Council archive · source document
Stormwater Reporting · RAL22/0021
Original PDF page 1, section 1. The text section number identifies this passage in the reader.
1
9 March 2023
Ref: AG/AG/213029-LA
102255ltr
Noosa Council
PO Box 141
Tewantin QLD 4565
Attention: Nadine Gorton (Planning & Development)
Dear Nadine
Re: Stormwater Management Plan
At: 39-41 Picture Point Cres Noosa Heads QLD 4567
For: Mrs Heidi Meyer
Council Ref: RAL22/0021
STORMWATER MANAGEMENT PLAN
Introduction
With reference to the abovementioned project, Covey Associates has been engaged to
undertake a Stormwater Management Plan for the proposed residential subdivision (1 lot into
2 lots) in response to an information request from Noosa Council dated 17 October 2022. In
particular this Stormwater Management Plan (SMP) addresses items 7 and 8 of the information
request regarding on-site disposal of stormwater and the potential impact on slope stability.
Previous Land-use, Topography and Drainage (Pre-development case)
The site is located at 39-41 Picture Point Cres, Noosa Heads. The real property description is
Lot 2 on RP 220514 and has an area of 1447m2. The site currently exists as a residential
property consisting of a house, driveway, pool and garden areas. In its existing state the site
is approximately 39% impervious (Figure 1).
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Section 2
2
Figure 1 – Existing Site Aerial (sourced from Nearmap)
The existing site drains from south to north as overland sheet flow which is directed towards
the Noosa Drive road reserve. This road reserve consists of a two way road with densely
planted vegetation within the verge on either side of the road. The site ultimately drains to
Noosa River which is located to the north of the site. In the pre-development case no
stormwater from the site discharges to Picture Point Crescent.
Proposed Land Use (Post-development case)
The development proposes a residential subdivision of 1 lot into 2 lots. It is proposed that in
the future a single dwelling will be built on each of the lots. Refer to Appendix A for the proposed
lot reconfiguration layout and indicative building layouts based on the allowable building
footprint.
It is proposed to discharge all future roof areas from each lot to the Picture Point Crescent kerb
and channel. The remaining proposed ground areas will be connected to an infiltration trench
which allows a portion of the stormwater to infiltrate into the natural ground with any excess
flow discharging over the northern boundary as sheet flow, as it does in the pre-development
case.
Stormwater Quantity
Stormwater Discharge to Picture Point Crescent
It is proposed to discharge stormwater from all roof areas to the Picture Point Crescent kerb
and channel via a charged downpipe system. Details of the design are provided in Appendix
A. This stormwater will then flow into the existing grated pit located in Picture Point Crescent.
Section 3
3
The catchment which discharges to the existing pit in the pre-development case is shown in
Figure 2.
SITE
Existing gully pit
Figure 2 – Existing Gully Pit Catchment (sourced from Noosa Council Mapping)
The following parameters were used to calculated the stormwater discharge from the
catchment:
Total catchment discharge to existing pit in Picture Point Crescent pre-development
parameters:
Area: 3767m2
Fraction impervious: 50%
Average Slope: 8%
Total catchment discharge to existing pit in Picture Point Crescent post-development
parameters:
Area: 4278m2 (includes 511m2 of future roof area)
Fraction impervious: 55%
Average Slope: 8%
Using the above parameters, the stormwater discharge in the pre-development and post-
development scenarios to Picture Point Crescent were calculated using the rational method as
shown in Appendix B and summarised in Table 1.
Section 4
4
Table 1 – Overall catchment peak flow discharging to existing pit in Picture Point Crescent
Peak Flow (l/s)
AEP
Pre-development Post-Development Difference
39% 100 120 +20
1% 260 300 +40
The existing kerb and channel on Picture Point Crescent is required to have capacity
equivalent to the 39% AEP storm event. The half road capacity up to the top of the kerb on the
development side of the road has been calculated to be 598 L/s using Manning’s equation.
The peak 39% AEP discharge from the post-development catchment is 120 L/s. Therefore, the
road has adequate capacity to cater for the increase in stormwater discharge from the
development. The half road width is only required to cater for the 39% AEP stormwater event
however it does have the capacity to cater for the 1% AEP discharge from this catchment. It is
important to note that the discharge to the Picture Point Crescent kerb and channel must be
limited to 25 L/s per lot with any excess flow to discharge toward the north of the property (as
explained later in this report).
The kerb and channel then discharges into the existing grated pit in the road way. It is noted
that the existing pit and pipe stormwater network is required to achieve a capacity of 39% AEP
discharge of the incoming catchment. Based on the GIS data from Noosa Council Mapping
system and using Manning’s equation the capacity of the downstream pipe was calculated.
The downstream pipe is a 300mm RCP at 25% grade which has a capacity of approximately
522 L/s. In the post-development case, the proposed 39% AEP discharge to this pipe is 120
L/s. Therefore, the existing 300mm RCP pipe has more than enough capacity to capture for
the increase in stormwater discharge due to the proposed development. Any flow that does
not get captured by the stormwater pit will flow through the overland flow path above the
stormwater alignment between 35 and 37 Picture Point Crescent, as it does in the pre-
development case.
Therefore, the proposed development will have a non-worsening effect on the peak stormwater
discharge to Picture Point Crescent and the surrounding properties.
Stormwater Discharge to Noosa Drive
The proposed ground areas (including the future driveways) will discharge to the proposed
infiltration trench provided for each lot respectively. The infiltration trench will allow the
stormwater runoff to discharge into the natural sand as on-site disposal. In extreme rainfall
events, when the infiltration trench reaches its maximum capacity, any excess stormwater will
discharge as sheet flow over the northern boundary due to the proposed level spreader
(concrete edging) which forms part of the infiltration trench.
The proposed design is consistent with the recommendations in Tectonics Geotechnical
Investigation Report No. 22511-001-Rev0 provided in Appendix C. In the report they also
determined that the proposed design would not have any impact on slope stability provided
their recommendations in the report were implemented. Further, Tectonic has determined that
the sandy soil encountered on-site was consistent with clean fine to medium grained sand
which have a design coefficient of permeability of 1 x 10-4 m/s. Details of the proposed
infiltration system are shown in Appendix A.
Section 5
5
Discharge to Noosa Drive pre-development site parameters:
Area: 1447m2
Fraction impervious: 39%
Average slope: 33%
Discharge to Noosa Drive post-development site parameters:
Area: 934m2
Fraction impervious: 4%
Average Slope: 33%
Using the above parameters, the stormwater discharge in the pre-development and post-
development scenarios to Noosa Drive were calculated as shown in Appendix B and
summarised in Table 2. It is noted that the post-development flows have decreased compared
to the pre-development case due to the future roof areas discharging to the south towards
Picture Point Crescent instead of discharge over the northern boundary towards Noosa Drive.
Therefore, the proposed development will have a non-worsening effect on the peak stormwater
discharge towards Noosa Drive and the surrounding properties.
Table 2 – Site peak flow discharging to Noosa Drive
Peak Flow (l/s)
AEP
Pre-development Post-Development Difference
39% 40 30 -10
1% 110 70 -40
Conclusion
This Stormwater Management Plan (SMP) has shown compliance with the stormwater
drainage requirements outlined in the Noosa Plan (2020). This site based SMP has
demonstrated that efficient management of stormwater runoff for the proposed development
is possible by adopting the stormwater strategies set out in this report.
Trusting the above is to your satisfaction. Should further information be required please contact
this office.
Yours faithfully
COVEY ASSOCIATES PTY LTD
ALLISTER GAFFNEY
Civil Engineer
BEng(Civil), MEng, RPEQ 24345
Section 6
APPENDIX A SITE LAYOUT AND ENGINEERING PLANS
Section 7
Area
Not Surveyed
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RL 48.084 AHD
Axis Surveys Pty Ltd ABN 94 010 743 174
Trading as: ACN 010 743 174
AXlS
SURVEYS
UNIT 5, 23 OVERLORD PLACE, ACACIA RIDGE, QLD 4110
2200853-01 C Ph (07) 3363 8100, www.axissurveys.com.au
Section 8
AREAS: COUNCIL GFA/PLOT RATIO: GFA= 604m²
LOWER FLOOR: 196m² SITE AREA = 1447m² LOWER FLOOR: 226m² PLOT RATIO= 604m² /
GROUND FLOOR: 203m² SITE / 2 = 723.5m² GROUND FLOOR: 203m² 723.5m²
31.673 UPPER FLOOR: 132m² UPPER FLOOR: 132m² = 0.83:1
338°30' ROOF FLOOR: 73m² SITE COVER = 245m² ROOF FLOOR: 73m²
245m² / 723.5m² = (33.9%)
GFA= 604m²
KEY:
AW - AWNING WINDOW CO - COFFEE MACHINE N - NICHE SLD - SLIDING DOOR
B - BATH FD - FRENCH DOORS OV - OVEN SLW - SLIDING WINDOW
IGHT
UP TO 4.5M HE
1.5M SETBACK P - PANTRY T - TUB
IGHT BFD - BI-FOLD DOOR FR - FRIDGE
M AND 7.5 M HE
BETW EEN 4.5
2M SETBACK BFW - BI-FOLD WINDOW FP - FIXED PANEL WINDOW SH - SHOWER V - VANITY BASIN
CT - COOK TOP L - LOUVER WINDOW S - SINK WC - WATER CLOSET
LOT 2 ON RP220514,
39 PICTURE POINT CRES
6M
NOOSA HEADS
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QLD 4567
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15.87 0"
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1.5M SETBACK UP TO 4.5M HEIGHT
1.5M SETBACK UP TO 4.5M HEIGHT
2M SETBACK BETWEEN 4.5M AND 7.5M HEIGHT
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1.5M SETBACK UP TO 4.5M HEIGHT
EXISTING SEWER /
MANHOLES TO BE PROPOSED
RL 48.5 DEMOLISHED MANHOLE
50.238
RL 46.5 RL 45 163°12'40" RL 44 RL 43 RL 42 RL 41 RL 40 RL 38 RL 37
WM RL 49.5 RL 39
PP
CLIENT: Heidi Meyer PROJECT: Picture Point
www.chriscloutdesign.com.au GENERAL NOTES:
Use written dimensions only. DO NOT scale drawings. Contractors SITE ADDRESS: Lot 2 on RP220514, 39 Picture Point Cres, Noosa Heads QLD 4567
A: OFFICE 1/20 DUKE STREET, to verify all dimensions on site prior to commencing works. Site
SUNSHINE BEACH, QLD 4567, location in accordance with engineers details. These drawings are to DRAWING TITLE: SITE PLAN
be read in conjunction with engineers design and details, the
E: [email protected] DATE: 16.11.22 SCALE: 1 : 100 @ A2 DRAWN BY: C.CLOUT
P: (07) 54748 107 BSA LICENCE: 1127508
accompanying building specification and schedule of finishes. If in
doubt, please request clarification. DO NOT ASSUME. ISSUE: PRELIMINARY CONCEPT
C1.0
Section 9
ROOF PP ROOF PP
58100 58100
2700
ROOF TERRACE ROOF TERRACE
300
55400 55400
UPPER PP UPPER PP
55100 55100
3300
UPPER LVL UPPER LVL
300
51800 51800
GROUND PP GROUND PP
51500 51500
3300
GROUND LVL GROUND LVL
300
48200 48200
LOWER PP LOWER PP
47900 47900
3000
LOWER UPPER LVL LOWER UPPER LVL
44900 44900
1000
LOWER LVL LOWER LVL
43900 43900
ELEVATION 1
SCALE: 1 : 100
ROOF PP ROOF PP
58100 58100
2700
ROOF TERRACE ROOF TERRACE
300
55400 55400
UPPER PP UPPER PP
55100 55100
3300
UPPER LVL UPPER LVL
300
51800 51800
GROUND PP
GROUND PP
51500
51500
3300
GROUND LVL GROUND LVL
300
48200 48200
LOWER PP LOWER PP
47900 47900
3000
LOWER UPPER LVL LOWER UPPER LVL
44900 44900
1000
LOWER LVL LOWER LVL
43900 43900
4233
ELEVATION 2 MIN
SCALE: 1 : 100
IL 40300
APPROX NEW SEWER
CLIENT: Heidi Meyer PROJECT: Picture Point
www.chriscloutdesign.com.au GENERAL NOTES:
Use written dimensions only. DO NOT scale drawings. Contractors SITE ADDRESS: Lot 2 on RP220514, 39 Picture Point Cres, Noosa Heads QLD 4567
A: OFFICE 1/20 DUKE STREET, to verify all dimensions on site prior to commencing works. Site
SUNSHINE BEACH, QLD 4567, location in accordance with engineers details. These drawings are to DRAWING TITLE: ELEVATIONS
be read in conjunction with engineers design and details, the
E: [email protected] DATE: 16.11.22 SCALE: 1 : 100 @ A2 DRAWN BY: C.CLOUT
P: (07) 54748 107 BSA LICENCE: 1127508
accompanying building specification and schedule of finishes. If in
doubt, please request clarification. DO NOT ASSUME. ISSUE: PRELIMINARY CONCEPT
C2.1
Section 10
CIVIL
PROPOSED LOT RECONFIGURATION
AT
39 - 41 PICTURE POINT CRESCENT, NOOSA HEADS, 4567
FOR
MRS. HEIDI MEYER
APPLICATION NO. RAL22/0021
Consulting Civil &
Structural Engineers
Project Management
ASSOCIATES PTY LTD
& Planning
PROJECT No. 213029 - ISSUE FOR APPROVAL
SUBJECT SITE
PROJECT MANAGER: CHRIS CAMP PH: 07 5443 7777
Sheet List Table
Sheet Number Sheet Title
C000 COVER SHEET
C300 STORMWATER MANAGEMENT PLAN
C301 STORMWATER DETAILS
C350 STORMWATER CATCHMENT PLAN
C400 SEWER AMD WATER CONNECTION PLAN
C401 SEWER DETAILS
LOCALITY PLAN
Local Government: NOOSA SHIRE COUNCIL
Locality: NOOSA HEADS
Cover Sheet Issue - A
C:\12dS\data\12DSERVER\213029_1964\DWG Covey\Civil\Uncontrolled\C000 COVER SHEET.dwg
Section 11
IT IS THE RESPONSIBILITY OF THE
CONTRACTOR TO CONTACT THE RELEVANT
AUTHORITIES TO CONFIRM THE LOCATION OF
ALL EXISTING SERVICES PRIOR TO THE
COMMENCEMENT OF EXCAVATION
0'
°2
29
.5
39
(50.238)
31.5 . 0
40
32.0
5
40.
51
.1 0'
39 9°2
32.5 2
STORMWATER INFILTRATION
33.0 TRENCH. REFER DETAIL ON C301 41.0
33.5 LEGEND
41.5
34.0 .65 PROPOSED SEWER
.5 13 42.0
34 EXISTING SEWER
Ø150
35.0 42.5 PROPOSED
Pe
35.5 Foungd Ø150 SW STORMWATER
43.0
STORMWATER GP2
CONNECTION POINT
36.0 INFILTRATION TRENCH.
5
INDICATIVE BUILDING
43.
REFER DETAIL ON C301 LOWER FLOOR
36.5 PROPOSED LOT 51
Ø150
43.0 CONTOUR AND LABEL
37.0 Ø150 SW 44.
0
GENERAL DIRECTION OF
GP2
37.5 CONNECTION POINT SURFACE FALL
5
38.
0 44.
5
38.
A
163°12'40"
0
50.238
45.
DP SURVEY NOTE:
0
3 .
ALL SURVEY INFORMATION PROVIDED BY AXIS
9
0
.5 42.
5 43. SURVEYS.
39. 0 PROPOSED LOT 52 43.0 5 5
45.
PH: 07 3363 8100
. 5
42
40. 0
0 DRAWING NO: 2200853
4
44.0
DATED: 4 MARCH 2022
41. DP
46.
0 DATUM AS SHOWN ON PLAN
5
41.
338°30'
0
31.673
4 .
2 46.5
338°30'
31.673
42.5
//
45.0
//
//
3 DP
RL 48200
//
43.0
//
Sewer M/H The text continues on section 12.
Used in these records
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