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Reference Document - MCU24 0155 (As Published).pdf
NOOSA COUNCIL
REFERENCE DOCUMENT
MCU24/0155 30 JULY 2020
18 Shearwater Street,
Peregian Beach
Stormwater Management Plan
23/04/2025
DCM Building Design
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Page 2
DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
SYNOPSIS
This document presents the Stormwater Management Plan for a small residential dwelling at 18
Shearwater Street, Peregian Beach. This document will report how stormwater runoff from the property
will be managed to minimise environmental impacts and comply with Noosa Councils Regulations.
Disclaimer
RECOR Pty Ltd has prepared this report based on an agreed scope of work and acts in all professional matters as an advisor to
the Client and exercises all reasonable skill and care in the provision of its professional services in a manner consistent with the
level of care and expertise exercised by members of the environmental profession.
Reports are commissioned by and prepared for the exclusive use of the Client. They are subject to and issued in accordance
with the agreement between the Client and RECOR Pty Ltd. RECOR Pty Ltd is not responsible and will not be liable to any other
person or organisation for or in relation to any matter dealt within this Report, or for any loss or damage suffered by any other
person or organisation arising from matters dealt with or conclusions expressed in this report (including without limitation matters
arising from any negligent act or omission of RECOR Pty Ltd or for any loss or damage suffered by any other party relying upon
the matters dealt with or conclusions expressed in this Report). Other parties should not rely upon the report or the accuracy or
completeness of any conclusions and should make their own inquiries and obtain independent advice in relation to such matters.
Except where expressly stated, RECOR Pty Ltd has not verified the validity, accuracy or comprehensiveness of any information
supplied to RECOR Pty Ltd for its reports. Reports prepared by RECOR Pty Ltd cannot be copied or reproduced in whole or part
for any purpose without the prior written agreement of RECOR Pty Ltd.
Where site inspections, testing or fieldwork have taken place, the report is based on the information made available by the client
or their nominees during the visit, visual observations, and any subsequent discussions with regulatory authorities. The validity
and comprehensiveness of supplied information has not been independently verified, and, for the purposes of this report, it is
assumed that the information provided to RECOR Pty Ltd is both complete and accurate. It is further assumed that normal
activities were being undertaken at the site on the day of the site visit(s), unless explicitly stated otherwise.
COPYRIGHT
The concepts and information contained in this document are the property of RECOR Pty Ltd. Use or copying of this document
in whole or in part without the written permission of RECOR Pty Ltd constitutes an infringement of copyright.
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Page 3
Document prepared by:
RECOR Pty Ltd
ABN 89 647 469 707
12/6 Bottlebrush Ave
Noosa Heads, QLD 4567
Australia
T 1300 469 707
E [email protected]
W recor.au
Document Prepared Approved
Revision Description Date
Revision by By
0 Initial draft for internal review A. Young E. Whitmore 24/04/2025
1 FINAL REPORT FOR ISSUE A. Young E. Whitmore 30/04/2025
Approved by: Eoin Whitmore
Address: Level 11 269 Wickham Street Fortitude Valley QLD 4006
Telephone: 0451453640 Website www.recor.au
Email: [email protected]
Signature: RPEQ 34231
The information within this document is and shall remain the property of RECOR.
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
CONTENTS
1 EXECUTIVE SUMMARY .................................................................................................... 5
2 INTRODUCTION ................................................................................................................ 6
2.1 Existing Site Features ......................................................................................................... 6
2.2 Legal Point of Discharge (LPOD) ....................................................................................... 8
2.3 Flooding and Storm Surcharge ........................................................................................... 8
2.4 Soil types ............................................................................................................................ 9
3 CATCHMENT ANALYSIS ................................................................................................. 10
3.1 Rational Method ................................................................................................................ 10
3.1.1 C10 Values for Impervious and Pervious Catchment Areas ............................... 10
3.1.2 Time of Concentration .......................................................................................... 10
3.2 Pre Development .............................................................................................................. 10
3.3 Post Development............................................................................................................. 11
4 COUNCIL REQUIREMENTS FOR ALLOTMENT DRAINAGE ........................................ 13
5 CONCLUSIONS AND RECOMMENDATIONS ................................................................ 14
6 REFERENCES ................................................................................................................. 15
LIST OF TABLES
Table 1: Pre Development Catchment Information ...............................................................................10
Table 2: Pre Development Catchment Discharges Q ...........................................................................11
Table 3: Post Development Catchment Information .............................................................................12
Table 4: Post Development Catchment Discharges Q .........................................................................12
Table 5: Pre-development vs Post-development Comparison..............................................................14
LIST OF FIGURES
Figure 1: Site layout and Impervious Areas ............................................................................................7
Figure 2: View of Site from Shearwater Street ........................................................................................7
Figure 3: Legal Point of Discharge ..........................................................................................................8
Figure 4: Flood Inundation and Storm Tide map ....................................................................................8
Figure 5: Subject Site, Australian Soil Classification ..............................................................................9
Figure 6: Post Development Pervious Area ..........................................................................................11
APPENDICES
APPENDIX 1. – ARCHITECTURAL DRAWINGS
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
1 EXECUTIVE S UMMARY
The subject site at 18 Shearwater Street, Peregian Beach has a small, detached dwelling which is
proposed to be demolished to accommodate the construction of a new private residential dwelling.
The site is located immediately west of Peregian Beach with a buffer between which comprises of
medium dense bushland containing some open drains to convey flows east to the beach which will
act as the legal point of discharge for the subject site in both the existing and developed scenarios.
The catchment for the site is small and largely limited to the area of the allotment itself. Based on a
Rational method analysis of the pre-development and post-development catchments it was found that
there is very little difference between the existing and the proposed catchment runoff due to similar
areas of pervious and impervious surfaces. Therefore, it is not deemed necessary to provide any
method of stormwater runoff collection or detention for the site.
The key reason for this report is to address Noosa Councils concerns over stormwater runoff from the
site as requested as item 15 of the information request (ECM_23440016_v4) and this item has been
addressed in the following report.
It is recommended that the proposed dwellings roof water be conveyed to the existing open drain via
a uPVC roof water pipe and to include an appropriate headwall and scour protection at the outlet.
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
2 INTRODUCTIO N
The subject site, 18 Shearwater Street Peregian Beach, is located immediately east of Peregian
Beach. The site backs onto Lot 5 CP864962 which acts as a buffer between the properties along
Shearwater Street and the beach. It is proposed to demolish the existing house and carport to
construct a new multi storey dwelling. An application for the proposed works (REF: MCU24/0155)
has been submitted to Noosa Council and an information request (ECM_23440016_v4) has been
received. The aim of this report is to address the item 15 of the information request.
Issue - Stormwater
From a site inspection (undertaken by Council Engineering Officers) and the submitted
information, it is not clear how stormwater will be managed, namely the proposed discharge
point.
Information Required
15. Provide a preliminary Stormwater Management Plan for the site, including details of
collection of stormwater runoff from the building and the hardstand areas, and location
and type of proposed stormwater discharge outlet(s).
2.1 Existing Site Features
The existing site is comprised of a small, detached house surrounded by paved area running the
perimeter of the building which includes the driveway, a turn around at the back and a carport. The
total impervious area of the site is approximately 364.5m 2 and includes existing house roof area,
driveway, turnaround, carport and surrounding concrete areas. Figures 1 and 2 below indicate the
site area and impervious area. The site falls from approximately Reduced Level (RL) 8.5m at the
front boundary to approximately RL 5.0m at the rear boundary and has an approximate fall of 11.6%
from front to rear. The existing lot is currently vegetated with some small shrubs and trees and a
turfed area at the rear of the property. The buffer behind the lot at the east is comprised of medium-
dense bushland with little to no Impervious areas. The subject site and land to the east is likely to
have good drainage and a high permeability due to the sandy soil types in the area (refer to section
2.4).
Shearwater street is an asphalt paved road with mountable kerb and channel on the opposite side of
the road to the subject site and has two-way crossfall. The sites frontage side of Shearwater Street
has no kerb, and water is free to flow from the road to the verge and ultimately through the subject
site. The road verge is sparsely turfed with no other vegetation.
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
Figure 1: Site layout and Impervious Areas
Figure 2: View of Site from Shearwater Street
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
2.2 Legal Po int of Discharge (LPOD)
The legal point of discharge for the site is in the land buffer to the east discharging to the existing
stormwater open drain as indicated below in figure 3 from Noosa Councils mapping service.
Figure 3: Legal Point of Discharge
2.3 Flooding an d Storm Surcharge
From Noosa Councils mapping service reflected in Figure 3 below, the subject site is not affected by
any flooding or storm tide inundation. Potential for increased storm surge levels due to climate
change effects has not been included in councils mapping although due to the higher elevations in the
sand dunes between the site and the beach, the site may be protected.
Figure 4: Flood Inundation and Storm Tide map
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
2.4 Soil ty pes
Disclaimer: The below is provided for commentary on the site conditions only, obtained from
Queensland Globe mapping service. Geotechnical advice should always be sought by a suitably
qualified Geotechnical Engineer.
The subject site has an Australian Soil Classification (ASC) of Podosol type soil. Podosol Soils are
typically sand soils with low water-holding capacity and often contain a hard layer known as “Coffee
Rock” (QLD Government 2025)
Because of this the pervious areas of the ground level of the site will be taken to have a high soil
permeability.
Figure 5: Subject Site, Australian Soil Classification
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
3 CATCHME NT ANALYSIS
The existing catchment for the site consists of a half road pavement and verge catchment as the
external component and the internal site as the internal component. Since the external component
area and catchment parameters would remain the same in both pre and post development scenarios,
the catchment analysis has been limited the internal catchment only.
3.1 Rati onal Method
As the site is small, a simple Rational method calculation is suitable to determine the pre and post
development flows.
The Rational method will be used as outlined in the Queensland Urban Drainage Manual (QUDM)
2016 edition, Chapter 4 – Catchment Hydrology.
3.1.1 C10 Values for Impervious and Per vio us Catchm ent Area s
The C10 values for each portion of the impervious and pervious catchment areas have been
calculated separately due to the highly permeable properties of the soil in the area. C10 values have
been calculated as from tables 4.5.1, 4.5.3, and 4.5.4 and will be taken as 0.35 for pervious areas
and 0.9 for impervious areas. These C10 values will be used for both Pre and Post Development
scenarios.
3.1.2 Time of Co ncentr ati on
From section 4.6.5 of QUDM a minimum time of concentration of 5 minutes has been adopted plus
another 1 minute for a total time of concentration of 6 minutes for the catchment.
3.2 Pre Developmen t
As shown in Figure 1 of this report, the total catchment area for the site is 546.5m 2 and the total
impervious area is 350.7m2.
Calculated C10 values and fraction impervious Fi are presented in Table 1 below.
Table 1: Pre Development Catchment Information
CATCHMENT INFORMATION
OVERALL
PERVIOUS IMPERVIOUS
Area(m2) 195.8 364.5
tc 6
Fraction
impervious, fi,
% 35.8 64.2
1
I10 74.8
C10 0.35 0.9 0.70
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
Calculated catchment discharges for events from AEP 1% (ARI 100year) to AEP 63.21% (ARI 1year)
events are shown in Table 2 below.
Table 2: Pre Development Catchment Discharges Q
ARI AEP(%) FY CY Iy
T
DISCHARGE (Q)
(mm/h) m3/s L/s
1 63.21 0.80 0.56 125.0 0.0109 10.88
2 50.00 0.85 0.60 139.6 0.0129 12.91
5 20.00 0.95 0.67 187.2 0.0194 19.35
10 10.00 1.00 0.70 219.6 0.0239 23.90
20 5.00 1.05 0.74 251.2 0.0287 28.70
50 2.00 1.15 0.81 294.4 0.0368 36.84
100 1.00 1.20 0.84 327.4 0.0428 42.75
3.3 Post Deve lopmen t
The soft landscaping pervious areas of the proposed allotment configuration are shown below in
Figure 6 below, the total catchment area for the site is 546.5m2 and the total pervious area is 272m2.
Figure 6: Post Development Pervious Area
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
Further to the area of pervious surface on the sites natural ground level, the proposed post
development catchment also includes an area of approximately 75m2 of rooftop garden bed. The C10
value for this area has been calculated as 0.7 to allow for a medium permeability soil for the garden
bed. It is assumed that the garden bed will become saturated faster than the natural sandy soils and
bypass flows to the LPOD faster via the roof water drainage networks and therefore the higher C10
value is justified which will increase the overall C10 value for the post developed site.
Calculated C10 values and fraction impervious Fi are presented in Table 3 below.
Table 3: Post Development Catchment Information
CATCHMENT INFORMATION
PERVIOUS Pervious Garden OVERALL
Natural Bed IMPERVIOUS
Area(m ) 2
197 75 274.5
tc 6
Fraction
impervious,
fi, % 36.0 13.7 50.2
1
I10 74.8
C10 0.35 0.7 0.9 0.71
Calculated catchment discharges for events from AEP 1% (ARI 100year) to AEP 63.21% (ARI 1year)
events are shown in Table 4 below.
Table 4: Post Development Catchment Discharges Q
ARI AEP(%) FY CY T
Iy DISCHARGE
(mm/h) m3/s L/s
1 63.21 0.80 0.57 125.0 0.0108 10.84
2 50.00 0.85 0.61 139.6 0.0129 12.86
5 20.00 0.95 0.68 187.2 0.0193 19.28
10 10.00 1.00 0.71 219.6 0.0238 23.81
20 5.00 1.05 0.75 251.2 0.0286 28.60
50 2.00 1.15 0.82 294.4 0.0367 36.71
100 1.00 1.20 0.86 327.4 0.0426 42.59
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
4 COUNCIL REQUIREMENTS FO R ALLOTMENT DRAINAGE
In accordance with the Noosa Plan 2020 and QUDM Section 7.13, the site is subject to a Level 0
drainage design standard. Under this standard, roof runoff may be directed to ground level towards a
drainage swale, as proposed for this site.
Table 9.4.6.3 of the Noosa Plan 2020 outlines performance outcome PO2, which requires maximising
on-site water efficiency through collection and reuse for non-potable purposes such as irrigation. To
meet acceptable outcomes AO2.1 and AO2.2, a 3000-litre rainwater tank is required for
accommodation uses. For non-accommodation uses, an appropriately sized rainwater storage system
must be provided to satisfy PO2.
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
5 CONCL USIO NS AND RECOMMENDATIONS
Based on the findings of the Rational method analysis for the site there is a slight decrease in runoff
of less than 1 L/s between pre and post development as shown in Table 5 below therefore, there is no
significant change in pre and post development flows from the site.
Table 5: Pre-development vs Post-development Comparison
ARI Pre-development Post-development Comparison
Discharge (Q, L/s) Discharge (Q, L/s) (L/s)
1 10.88 10.84 -0.04
2 12.91 12.86 -0.05
5 19.35 19.28 -0.07
10 23.90 23.81 -0.09
20 28.70 28.60 -0.10
50 36.84 36.71 -0.13
100 42.75 42.59 -0.16
To address item 15 from Noosa councils Request for Information, there is no need for collection or
detention of stormwater runoff for the proposed site for the purposes of mitigating post development
flow to predevelopment levels however, as discussed in chapter 4 of this report, sufficient collection of
stormwater runoff is required to meet councils’ specific performance outcomes.
Although the site falls under Level 0 roof water design standards per QUDM Section 7.13.10, it is
recommended to discharge roof runoff via a minimum 150mm diameter uPVC pipe to the existing
open drain located in the rear (eastern) buffer. The outlet should include a small plastic headwall (or
similar) and at least 0.3m² of 100mm D50 rock to prevent scour and ensure free drainage. This
solution is feasible only if existing drain levels are sufficient to allow connection and would meet the
Level 1 drainage design criteria outlined in QUDM Section 7.13.11.
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
6 REFERENCES
QLD Government. 2025. Soils Explained: Common Soil Types.
https://www.qld.gov.au/environment/land/management/soil/soil-
explained/types#:~:text=Podosols%20are%20mainly%20sandy%20soils,Fraser%20Island)%
20and%20Shelburne%20Bay.
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
Appendix 1. – Architectural Drawings
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DCM BUILDING DESIGN
18 SHEARWATER STREET, PEREGIAN BEACH – STORMWATER MANAGEMENT PLAN
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