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Stormwater Treatment & Water Quality Management Plan_April2014
Attached to the e-mail REC13/0146 - Response to Information Request - Email 2.
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Log in to see the plans as drawn RECONFIGURATION OF LOT 136
ON MCH978
STORMWATER TREATMENT AND
WATER QUALITY MANAGEMENT PLAN
FOR
VALKEV PTY LTD
APRIL 2014
Civil, Environmental &
Hydraulic Engineers
A.B.N. 45140292324
8/41 Sunshine Beach Rd
Noosa Junction Q 4567
Telephone (07) 54749081
Facsimile (07) 54749041
Job No: 1225
www.callaghanandtoth.com.au
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Page 2
Callaghan & Toth
DOCUMENT HISTORY
Document Reference: No: 1225_SMP_Master.doc
Project Manager: Alex McWilliam
Author: Lex Toth NPER3 (ENV) (CIVIL) RPEQ 6069 CPESC
Reviewer: Jane Davissen BE (ENV)
Client: Kevin and Val Kelly
Contact Person: Alex McWilliam (07 54 555425)
DISTRIBUTION LIST
POSITION ON
NAME ORGANIZATION REVISION REVISION REVISION
MANAGEMENT TEAM
0 1 2
Kevin and Val Kelly Valkev Pty Ltd Client
Jane Davissen Callaghan & Toth Author
Alex McWilliam McWilliam Property Project Manager
Max Watterson Max Watterson & Planner
Associates
Noosa Council Assessment Officer
REVISION LIST
REVISION DATE DISTRIBUTED ISSUED BY CHECKED BY
The information contained in this report is confidential and proprietary to Callaghan and Toth. It may
only be used by the person to whom it is provided, for the stated purpose for which it is provided, and
must not be imparted to any third person without the prior written approval of Callaghan and Toth.
Callaghan and Toth reserve all legal rights and remedies in relation to infringement of its rights in
respect of its confidential information.
©Callaghan & Toth
2014
55 Lake MacDonald Drive – Stage 1 to 5 pg. 2
Page 3
Callaghan & Toth
CONTENTS
1. SUMMARY ............................................................................................................... 5
2. INTRODUCTION...................................................................................................... 6
3. SITE DESCRIPTION................................................................................................ 8
3.1 Proposed Works................................................................................................. 8
4. WATER QUALITY MANAGEMENT PLAN ............................................................. 12
4.1 Proposed On-Site Stormwater Treatment Process .......................................... 12
4.2 MUSIC Model ................................................................................................... 12
4.2.1 Source Nodes ............................................................................................ 12
4.2.2 Treatment Nodes ....................................................................................... 14
4.2.3 Rainfall Data .............................................................................................. 15
4.3 MUSIC Modelling Results ................................................................................ 16
4.3.1 Water Quality Objectives ........................................................................... 16
4.3.2 Assessment of Results .............................................................................. 16
4.4 TREATMENT DEVICES DESIGN DETAILS .................................................... 17
5. FLOODING ASSESSMENT SUMMARY ................................................................ 21
5.1 Existing Conditions ........................................................................................... 21
5.2 Proposed Drainage System ............................................................................. 21
5.3 Western Tributary ............................................................................................. 22
INSERT DRAWING NUMBER 1225-33 ........................................................................ 23
6. CONCLUSIONS & RECOMMENDATIONS ........................................................... 24
APPENDIX 1 - Preliminary Stormwater Quality Management Plan.......................... A
APPENDIX 2 - MUSIC Results ................................................................................ B
APPENDIX 3 - Site Photos ...................................................................................... C
APPENDIX 4 - BSM Flood Report ........................................................................... F
55 Lake MacDonald Drive – Stage 1 to 5 pg. 3
Page 4
Callaghan & Toth
LIST OF REFERENCES
1. Department of State Development, Infrastructure and Planning, “State Planning Policy”,
December 2013
2. Engineers Australia, “Australian Runoff Quality Guidelines”, 2006.
3. Healthy Waterways, “Water Sensitive Urban Design Technical Design Guidelines for
South East Queensland”, 2006.
4. Water by Design, “MUSIC Modelling Guidelines for South East Queensland” – Version
1, December 2010.
5. Water by Design, “Deemed to Comply Solutions – Stormwater Quality Management
(South East Queensland)”, Version 1.0 May 2010
6. Wong, T., Breen, P. & Lloyd, S., “Water Sensitive Road Design – Design Options for
Improving Stormwater Quality of Road Runoff. CRC for Catchment Hydrology Technical
Report No 00/1”, 2000.
LIST OF FIGURES
Figure 1.1 Site Location Plan……………………………………………………………...7
Drawing 1225-50 Reconfiguration Layout Plan………………………………………………….9
Figure 3.1 Stormwater Layout – Stage 1, 2, 3 & 5.……………………………… ……10
Figure 3.2 Stormwater Layout – Stage 4…. …………………………………………...11
Figure 4.1 MUSIC Model for the Proposed Development…………………………….13
Figure 4.2 Typical Bioretention Basin Detail…..……………………………………….19
Figure 4.3 Typical Kerbside Basin and Raingarden Detail……………………………20
Drawing 1225-33 Riparian Zones Stage 3 and 5………………………………………………23
LIST OF TABLES
Table 4.1 MUSIC Catchment Areas……………………………………………………14
Table 4.2 Comparison of Load Reductions……………………………………………16
Table 4.3 Design Features of Stormwater Treatment Systems……………………..20
Table 5.1 Pre-Development and Post Development Discharges……………………21
55 Lake MacDonald Drive – Stage 1 to 5 pg. 4
Page 5
Callaghan & Toth
1. SUMMARY
The key points of this investigation are as follows:
1. Runoff from new roadways, footpaths and allotments is to be cleaned of nutrients and
gross pollutants via a stormwater treatment system prior to being released to existing
waterways.
2. The stormwater treatment system includes:
a. One small Bioretention Basin (already completed for Stage 1)
b. Two medium Bioretention Basins located in park,
c. Three small Roadside Bio Basins,
d. Two Bioretention swales,
e. Three Raingardens for Lots 26, 27 & 28, and
f. One Grassed Buffer.
3. The increase in pollutant loads due to the increase in impervious areas is to be
attenuated.
4. Stormwater Detention is to achieve no increase in runoff concentration by the following
measures:
a. Riparian vegetation planting to attenuate flood flows:
b. Pedestrian bridge over the eastern tributary (off Lake MacDonald Drive)
to attenuate flows;
c. Detention storage in Bioretention Basin 2 and 3;
d. Reshaping of the western tributary (off Blue Wren Place) to provide
greater flood storage.
55 Lake MacDonald Drive – Stage 1 to 5 pg. 5
Page 6
Callaghan & Toth
2. INTRODUCTION
This Stormwater Quality Management Plan (SWQMP) has been prepared in response to
Information Requests for the following applications:
1. Reconfigure a Lot application (REC13/0146) at 55 Lake MacDonald Drive, Cooroy, and
2. Preliminary Approval for Material Change of Use (MCU 13/0226) and Reconfigure a Lot
(REC 13/0148) at Pearsons Rd, Cooroy.
Each of the issued Information Requests by the then Sunshine Coast Regional Council,
requested an overall Stormwater Quality Management Plan showing how stormwater from both
developments will be treated to meet current best practice load based reduction targets and
drainage requirements. As such this Stormwater Management Plan (SWQMP) has been
prepared in accordance with the:
Water Sensitive Design Code in the Noosa Plan;
Water Sensitive Urban Design Technical Design Guidelines for South East
Queensland, published by Health Waterways; and
Environmental Protection (Water) Policy 2008.
The lots contributing to the overall development and subject to this report are shown in Site
Location Plan, Figure 1.1 and are described as follows:
1. Lot 136 and Lot 137 on MCH978 and Lot 1 on RP173883 located at 55 Lake MacDonald
Drive – which is reconfigured into 32 lots of which Stage 1 (four lots) and Stage 2 (3 lots)
have been approved, and
2. Lot 135 on MCH978 located at Pearsons Road Cooroy – will be reconfigured into 25 lots.
This SWQMP considers the new hardstand areas, including roadways, footpaths, allotments,
and new roof areas for the proposed 57 lots. This report also aims to demonstrate that the
proposal complies with relevant codes and guidelines and that the storm water runoff will not
change the surrounding hydrology. The Model for Urban Stormwater Improvement
Conceptualization (MUSIC) has been used to assess the suitability of various treatment devices
and to model existing and predicted pollution export loads and concentrations from the
development areas.
55 Lake MacDonald Drive – Stage 1 to 5 pg. 6
Page 7
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Page 8
Callaghan & Toth
3. SITE DESCRIPTION
The site consists of four (4) rural lots which are mostly cleared land for rural pursuits. The site
is bounded by Lake MacDonald Drive to the south-east, residential development to the south-
west and north.
Two watercourses run through the site as shown on Drawing Number 1225-50 Revision A.
The watercourses join just downstream of this development and eventually flow to Six Mile
Creek, a tributary of the Mary River. This site is subject to the ponding of floodwaters. The Q100
year ARI flood levels indicate that the extent of flooding does not impact on the proposed lots,
as shown in BSM Flood Report in Appendix 4.
The Cooroy and Lake MacDonald Biodiversity Overlay (Map OM3.1) from the Noosa Plan also
shows that these watercourses are subject to Riparian Buffer Areas along most of their lengths.
These two watercourses are tributaries of Six Mile Creek and shall hereafter be described as
the eastern and western tributaries (see Drawing Number 1225-50).
3.1 Proposed Works
The overall proposal is to reconfigure these four lots into a total of 57 lots. The overall
reconfiguration will include:
Construction of new roads;
Construction of pathways;
Allotment shaping;
Dedication of parkland – active and passive, including riparian buffer areas; and
Construction and provision of services.
As a result of these works stormwater drainage and treatment devices are required to drain the
site, attenuate flows and treat stormwater runoff to acceptable levels.
Figure 3.1 shows the stormwater layout for Stage 1 and 2 (already completed), Stage 3 and
Stage 5 while Figure 3.2 shows the stormwater layout for Stage 4.
55 Lake MacDonald Drive – Stage 1 to 5 pg. 8
Page 9
Civil, Environmental &
Hydraulic Engineers
SEDIMENT AND EROSION CONTROL
Sedimentation Controls shall comply with
the requirements of,
"MANUAL FOR EROSION AND SEDIMENT
CONTROL, MAROOCHY SHIRE COUNCIL"
(MESC, 2007) which can be accessed on the
Councils external internet site.
energex
Works Standards refer to,
"Contract Standards for Erosion and
Sediment Control on Construction Sites."
Page 10
LEGEND STAGED WORKS
STAGE 1 WORKS AREA - OPW13/0417
STAGE 2 WORKS AREA — OPW13/0616
STAGE 3 WORKS AREA
STAGE 4 & 5 WORKS AREA
ROAD IS TOO FLAT FOR KERB,
2m OFF EDGE OF SHOULDER.
INSTALL TYPE 22 CONCRETE INVERT
TURF EITHER SIDE OF INVERT.
RP20685
+TUBE STOCK
MULCH & REVEGETATION
0.1m DEEP COARSE SAND
TRANSITION LAYER (0.5mm-2mm) ——_—L |
0.15m MINIMUM DEEP S-2mm WASHED SCREENINGS &
SLOTTED RIGID SEEPAGE PIPES & 0.5% MIN GRADE.
LEGEND:
SW
+
+ ee
EXISTING FLOWS TO ADJACENT LOT ARE ATTENUATED TO
PRE-DEVELOPMENT LEVELS BY REMOVING Q5 FLOW TO
BIO-RETENTION BASIN FOR TREATMENT. OVERLAND FLOW
CONTAINED BETWEEN LOTS 39 &40.
NTS
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36
SAG PITS TO TAKE Q5, OVERFLOW TO
FLOW PATH BETWEEN LOTS 39/40
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REQUIREMENTS. 4mx4m CONCRETE HARDSTAND
150mm ABOVE GROUND LEVEL. WIDEN SHOULDER TO
3m WITH TAPERS IN ACCORDANCE WITH TRANSLINK
REQUIREMENTS.
|
—~| 0.80 1.20 ++ 1.00 +++ 1.20 --| FLUSH KERB
TS2000 SAND ROAD EDGE
TOPSOIL & TURF
@8/sqm
LOW POINT OF LOT 5 RP206856,
LOCATION OF FUTURE STORMWATER
DRAINAGE THROUGH LOT 12 RP134343
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( Callaghan & Toth )
Civil, Environmental &
Hydraulic Engineers
PO BOX 2305
NOOSA HEADS 4567
8/41 Sunshine Beach Road
Phone 54749081, Fax 54749041
www.callaghanandtoth.com.au
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=|
TO TYPICAL DETAIL FIGURE 4.2
designed | ADT datum AHD DERIVED
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PROPOSED BIORETENTION SWALE TO
PS
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TYPICAL SECTION SHOWN BELOW
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FINAL Q100 FLOOD LINE
EXISTING TOP OF BANK
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PREVIOUS ROAD
RESERVE. BDY
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MAX WATTERSION & ASSOCIATES
PHONE 54 426 121
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PROPOSED 57 LOT SUBDMSION
55 LAKE MacDONALD DRIVE
COOROY
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title
STAGE 4 STORMWATER MASTER
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LOT 136 on MCH978
Parish of TEWANTIN
County of MARCH
SUNSHINE COAST COUNCIL
Locality of LAKE MacDONALD
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SCALE
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USE ONLY DIMENSIONS PROVIDED
REVISIONS
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COMPUTER DIRECTORY
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date 10-3-14
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INTER-ALLOTMENT ——————
STORMWATER
MAX WATTERSION & ASSOCIATES
PHONE 54 426 121
(SS
project
PROPOSED 57 LOT SUBDMSION
55 LAKE MacDONALD DRIVE
LOT 136 on MCH978
Parish of TEWANTIN
County of MARCH
SUNSHINE COAST COUNCIL
Locality of LAKE MacDONALD
4 BIO BASIN 3
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SURFACE AREA
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Page 12
Callaghan & Toth
4. WATER QUALITY MANAGEMENT PLAN
4.1 Proposed On-Site Stormwater Treatment Process
The developed site was divided into MUSIC model sub-catchments as shown on Figure 4.1.
The proposed stormwater treatment train for the overall development site is illustrated on
Figure 3.1 and Figure 3.2 and are described below:
a. One small Bioretention Basin (BioBasin 1)(already completed for Stage 1 i.e. Lots 1
to 4),
b. Two medium Bioretention Basins located in parkland treating runoff as follows:
i. BioBasin 3 – Stages 2 and 5 i.e. Lots 5 to 16 and associated road reserve, and
ii. BioBasin 2 – Stage 4 i.e. Lot 33 to 57.
c. Three small Roadside Bio Basins (1a, 1b and 2) treating runoff from Lots 21 to 25
and associated road reserve (part of Stage 3),
d. Two Bioretention swales treating runoff from Lots 17,19,20,29 to 32 and associated
road reserve (part of Stage 3),
e. Three Raingardens for Lots 26, 27 & 28 (part of Stage 3), and
f. A grassed buffer to treat sheet flow of road connecting Stage 3 to Blue Wren Place.
BioBasin 3 is located within the new Passive Parkland Area and discharges into the eastern
tributary. The three (3) raingardens will be located within the lots which they are treating and
also discharges into the eastern tributary
.
BioBasin 2 is located within the new Passive Parkland Area, the small roadside Bio Basins and
the swales are located along the new roadway off Blue Wren Court and these systems all
discharge into the western tributary.
The bio-retention component of these treatment systems will remove the nutrients, heavy
metals, and retard flow.
4.2 MUSIC Model
4.2.1 Source Nodes
Catchment areas of source nodes within the proposed development have been identified as
sub-catchments such as roofs, yard, road and verge. MUSIC allows for characteristics of these
source nodes to be amended to ensure that accurate pollution generation and hydraulic
characteristics for each sub-catchment are used to generate stormwater runoff within the
model. Table 4.1 below details the sub-catchments used in the MUSIC model, land use,
percent imperviousness and area of each sub-catchment. The MUSIC Modelling Guidelines for
South-East Queensland – Version 1 December 2010 have been used to set level of
imperviousness. The urban residential pollutant export parameters within the guidelines have
been used for each node.
The site has also been divided into three (3) main discharge points and modelled as such,
being
Lots 1 to 16, and 26 to 28 discharging into creek flowing from east to west coming from
Lake MacDonald Drive
Lots 17 to 25 and 29 to 32 discharging into eastern side of creek flowing from south to
north coming from Blue Wren Place
Lots 33 to 57 discharging into western side of creek flowing from south to north from
Blue Wren Place.
55 Lake MacDonald Drive – Stage 1 to 5 pg. 12
Page 13
"Roadways | Lot 20 to25 - Yard Lot 20 to25 - Roof Area 17,19 - Roof Area Lot 1 to 4- Yard, Roadways from Blue Wren Place Lot 17,19-Yard | Lot 26-28 - Yard Lot 26-28 - Roof Areal = 5 | _Raingardens x3_ — | of ft | Lot $ to16 - Ys te ahve BioBasin 3- Park Callaghan & Toth Civil, Environmental & Hydraulic Engineers 8/41 Sunshine Beach Road PO BOX 2305 NOOSA HEADS 4567 Ph: 54749081 Fax: 54749041 www.callaghanandtoth.com.au 1 to 4-Roof, 28m2 Roadside BioBasin 1 Bioretention Swale 1 10m2 Roadside | | Lot 33-57 - Roof Area Lot 29 to 32- Roof Area Pal Bioretention Swale 2) ‘Lot 33-57 - Yard (Completed) from Blue Wren North section of trom Blue Wren Place Lot 18 - Yard. Lot 18- Roof Area Joining Road from Blue Wren Place | Junction - Ck off Blue Wren Place’ | Junction - east west gully | Junction west side stg5 gully RaceWing Node -T of Six Mile Ck project 57 LOTS RESIDENTIAL RECONFIGURATION MUSIC MODEL location 55 LAKE MACDONALD DRIVE / PEARSONS ROAD COOROY Figure 4.1 Date: APRIL 2014 Page 13
Page 14
Callaghan & Toth
TABLE 4.1 MUSIC CATCHMENT AREAS (DEVELOPED)
Catchment Land Use Music Impervious Area (ha)
Lot 1 – 4 Urban – Roof 100% 0.08
Yard – Lot 1 to 4 Urban – Yard 20% 0.167
Road Widening + Verge (Lake Urban – Road 60% 0.051
MacDonald Dr)
Lot 5 – 16 Urban – Roof 100% 0.3
Yard – Lot 5 to 16 Urban – Yard 20% 0.717
Road Widening + Verge (Masonry Urban – Road 60% 0.185
Street)
Lot 26 to 28 Urban – Roof 100% 0.075
Yard – Lot 26 to 28 Urban – Yard 20% 0.126
Lot 17 to 25 and 29 to 32 Urban – Roof 100% 0.40
Yard – Lot 17 to 25, and 29 to32 Urban – Yard 20% 0.61
Roadway (off Blue Wren Ct) Urban – Road 60% 0.40
Lot 33 - 57 Urban – Roof 100% 0.625
Yard – Lot 33 to 57 Urban – Yard 20% 1.065
Roadway (off Blue Wren Pl) Urban – Road 60% 0.461
TOTAL 5.262ha
4.2.2 Treatment Nodes
The “MUSIC Modelling Guidelines for South East Queensland” Version 1 prepared by Water by
Design and dated December 2010 has been used to set the rainfall runoff parameters and
pollutant export parameters for the site.
The land use type used for this model was “Urban” and the values in the guideline shown in
Table 3.7 and Table 3.8 of the guidelines have been used in this model.
Treatment nodes proposed for areas discharging into the eastern tributary (Stages 1, 2,
part of 3 and 5):
1. Bioretention Basin 1 (already completed as part of Stage 1):
a. Located in Passive Parkland adjacent to Lake MacDonald Drive.
b. It is 47m2 in area with a filter area of 25m2.
c. Filter layer depth of 0.5m and an extended detention depth of 0.3m.
55 Lake MacDonald Drive – Stage 1 to 5 pg. 14
Page 15
Callaghan & Toth
d. The size and depth of the systems have been designed in accordance with
Water by Design Guidelines and a typical plan and section are shown in Figure
4.2.
2. Bioretention Basin 3
a. Located in Passive Parkland adjacent to Masonry Street.
b. Designed with a filter area of 150m2.
c. Filter layer depth of 0.5m and an extended detention depth of 0.3m.
d. The size and depth of the systems have been designed in accordance with
Water by Design Guidelines and a typical plan and section are shown in Figure
4.2.
3. Raingardens – Lot 26,27,28
a. Located within Lots 26, 27 and 28
b. Each designed with an area of 6m2 filter area
c. Filter layer depth of 0.4m and an extended detention depth of 0.15m.
d. The size and depth of the systems have been designed in accordance with
Water by Design Guidelines and a typical plan and section are shown in Figure
4.3.
Treatment nodes proposed for areas discharging into the western tributary (Part of Stage
3), eastern bank:
4. Bioretention Swales 1 and 2
a. Located in road reserve adjacent road off Blue Wren Place
b. Designed to have filter areas of 97m2 and 82m2 respectively
c. The swales are 80m and 70m respectively with a total of 150m swale length.
d. Filter layer depth of 0.4m.
e. The size and depth of the systems have been designed in accordance with
Water by Design Guidelines.
5. Roadside Bio Basins 1a and 1b and 2
a. Located in road reserve
b. Designed to have filter areas of 10m2, 15m2 and 10m2 respectively.
c. Filter layer depth of 0.4m and extended detention depth of 0.1m.
d. The size and depth of the systems have been designed in accordance with
Water by Design Guidelines.
6. Grassed Buffer
a. Located in road reserve.
b. Accepts sheet flow from road.
c. Is approximately 50% of impervious area of the road.
Treatment nodes proposed for areas discharging into the western tributary (Stage 4),
western bank:
7. Bioretention Basin 2:
a. Located in Passive Parkland adjacent to creek.
b. Design with a filter area of 211m2.
c. Filter layer depth of 0.5m and an extended detention depth of 0.3m.
d. The size and depth of the systems have been designed in accordance with
Water by Design Guidelines. A typical bioretention basin plan and cross-section
is shown in Figure 4.2.
4.2.3 Rainfall Data
The meteorological data used for the MUSIC Model was the data for Cooroy from 01/01/92 –
31/12/02 and is a 6 minute time step. The choice of the data was based on recommendations
from Noosa Council Land Development Section.
55 Lake MacDonald Drive – Stage 1 to 5 pg. 15
Page 16
Callaghan & Toth
The mean Annual Rainfall for Cooroy 92 – 02 = 1585mm
The mean Annual Rainfall for Cooroy 72 – 02 = 1650mm
The MUSIC Modelling Guidelines (2010) details that Cooroy data for 1973 to 1983 should be
used. This data has an annual average Rainfall of 1600mm. It is considered that the 10 year
period from 1992 – 2002 has a relatively close mean annual Rainfall to the recommended 10
year period and as such is acceptable to use in this case.
Urban Residential rainfall-runoff parameters from the draft guidelines have been used.
4.3 MUSIC Modelling Results
The MUSIC modelling program has been used to investigate the performance of various
treatment options in the treatment train. MUSIC Version 6.0.1 is the current version and was
used to assess this development proposal.
4.3.1 Water Quality Objectives
This proposed stormwater treatment system for the development, when modelled using MUSIC
meets the pollution load reduction target as detailed in DSDIP’s State Planning Policy
December 2013 – Appendix 2, Table B. The following have been included in Appendix 2.
The treatment train effectiveness for the system.
The MUSIC Version 6.0.3 Summary Report.
The treatment train effectiveness for the system is shown below in Table 4.2. The results
indicate that the proposed stormwater treatment train will be effective in achieving the
reductions as outlined in the State Planning Policy December 2013 – Appendix 2, Table B. It
reduces sediment and nutrient concentrations and loads to an acceptable level and also
reduces runoff concentrations.
TABLE 4.2: COMPARISON OF LOAD REDUCTIONS
MUSIC REDUCTION POLLUTANT LOAD
PARAMETERS
RESULTS REDUCTION TARGETS
Flow 3%
Total Suspended Solids 81% 80%
Total Phosphorous 58% 60%
Total Nitrogen 51% 45%
Gross Pollutants 99% 90%
4.3.2 Assessment of Results
The developed site has been modelled as a series of Urban Residential sub-catchments, which
incorporate Water Sensitive Urban Design (WSUD) treatment trains. Figure 3.1 and Figure 3.2
show the proposed locations of the treatment systems. The reductions listed in Table 4.2 above
generally comply with Council’s requirements, Water by Design Deemed to Comply Solutions
and the State Planning Policy December 2013 – Appendix 2, Table B. Therefore, it is
considered that the proposed stormwater treatment system is currently sufficient to reduce the
pollutants prior to exiting the site and entering the tributary of the Six Mile Creek.
55 Lake MacDonald Drive – Stage 1 to 5 pg. 16
Page 17
Callaghan & Toth Total Phosphorus result for the site discharging into the tributaries is 58% - which is considered suitable as the target is 60% and the result is within acceptable model error. 4.4 TREATMENT DEVICES DESIGN DETAILS Below in Table 4.3 are general design details for stormwater treatment systems. Lining: The surrounding soils are clay to silty clays with a saturated hydraulic conductivity of approximately 3.6mm/hr. The sandy loam media that is proposed as the filter media has a hydraulic conductivity of 200mm/hr, therefore the conductivity of the filter media is > 10 times the conductivity of the surrounding soils and an impervious liner is not considered to be required. 55 Lake MacDonald Drive – Stage 1 to 5 pg. 17
Page 18
Callaghan & Toth
TABLE 4.3: Design Features of Stormwater Treatment Systems
Extended
Filter Overall Length Width Total Filter Depth Transition
SYSTEM Detention
S.A. (m2) S.A. (m2) (m) (m) Depth (m) (m) Layers (m)
Depth (m)
Bio Basin 1 25 47 6.25 4 0.8 0.5 0.3 0.3
Bio Basin 2 211 275 0.8 0.5 0.3 0.3
Bio Basin 3 150 202 0.8 0.5 0.3 0.3
Road Bio
10 10 4 2.5 0.65 0.4 0.25 0.1
Basin 1a
Road Bio
15 15 6 2.5 0.65 0.4 0.25 0.1
Basin 1b
Road Bio
10 10 4 2.5 0.65 0.4 0.25 0.1
Basin 2
Bio Swale 1 97 97 80 1.2 0.65 0.4 0.25 0.0
Bio Swale 2 82 82 70 1.2 0.65 0.4 0.25 0.0
Raingardens
(a total of 4 on 24 24 3 2 0.55 0.4 0.25 0.15
site)
Grassed
n/a 150 40 2.5 to 5 n/a n/a n/a n/a
Buffer
55 Lake MacDonald Drive – Stage 1 to 5 pg. 18
Page 19
PIT, PIPEWORK AND OUTLET —
FILTER MEDIA SANDY LOAM (TS2000 SAND)
CONFIGURATION AS PER SATURATED HYDRAULIC CONDUCTIVITY
IPWEAQ STD DWG 200mm/+R THICK PLANT WITH MACROPHYTES
WSUD-002 @ 8/m
LARGE COARSE SEDIMENT FOREBAY 2008
030 RIVER STONES OVER GEOTEXTILE
RL 2 ck
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DIAMETER SAND) DRAINAGE LAYER
(WASHED FINE GRAVEL 2—Smm WITH <2% FINES SATURATED
100@ SLOTTED
HYDRAULIC CONDUCTITY OF 4000mm/HR).
SECTION A - A
SEEPAGE PIPE TO
INLET OF O/F PIT
BIO BASIN 2 — 211m? FILTER SURFACE AREA
BIO BASIN 3 — 150m? FILTER SURFACE AREA
SEEPAGE PIPE
i
|
|
| 2.0m CENTRES
|
|
1.0. TO SURFACE WITH CAP
& CONC SURROUND
9100 SLOTTED.
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900x600 NORMAL GRATE & FRAME ON
OUTLET FROM O/F PIT TO LEGS” MIN 100 GAP TO PIT. CONTRACTOR
EXISTING WATERCOURSE TO MEGAPOXY ALL JOINS.
PLAN
project
Callaghan & Toth
Civil, Environmental &
Hydraulic Engineers
8/41 Sunshine Beach Road
PO BOX 2305
( NOOSA HEADS 4567
H Ph: 54749081 Fax: 54749041
= www.callaghanandtoth.com.au
57 LOTS RESIDENTIAL RECONFIGURATION
location
55 LAKE MACDONALD DRIVE / PEARSONS ROAD
COOROY
TYPICAL BIORETENTION BASIN
Figure 4.2
Scale: NTS Date: APRIL 2014
Page 19
Page 20
LENGTH VARIES KERB_& GUTTER TVVY 10 TO SURFACE WITH CONCRETE SURROUND KERBSIDE_ BASIN LAYOUT 600 x 600 OVERFLOW PIT UNDERGROUND DRAINAGE PIPE SCALE 1:100 SLOTTED RIGID PIPE RS BBIA = 10m? — RS BBIB = 15m? RS BB2 = 10m? 3.20 FOOTPATH IF REQUIRED KERB 0.60 2.00 0.60 2 3%> THe NY AVA AY AYA OES i 0.40 FILTER MEDIA (SANDY LOAM) (SATURATED HYDRAULIC CONDUCTIVITY 300mm/Hr) TRANSITION LAYER COARSE SAND 1mm @ DRAINAGE LAYER 2—5mm WASHED SCREENINGS 100@ SLOTTED RIGID PIPE STORMWATER DRAINAGE PIPE oj 0.20 POLY POOL LINER WITH WELDED JOINS ROADSIDE BASIN SECTION SCALE 1:50 SANDY LOAM PLANT — WITH NATIVE DROUGHT RESISTANT SHRUBS & GRASSES fl 1.5m | r— 450 x 450 GRATED OVERFLOW PIT 200 x 75 CCA TREATED PINE SLEEPERS 50mm 0.15m 0.4m 0.2m COARSE SAND 7 #150 OUTLET FROM O/F PIT TO INTERLOT DRAINAGE 9100 SLEEVED SEEPAGE PIPE TO INLET OF O/F PIT SECTION A — A ROOFWATER TANK OUTLET PIPE & PAVED 150 OUTLET 1.5m AREA DRAINAGE. OUTLET PIPE— FROM O/F PIT IL TO MATCH SAND SURFACE LEVEL TO INTERLOT DRAINAGE. 4.0m [ ; A t N T Ilodl Hit TI—T1 #100 SLEEVED SEEPAGE PIPE CoD DDD nd Tr ‘_ OVERFLOW PIT PRIVATE_RAIN GARDEN PLAN Project Callaghan & Toth Civil, Environmental & . . location Hydraulic Engineers 8/41 Sunshine Beach Road PO BOX 2305 NOOSA HEADS 4567 Ph: 54749081 Fax: 54749041 COOROY Mt 57 LOTS RESIDENTIAL RECONFIGURATION TYPICAL RAINGARDENS DETAILS 55 LAKE MACDONALD DRIVE / PEARSONS ROAD Figure 4.3 —_ www.callaghanandtoth.com.au Scale: NTS Date: APRIL 2014 Page 20 450 x 450 GRATED
Page 21
Callaghan & Toth
5. FLOODING ASSESSMENT SUMMARY
The flood study for the site was undertaken by Brisbane Stormwater Management Pty Ltd
(BSM). The results of the flood study and assessment are summarised below.
5.1 Existing Conditions
The site is traversed by two tributaries of Six Mile Creek, described as the eastern and western
tributaries.
The site is subject to ponding of floodwaters from the adjacent watercourses and the Q100 year
ARI flood levels (see Drawing Number 1225-33). The proposed lots are above the Q100 year
inundation line. The new road from Blue Wren Court is partly below the Q100 inundation line.
The flood assessment from BSM (See Appendix 4) reports on the hydrologic and hydraulic
performance of the site including upstream and downstream catchments.
5.2 Proposed Drainage System
Some of the increased stormwater runoff from the proposed residential areas is proposed to be
mitigated by conventional detention volumes in two bio-retention basins, but most of the
increased runoff is proposed to be attenuated by an increase in the floodway storage on the
site. The increased floodway storage will be achieved by deliberately “roughening” the
floodways (by revegetating the riparian zones, as required by Council) and by constructing a
restrictive footbridge across the eastern tributary to back-up the flood profiles in that tributary
floodway.
There will also be some regrading of the invert of the western tributary and the removal of an
artificial hump in the eastern tributary channel to achieve some more storage of flood flows
during the 100yr events.
The road surface level is proposed to tbe drained to an underground drainage system capable
of taking Q5 ARI flows. The overflow will discharge to the Bioretention Basins / Swales where it
will attenuate flows to pre-development conditions.
The Bioretention Basins have been modelled to act as a detention/infiltration basin. The basin
size and weir size is sufficient to reduce the increase in runoff for Q1 to Q100 storms, back to
predevelopment levels as shown in Table 5.1.
TABLE 5.1: Pre-Development and Post Development Discharges at node 15-16
Q1 Q2 Q5 Q10 Q100
Location
(m3/s) (m3/s) (m3/s) (m3/s) (m3/s)
Pre-Development 6.8 8.4 13.8 17.3 26.0
Post Development 6.7 8.3 13.5 17.2 25.1
55 Lake MacDonald Drive – Stage 1 to 5 pg. 21
Page 22
Callaghan & Toth
5.3 Western Tributary
It is proposed to reshape the existing western tributary to achieve the following:
Increase flood storage for the site
Reduce maintenance requirements for the watercourse
Reduce habitat for pests species, that is remove breeding ponds for mosquitos and
toads
Improve drainage through the site
The proposed works include:
Reshaping the low flow profile between the top of banks on both sides of the
watercourse. Drawing Number 1225-33 shows the area of earthworks.
Placement of a 1.5m wide rock lined invert for the length of the watercourse
Revegetation of the banks to replace the weeds removed on site
Maintain existing trees within the riparian zone of the watercourse
55 Lake MacDonald Drive – Stage 1 to 5 pg. 22
Page 23
Im
GD
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=
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5m RIPARIAN BUFFER FROM INVERT
5m RIPARIAN BUFFER FROM TOP OF BANK
[TT] tom riparian BUFFER FROM TOP OF BANK
Serer
LOT OR INFRASTRUCTURE INSIDE RIPARIAN BUFFER
(TOTAL AREA 340 SQUARE METRES)
ADDITIONAL RIPARIAN BUFFER OFFSET (PRELIMINARY AREA
580 SQUARE METRES, SUBJECT TO FLOOD MODELING)
EXISTING TOP OF BANK
FINAL Q100
——— --———___ PROPOSED LAY BACK TYPE INVERT LINE KERB &
CHANNEL M1 TO IPWEAQ STD DWG R-0080
=—= SW _ PROPOSED STORMWATER PIPE
+ 5 PROPOSED INTERLOT DRAINAGE PIPE WITH
—_ RAINGARDEN
+ —*— PROPOSED INTERLOT DRAINAGE PIPE
WITH PITS
PROPOSED BIORETENTION BASIN
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WESTERN TRIBUTARY a
WESTERN BANK — RIPARIAN BUFFER AREA
PLANT AREA TO ACHIEVE PLANT DENSITY OF
1 PLANT/1.5m?. CURRENTLY RIPARIAN AREA
FROM TOP OF BANK LIMITED TO GRASS
NATURE VEGETATION PRESENT ON BANKS
7 = Fao |
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ACTIVE
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$— ~~ x Fa100
FLUSH KERB ON
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EASTERN TRIBUTARY ;
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RIPARIAN MAPPING DOWNSTREAM
OF THIS POINT, STREAM BANK
USED FOR START OF BUFFER
26
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BEHIND LOTS FoR,
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ACCESS OR SERVICES
RP1 73883
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EASTERN BANK — RIPARIAN BUFFER AREA ‘
PLANT 70% OF AREAS TO ACHIEVE PLANT
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A
12
100
NO RIPARIAN MAPPING DOWNSTREAM
OF THIS POINT, STREAM INVERT |.
USED FOR START OF BUFFER | »
a
PURPLE AREA — INFILL PLANTING | |
REQUIRED FOR 30% OF AREA 10 N
ACHIEVE 1 PLANT/1.5m?
( Callaghan & Toth )
Civil, Environmental &
Hydraulic Engineers
PO BOX 2305
NOOSA HEADS 4567
i! 8/41 Sunshine Beach Road
=| Phone 54749081, Fax 54749041
www.callaghanandtoth.com.au
designed | ADT datum AHD DERIVED
drown BM ye
PS
checked | AH Origin (B.M.) RL *
approved
SURVEYED _BY
MAX WATTERSION & ASSOCIATES
PHONE 54 426 121
a
(SS
project
PROPOSED 31 LOT SUBDMSION
55 LAKE MacDONALD DRIVE
COOROY
Client
VALKEV PTY LTD
$d
_O——————————L————,
title
RIPARIAN ZONES STAGE 3 & 5
—_
_—_—————————————————————.
LOT 136 on MCH978
Parish of TEWANTIN
County of MARCH
SUNSHINE COAST COUNCIL
Locality of LAKE MacDONALD
Ce )
_—————————————————
SCALE
0.5 10.15 20 25 Meters 50
SS
scale SCALE SHOWN IS ORIGINAL DRAWING SCALE
( DO_NOT SCALE FROM THIS DRAWING
1:1000(A3) USE ONLY DIMENSIONS PROVIDED
REVISIONS
re detai
~|
FILES
COMPUTER DIRECTORY
X:\JOBS\CT Projects in progress\1225 30 lots
lake MacDonald Drive\\Design\Current_DWG—BASE
PRELIMINARY
Sheet 1 of 10 sheets
drawing number
1225-33
date 10-3-14 yy,
Page 24
Callaghan & Toth
6. CONCLUSIONS & RECOMMENDATIONS
An integrated water management approach has been used to assess the site’s stormwater
requirements and water management needs. In summary:
The proposed reconfiguration at 55 Lake MacDonald Drive and Pearsons Road from
four (4) lots into Fifty-seven (57) lots can be treated by a stormwater treatment train
consisting of:
o One medium Bioretention Basin (BioBasin 1)(already completed for Stage 1 i.e. Lots
1 to 4),
o Two large Bioretention Basins located in park treating runoff from Lots 5 to 16 and
associated road reserve for BioBasin 3 and treating runoff from Lot 33 to 57 for
BioBasin 2.
o Three small Roadside Bio Basins treating runoff from Lots 20 to 25 and associated
road reserve,
o Two Bioretention swales treating runoff from Lots 17,19, 29 to 32 and associated
road reserve,
o Three Raingardens for Lots 26, 27 & 28, and
o A grassed buffer for the road joining the new development to Blue Wren Place.
This proposed stormwater treatment train achieves the current best practice load based
reduction targets as prescribed in the Water by Design Deemed to Comply Solutions –
Stormwater Quality Management (South East Queensland) version 1.0 – Table A-2
The new lots have sufficient flood free areas to build residential infrastructure in
accordance with Council’s requirements.
The increased flood storage achieved with the measures:
o Detention volume in Bio Basins 2 and 3,
o Watercourse reshaping for the Western tributary,
o Revegetation of riparian areas to “roughen” the catchment, and
o Constructing a restrictive footbridge across the eastern tributary;
Allows attenuation of the runoff concentrations back to Pre Development levels and so
the development will not have an impact on the hydrology of the downstream receiving
waters.
55 Lake MacDonald Drive – Stage 1 to 5 pg. 24
Page 25
Callaghan & Toth APPENDIX 1 - Preliminary Stormwater Quality Management Plan 55 Lake MacDonald Drive – Stage 1 to 5 pg. A
Page 26
Maintenance Manual -— Lake MacDonald Drive - Stormwater Treatment Devices
Page 27
1.0 INTRODUCTION Stormwater treatment systems are designed with the intent to remove pollutants from stormwater piror to it entering local waterways. The systems commonly used include bioretention basins, raingardens, kerbside bioretention pits, and bioretention swales. Stormwater is directed to these systems via piped systems or overland with breaks in kerbs or swales directing water to enter the treatment system. Treated stormwater is collected at the base of the system via perforated pipeswhich are located in a gravel drainage layer. The treated stormwater is discharged to the local waterways or collected for reuse. Figure 1 below shows a concept illustration of a raingarden or bioretention tree pit illustrating stormwater flow pathways and subsurface infrastructure requiring maintenance.
Page 28
2.0 LONGTERM MAINTENANCE Three key elements in the design and construction of raingardens and bioretention tree pits have been identified that strongly influence the amount of long term maintenance that is required. The elements are: Correct filter media specification and installation Dense vegetation cover Protection during construction phases The importance of these key elements is described in more detail below. 2.1 Filter media The filter media for the raingarden or bioretention systems must meet certain specifications. It is crucial that the filter media installed maintains its hydraulic conductivity (i.e. it’s ability to pass water through the media) in the long term. When an inappropriate filter media is installed (e.g. it contains high levels of fine silt + clay materials) it may result in compaction or even structural collapse of the media. This leads to a substantial reduction in the treatment capacity of the system because water will not filter through the media but will pond on the surface instead and spill out through the overflow. A symptom of this compaction is often the loss of vegetation within the raingarden or tree pit. Similarly, the filter media must be correctly installed with an appropriate level of compaction during installation. Guidelines currently recommend that filter media be lightly compacted during installation to prevent migration of fine particles. In small systems, a single pass with a vibrating plate should be used to compact the filter media, while in large systems, a single pass with roller machinery (e.g. a drum lawn roller) should be performed (FAWB 2008). 2.2 Vegetation cover Nutrients have been identified as a key pollutant in stormwater, particularly nitrogen and phosphorus. The nutrient removal efficiency of raingardens and bioretention systems is related to the root structure and density of the plants within the system. Early analysis carried out by FAWB suggests that dense fibrous roots provide the most efficient pollutant removal. Further, as plants mature and their roots penetrate the filter media they play a role in maintaining the hydraulic conductivity of the media. Root growth helps to maintain the surface porosity and the infiltration capacity of the filter media. As a result, it is important that dense vegetation cover is established at an early stage to prevent compaction or surface sealing by promoting extensive root penetration. Some bioretention tree pits are designed without understorey vegetation. In these instances, it is likely that additional maintenance will be required to maintain the porosity of the surface of the filter media (e.g. physical removal of any fine sediments accumulating on the surface). 2.3 Protection during construction phases Protection of biofiltration systems during construction allows for good plant establishment and prevents disturbance or scour of the filter media surface. It is also important to protect the biofiltration system from heavy sediment loads, or other wash off (e.g. cement washings), during
Page 29
any construction in the catchment to prevent clogging of the surface of the filter media (see
Section 3 for more detail).
3.0 ESTABLISHMENT PHASE MAINTENANCE
A number of maintenance activities have been identified that are, in most cases, only required
during the establishment phase of a raingarden or tree pit. The end of the establishment phase
can be defined by the completion of both of the following:
i. The plant establishment – where plants are suitably established to no longer require
irrigation and are close to their mature height and/or when larger trees no longer require
tree stakes for support. This period is typically 18 to 24 months.
ii. The raingarden or tree pit is completely connected to its intended catchment and the
catchment is no longer under construction (therefore there is less risk of high sediment
loads or other contaminants, such as cement washings or fine clay sediments, being
washed onto the surface of the filter media and causing clogging). It is also important that
the entire catchment is connected to ensure adequate water availability for plants under
normal climatic conditions.
3.1 Protection of filter media during construction
Construction sites usually generate very high loads of sediment in stormwater runoff. These
exceptionally high loads can cause the filter media within a raingarden or tree pit to become
clogged or blocked. Blockage may occur as a result of the accumulation of fine sediment on the
surface; this can sometimes be manually removed. Accumulation of fine sediment may also
occur in a layer deeper within the filter media, usually resulting in the need to remove and replace
the filter media. To protect the filter media while construction activities are occurring in the
catchment, at least one of the following precautions should be taken:
1. Keep the raingarden or tree pit off-line during this period to prevent any stormwater
entering– Note: adequate alternative sediment control measures must also be installed
during construction to prevent heavy sediment loads being discharged directly to the
stormwater system while the raingarden or tree pit is off-line.
2. Delay final landscaping and protect system by covering the entire bioretention surface
with geofabric (and turf or gravel if desired for aesthetic purposes) as shown in Figure 2
(left).
3. Temporarily partition the bioretention system, creating a sacrificial sediment forebay. This
allows the vegetation to establish in the rest of the system while the sacrificial sediment
forebay at the inlet is protected using geofabric and turf as described above and shown in
Figure 2 (right). This approach is best suited when the over flow pit is located close to the
inlet zone.
Page 30
3.2 Irrigation Plants and trees in raingardens and tree pits will probably require irrigation during the establishment phase. Irrigation should be applied directly to the surface of the filter media. The use of Ag pipes for irrigating young trees is not recommended as it creates a short circuit pathway, or preferential flow path, for stormwater. As illustrated in Figure 3, the stormwater flows straight down the Ag pipes and into the drainage layer at the base where it is conveyed downstream to the conventional stormwater system, effectively bypassing any pollutant removal processes that occur as the stormwater filters through the soil media. Figure 3. Concept illustration showing how Ag pipes installed for tree watering can result in short circuiting and reduced stormwater treatment. 3.3 Tree stake removal Tree stakes are often used to support young trees planted into the filter media of raingardens or tree pits. Once the trees are adequately established the stakes should be removed and the holes filled in with filter media. Failure to fill in the holes will result in the creation of a short circuit pathway, or preferential flow path, for stormwater. Instead of ponding on the surface of the raingarden, the holes left behind after the stakes are removed allow water to bypass the filter media and drain directly into the drainage layer at the base of the cell, effectively bypassing any pollutant removal processes.
Page 31
4.0 MAINTENANCE MANUAL
4.1 BIORETENTION SYSTEMS MAINTENANCE PROCEDURES
Objective To maintain the bioretention systems to ensure that it continues to remove pollutants from stormwater runoff, as
intended during the design phase including:
Bioretention Basins 1, 2 and 3
Bioretetnion Swales 1 and 2
Roadside BioBasins 1a, 1b and 2
Actions Description Responsibility Timeframe
General Remove accumulated litter / debris to pond and grates Developer Every three months for first
Maintenance year of operation – during
Remove accumulated sediments at inlet On-maintenance period
Remove impermeable layer if water ponds for more than a
few hours
Remove weeds and dead plants
Replace plants where necessary
Water plants as necessary
Reinstate areas that have eroded and holes in media
Ensure energy dissipation at entry and exit points is adequate
and repair if necessary
Control erosion and sediment loss upstream or within system
where necessary
Check builders working upstream block inlet to biopod with
filter bags and ring edge with sediment fence. If not compliant,
ring building compliance officer.
Following Off- Remove accumulated litter / debris to pond and grates Council Every six months (or as
Page 32
maintenance necessary) following first
Remove accumulated sediments at inlet
year.
Remove impermeable layer (such as oily or clayey sediment)
if water ponds for more than a few hours
Remove weeds and dead plants
Replace plants where necessary (8-10 plants per m2 is
required). Ensure even spacing of plants.
Water plants as necessary
Check if a small clear flow is discharging from seepage pipe
to overflow pit after soaking rain. Repair blockages in pipes if
necessary
Treat plants for disease, pests etc.
Water plants as necessary
Reinstate areas that have eroded and holes in media
Ensure energy dissipation at entry and exit points is adequate
and repair if necessary
Ensure builder is aware that when working upstream they are
to block inlet to biopod with filter bags and ring edge with
sediment fence.
Every ten years Remove the top 50mm of filter material Council Every ten years (or as
necessary)
If after the removal of the top 50mm of filter material the water
ponds for more than 2 hours after inflow stops. Test hydraulic
conductivity of filter media (Replace filter media if conductivity
is below the minimum of 50 mm/hr).
Inspections Carry out three monthly inspections of the system and inspect Council Every six months –or as
the following: necessary.
o Sediment build up on surface
o Impermeable layer (such as oily or clayey sediment)
build up
Page 33
o Organic matter build up
o Health of vegetation, presence of disease, pests,
stunted growth, etc
o Pondage during storms not infiltrating into the sand
o Erosion at the outlet or inlet
Reporting Keep a record of inspections and actions undertaken using Council
FAWB form 4.2.5
Record environmental incidents and corrective actions using
FAWB form 4.2.5
Page 34
4.2 RAINGARDEN MAINTENANCE PROCEDURES
Objective To maintain the raingarden systems to ensure that it continues to remove pollutants from stormwater runoff, as
intended during the design phase.
Actions Description Responsibility Timeframe
General Remove accumulated litter / debris to pond and grates Developer Every three months for first
Maintenance year of operation – during
Remove accumulated sediments at inlet On-maintenance period
Remove impermeable layer if water ponds for more than a
few hours
Remove weeds and dead plants
Replace plants where necessary
Water plants as necessary
Reinstate areas that have eroded and holes in media
Ensure energy dissipation at entry and exit points is adequate
and repair if necessary
Control erosion and sediment loss upstream or within system
where necessary
Check builders working upstream block inlet to biopod with
filter bags and ring edge with sediment fence. If not compliant,
ring building compliance officer.
Following Off- Remove accumulated litter / debris to pond and grates Householder Every six months (or as
maintenance necessary) following first
Remove accumulated sediments at inlet year.
Remove impermeable layer (such as oily or clayey sediment)
if water ponds for more than a few hours
Remove weeds and dead plants
Page 35
Replace plants where necessary (6-10 plants per m2 is
required). Ensure even spacing of plants.
Water plants as necessary
Check if a small clear flow is discharging from seepage pipe
to overflow pit after soaking rain. Repair blockages in pipes if
necessary
Treat plants for disease, pests etc.
Water plants as necessary
Reinstate areas that have eroded and holes in media
Ensure energy dissipation at entry and exit points is adequate
and repair if necessary
Ensure builder is aware that when working upstream they are
to block inlet to biopod with filter bags and ring edge with
sediment fence.
Every ten years Remove the top 50mm of filter material Householder Every ten years (or as
necessary)
If after the removal of the top 50mm of filter material the water
ponds for more than 2 hours after inflow stops. Test hydraulic
conductivity of filter media (Replace filter media if conductivity
is below the minimum of 50 mm/hr).
Inspections Carry out three monthly inspections of the system and inspect Householder Every three months –or as
the following: necessary.
o Sediment build up on surface
o Impermeable layer (such as oily or clayey sediment)
build up
o Organic matter build up
o Health of vegetation, presence of disease, pests,
stunted growth, etc
o Pondage during storms not infiltrating into the sand
Page 36
o Erosion at the outlet or inlet
Reporting Keep a record of inspections and actions undertaken using Householder
FAWB form 4.2.5
Record environmental incidents and corrective actions using
FAWB form 4.2.5
Page 37
APPENDIX A FAWB FORM 4.2.5 4.2.5 FORM (REGULAR INSPECTION & MAINTENANCE) Location Raingarden/Tree Pit Site Visit Date: Site Visit By: Weather: Routine Inspection Oo Complete section 1 (below) Purpose of the Site Visit Routine Maintenance oO Complete sections 1 and 2 (below) NOTE: Where maintenance is required (‘yes’ in Section 2), details should be recorded in the ‘Additional Comments’ section at the end of this document. 1. Filter media *In addition to regular inspections, it is recommended that inspection for damage and blockage is made after significant rainfall events that might occur once or twice a year. Section 1 Section 2 Maintenance Required? Maintenance Performed Yes No Yes No Filter media (CIRCLE — pooling water/accumulation of silt & clay layer/scour/holes/sediment build up) oO oO oO oO Litter (CIRCLE - large debris/accumulated vegetation/anthropogenic) oO oO oO oO 2. Vegetation Vegetation health (C/RCLE - signs of disease/pests/poor growth) oO oO oO oO Vegetation densities (CIRCLE — low densities- infill planting required) oO oO oO Oo Build up of organic matter, leaf litter (C/RCLE - requires removal) Oo oO oO Oo Weeds (CIRCLE - isolated plants/infestation) (SPECIES - . Oo oO oOo oOo
Page 38
3. Pits, pipes and inflow areas Section 1 Section 2 Maintenance Required? Maintenance Performed? Yes No Yes No Perforated pipes (C/RCLE — full blockage/partial blockage/damage) oO oO oO oO Inflow areas (CIRCLE — scour/excessive sediment deposition/litter blockage) oO oO oO oO Overflow grates (CIRCLE — damage/scour/blockage) oO oO oO oO Pits (CIRCLE — poor general integrity/sediment build-up/litter/blockage) oO oO oO oO Other stormwater pipes and junction pits (C/RCLE — poor general integrity/sediment build-up/litter/blockage) oO oO oO oO 4, Submerged zone Section 1 Section 2 Maintenance Required? Maintenance Performed? Yes No Yes No Weir/up-turned pipe (C/RCLE — full blockage/partial blockage/damage) oO oO oO oO Water level (C/RCLE — at design level/drawn down) SOME DRAWDOWN DURING DRY PERIODS IS EXPECTED Oo oO Oo Oo 5. Additional Comments
Page 39
| | - | Callaghan & Toth APPENDIX 2 - MUSIC Results 55 Lake MacDonald Drive — Stage 1 to 5 pg. B
Page 40
Source nodes Road Lotito4- Lotito4- LotSto16- Lot5to16- Roadways- Lot 20 to25- Lot 20 to25 - Location reserve Roof Area Yard Yard Roof Area Masonry St Roof Area Yard ID 1 2 3 6 7 8 9 10 UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource Node Type Node Node Node Node Node Node Node Node Total Area (ha) 0.051 0.08 0.107 0.717 0.3 0.185 0.15 0.275 Area Impervious (ha) 0.03063777 0.07991325 0.02170976 0.1454757 0.2996747 0.111137 0.14983735 0.05579612 Area Pervious (ha) 0.02036223 —8.67E-05 0.08529024 0.5715243 0.0003253 0.073863 :0.00016265 0.21920388 Field Capacity (mm) 200 200 200 200 200 200 200 200 Pervious Area Infiltration Capacity coefficient - a ait att ait ait att ait ait att Pervious Area Infiltration Capacity exponent - b 5 5 5 5 5 5 5 5 Impervious Area Rainfall Threshold (mm/day) 1 1 1 1 1 1 1 1 Pervious Area Soil Storage Capacity (mm) 500 500 500 500 500 500 500 500 Pervious Area Soil Initial Storage (% of Capacity) 10 10 10 10 10 10 10 10 Groundwater Initial Depth (mm) 50 50 50 50 50 50 50 50 Groundwater Daily Recharge Rate (%) 28 28 28 28 28 28 28 28 Groundwater Daily Baseflow Rate (%) 27 27 27 27 27 27 27 27 Groundwater Daily Deep Seepage Rate (%) 0 0 0 0 0 0 0 0 Stormflow Total Suspended Solids Mean (log mg/L) 2.43 1.3 2.18 2.18 1.3 2.43 13 2.18 Stormflow Total Suspended Solids Standard Deviation (log mg/L 0.39 0.39 0.39 0.39 0.39 0.39 0.39 0.39 Stormflow Total Suspended Solids Estimation Method Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic _—_ Stochastic Stormflow Total Suspended Solids Serial Correlation 0 0 0 0 0 0 0 0 Stormflow Total Phosphorus Mean (log mg/L) -0.3 -0.89 -0.47 -0.47 -0.89 -0.3 -0.89 -0.47 Stormflow Total Phosphorus Standard Deviation (log mg/L) 0.31 0.31 0.31 0.31 0.31 0.31 0.31 0.31 Stormflow Total Phosphorus Estimation Method Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic _—_ Stochastic Stormflow Total Phosphorus Serial Correlation 0 0 0 0 0 0 0 0 Stormflow Total Nitrogen Mean (log mg/L) 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 Stormflow Total Nitrogen Standard Deviation (log mg/L) 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.23 Stormflow Total Nitrogen Estimation Method Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic _—_Stochastic Stormflow Total Nitrogen Serial Correlation 0 0 0 0 0 0 0 0 Baseflow Total Suspended Solids Mean (log mg/L) 1 0 1 1 0 1 0 1 Baseflow Total Suspended Solids Standard Deviation (log mg/L) 0.34 0 0.34 0.34 0 0.34 0 0.34 Baseflow Total Suspended Solids Estimation Method Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Baseflow Total Suspended Solids Serial Correlation 0 0 0 0 0 0 0 0 Baseflow Total Phosphorus Mean (log mg/L) -0.97 0 -0.97 -0.97 0 -0.97 0 -0.97 Baseflow Total Phosphorus Standard Deviation (log mg/L) 0.31 0 0.31 0.31 0 0.31 0 0.31 Baseflow Total Phosphorus Estimation Method Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Baseflow Total Phosphorus Serial Correlation 0 0 0 0 0 0 0 0 Baseflow Total Nitrogen Mean (log mg/L) 02 0 0.2 02 0 0.2 0 0.2 Baseflow Total Nitrogen Standard Deviation (log mg/L) 02 0 0.2 02 0 0.2 0 0.2 Baseflow Total Nitrogen Estimation Method Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic _—_ Stochastic Baseflow Total Nitrogen Serial Correlation 0 0 0 0 0 0 0 0 OUT - Mean Annual Flow (ML/yr) 0.478 1.02 0.643 431 3.82 1.73 1.91 1.65 OUT - TSS Mean Annual Load (kg/yr) 177 30.5 116 814 114 655 57.2 309 OUT - TP Mean Annual Load (kg/yr) 0.292 0.167 0.241 1.61 0.634 1.09 0.316 0.621 OUT - TN Mean Annual Load (kg/yr) 1 2.11 13 8.72 8.02 3.6 4.01 3.36 OUT - Gross Pollutant Mean Annual Load (kg/yr) 118 24 11.8 79.2 90.1 42.8 45.4 30.4 Rain In (ML/yr) 0.711512 1.1161 1.49278 10.003 4.18536 2.58098 2.09268 (3.83658 ET Loss (ML/yr) 0.231547 0.0962114 0.84291 5.64827 0.360791 0.839924 0.180395 2.16635 No Imported Data Source nodes USTM treatment nodes BioBasin 1 - 25m2 10m2 Stg1(Comple BioBasin3- Bioretention Roadside Roadside —_Raingardens Bioretention Location ted) Park Swale2 BioBasin1 BioBasin2_ x3. Swale 1 Swale 1 ID 4 5 14 15 17 20 27 28 BioRetention BioRetention BioRetention BioRetention BioRetention BioRetention BioRetention Node Type NodeV4 NodeV4 —- NodeV4. ss NodeV4.~—s NodeV4. = NodeV4. = NodeV4.~—s SwalleNode. Lo-flow bypass rate (cum/sec) 0 0 0 0 0 0 0 0.005 Hi-flow bypass rate (cum/sec) 100 100 100 100 100 100 100 Inlet pond volume Area (sqm) 46.69 202 82 25 10 18 97 Extended detention depth (m) 03 0.3 0 0.4 0.4 0.15 0 0.65 Overflow weir width (m) 3 3 1 1 1 1 1 a“ Weir Coefficient 17 1.7 17 17 1.7 17 17 Number of CSTR Cells 3 3 3 3 3 3 3 10 Total Suspended Solids - k (m/yr) 8000 8000 8000 8000 8000 8000 8000 8000 Total Suspended Solids - C* (mg/L) 20 20 20 20 20 20 20 20 Total Suspended Solids - C** (mg/L) 14 Total Phosphorus - k (m/yr) 6000 6000 6000 6000 6000 6000 6000 6000 Total Phosphorus - C* (mg/L) 0.13 0.13 0.13 0.13 0.13 0.13 0.13 0.13 Total Phosphorus - C** (mg/L) 0.13 Total Nitrogen - k (m/yr) 500 500 500 500 500 500 500 500 Total Nitrogen - C* (mg/L) 14 1.4 1.4 14 1.4 1.4 14 1.4 Total Nitrogen - C** (mg/L) 1.4 Threshold Hydraulic Loading for C** (m/yr) 3500 Horizontal Flow Coefficient 3 3 3 3 3 3 3 Reuse Enabled Off Off Off Off Off Off Off Off Annual Demand Enabled Off Off Off Off Off Off Off Off Daily Demand Enabled Off Off Off Off Off Off Off Off Custom Demand Enabled Off Off Off Off Off Off Off Off Filter area (sqm) 25 150 82 25 10 18 97 Filter perimeter (m) 20.5 47 172.4 24 14 33 162.4 Filter depth (m) 05 0.5 04 04 04 04 04 Filter Median Particle Diameter (mm) Saturated Hydraulic Conductivity (mnvhr) 200 200 200 200 200 200 200 Infiltration Media Porosity 0.35 0.35 0.35 0.35 0.35 0.35 0.35 Lot 29 to 32 - Lot 29 to 32- North section of Roadway Roadway Joining Road from Blue Lot 33-57- Lot33-57- fromBlue —_ from Blue Roadways Yard Roof Area Roadways Lot 18 - Yard Yard Wren Place Wren Place RoofArea Yard Wren Place Wren Place 1 12 13 30 31 32 33 36 UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource UrbanSource Node Node Node Node Node Node Node Node Node 0.08 0.177 01 0.129 0.625 1.065 0.461 0.034 0.04805925 0.03591241 0.09989157 0.05198779 0.07700938 0.62432229 0.21608316 0.27867875 0.02042518 0.03194075 0.14108759 0.00010843 0.03401221 0.05199062 0.00067771 0.84891684 0.18232125 0.01357482 200 200 200 200 200 200 200 200 ait 211 ait ait 211 211 ait 211 5 5 5 5 5 5 5 5 1 1 1 1 1 1 1 1 500 500 500 500 500 500 500 500 10 10 10 10 10 10 10 10 50 50 50 50 50 50 50 50 28 28 28 28 28 28 28 28 27 27 27 27 27 27 27 27 0 0 0 0 0 0 0 0 2.43 2.18 1.3 2.43 1.3 2.18 2.43 2.43 0.39 0.39 0.39 0.39 0.39 0.39 0.39 0.39 Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic | Stochastic Stochastic 0 0 0 0 0 0 0 0 -0.3 -0.47 -0.89 -0.3 -0.89 -0.47 -0.3 -0.3 0.31 0.31 0.31 0.31 0.31 0.31 0.31 0.31 Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic | Stochastic Stochastic 0 0 0 0 0 0 0 0 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.26 0.23 0.23 0.23 0.23 0.23 0.23 0.23 0.23 Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic | Stochastic Stochastic 0 0 0 0 0 0 0 0 1 1 0 1 0 1 1 1 0.34 0.34 0 0.34 0 0.34 0.34 0.34 Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic | Stochastic Stochastic 0 0 0 0 0 0 0 0 -0.97 -0.97 0 -0.97 0 -0.97 -0.97 -0.97 0.31 0.31 0 0.31 0 0.31 0.31 0.31 Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic | Stochastic Stochastic 0 0 0 0 0 0 0 0 0.2 0.2 0 0.2 0 0.2 0.2 0.2 0.2 0.2 0 0.2 0 0.2 0.2 0.2 Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic Stochastic | Stochastic Stochastic 0 0 0 0 0 0 0 0 0.75 1.06 1.27 1.21 7.97 6.4 4.32 0.319 296 202 38.1 458 238 1.21E+03 1.62E+03 120 0.463 0.396 0.213 0.733 1.33 2.45 2.66 0.199 1.55 2.18 2.63 2.48 16.4 12.9 8.93 0.66 18.5 19.6 30 29.9 188 118 107 7.87 1.1161 2.46936 1.39512 1.79971 8.71951 14.8581 6.43151 0.474341 0.36321 1.39434 0.120263 0.585679 0.751637 8.38967 2.09301 0.154365 BioBasin 2 - Swale 2 Park Raingardens Buffer 29 34 35 BioRetention BioRetention SwaleNode NodeV4 NodeV4 BufferNode 0.004 0 0 100 100 274 6 102.125896 0.65 0.3 0.15 3 1 17 1.7 10 3 3 8000 8000 8000 20 20 20 14 6000 6000 6000 0.13 0.13 0.13 0.13 500 500 500 1.4 1.4 1.4 1.4 3500 3 3 Off Off Off Off Off Off Off Off Off Off Off Off Off Off Off Off 211 6 60 10 0.5 0.4 200 200 0.35 0.35
Page 41
Length (m) 80 70
Bed slope 0.005 0.005
Base Width (m) 1.2 1.2
Top width (m) 4.1 4.1
Vegetation height (m) 0.25 0.25
Vegetated Vegetated Vegetated Vegetated Vegetated Vegetated Vegetated Vegetated Vegetated
with Effective with Effective with Effective with Effective with Effective with Effective with Effective with Effective with Effective
Nutrient Nutrient Nutrient Nutrient Nutrient Nutrient Nutrient Nutrient Nutrient
Removal Removal Removal Removal Removal Removal Removal Removal Removal
Vegetation Type Plants Plants Plants Plants Plants Plants Plants Plants Plants
Total Nitrogen Content in Filter (mg/kg) 400 400 400 400 400 400 400 400 400
Orthophosphate Content in Filter (mg/kg) 50 50 50 50 50 50 50 50 50
Is Base Lined? Yes No No No No Yes No No No
Is Underdrain Present? Yes Yes Yes Yes Yes Yes Yes Yes Yes
Is Submerged Zone Present? No No No No No No No No No
Submerged Zone Depth (m)
B for Media Soil Texture 13 13 13 13 13 13 13 -9999 -9999 13 13 -9999
Proportion of upstream impervious area treated 0.5
Exfiltration Rate (mm/hr) 0 0 0 0 0 0 0 0 0 0 0 0
Evaporative Loss as % of PET
Depth in metres below the drain pipe
IN - Mean Annual Flow (ML/yr) 2.14 9.87 3.55 4.31 0.807 1.71 2.11 1.9 3.36 18.7 0.763 0.319
IN - TSS Mean Annual Load (kg/yr) 324 1.58E+03 699 662 307 166 484 39 111 3.06E+03 91.8 120
IN - TP Mean Annual Load (kg/yr) 0.699 3.33 1.34 1.4 0.494 0.45 0.897 0.255 0.515 6.44 0.222 0.199
IN - TN Mean Annual Load (kg/yr) 4.42 20.3 7.29 8.93 1.69 3.52 4.36 1.74 3.7 38.3 1.56 0.66
IN - Gross Pollutant Mean Annual Load (kg/yr) 47.7 212 79.5 94 19.9 36.5 48.4 0 0 412 15.7 7.87
OUT - Mean Annual Flow (ML/yr) 2.08 9.5 3.36 4.26 0.783 1.67 1.9 1.9 3.36 18.2 0.749 0.319
OUT - TSS Mean Annual Load (kg/yr) 44.9 247 111 256 58.3 49.2 39 20.2 54.5 545 34 76.5
OUT - TP Mean Annual Load (kg/yr) 0.278 1.3 0.515 0.809 0.165 0.257 0.255 0.229 0.436 2.7 0.13 0.152
OUT - TN Mean Annual Load (kg/yr) 1.98 8.94 3.7 5.79 0.907 1.91 1.74 1.75 3.67 18 0.925 0.593
OUT - Gross Pollutant Mean Annual Load (kg/yr) 0 0 0 0 0 0 0 0 0 0 0 7.87
Flow In (ML/yr) 2.14031 9.86409 3.54659 4.31309 0.806372 1.71289 2.11429 1.90084 3.35972 18.6825 0.763022 0.318748
ET Loss (ML/yr) 0.0610429 0.363982 0.186365 0.0586939 0.0229932 0.04166 0.211811 0 0 0.513396 0.0140031 0
Infiltration Loss (ML/yr) 0 0 0 0 0 0 0 0 0 0 0 0
No Generic treatment nodes
Other nodes
Location Junction - Ck off
Junction
Blue Wren
- eastPlace
Receiving
west gullyNode
Junction
- Tributary
westofside
Sixstg5
Mile gully
Ck
ID 21 38 39 40
Node Type JunctionNode JunctionNode ReceivingNode JunctionNode
IN - Mean Annual Flow (ML/yr) 11.4 13.3 42.8 18.2
IN - TSS Mean Annual Load (kg/yr) 500 341 1.39E+03 545
IN - TP Mean Annual Load (kg/yr) 1.92 1.84 6.46 2.7
IN - TN Mean Annual Load (kg/yr) 13.6 12.8 44.5 18
IN - Gross Pollutant Mean Annual Load (kg/yr) 7.87 0 7.87 0
OUT - Mean Annual Flow (ML/yr) 11.4 13.3 0 18.2
OUT - TSS Mean Annual Load (kg/yr) 500 341 0 545
OUT - TP Mean Annual Load (kg/yr) 1.92 1.84 0 2.7
OUT - TN Mean Annual Load (kg/yr) 13.6 12.8 0 18
OUT - Gross Pollutant Mean Annual Load (kg/yr) 7.87 0 0 0
% Load Reduction 4.17 3.41 3.34 2.77
TSS % Load Reduction 78.9 83.5 81.5 82.2
TN % Load Reduction 44.3 54.6 51.1 52.8
TP % Load Reduction 57.8 59 58.2 58.1
GP % Load Reduction 97 100 99.2 100
Links
Location Drainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage LinkDrainage Link
Source node ID 12 13 16 19 18 1 3 2 8 6 7 15 17 24 25 26 27 28 14 29 31 32 33 9
Target node ID 14 14 17 20 20 4 4 4 5 5 5 21 21 27 27 27 28 21 29 21 34 34 34 15
Muskingum-Cunge Routing Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed Not Routed
Muskingum K
Muskingum theta
IN - Mean Annual Flow (ML/yr) 1.06 1.27 0.807 0.757 0.956 0.478 0.643 1.02 1.73 4.31 3.82 4.26 0.783 0.493 0.637 0.985 1.9 1.9 3.36 3.36 7.97 6.4 4.32 1.91
IN - TSS Mean Annual Load (kg/yr) 202 38.1 307 137 28.4 177 116 30.5 655 814 114 256 58.3 91.7 19.1 373 39 20.2 111 54.5 238 1.21E+03 1.62E+03 57.2
IN - TP Mean Annual Load (kg/yr) 0.396 0.213 0.494 0.291 0.158 0.292 0.241 0.167 1.09 1.61 0.634 0.809 0.165 0.185 0.106 0.605 0.255 0.229 0.515 0.436 1.33 2.45 2.66 0.316
IN - TN Mean Annual Load (kg/yr) 2.18 2.63 1.69 1.52 2 1 1.3 2.11 3.6 8.72 8.02 5.79 0.907 0.998 1.34 2.02 1.74 1.75 3.7 3.67 16.4 12.9 8.93 4.01
IN - Gross Pollutant Mean Annual Load (kg/yr) 19.6 30 19.9 13.9 22.5 11.8 11.8 24 42.8 79.2 90.1 0 0 9.06 15 24.3 0 0 0 0 188 118 107 45.1
OUT - Mean Annual Flow (ML/yr) 1.06 1.27 0.807 0.757 0.956 0.478 0.643 1.02 1.73 4.31 3.82 4.26 0.783 0.493 0.637 0.985 1.9 1.9 3.36 3.36 7.97 6.4 4.32 1.91
OUT - TSS Mean Annual Load (kg/yr) 202 38.1 307 137 28.4 177 116 30.5 655 814 114 256 58.3 91.7 19.1 373 39 20.2 111 54.5 238 1.21E+03 1.62E+03 57.2
OUT - TP Mean Annual Load (kg/yr) 0.396 0.213 0.494 0.291 0.158 0.292 0.241 0.167 1.09 1.61 0.634 0.809 0.165 0.185 0.106 0.605 0.255 0.229 0.515 0.436 1.33 2.45 2.66 0.316
OUT - TN Mean Annual Load (kg/yr) 2.18 2.63 1.69 1.52 2 1 1.3 2.11 3.6 8.72 8.02 5.79 0.907 0.998 1.34 2.02 1.74 1.75 3.7 3.67 16.4 12.9 8.93 4.01
OUT - Gross Pollutant Mean Annual Load (kg/yr) 19.6 30 19.9 13.9 22.5 11.8 11.8 24 42.8 79.2 90.1 0 0 9.06 15 24.3 0 0 0 0 188 118 107 45.1
Catchment Details
Catchment Name 1225_Cooroy 1992 - 2002_April2013_Version2
Timestep 6 Minutes
Start Date 1/01/1992
End Date 31/12/2001
Rainfall Station 40059 COOROY
ET Station User-defined monthly PET
Mean Annual Rainfall (mm) 1398
Mean Annual ET (mm) 1652
Page 42
Drainage Link 10 15 Not Routed 1.65 309 0.621 3.36 30.4 1.65 309 0.621 3.36 30.4 Drainage Link WW 15 Not Routed 0.75 296 0.463 1.55 18.5 0.75 296 0.463 1.55 18.5 Drainage Link 30 14 Not Routed 1.21 458 0.733 2.48 29.9 1.21 458 0.733 2.48 29.9 Drainage Link Not Routed 23 35 0.445 82.1 0.169 0.892 8.18 0.445 82.1 0.169 0.892 8.18 Drainage Link 22 35 Not Routed 0.319 9.66 5.30E-02 0.667 7.51 0.319 9.66 5.30E-02 0.667 7.51 Drainage Link Not Routed 36 37 0.319 120 0.199 0.66 7.87 0.319 120 0.199 0.66 7.87 Drainage Link Not Routed 37 a1 0.319 76.5 0.152 0.593 7.87 0.319 76.5 0.152 0.593 7.87 Drainage Link Not Routed 4 38 2.08 0.278 1.98 2.08 0.278 1.98 Drainage Link Not Routed 5 38 9.5 247 1.3 8.94 9.5 247 1.3 8.94 Drainage Link 20 38 Not Routed 1.67 49.2 0.257 1.91 1.67 49.2 0.257 1.91 Drainage Link Not Routed 38 39 13.3 341 1.84 12.8 13.3 341 1.84 12.8 Drainage Link Not Routed 21 39 11.4 500 1.92 13.6 7.87 11.4 500 1.92 13.6 7.87 Drainage Link Not Routed 34 40 18.2 545 27 18.2 545 27 Drainage Link Not Routed 40 39 18.2 545 27 18.2 545 27 Drainage Link Not Routed 35 Pal 0.749 34 0.13 0.925 0.749 34 0.13 0.925
Page 43
Callaghan & Toth APPENDIX 3 - Site Photos Western Tributary – looking from Blue Wren Court Western Tributary – opposite proposed Lot 20 55 Lake MacDonald Drive – Stage 1 to 5 pg. C
Page 44
Callaghan & Toth Western Tributary – opposite proposed Lot 30 Eastern Tributary – To the west of Stage 1 55 Lake MacDonald Drive – Stage 1 to 5 pg. D
Page 45
Callaghan & Toth Eastern Tributary – western bank Eastern Tributary – western bank – showing lack of vegetation from top of bank out 55 Lake MacDonald Drive – Stage 1 to 5 pg. E
Page 46
Callaghan & Toth APPENDIX 4 - BSM Flood Report 55 Lake MacDonald Drive — Stage 1 to 5 pg. F
Page 47
Brisbane Stormwater Management Pty Ltd
VALKEV PTY LTD
STORMWATER DETENTION AND FLOODING
FOR SUBDIVISION OF LOT2 ON RP173883
AND LOTS 135, 136 AND 137 ON MCH978
AT ELM STREET AND LAKE MACDONALD DRIVE
COOROY
30 APRIL 2014
Page 48
SUBDIVISION OF LOT 2 ON RP173883 AND LOTS 135, 136 AND 137 ON MCH 978
AT ELM STREET AND LAKE MACDONALD DRIVE, COOROY
STORMWATER DETENTION AND FLOODING REPORT
COMPILED FOR VALKEV P/L BY BRISBANE STORMWATER MANAGEMENT P/L
DOCUMENT CONTROL SHEET
Document Title: Stormwater Detention And Flooding For Subdivision Of Lot 2 On RP173883 And
Lots 135, 136 And 137 On MCH978, At Elm Street & Lake Macdonald Drive, Cooroy
Client: Valkev Pty Ltd
BSM Job No: 2013-08
Project Manager: Denis Ogle
Distribution:
Doc Filename Status Format Issued To Date
ValkevSDF.Doc Draft Pdf Callaghan & Toth P/L 28/4/14
BSM – Office 28/4/14
ValkevSDF.Doc Final Pdf & Callaghan & Toth P/L 30/4/14
Hardcopy BSM – Office Copy 30/4/14
Brisbane Stormwater Management P/L
92 Alkoomie St, PO Box 8119, Wynnum Nth, Q4178
Ph (07)33963383, Email [email protected]
Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 1
Page 49
List Of Contents
1. Summary 3
2. Introduction 4
3. Stormwater Detention Requirement 5
4. Stormwater Discharges To No 2 Pearsons Road 6
5. Runoff Rates To Floodway Model 8
5.1 Catchment Areas And Subdivision 8
5.2 Design Rainfall Data 8
5.3 Model Calibration 10
5.4 Linkage From Catchment Model To Floodway Model 11
6. Floodway Profiles, Pre-Development 13
7. Floodway Profiles, Post-Development 17
7.1 Mitigation Concept For Increased Stormwater Runoff 17
7.2 Model Simulation 17
7.3 Sensitivity Test 18
8. Certification 19
List Of Figures (following text)
1 Locality And Lot Plan
2 Urbs Models Of Stormwater Detention Requirement
3 Proposed Change In Discharge Scenarios To No 2 Pearsons Road
4 Catchment Subdivision For Pre-Development Urbs Model
5 Catchment Subdivision For Post-Development Urbs Model
6 XPStorm Hydraulic Model Network
7 Photographs Of Eastern Floodway On 25 November 2013
8 Photographs Of Western Floodway On 25 November 2013
9 Proposed Floodway Modifications
10 Longitudinal Floodway Profiles
11 Floodway Cross-Section Changes – West Tributary
12 Footbridge And Bio-Basin Schematics
13 Flood Levels And Flood Boundaries
Appendices
A. Design Rainfall Data
B. Rational Method Calculations Of Floodway Inflows, Pre-Development
C. Rational Method Calculations Of Floodway Inflows, Post-Development
D. Floodway Storage Volumes
Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 2
Page 50
1.0 SUMMARY
This analysis has found that the development’s stormwater detention requirement can be achieved by
enlarging the flood storage on the site, by the means shown on Figures 9 to 11 of this report, to augment
the small amount of conventional detention storage that can be gained in two bio-basins on the site (as in
Figure 12). The additional storage volumes generated by these works, after allowing for the small
amounts of flood storage that will be lost to filling of lot margins and active parkland, are compared to
the detention storages that would be required of a fully-conventional detention system, in Table S1:
Table S1: Comparison Of Pre-Development And Post-Development Floodplain Volumes (m3)
To Required Detention Volumes
1Year 2 Year 5 Year 10 Year 20 Year 50 year 100 Year
Pre-Development 5456 6184 8515 9927 11352 12986 14493
Floodway Storage
Post-Development 5781 6591 9349 11121 12976 14807 16240
Floodway Storage
Floodway Gain 325 407 834 1194 1624 1821 1747
Plus Bio-Basins 162 183 252 252 252 252 252
Less Active Park Fill -0 -0 -0 -0 -0 -18 -45
Nett Gain 487 590 1086 1446 1876 2055 1954
Req’d Extra Volume
(From Table 3) 395 525 770 910 1095 1370 1585
The abovementioned works, together with a minor regrading of the invert profile around node 5 (as also
shown on Figure 10) will result in the development having practically nil adverse impact on flood levels
on adjoining properties, as summarised in Tables 16 to 18 of this report. The only exception to this
generality is at node 23, just upstream of the site boundary in the western tributary, where the affluxes
will range from 0.02 metre in a 10 year storm to 0.05 metre in a 100 year storm. The western channel
between node 23 and the site boundary was designed in 2006 to be deliberately revegetated to a
Manning’s n of 0.15, as part of the adjoining Blue Wren Place development. That revegetation was
installed at the time of that development, but has since been removed, thereby reducing the present (“pre-
development”) Manning’s n in this area to about 0.04, consequently decreasing the flood levels at node
23 to about 0.4 metre below the original design levels. The post-development flood levels as a result of
Valkev’s development, while being 0.02 to 0.05 metre above the present levels, will nevertheless be at
least 0.3 metre below the original design levels for this area, and the quoted affluxes are therefore
suggested to be of no consequence. This is illustrated by the levels of the adjoining lot in Blue Wren
Place, which are marked on the longitudinal floodway profiles in Figure 10 of this report.
The works will also result in nil adverse impact on downstream peak flow rates, apart from a slight
increase in flows along the western tributary through the immediately adjoining downstream property
(No2 Pearsons Road). That increase on the adjoining property results in the deliberate diversion of local
runoff away from that adjoining property, and directly to the western floodway upstream of that property.
Downstream of the natural point of inflow to the floodway for that runoff, on the adjoining property, the
flows revert to their pre-development rates.
The consequent flood levels for design of the development are summarised in Tables 16 to 18 and in
Figures 13 of this report. A sensitivity test has identified the impact of uncontrolled floodplain regrowth
on the abovementioned design levels. The consequent 100 year flood levels are summarised in Table 21
and in Figures 13, and appropriate account should be taken of these possible flood levels when
considering appropriate design levels for the development.
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2.0 INTRODUCTION
This report describes Brisbane Stormwater Management P/L’s (BSM’s) stormwater detention and
flooding assessment of a proposed subdivision of Lot 2 on RP173883 and Lots 135, 136 and 137 on
MCH978, at Elm Street and Lake Macdonald Drive, Cooroy. The site locality and the proposed lot layout
are shown in Figure 1 of this report.
The site is traversed by two tributaries of Six Mile Creek, hereafter described as the eastern and western
tributaries. The catchment areas of the two tributaries are shown in Figure 4, and the tributary floodways
can be seen in more detail in Figure 6.
Some of the increased stormwater runoff from the proposed residential areas is proposed to be mitigated
by conventional detention volumes in two bio-retention basins, but most of the increased runoff is
proposed to be attenuated by an increase in the floodway storage on the site. The increased floodway
storage will be achieved by deliberately “roughening” the floodways (by revegetating the riparian zones,
as required by Council) and by constructing a restrictive footbridge across the eastern tributary to back-up
the flood profiles in that tributary floodway.
Hydraulic model analyses of the interaction between increased site runoff and floodway through-flows
can be skewed by “hydrograph separation”, whereby the urbanisation of a particular site is predicted to
hasten the discharge of the increased site runoff down the floodway before the arrival of the major
floodway flows from the upstream catchment – which can lead to a perception that the peak flow-rates
along the floodway will not be significantly increased, which in turn leads to a perception that little or no
attenuation volume is required. This perception may be valid for a site development that is considered in
isolation, but it becomes invalid when the “equal opportunity” development of all such sites in the
catchment is collectively considered.
To overcome the abovementioned modelling difficulty without resorting to a catchment-wide “equal
opportunity” analysis, this assessment has firstly determined the detention volume that would be required
for a fully-conventional system of dedicated basins on the site’s stormwater outlets. The assessment was
thereafter focussed on achieving at least that volume from the proposed combination of bio-basin
detention and increased floodway volume, while also using a floodway model to verify that the proposed
changes to the floodway profiles on the site would not adversely affect the flood profiles upstream and
downstream of the site.
The development proposal is particularly cognisant of the need to not increase local stormwater
discharges (as distinct from tributary channel through-flows) onto an adjoining property to the north –
namely No 2 Pearsons Road (refer Figure 1). This is proposed to be achieved by diverting part of the
runoff from the relevant sub-catchment, directly across to the western tributary floodway within the site.
This diversion proposal had to be accounted in the floodway modelling process.
The assessment process was therefore structured as follows:
- Determination of the required detention volume - as described in Section 3 of this report.
- Devising a diversion mechanism, in liaison with the applicant’s civil consultant (Callaghan & Toth),
to ensure no increase in stormwater discharges to No 2 Pearson Road – as described in Section 3.
- Calculation of the runoff rates to the floodways and running them though floodway models of the pre
and post-development scenarios – as described in Sections 4 to 7.
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3.0 STORMWATER DETENTION REQUIREMENT
As already noted in Section 1, the increased rates of stormwater runoff from the site are proposed to be
mitigated partly by conventional detention storage in two bio-basins and partly by increased floodway
storage on the site, with a requirement that the combined volume of those two storages should be at least
equal to the detention volume that would be required for a fully-conventional system.
The detention volume that would be required for a fully-conventional system has been determined by
compiling hydrologic models of four distinct parts of the proposed development platform, notated as
models A, B, C and D in Figure 2 of this report.
The attenuation objective for each of the four models was set by Rational Method calculations of the pre-
and post-development peak flow rates, as summarised in Tables 1 and 2 hereafter. The contributing areas
shown for Area A in Tables 1 and 2 are slightly less than the actual area of 2.49 hectare, because of
partial-area criticality (refer Figure 2 for partial-area limits).
Table 1: Rational Method Calculations Of Pre-Development Peak Flow Rates
Area C10 Tc I (mm/hr) A Q (m3/s)
(min) 1 / 2 / 5 / 10 / 20 / 50 / 100 (Ha) 1 / 2 / 5 / 10 / 20 / 50 / 100
A 0.72 24 65 / 73 / 98 / 116 / 130 / 152 / 166 2.43 0.25 / 0.30 / 0.45 / 0.56 / 0.66 / 0.85 / 0.97
B 0.70 18 75 / 84 / 112 / 132 / 151 / 172 / 192 0.85 0.10 / 0.12 / 0.18 / 0.22 / 0.26 / 0.33 / 0.38
C 0.70 20 71 / 80 / 106 / 127 / 142 / 165 / 180 1.85 0.20 / 0.24 / 0.36 / 0.46 / 0.54 / 0.68 / 0.78
D 0.70 16 80 / 90 / 120 / 140 / 158 / 183 / 202 1.34 0.17 / 0.20 / 0.30 / 0.37 / 0.43 / 0.55 / 0.63
Table 2: Rational Method Calculations Of Post-Development Peak Flow Rates
Area C10 Tc I (mm/hr) A Q (m3/s)
(min) 1 / 2 / 5 / 10 / 20 / 50 / 100 (Ha) 1 / 2 / 5 / 10 / 20 / 50 / 100
A 0.78 18 75 / 84 / 112 / 132 / 151 / 172 / 192 2.34 0.30 / 0.36 / 0.54 / 0.67 / 0.80 / 1.00 / 1.17
B 0.80 13 89 / 100 / 133 / 155 / 175 / 201 / 221 0.85 0.13 / 0.16 / 0.24 / 0.29 / 0.35 / 0.44 / 0.50
C 0.80 14 86 / 96 / 129 / 150 / 169 / 194 / 214 1.85 0.28 / 0.34 / 0.50 / 0.62 / 0.73 / 0.92 / 1.06
D 0.80 11 93 / 105 / 141 / 163 / 186 / 215 / 235 1.34 0.22 / 0.27 / 0.40 / 0.49 / 0.58 / 0.74 / 0.84
Version 3.5g of the URBS software was used as the basis for the hydrological models of Areas A to D.
Each of those areas was modelled as a sub-area network, using the subdivision lines indicated on Figure
2. Each of the four models was based on post-development conditions and was calibrated to closely
match its peak outflow rates to the Rational Method calculations of the post-development flow rates (as
in Table 2). A hypothetical detention basin was then added to the outlet of each model, with its storage-
discharge characteristics adjusted so as to reduce the peak outflow rates to the Rational Method
calculations of the pre-development flow rates (as in Table 1). The resultant storage requirements are
summarised in Table 3, below:
Table 3: Required Detention Volumes (m3) For Fully-Conventional System
Area 1 Yr 2 Yr 5 yr 10 Yr 20 Yr 50 yr 100 Yr
A 130 170 245 290 355 445 520
B 60 80 110 130 150 195 220
C 130 175 260 300 360 425 495
D 75 100 155 190 230 305 350
Total 395 525 770 910 1095 1370 1585
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4.0 STORMWATER DISCHARGES TO No 2 PEARSONS ROAD
A catchment area of 2.49 hectares presently drains across the northern boundary of the site and onto No 2
Pearsons Road, as shown for the pre-development scenario in Figure 3. Local stormwater discharges onto
the adjoining property will be maintained at or below their existing rates by diverting part of the runoff
from the relevant catchment, directly across to the western tributary floodway within the site, as shown
for the post-development scenario in Figure 3.
The existing discharge rates to the adjoining property, as calculated by the Rational Method for the
partial-area of 2.43 hectares shown in Figure 3, are summarised in Table 4 below:
Table 4: Rational Method Calculations Of Pre-Development Peak Flow Rates To No 2 Pearson Road
C10 Tc I (mm/hr) A Q (m3/s)
(min) 1 / 2 / 5 / 10 / 20 / 50 / 100 (Ha) 1 / 2 / 5 / 10 / 20 / 50 / 100
0.72 24 65 / 73 / 98 / 116 / 130 / 152 / 166 2.43 0.25 / 0.30 / 0.45 / 0.56 / 0.66 / 0.85 / 0.97
In the post-development scenario, runoff from the 2.40 hectare post-development catchment (excluding a
0.018 hectare drainage corridor connecting to the adjoining property) will be collected at the sag in the
proposed road, from which flows up to Q5 will be diverted eastward by piping along the road, to the
western tributary channel. Flows in excess of Q5 at the sag will discharge overland, through the
abovementioned drainage corridor, to the adjoining property.
The Q5 diversion capacity, as calculated by the Rational Method for a partial area of 2.25 hectares, is
summarised in Table 5, below:
Table 5: Rational Method Calculation Of Q5 Diversion Capacity
C10 Tc (min) I5 (mm/hr) A (Ha) Q5 (m3/s)
0.78 18 112 2.25 0.00278 x (0.95 x 0.78) x 112 x 2.25 = 0.52
The post-development discharge rates to the adjoining property up to Q5, being just the runoff from the
surface of the connecting drainage corridor, are calculated by the Rational Method as in Table 6 below.
These flow rates are all practically zero.
Table 6: Rational Method Calculations Of Post-Development Flows Up To Q5 To No 2 Pearson Road
C10 Tc I (mm/hr) A Q (m3/s)
(min) 1 / 2 / 5 (Ha) 1 / 2 / 5
0.90 10 97 / 109 / 147 0.018 0.003 / 0.004 / 0.006
The post-development discharge rates to the adjoining property from Q10 to Q100, as calculated by the
Rational Method for the partial area of 2.30 hectares shown in Figure 3, are summarised in Table 7,
below:
Table 7: Rational Method Calculations Of Post-Development Flows Q10 - Q100 To No 2 Pearson Road
C10 Tc I (mm/hr) A Q (m3/s)
(min) 10 / 20 / 50 / 100 (Ha) 10 / 20 / 50 / 100
0.78 18 132 / 151 / 172 / 192 2.30 0.66 / 0.79 / 1.00 / 1.15
Less 0.52 m3/s Q5, =
0.14 / 0.27 / 0.48 / 0.63
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The consequent changes in local discharges from the site, to No2 Pearsons Road, are collated from Tables 4, 6 and 7 and summarised in Table 8, below. The changes are seen to be non-adverse, from Q1 to Q100. Table 8: Changes To Local Stormwater Discharges (m3/sec) From Site To No 2 Pearsons Road Scenario Q1 Q2 Q5 Q10 Q20 Q50 Q100 Pre-Development 0.25 0.30 0.45 0.56 0.66 0.85 0.97 Post-Development 0.003 0.004 0.006 0.14 0.27 0.48 0.63 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 7
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5.0 RUNOFF RATES TO FLOODWAY MODEL
5.1 Catchment Areas And Subdivision
Flood profiles along floodways such as the subject tributaries are affected by the hydraulic capacity of the
adjoining downstream reaches and by any waterway structures in those downstream reaches.
Accordingly, the Extran model extends some distance downstream of the site to the convergence of the
two tributaries just downstream of Pearsons Road, as shown in Figure 3. The catchment modelling
therefore includes not just the contributing areas alongside and upstream of the site, but also the areas
downstream of the site to that termination point downstream of Pearsons Road. The extent of the 151.7
hectare overall catchment is shown in Figures 4 and 5. The site occupies 8.0 hectare, or about 5 percent,
of the overall catchment area.
The catchment has been subdivided into 23 subareas for modelling of the pre-development scenario (as in
Figure 3), and 41 subareas for the post-development scenario (as in Figure 4). The subdivision of the
areas external to the site is identical between the two scenarios, whereas the subdivision of those areas
which discharge to the floodways within the site are treated differently between the two scenarios, to
allow for accurate modelling of the increased runoff from the proposed urban development of 65 percent
of the site area. The modelling of the post-development scenario also accounts for the Q5 splits of the
inflows to the bio-basins, which necessitates doubling-up of the relevant six subareas, taking the total
sub-area count to 47 as marked on Figure 5. The impervious fractions applied to each of the modelled
subareas are summarised in Table 9, on the following page of this report.
5.2 Design Rainfall Data
The Bureau of Meteorology has recently updated the rainfall intensity-frequency-duration data that was
previously published in Volume 1 of Australian Rainfall and Runoff (1987). The previous data was based
on rainfalls recorded up to 1985, whereas the latest data is based on rainfalls recorded up to 2010 / 2011.
There has also been a change of nomenclature, whereby the previous description of severity in terms of
“average recurrence interval” has been updated to “annual exceedence probability” for storms from 2-
year to 100 year severity. Rainfall intensities for the 1 year severity are still quoted for an average
recurrence interval of once per year. The updating has increased the rainfall intensities at higher ARI’s
(or lesser exceedence probabilities) by about 4 percent, compared to the previous data. The updated
intensity-frequency-duration data for Cooroy is reproduced in Appendix A of this report.
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Table 9: Impervious Fractions Assigned To Urbs Model Subareas Pre-Development Scenario Post-Development Scenario Subarea Impervious Subarea Impervious (Figure 1) Fraction (Figure 2) Fraction 1 0.10 1 0.10 2 0.15 2 0.15 3 0.15 3 0.15 4 0.35 4 0.35 5 0.15 5 0.15 6 0.50 6 0.50 7 0.20 7 0.30 8 0.06 8 0.60 9 0.10 9 0.00 10 0.30 10 0.60 11 0.30 11 0.50 12 0.58 12 0.50 13 0.65 13 0.50 14 0.28 14 0.50 15 0.45 15 0.50 16 0.45 16 0.50 17 0.00 17 0.50 18 0.04 18 0.50 19 0.08 19 0.60 20 0.31 20 0.00 21 0.35 21/22 0.30 22 0.25 23 0.37 23 0.45 24 0.58 25 0.65 26 0.28 27 0.45 28 0.45 29/39 0.15 30/40 0.15 31/41 0.50 32/42 0.50 33/43 0.55 34 0.55 35 0.55 36 0.45 37 0.08 38 0.60 44 0.39 45 0.35 46 0.25 47 0.45 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 9
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5.3 Model Calibration
The catchment runoff processes have been modelled with the “basic” variant of Version 3.5g of the Urbs
software, with the “Rational Method” procedure invoked so as to improve the routing simulation within
individual subareas, and with rainfalls converted to runoff via the initial/continuing loss procedure. The
operating parameters of the model which affect the outcome of the simulation are the storage lag
parameter (alpha), the non-linearity parameter (m), the initial rainfall loss (IL) and the continuing rainfall
loss (CL).
Ideally, the operating parameters should be calibrated to observed rainfall and runoff data in the subject
catchment, using either data from particular storm events or derived statistical data via a frequency curve
of recorded flows. In this instance, there is a streamgauge further downstream in the broader catchment
(at Cooran, where the contributing catchment area is 180 square kilometres, or about 120 times larger
than the subject catchment). This gauge has been recording flood flows for 60 years, but the accuracy of
its height/flow rating curve has been confirmed by current-metering to only just above the 1-in-2 year
flood height, which means that its usefulness for model calibration to flows of 5 year or greater severity
is very questionable.
The calibration has therefore reverted to an alternative process involving three stages:
- Calibration to Rational Method calculations of the peak flow rates from individual subareas and groups
of subareas.
- Comparing the calibrated parameters from the first stage to the corresponding parameters from
previous calibrations to other morphologically similar catchments with more highly rated streamgauge
data.
- Comparing the predicted peak flow rates at particular locations in the modelled area to the
corresponding flow rates in the 2002 L&T floodway model.
The Rational Method calibration has been applied to the peak flow rates entering the floodway model
near the upstream boundaries of the site and to the peak inflow rates from each of the subareas which
discharge to the floodway within the subject site. The relevant calculations are summarised in
Appendices B and C of this report, for the pre- and post-development scenarios respectively. An
acceptably close calibration to these calculated peak flow rates was achieved, as in Table 10 below and in
Table 11 on the following pages of this report, using an alpha parameter of 0.85 an m parameter of 0.8,
an initial rainfall loss of 16 mm, and a continuing rainfall loss of 2 mm/hour. The alpha parameter for
individual small subareas which discharge overland flow mostly as shallow sheet flow was increased by
arbitrarily applying reach factors of up to 3.
Table 10 : URBS / Rational Method Peak Flow Calibration (m3/sec) For Pre-Development Scenario
(Refer Figure 4 For Subarea Locations)
Subareas 1 year 2 year 5 Year 10 Year 20 year 50 year 100 Year
1–5 5.2 / 6.0 6.7 / 7.6 11.2/ 11.5 14.5 / 14.2 17.4 / 16.9 21.4 / 21.5 24.8 / 24.6
7 0.29 / 0.29 0.36/ 0.35 0.54 / 0.52 0.64 / 0.63 0.78 / 0.75 0.96 / 0.95 1.10 / 1.10
8 0.24 /0.25 0.30 /0.30 0.47 / 0.45 0.56 / 0.55 0.68 / 0.65 0.83 / 0.83 0.96 / 0.96
9 0.21 / 0.23 0.26 / 0.27 0.40 / 0.40 0.49 / 0.49 0.60 / 0.59 0.74 / 0.74 0.85 / 0.85
12 – 16 4.8 / 4.8 6.1 / 5.8 9.3 / 8.6 11.2 / 10.8 13.6 / 12.8 16.5 / 16.2 18.8 / 18.7
17 0.19 / 0.22 0.24 / 0.26 0.39 / 0.38 0.48 / 0.48 0.59 / 0.57 0.72 / 0.71 0.82 / 0.83
18 0.20 / 0.21 0.25 / 0.26 0.39 / 0.38 0.47 / 0.47 0.57 / 0.56 0.70 / 0.71 0.81 / 0.81
19 0.19 / 0.21 0.23/ 0.25 0.37 / 0.37 0.46 / 0.46 0.56 / 0.54 0.69 / 0.70 0.79 / 0.79
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Table 11 URBS / Rational Method Peak Flow Calibration (m3/sec) For Post-Development Scenario
(Refer Figure 5 For Subarea Locations)
Subareas 1year 2 year 5 Year 10 Year 20 year 50 year 100 Year
7 0.30 / 0.30 0.37 / 0.36 0.56 / 0.54 0.68 / 0.67 0.81 / 0.79 1.00 / 1.00 1.14 / 1.15
8 0.05 / 0.05 0.06 / 0.06 0.10 / 0.09 0.12 / 0.11 0.14 / 0.13 0.17/ 0.17 0.19 / 0.19
9 0.13 /0.14 0.17 /0.16 0.27 / 0.25 0.33 / 0.30 0.39 / 0.36 0.47 / 0.46 0.53 / 0.53
10-18 0.19 / 0.20 0.24 / 0.24 0.37 / 0.37 ---- /----- ---- / ---- ---- / ---- ---- / ----
19 0.06 / 0.06 0.08 / 0.08 0.12 / 0.11 0.14 / 0.14 0.17 / 0.17 0.20 / 0.21 0.23 / 0.24
20 0.19 / 0.20 0.23 / 0.22 0.39 / 0.34 0.47 / 0.42 0.55 / 0.50 0.66 / 0.64 0.74 / 0.74
25-35 0.37 / 0.39 0.47 / 0.46 0.71 / 0.68 ---- / ---- ---- / ---- ---- / ---- ---- / ----
36 0.21 / 0.21 0.26 / 0.25 0.39 / 0.38 0.48 / 0.43 0.56 / 0.56 0.68 / 0.70 0.77 / 0.80
37 0.10 / 0.11 0.13 / 0.13 0.20 / 0.19 0.24 / 0.24 0.29 / 0.28 0.36 / 0.35 0.41 / 0.41
38 0.06 / 0.06 0.07 / 0.07 0.11 / 0.11 0.14 / 0.13 0.16 / 0.16 0.19 / 0.20 0.22 / 0.23
The calibrated parameters compare favourably with those inferred from other morphologically similar
catchments having more highly rated streamgauge data. In this instance, data have been inferred from
previous model calibrations to streamgauge records in Moggill Creek and Bulimba Creek in the outer
suburbs of Brisbane, with a comparison as in Table 12 below:
Table 12 Comparison Of Adopted Operating Parameters With Other Calibrations
Operating Parameter Adopted Values Moggill, Bulimba Creeks
Alpha 0.85 0.80 – 0.83
m 0.80 0.75 – 0.80
IL (mm) 16 15 – 20
CL (mm/hr) 2 2-3
The predicted peak inflow rates to the upstream end of the floodway model also compare favourably to
the peak flow rates in L&T’s Mike 11 floodway model, as in Table 13, below:
Table 13 : Comparison of BSM / CLT Peak Flows (m3/sec) At Upstream Boundaries Of Site
BSM Subareas CLT Mike XS 10 Year 20 Year 50 Year 100 Year
1–5 T3-789 14.4 / 12.1 17.3 / 16.1 21.3 / 21.8 24.8 / 25.7
12 – 16 T2-457 11.2 / 11.0 13.5 / 13.2 16.5 / 16.5 18.8 / 18.7
5.4 Linkage From Catchment Model To Floodway Model
BSM’s in-house ‘UrbsInt’ and “AsciXP” subroutines were used to convert flow outputs from particular
subareas or groups of subareas within the Urbs model to inflow hydrographs at particular nodes within
the floodway model, as in Table 14, hereafter:
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Table 14: Discharge Points From Urbs Hydrologic Model To XPStorm Hydraulic Model Pre-Development Scenario Post-Development Scenario Urbs Subareas (Location, Figure 4) XPStorm Node (Location, Figure 6) Urbs Subareas (Location, Figure 5) XPStorm Node (Location, Figure 6) 1-5 1 1-5 1 6 3 6 3 7 4 7 4 8 8 8 7 9 13 9 8 10 16 10 - 18 10 11 20 19 11 12-16 23 20 13 17 25 21 16 18 28 22 20 19 - 20 31 24 - 28 23 21 32 29 - 36 27 22 35 37 28 23 38 3823 29 44 31 45 32 46 35 47 38 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 12
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6.0 FLOOD PROFILES, PRE-DEVELOPMENT
Version 9.28 of the Extran software, as embedded in the XPStorm modelling suite, has been used to
convert the catchment runoff hydrographs to flood profiles along the floodways. The extent and detail of
the model are shown in Figure 3 of this report. Te model provides approximately three times the detail of
the Mike11 model which L&T used in 2002 to model these floodways. The model network also includes
a number of interconnecting links to provide for simulation of overflows between the two tributaries
where they are aligned in close proximity, downstream of the site.
This version of the Extran software includes a facility to specify different internodal distances for the left
overbank, channel and right overbank segments, which in turn provides for a reasonably accurate
calculation by the software of the internodal flood volumes up to the peak flood level profile. This feature
was vital for checking that the reshaping of the floodway in the post-development scenario achieves the
required stormwater detention volumes, over-and-above the existing floodway volumes. Accordingly,
this facility was invoked for this analysis and separate internodal distances were measured and applied to
each connecting link of the model network.
Field-surveyed spot heights, which can be seen in the background of Figure 6 were used to define the
cross-section shape of each of the links between adjoining nodes of the model. The Manning’s n values
of the channel and overbank sectors of the floodways were perceived by site inspection. The adopted
values ranged from 0.035 for open grassed paddock or park, to 0.150 in densely timbered areas.
Examples of the adopted values are shown in Figures 7and 8 of this report.
The starting point for the simulations was the tailwater level just downstream of the convergence of the
two tributaries. Initial runs of the model, based on a “normal-depth” criterion at node 39 at the
downstream end of the model, simulated a 100 year tailwater level substantially higher than L&T’s
predicted tailwater level at this location. The slope of the outfall reach, between nodes 38 and 39, was
therefore artificially steepened so as to induce a simulated tailwater level much closer to the L&T level.
Initial runs of the model, for ARI’s of 2 year and 100 year, and for storm durations from 20 minutes to 9
hours, revealed that the critical storm durations varied from 1.5 hours to 3 hours along these floodways.
Accordingly, all subsequent simulations included three storm durations: - namely, 1.5, 2 and 3 hours.
The set-up of the model resulted in simulated flood levels near the upstream and boundaries of the site
that, apart from node 23, were generally at or slightly above the co-located levels from L&T’s Mike 11
model, as indicated in Table 15 below. Overall, the consistency between the two models appears to be
quite good, despite the considerable difference in network density between the two models.
Table 15 : Comparison of BSM / CLT Flood Levels (m) In Vicinity Of Site Boundaries
BSM Node CLT X-Sect 10 year 20 Year 50 Year 100 Year
3 T3-811 101.61 / 101.38 101.65 / 101.54 101.72 / 101.69 101.81 / 101.71
16 T3-1199 99.60 / 99.58 99.68 / 99.61 99.74 / 99.68 99.79 / 99.71
23 T2-389 100.98 / 101.33 101.05 / 101.39 101.12 / 101.47 101.17 / 101.51
29 T2-611 99.89 / 99.82 99.95 / 99.89 100.01 / 99.97 100.05 / 100.05
The predicted pre-development peak flood levels at each node of the model, for ARI’s from 1to 100
years, are summarised in Tables 16 to 18 on the following pages of this report, where they are compared
to the corresponding post-development flood levels. The corresponding 100 year pre-development flood
profile is shown on Figure 10, and the pre-development 100 year boundary is mapped on Figures 9 and
13.
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Table 16: NODE Predicted 1 Year To 5 Year Flood Levels (m) And Affluxes (m) (Pre-Development Levels Are Based On Existing Floodplain Condition) (Post-Development Levels Are Based On Proposed Floodplain Condition) (Yellow shading indicates areas within site) PRE-DEV EASTERN TRIBUTARY ON Oak WD = NNNMAHAHAHABaA nanny, NH OCOANDAHKWNH =O WESTERN TRIBUTARY 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 102.259 102.213 101.350 101.327 101.250 100.761 100.755 100.084 100.056 100.061 100.012 99.915 99.644 99.554 99.439 99.128 98.873 98.687 98.620 97.962 97.706 97.604 100.729 100.580 100.111 100.056 99.898 99.785 99.651 99.448 98.923 98.871 98.576 98.529 97.745 97.706 97.623 97.417 96.818 1 YEAR POST-DEV AFFLUX 102.254 102.207 101.162 101.112 100.766 100.763 100.755 100.134 100.119 100.122 100.069 99.964 99.699 99.606 99.434 99.121 98.866 98.680 98.615 97.960 97.703 97.602 100.691 100.492 100.230 100.088 100.005 99.819 99.688 99.452 98.930 98.878 98.581 98.533 97.746 97.703 97.621 97.415 96.815 0.00 -0.01 -0.19 -0.22 -0.48 0.00 0.00 0.05 0.06 0.06 0.06 0.05 0.05 0.05 0.00 -0.01 -0.01 -0.01 -0.01 0.00 0.00 0.00 -0.04 -0.09 0.12 0.03 0.11 0.03 0.04 0.00 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.00 PRE-DEV POST-DEV AFFLUX 102.625 102.614 101.386 101.351 101.287 100.776 100.768 100.145 100.121 100.131 100.079 99.983 99.725 99.647 99.551 99.230 98.971 98.776 98.681 97.993 97.840 97.688 100.791 100.631 100.177 100.114 99.965 99.844 99.706 99.469 99.048 98.996 98.686 98.611 97.881 97.840 97.710 97.521 96.920 2 YEAR 102.635 102.624 101.200 101.134 100.783 100.780 100.769 100.203 100.200 100.205 100.149 100.040 99.777 99.689 99.545 99.224 98.966 98.771 98.678 97.992 97.841 97.689 100.768 100.562 100.297 100.156 100.075 99.891 99.758 99.477 99.053 99.000 98.692 98.614 97.882 97.841 97.710 97.521 96.920 0.01 0.01 -0.19 -0.22 -0.50 0.00 0.00 0.06 0.08 0.07 0.07 0.06 0.05 0.04 -0.01 -0.01 -0.01 0.00 0.00 0.00 0.00 0.00 -0.02 -0.07 0.12 0.04 0.11 0.05 0.05 0.01 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 PRE-DEV 102.977 102.969 101.542 101.479 101.395 100.846 100.829 100.295 100.299 100.323 100.270 100.195 99.963 99.887 99.799 99.471 99.192 99.057 98.832 98.088 98.033 97.841 100.923 100.730 100.317 100.233 100.095 99.969 99.833 99.538 99.266 99.223 99.036 98.832 98.084 98.032 97.927 97.721 97.124 5 YEAR POST-DEV AFFLUX 102.978 102.969 101.368 101.213 100.871 100.867 100.849 100.473 100.461 100.457 100.404 100.272 99.992 99.926 99.792 99.461 99.186 99.053 98.830 98.086 98.031 97.839 100.923 100.709 100.433 100.297 100.213 100.032 99.893 99.549 99.265 99.221 99.033 98.830 98.082 98.031 97.924 97.718 97.121 0.00 0.00 -0.17 -0.27 -0.52 0.02 0.02 0.18 0.16 0.13 0.13 0.08 0.03 0.04 -0.01 -0.01 -0.01 0.00 0.00 0.00 0.00 0.00 0.00 -0.02 0.12 0.06 0.12 0.06 0.06 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 14
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Table 17 : NODE EASTERN TRIBUTARY OANoahkwh = NVNUNMABAABBAAAA AH OG NH COANDAHKWNH =O WESTERN TRIBUTARY 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Predicted 10 Year To 50 Year Flood Levels (m) And Affluxes (m) (Pre-Development Levels Are Based On Existing Floodplain Condition) (Post-Development Levels Are Based On Proposed Floodplain Condition) (Yellow shading indicates areas within site) PRE-DEV POST-DEV AFFLUX 103.013 103.000 101.605 101.553 101.447 100.920 100.903 100.415 100.404 100.428 100.375 100.305 100.002 99.956 99.877 99.604 99.347 99.180 98.931 98.173 98.111 97.938 100.977 100.777 100.377 100.287 100.147 100.021 99.888 99.604 99.379 99.347 99.153 98.934 98.172 98.111 98.043 97.823 97.224 103.013 103.001 101.509 101.305 100.949 100.946 100.923 100.635 100.616 100.615 100.568 100.386 100.037 99.996 99.875 99.600 99.342 99.176 98.928 98.170 98.108 97.934 100.998 100.777 100.504 100.364 100.277 100.097 100.957 99.614 99.377 99.343 99.151 98.931 98.169 98.108 98.039 97.819 97.221 0.00 0.00 -0.10 -0.25 -0.50 0.03 0.02 0.22 0.21 0.19 0.19 0.08 0.04 0.04 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.13 0.08 0.13 0.08 1.07 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 103.045 103.028 101.654 101.611 101.484 100.983 100.963 100.552 100.538 100.532 100.476 100.405 100.031 100.000 99.930 99.678 99.441 99.252 99.022 98.272 98.200 98.066 101.047 100.831 100.438 100.346 100.213 100.079 99.946 99.663 99.494 99.448 99.216 99.025 98.271 98.200 98.163 97.935 97.333 103.044 103.027 101.599 101.366 100.973 100.967 100.938 100.751 100.716 100.723 100.673 100.506 100.151 100.051 99.930 99.678 99.441 99.252 99.021 98.271 98.199 98.065 101.078 100.850 100.577 100.438 100.346 100.170 100.033 99.668 99.494 99.448 99.216 99.025 98.271 98.199 98.162 97.934 97.332 PRE-DEV POST-DEV AFFLUX 0.00 0.00 -0.05 -0.25 -0.51 -0.02 -0.02 0.20 0.18 0.19 0.20 0.10 0.12 0.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.03 0.02 0.14 0.09 0.13 0.09 0.09 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 103.083 103.059 101.723 101.679 101.530 101.009 100.979 100.634 100.604 100.627 100.572 100.518 100.144 100.055 99.999 99.737 99.541 99.318 99.121 98.381 98.299 98.210 101.123 100.890 100.504 100.411 100.282 100.144 100.007 99.730 99.649 99.555 99.273 99.124 98.381 98.299 98.280 98.045 97.445 103.082 103.058 101.702 101.452 100.989 100.982 100.948 100.811 100.778 100.787 100.726 100.580 100.234 100.135 99.998 99.737 99.539 99.317 99.119 98.379 98.297 98.207 101.167 100.930 100.662 100.521 100.426 100.253 100.115 99.735 99.647 99.554 99.272 99.122 98.379 98.297 98.278 98.043 97.443 PRE-DEV POST-DEV AFFLUX 0.00 0.00 -0.02 -0.23 -0.54 -0.03 -0.03 0.18 0.17 0.16 0.15 0.06 0.09 0.08 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.04 0.04 0.16 0.11 0.14 0.11 0.11 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 15
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Table 18: Predicted 100 Year Flood Levels (m) And Affluxes (m) (Pre-Development Levels Are Based On Existing Floodplain Condition) (Post-Development Levels Are Based On Proposed Floodplain Condition) (Yellow shading indicates areas within site) 100 YEAR NODE PRE-DEV POST-DEV AFFLUX EASTERN TRIBUTARY 1 103.110 103.110 0.00 2 103.080 103.079 0.00 3 101.805 101.745 -0.06 4 101.731 101.529 -0.20 5 101.561 101.042 -0.52 6 101.025 101.034 0.01 7 100.910 100.986 0.08 8 100.720 100.856 0.14 9 100.667 100.825 0.16 10 100.702 100.838 0.14 11 100.642 100.767 0.13 12 100.594 100.629 0.04 13 100.216 100.293 0.08 14 100.116 100.192 0.08 15 100.051 100.038 -0.01 16 99.791 99.786 0.00 17 99.606 99.600 -0.01 18 99.357 99.354 0.00 19 99.186 99.181 -0.01 20 98.451 98.444 = -0.01 21 98.363 98.357 = -0.01 22 98.308 98.298 -0.01 WESTERN TRIBUTARY 23 101.173 101.226 | 0.05 24 100.932 100.984 0.05 25 100.544 100.716 0.17 26 100.454 100.574 0.12 27 100.325 100.476 0.15 28 100.186 100.297 0.11 29 100.047 100.147 0.10 30 99.817 99.813 0.00 31 99.766 99.758 -0.01 32 99.620 99.615 -0.01 33 99.307 99.304 0.00 34 99.189 99.184 0.00 35 98.451 98.444 = -0.01 36 98.363 98.356 -0.01 37 98.350 98.343 -0.01 38 98.110 98.103 -0.01 39 97.509 97.513 0.00 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 16
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7.0 FLOOD PROFILES, POST-DEVELOPMENT
7.1 Mitigation Concept For Increased Stormwater Runoff
The impact of the increased site runoff on flood profiles along the floodways is proposed to be mitigated
mostly by increasing the floodway storage on the site, and partly by conventional detention storage in
two of the proposed bio-basins. The increase in the floodway storage will be achieved by deliberately
roughening the floodways (by revegetating the riparian zones, as required by Council) and by
constructing a restrictive footbridge across the eastern tributary to back-up the flood profiles in that
tributary floodway.
A small additional amount of storage is also required to offset the minor intrusions of the development
platform into the pre-development 100 year flood boundary, and for some minor regrading of an artificial
hump in the existing low-flow channel around node 5 of the Extran model (as seen on Figure 10).
The full suite of the proposed modifications to the flood storage system is shown on Figure 9, with
additional detail on Figures 10 to 12.
The revegetation of the riparian zones, by planting of shrubs (typically, Lomandra sp) and trees at
densities of one item per 1.5 to 2 square metres, is presumed to increase the Manning’s n of the presently
grassed areas from 0.03/0.05 to 0.07.
The detention storages in the bio-basins are accounted as only the “live” storages, in the narrow range of
elevation between the riser overflow level and the weir level. The overflow level in the riser will be
controlled by an overflow slot in one side of the riser, with details as in Figure 12.
7.2 Model Simulation
An Extran model of the post-development scenario was compiled by adjusting a copy of the pre-
development model so as to include the reshaped and revegetated floodways and associated increases in
Manning’s n values, together with the inclusion of the proposed footbridge, the minor regrading of the
invert around Node 5, and hypothetical vertical walls at the boundaries of the proposed allotments.
The achievement of the required increase in floodplain volume, to offset the development’s stormwater
detention requirement, is summarised in Table 19, below:
Table 19: Comparison Of Pre-Development And Post-Development Floodplain Volumes (m3)
To Required Detention Volumes
1Year 2 Year 5 Year 10 Year 20 Year 50 year 100 Year
Pre-Development 5456 6184 8515 9927 11352 12986 14493
Floodway Storage
Post-Development 5781 6591 9349 11121 12976 14807 16240
Floodway Storage
Floodway Gain 325 407 834 1194 1624 1821 1747
Plus Bio-Basins 162 183 252 252 252 252 252
Less Active Park Fill -0 -0 -0 -0 -0 -18 -45
Nett Gain 487 590 1086 1446 1876 2055 1954
c.f.
Req’d Extra Volume 395 525 770 910 1095 1370 1585
(From Table 3)
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The impact of the proposed development on peak flow rates downstream of the site is summarised in
Table 20, below. Flow rates leaving the site via the eastern tributary (nodes 15 – 16) will be slightly
reduced. Flow rates leaving the site via the western tributary (nodes 29-30) will increase, and this is a
result of the diversion of local stormwater runoff away from No 2 Pearsons Road and directly to the
western floodway. Further downstream along the western floodway, past the junction with the remaining
local runoff from that adjoining property (nodes 31-32), the post-development flows will revert to the
pre-development rates (within +/- 0.01 m3/sec). Further downstream, at the downstream end of the model
(nodes 38-39), where the two tributaries have converged, the flow-rates will be slightly reduced.
Table 20 : Pre / Post-Development Peak Flow Rates (m3/sec) Through Downstream Properties
Between 1 Year 2 Year 5 Year 10 Year 20 Year 50 Year 100 Year
Nodes
15 - 16 6.8 / 6.7 8.4 / 8.3 13.8 / 13.5 17.3 / 17.2 20.4 / 20.4 22.9 / 22.8 26.0 / 25.1
29 - 30 5.1 / 5.7 6.4 / 6.7 9.9 / 10.3 11.9 / 12.8 14.4 / 14.9 17.6 / 18.2 20.0 / 20.6
31 - 32 5.6 / 5.6 6.8 / 6.9 10.2 / 10.3 12.6 / 12.5 18.1 / 18.1 26.5 / 26.6 31.9 / 31.4
38 - 39 12.8/12.6 15.9 / 15.9 24.3 / 24.2 30.2 / 30.0 38.1 / 37.8 47.9 / 47.8 55.0 / 54.1
The flood levels predicted by the post-development model have been compared to those for the pre-
development scenario in Table 16 to 18 on preceding pages of this report, for ARI’s from 1 to 100 years.
Yellow highlighting is used in those two tables to identify nodes that are within the site boundaries. The
flood level affluxes on all external properties as a result of the proposed development are generally seen
to be practically zero (maximum 0.01 metre), when quoted to the nearest centimetre.
The only exception to the abovementioned generality regarding affluxes is at node 23, just upstream of
the site boundary in the western tributary, where the affluxes will range from 0.02 metre in a 10 year
storm to 0.05 metre in a 100 year storm. The western channel between node 23 and the site boundary was
designed in 2006 to be deliberately revegetated to a Manning’s n of 0.15, as part of the adjoining Blue
Wren Place development. That revegetation was installed at the time of that development, but has since
been removed, thereby reducing the present (“pre-development”) Manning’s n in this area to about 0.04,
consequently decreasing the flood levels at node 23 to about 0.4 metre below the original design levels.
The post-development flood levels as a result of Valkev’s development, while being 0.02 to 0.05 metre
above the present levels, will nevertheless be at least 0.3 metre below the original design levels for this
area, and the quoted affluxes are therefore suggested to be of no consequence. This is illustrated by the
levels of the adjoining lot in Blue Wren Place, which are marked on the longitudinal floodway profiles in
Figure 10 of this report.
The corresponding 100 year post-development flood profiles are shown on Figure 10, and the post-
development 100 year boundary is mapped on Figure 13.
7.3 Sensitivity Test
The sensitivity of the development to uncontrolled regrowth along the floodways was examined by
applying a Manning’s n of value of 0.15 to all overbank sectors of all of cross-sections of the model. The
100 year flood levels predicted by this test are summarised in Table 21, on the following page of this
report, and in Figures 10 and 13. The design levels for the development platform should take due account
of these flood levels.
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Table 21: _ 100 Year Flood Levels (m) With Manning’s n 0.150 On All Overbank Areas XPStorm Node Flood Level 3 101.78 4 101.67 5 101.16 6 101.15 % 101.11 8 101,00 9 100.98 10 100.98 i 100.91 12 100.81 13 100.55 14 100.43 15 100.16 23 101.53 24 101.27 25 101.00 26 100.83 oT 100.70 28 100.50 29 100.30 30 100.00 8.0 CERTIFICATION I hereby certify that the findings described in this report have been deduced by industry-standard analytical procedures and that the Sunshine Coast Regional Council can rely on those findings in their considerations of the relevant development application. Denis Ogle, RPEQ 2405, 30 April 2014 Rrithane Gtarmwater Manacemant PhT 4d Naenment File: ‘ValleavSk Nac Page 19
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NORTH
CORDWO
OD
DRIVE
M A SONRY
16
8
15
9 1
AD
RP173883
RO
NS
10
ST RE
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14
AR
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No 2, PEARSONS ROAD 12
6
44 31
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42
5
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40 30
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38
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36 33 28 27
35 100
29 PARK
34
STREE
46 26
T
47 48 49
50 20
51 100 25
52 24
53 56 PARK
54
55 21
19
22 4
57 23 BIO BASIN
3
17 2
E
BLUE R EN
18 1
D RIV
ALD
ON
CD
W
A
E M
PLA LA K
C E
0 SCALE 100 m
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
LOCALITY AND LOT PLAN FIGURE 1
Page 68
NORTH
CORDWO
OD
DRIVE
M A SONRY
PARTIAL-AREA LIMITS, FOR CALCULATION OF
PRE- AND POST-DEVELOPMENT FLOW RATES 16
8
15
9 1
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RP173883
RO
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10
S T RE
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14
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No 2, PEARSONS ROAD 12
6
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42
5
41
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40 30
45 39
38
37 33 27
36 28
35 100
29 PARK
STREE
34
46 26
T
47 48 49
50 20
51 100 25
52 24
53 56 PARK
54
55 21
19
22 4
57 23 BIO BASIN
3
17 2
E
BLUE R EN
18 1
D RIV
ALD
ON
CD
W
A
E M
PLA LA K
C E
0 SCALE 100 m
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
URBS MODELS OF STORMWATER DETENTION REQUIREMENT FIGURE 2
Page 69
AD
RO
NORTH
S
ON
S
AR
PE
PARTIAL-AREA LIMIT, FOR CALCULATION OF
PRE-DEVELOPMENT FLOW RATES
No 2, PEARSONS ROAD
ELM
STREET
PRE-DEVELOPMENT SCENARIO
AD
RO
S
S ON
AR
PE
PARTIAL-AREA LIMIT, FOR CALCULATION OF
POST-DEVELOPMENT FLOW RATES
No 2, PEARSONS ROAD
44
43 FLOW
42 IN EXCESS S
OF Q5
39
ELM
45 38
37 33
36
35 BIO
STREET
34
46
FLOWS UP
TO Q5
47 48 49
50
51
52
53 56
54
55
57
POST-DEVELOPMENT SCENARIO
0 SCALE 100 m
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
PROPOSED CHANGE IN DISCHARGE SCENARIOS TO No 2 PEARSONS ROAD FIGURE 3
Page 70
NORTH
T
E C
GE
W IL
E
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DR
A LD
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MA
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COOROY
EL M
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STREET
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AN
MA P
ELM
T EW
LE
STRE ET
DIAMOND ST
0 SCALE 500 m
KAURI ST
EM ERA LD
ST
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
CATCHMENT SUBDIVISION FOR PRE-DEVELOPMENT URBS MODEL FIGURE 4
Page 71
NORTH
T
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WIL
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DR
LD
T
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DETAIL PLAN - SITE AREA 0 SCALE 200 m
SAPPHIRE STREET
STREET
PEARL STREET
RD
N
TI
AN
MA P
ELM
W
TE
LE
STRE ET
DIAMOND ST
0 SCALE 500 m
KAURI ST
EM ERA LD
ST
OVERALL PLAN
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
CATCHMENT SUBDIVISION FOR POST-DEVELOPMENT URBS MODEL FIGURE 5
Page 72
SCALE BSM— 200m 28 Apr 2014 | VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY | XPSTORM HYDRAULIC MODEL NETWORK | [FIGURE 6 |
Page 73
LOOKING DOWNSTREAM FROM NODE 10, THROUGH NODE 11 TO NODE 12
LOOKING DOWNSTREAM FROM NODE 12, THROUGH NODE 13 TO NODE 14
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
PHOTOGRAPHS OF EASTERN FLOODWAY ON 25 NOVEMBER 2013 FIGURE 7
Page 74
LOOKING DOWNSTREAM FROM NODE 25, TO NODE 26
LOOKING UPSTREAM FROM NODE 27, TO NODE 26
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
PHOTOGRAPHS OF WESTERN FLOODWAY ON 25 NOVEMBER 2013 FIGURE 8
Page 75
NORTH
0 SCALE 100 m
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
PROPOSED FLOODWAY MODIFICATIONS FIGURE 9
Page 76
WESTERN TRIBUTARY
EASTERN TRIBUTARY
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
LONGITUDINAL FLOODWAY PROFILES FIGURE 10
Page 77
DETAIL OF CHANNEL RESHAPING
TYPICAL CROSS-SECTION DETAILS
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
FLOODWAY CROSS - SECTION CHANGES, WEST TRIBUTARY FIGURE 11
Page 78
DECK LEVEL 100.55 (10 YR FLOOD LEVEL)
0.25 M 0.4 M
APPROACH FILL APPROACH FILL
0.2 M DIA PILE IL 98.63
0.45 M DIA PILE
PROPOSED FOOTBRIDGE, LOOKING DOWNSTREAM
(ONE 8.8 M CLEAR BRIDGE SPAN, PLUS THREE 2.2 M CLEAR BOARDWALK SPANS)
Q5 STORAGE LEVEL
Q1 STORAGE LEVEL
0.3 M BIO-STORAGE 0.7 M 0.4 M 0.1 M
WEIR
N-3
1-O
SAND SURFACE AREA 200 M2
1 M x 1M (INT) RISER BOX
0.7 M WIDE x 0.4 M DEEP NOTCH IN ONE SIDE
OUTLET PIPE, DIA AS REQ'D SAFETY / TRASH RACK AS REQ'D
TO CONVEY Q5 = 0.63 M3/SEC
BIO-BASIN SCHEMATIC, WESTERN TRIBUTARY
Q5 STORAGE LEVEL
0.2 M BIO-STORAGE
0.2 M 0.07 M Q1 STORAGE LEVEL
WEIR
-5
1 - ON
SAND SURFACE AREA 150 M2
1 M x 1M (INT) RISER BOX
1.0 M WIDE x 0.2 M DEEP NOTCH IN ONE SIDE
OUTLET PIPE, DIA AS REQ'D SAFETY / TRASH RACK AS REQ'D
TO CONVEY Q5 = 0.35 M3/SEC
BIO-BASIN SCHEMATIC, EASTERN TRIBUTARY
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
FOOTBRIDGE AND BIO - BASIN SCHEMATICS FIGURE 12
Page 79
NORTH
0 SCALE 50 m
28 Apr 2014
VALKEV PTY LTD - ELM STREET AND LAKE MACDONALD DRIVE, COOROY
FLOOD LEVELS AND FLOOD BOUNDARIES FIGURE 13
Page 80
Appendices
A. Design Rainfall Data
B. Rational Method Calculations Of Floodway Inflows, Pre-Development
C. Rational Method Calculations Of Floodway Inflows, Post Development
D. Floodplain Storage Volumes
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Appendix A
Design Rainfall Data
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= i 4 Ret Recents “se Bureau of Meteorology Location Label: Cooroy Latitude: 26° 24' 26" S)] Longitude: 152° 54' 51" (Nearest grid cell: 152.9125 (E)] mm) Rainfall depth for Durations, Exceedance per Year (EY), and Annual Exceedance Probabilities (AEP). EY Duration | aey | 50% | 20% | 10% | 5% | 2% | 1% | 1 min 2.7 3.1 4.2 a9| . 5.6 6.4 7.1| 22min 43, 5.4) 74, os} ioa; 119) 13.3 3 min 68) 76, 1oal 122; a4al 165] 48.4 4 min a 8.5. 96] 430| 193| i75| 20.5) 229 5 min | a03) dal «sel aso) Soe sanl a0 10min 16.1, 182] 245| 285| 324] 37.3/ 40.9 15 min | 204) 23.0 309| 36.0| 40.9| 47.0) 51.6 30 min : 28.9, 326] 439| 5ial see; 67.8| 74.7 ahour 393| 444| 603/ [email protected]| 95.7| 106.4] 2 hour | | 523; seal 62a| 97.8] 113.4] 134.5] 151.0] 3 hour | 61.61 70.4) 98.4, 118.0| 137.6] 164.3| 185.3 6 hour | sil 93.9, 134.3/ 162.8) 191.6) 231.0] 262.3 12 hour | 106.3/ 124.0| 1981.5| 222.5] 2641] 321.7, 367.6 | 24 hour | 134.9] 158.8] 237.6 294.8 353.6] 436.1| 502.8 Aa8hour 164.5. 194.4. 295.7, 371.2, 450.7, 564.9 659.8 72 hour | 481.6 2145] 327.8, 413.8) 505.7; 640.01 753.4 96 hour _ 194.2 229.1. 350.0 442.8 542.9 690.6 816.5 120 hour ‘| 204.9] 241.2) 367.61 465.2| 570.8) 727.5) 861.7 144 hour [214.8] 252.3) 383.1] 484.2) 593.7/ 756.2| 895.5| 168 hour | 2245] 263.2) 397.6, 501.3; 623.4] 779.5| 921.5 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 22
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Appendix B
Rational Method Calculations Of Floodway Inflows, Pre-Development
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Concentration Times
Subareas 1 - 5
Average Stream Velocity: 5-6% catchment slope = hilly; T = 1206 / 0.9 x 60 = 22 mins
Components Of Flow: 40 m sheet flow @ 10% = 9 mins
530 m steep [email protected] m/sec = 7 mins
730 m [email protected] – 1.1 m/sec = 12 mins
Total: 28 mins
Bransby-Williams: T = 58 L / A0.1 Se0.2 = 58 x 1.206 / 66.8 0.1 x 1.04 0.2 = 46 mins
From 22, 28, 46 mins (average 32) : Adopt Tc = 30 mins
Subarea 7
55 m sheet flow @ 4-5% = 12 mins
230 m swale/channel @ 5% = 4 mins
Total: 16 mins
Subarea 8
130 m sheet flow, partly lawn @ 7% = 16 mins
Subarea 9
85 m sheet flow @ 8% = 13 mins
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Subareas 12 — 16 Std inlet time for 10% grade = 9 mins 150 m pipe/kerb along Tewantin Rd@ 6% = 1.2 min 60 m pipe/kerb along Kauri St@ 4% grade = 0.6 mins 115 m pipe/kerb along Pearl St @ 4% grade = 1.2 mins 115 m pipe flow to sapphire [email protected]% grade = 1.8 mins 260 m open easement [email protected]% grade = 6.0 mins 370 m natural floodway @ hydraulic model 0.8 m/sec = 7.7 mins Total: = 27 mins Subarea 17 130 m sheet flow @ 4% = 19 mins Subarea 18 90 m sheet flow @ 4%, partly lawn = 16 mins Subarea 19 85 m sheet [email protected]%, average grass = 19 mins 85 m natural [email protected] m fall = 5 mins Total: 24 mins Q=0.00278 x FxCxIx A (F = 0.80 / 0.85 / 0.95 / 1.00 / 1.05 / 1.15 / 1.20) Subs Fi | C10 Tc I (mm/hr) A Q (m3/s) (min) | 1/2 / 5 / 10 / 20 / 50 / 100 | (Ha)} 1/2 /5 / 10 / 20 / 50 / 100 1-5 | 0.21 | 0.74 | 28 60/67 / 90 / 107 / 123 / 140 / 155 | 66.8 | 6.0/7.6/11.5/14.2/16.9 /21.5 /24.6 7 0.20 | 0.74 | 16 80/90 /120/ 140 / 158 / 183 / 202 | 2.2 | 0.29/0.35/0.52/0.63 /0.75/ 0.95/ 1.10 8 0.06 | 0.71 16 80/90 /120/ 140 / 158 / 183 / 202 | 2.0 | 0.25/0.30/0.45 / 0.55 / 0.65 / 0.83/ 0.96 9 0.10 | 0.72 | 13 89 /100/133/ 155 / 175 / 201 / 221 | 1.64 | 0.23/0.27/ 0.40 / 0.49 / 0.59 / 0.74 / 0.85 12-16 | 0.50 | 0.80 | 24 61/73/ 98 / 116 / 130 / 153 / 165 | 44.4 | 4.8/5.8 /8.6 /10.8 /12.8 /16.3/ 18.7 17 0.00 | 0.70 | 19 73: 182/109 / 129 / 148 / 167 / 186 | 1.9 | 0.22/0.26/ 0.38 / 0.48 / 0.57 / 0.71 / 0.83 18 0.04 | 0.71 16 80/90/120/ 140 / 158 / 183 / 202 | 1.7 | 0.21/0.26/0.38/0.47/0.56/0.71/0.81 19 0.09 | 0.72 | 24 65/ 73/ 98/ 116/ 130/ 152 / 166 | 1.99 | 0.21/0.25 / 0.37 / 0.46 / 0.54 / 0.70 /0.79 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 25
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Appendix C
Rational Method Calculations Of Floodway Inflows, Post-Development
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Concentration Times Subarea 7 As per “Pre-Development”, Tc = 16 mins Subarea 8 QUDM std inlet time, 6 – 7% slope = 10 mins Subarea 9 Most of the area is within the 100 yr flood boundary: adopt Tc = 5 mins. Subareas 10 - 18 50 m sheet flow across lawn @ 8% = 13 mins 50 m swale/pipe @ 1% = 1 min Total: = 14 mins Subarea 19 30 m sheet flow across lawn @ 3% = 10 mins 45 m pipe / swale @ 2% = 1 min Total: = 11 mins Subarea 20 Most of the area is within the 100 yr flood boundary: adopt Tc = 5 mins Subarea 29 - 35 70 m sheet flow across lawn @3% = 17 mins 65 m pipe/kerb @ 2 m fall = 1 min 160 m pipe @ 6 m fall = 2 mins Total: = 20 mins Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 27
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Subarea 36 QUDM std inlet time for 8% grade = 10 mins 70 m wq-swale & pipes @ 1% = 2 mins Total : = 12 mins Subarea 37 As per “Pre-Development” : 16 mins Subarea 38 QUDM std inlet time for 1.5% grade = 15 mins 5-10 m pipe = 0 mins Total: = 15 mins Q=0.00278 x FxCxIx A (F = 0.80 / 0.85 / 0.95 / 1.00 / 1.05 / 1.15 / 1.20) Subs Fi C10 Tc I (mm/hr) A Q (m3/s) (min) 1/2/ 5 / 10 / 20 /50 /100 | (Ha) 1/ 2/5/10 / 20/50 / 100 0.30 | 0.76 16 80/90/ 120/140 / 158/ 183/202 | 2.25 | 0.30/ 0.36/ 0.54 / 0.67 / 0.79 / 1.00/ 1.15 oo; 0.60 | 0.82 10 97/109 / 147/171 / 194/ 224/245 | 0.29 | 0.05/0.06/ 0.09 / 0.11 /0.13 /0.17/0.19 9 0.00 | 0.70 5 121/137 /185 / 216 / 247 / 288 / 318 | 0.72 | 0.14/0.16/ 0.25 /0.30/ 0.36 / 0.46 / 0.53 10-18 | 0.50 | 0.80 14 84/96 / 128 / - / - / -/ - | 1.35 | 0.20/0.24/0.37/ ----/ ---- / ---- / ---- 19 0.60 | 0.82 11 94/106 /143 / 166 / 189 / 218/238 | 0.37 | 0.06/0.08 / 0.11 /0.14/0.17/0.21 /0.24 20 0.00 | 0.70 5 121/137 / 185 / 216 / 247 / 288/318 | 0.99 | 0.20/0.22 / 0.34 / 0.42 / 0.50 / 0.64 /0.74 29-35 | 0.46 | 0.79 20 71/80/106/ --- / --- / --- /--- | 3.09 | 0.39/0.46/0.68/ --- / --- / --- /--- 36 0.45 0.79 12 92 /103 /138/ 160 / 183/211 /231 | 1.32 | 0.21/0.25/0.38/ 0.48 / 0.56 / 0.70 /0.80 37 0.08 | 0.72 16 80/90 / 120/140 / 158/ 183/202 | 0.84 | 0.11/0.13 / 0.19 / 0.24 / 0.28 / 0.35 /0.41 38 0.60 | 0.82 15 82/92 / 124/ 144/ 164/ 188/206 | 0.40 | 0.06/0.07 / 0.11 / 0.13 / 0.16 / 0.20 / 0.23 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 28
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Appendix D
Floodplain Storage Volumes
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PRE-DEVELOPMENT FLOODPLAIN STORAGE VOLUMES (CUBIC METRES) USNODE DSNODE 1YEAR 2YEAR SYEAR 10YEAR 20 YEAR 50 YEAR 100 YEAR 3 4 273 =286 356 398 438 490 549 4 5 127 136 178 204 225 250 273 5 6 583-612 724 815 900 957 988 6 7 648 669 776 910 1031 1075 1090 7 8 139 178 341 465 535 560 702 8 9 197 227 318 392 499 563 635 9 10 175 200 281 340 422 497 564 10 11 300 345 491 592 712 842 947 11 12 247 9282 403 480 561 668 750 12 13 314 362 523 590 663 827 960 13 14 470 558 867 988 1071 1262 1462 14 15 310 386 615 718 792 900 1000 23 24 224 256 329 369 425 497 547 24 25 114 136 193 225 262 307 340 25 26 312 352 440 485 535 598 641 26 27 158 192 278 321 379 447 493 27 28 185 221 317 368 428 505 554 28 29 260 311 454 526 611 715 786 29 30 420 475 631 741 863 1026 1212 TOTAL 5456 6184 8515 9927 11352 12986 14493 POST-DEVELOPMENT FLOODPLAIN STORAGE VOLUMES (CUBIC METRES) USNODE DSNODE 1YEAR 2YEAR SYEAR 10YEAR 20 YEAR 50 YEAR 100 YEAR 3 4 208 217 253 293 326 375 420 4 5 85 8691 114 148 168 195 229 5 6 646 667 785 896 929 951 1030 6 7 650 673 812 955 990 1000 1108 7 8 144 187 413 511 760 966 1065 8 9 225 263 436 568 681 756 818 9 10 197 229 364 492 588 650 699 10 11 339 396 624 830 993 1095 1179 11 12 280 322 473 573 683 764 823 12 13 347 = 397 567 649 819 952 1047 13 14 523 607 941 1074 1268 1520 1697 14 15 323 400 630 736 822 953 1053 23 24 224 261 346 392 446 511 560 24 25 161 191 264 303 352 413 456 25 26 285 331 444 510 590 687 751 26 27 235 280 382 437 502 583 638 27 28 223 275 395 459 534 626 680 28 29 305 373 538 626 735 862 924 29 30 381 9 431 568 669 790 948 1063 TOTAL 5781 6591 9349 11121 12976 14807 16240 Brisbane Stormwater Management Pty Ltd Document File: ValkevSDF.Doc Page 30