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Appendix B - Stormwater Management Report
STORMWATER MANAGEMENT REPORT 58 on RP32777 25 Tulip Street, Cooroy [OCR of page images] NT REPORT pA : Ee S 7 MANAGEME een. aee Per wl e
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Contents 1. INTRODUCTION .............................................................................................................. 4 2. SITE DETAILS ................................................................................................................... 4 2.1. Existing Site Description and Drainage Regime ................................................................. 4 2.2. Proposed Development Drainage Regime .......................................................................... 6 3. STORMWATER CHARACTERISTCS ............................................................................... 6 3.1. Comparison of Pre/Post Development and Quantity.......................................................... 6 3.2. Quality ............................................................................................................................ 7 3.2.1. Construction Phase....................................................................................................... 7 3.2.2. Operational Phase ........................................................................................................ 7 4. Conclusion and Recommendations ....................................................................................... 7 Appendix A –Proposed Development Concept Plans ..................................................................... 8
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Document Control
Report Title Stormwater Management Report
Client Ashley Trompf
Client Contact Ashley Trompf Client Reference 25 Tulip St, Cooroy
Verifier
Rev Date Revision details/status Author Reviewer Approver
(if required)
0 5 Nov 2025 Initial Version J.Bauleka J.Bauleka J.Bauleka
1 10 Nov 2025 Issued for Use J.Bauleka J.Bauleka
Current revision 1
Approval
Author signature Approver signature
Name J.Bauleka Name J.Bauleka
RPEQ: 20693
Title Civil Engineer Title Civil Engineer
Auxilium Consulting Pty Ltd
ABN 84 639 195 092
9 Ginger Bell Ave
Bli Bli, Qld 4560
Australia
M +61 423 415 419
E [email protected]
Page 4
1. INTRODUCTION Auxilium Consulting Pty Ltd (Auxilium) has been engaged to prepare a Stormwater Management Report to accompany a development application for a residential subdivision located at 25 Tulip Street, Cooroy. This report investigates the stormwater management considerations for the existing and proposed development site and assesses how the run-off from the site is to be managed in accordance with Noosa Council requirements for stormwater drainage. 2. SITE DETAILS 2.1. Existing Site Description and Drainage Regime The existing Site is located at 25 Tulip Street, described as Lot 58 on Plan RP32777, and contains an existing dwelling and shed with an area of 1,529 m2. The Site is a residential setting with a large proportion of permeable areas. FIGURE 1 SITE LOCALITY PLAN (NOOSA COUNCIL INTRAMAPS, 2025) The Site slopes away from the road frontage towards the rear of the property. An unmapped channel conveys flows to the east and eventually into the Lake Macdonald catchment system. Roof run-off from the existing dwelling is discharged to the rear of the Site as overland flows to the existing channel. Road surface flows are excluded from the Site’s catchment with the kerb and channel and crossover.
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FIGURE 2 SITE FRONTAGE (GOOGLE STREETVIEW, AUG 2023) FIGURE 3 EXISTING ROOF DRAINAGE TO OVERLAND FLOWS TO REAR OF THE SITE (NOV 2025)
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2.2. Proposed Development Drainage Regime
The proposed subdivision results in the creation of one additional rear lot with an increase of
impermeable surfaces through roof areas and driveway. It is expected that stormwater quantities will
increase as a result of these impermeable areas with attenuation via rainwater tanks proposed.
Existing surface flows from upstream adjacent properties will remain unchanged. The existing
drainage regime of discharging to the Lawful Point of Discharge (LPOD) at the northeastern
boundary (unmapped channel) is maintained in the developed state.
The roof and allotment drainage system for the proposed site shall be designed to comply with:
1. Noosa Council Planning Scheme SC6.7.6 Stormwater Management and 9.4.8 Water Quality
and Drainage Code
2. The Queensland Urban Drainage Manual (QUDM); and
3. AS/NZS 3500.3:2015 - Plumbing and Drainage Part 3: Stormwater Drainage.
Refer to Appendix A Proposed Development Concept Plan for the proposed stormwater drainage layout
plan illustrating the concept described above.
3. STORMWATER CHARACTERISTCS
3.1. Comparison of Pre/Post Development and Quantity
The development proposes to increase the impervious area of the site by 229m2 for the additional
dwelling and allowance for the driveway surface – note this is an approximation to provide allowance
for siting the actual driveway layout.
Pre and post discharge rates have been calculated using DRAINS software to evaluate the effect of
the development. Attenuation of post-development flows have achieved by modelling each dwelling
having a 3kL rainwater tank.
Utilising the modelling methods of ARR2019, parameters from the ARR Data Hub for the site
location, and rainfall Intensity Frequency Distribution data from the Australian Bureau of
Meteorology have been implemented into the DRAINS model to determine the mean peak discharge
rates from the storm events. This is presented in Table 1 below.
QPROPOSED M³/S (WITH
% AEP EVENT Q EXISTING M³/S QPROPOSED M³/S (NO ATTENUATION) QCHANGE M³/S
ATTENUATION)
63.2 0.020 0.023 0.020 0.000
39.3 0.030 0.032 0.027 -0.003
18.1 0.043 0.046 0.041 -0.002
10 0.051 0.056 0.049 -0.002
5 0.063 0.066 0.059 -0.004
2 0.072 0.074 0.067 -0.005
1 0.082 0.085 0.077 -0.005
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TABLE 1 PRE AND POST COMPARISON OF PEAK DISCHARGE RATES
The effect of the rainwater tanks is effective attenuation of discharge rates to maintain existing rates
or even a reduction of the pre-development rates.
Controlled flows from the outlets of these tanks will be discharged to the LPOD via a level spreader
device to maintain the pre-development drainage regime.
3.2. Quality
3.2.1.Construction Phase
To fulfill the General Environmental Duty, a person “…must not carry out any activity that causes or is
likely to cause environmental harm, unless measures to prevent or minimise the harm have been taken…”. It is
necessary to manage and mitigate these impacts through best practise erosion and sediment controls.
Due to the development area being less than 2,500 m2 the construction impacts will be managed
using the principles aligned with the desired outcomes of Appendix 2 of State Planning Policy (SPP).
A site-specific erosion and sediment control plan must be prepared and submitted as part of the
Operational Works approval.
3.2.2.Operational Phase
This development consists of an additional dwelling as part of the subdivision and is consistent in
character with the existing residential dwelling and environment. As the development proposal is not
considered to significantly alter the potential for pollutant generation, stormwater quality treatment
processes are not proposed for the development.
4. Conclusion and Recommendations
This Stormwater Management Report demonstrates how the stormwater run-off from the site is to be
managed to comply with the relevant requirements and mitigate adverse impacts to the downstream
catchment.
The proposed site stormwater run-off maintains the existing drainage regime. The existing
surface runoff from the upstream properties remains unchanged compared to the existing state.
Pre and post development modelling of the resultant peak flows has been carried out, with
attenuation using two 3kL rainwater tanks identified to mitigate peak flows. Outlets from the
tanks discharge via a level spreader device to the LPOD, to maintain the pre-development
drainage regime.
A site-specific erosion and sediment control plan is to be prepared and submitted with the
Operational Works approval to mitigate impacts to the receiving catchments and fulfil the
general environmental duty of care and Appendix 2 of the SPP.
The proposed development is not considered to significantly alter the pollutant generating
potential of the site; therefore, stormwater quality treatment processes are not proposed for the
development.
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Appendix A –Proposed Development Concept Plans [OCR of page images] Appendix A —Proposed Development Concept Plans
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Last Modified :— Oct 27, 2025 - 2:02pm
LEGEND
ADJACENT BOUNDARY CATCHMENT TABLE
EXISTING ELECTRICAL
EXISTING DRAINAGE CATCHMENT | AREA (ha) | IMPERVIOUS ( % )
EXISTING KERB PRE 01 0.153 16.00
EXISTING MINOR CONTOUR
EXISTING MAJOR CONTOUR
=a =o CATCHMENT BOUNDARY
trop C) LEGAL POINT OF DISCHARGE
F Associated Job N Survey Dat CLIENT COUNCIL
; ssocianee es ion veo Scales J. & C. TROMPF 25 TULIP STREET, COOROY QLD 4563
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8 Height T py 66,329 Scale 1150 @Al © ABN 84 639 195 092 NAN PLAN STATUS Job No] =
A [ISSUE FOR REVEW 23.10.25 Datum . PIKKI ST JARO BALLEKA SIGNATURE ISSUE FOR USE Contract_No. -
- Signatory: - RPEQ Full Name, Eng. Area and RPEQ No. or Survey | SURVEYPLAN ] Dimensions shown in metres MAROOCHYDORE BC, QLD 4558 RPEQ #20695 DRAWN DESIGNED DATE i
Revisions/Descriptions = Full Name and Position Title Date Books | __%% __| except where shown otherwise +61 423 415 419 cPEng TN MN 23.10.25 Drawing No.| C900 [A
COTES [email protected].AU__} DATE:23.10.25 WU. Series Number 1 of 4
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Emt for Acsess & Services Concrete
STREET
Deck
806m²
725m²
Shed
2
Step
1
EXISTING BUILDING
TULIP
DECK
Slab
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Emt for Acsess & Services Concrete
STREET
Deck
806m²
725m²
Shed
2
Step
1
EXISTING BUILDING
TULIP
DECK
Slab
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XREFS :— X—BASE.dwg ; X-SURVEY.dwg ALL ROOFWATER TO DISCHARGE OVER TANK INLET MESH PROTECTION COVER OVER INLET INTO TANK Last Modified :— Oct 27, 2025 - 2:02pm CAD FILES J [email protected] DATE:23.10.25 poo n---- nnn H \ PROPOSED #100 ORIFICE 2 | | | AT 1.82m OF TANK PROPOSED $50 ORIFICE 1 DISCHARGE TO PROPOSED AT BASE OF TANK STORMWATER DRAINAGE t—| SYSTEM (REFER PLAN) pase Ut é at z x a at 4 a , 4 4 ; o 4 ¢ a 4 a 24 < ¢ a 4 4 4 7 9 q “ < STORMWATER DETENTION TANK DETAIL-3kL F Associated Job Nos] Survey Data Scales CLIENT 25 TULIP STREET, COOROY QLD 4563 COUNCIL E tore J. & C. TROMPF ; AHD AUXILIUM ° a 3 Detum aan TANK DETAIL NOOSA SHIRE COUNCIL C Auxiliary Drg Nos] Horiz. | MGA2020 | 9 02 Oh 0.6m ASSOCIATED CONSULTANTS Grid ZONEQ6 k ‘ ‘ NAN 8 Height | pr gg. 399 Scale 110 @A1 © ABN 84 639 195 092 BREN PLANNING STATUS Job No] = A [ISSUE FOR REVEW 23.10.25 Datum : PIKK|. ST JARO. BAULEKA SIGNATURE ISSUE FOR USE Contract_No, - a Signatory: - RPEQ Full Name, Eng. Area and RPEQ No. or Survey | SURVEYPLAN | Dimensions shown in metres MAROOCHYDORE BC, QLD 4558 RPEQ #20693 DRAWN DESIGNED DATE i | Revisions/Descriptions = Full Name and Position Title Date Books | yx __ except where shown otherwise +61 423 415 419 cPEng TN MN 23.10.25 Drawing No. C905 7 A VU. Series Number °