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WORKING FOR YOUR PROJECTS SUCCESS STORM WATER MANAGEMENT PLAN 89-93 Eumundi Noosa Road, Noosaville CLIENT: Vantage Building Group TOWNHOUSE DEVELOPMENT
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Page 2
Document Status
Document Type Author Checked by Date Issued Revision
Report Tom Harrington Sean Richardson
Project Details
Project Name Stormwater Management Plan
89-93 Eumundi Noosa Road, Noosaville
Client Vantage Building Group
Authors Tom Harrington
Checked by Sean Richardson
SCG Consulting Engineer reference 31131(SWMP)
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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 and Infrastructure .................................................................................................... 5
4.2 Lawful Point of Discharge ........................................................................................................................... 6
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 ..................................................................................................................................... 11
5.3.3 Proposed Treatment Measures ......................................................................................................................... 13
5.3.4 Pollutant Modelling ................................................................................................................................................ 13
6.0 STORMWATER QUANTITY ............................................................................................................ 15
6.1 Rational Method .......................................................................................................................................... 16
6.1.1 Design Storms........................................................................................................................................................... 16
6.1.2 Rainfall Intensity ..................................................................................................................................................... 16
6.1.3 Time of Concentration .......................................................................................................................................... 16
6.1.4 Runoff Coefficient (C10)......................................................................................................................................... 17
6.1.5 Peak Flows ................................................................................................................................................................. 17
6.2 Proposed Drainage .................................................................................................................................... 18
6.2.1 Catchments ................................................................................................................................................................ 18
6.2.2 Peak Flow Mitigation ............................................................................................................................................. 18
6.3 Hydraulic Modelling (PC Drains) .......................................................................................................... 19
6.3.1 Rainfall Data .............................................................................................................................................................. 19
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6.3.2 Initial Loss (IL) and Continuing Loss (CL) .................................................................................................... 19
6.3.3 Configuration ............................................................................................................................................................ 20
6.3.4 Results ......................................................................................................................................................................... 20
6.3.5 Total Post Development Mitigated Discharge............................................................................................. 21
6.4 Downstream Infrastructure Consideration .....................................Error! Bookmark not defined.
7.0 FLOODING ........................................................................................................................................... 22
8.0 CONCULSION ...................................................................................................................................... 23
APPENDIX A – Detailed Site Survey ........................................................................................................ 24
APPENDIX B – Proposed Development Plans ..................................................................................... 25
APPENDIX C – Existing Drainage Features and Infrastructure ..................................................... 26
APPENDIX D – Concept Stormwater Management Plan .................................................................. 27
APPENDIX E – Rational Method Calculations ...................................................................................... 28
APPENDIX F – BOM IFD Data ..................................................................................................................... 29
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1.0 INTRODUCTION
SCG Consulting Engineers have been commissioned by Vantage Building Group complete a Stormwater
Management Plan (SWMP) for a residential development at Lot 1 on RP130594, Lots 80 and 81 on
RP71151, 89-93 Eumundi Road, Noosaville.
The proposed development involves the construction of 22 townhouse 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 31131 -SW1.1.thru to SW1.5).
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.
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2.0 EXISTING SITE DESCRIPTION
The site is described as Lot 1 on RP130594, Lots 80 and 81 on RP71151 and is located within Noosa
Shire Council and is approximately 4150m2 (0.42ha) 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. Lot 1 and Lot 89 currently contains existing residential dwellings
to the front portions of the site. Lot 81 contains a small shed to the front portion of the site. 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 16-17.5 AHD)
in a north-eastern direction down towards the rear boundary (Approx. RL 10-15 AHD). Surface grades
for the majority of the site are in the order of 4-6%. 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.
Figure 2.1 – Locality Plan
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3.0 PROPOSED DEVELOPMENT
A residential development is proposed for the allotment comprising of 22 residential townhouse
dwellings.
The proposed development plans are detailed in Blackwood Architecture and Design drawings 202144,
DA5 thru DA7 RevD (refer Appendix B). The development includes the following features: -
• 8 visitor and 26 private carparking spaces
• Bin storage and washdown areas
• Single property driveway access to Eumundi Noosa Road
• Bio retention/detention basin for stormwater quality and quantity
• Landscaping areas across the site
• Padmount transformer.
4.0 EXISTING DRAINAGE
4.1 Existing Drainage and Infrastructure
Data obtained from Noosa Council’s Interactive Mapping, accompanied with a detailed site survey
prepared by Noosa Cooloola Land Surveys confirms the following drainage infrastructure along the rear
boundary of the site: -
• 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
• Existing kerb adaptor connections to Eumundi Noosa Road.
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Refer to Appendix A for the detailed site survey and Appendix C for the existing drainage features and
infrastructure on Noosa Council Mappin Data.
4.2 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.
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• 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).
If the proposed development maintains pre-development flow conditions, the lawful point of discharge
for the subject site is the existing stormwater drainage infrastructure within Lot 99, 100 and 101 on
SP106085, east of the site and the Eumundi Noosa Road kerb and channel. 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.
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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. For the proposed development we have suggested to incorporate Water Sensitive
Urban Design (WSUD) principles in the landscaping for the proposed development to treat stormwater
before it exists the site. A series of vegetated swales, a bio retention/detention basin bed and a water
tank for stormwater re-use have been incorporated into the proposed 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 -
Stormwater Quality Deemed to Comply Solutions - 2010. Therefore, stormwater quality treatment is
warranted for the proposed development.
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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.
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• 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.
5.3 Completed Development
We are proposing to use a combination of active and passive stormwater treatment measures. Active
measures will include a bio-retention basin and a water storage tank for re-use and passive measures via
gross pollutant inserts into stormwater pits within paved areas that receive runoff from areas prone to
gross pollutants.
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%
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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.
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.
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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.
Mitigating Measures
• Fall vehicles pavement areas towards landscaping areas and the bioretention bed.
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• 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
Following the water quality objectives for the site mentioned above, to ensure that on-site stormwater
management facilities can be economically maintained, it was deemed the most appropriate method for
treatment is the use of a small grass swale and an on-site bio-retention basin. Roof and surface runoff
will be collected by an internal drainage network and directed to the on on-site bio retention basin 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 17-22 and unit 1 will be collected by a 15kL
rainwater re-use tank with overflow to Eumundi Noosa Road kerb and channel. The
rainwater tank will be re-used for landscaping irrigation only, to all common areas.
2. Roof water for the remainder of the proposed development will be collected by the
internal drainage network to discharge into a small grassed swale directed to the bio
retention basin for treatment.
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3. Surface runoff from hardstand and landscaping areas will be collected by various pits and
pipes. The internal drainage network will then discharge into a small grassed swale
directed to the bio retention basin for treatment.
The Music Model was set up in accordance with the Water By Design Music Modelling Guidelines for
South East Queensland.
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.
Figure 5.1 – Music Model Schematic
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Figure 5.2 – Music Modelling Results 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 provided in the Stormwater Management Plan drawing no: SCG 31131- SW1.1 thru SW1.5 (Appendix D). 6.0 STORMWATER QUANTITY Noosa Shire Council’s Planning Scheme – Noosa Plan 2020, require post development peak flows leaving the development site will not exceed the pre-development peak flow rates for the required design storms. Peak flow increases will be minimised by the provision of an On-site Detention (OSD) basin fitted with a low flow orifice plate to detain a portion of the runoff from the site and limit the peak flow rates of pre-development levels. SCG Consulting Engineers Page 15 SCG Ref: 31131(SWMP)
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6.1 Rational Method
To calculate the peak discharges for the site under existing (pre-development) and proposed (post-
development) conditions the rational method has been used in accordance with QUDM 2017.
6.1.1 Design Storms
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 Year ARI (Q10 Storm)
2. Major Drainage System - 100 Year ARI (Q100 Storm)
6.1.2 Rainfall Intensity
Rainfall intensities were obtained from The Australian Bureau of Meteorology. Refer to Appendix F
for the IFD design rainfall intensity.
6.1.3 Time of Concentration
Times of concentration (Tc) were calculated as defined in QUDM 2017. Refer Table 6.1 for Adopted
time of Concentrations and Appendix E for calculations: -
Table 6.1 – Tc Values
STATE CATCHMENT A (Tc) (mins) CATCHMENT B (Tc) (mins)
Pre Development 5 13.00
Post Development 5 5.67
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6.1.4 Runoff Coefficient (C10)
The 10year runoff coefficients (C10) were calculated as defined in QUDM. Refer to Table 6.2 for
Adopted C10 Values: -
Table 6.2: C10 Values
STATE CATCHMENT A (C10) CATCHMENT B (C10)
Pre Development 0.78 0.74
Post Development 0.88 0.88
6.1.5 Peak Flows
Table 6.3 below displays a summary of major and minor discharge rates for pre and post development
conditions using the rational method. Refer to Appendix E for calculations: -
Table 6.3: Pre and Post Development Peak Flow Rates
Condition Q1 Q2 Q5 Q10 Q20 Q50 Q100
(m3/s) (m3/s) (m3/s) (m3/s) (m3/s) (m3/s) (m3/s)
Pre Development 0.010 0.013 0.019 0.024 0.029 0.037 0.042
Catchment A
Post Development 0.028 0.034 0.051 0.063 0.076 0.095 0.105
Catchment A
Pre Development 0.063 0.076 0.114 0.140 0.167 0.210 0.240
Catchment B
Post Development 0.070 0.084 0.128 0.159 0.191 0.241 0.266
Catchment B
Total 0.074 0.089 0.134 0.164 0.195 0.247 0.282
Pre Development
Total 0.098 0.118 0.179 0.222 0.267 0.336 0.370
Post Development
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6.2 Proposed Drainage
The proposed site drainage is detailed in drawings SCG 31131- SW1.1 thru SW1.5 (Appendix D) and
is discussed below.
6.2.1 Catchments
Roof Catchment
1. Runoff from catchment A, consisting of the roof area of buildings containing units 17-22
and unit 1 will flow via downpipes to an internal drainage network where it will be
directed to an underground rainwater tank for re-use. The tank will then overflow to the
Eumundi Noosa Road kerb and channel (lawful point of discharge).
2. Runoff from catchment B, consisting of the remaining roof areas of the site, will flow via
downpipes to an internal drainage network where it will be directed to the on-site bio
retention/detention basin prior to discharging to the existing inter-allotment drainage
network located in Lot 99–101 on SP106085 (lawful point of discharge).
Ground Catchment
Surface runoff from the hardstand and landscaping areas will be directed to a series of entry pits and an
underground pipe network to the on-site bio retention/detention basin. The treated/detained runoff is
then discharged to the existing inter-allotment drainage network located in Lot 99–101 on SP106085
(lawful point of discharge).
6.2.2 Peak Flow Mitigation
As shown in Table 6.3 Stormwater peak discharge will increase as a result of the proposed development.
Therefore, it is proposed to utilise an OSD system to mitigate the peak stormwater discharge rates from
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catchment B of the proposed development prior to discharging to the lawful point of discharge as
discussed in section 4.2.
Catchment A will result in an increase to stormwater runoff rates to existing flow conditions. Refer to
section 6.4 for the downstream infrastructure considerations.
6.3 Hydraulic Modelling (PC Drains)
Hydraulic modelling has been undertaken using the software package PC DRAINS. We have modelled
the site to establish existing and proposed stormwater drainage characterisitics.
6.3.1 Rainfall Data
Rainfall data accompanied with Initial Loss (IL) and Continuing Loss (CL) was sourced from the
Australian Rainfall and Runoff (ARR) data hub and were imported into the model.
6.3.2 Initial Loss (IL) and Continuing Loss (CL)
Initial Losses (IL) and Continuing Loss (CL) were approximated based on the storm losses from the
ARR Data Hub, Table 6.4 below states the adopted values: -
Table 6.4: Adopted (IL) and (CL) Values
AREAS (IL) (CL)
(mm) (mm/hr)
Impervious 0 0
Pervious 27 2.6
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6.3.3 Configuration
To mitigate the peak flow increase from the developed site, it is proposed to include an inground open
bio retention/detention basin for catchment B, located within the north eastern corner of the site. We
propose for the detention basin to cater for flows up to the Q100 storm event and a limited capacity to the
existing stormwater infrastructure located in Lot 101 RP 106085, refer to section 6.4 for further
discussion. The proposed on-site detention will have the following properties: -
• Base Area = 140m2
• Internal Depth = 1.1m
• Low Flow Orifice = 0.18m diameter
• Overflow Pit Elevation from base = 1.1m
• Required Volume = 150m3
• Provided Volume = 180m3
The site was divided into sub-catchments to mirror the Stormwater Management Plan drawing no: SCG
31131- SW1.1 - SW1.5 detention basin was also included for catchment B as discussed above.
6.3.4 Results
The pre development and post development peak median flow rates were compared for the catchments
and are displayed in Table 6.5 below:
Table 6.5 – Comparison of peak Flows
Condition Q1 Q2 Q5 Q10 Q20 Q50 Q100
(m3/s) (m3/s) (m3/s) 3 (m3/s) (m3/s) (m3/s)
(m /s)
Drains Catchment B 0.048 0.065 0.095 0.119 0.141 0.167 0.187
Pre Development
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Drains catchment B 0.038 0.041 0.047 0.053 0.058 0.081 0.104
Post Development
(Mitigated)
The PC DRAINS Hydraulic Modelling has demonstrated the proposed mitigated peak discharge flow
rates will not exceed the total pre development flows for all design storms. Refer Appendix D for the
drains results.
6.3.5 Total Post Development Mitigated Discharge
The post development rational method results displayed in Table 6.3 for catchment A has been added
to the mitigated catchment B results from PC DRAINS displayed in Table 6.5. Table 6.6 summarises
the total post development site discharge.
Table 6.6 – Total Post Development Mitigated Peak Discharge
Catchment Q1 Q2 Q5 Q10 Q20 Q50 Q100
(m3/s) (m3/s) (m3/s) 3 (m3/s) (m3/s) (m3/s)
(m /s)
Rational Method 0.028 0.034 0.051 0.063 0.076 0.095 0.105
Catchment A Post
Development
Drains Catchment B 0.031 0.038 0.044 0.052 0.057 0.061 0.109
Post Development
(Mitigated)
Total Site Discharge 0.059 0.072 0.095 0.115 0.133 0.156 0.217
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6.4 Downstream Infrastructure Consideration To determine if the existing lawful points of discharge for Catchment B is capable to safely convey the post development mitigated flow we have modelled the existing drainage infrastructure as discussed in Section 4.1 using the software PC DRAINS. The modelling has demonstrated that all post development mitigated peak flows up to Q100 can be safely contained within the existing 375m2 diameter stormwater line traversing the rear of Lot 101 on SP106085. The pipe longitudinal sections and calculations have been exported and are shown in Appendix D. Catchment A will result in a increased discharge to the Eumundi Noosa Road kerb and channel, however this has been limited to a Q10 flow rate of 25Lt/s at each kerb adaptor location as per Noosa Council requirements. The net total discharge from the proposed site will remain below pre development flows for all storms from Q1 up to Q100. 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: 31131(SWMP)
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8.0 CONCULSION The stormwater management report demonstrates under the detailed plans the proposed residential development at , Lot 1 RP130594 and Lots 80 and 81 RP71151, 89-93 Eumundi Road, Noosaville meets the quantity and quality stormwater requirements as described in this report. If the proposed development maintains pre-development drainage patterns and flow rates to the lawful points of discharge, are the existing stormwater infrastructure within Lot 101 SP 106085 on the eastern boundary of the site and the Eumundi Noosa Road kerb and channel. 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 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 the bio retention basin and the designed to contain all flows up to a Q100 storm event. The existing stormwater infrastructure is capable of conveying the post development mitigated flow paths for all storms up to a Q100. The subject site is not affected by localized flooding. SCG Consulting Engineers Page 23 SCG Ref: 31131(SWMP)
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APPENDIX A — Detailed Site Survey 0€8ze9 60r0 O9€Z82 6140 oouew Bai ney preg L9S¥ “CTO ‘SPESH BSOON ‘p89l XOg ‘O'd 98rp26E19 NOV ssoAaAing pue 8ulyjnsuo> PIT Aig skaning puey 200/005 esooN 98Z€09 ZLbO > ISLLZd& « . 08 —= Zz 31131(SWMP) SCG Ref: Page 24 SCG Consulting Engineers
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APPENDIX B – Proposed Development Plans SCG Consulting Engineers Page 25 SCG Ref: 31131(SWMP)
Page 28
EXISTING
SHALLOW BUND
EXISTING 450 SQ.
DRAINAGE PIT & 225
DIAMETER PVC PIPE
NOTE: INTERALLOTMENT
DRAINAGE LOCATED IN
REAR PROPERTIES IN
ADMIRAL PLACE.
SUBJECT
GROUND BUILT UP
SITE
APPENDIX C – Existing Drainage Features and Infrastructure
ROOF SHEETING PINNED TO
BOUNDARY FENCE TO PREVENT
STORMWATER FLOWS
SHEET FLOW PATH
Noosa Shire Council does not warrant the accuracy of information in this publication and any person using or relying 24/11/2021
upon such information does so on the basis that Noosa Shire Council shall bear no responsibility or liability
whatsoever for any errors, faults, defects or omissions in the information.
1:750
Page 29
APPENDIX D – Concept Stormwater Management Plan SCG Consulting Engineers Page 27 SCG Ref: 31131(SWMP)
Page 30
Issue:
Unit 1/11 Project Ave,
Noosa Heads
Ph (07) 5455 5604
email:[email protected]
web:www.scg-engineers.com
ABN 40 098 481 899
DEBUILD T/A
Title:
Project
Date: Drawn Design
SCHEMATIC DRAINAGE PROPOSAL ONLY DETAILED DESIGN Rev.
Checked: Drg No.
ISSUED AT OPERATIONAL WORKS APPLICATION
Rev. - 10.06.16
Page 31
APPENDIX E – Rational Method Calculations SCG Consulting Engineers Page 28 SCG Ref: 31131(SWMP)
Page 32
STORMWATER RUNOFF ASSESMENT
Noosa Site
Calculates existing and developed flow rates in accordance with QUDM
2017 for sites located in Noosa
Address 89-93 Eumundi Noosa Rd Site Area 4150 m2
SCG Job No. 31131
Pre Development Post Development
Sub-catchment A Sub-catchment B Sub-catchment A Sub-catchment B
2 2 2
Pervious Area 278 m Pervious Area 3397 m Pervious Area 234 m Pervious Area 575 m2
Impervious area 210 m2 Impervious area 265 m2 Impervious area 936 m2 Impervious area 2305 m2
TOTAL 488 m2 TOTAL 3662 m2 TOTAL 1170 m2 TOTAL 2880 m2
STORM DATA STORM DATA STORM DATA STORM DATA
Time of Concentration 5 min Time of Concentration 13 min Time of Concentration 5 min Time of Concentration 5.67 min
I 10 226 mm/hr I 10 164 mm/hr I 10 226 mm/hr I 10 220 mm/hr
fi 0.43 fi 0.07 fi 0.80 fi 0.80
C 10 0.78 C 10 0.74 C 10 0.88 C 10 0.88
Frequency Frequency Frequency Frequency
ARI (years) Cy Iy ARI (years) Cy Iy ARI (years) Cy Iy ARI (years) Cy Iy
Factor (Fy) Factor (Fy) Factor (Fy) Factor (Fy)
1 0.8 0.624 124 1 0.8 0.592 93 1 0.8 0.704 121 1 0.8 0.704 124
2 0.85 0.663 141 2 0.85 0.629 105 2 0.85 0.748 138 2 0.85 0.748 141
5 0.95 0.741 192 5 0.95 0.703 141 5 0.95 0.836 187 5 0.95 0.836 192
10 1 0.78 226 10 1 0.74 164 10 1 0.88 220 10 1 0.88 226
20 1.05 0.819 259 20 1.05 0.777 186 20 1.05 0.924 252 20 1.05 0.924 259
50 1.15 0.897 301 50 1.15 0.851 214 50 1.15 1 292 50 1.15 1 301
100 1.2 0.936 332 100 1.2 0.888 234 100 1.2 1 322 100 1.2 1 332
Q = C x I x A / 360
Q - Pre-Development A Q - Pre-Development B Q - Post-Development A Q - Post-Development B
ARI Qy (m3/s) Qy (Lt/s) ARI Qy (m3/s) Qy (Lt/s) ARI Qy (m3/s) Qy (Lt/s) ARI Qy (m3/s) Qy (Lt/s)
1 0.010 10.5 1 0.063 63.5 1 0.028 27.7 1 0.070 69.8
2 0.013 12.7 2 0.076 76.1 2 0.034 33.5 2 0.084 84.4
5 0.019 19.3 5 0.114 114 5 0.051 50.8 5 0.128 128
10 0.024 23.9 10 0.140 140 10 0.063 62.9 10 0.159 159
20 0.029 28.8 20 0.167 167 20 0.076 75.7 20 0.191 191
50 0.037 36.6 50 0.210 210 50 0.095 94.9 50 0.241 241
100 0.042 42.1 100 0.240 240 100 0.105 105 100 0.266 266
Page 33
APPENDIX F — BOM IFD Data SCG Consulting Engineers Page 29 SCG Ref: 31131(SWMP)
Page 34
11/23/21, 12:12 PM Rainfall IFD Data System: Water Information: Bureau of Meteorology
Location
Label: Not provided
Latitude: -26.406 [Nearest grid cell: 26.4125 (S)]
Longitude:153.05 [Nearest grid cell: 153.0625 (E)]
IFD Design Rainfall Intensity (mm/h) Issued: 23 November 2021
Rainfall intensity for Durations, Exceedance per Year (EY), and Annual Exceedance Probabilities (AEP).
FAQ for New ARR probability terminology
Annual Exceedance Probability (AEP)
Duration 63.2% 50%# 20%* 10% 5% 2% 1%
1 min 171 194 263 308 350 405 446
2 min 145 165 228 272 314 372 417
3 min 137 155 214 253 292 344 384
4 min 130 148 202 239 274 320 356
5 min 124 141 192 226 259 301 332
10 min 102 115 155 181 205 236 259
15 min 86.3 97.5 131 153 173 199 218
20 min 75.3 85.1 115 134 152 175 192
25 min 67.1 75.9 103 120 136 157 173
30 min 60.8 68.8 93.2 109 124 144 159
45 min 48.1 54.5 74.5 87.8 101 117 130
1 hour 40.4 45.9 63.1 74.8 86.1 101 113
1.5 hour 31.3 35.8 49.8 59.4 68.9 81.6 91.4
2 hour 26.1 29.9 42.1 50.4 58.8 70.0 78.7
3 hour 20.3 23.3 33.2 40.1 47.0 56.3 63.7
4.5 hour 15.8 18.2 26.3 31.9 37.6 45.3 51.4
6 hour 13.2 15.4 22.3 27.2 32.1 38.9 44.2
9 hour 10.3 12.1 17.7 21.7 25.7 31.2 35.6
12 hour 8.69 10.2 15.0 18.4 21.9 26.7 30.5
18 hour 6.78 7.95 11.8 14.6 17.4 21.3 24.4
Note:
# The 50% AEP IFD does not correspond to the 2 year Average Recurrence Interval (ARI) IFD.
Rather it corresponds to the 1.44 ARI.
* The 20% AEP IFD does not correspond to the 5 year Average Recurrence Interval (ARI) IFD.
Rather it corresponds to the 4.48 ARI.
This page was created at 12:12 on Tuesday 23 November 2021 (AEST)
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