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33 Pavilion Street, Pomona PSP Developments Pty Ltd Flood and Stormwater Management Plan 23-0167SMP01-V3 November 2023
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Commercial in Confidence
This document is commercial-in-confidence. The recipient of this document agrees to hold all information presented
within as confidential and agree not to use or disclose or allow to use or disclosure of the said information to
unauthorized parties, directly or indirectly, irrespective of the acceptance or rejection of the presentation or at any time
before, during or after an agreement has been reached, without prior written consent.
This report is prepared by Colliers | Engineering & Design for exclusive use by its client only. No responsibility is accepted
for the use of or reliance upon this report in whole or in part by any third party.
Limitations
The sole purpose of this report and the associated services performed by Colliers | Engineering & Design is to display
information in accordance with the scope of services set out in the contract/quotation between Colliers | Engineering &
Design and its client. The scope of works and services were defined by the requests of the client, by the time and
budgetary constraints imposed by the client, and by the availability of access to site/s and information.
This report is prepared with information supplied by the client and possibly others which is presumed to be accurate and
complete. No responsibility is accepted for information that is withheld, incorrect or that is inaccurate, nor for changes
to the conditions over the passage of time or from latent circumstance or conditions. No warranty or guarantee is made
in relation to the data, findings and conclusions expressed in this report.
This report has been compiled at the level of detail specified in the report and no responsibility is accepted for
interpretations made at more detailed levels than so indicated.
Report Contact:
Name: Lochlan Gillis
Position Senior Water Resources Engineer
Phone: (07) 3532 1300
Document Control
21-0352FSMP02-V3
Version Date Details Prepared Checked Approved Signed RPEQ
1 18/07/2023 Issue BB / LG LG KM 09298
2 06/10/2023 Issue LG KM KM 09298
3 15/11/2023 Issue LG KM KM 09298
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page i
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Executive Summary Colliers Engineering and Design have been engaged by PSP Developments Pty Ltd to prepare a Stormwater Management Plan (SMP) in support of a development application to Noosa Shire Council (NSC) over land located at 33 Pavilion Street, Pomona (Lot 4 RP809059). This development application seeks a development permit for a Reconfiguration a Lot (ROL) to create 8 residential lots. The site has an existing building at Lot 1 and no works are required to create lot 1. The location of the proposed development site has a total land holdings area covering 3.33ha. The site is consistent with a rural residential land use type with some wooded vegetation cover over the site. The site is accessed by Pavilion Street to the east and Majestic Place to the south and is bounded by private allotments to the north, east and south. Cooroora Creek is located in the adjacent property to the west. It can be seen from the results presented that the treatment measures proposed for the development site achieve the performance criteria set by the NSC Planning Scheme (2020) and SPP (July 2017). Annual Load Reductions of Total Suspended Solids (TSS), Total Phosphorus (TP), Total Nitrogen (TN) and Gross Pollutants (GP) between the Mitigated and Unmitigated Scenarios have been achieved through the upgrade of the existing bioretention basin from 80m2 to 130m2. It has been demonstrated that non-worsening of peak flows has been achieved to the discharge point for events up to the 1% AEP event. The results show that there is non-worsening for events up the 1% AEP. The intent of sizing the detention basin is to mitigate flows up to the 10% AEP storm event to ensure non-worsening of discharges into the downstream flow path. In larger events, flows from the site will start to sheet flow across the rear of the site to Cooroora Creek. As the discharge point for the site becomes inundated from Cooroora Creek flooding in the major storm event, it is considered non-worsening has been achieved. The catchment size of Cooroora Creek reporting past the site is approximately 1,400 ha and it is considered that no quantifiable change to downstream flooding conditions would result. The development Is located above ”he r’Iional 1% (2100) AEP flood extent with 500mm freeboard recommended to future dwellings on the new allotments. 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona
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Table of Contents
Executive Summary ................................................................................ 2
1. Introduction ..................................................................................... 6
1.1 Site Characteristics ................................................................................ 6
1.1. Flood Overlay ......................................................................................... 7
1.2. Lawful Point of Discharge .................................................................... 8
1.3. Request for Information ....................................................................... 9
Item 10: Issue – Earthworks ..............................................................................9
Item 11 9
Item: Flood impact assessment ........................................................................9
Item 16 / 17 ...................................................................................................... 10
Items – 8 - 20.................................................................................................... 10
Item 21 11
Item 23 / 24 ...................................................................................................... 12
1.4. Further Advice ..................................................................................... 13
Issue - Stormwater Quality ............................................................................. 13
Information Request........................................................................................ 14
Detention Basin ................................................................................................ 15
2. STORMWATER QUANTITY.............................................................. 18
2.1. Hydrologic Assessment ...................................................................... 18
2.1.1. Existing Scenario .............................................................................. 18
2.1.2. Rational Method Check ................................................................... 19
2.1.3. Developed Scenario ......................................................................... 21
2.1.4. Mitigation Scenario.......................................................................... 23
2.2. Flood Investigation .............................................................................. 25
2.2.1. Flood Model ...................................................................................... 25
2.2.2. Existing Scenario (E05) .................................................................... 25
2.2.3. Proposed Scenario (P06)................................................................. 25
2.2.4. Afflux .................................................................................................. 25
2.2.5. Peak Flow .......................................................................................... 26
2.2.6. Flood Storage ................................................................................... 26
2.2.7. Flood Immunity ................................................................................ 27
3. STORMWATER QUALITY ................................................................ 29
3.1. Design Objectives ................................................................................ 29
3.2. Stormwater Quality Treatment ......................................................... 29
3.2.1. Strategy ............................................................................................. 29
3.2.2. MUSIC Parameters........................................................................... 29
3.2.3. Catchment Areas .............................................................................. 30
3.2.4. MUSIC Model Layout ....................................................................... 31
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3.3. Treatment Measures .......................................................................... 32
3.3.1. Bioretention System ......................................................................... 32
3.3.2. Sediment Forebays .......................................................................... 33
3.4. Results .................................................................................................. 33
4. CONSTRUCTION PHASE MANAGEMENT ...................................... 35
4.1. Erosion and Sediment Control .......................................................... 35
5. ESTABLISHMENT AND OPERATIONAL PHASE
MANAGEMENT ............................................................................... 36
5.1. Establishment ...................................................................................... 36
5.2. Operational .......................................................................................... 36
6. CONCLUSION .................................................................................. 37
7. REFERENCES.................................................................................... 38
List of Tables
Table 1-1: Reformatted MUSIC results ........................................................ 14
Table 2-7: Pavilion St Road capacity calculation using Manning’s’
equation .......................................................................................................... 17
Table 2-1: Summary of Existing Catchment Parameters .......................... 19
Table 2-2: Existing Catchment Peak Flows .................................................. 19
Table 2-3: Comparison of WBNM and Rational Method Peak Flows –
SUB3 ................................................................................................................ 21
Table 2-4: External catchment overland flow (entering site) and pipe
flow (diverted around site via Pavilion St)................................................... 22
Table 2-5: Summary of Developed Catchment Parameters ..................... 22
Table 2-6: Comparison of Peak Flows At Site Outlet (Existing Vs.
Developed)...................................................................................................... 22
Table 2-7: Summary of Basin Structure Details ......................................... 23
Table 2-8: Comparison of Peak Flows (Existing Vs. Mitigated) ................. 24
Table 2-9: Comparison of 1% AEP event across all durations (Existing
Vs. Mitigated) .................................................................................................. 24
Table 2-10: Existing and Proposed Peak discharge at the Site
Boundary. ....................................................................................................... 26
Table 2-11: 1% AEP Flood Storage Comparison. ........................................ 26
Table 2-12: Lot Levels Compared to Adjacent 1% AEP Peak Flood
Levels............................................................................................................... 27
Table 3-1: Site Stormwater Quality Objectives (Operational Phase) ....... 29
Table 3-2: Urban land use (Split Source Nodes) - Pollutant Export
Parameters ..................................................................................................... 30
Table 3-3: MUSIC Runoff Generation Parameters ..................................... 30
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Table 3-4: Catchment Areas ......................................................................... 30
Table 3-5: Bioretention Design Parameters ............................................... 33
Table 3-6: Sediment Forebay Design Parameters...................................... 33
Table 3-7: MUSIC Results – Load Based Pollutant Outputs ...................... 33
Table 3-8: MUSIC Results – Portion of total pollutant loads for External
Catchment and Site ....................................................................................... 34
List of Figures
Figure 1-1: Site Location .................................................................................. 7
Figure 1-2: Overland Flow Paths and Flood Hazard Overlay Mapping
(2019 Aerial)...................................................................................................... 8
Figure 1-3: The development site (current and original developments)
source loads from the MUSIC model .......................................................... 14
Figure 1-4: Moderate Flood Extent (Source: Noosa Council Disaster
Mapping) ......................................................................................................... 16
Figure 1-4: Pavilion St Road Cross-Section ................................................. 17
Figure 2-1: Existing Catchment Delineation................................................ 18
Figure 2-2: Developed Catchment Delineation .......................................... 21
Figure 2-3: Proposed cut / fill areas and extent of 1% AEP (CC) flood
level ................................................................................................................. 27
Figure 2-4: 1% (2100) AEP Peak Water Surface Elevation Reporting
Locations ......................................................................................................... 28
Figure 3-1: WSUD Catchment Locality Plan ................................................ 31
Figure 3-2: MUSIC Model Layout .................................................................. 32
Appendices
Reconfiguration of Lot Plan and Concept Engineering
Rational Method and WBNM Output
Existing Flood Map
Proposed Flood Map
Flood Afflux Map
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona
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1. Introduction
Colliers Engineering and Design have been engaged by PSP Developments Pty Ltd to prepare a Stormwater
Management Plan (SMP) in support of a development application to Noosa Shire Council (NSC) over land
located at 33 Pavilion Street, Pomona (Lot 4 RP809059). This development application seeks a development
permit for a Reconfiguration a Lot (ROL) to create 8 residential lots. The site has an existing building at Lot 1
and no works are required to create lot 1.
The proposed outcome of this document is to identify stormwater management options that could be
implemented within the development in order to achieve the requirements and targets of NSC Planning
Scheme “Water Quality and Drainage Code” as well as the relevant provisions of State Planning Policy (SPP
2017). The intent of the codes associated with these documents will be achieved through the appropriate
integration of stormwater management options within the proposed residential land-use. The objectives of
this Stormwater Management Plan are to:
Detail the proposed stormwater quality management strategy and how the load reduction
objectives specified by the State Planning Policy (SPP, DSDIP 2017) and NSC Planning Scheme are
achieved during the operational phase of the development;
Consider suitable Stormwater Quality Improvement Devices (SQID’s) based on Water Sensitive
Urban Design (WSUD) principles;
Outline the maintenance requirements for the proposed stormwater quality improvement
devices;
Ensure the development achieves non-worsening of stormwater flows downstream of the site;
and
Demonstrate how the lawful point of discharge requirements for the site will be achieved.
Demonstrate development is located outside of Flood Hazard Overlay Mapping.
The proposed development layout and preliminary engineering drawings is provided in Appendix A.
1.1 Site Characteristics
The location of the proposed development site is shown in Figure 1-1, with a total land holdings area
covering 3.33ha. The site is consistent with a rural residential land use type with some wooded vegetation
cover over the site. The site is accessed by Pavilion Street to the east and Majestic Place to the south and is
bounded by private allotments to the north, east and south. Cooroora Creek is located in the adjacent
property to the west.
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SITE Figure 1-1: Site Location 1.1. Flood Overlay The rear of the site is partially influenced by flooding from Cooroora Creek, which is located to the west of the property. The inundation extent identified in the Flood Hazard Overlay is highlighted in Figure 1-2. 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 7
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Figure 1-2: Overland Flow Paths and Flood Hazard Overlay Mapping (2019 Aerial)
1.2. Lawful Point of Discharge
As outlined by the Queensland Urban Drainage Manual (4th Edition – Institute of Public Works Engineering
Australasia, Queensland Division) a test can be undertaken to determine whether a lawful point of
discharge exists:
The criteria for determining the lawful point of discharge are:
(i) 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).
It is proposed that discharge of runoff from the proposed development site will be maintained to the
property boundary within the mapped waterway.
It is considered that discharge from the site will be managed in such a manner as to not substantially
damage third party property, and as a result it is considered suitable lawful points of discharge has been
identified and achieved.
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1.3. Request for Information
An information request from Noosa Council, dated 15 August 2023, requested further information on the
development application (RAL23/0013). Items relevant to the Flood Investigation and Stormwater
Management Plan are listed below together with the relevant response(s).
Item 10: Issue – Earthworks
Section 2.2.1 of Collier’s Flood and Stormwater Plan proposes the following:
a. A drain at a depth of 0.4m in a 3-metre-wide easement; and
b. 1,250m of cut at a depth of 0.1m.
Insufficient information has been provided demonstrating the location and extent of these works. Any works that
is located outside of the subject site (33 Pavilion Street) must be supported with the landowners’ written consent.
Response:
The earthworks (drain in 3mtr easement, and 1250m3 cut) are part of 25 Pavilion works and have been
constructed.
Section 2.2.1 of the SMP has been updated to show the works as “existing” to clarify this point.
Item 11
Provide additional detail demonstrating the location and extent of the works proposed in Section 2.2.1 of Collier’s
Flood and Stormwater Plan. The additional detail must be prepared by a suitably qualified person (RPEQ –
Registered Professional Engineer of Queensland) and include, but not be limited to:
a. details of the proposed stormwater drain and easement (location, grades, lots benefitted and burdened);
and
b. where works are located outside of the subject site (33 Pavilion Street), provide all respective landowners’
written consent.
Response:
The stormwater drain and easement are not proposed works. They are existing works as part of adjoining
application 25 Pavilion. Section 2.2.1 SMP has been updated to clarify this point.
Item: Flood impact assessment
The submitted Flood and Stormwater Plan prepared by Colliers includes aerial imagery that does not reflect the
recent subdivision at 25 Pavilion Street (now Majestic Drive). It is unclear to Council if survey data reflecting the
newly completed works has been used in conjunction with Lidar to provide an accurate assessment of the
proposed flood and afflux mapping. Council is concerned that the proposed earthworks may adversely affect the
flood characteristics of external sites.
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Response:
Note: Afflux mapping has been updated since V1 of the report as follows:
existing scenario has been revised from E03 to E04,
proposed scenario has been revised from P04 to P06.
The existing scenario (E04) includes:
site survey of 25 Pavilion St, Pomona, prior to development works.
a design surface of the engineering design at 25 Pavilion St, Pomona
SMP-V2 has figures updated with aerial imagery that reflects the recent subdivision at 25 Pavilion Street
(now Majestic Drive), showing the subdivision has been considered in the existing scenario.
Item 16 / 17
16. Provide additional comment detailing that the submitted Flood Investigation has been conducted using recent
survey data of the completed works along 25 Pavilion Street (now Majestic Drive).
17. Alternatively, provide an amended Flood Investigation th tilizesses recent survey data in conjunction with
Lidar to more accurately assess the impacts the proposed subdivision works will have on flood depths on external
sites. The amended Flood Investigation must be prepared by a suitably qualified person (RPEQ – Registered
Professional Engineer of Queensland).
Response:
The flood investigation has conducted using the design surface supplied by TOD consulting, which 25
Pavilion St has been constructed to, and is considered of sufficient accuracy for the purpose of the flood
investigation.
Items – 8 - 20
Provide an updated flood impact assessment and proposal plans which address the following:
18. Provide updated proposal plans which show drainage easement overall balance areas of Lot 9 which will
remain below the 1%AEP (2100) flood level
19. Amend the earthworks design for Lots 8 and 9 such that there is no net loss of floodplainstorage (e.g. provide
partial retaining)
20. Provide an additional flood afflux map showing the impacts associated with this development only (i.e. not
combined impacts with 25 Pavilion St development).
Response:
18. Figure 2-3 in the report has been added to clarify proposed cut and fill areas in relation to the 1% AEP
(Climate change) flood level/
19. Updated
20. Afflux map updated (E05 vs P06) – Refer SMP-V2 Appendix E.
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Item 21
Issue: Storage sizing does not appear to be in accordance with QUDM and ARR2019.
Information Request
21. Provide revised sizing/modelling and associated engineering drawings and reporting for the detention storage
proposed for the development site, which achieves the following:
a. Is undertaken using the ensemble storms approach of ARR2019
b. The detention storage volume of ~200m3/ha (of development) is considered low for this type of land use
change. The pervious initial loss reported in the SWMP appears to be much lower than the
recommendations of either QUDM or ARR2019 and is likely to result in under-sizing of the detention
storage due to an over-estimate of the pre-development peak flows. Justify the assumed initial loss or
adopt a revised value consistent with QUDM and ARR2019
c. Provide a copy of the WBNM model for review
d. Update the basin design to ensure the freeboard requirements of QUDM are achieved for the 1%AEP
(2100) event. The proposed freeboard of 50mm is not acceptable as it presents an unacceptable risk of
embankment overtopping and failure
e. Demonstrate no increase in peak flows for all events up to and including the 1%AEP (2100) event, for the
range of durations applicable to the downstream land, not just the critical duration at the site boundary.
f. Explanation is required for why the 1%AEP (2100) peak flow is predicted to decrease in Table 2-5 rather
than increase following development?
g. Are Tables 2-1 and 2-2 meant to refer to Sub3 rather than Sub1 (the neighbouring site)?
h. The SWMP makes a number of assumptions regarding contribution of flows from East of Pavilion St,
without justifying how this has been quantified. Calculations supporting the estimated conveyance
capacity of Pavilion St are requested.
Response:
21. Figure 2-3 in the report has been added to clarify proposed cut and fill areas in relation to the 1% AEP
(Climate change) flood level/
a. iWBNM Lite (2019 version) ultilised, which applies ARR2019 with ensemble storms.
b. IL revised to 35mm and CL revised to 2.4 mm/hr in line with ARR2019 datahub values.
c. Files will be supplied to Council as requested.
d. The updated basin achieves a freeboard of 0.19m. This improves upon the existing approved
freeboard (0.14m) currently provided within the basin for 25 Pavilion St, Pomona, as per
Stormwater Management Plan 21-066-SMP02-V1.
The augmented basin design has considered flood storage area within the flood overlay, and has
limited fill to achieve a balance between providing basin capacity, and achieving flood storage area.
As the basin has capacity to contain the 1% AEP (climate change) in the fully blocked case, it is
considered that the basin design satisfies the multiple objectives at the site.
e. Refer Table 2-9 for a summary of peak mitigated flows for the 1% AEP event across all storm
durations. The analysis demonstrates non-worsening has been achieved across a range of
durations.
f. Table updated.
g. Tables updated.
h. Table 2-4 has been provided to qualify the contribution of flows from catchments Ex1 and Ex2 east
of Pavilion St, demonstrating the portion of 10% AEP pipe flow diverted around the site and the
portion of overland flow that tops Pavilion St and enters the site.
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Item 23 / 24 Iss–e - Stormwater Quality It is unclear how compliance with the pollutant load reduction targets have been calculated. The development source node unmitigated loads should be factored by the required pollutant reduction percentages and then compared to the results from the model. It is unclear if this has been done. Information Request: 23. Provide a copy of the MUSIC model. 24. Provide further reporting of results which shows: the unmitigated loads from the development site(s) nodes only, the required load reductions (kg/yr) from the development site loads in order to meet the targets, and the mitigated results at the receiving node. Response: 24. Calculations for mitigated loads are shown in Table 3-8, demonstrating that the bioretention basin meets the target reductions for the development site. 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 12
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1.4. Further Advice
Further advice was received from Noosa Council, dated 7 November 2023, regarding the development
application (RAL23/0013). The further advice letter asks for the proposal to comply with the Noosa Plan for
stormwater items listed below.
Issue - Stormwater Quality
It is unclear how compliance with the pollutant load reduction targets has been calculated. The scheme requires
an 80%/60%/45% reduction in TSS/TP/TN for the unmitigated development site loads. Since the bioretention
device receives flows from areas outside the development, a manual calculation of compliance with this target is
required, based on the MUSIC model results.
This is achieved by:
1. Extracting the development site (current and original developments) source loads from the model
2. Calculating the required pollutant load removal by multiplying (1) by 80%/60%/45%
3. Comparing the required load removal (kg/yr) to the actual load removal achieved by the device
This does not appear to have been done.
Response:
The SMP demonstrates an 80%/60%/45% reduction in TSS/TP/TN for the unmitigated development site
loads according to the scheme as summarized in Table 3-7 and Table 3-8.
The information provided in the SMP-V2 has been reformatted as per the above request:
1. The source loads of the current and original developments were extracted from the model (refer
Figure 1-3) and are summarized in the “Unmitigated (kg/yr)” column of Table 1-1.
Note that there is a minor difference between Figure 1-3 and Table 3-7 as MUSIC is a stochastic model, with
randomness resulting in minor changes in results between model runs.
2. The required pollutant load removal (2) was calculated by multiplying (1) by 80%/60%/45%. This
information is provided in Table 1-1.
3. The actual load removal (3) achieved by the device exceeds the required load removal (2) and therefore
meets the target reductions as per the scheme.
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Figure 1-3: The development site (current and original developments) source loads from the MUSIC model
Table 1-1: Reformatted MUSIC results
(1) (2)
Development Required (3)
site pollutant load Target Total load Reduction
Pollutant Compliance
unmitigated removal for Reduction removal by Achieved (%)
source load development device (kg/yr)
(kg/yr) (kg/yr)
TSS 4,650 3,720 80% 3750 81%
TP 9.29 5.6 60% 6.9 74%
TN 51.6 23.2 45% 27 53%
GP 485 437 90% 638 100%
Information Request
Provide a copy of the MUSIC model and/or updated reporting addressing the above.
MUSIC results are as per model supplied with SMP-V2.
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Detention Basin
Detention Basin - storage sizing does not appear to be in accordance with QUDM and ARR2019.
Information Request
1) Provide revised sizing/modeling and associated engineering drawings and reporting for the detention storage
proposed for the development site, which addresses the following:
a) The response states that the initial losses have increased, however page 14 of the SWMP states that the
losses are unchanged. This needs to be resolved.
b) Provide a copy of the WBNM model for review
c) The results provided in Appendix B show peak flows increasing for a number of event frequencies and
durations. Demonstrate no increase in peak flows for all events up to and including the 1%AEP (2100)
event, for the range of durations applicable to the downstream land, not just the critical duration at the
site boundary
d) The external catchment areas stated in the existing case (Table 2-1) and developed case (Table 2-5) are
significantly different. There does not seem to be any valid reason for this. Sub3 and Sub4 also change
between tables, though these are within the site and this change may be due to physical changes. Justify
or resolve these differences and provide a ‘developed’ catchment plan where significant differences to the
existing case do exist.
e) Provide calculations quantifying the underground pipe and surface flow capacity of Pavilion St, in order
to demonstrate that the assumptions made in relation to the amount of external catchment flow which
enters the site are valid.
Response:
a) This is a typographical error. Losses in Section 2.1.1 have been updated to reflect the existing
scenario WBNM model initial and continuing loss of 35mm and 2.4mm/hr, in line with ARR2019
datahub values.
b) Supplied with SMP-V3.
c) The basin design is based upon augmentation of an approved and constructed basin at 25 Pavilion
St with outlet structure modelled as constructed. Effort has been taken to develop a design that
mitigates peak flows back to pre-development flow rates whilst improving upon freeboard of the
approved basin, as per Council’s RFI item 21 (d), dated 15 August 2023. The design achieves both
objectives, demonstrating:
non-worsening has been achieved across the full range of durations for peak 1% AEP
event (Appendix B).
the critical peak flows for the mitigated scenario are below the peak existing scenario flow
rate across all storm events.
The basin discharges to the local overland flow path which is significant in cross section due to the
fact that it acts to also convey breakout flows from the regional system in events greater than a
moderate event (approximately equivalent to at 10% AEP event). The use of this area within both
sites is restricted by existing regional flood conditions across the sites.
While it is noted that there are minor increases in some duration events (not the critical event) with
a single AEP (as provided in Appendix B) the minor change in small, frequent and short duration
events will be of no consequence and will be unlikely to create impact on downstream properties.
The basin is located a sufficient distance from the downstream boundary that any minor change (in
the order of 200 L/s) will be spread and flow across the downstream boundary with no observable
impacts across the width of the significant flowpath.
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In addition, the magnitude of the increases (change) in non-critical durations (pre-post) still remain
orders of magnitude below the 1% AEP peak flow for the regional event. For example, the 1% AEP
peak flow in the regional event is in the order of 300 m3/s and the greatest change across
equivalent duration within an AEP event is 0.22 m3/s, (approximately 0.07% of the regional 1% AEP
flow). Based on guidance provided in the Flooding and Stormwater Management
Guidelines (Sunshine Coast Council, 2020) policy this is argued to be an acceptable difference.
Therefore, the change in non-critical durations is considered not to be of any significant
consequence within the context of the overland flow path and will not results in nuisance or
damage the downstream property.
Based on the above, and that the proposed solution provides an improved performance outcome
above the current approved basin, it is considered that the proposed detention basin meets the
performance objectives of the Noosa Planning Scheme, the intent of the QUDM guidelines and is
analysed using ARR2019 methodology. As such it is considered that the basin design is sufficient to
meet the approval criteria of the application.
Figure 1-4: Moderate Flood Extent (Source: Noosa Council Disaster Mapping)
d) Across some storm durations there is a minor difference in flow rates above existing. These
differences are largely unobservable above 90 min, and resolved once the duration is greater than
270 min (4.5 hours):
e) Differences between external catchments have been corrected in Table 2-1 to reflect the existing
scenario WBNM model. There is no difference in the external catchment size modelled for the
existing and developed scenarios.
Differences between SUB3 and SUB4 reported in SMP are correct. This is due to grading within the
site adjusting catchment delineation. Refer to Figure 2-1 and Figure 2-2 for details.
The difference in catchment delineation between existing and developed scenarios does not
materially change the results of the model. This is because SUB3 is routed to SUB4, which connects
to the model outlet “SINK” in the existing scenario, bypassing sub-catchments SUB1 and SUB2. In
the proposed scenario SUB3 is routed to SUB1, where the basin structure is located, in alignment
with the engineering drawings for the proposed development (Appendix A). Refer Table 2-1 and
Table 2-5 for model routing.
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f) The 10% AEP capacity of the road is as per the approved matches the approved SMP for the
adjacent developments at 25 Pavilion St, which states:
“Existing drainage capacity of Pavilion Street is approximately equivalent to the 10% AEP storm event,
with flow greater than this overtopping the verge and entering the site.”
This has intentionally been kept consistent between SMPs, and demonstrates that the proposed
augmented basin achieves greater storage and improved freeboard in comparison to the
approved SMP for 25 Pavilion St.
A road capacity calculation was completed to confirm this assumption using a cross section of the
road based on LIDAR data. Refer to Table 1-2 and Figure 1-5. Manning’s equation indicates that the
road has a road capacity (1.16 m3/s) greater than the 10% AEP flow rate from the external
catchments (0.437 m3/s for EX1 and 0.165 m3/s for EX2). Therefore, the assumption that Pavilion St has
capacity for 10% AEP flows is conservative, and freeboard within the basin is expected to be greater
than modelled.
Table 1-2: Pavilion St Road capacity calculation using Manning’s’ equation
Parameter Value Unit
Cross sectional area 1.24 m2
Channel slope 0.026 m/m
Wetter perimeter 11.21 m
Manning's (n) 0.04
Hydraulic radius (R) 0.1 m
Velocity 0.93 m/s
Froude Number 0.73
Flow rate (Q) 1.16 m3/s
Road Cross Section
0.2
0.18
0.16
0.14
0.12
Elevation (m)
0.1
0.08
0.06
0.04
0.02
0
0 2 4 6 8 10 12
Ground Level
Distance (m)
Water level
Figure 1-5: Pavilion St Road Cross-Section
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2. STORMWATER QUANTITY
The objective of this component of the study is to investigate the potential impact that the proposed
development will have on peak flows discharging downstream from the site.
2.1. Hydrologic Assessment
Hydrologic modelling of the catchments has been undertaken using WBNM software (Boyd et al, 2019),
developed jointly by the University of Wollongong, Rienco Consulting and Balance R&D. The 2019 version
has been used for this investigation which utilizes ARR2019 hydrology.
Modelling has been carried out for the 1, 2, 5, 10, 20, 50 and 100-year Average Recurrence Interval (ARI)
storm events for the following scenarios:
1. Existing Scenario (base case)
2. Developed Scenario
3. Mitigated Scenario
2.1.1. Existing Scenario
Sub-catchments have been delineated using 1m contours sourced from the NSC catalogue, developed
using 2015 LiDAR and site survey. The fraction impervious values have been calculated using aerial imagery.
Figure 2-1 shows the existing catchment delineation with a summary of parameters shown in Table 2-1.
Figure 2-1: Existing Catchment Delineation
The existing drainage capacity of Pavilion Street is approximately equivalent to the 10% AEP storm event,
with flow greater than this overtopping the verge and entering the site at both 25 and 33 Pavilion Street. To
account for this, the peak flow for SUB1-Ex was determined for the 10%, 5%, 2% and 1% AEP. The portion
of flow greater than the 10% AEP was converted into a ratio, which was then applied to the catchment area
as detailed below in Table 2-1. This ensured that flows from SUB1-Ex greater than the 10% AEP were
routed through the site.
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Table 2-1: Summary of Existing Catchment Parameters
Sub-catchment Downstream Area (ha) Imperviousness (%)
Catchment
Ex2 SUB3 1.960 50
Ex1 SUB1 0.287 50
SUB3 SUB4 2.085 21
SUB1 SUB2 2.079 11
SUB2 SUB4 1.354 5
SUB4 SINK 0.511 5
Ex1 (<10% AEP) 0.0* -
Ex1 (5% AEP) 0.049* 50
Ex1 (2% AEP) 0.093* 50
Ex1 (1% AEP) 0.116* 50
Ex1 (1% AEP CC) 0.152* 50
Ex2 (<10% AEP) 0.0* -
Ex2 (5% AEP) 0.300* 50
Ex2 (2% AEP) 0.618* 50
Ex2 (1% AEP) 0.782* 50
Ex2 (1% AEP CC) 1.032* 50
* area factored based on flow rate for events greater than 10% AEP
The WBNM model has been run for events from 1 to 100-year ARI and for durations of 20 minutes to 3
hours. A WBNM catchment lag factor of 1.6 was applied which is within the recommended range. An initial
and continuing loss of 35mm and 2.4mm/hr in line with ARR2019 datahub values. The resulting peak flows
for the critical duration are provided in Table 2-2 for each event at the outlet reporting locations.
Table 2-2: Existing Catchment Peak Flows
Event AEP 63.20 50% 20% 10% 5% 2% 1% 1%CC
%
Existing (m3/s) – SUB3 0.13 0.16 0.30 0.38 0.47 0.58 0.68 0.88
Existing (m3/s) – SUB4 0.33 0.43 0.72 0.92 1.21 1.55 1.86
2.1.2. Rational Method Check
Pre-development peak flows have been checked against peak flows determined using the Rational Method
(RM) for SUB3, as shown in
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Table 2-3. A time of concentration of 20.6 minutes was determined for SUB3 rational method. It can be seen there is values are generally within ten percent difference across events assessed, indicating that the WBNM model flows are suitable for use. Refer to Appendix B for a summary of rational method parameters used. 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 20
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Table 2-3: Comparison of WBNM and Rational Method Peak Flows – SUB3
Event AEP 63.20% 50% 20% 10% 5% 2% 1% 1%CC
Rational 0.15 0.18 0.28 0.34 0.41 0.52 0.60 0.72
Existing (m3/s) 0.13 0.16 0.30 0.38 0.47 0.58 0.68 0.88
Change (%) -13% -10% 7% 11% 14% 11% 13% 22%
2.1.3. Developed Scenario
The Developed Scenario has been modelled in WBNM by adjusting the site’s fractions impervious values
and catchment delineation to represent the proposed development. The impervious fraction for the
developed portion of the SUB1 (adjoining approval) and SUB3 has increased from 11% to 50% (values
consistent with ‘Urban Residential – low density (Including roads)’ catchments in QUDM (2017)). The
developed catchment delineation is shown in Figure 2-2. SUB1 and SUB3 represents the development with
flows being routed through the existing detention basin (which has been increased in volume). The
catchment parameters are summarised in Table 2-5.
Figure 2-2: Developed Catchment Delineation
Similar to the existing scenario, the existing drainage capacity of Pavilion Street is approximately equivalent
to the 10% AEP storm event, with flow greater than this overtopping the verge and entering the site. To
account for this, the peak flow for SUB1-Ex was determined for the 10%, 5%, 2% and 1% AEP. The portion
of flow greater than the 10% AEP was converted into a ratio, which was then applied to the catchment area
as detailed below in Table 2-4 and Table 2-5. This ensured that flows from SUB1-Ex greater than the 10%
AEP were routed through the site.
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Table 2-4: External catchment overland flow (entering site) and pipe flow (diverted around site via Pavilion St)
Flow 10% AEP 5% AEP 2% AEP 1% AEP 1% CC AEP
Area Flow Area Flow Area Flow Area Flow Area Flow
(ha) (m3/s) (ha) (m3/s) (ha) (m3/s) (ha) (m3/s) (ha) (m3/s)
TOTAL 1.960 0.437 1.960 0.534 1.960 0.671 1.960 0.768 1.960 0.982
EX2 Overland - - 0.300 0.097 0.618 0.234 0.782 0.331 1.032 0.545
Pipe 0.437 0.437 0.437 0.437 0.437
TOTAL 0.287 0.165 0.287 0.093 0.287 0.114 0.287 0.130 0.287 0.165
EX1 Overland - - 0.049 0.018 0.093 0.039 0.116 0.055 0.152 0.091
Pipe flow 0.075 0.075 0.075 0.075 0.075
Table 2-5: Summary of Developed Catchment Parameters
Sub-catchment Downstream Area (ha) Imperviousness (%)
Catchment
Ex2 SUB3 1.960 50
Ex1 SUB1 0.287 50
SUB3 SUB2 1.780 50
SUB1 SUB2 2.079 50
SUB2 SUB4 1.354 5
SUB4 SINK 0.819 5
Ex1 (<10% AEP) 0.0* -
Ex1 (5% AEP) 0.049* 50
Ex1 (2% AEP) 0.093* 50
Ex1 (1% AEP) 0.116* 50
Ex1 (1% AEP CC) 0.152* 50
Ex2 (<10% AEP) 0.0* -
Ex2 (5% AEP) 0.300* 50
Ex2 (2% AEP) 0.618* 50
Ex2 (1% AEP) 0.782* 50
Ex2 (1% AEP CC) 1.032* 50
* area factored based on flow rate for events greater than 10% AEP
The increased imperviousness and changes to catchment areas associated with the development resulted
in an increase in peak flows to the sites outlet as shown in Table 2-6. Mitigation will be required to ensure
non-worsening downstream and satisfy the lawful point of discharge requirements.
Table 2-6: Comparison of Peak Flows At Site Outlet (Existing Vs. Developed)
Event AEP 63.20% 50% 20% 10% 5% 2% 1% 1%CC
Existing (m3/s) 0.33 0.43 0.72 0.92 1.21 1.55 1.86 2.57
Developed (m3/s) 0.34 0.43 0.73 0.94 1.25 1.66 2.04 2.63
Change (m3/s) 0.01 0.00 0.01 0.02 0.04 0.11 0.18 0.06
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2.1.4. Mitigation Scenario
When comparing the peak flows in the existing and developed scenarios, increases in the peak discharge
are predicted at the site outlet. A detention basin is proposed to attenuate peak flows discharging from the
site to demonstrate non-worsening and meet the legal point of discharge requirements.
All modelling parameters remain consistent between the developed and mitigated scenarios, with the
addition of detention basins. The proposed basin structure details are summarised in Table 2-7 with
Concept Engineering Drawings included in Appendix A.
Table 2-7: Summary of Basin Structure Details
Sub-catchment Existing Basin Upgraded Basin
Elevation (RL) Storage (m3)
0 0 0
0.1 26 35
0.2 55 74
0.3 87 117
0.4 123 163
0.5 162 214
0.6 205 268
0.7 251 327
0.8 301 391
0.9 338 458
0.97 - 508
Pipe Outlet 1 x 450mm RCP at RL0.0m 1 x 450mm RCP at RL0.0m
Bioretention Outlet Not modelled 1 x 450mm RCP at RL-0.9m
Weir Outlet 4m wide at RL.0.60m 8m wide at RL.0.60m
Crest Level RL 0.97m RL 0.97m
Q100CC WSL RL 0.83m RL0.78m
Q100CC Freeboard 0.14m 0.19m
Peak flows from the mitigated scenario modelling are presented in Table 2-8 with a comparison against the
existing peak flows. The results show that there is non-worsening for events up the 1% AEP. The intent of
sizing the detention basin is to mitigate flows up to the 10% AEP storm event to ensure non-worsening of
discharges into the downstream flow path. In larger events, flows from the site will start to sheet flow
across the rear of the site to Cooroora Creek. As the discharge point for the site becomes inundated from
Cooroora Creek flooding in the major storm event (refer Figure 1-2), it is considered that the non-worsening
has been achieved.
Table 2-8 contains a summary of peak mitigated flows for the 1% AEP event across all storm durations. The
analysis demonstrates non-worsening has been achieved across a range of durations.
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Table 2-8: Comparison of Peak Flows (Existing Vs. Mitigated)
Event AEP 63.2% 50% 20% 10% 5% 2% 1% 1% CC
Existing (m3/s) 0.33 0.43 0.72 0.92 1.21 1.55 1.86 2.57
Mitigated (m3/s) 0.34 0.43 0.66 0.82 1.04 1.49 1.82 2.46
Change (m3/s) 0.01 0.00 -0.06 -0.10 -0.17 -0.06 -0.04 -0.10
Table 2-9: Comparison of 1% AEP event across all durations (Existing Vs. Mitigated)
Duration
10 15 20 25 30 45 60 90 120 180 270 360
(min)
Existing
0.98 1.68 2.13 2.45 2.57 2.49 2.45 2.29 2.16 2.04 1.77 2.02
(m3/s)
Mitigated
0.91 1.53 1.96 2.28 2.38 2.46 2.35 2.20 2.06 1.89 1.69 1.92
(m3/s)
Change
-0.07 -0.15 -0.17 -0.17 -0.18 -0.03 -0.09 -0.09 -0.11 -0.15 -0.08 -0.10
(m3/s)
Table 2-7 provides a summary of the basin configuration and it is noted there is 0.19m freeboard from the
1% (2100) AEP flood level to the basin crest. A sensitivity analysis was undertaken to assess the impact of
100% blockage of both basin outlet configurations. Under this scenario the flood level rose to RL0.89m and
demonstrates the spillway is able to convey the 1% (2100) AEP flows under fully blocked conditions without
overtopping the embankment crest. Given this and the fact that the land downstream of the detention
basin will remain undeveloped it is considered that the 0.08m from the 1% (2100) AEP flood level (and
0.37m from spillway level) to basin crest level is acceptable.
It is noted that with the inclusion of 0.3m of Extended Detention Depth for the co-located bioretention
basin, the total Q20 depth for the basin is expected to be less than the 1.2m recommended by QUDM for
safety concerns.
Refer to Appendix B for summary of WBNM output.
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2.2. Flood Investigation
The proposed development footprint is currently largely located outside of the NSC Flood Hazard Overlay
Mapping; however, the rear of lot 8 and 9 is partially inundated in the 1% (2100) AEP. The Noosa Plan Flood
Hazard Overlay Code identifies that any development / filling below the 1% (2100) AEP flood level must
demonstrate that no off-site impacts and no loss of flood plain storage is demonstrated.
Council’s Pomona Flood Model was utilised to represent the development proposal and demonstrate the
requirements of the Flood Hazard Overlay Code.
2.2.1. Flood Model
The NSC Pomona Flood Model was utilised as the basis for the flood assessment to represent flooding in
the 1% (2100) AEP event. The model was setup and run for the Existing and Proposed Scenarios. The
model was utilised in full, with the following updates made to represent these two scenarios:
Existing (E05)
Reduce model grid size from 5m to 2m.
Update model terrain to utilise 2015 Lidar and site survey.
Model was run using HPC and the latest TUFLOW engine (version 2020-10-AA).
Represented 1D channels in 2D with smaller grid size.
Site survey of 25 Pavilion St, Pomona, prior to development works.
Represented design for 25 Pavilion St, Pomona, including:
o surface of preliminary engineering design
o drain in 3m easement (approx. 0.4m deep at 1% grade).
o area of cut, 1,250m2 and 0.1m deep.
Site survey of 33 Pavilion St, Pomona.
Proposed (P06)
Update model terrain to include updated engineering design for 33 Pavilion St, Pomona (supplied
by TOD Consulting, 21 September 2023).
2.2.2. Existing Scenario (E05)
The existing case model has been setup and run for the 1% (2100) AEP flood event. The results of this have
been used as the basis for assessing the potential impacts that may result from the development.
Appendix C details the existing flood extent in relation to the development site.
2.2.3. Proposed Scenario (P06)
The proposed case model has been setup and run for the 1% (2100) AEP flood event, which incorporates
the proposed development site. Appendix D details the proposed flood extent in relation to the
development site. An indicative site plan is overlaid on this figure to highlight how the development relates
to the flood extent.
2.2.4. Afflux
Afflux mapping has been undertaken for the 1% (2100) AEP events to identify whether there are any
impacts resulting, and if so, whether an alternative development arrangement needs to be investigated.
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Appendix E details the afflux map which compares the existing and proposed case for the 1% (2100) AEP
flood levels. It is noted that based on the current development arrangement there are no increases in flood
levels noted either upstream or downstream as a result of the development site itself.
2.2.5. Peak Flow
The assessment found the peak discharge at the site boundary are predicted to decrease slightly. This is
shown in Table 2-10 which compares the Existing and Proposed peak discharge at the site boundary. As
such it is considered that non-worsening is achieved, and the development does not impact peak flow rates
in the regional flood event.
Table 2-10: Existing and Proposed Peak discharge at the Site Boundary.
Peak Flow 1% (2100) AEP
Existing – E03 (m3/s) 304.53
Proposed – P06 (m3/s) 303.96
Change (m3/s) -0.57
2.2.6. Flood Storage
A flood storage assessment has been completed over the site to ensure there is no loss of flood plain
storage has resulted from the development. The assessment includes the adjacent site at 25 Pavilion St, as
a small amount of earthworks to extend into 25 Pavilion St is proposed to augment the capacity of the
detention basin. The assessment found that there was some loss of flood plain storage due to the
development. Therefore, a proposed (with cut) scenario is proposed to achieve the flood storage balance.
For the existing flood storage calculation, the existing peak 1% (2100) AEP flood surface was compared to
the existing model terrain (after construction of 25 Pavilion St). Similarly with the proposed flood storage
calculation, the proposed (no cut) peak 1% (2100) AEP flood surface was compared to the proposed model
terrain. The proposed (with cut) scenario incorporates an area of shallow cut to offset loss of floodplain
storage between the building pad fill at lot 8 and the vegetation covenant. Refer to engineering drawings
(Appendix A) for extent of proposed cut.
Details of the flood plain storage within 33 and 25 Pavilion Street, Pomona, in the existing, proposed and
mitigated cases is summarised below in Table 2-11. A summary of proposed cut and fill areas in relation to
the 1% AEP (Climate change) flood level is shown in Figure 2-3.
Table 2-11: 1% AEP Flood Storage Comparison.
Scenario Flood Plain Storage (m3)
25 Pavilion St 33 Pavilion St Total Balance
Existing 7899 10440 18339
Proposed (no cut) 7890 10353 18243 -96
Proposed (with
7890 10449 18339 0
cut)
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Existing 1% AEP flood level
Area of shallow cut to offset
loss of floodplain storage.
Fill – earthworks to augment the
capacity of the existing basin
Fill at lot 8 building platform
Figure 2-3: Proposed cut / fill areas and extent of 1% AEP (CC) flood level
2.2.7. Flood Immunity
The NSC Planning Scheme identifies the Defined Flood Event, from which freeboard is set is the 1% (2100)
AEP flood event. Flood levels around the site for the 1% (2100) AEP are detailed for various reporting
locations as shown in Figure 2-4. This shows the proposed new lots are above the 1% (2100) AEP peak flood
levels. The peak flood level, minimum finished flood level and proposed lot level is shown in Table 2-12. It
is seen that greater than 500mm freeboard is provided to lot. It is recommended that future buildings on
each lot achieve a minimum of 500mm freeboard above the regional 1% (2100) AEP flood level.
Table 2-12: Lot Levels Compared to Adjacent 1% AEP Peak Flood Levels
Lot 1% AEP Peak Flood Minimum Freeboard Min Finished Floor Proposed Min Lot
Level (m AHD) to Floor (m) Level (m AHD) Level (m AHD)
8 83.44 0.5 83.94 87.61*
*Reported level is min lot level within the proposed building footprint area
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Figure 2-4: 1% (2100) AEP Peak Water Surface Elevation Reporting Locations It is noted that flood levels at 25 Pavilion St for the 1% (2100) AEP are unaffected by the proposal at 33 Pavilion St, with exception of the small area of afflux adjacent Lot 10. In this area, water surface elevation has increased from 83.71m AHD to 83.8m AHD. However, this has no impact on Lot 10, 25 Pavilion St, as the 1% AEP Peak Level adjacent the site is consistent with peak level of 85.11m AHD as per previous modelling for 25 Pavilion St (report 21-0166SMP01-V1). The afflux is reasoned to be a small area of instability within the model and is not predicted to be observable in practice. 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 28
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3. STORMWATER QUALITY
3.1. Design Objectives
This report identifies the stormwater quality management objectives for the operational phase (post-
construction phase) of the proposed development. Construction based stormwater quality management
objectives will need to be addressed as part of operational works documentation.
NSC Planning Scheme (2020) defines the post-construction phase Water Quality Objectives as shown in
Table 3-1.
Table 3-1: Site Stormwater Quality Objectives (Operational Phase)
Minimum reductions in mean annual loads from unmitigated development (%)
Total Suspended Total Phosphorous Total Nitrogen Gross pollutants
Solids (TSS) (TP) (TN) >5 mm
80 60 45 90
3.2. Stormwater Quality Treatment
3.2.1. Strategy
The objective of this report is to assess the stormwater quality measures required based on the
development layout to support the development application. Runoff from the development will be
collected in a stormwater drainage system and discharged into a bioretention basin prior to being
discharged from the site, with the existing bioretention basin associated with 25 Pavilion Street, being
extended.
3.2.2. MUSIC Parameters
An assessment of stormwater runoff quality from the existing conditions and proposed developed
conditions has been undertaken using the Model for Urban Stormwater Improvement Conceptualisation
(MUSIC) – Version 6.3, released in 2018.
Climate data for the catchment was sourced from the MUSIC model database. The rainfall and evaporation
data template for this site has been based on data from Cooroy from 1/1/1973- 31/12/1983 with six (6)
minute rainfall duration.
Table 3-2 and Table 3-3 outline the adopted source node parameters from “MUSIC Modelling Guidelines”
(Water By Design, 2010) that were used in the MUSIC model.
The site density of 10 dwellings per hectare, with the source nodes being assigned percentage impervious
values based on 10 dwellings per hectare
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Table 3-2: Urban land use (Split Source Nodes) - Pollutant Export Parameters
Total Suspended
Total Phosphorous Total Nitrogen
Solids
(Log10 mg/L) (Log10 mg/L)
Land Use Parameter (Log10 mg/L)
Storm Base Storm Base Storm Base
Flow Flow Flow Flow Flow Flow
Mean 2.18 1.0 -0.47 -0.97 0.26 0.20
Ground
Std Deviation 0.39 0.34 0.31 0.31 0.23 0.20
Mean 2.43 1.0 -0.30 -0.97 0.26 0.20
Road
Std Deviation 0.39 0.34 0.31 0.31 0.23 0.20
Mean 1.30 N/A -0.89 N/A 0.26 N/A
Roof
Std Deviation 0.39 N/A 0.31 N/A 0.23 N/A
Table 3-3: MUSIC Runoff Generation Parameters
Parameter Urban
Rainfall Threshold (mm) 1
Soil Capacity (mm) 500
Initial Storage (%) 10
Field Capacity 200
Infiltration Capacity Coefficient a 211
Infiltration Capacity Coefficient b 5
Initial Depth (mm) 50
Daily Recharge (%) 28
Daily Drainage (%) 27
Daily Deep Seepage Rate (%) 0
3.2.3. Catchment Areas
The development site and external catchment has been split into three catchments containing split source
nodes (road, roof and ground) representing total developed area reporting to the bioretention basin. As it
is proposed to extend the existing bioretention basin approved with reconfiguration of lot at 25 Pavilion
Street, the catchment setup from that approval has also been represented. Table 3-4 outlines the
catchment areas and imperviousness represented within the MUSIC model. The stormwater quality
catchments are provided in Figure 3-1.
Table 3-4: Catchment Areas
Catchment Road (ha) Roof (ha) Ground (ha) Total (ha)
1 0.342 0.250 0.791 1.384
Ex1 - 0.049 0.415 0.464
2 0.157 0.250 0.854 1.261
Ex2 0.091 0.639 0.73
Impervious % 60 100 15 -
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Figure 3-1: WSUD Catchment Locality Plan 3.2.4. MUSIC Model Layout As the management of urban stormwater needs to take a holistic approach, specific management measures need to be implemented in series to form a treatment train. The correct utilisation of various devices within the treatment train is imperative to target the desired pollutants, from the gross solids to the fine colloidal partials. Figure 3-2 shows the MUSIC model layout for the development. 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 31
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Figure 3-2: MUSIC Model Layout 3.3. Treatment Measures Runoff from the development will be treated through a bioretention basins. The locality of the treatment devices servicing the development is shown in Figure 3-1. 3.3.1. Bioretention System Bioretention systems use ponding above a treatment surface to maximise the volume of runoff flowing through the filtration media. They typically convey flows above the design event through overflow pits or a weir. The treatment system operates by firstly filtering surface flows through surface vegetation and then percolating runoff through prescribed filtration media. This media provides treatment through fine filtration, extended detention and biological uptake of nutrients. As these systems take approximately 12-24hrs to drain, the maximum depth of pondage allowed to occur over the filter area has been limited to 300mm, with a minimum filter media depth of 500mm. Table 3-5 summarises the proposed design parameters for the main bioretention system for this development, and highlights the size of the existing bioretention basin approved as part of 25 Pavilion Street, along with the upgraded size to account for the additional development from 33 Pavilion Street . As noted above this may be split into several devices on detailed design. It is to be noted that the Orthophosphate content of the filter media has been reduced to 30mg/kg in line with recent advice from Healthy Waterways. 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 32
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Table 3-5: Bioretention Design Parameters
Parameter Existing Basin Upgraded Basin
Extended Detention Depth (m) 0.30 0.30
Storage Surface Area (m2) 80 130
2
Filter Media Area (m ) 80 130
Unlined Filter Media Perimeter (m) 0.01 0.01
Saturated Hydraulic Conductivity (mm/hr) 200 200
Filter Depth (m) 0.5 0.5
TN Content of Filter Media (mg/kg) 400 400
Orthophosphate Content of Filter Media (mg/kg) 30 30
Exfiltration Rate (mm/hr) 0.0 0.0
Overflow Weir (m) 2 2
3.3.2. Sediment Forebays
To ensure that the deposition of coarse sediment on the filter media surface does not affect its function,
bioretention systems should be designed with pre-treatment to limit the amount of coarse sediment
reaching the filter media. The sediment forebay has been sized in accordance with the WaterByDesign’s
Bioretention Technical Design Guideline. Table 3-6 summarises the proposed design parameters for the
proposed sediment forebay.
Table 3-6: Sediment Forebay Design Parameters
Parameter Value
Site Catchment (ha) 2.645
Min Area of Forebay (m2) 26
Removal Efficiency (%) 80
3.4. Results
MUSIC modelling of the proposed treatment train for the developable area of the development at 25
Pavilion Street, Pomona was performed to ensure the WQO’s were achieved. Table 3-7 presents the load-
based outputs that are represented by this application. As the bioretention basin is treating an external
catchment, the loads generated from the external catchment have been subtracted from the mitigated
loads. The results show the mitigated scenario, which achieves compliant load reductions set out within the
NSC Planning Scheme. Calculations for mitigated loads are shown in Table 3-8.
Table 3-7: MUSIC Results – Load Based Pollutant Outputs
Mitigated
Unmitigated (Less External Reduction Target
Pollutant Compliance
(kg/yr) Catchment) Achieved (%) Reduction
(kg/yr)
TSS 4,660 900 81 80%
TP 9.27 2.38 74 60%
TN 51.8 24.5 53 45%
GP 485.0 0 100 90%
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 33
Page 35
Table 3-8: MUSIC Results – Portion of total pollutant loads for External Catchment and Site
Total Model Residual External Catchment Site – Mitigated load (less
Pollutant
load (kg/yr) Source Load (kg/yr) external catchment) (kg/yr)
TSS 2190 1290 900
TP 5.3 3.0 2.4
TN 43.5 19.0 24.5
GP 0 153 0
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 34
Page 36
4. CONSTRUCTION PHASE
MANAGEMENT
4.1. Erosion and Sediment Control
The management of the site during the construction phase is an important step in ensuring water quality
standards are achieved. Implementation of best practice Erosion and Sediment Control techniques is
imperative to managing the quality of runoff affected by construction works.
The following points provide general guidance on the management of stormwater during the construction
phase. Detailed Erosion and Sediment Control Management Plans should be developed in conjunction with
the Operational Works design prior to construction works commencing in accordance with the International
Erosion Control Association (IECA) - “Best Practice Erosion and Sediment Control (BPESC) document” and
overseen by a Certified Professional in Erosion and Sediment Control (CPESC) or Registered Professional
Engineer Queensland (RPEQ).
1. Establish a single stabilised entry/exit point for the site works;
2. Construct a shake-down grid at the entrance to facilitate the removal of sediment from trucks leaving
the site. The access road extending from the end of existing road or kerb to the grid should comprise
a 150-200mm deep pad of 40mm crushed rock;
3. Install sediment fences along the lower boundaries of the site;
4. Construct one or more strategically placed sediment basins in the proposed drainage reserve and
construct contour drains / bunds to direct disturbed runoff to the sediment basins;
5. Install bins and/or wind-proof litter areas on-site to minimise the dispersion of gross pollutants;
6. Maintain on site sufficient materials necessary for the emergency repair of all erosion control
devices. This includes silt fences, clean crushed rock for reapplication to the entrance road and for
replacement of rock within temporary drainage channels, and flocculants for settling sediment
basins;
7. Following each day’s construction works, ensure that any material on road surfaces is swept from
the road, and not permitted to be washed down the gutters and piped drainage systems;
8. Quality of pooled water within sediment basins are to be monitored prior to dewatering, sufficient
time should be given to allow sediment to settle (possible with the assistance of a suitable flocculent
if necessary) &/or filtering during pumping operations; and
9. Final establishment of bioretention basin should not occur until full stabilisation of upstream
catchment has occurred; preferably these should be temporarily turfed during the maintenance
period while dwelling construction is occurring.
It shall be the responsibility of the developer, through their principal contractor, to ensure that temporary
sediment and erosion controls are installed and maintained correctly.
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 35
Page 37
5. ESTABLISHMENT AND OPERATIONAL
PHASE MANAGEMENT
5.1. Establishment
Experience shows that the critical periods in the life of WSUD vegetated stormwater systems are the
construction and establishment phases. The timing and approach to these systems must be carefully
considered to ensure successful establishment and long-term performance. Bioretention systems are now
common stormwater treatment devices for new urban developments in Queensland. Successful
construction and allowing adequate time for the systems to establish is critical to their long-term
performance and function. Construction of the system is also linked to having suitable bioretention designs
in place to ensure, civil contractors have appropriate plans to construct to. Applying due care in the design
and construction phase will ensure the function of the system whilst also keeping on-going maintenance to
a minimum. It is highly recommended that the constructed activities be completed in accordance with the
Construction and Establishment Guidelines: Swales, Bioretention Systems and Wetlands (Apr 2010). This will
require a sacrificial turf layer to be installed to protect the filter media from the building phase.
5.2. Operational
It is not proposed for water quality monitoring of the bioretention system to be undertaken during the
operational phase of its life. The “Maintaining Vegetated Asset” guideline highlights that water quality
monitoring is not recommended to determine the performance of every vegetated stormwater asset, as it
is a specialized field that is complex and costly. In line with this guideline the on-going monitoring of water
quality from this device is not considered necessary considering the small size of the development.
The bioretention system will be maintained by the NSC, who as the asset custodian, will be responsible for
the on-going maintenance of the water quality device. Maintenance for the bioretention basin may involve
the following:
1. Scheduled inspections;
2. Removal of noxious plants or weeds;
3. Maintaining the desired vegetation;
4. Repairing erosion;
5. Unblocking inlets and outlets;
6. Removing litter and debris;
7. Managing algal or moss growth; and
8. Maintaining the permeability of the filtration.
Operations and maintenance should be conducted in accordance with the Maintaining Vegetated Stormwater
Assets (Feb 2012) guideline.
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 36
Page 38
6. CONCLUSION
Colliers Engineering and Design have been engaged by PSP Developments Pty Ltd to prepare a Stormwater
Management Plan (SMP) in support of a development application to Noosa Shire Council (NSC) over land
located at 33 Pavilion Street, Pomona (Lot 4 RP809059). This development application seeks a development
permit for a Reconfiguration a Lot (ROL) to create 8 residential lots. The site has an existing building at Lot 1
and no works are required to create lot 1.
It can be seen from the results, presented in Table 3-7 that the treatment measures proposed for the
development site achieve the performance criteria set by the NSC Planning Scheme (2020) and SPP (July
2017). Annual Load Reductions of Total Suspended Solids (TSS), Total Phosphorus (TP), Total Nitrogen (TN)
and Gross Pollutants (GP) between the Mitigated and Unmitigated Scenarios have been achieved through
the upgrade of the existing bioretention basin from 80m2 to 130m2.
It has been demonstrated that non-worsening of peak flows has been achieved to the discharge point for
events up to the 1% AEP event (refer Table 2-8). The results show that there is non-worsening for events up
the 1% AEP. The intent of sizing the detention basin is to mitigate flows up to the 10% AEP storm event to
ensure non-worsening of discharges into the downstream flow path. In larger events, flows from the site
will start to sheet flow across the rear of the site to Cooroora Creek. As the discharge point for the site
becomes inundated from Cooroora Creek flooding in the major storm event, it is considered non-worsening
has been achieved. The catchment size of Cooroora Creek reporting past the site is approximately 1,400 ha
and it is considered that no quantifiable change to downstream flooding conditions would result.
This plan demonstrates that effective treatment of stormwater at the proposed development can be
achieved through the integration of Water Sensitive Urban Design (WSUD) principles. Through the
incorporation of bioretention basins, the plan successfully demonstrates:
Compliance with the requirements of the NSC Planning Scheme and SPPs Load Based Objectives;
The end of line bioretention basin is upgraded to 130m2 to cater for the proposed development.
Ecological sustainability in terms of the development’s impact upon receiving waters and the viability of
the proposed site development.
Non-worsening of peak flows is achieved through the upgrade of the existing basin.
The development is located above the regional 1% (2100 AEP flood extent with 500mm freeboard
recommended to future dwellings on the new allotments.
We therefore request Council approval of the engineering components for the proposed development with
reasonable and relevant conditions. Detailed design may result in changes to the proposed strategy;
however, the design objectives will be maintained.
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 37
Page 39
7. REFERENCES
Noosa Shire Council (NSC) Planning Scheme 2020;
http://www.bom.gov.au/water/designRainfalls/revised-ifd (Bureau of Meteorology, Online Rainfall IFD
Data System);
State Planning Policy (Department of Infrastructure, Local Government and Planning, 2017);
Australian Rainfall and Runoff (Institute of Engineers Australia, 2019);
Queensland Urban Drainage Manual – 4th Edition (Institute of Public Works Engineering Australasia,
Queensland Division, 2017);
MUSIC Modelling Guidelines Version 1.0 (Water by Design, 2010);
Maintaining Vegetated Stormwater Assets (Water by Design, 2012); and
Construction and Establishment Guidelines: Swales, Bioretention Systems and Wetlands (Water by
Design 2012).
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona Page 38
Page 40
Appendices
Reconfiguration of Lot Plan and Concept Engineering
23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona
Page 41
PSP Developments
Pty Ltd
Proposal Plan
33 Pavilion Street,
Pomona
Lot 4 on RP809059
7
1001m²
Road
8 6
2.333ha
1001m²
²
e
15m Wid
STAGE 24
1033m² 5
1284m²
3
1042m²
601
284m²
2 1
1085m² 1661m²
STAGE 1
A3 1:1500
13285-PRO-01L
Page 42
Rational Method and WBNM Output 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona
Page 43
Project Name: 33 Pavilion St Col Fi sy Project No.: 23-0167 Author: L Gillis be Date: 04/10/2023 ARR: ARR2016 RATIONAL METHOD SUMMARY & RAINFALL DATA 10 15 20 25 30 45 60.00 90.00 120.00 180.00 270.00 360.00 540.00 720.00 1080.00 1440.00 1800.00 2160.00 2880.00 4320.00 1 1.0075669| 0.6553598 | 0.22487336 | -0.113584 | 0.0190669 | -0.001362 | 3.423E-05 2 1.1258065 | 0.6506015| 0.2318719 | -0.117139 | 0.0198273 | -0.001428 | 3.616E-05 5 1.424489 | 0.6620312| 0.222184 | -0.115032 | 0.0197897 | -0.001441 | 3.667E-05 10 1.5850968 | 0.6825591| 0.20021482 | -0.10711 | 0.0185666| -0.001353 | 3.418E-05 20 5% | 1.7200166| 0.7080383| 0.17219149 | -0.096592 | 0.0168551| -0.001224 | 3.048E-05 50 2% | 1.8736345| 0.7649483| 0.10527054 | -0.068783 | 0.0116344| -0.000762| 1.48E-05 100 1% 1.976603 | 0.8128499 | 0.048541624| -0.044997 | 0.0071252| -0.000359 | 1.091E-06 Catchment Data Details: Variable | Value Units Exisiting Scenario - SUB3 Area: 1.78 ha fi 0.21 fraction Cio 0.55 fraction Rational Method Summary: Overland flow time (min) 20.60 Pipe flow time (min) Adopted Time of Concentration (tc) (min) 20.6 Duration (hours) 0.3 Freq Factor 0.80 0.85 1.05 1.15 1.20 Duration (hours) 20.60 20.60 20.60 20.60 20.60 Duration (min) 0.34 0.34 0.34 0.34 0.34 Intensity (mm/hr) 70.15, 78.92 142.26 165.46 183.04 Discharge (m°/s) 0.1536 | 0.1837 0.4089 0.5209 | 0.6013
Page 44
SUMMARY OF RESULTS E05 RESULTS % AEP 1 0.52 0.97 1.35 1.64 1.81 1.83 1.86 1.76 1.69 1.59 1.38 1.57 1.86 2 0.40 0.69 1.01 1.28 1.45 1.51 1.55 1.49 1.43 1.34 1.16 1.32 1.55 5 0.30 0.37 0.59 0.78 0.95 1.13 1.13 1.16 1.21 1.12 1.09 1.05 1.21 10 0.24 0.25 0.31 0.44 0.58 0.78 0.84 0.87 0.92 0.88 0.84 0.80 0.92 20 0.20 0.21 0.20 0.21 0.28 0.49 0.60 0.72 0.67 0.67 0.68 0.59 0.72 50 0.15 0.15 0.15 0.15 0.15 0.13 0.17 0.32 0.36 0.36 0.43 0.36 0.43 63.2 0.13 0.13 0.13 0.13 0.13 0.11 0.11 0.17 0.24 0.27 0.33 0.29 0.33 1% CC 0.98 1.68 2.13 2.45 2.57 2.49 2.45 2.29 2.16 2.04 1.77 2.02 2.57 DO5 Results % AEP 1 0.75 1.20 1.51 1.75 1.83 1.89 1.85 1.74 1.65 1.53 1.35 1.55 1.89 2 0.59 0.95 1.22 1.43 1.51 1.58 1.56 1.48 1.40 1.30 1.14 1.31 1.58 5 0.48 0.65 0.86 0.99 1.10 1.22 1.16 1.16 1.20 1.11 1.08 1.04 1.22 10 0.39 0.48 0.60 0.70 0.78 0.90 0.89 0.90 0.94 0.89 0.84 0.80 0.94 20 0.33 0.40 0.43 0.47 0.52 0.61 0.67 0.73 0.67 0.71 0.69 0.60 0.73 50 0.23 0.28 0.31 0.32 0.32 0.29 0.31 0.38 0.38 0.40 0.43 0.36 0.43 63.2 0.20 0.24 0.27 0.28 0.28 0.26 0.25 0.25 0.28 0.30 0.34 0.29 0.34 1% CC 1.17 1.80 2.19 2.48 2.52 2.52 2.42 2.25 2.10 1.96 1.73 1.98 2.52 Mitigated Results NTA Max WSL (m) 1 0.59 0.93 1.27 1.53 1.66 1.82 1.77 1.68 1.58 1.43 1.28 1.46 1.82 0.39 2 0.49 0.72 0.96 1.19 1.30 1.49 1.46 1.40 1.29 1.15 1.04 1.21 1.49 0.39 5 0.42 0.53 0.68 0.79 0.87 1.02 1.04 1.00 1.03 1.00 0.97 0.92 1.04 0.39 10 0.37 0.42 0.51 0.60 0.67 0.78 0.78 0.78 0.82 0.80 0.75 0.72 0.82 0.39 20 0.33 0.38 0.40 0.43 0.48 0.57 0.62 0.65 0.62 0.66 0.64 0.58 0.66 0.20 50 0.23 0.29 0.31 0.32 0.32 0.29 0.31 0.37 0.38 0.40 0.43 0.36 0.43 0.04 63.2 0.20 0.25 0.27 0.28 0.28 0.26 0.25 0.25 0.28 0.30 0.34 0.29 0.34 0.02 1% CC 0.91 1.53 1.96 2.28 2.38 2.46 2.35 2.20 2.06 1.89 1.69 1.92 2.46 0.78 1% Blocked 0.81 1% CC Blocked 0.89 Difference 1% AEP 0.07 -0.04 -0.08 -0.11 -0.15 -0.01 -0.09 -0.08 -0.11 -0.16 -0.10 -0.11 0.07 1% AEP CC -0.07 -0.15 -0.17 -0.17 -0.18 -0.03 -0.09 -0.09 -0.11 -0.15 -0.08 -0.10 -0.03
Page 45
Comment#1/33 Pavilion Street
Comment#2] Existing (E05) IMPORT SAVE & RUN
Comment#3/ARR19 IL & CL CLEAR_ALL BROWSE
RESULTS_ONLY BROWSE
| DEFAULTS ] BROWSE
Lag Parameter (C) 1.6 Name 5% AEP 2% AEP 1% AEP 1% AEP CC Area BROWSE
Stream Lag Factor] 1 EX2 0.300 0.618 0.782 1.032 1.960
Calculation Timestep 1)}mins EX1 0.049 0.093 0.116 0.152 0.287
Initial Loss| 35/mm
Continuing Loss Rate} 2.4|mm/hr How TIPS PomonalFD
TOPOLOGY TIPS ARR
Subarea Name Connects_to Area_ha Imp_% Storm# AEP (ARI) Dura_mins | Subarea
1/EX2 SUB3 0.782 50 1 i 10
2/Ex1 SUB1 0.116 50 2 zl 15
3/SUB3 SUB4 2.085 21 3 Hl 20 Diverts to Sub
4|SUB1 SUB2 2.079 11 4 Hl 25 Crest Elev [m]
5|SUB2 SUB4 1.354 5 5 Hl 30 Length [m]
6|SUB4 SINK 0.511 5 6 Hl 45 Weir Coeff
7 7 1 60 D_Fact
8 8 1 90 Directed to
9 9 1 120 Delay [mins]
10 10 Hl 180
11 11 Hl 270
12 12 Hl 360
SINK
1 2 3 4 5 6 7 8 9 10
Structure Averages 1 AEP 10 mins 1 AEP 15 mins 1AEP 20 mins 1 AEP 25 mins 1 AEP 30 mir1 AEP 45 mins 1 AEP 60 mins 1AEP90 mins 1 AEP 120 m1 AEP 180 mins
EX2 0.27 0.3048 0.2993 0.3166 0.3312 0.3016 0.279 0.2517 0.2426 0.2134
Ex1 0.0441 0.0531 0.0511 0.0538 0.0546 0.0513 0.0456 0.0408 0.0388 0.0326
SUB3 0.4518 0.6537 0.7599 0.8396 0.9097 0.8312 0.8307 0.7793 0.7476 0.7033
SUB1 0.2051 0.4051 0.5189 0.5914 0.6634 0.6097 0.6211 0.5851 0.5643 0.5303
SUB2 0.1797 0.4291 0.6427 0.8053 0.9036 0.9166 0.9357 0.8906 0.858 0.8132
SUB4 0.5228 0.9721 1.3489 1.6429 1.8072 1.8262 1.8554 1.7579 = 1.6859 1.591
Structure_averages
Inflow Peak [m3/s]
Outflow Peak [m3/s]
Inflow Volume [m3]
Max Vol Stored [m3]
Max Water Elev [m]
RESULTS
10 15 20 25 30 45 60 90 120 180
1 0.5228 0.9721 1.3489 1.6429 1.8072 1.8262 1.8554 1.7579 = 1.6859 1.591
2 0.3953 0.6875 1.0064 1.278 1.4451 1.5126 1.5531 1.4897 1.4294 1.3434
5 0.3043 0.3675 0.5886 0.7792 0.9472 1.1269 1.1333 1.1632 1.2074 1.1232
10 0.2421 0.2465 0.3091 0.4414 0.5812 0.7763 0.8429 0.8745 0.9193 0.8814
20 0.2025 0.2085 0.2032 0.2148 0.2814 0.4883 0.5985 0.7204 0.6667 0.6693
50 0.1451 0.1518 0.1479 0.1485 0.1463 0.1296 0.1656 0.3238 0.3561 0.3639
63.2 0.127 0.1332 0.1302 0.1307 0.1287 0.1143 0.1093 0.1702 = 0.2431 0.2693
1% CC 0.9809 1.68 2.1314 2.4494 2.5659 2.4916 2.4494 2.293 2.1621 2.0411
WBNM_Run: C:\Projects (C drive)\33 Pavilion\001\wbnm2019_w64.exe
ARR2019 Gauge C:\Projects (C drive)\33 Pavilion\004 Layout Updates\PomonalFD.\ Note this must be in same location as runfile
ARR_Catchment: QLD_ARR_Datahub.txt
ARR_Patterns: QLD_ECnorth_Increments.csv
Note this must be in same location as runfile
Note this must be in same location as runfile
LAST_BUILD: C:\Projects (C drive)\33 Pavilion\004 Layout Updates\runfiles\005.wbn
11
1 AEP 270 mins
0.1827
0.0276
0.6063
0.4565
0.7026
1.3767
270
1.3767
1.1645
1.0876
0.8425
0.6807
0.4278
0.3317
1.7709
12
1 AEP 360 mins
0.2083
0.0314
0.6874
0.5166
0.7987
1.569
360
1.569
1.3229
1.0507
0.8005
0.5905
0.3565
0.2863
2.0186
Delay [mins]
MAX
Diverts to Sub
Invert [m]
No. Barrels
Ent. Type
Dia/(Width)[mm]
(Height)[mm]
Disch-Factor
Directed to
%Per to LS
%lmp to LS
Pipe#1 Pipe#2. Pipe#3 Elevation_m Storage_m3
1.8554
1.5531
1.2074
0.9193
0.7204
0.4278
0.3317
2.5659
Page 46
Comment#1]33 Pavilion Street
Commenti#2|Developed (DOS) IMPORT SAVE & RUN
Comment#3JARR19 IL & CL CLEAR_ALL BROWSE WBNM_Run: C:\Projects (C drive)\33 Pavilion\001\wbnm2019_w64.exe
RESULTS_ONLY BROWSE ARR2019 Gauge C:\Projects (C drive)\33 Pavilion\004 Layout Updates\PomonalFD.csv Note this must be in same location as runfile
wor - [eeraurs_] BROWSE ARR_Catchment: QLD_ARR_Datahub.txt Note this must be in same location as runfile
Lag Parameter (C) 1.6 Name 5% AEP 2% AEP 1% AEP 1% AEP CC Area BROWSE ARR_Patterns: QLD_ECnorth_Increments.csv Note this must be in same location as runfile
Stream Lag Factor| 1 [pa | __ 0.300 0.618 | 0.782 [__ 1.032 1.960 | LAST_BUILD: C:\Projects (C drive)\33 Pavilion\004 Layout Updates\runfiles\004.wbn
Calculation Timestep| 1|mins | EXi | _(0.049 0.093 | 0.116 [0.182 0.287 |
Initial Loss| 35|mm
Continuing Loss Rate| 2.4|mm/hr He S PomonalFD
T ARR
‘Subarea ‘Connects_to_Area_ha ‘Stormit "AEP (ARI) ‘Dura_mins ea TW D-Fact Type %Pertols _ %imptols |
1 1 1 10
2/Ex1 2 1 15 R Weir#1 Weir#2 a Pipe#1 Pipe#2 Pipe#3
3/SUB3 3 1 20 Diverts to Sub Diverts to Sub
4/suB1 4 1 25 Crest Elev [m] Invert [m]
5|SUB2 5 1 30 Length [m] No. Barrels
6|SUB4 6 1 45 Weir Coeff Ent. Type
7 7 1 60 D_Fact_ Dia/(Width)[mm]
8 8 1 90 Directed to (Height)[mm]
9 9 1 120 Delay [mins] Disch-Factor,
10) 10] 1 180 Directed to}
1 11 1 270 Delay [mins]
12| 12] 1 360
SINK
1 2 3 4 5 6 7 8 9 10 a. 12
Structure Averages AEP 10 mins AEP 15 mins 1 AEP 20 mins 1AEP 25 mins 1 AEP 30 mins 1 AEP 45 mins AEP 60 mins 1AEP90 mins 1AEP 1201 AEP 180 mins 1 AEP 270 mins 1 AEP 360 mins
EX2 0.27 0.3048, 0.2993, 0.3166 0.3312 0.3016 0.279 0.2517 0.2426 0.2134 0.1827 0.2083,
Ex 0.0441 0.0531 0.0511 0.0538 0.0546 0.0513 0.0456 0.0408 0.0388 0.0326 0.0276 0.0314
‘SUB3 0.7164 0.8185 0.8424 0.8913 0.9315 0.8415 0.8095, 0.7441 0.7137 0.6627 0.5694 0.6485,
SUB1 1.092 1.3032 1.3911 1.4863 1.5422 1.4207 1.3868 1.2979 1.2349 1.1662 1.0093 1.1442
SUB2 0.837 1.2355 1.4905 1.6897 1.7317 1714 1.6838 1.5783 1.4912 1.404 1.2272 1.3992
SUB4 0.745 1.1968 1.5099 1.7534 1.8313 1.8869 1.8492 1.7418 1.6464 1.533 1.3517 1.5457
Structure_averages
Inflow Peak [m3/s]
Outflow Peak [m3/s]
Inflow Volume [m3]
Max Vol Stored (m3)
Max Water Elev [m]
DOS Results
10 15 20 25 30 45 60 90 120 180 270 360 MAX
1 0.745 1.1968 1.5099 1.7534 1.8313 1.8869 1.8492 1.7418 1.6464 1.533 1.3517 1.5457 1.8869
2 0.593 0.95 1.2161 1.4339 1.5112 1581 1.5628 1.482 1.4027 1.3002 1.1415 1.3089 1.581
5 0.4773 0.6458, 0.8553, 0.9881 1.0999 1.2208 1.1616 1.1648 1.1994 1.1141 1.075 1.0379 1.2208
10 0.3932 0.4807 0.5952 0.6954 0.7837 0.9013 0.8893 0.9028 0.9377 0.8856 0.8442 0.8049 0.9377
20 0.3253 0.4016, 0.4345, 0.4689 0.5236 0.6083 0.671 0.727 0.6702 0.7067 0.6887 0.5958 0.727
50 0.226 0.2833 0.3083, 0.3162 0.3178 0.2932 0.3067 0.375, 0.3786 0.3975, 0.4338, 0.3646 0.4338
63.2 0.1953 0.2446, 0.2687 0.2769 0.2779 0.2568 0.2471 0.2549 0.2779 0.3044 0.3436, 0.2948 0.3436
1% CC 1.1724 1.7951 2.187 2.4777 2.5173 2.5238, 2.4187 2.2471 2.1007 1.9562 1.728 1.9757 2.5238
Page 47
Comment#1/33 Pavilion Street
Comment#2|Developed (D05) IMPORT. SAVE & RUN
Comment#3/ARR19 IL & CL CLEAR_ALL BROWSE
RESULTS_ONLY BROWSE
| DEFAULTS ] BROWSE
Lag Parameter (C) 1.6 Name 5% AEP 2% AEP 1% AEP 1% AEP CC Area BROWSE
Stream Lag Factor] 1 EX2 0.300 0.618 0.782 1.032 1.960
Calculation Timestep 1)}mins EX1 0.049 0.093 0.116 0.152 0.287
Initial Loss| 35/mm
Continuing Loss Rate} 2.4|mm/hr How TIPS PomonalFD
TOPOLOGY TIPS ARR
Subarea Name Connects_to Area_ha Imp_% Storm# AEP (ARI) Dura_mins | Subarea
1/EX2 SUB3 0.782 50 1 i 10
2/Ex1 SUB1 0.116 50 2 zl 15
3/SUB3 SUB1 1.78 50 3 Hl 20 Diverts to Sub
4|SUB1 SUB2 2.079 50 4 Hl 25 Crest Elev [m]
5|SUB2 SUB4 1.354 5 5 Hl 30 Length [m]
6|SUB4 SINK 0.819 6.5 6 Hl 45 Weir Coeff
7 7 1 60 D_Fact
8 8 1 90 Directed to
9 9 1 120 Delay [mins]
10 10 Hl 180
11 11 Hl 270
12 12 Hl 360
SINK
1 2 3 4 5 6 7 8 9 10
Structure Averages 1 AEP 10 mins 1 AEP 15 mins 1AEP 20 mins 1 AEP 25 mins 1 AEP 30 mins 1 AEP 45 mins 1AEP 60 mins 1AEP90 mins 1 AEP 120111 AEP 180 mins
EX2 0.27 0.3048 0.2993 0.3166 0.3312 0.3016 0.279 0.2517 0.2426 0.2134
Ex1 0.0441 0.0531 0.0511 0.0538 0.0546 0.0513 0.0456 0.0408 0.0388 0.0326
SUB3 0.7164 0.8185 0.8424 0.8913 0.9315 0.8415 0.8095 0.7441 = -0.7137 0.6627
SUB1 1.092 1.3032 1.3911 1.4863 1.5422 1.4207 1.3868 1.2979 1.2349 1.1662
SUB2 0.837 1.2355 1.4905 1.6897 1.7317 1.714 1.6838 1.5783 1.4912 1.404
SUB4 0.745 1.1968 1.5099 1.7534 1.8313 1.8869 1.8492 1.7418 1.6464 1.533
Structure_averages
Inflow Peak [m3/s]
Outflow Peak [m3/s]
Inflow Volume [m3]
Max Vol Stored [m3]
Max Water Elev [m]
DOS Results
10 15 20 25 30 45 60 90 120 180
1 0.745 1.1968 1.5099 1.7534 1.8313 1.8869 1.8492 1.7418 1.6464 1.533
2 0.593 0.95 1.2161 1.4339 1.5112 1.581 1.5628 1.482 1.4027 1.3002
5 0.4773 0.6458 0.8553 0.9881 1.0999 1.2208 1.1616 1.1648 = 1.1994 1.1141
10 0.3932 0.4807 0.5952 0.6954 0.7837 0.9013 0.8893 0.9028 0.9377 0.8856
20 0.3253 0.4016 0.4345 0.4689 0.5236 0.6083 0.671 0.727 ~—-0.6702 0.7067
50 0.226 0.2833 0.3083 0.3162 0.3178 0.2932 0.3067 0.375 0.3786 0.3975
63.2 0.1953 0.2446 0.2687 0.2769 0.2779 0.2568 0.2471 0.2549 0.2779 0.3044
1% CC 1.1724 1.7951 2.187 2.4777 2.5173 2.5238 2.4187 2.2471 2.1007 1.9562
WBNM_Run: C:\Projects (C drive)\33 Pavilion\001\wbnm2019_w64.exe
ARR2019 Gauge C:\Projects (C drive)\33 Pavilion\004 Layout Updates\PomonalFD.csv Note this must be in same location as runfile
ARR_Catchment: QLD_ARR_Datahub.txt
ARR_Patterns: QLD_ECnorth_Increments.csv
LAST_BUILD: C:\Projects (C drive)\33 Pavilion\004 Layout Updates\runfiles\004.wbn
11
1 AEP 270 mins
0.1827
0.0276
0.5694
1.0093
1.2272
1.3517
270
1.3517
1.1415
1.075
0.8442
0.6887
0.4338
0.3436
1.728
12
1 AEP 360 mins
0.2083
0.0314
0.6485
1.1442
1.3992
1.5457
360 MAX
1.5457
1.3089
1.0379
0.8049
0.5958
0.3646
0.2948
1.9757
Diverts to Sub
Invert [m]
No. Barrels
Ent. Type
Dia/(Width)[mm]
(Height)[mm]
Disch-Factor
Directed to
Delay [mins]
Note this must be in same location as runfile
Note this must be in same location as runfile
%Per to LS
%lmp to LS
Pipe#1. Pipe#2. Pipe#3 Elevation_m Storage_m3
1.8869
1.581
1.2208
0.9377
0.727
0.4338
0.3436
2.5238
Page 48
Comment#1]33 Pavilion Street Commenti#2|Mitigated (M05) IMPORT SAVE & RUN Comment#3]ARR19 IL & CL CLEAR_ALL BROWSE WBNM_Run: C:\Projects (C drive)\33 Pavilion\001\wbnm2019_w64.exe RESULTS_ONLY BROWSE ARR2019 Gauge C:\Projects (C drive)\33 Pavilion\004 Layout Updates\PomonalFD.csv Note this must be in same location as runfile [[veraucs_] BROWSE ARR_Catchment: QLD_ARR_Datahub.txt Note this must be in same location as runfile Lag Parameter (C) 1.6 Name 5% AEP 2% AEP 1% AEP 1% AEP CC Area BROWSE ARR_Patterns: QLD_ECnorth_Increments.csv Note this must be in same location as runfile Stream Lag Factor] 1 EX2 0.300 0.618 0.782 1.032 1.960 LAST_BUILD: C:\Projects (C drive)\33 Pavilion\004 Layout Updates\runfiles\005.wbn Calculation Timestep| 1}mins EX1 0.049 0.093 0.116 0.152 0.287 Initial Loss} 35/mm Continuing Loss Rate| 2.4|mm/hr He TIPS PomonalFD TOPOLOGY | TIPS aE Name Connects to Area_ha Imp_% Storm# ‘AEP (ARI) = IWL D-Fact Type %PertolS %lmp to LS A/EX2 SUB3 0.782 50 1 1 SUB1 0 1 OUTLET 2/Ex1 SUB1 0.116 50 2 1 Weir Weirl2 a Pipef1 Pipe#2 Pipe#3 Elevation_m Storage_m3 RL 3|SUB3. SUB1 1.78 50 3 1 Diverts to Sub SUB2 Diverts to Sub SUB2 SUB2 -0.9 0 84.4 4\SUB1 ISUB2 2.079 50 4 1 Crest Elev [m] 0.6 Invert [m] 0 -0.9 0 0 85.3 5|SUB2 ISUB4 1.354 5 5 1 Length [m] 8 No. Barrels 0 0 0.3 116.7 85.6 6|SUB4 SINK 0.819 6.5 6 1 Weir Coeff 1.6 Ent. Type 1 1 0.6 268 85.9 7 7 1 D_Fact 1 Dia/(Width)[mm] 450 450 0.9 458.1 86.2 8 8 1 Directed to TOP (Height)[mm] 0.97 508.3 86.27 9 9 1 120 Delay [mins] 0 Disch-Factor| 1 1 10 10 1 180 Directed to TOP TOP 11 11 1 270 Delay [mins] 0 0 12 12 1 360 SINK Elevation _|Freeboard RL 1% WSL 0.809 0.162 86.11 1%CC WSL 0.781 0.189 86.08 196Blocked Osi 0.159 86.11 i 2 3 4 5 6 7 8 9 10 11 12 1%CC Blocked 0.892 0.078 86.19 Structure Averages 1AEP10mins © 1AEP15 mins 1AEP20mins 1AEP 25 mins 1 AEP 30 mins 1 AEP 45 mins 1 AEP 60 mins 1AEP90 mins 1AEP 12011 AEP 180 mins 1 AEP 270 mins 1 AEP 360 mins Bund 0.970 86.27 EX2 0.27 0.3048 0.2993 0.3166 0.3312 0.3016 0.279 0.2517 0.2426 0.2134 0.1827 0.2083 Ext 0.0441 0.0531 0.0511 0.0538 0.0546 0.0513 0.0456 0.0408 0.0388 0.0326 0.0276 0.0314 SUB3 0.7164 0.8185 0.8424 0.8913 0.9315 0.8415 0.8095 0.7441 0.7137 0.6627 0.5694 0.6485 SUB1 0.8886 1.1944 1.3166 1.4336 1.4633 1.394 1.3601 1.2745 1.205 1.137 0.9905 1.1242 SUB2 0.5879 1.0481 1.3538 1.5811 1.6475 1.6819 1.651 1.552 1.4668 1.3679 1.2047 1.3771 SUB4 0.5163 0.9976 1.352 1.6183 1.7324 1.852 1.8026 1.7118 1.6168 1.4976 1.3303 1.5224 Structure_averages Inflow Peak [m3/s] 1.092 1.3032 1.3911 1.4863 1.5422 1.4207 1.3868 1.2979 1.2349 1.1662 1.0093 1.1442 Outflow Peak [m3/s] 0.8886 1.1944 1.3166 1.4336 1.4633 1.394 1.3601 1.2745 1.205 1.137 0.9905 1.1242 Inflow Volume [m3] 974.8 1461.9 1843.3 2154 2421.1 3067.7 3573.4 4379.9 5071 6209.9 7616.5 8826.2 Max Vol Stored [m3] 348.3 375.8 386.9 397.3 400.2 393.9 390.7 383.1 376.7 370.8 357.4 369.5 Max Water Elev [m] 0.7268 0.7702 0.7876 0.8045 0.8085 0.7989 0.794 0.7815 0.7719 0.762 0.7411 0.7603 Mitigated Results EVENT (% AEP) 10 15 20 25 30 45 60 90 120 180 270 360 MAX Max Water Elev [m] 1 0.5904 0.9308 1.2719 1.5347 1.661 1.8194 1.7702 1.6777 1.5808 1.4287 1.2779 1.4594 1.8194 0.8085 2 0.4927 0.7204 0.9557 1.1904 1.2975 1.4943 1.4609 1.4035 1.2873 1.153 1.0368 1.2106 1.4943 5 0.4242 0.532 0.6751 0.7879 0.8742 1.0227 1.0368 1.0047 1.0349 0.9998 0.9706 0.9206 1.0368 10 0.3731 0.4227 0.5087 0.5973 0.666 0.7812 0.7826 0.7824 0.8179 0.7971 0.7541 0.7198 0.8179 20 0.3254 0.3764 0.3962 0.4331 0.4849 0.5681 0.6179 0.6457 0.6202 0.6558 0.6367 0.575 0.6558 0.201 50 0.2318 0.2862 0.3091 0.3157 0.3169 0.2944 0.3074 0.3716 0.3765 0.3975 0.4309 0.3646 0.4309 0.041 63.2 0.2006 0.2484 0.2713 0.2781 0.2789 0.2576 0.2476 0.2549 0.2781 0.3044 0.3436 0.2948 0.3436 0.015 1% CC 0.9108 1.5348 1.9647 2.2772 2.3841 2.4626 2.3546 2.1994 2.0553 1.8887 1.6907 1.919 2.4626 0.7806 1% Blocked 0.811 1% CC Blocked 0.892 FSL EDD
Page 49
Existing Flood Map 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona
Page 50
LEGEND i" Site DCDB entities Noosa_2015_Lidar Flood Depth (m) . 1.5 0 DATE: 03/10/2023 CONSULTANT: CREATED BY: L. GILLIS J REVISION: B PAGESIZE: A3_ SCALE; /*!-500 Colliers STATUS: ISSUE COORDINATE SYSTEM: GDA 94 / MGA ZONE 56 PROJECT TITLE: 33 PAVILION STREET, POMONA - FLOOD INVESTIGATION PROJECTNO: = 23-0167 BIEN: FIGURE TITLE: FLOOD DEPTH MAP - EXISTING (E05) - 1% (2100) AEP FIGURE NO: APPENDIX C © PeakUrban
Page 51
Proposed Flood Map 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona
Page 52
LEGEND Flood depth (m) 1.5 DATE: 04/10/2023 CREATED BY: L. GILLIS REVISION: B PAGE SIZE: A3 SCALE: STATUS: ISSUE COORDINATE SYSTEM: GDA 94 / MGA ZONE 56 1:1,500 PROJECT TITLE: 33 PAVILION STREET, POMONA - FLOOD INVESTIGATION PROJECT NO: 23-0167 FIGURE TITLE; FLOOD DEPTH MAP - PROPOSED (P06) - 1% (2100) AEP FIGURE NO: APPENDIX D
Page 53
Appendix E Flood Afflux Map 23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona
Page 54
LEGEND i" Site Layout — Lot boundaries --- Easement — Vegetation Covenant Noosa_2015_Lidar — 1 — 500 Afflux (m) Wl <-0.1 HM -0.075 to -0.1 MM -0.05 to -0.075 -0.025 to -0.05 -0.01 to -0.025 -0.025 -0.01 to 0.01 0.01 to 0.025 0.025 to 0.05 MP) 0.05 to 0.075 HM 0.075 to 0.1 Hl >0.1 !) Was Wet now Dry MN Was Dry now Wet ele SMa Lore 7 a Ly BATE: 04/10/2023 CONSULTANT: CREATED BY: _L, GILLIS NN j REVISION: B PAGE SIZE: A3 SCALE; !*!500 N Colliers STATUS: ISSUE COORDINATE SYSTEM: GDA 94 / MGA ZONE 56 PROJECT TITLE: 33 PAVILION STREET, POMONA - FLOOD INVESTIGATION PROJEGCNO: 23-0167 CLIENT: FIGURE TITLE: FLOOD AFFLUX MAP - PROPOSED (P06) VS EXISTING (E05) - 1% (2100) AEP FIGURE NO: APPENDDCE
Page 55
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23-0167SMP01-V3 | Stormwater Management Plan | 33 Pavilion Street, Pomona