff through the Bio Basin.
• Capture roof runoff and store for re-use.
5.3.3 Proposed Treatment Measures
Implementing the water quality objectives for the site as mentioned above and to ensure that on-site
stormwater management facilities can be economically maintained, it was deemed the most appropriate
method for treatment is the inclusion of small grass swales and bio-retention basins. Roof and surface
runoff will be collected via an internal drainage network and directed to the on-site bio retention basins
prior to the lawful point of discharge.
5.3.4 Pollutant Modelling
The impact of the stormwater quality management strategy of runoff discharged from the site has been
assessed using the Pollutant Export Model, Model for Urban Stormwater Improvement
Conceptualisation (MUSIC).
For our model the proposed treatment train has been modelled: -
1. Roof water from buildings containing units 301-304, 401-404 will be collected by a 7kL
rainwater re-use tank with an overflow to an onsite Bio retention basin, namely Bio-
Retention Bed A (BR-A) located in the north-eastern corner of the site. The rainwater
tank will be re-used for area landscaping irrigation only, to all common areas.
2. Roof water from buildings containing units 701-704 and the front portion of 601-602 will
be collected by a 7kL rainwater re-use tank with overflow to the onsite Bio retention
basin, namely Bio-Retention Bed B (BR-B) located in the South-eastern corner of the
site. The rainwater tank will be re-used for landscaping irrigation only, to all common
areas.
3. Surface runoff from hardstand and landscaping areas will be collected by numerous catch
pits and pipes. The internal drainage network will then discharge into the onsite bio
retention basins for treatment.
SCG Consulting Engineers Page 12 SCG Ref: 33132(SWMP).RevB
Section 15
The Music Model was set up in accordance with the Water By Design Music Modelling Guidelines for
South East Queensland. Design parameters are listed below:
BR-A
• Surface Area = 85m2
• Filter Media Area = 50m2
• Filter Depth = 0.4m
• Extended Detention = 0.2m
• Hydraulic Conductivity = 180mm/ Hr
• TN content of Filter Media = 500mg/ kg
• Orthophosphate content of Filter Media = 5mg/ kg
BR-B
• Surface Area = 30m2
• Filter Media Area = 25m2
• Filter Depth = 0.4m
• Extended Detention = 0.2m
• Hydraulic Conductivity = 180mm/ Hr
• TN content of Filter Media = 500mg/ kg
• Orthophosphate content of Filter Media = 5mg/ kg
Figure 5.1 displays a print screen of the MUSIC Model Schematic for the proposed development and
Figure 5.2 displays the annual pollutant loads that will be discharged from the proposed development.
SCG Consulting Engineers Page 13 SCG Ref: 33132(SWMP).RevB
Section 16
Figure 5.1 – Music Model Schematic
Figure 5.2 – Music Modelling Results
SCG Consulting Engineers Page 14 SCG Ref: 33132(SWMP).RevB
Section 17
The modelling results show the pollutant reduction objectives are met for all contaminants listed in Table
5.1. Details of the proposed bio-retention basin are detailed in the Stormwater Management Plan drawing
no: SCG 33132 - SW1.1 thru to SW1.4 (Appendix D.)
6.0 STORMWATER QUANTITY
Noosa Shire Council’s Planning Scheme – Noosa Plan 2020, requires post development peak flows
leaving the development site will not exceed the pre-development peak flow rates for the required design
storms.
A Stormwater Quantity Analysis has been undertaken of the existing and developed site conditions in
accordance with the following guidelines.
− QUDM 2017
− Noosa Planning Scheme 2020
− Australian Rainfall and Runoff (ARR 2019)
The following section of this report discusses the proposed developments impact on peak stormwater
discharge from the site and the proposed mitigation measures to ensure a non-worsening effect is
achieved to downstream properties.
6.1 Drains Analysis
To calculate the peak discharges for the site under existing (pre-development) and proposed (post-
development) conditions. Hydraulic modelling has been undertaken for the site using the software
package PC DRAINS. Modelling has established existing and proposed stormwater drainage
characteristics.
Rainfall patterns accompanied with Initial Loss (IL) and Continuing Loss (CL) was sourced from the
Australian Rainfall and Runoff 2019 (ARR 2019) data hub for Noosaville.
Initial Losses (IL) and Continuing Loss (CL) were approximated based on the storm losses from the
ARR Data Hub, Table 6.1 below states the adopted values: -
Table 6.1 - Adopted (IL) and (CL) Values
AREAS (IL) (CL)
(mm) (mm/hr)
Impervious 1 0
Pervious 27 2.6
SCG Consulting Engineers Page 15 SCG Ref: 33132(SWMP).RevB
Section 18
Design ARR 2019 storms for Noosaville have been added into DRAINS accompanied with IFD rainfall
depths from the Bureau of Meteorology (BOM) website
6.1.1 Existing Catchments
The existing site has been divided into two sub catchments to compare the existing site discharge
locations. These are labelled as A & B and are detailed on SCG drawing No. 33132 - SW1.4(Appendix
D)
Times of concentration (Tc) were calculated as defined in QUDM 2017 using a combination of standard
inlet time & overland sheet flow time. Table 6.2 displays the Adopted time of Concentrations.
Table 6.2 – Tc Values
STATE Catchment A (Tc) (mins) Catchment B (Tc) (mins)
Pre Development 15 13
Post Development 6 6
6.1.2 Existing Site
The existing site consists of 4 Lots containing a residential dwelling on each, detached sheds &
landscaped ground areas. The existing surface on Lots 75,76 & part of 77 RP71151 generally falls in an
eastern direction towards the rear boundary & the existing inter-allotment drainage system. Lot 6
SP208257 and a portion of Lot 77 RP71151 generally falls in a south-eastern direction towards the
Headland Drive Road Reserve. Roof runoff from existing dwellings appears to be a mixture of
discharging directly to ground level & via kerb adaptors to Headland Drive.
The total impervious areas have been estimated using the detailed site survey and was found to be
approximately 1521m2 which equates to approximately 22% of Impervious Area for (Cat A) & 41% of
Impervious Area for (Cat B) respectively.
The existing site catchments are as follows.
Catchment A
- Area – 0.4833 Ha
- Tc – 15 mins
- Fraction Impervious (Fi) – 0.21
SCG Consulting Engineers Page 16 SCG Ref: 33132(SWMP).RevB
Section 19
Catchment B
- Area – 0.1485 Ha
- Tc – 13 mins
- Fraction Impervious (Fi) – 0.41
Peak flow rates for the median design storm for the existing site are given in Table 6.3
Table 6.3 – Existing Site Peak Flow Rates (L/s)
Storm Event Q1 Q2 Q5 Q10 Q20 Q50 Q100
(1EY) (0.5EY) (0.2EY) (10%AEP) (5%AEP) (2%AEP) (1%AEP)
Cat A 79 119 160 186 218 259 287
Existing PFR
Cat B 27 39 52 59 69 83 91
Existing PFR
(PFR – Peak Flow Rate)
6.1.3 Proposed Site
The development consists of the construction of mixed residential townhouse/ unit development along
with a shared access driveway and ground level landscaping/ courtyards & a community pool area. The
total pervious area for the site was calculated to be approximately 1368m2.
The Developed site catchments are as follows.
Catchment A
- Area – 0.4363 Ha
- Tc – 6 mins
- Fraction Impervious (Fi) – 0.77
Catchment B
- Area – 0.1955 Ha
- Tc – 6 mins
- Fraction Impervious (Fi) – 0.83
-
SCG Consulting Engineers Page 17 SCG Ref: 33132(SWMP).RevB
Section 20
Peak flow rates for the median design storms for the developed site are given in Table 6.4
Table 6.4 – Developed Site Peak Flow Rates (L/s)
Storm Event Q1 Q2 Q5 Q10 Q20 Q50 Q100
(1EY) (0.5EY) (0.2EY) (10%AEP) (5%AEP) (2%AEP) (1%AEP)
Cat A 124 156 193 233 270 321 359
Developed PFR
Cat B 60 75 93 111 129 149 166
Developed PFR
(PFR – Peak Flow Rate)
6.1.4 Peak Flow Comparison
Table 6.5 indicates the increased peak flow rates for the developed cases.
Table 6.5 – Comparison of Existing Vs Developed Peak Flows (L/s)
AEP Storm Q1 Q2 Q5 Q10 Q20 Q50 Q100
(1EY) (0.5EY) (0.2EY) (10%AEP) (5%AEP) (2%AEP) (1%AEP)
Cat A 45 37 33 47 52 62 72
Increase PFR
Cat B 33 36 41 52 60 66 75
Increase PFR
(PFR – Peak Flow Rate )
As shown in Table 6.5 Stormwater peak discharge will increase as a result of the proposed development
due to the increase in impervious area. Therefore, it is proposed to utilise two On Site Detention (OSD)
systems to mitigate the peak stormwater discharge rates from the proposed development prior to
discharging to the lawful point of discharge as discussed in section 4.2.
6.1.5 Peak Flow Mitigation (OSD)
To mitigate the peak flow increase from the developed site, it is proposed to include a mixture of
inground detention tanks located under the proposed driveway and inground open bio retention basins
that include a volume dedicated to on site detention of stormwater runoff.
SCG Consulting Engineers Page 18 SCG Ref: 33132(SWMP).RevB
Section 21
Catchment A will be detained through the use of a in-ground open detention basin, Bio-Retention Bed
(BR-A) located in the northeast corner of the site to detain all flows from Catchment A
For catchment B it is proposed to utilize a series of underground detention tanks to capture all roof
water from building 5, 6 & 7. Tank overflows & all groundwater runoff will then drain to an in-ground
open bio retention/ detention basin, (BR-B) located at the southern corner of the site on Headland Dr.
We propose for the detention systems to cater for flows up to the Q100 storm event and a limit the peak
flow rates of pre-development levels for all storms up to the Q100 storm event.
For proposed Catchment A, the proposed BR-A will have the following properties: -
• Base Area = 98m2
• Internal Depth = 1.0m
• Low Flow Orifice = 275mm diameter
• High Flow Orifice = 250mm diameter
• Overflow Wier Elevation From Base = 1.0m
• Required Volume = 100m3
• Provided Volume = 110m3
For proposed Catchment B, the proposed inground detention tanks, located under the driveway will have
the following properties:
Detention Tank for Building 5 roof water:
• Base Area = 26m2
• Internal Depth = 1.1m
• Low Flow Orifice = 55mm diameter
• High Flow Orifice = 75mm diameter
• Required Volume = 23m3
• Provided Volume = 28m3
Detention Tank for Building 6 & 7 roof water:
• Base Area = 24m2
• Internal Depth = 1.9m
• Low Flow Orifice = 95mm diameter
• High Flow Orifice = 100mm diameter
• Required Volume = 45m3
• Provided Volume = 48m3
SCG Consulting Engineers Page 19 SCG Ref: 33132(SWMP).RevB
Section 22
the proposed BR-A will have the following properties: -
• Base Area = 32m2
• Internal Depth = 0.35m
• Low Flow Orifice = 250mm diameter
• Overflow Wier Elevation From Base = 0.35m
• Required Volume = 11.7m3
• Provided Volume = 12.8m3
Figure 6.1 illustrates the DRAINS Model layout for the site.
Figure 6.1 – Drains Model Layout
SCG Consulting Engineers Page 20 SCG Ref: 33132(SWMP).RevB
Section 23
Peak flow rates determined for each 3 cases are outlined in Table 6.6.
Table 6.6 – Comparison of Peak Flows (L/s)
AEP Storm Q1 Q2 Q5 Q10 Q20 Q50 Q100
(1EY) (0.5EY) (0.2EY) (10%AEP) (5%AEP) (2%AEP) (1%AEP)
Existing 79 119 160 186 218 259 287
PFR A
Existing 27 39 52 59 69 83 91
PFR B
Mitigated 80 102 147 185 209 230 287
PFR A (+1) (-17) (-13) (-1) (-9) (-19) (0)
Mitigated 30 39 47 52 59 72 87
PFR B (+3) (0) (-5) (-7) (-10) (-11) (-4)
(PFR – Peak Flow Rate)
As shown in Table 6.6 the proposed OSD facilities have demonstrated the proposed mitigated peak
discharge flow rates will not exceed the total pre-development flows for all design storms above 2 year
ARI, up to and including the 1% AEP Design Storm. We note that there is a marginal increase in the
mitigated developed peak flow rate for the Q1 (1EY) storm event of 3L/s. However, as the increase in
stormwater discharge is considered very minor and below the design ARI for the minor stormwater
drainage system, the effect on the downstream network is considered to be insignificant and negligible.
Further, all stormwater discharging site in the developed case will discharge to the bio-retention basins
which both have an extended detention depth of 200mm prior to the allocated detention zone. This
equates to approximately 6kL of additional detention storage which has not been considered in the
calculation of peak stormwater discharge rates for the developed site. The peak stormwater discharge
values are therefore considered to be conservative and are expected to be less than the existing site. We
consider the developed site will not have a non-worsening effect on surrounding properties and
downstream network, with regard to stormwater discharge.
The proposed stormwater detention system is therefore considered to be adequate for the development.
SCG Consulting Engineers Page 21 SCG Ref: 33132(SWMP).RevB
Section 24
6.2 Proposed Drainage
The proposed site drainage is detailed in drawings SCG 33132 - SW1.1 - SW1.4 (Appendix D) and is
discussed below.
As defined in the Noosa Plan 2020 stormwater drainage must be designed in accordance with QUDM
2017, therefore the following design storms were adopted: -
1. Minor Drainage System - 10% AEP ARI (Q10 Storm)
2. Major Drainage System - 1% AEP ARI (Q100 Storm)
6.3 Downstream Infrastructure Consideration
The mitigated peak flow rates for both discharge points will be less than existing peak flow rates
discharging to the existing drainage infrastructure located in Lot 108 on SP106085, No.6 Starboard
Avenue, & the existing stormwater drainage infrastructure located within Headland Drive, as discussed
in Section 4.1. Therefore, it is considered acceptable as existing stormwater peak flows maintain existing
conditions.
7.0 FLOODING
Information provided from Noosa Council’s Flood Hazard Overlay Map confirms the site is unaffected
by flooding.
SCG Consulting Engineers Page 22 SCG Ref: 33132(SWMP).RevB
Section 25
8.0 CONCULSION
The stormwater management report demonstrates under the detailed plans the proposed residential
development at , Lots 75-77 RP 71151 & Lot 3 SP 208257, 79-83 Eumundi Noosa Rd & 26 Headland
Dr, Noosaville meets the quantity and quality stormwater requirements as described in this report.
Sediment generated during the construction phase is to be dealt with in accordance with a Silt and
Sediment Control plan and is to be kept on-site throughout construction.
The proposed development triggers the State Planning Policy 2017 stormwater quality treatment
objectives. An on-site bio-retention basin, grassed swales and a water storage tank for re-use for
landscaping irrigation has been incorporated into the proposed development to meet the prescribed water
quality objectives, prior to discharging to the lawful point of discharge.
On-site detention has been provided to maintain existing peak flow rates and to ensure a non-worsening
to flooding of downstream properties. On-site detention is proposed to be contained within a mixture of
underground tanks and the onsite bio retention basins and the designed to contain all flows up to a Q100
storm event.
The subject site is not affected by localised flooding.
Digitally
signed by S
Richardson
SEAN RICHARDSON – RPEQ 5835
For and on behalf of
SCG CONSULTING ENGINEERS
SCG Consulting Engineers Page 23 SCG Ref: 33132(SWMP).RevB
Section 26
APPENDIX A -— Detailed Site Survey SCG Consulting Engineers Page 24 SCG Ref: 33132(SWMP).RevB
Section 27
LEGEND:
Road Terrain
Kerb Back Driveway
Kerb Invert Footpath
Edge of Bitumen Slab Edge
Edge of Gravel Retaining Wall Base
Road Crown Retaining Wall Top
Traffic Park Meter Change of Grade
EMT.V EMT.Y Traffic Light
Traffic Pit
Top of Bank
Toe of Bank
2 3
48 SP298783 49 SP106085 Traffic Sign
Traffic Post Box
Waterline
Garden Edge
Structures Creek Toe of Bank
SP298783 SP298783 108 Building Line
Roof Ridgeline
Creek Top of Bank
Creek Invert
Fence Line Creek Waterline
// // // SP106085 Gate Tree
// Hand Rail Tree Canopy
8
//
// Cattle Grid Control Point/PSM
Bollard Drainage
10
Sewer Drainage line
75 S(*) Sewer Line
D(*)
Open Drain
14
//
//
12
14 RP71151 EMT.AA Valve
Inspection Opening
Manhole
Field Inlet
Manhole Downpipe
SP106085
9
Electrical Communications
E(*) Electricity Line C(*) Communication Line
EOH Overhead Line TOH Overhead Line
Pits/Manholes Pits/Manholes
// //
107 Pole Pillar
//
//
11
//
//
d // // // //
Street Light Gas
SP106085
oa
Light In-Ground
13
G(*) Gas Line
14
Water Valve
12
R
Water Line Marker
14
W(*)
Meter General
10
Valve Pothole
sa
76 H Fire Hydrant
//
Tap Subsurface Utility - QL
13
//
oo
RP71151 Fuel
Sprinkler * (A)
* (B)
* QL-A (H±50mm,V±50mm)
* QL-B (H±300mm,V±500mm)
iN
P(*) Fuel Line * (C) * QL-C (H±300mm,2D)
14
13 // // Fitting * (D) * QL-D (Exist Record)
//
14
//
// //
nd
// //
11
12
EMT.BB
//
mu
13 NOTES:
SP106085
77
14
Eu
1. Drawn to scale on an A3 sheet.
//
RP71151 2. Contour Interval... 0.25m
3. All levels are in metres on the Australian Height
Datum referred to (PSM53205) - RL 13.595 AHD
//
11
14
// situated in EUMUNDI RD.
102
13
// 4. All Boundaries are vide title and subject to
14
// 11
SP106085 confirmation by survey.
//
EMT A 5. The Location of Underground services are in
//
SP208257
3 accordance with AS5488:2019, the Australian
Standard for classification of Subsurface Utility
SP2082
//
1 57 Information (SUI). The exact nature and location
SP208257 2 of these services should be confirmed prior to
construction.
SP208257
//
6. Area vide title - 3/SP208257 : 639m²
7 4
// // 10 //
9
7. Area vide title - 77/RP71151 : 1831m²
8. Area vide title - 76/RP71151 : 1927m²
8 9. Area vide title - 75/RP71151 : 1925m²
5
11 10
12
13 10. Field Survey Completed on 18/05/2023
14
EMT B Level datum: AHD Derived ((PSM53205))
SP208257
Headland Drive
Horiz datum: MGA Derived GNSS (CORS)
Coord Origin: Arbitrary ((NE Cor Site))
GDA System: GDA2020 Coordinate System: MGA
Meridian: + 8°58'38" RP71151
Title:
VERIFICATION PLOT
Lots 75-77 on RP71151, and Lot 3 on
SP208257 - 79-83 Eumundi Noosa Road,
and 26 Headland Drive, Noosaville
Client: Capital Prudential Pty Ltd
Locality: Noosaville
Local Gov: Noosa Shire Council
Surveyed By: WA Approved: CJ
Scale 1:750 Date Created: 26/05/23 Scale: 1:750
File Ref: 230833
Plan No: 230833_001_VER Rev: A
0m 10 20 30 40 50 60 70 80 90
Page 1 of 8 A3
Section 28
)
C (D)
(D
Scale 1:250
C
(D)
W (D)
0m 5 10 15 20 25
C
)
(D
)
W
(D
)
(D
48
C
(D)
W
SP298783
LEGEND:
C
Road Terrain
(D)
Kerb Back Driveway
)
Kerb Invert Footpath
(D
83
Edge of Bitumen Slab Edge
SP2S T(B. V
D
Edge of Gravel Retaining Wall Base
)
987)
nel
W
(D
Road Crown Retaining Wall Top
)
(D
chan
14.66 Traffic Park Meter Change of Grade
ad
EM
C
Traffic Light Top of Bank
f ro
W
(D)
Traffic Pit Toe of Bank
and
Traffic Sign Waterline
eo
Traffic Post Box Garden Edge
Site Benchmark
C
Kerb
in
Structures Creek Toe of Bank
trel
14.24 RL 14.51m // // Building Line Creek Top of Bank
Creek Invert
Cen
14.15 13.56 // Roof Ridgeline
(D)
d
14.88 Timber fence
//
)
// 12.59 Fence Line Creek Waterline
(D
// 13.08
// 12.27
oa
13.93 Gate Tree
14.42
en
Tree Canopy
)
Hand Rail
D
T73
W
13.12
(D
13.58
)
tum
Cattle Grid
R
Control Point/PSM
B)
(D
Co Bollard
14.00 ncr Drainage
S (
C
ete
//
i
of b
14.55 13.09
sa
13.54
W
driv 12.70 Sewer D(*) Drainage line
(D)
Concrete driveway ew 12.27 S(*) Sewer Line Open Drain
13.95 ay
ge
Valve Manhole
oo
14 T74 12.86
Ed
14. 13.26 Field Inlet
C
.30 30 Inspection Opening
13.91 Manhole Downpipe
brick house with subfloor space
14
iN
18.53
13.84 Electrical Communications
14 Co 12.57
)
Communication Line
Single storey Timber and
.32
12
Electricity Line C(*)
ncr
(D)
E(*)
(D
14.21
ete Overhead Line
//
EOH Overhead Line TOH
nd
14.50 foo 12.14
14.12 Pits/Manholes Pits/Manholes
)
tpa
W
en
(D
D
)
th Pole Pillar
(D
mu
itum
14.06 14.3 Street Light Gas
4
B)
Ridge line
C
14.45 14.65 14 15.05 Light In-Ground G(*) Gas Line
W
14.52 Concrete
of b
S (
0"
Water Valve
(D)
T72 12.78
Eu
4'3
14.59 12.54 W(*) Water Line Marker
Floor Level 15.06
ge
9
Meter General
1°0
.99
T71
C
//
13.98
Ed
13.82 Valve Pothole
14.23
21
23
13.70 12.60 Fire Hydrant
75 12.33 H
Tap Subsurface Utility - QL
)
Sprinkler * QL-A (H±50mm,V±50mm)
RP71151
(D
* (A)
(D)
Fuel * (B) * QL-B (H±300mm,V±500mm)
k
)
Fuel Line * (C) * QL-C (H±300mm,2D)
W
P(*)
an
)
(D
12.65
(D
18.61 Fitting * (D) * QL-D (Exist Record)
ba D
nk
15.40
fb
13.93 13.76 13.62
14.10 Ridge line 18.53 12.60
po
14.10
C
//
W
12.40
B)
of
Open face
To
14.41
(D)
14.31
m
14.38
S (
garage
tto
13.65
13.48 13.14 12.83 Concrete NOTES:
Bo
C
C (D) 13.00 12.30
14.18
(D) 13.98 Concrete driveway 13.40
13.32 12.98 1. Drawn to scale on an A3 sheet.
C 12.76
)
88°08'10" 2. Contour Interval... 0.25m
(D
//
13.92 //
//
T46 13.61 12.95 //
(D)
Chainwire fence // 13.19
// // // // 3. All levels are in metres on the Australian Height
W)
95.930
// // //
Garden
(C
T45 T66 Datum referred to (PSM53205) - RL 13.595 AHD
)
T55 T56 T57 T58 T59 T60 T67
(D
14.10 // T51 T52 T53 T54 T63 T64 T65
T61 T62 situated in EUMUNDI RD.
D
Garden 12.03
13
T50
C
4. All Boundaries are vide title and subject to
W
Site Benchmark T49
13.85 confirmation by survey.
B)
RL 14.18m 14.20 13.56
14
13.90 12.63
C (D) 5. The Location of Underground services are in
S (
12
13.89 Concrete dri 13.56 13.30 accordance with AS5488:2019, the Australian
//
14.36 14.23 veway
13.83 11.96 Standard for classification of Subsurface Utility
14.19 13.71
14
//
13.88 13.30 Information (SUI). The exact nature and location
)
13.97
(D
14.11 14.35 13.55 of these services should be confirmed prior to
12.58
(D)
W)
Section 29
)
13.98 13.03 construction.
)
(C
(D
12.29
(D
12.99
13.91 6. Area vide title - 3/SP208257 : 639m²
C
C
D
7. Area vide title - 77/RP71151 : 1831m²
W
13.02 Concrete
//
14.07
13.91 8. Area vide title - 76/RP71151 : 1927m²
12.17
13.29 12.98 12.67 9. Area vide title - 75/RP71151 : 1925m²
20.01
13.21 12.98
B)
14.08 Verandah
Steps
RP71151
10. Field Survey Completed on 18/05/2023
"
T43
'30
S (
15.90
Ridge line
12.94
9
04
.97
timber house
Verandah Garden
13
Two storey
) 31°
76
)
16.61
15.88
en
23
13.82
(D
//
Level datum: AHD Derived ((PSM53205))
um
13.89 13.75
W)
Ridge line
)
(D)
Horiz datum: MGA Derived GNSS (CORS)
(C
(D
14.33
bit
d
(D
Garden underneath steps
Steps
roa
12.42 Coord Origin: Arbitrary ((NE Cor Site))
of
Shed
19.93
C
C
11.95 GDA System: GDA2020 Coordinate System: MGA
W
ge
of
D
14.17 Meridian: + 8°58'38" RP71151
Ed
ne
13.74
16.58
13.66
eli
14.09 T44 13.81
Title:
ntr
//
B)
12.22
Ce
VERIFICATION PLOT
14
13.67 13.60
S (
14.32 13.78 Sewer MH:
//
14.07 14.00 IL: 10.849
EOH 13 T68
)
Lots 75-77 on RP71151, and Lot 3 on
(D
Type: 150 RCP
11.64
EOHT41
(D l
11.90
e
nn
W)
T40 12.32
)
)
88°08'10" // SP208257 - 79-83 Eumundi Noosa Road,
(C
(D
EOH Garden T42 //
ha
EO 13.97 12.64 //
14
Chainwire fence // //
Site Benchmark H 13.15 // 95.930
dc
// //
// // // 11.76 and 26 Headland Drive, Noosaville
C
C
13.49
W
//
//
12.72 12.03
//
//
an
//
RL 14.20m //
12
14.14
15.30
rb
13.68 12.75 Sewer MH:
Client: Capital Prudential Pty Ltd
Ke
//
12.81
Timber fence
13.03 IL: 10.863
14.29 13.66
Ridge line
Type: 150 RCP Locality: Noosaville
T48 T35
EO T47 T38
12.42 12.29
12.07
H 12.06 Noosa Shire Council
EO ewayl
13.93 13.52 Shed Local Gov:
dri rave
12.99
D ain
C otpath
13.11 T36
(C) 12.13 r Surveyed By: WA Approved: CJ
G
T37
13 ld
v
fo )
ncr W (C)
)
)
a
//
Concrete Drive
ete (D
15.36
)
13.99
ur
H
12.65
(D
(D
11.76
(D
way 12.38 t Date Created: 26/05/23 Scale: 1:250
13.50
12.98
Na
W
C
230833
//
File Ref:
S
77 12.21
16.93
13.05
13.93 Concrete 12.12 Plan No: 230833_001_VER Rev: A
RP71151
Co
14
Slab 12.17
Page 2 of 8 A3
l
11.80
ne
an
ch
nd
The text continues on section 30.