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Appendix D - Flood Assessment
Attached to the e-mail RAL20/0014 - Response to Council's Information Request - 9A Jirrima Cres, Cooroibah - Email 02 of 02.
FLOOD ASSESSMENT
9A JIRRIMA CRESCENT, COOROIBAH
CLIENT: MAUD CAZOT
DOCUMENT NUMBER: R1593
VERSION: -
Environment. Engineering. Education. PAGE 1
DATE: 31/03/2021
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
TABLE OF CONTENTS TABLE OF FIGURES
1 SCOPE 1
1.1. GUIDELINES 1 FIGURE 1 – SITE LOCATION (EXTRACT FROM NOOSA PLAN 2020) ......................................................................... 1
1.2. REVISION 1 FIGURE 2 – ZONE MAP (EXTRACT FROM NOOSA PLAN 2020) ................................................................................. 1
FIGURE 3 – PROPOSED SITE LAYOUT............................................................................................................................... 2
2 PROJECT DESCRIPTION 1
2.1. LOCATION & LANDUSE 1 FIGURE 4 – EXTRACT FROM NOOSA PLAN FLOOD HAZARD OVERLAY MAP ..................................................... 2
2.2. PROJECT WORKS 2 FIGURE 5 – CATCHMENT PLAN.......................................................................................................................................... 5
FIGURE 6 – XP MODEL FEATURES ..................................................................................................................................... 7
3 SITE DESCRIPTION 2
3.1. TOPOGRAPHY AND DRAINAGE 2 FIGURE 7 – EXTRACT FROM 1 % AEP AFFLUX PLOT .................................................................................................... 9
3.2. FLOODING 2 FIGURE 8 – 1 % PEAK WATER LEVEL ............................................................................................................................... 10
FIGURE 8 – 1 % PEAK WATER LEVEL ................................................................................................................................ 11
4 OVERLAND FLOW ASSESSMENT 3
4.1. HYDROLOGY 3
4.1.1. RAINFALL DATA 3
4.2. CATCHMENT DELINEATION 3 TABLE OF TABLES
4.2.1. ROUTING 4
4.2.2. ROUGHNESS COEFFICIENTS 4 TABLE 1 - INTENSITY FREQUENCY DURATION DATA APPLIED TO HYDROLOGIC ASSESSMENT .................. 3
4.2.3. RAINFALL LOSSES 4 TABLE 2 – CATCHMENT DETAILS APPLIED TO HYDROLOGIC ASSESSMENT ....................................................... 3
4.3. RATIONAL METHOD COMPARISON 4 TABLE 3 – SUMMARY OF RATIONAL METHOD COMPARISON – 1 % AEP ............................................................ 4
4.4. HYDRAULIC MODELLING 6
4.4.1. BOUNDARY CONDITIONS 6
4.4.2. ROUGHNESS 6
4.4.3. 1D ELEMENTS 6
4.5. RESULTS – FLOOD MAPPING 8
4.6. RESULTS – DRIVEWAY FLOODING 8
5 SUMMARY 8
APPENDIX A A
APPENDIX B B
APPENDIX C C
Environment. Engineering. Education. PAGE I
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
1 SCOPE
Topo were engaged by Maud Cazot to prepare a Flood Assessment for a proposed
reconfiguration of lots (1 into 2) at 9A Jirrima Crescent, Cooroibah in Queensland.
The site is formally described as Lot 101 on SP168341 and covers a total area of 4.46
ha.
1.1. GUIDELINES
This report has been prepared in accordance with:
+ Queensland Urban Drainage Manual (QUDM), and
+ The Noosa Plan (2020)
1.2. REVISION Figure 1 – Site Location (Extract from Noosa Plan 2020)
VERSION DATE AUTHOR APPROVED
STEVEN CHAMBERLAIN STEVEN CHAMBERLAIN
- 31/03/2021
(RPEQ 15,545) (RPEQ 15,545)
2 PROJECT DESCRIPTION
2.1. LOCATION & LANDUSE
Site access is provided from Jirrima Crescent via a driveway along the northern
boundary. The site is located within a rural residential zoning area and currently
contains a single dwelling.
Figure 2 – Zone Map (Extract from Noosa Plan 2020)
Figure 1 presents the site and surrounds, while Figure 2 presents the rural residential
zoning.
Environment. Engineering. Education. PAGE 1
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
2.2. PROJECT WORKS
The proposed development will involve a 1 into 2 reconfiguration of lot, with required
stormwater, electrical and services connections. An extract of the proposed
development layout is provided as Figure 3.
3 SITE DESCRIPTION
3.1. TOPOGRAPHY AND DRAINAGE
The site is traversed by a mapped drainage line which enters from the southern
boundary and exits to the north. The site falls inwards from both the eastern boundary
(Jirrima Crescent) and the western boundary (adjacent lot) towards the drainage line.
The peak elevation of the site is located on the north east corner of proposed Lot 2
at approximately 16.0 metres AHD with a general slope of 3 %. The south west corners
has a peak elevation of approximately 9.5 metres AHD on top of the ridge in this Figure 3 – Proposed Site Layout
corner, with a general slope of 2 % to the waterway which is at RL 6.0 near the
northern boundary.
The adjacent lot to the east (9 Jirrima Crescent) slopes towards proposed Lot 2. Some
runoff from the adjacent lots to the south (fronting Illoura Place) has potential to
enter lots 1 and 2 from this direction via overland sheet flow. There is currently no
easement associated with the mapped drainage line, which will provide the lawful
point of discharge for the reconfiguration.
3.2. FLOODING
An extract from the Noosa Plan Flood Hazard Overlay Map is included as Figure 4,
illustrating the approximate location of inundation associated with the drainage line
on the downstream lot.
Figure 4 – Extract from Noosa Plan Flood Hazard Overlay Map
Environment. Engineering. Education. PAGE 2
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
4 OVERLAND FLOW ASSESSMENT 4.2. CATCHMENT DELINEATION
4.1. HYDROLOGY The study area has been divided into 21 sub-catchments as part of this assessment.
The fraction impervious was calculated using aerial photography. A summary of the
An integrated hydrologic and hydraulic model was constructed for the catchment catchment parameters applied to this assessment is included as Table 2, while the
and site using the XP-STORM 1D/2D software. The model represents the sub- catchment plan is included as Figure 5.
catchments as a network of 1D elements and nodes linked to the 2D geometric base.
Each node is defined by its pervious (undeveloped) and impervious (developed) Table 2 – Catchment Details Applied to Hydrologic Assessment
areas, fraction impervious and average catchment slope. The net rainfall is routed
through the network after appropriate losses (initial and continuing) and roughness CATCH ID AREA (HA) FRACTION IMPERVIOUS SLOPE (M/M)
factors are applied, resulting in a surface runoff hydrograph for each sub-catchment.
1 3.36 9.9 6.7
4.1.1. RAINFALL DATA 2 3.78 6.4 4.4
Intensity Frequency Duration (IFD) data for the site has been derived using the Bureau 3 1.72 3.1 6.7
of Meteorology (BOM) 2016 Rainfall IFD Data System. Modelling was undertaken for
4 1.48 10.6 4.1
63 % to 1 % Annual Exceedance Probability (AEP) storm events using the IFD data
summarised in Table 1. 5 1.14 1.7 2.6
6 0.63 13.8 2.9
Table 1 - Intensity Frequency Duration Data Applied to Hydrologic Assessment
7 1.62 0.0 1.6
RAINFALL DEPTH (MM)
DURATION 8a 0.59 1.5 2.6
63% AEP 0.5 EY 0.2 EY 10% AEP 5% AEP 2% AEP 1% AEP 8b 0.49 0.0 1.6
15 84.2 106 131 150 170 195 213 8c 0.10 18.1 4.8
20 73.5 92.2 114 131 149 171 187 8d 0.12 21.8 3.8
25 65.5 82.3 102 117 133 154 169 8e 0.67 16.8 3.2
30 59.4 74.5 92.7 106 121 140 155 8f 0.23 6.0 3.2
45 47 59.1 74 85.4 97.8 114 126 8g 0.50 15.1 4.1
60 39.4 49.7 62.6 72.6 83.5 97.9 109 8h 0.28 13.9 3.5
90 30.6 38.7 49.3 57.6 66.6 78.8 88.1 8i 0.23 17.1 4.4
120 25.6 32.4 41.6 48.8 56.7 67.4 75.7 9 1.56 0.0 1.8
180 12.9 16.6 22 26.2 30.9 37.3 42.3 10 3.43 4.6 3.2
270 122 153 191 220 252 293 323 11 1.86 2.9 2.4
360 99.3 125 154 177 201 231 253 12 1.69 9.8 5.1
13 0.76 0.0 1.3
TOTAL 26.21 - -
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
4.2.1. ROUTING Table 3 – Summary of Rational Method Comparison – 1 % AEP
Hydrologic modelling has been undertaken using the Laurenson runoff routing PEAK FLOW RATE (M³/S)
method. The Laurenson method requires the catchment to be divided into a pervious CATCH ID DIFFERENCE (M³/S)
(undeveloped) and an impervious (developed) portion. A fraction impervious of 0 % RATIONAL METHOD XP
has been applied to the undeveloped portion and 100 % to the developed portion 1 1.60 1.87 -14
and used to calculate the overall fraction impervious for each sub-catchment.
2 1.65 1.73 -4
4.2.2. ROUGHNESS COEFFICIENTS
3 0.81 1.01 -20
The Manning’s roughness coefficients have been varied for the developed and 4 0.66 0.76 -12
undeveloped portions of the catchment and include considerations for the extent and
density of vegetation. The following values were applied. 5 0.55 0.50 8
6 0.29 0.34 -13
+ Developed catchment n = 0.015
+ Undeveloped catchment n = 0.045 to 0.065 7 0.59 0.55 7
8* 1.41 1.35 4
4.2.3. RAINFALL LOSSES
9 0.58 0.56 5
Initial Loss (IL) and Continuing Losses (CL) have been applied to the modelling. These
10 1.49 1.39 7
values have been varied for the developed and undeveloped portions of the
catchment as shown below: 11 0.84 0.72 14
12 0.80 0.91 -12
+ Developed catchment IL = 0 mm, CL = 0 mm/hr
+ Undeveloped catchment IL = 10 mm, CL = 2.5 mm/hr 13 0.27 0.26 5
4.3. RATIONAL METHOD COMPARISON NOTE: * Rational Method comparison undertaken for total catchment rather than individual smaller
sub-catchments
A comparison has been made between peak discharges provided by XP-STORM and
Although not formally a calibration process, it is an effective way to ensure roughness
those provided by the Rational Method calculations for the pre-development
coefficients and loss rates are reasonable in the absence of recorded data. As can be
scenario 1 % AEP critical duration event. This comparison is summarised in Table 3.
seen, the results of the hydrologic model compare well with those provided by the
Rational Method and are therefore appropriate for use as part of this assessment. A
negative value for difference indicates the XP-STORM peak flow rates are higher than
the Rational Method calculation.
Environment. Engineering. Education. PAGE 4
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH Figure 5 – Catchment Plan Environment. Engineering. Education. PAGE 5
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
4.4. HYDRAULIC MODELLING 4.4.2. ROUGHNESS
Review of aerial photography was undertaken to determine the Manning’s roughness
The unsteady state, 1D/2D hydraulic model XP-STORM (incorporating TUFLOW as coefficients and expected loss rates within the catchment. Based on this assessment,
the model engine) was used to analyse the flood behaviour of the study area. LIDAR five land uses/roughness coefficients have been applied to the modelling as
data from DNRM was applied for the external catchments, while detailed site survey summarised below. The default land use is Grass.
was used to represent the site. This data was converted by XP-STORM to create a
TIN for the study area, from which 1.25 m (2D) cells were generated. Flows are + Roads and driveways n = 0.015
transferred into the 2D domain, and flow overland as the topography dictates. Flood + Grass/lawns (default) n = 0.045
levels, discharge and velocity can be extracted from the model as functions of time + Mature Trees/Dense Vegetation n = 0.080
at required locations. + Carports/sheds n = 1.000
+ Dams/water bodies n = 0.025
4.4.1. BOUNDARY CONDITIONS
Dwellings have been modelled as inactive areas and therefore no flow can pass
Hydrographs generated by the hydrologic module of XP-STORM are applied as the
through the buildings. The XP model features are illustrated as Figure 6.
inputs to the 1D hydraulic model and as point flows inside the active 2D domain.
The downstream extent of the model has been extended downstream of the site, with 4.4.3. 1D ELEMENTS
the boundary location chosen to ensure it has no impact of the observed flood levels Cross drainage for the roadways and under the proposed driveway have been
at the site or the proposed driveway crossing. Normal flow conditions are assumed represented as 1D elements, with the inlet and outlet nodes linked to the active 2D
at the outlet. domain. Inlet and exit losses of 0.5 and 0.7 respectively have been applied to the
culverts (in accordance with QUDM (2013) Section 7.16.9 (b)(ii). Culvert details are
provided in the civil plan set included as Appendix A.
Environment. Engineering. Education. PAGE 6
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH Figure 6 – XP Model Features Environment. Engineering. Education. PAGE 7
Page 10
R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
4.5. RESULTS – FLOOD MAPPING 5 SUMMARY
Flood maps are provided in Appendix B, representing: The modelling undertaken as part of this assessment demonstrates the proposed
driveway can be constructed without causing adverse flood impacts for neighbouring
+ Pre-development Peak Water Level – 1 % AEP properties. The proposed driveway also remains trafficable during the critical
o Drawing No. D02 duration 1 % AEP storm event, and therefore complies with the requirements of
+ Pre-development Maximum Depth – 1 % AEP Noosa Council.
o Drawing No. D03
+ Post-development Peak Water Level – 1 % AEP 2 x 1200 x 300 mm box culverts are required under the main flowpath, while an
o Drawing No. D04 additional 1200 x 300 mm box culvert is proposed to the west to ensure ponding
+ Post-development Maximum Depth – 1 % AEP does not occur in an existing low point of the site.
o Drawing No. D05
+ Post-development Maximum Depth – 1 % AEP – Depths Greater than 200mm
o Drawing No. D06
This report and associate modelling have been prepared by Steven Chamberlain of
+ Post-development Velocity x Depth – 1 % AEP
Topo (RPEQ 15,545).
o Drawing No. D07
+ Afflux Assessment – 1 % AEP event
o Drawing No. D08
The results of this assessment indicate there are no adverse impacts in terms of
flooding for the upstream or downstream properties, and the building envelope for
the proposed lot can be provided outside of the flood extents. An extract of the
afflux assessment plot is included as Figure 7.
4.6. RESULTS – DRIVEWAY FLOODING
An assessment has been made of the flow regime at the proposed driveway crossing
during the 1 % AEP event to ensure it complies with the requirements of QUDM.
QUDM requires for transverse flow such as over a causeway:
+ Maximum flow depth, dg ≤ 200 mm
+ The product of flow depth and velocity shall be limited by the formula d g ,.
Vave <= 0.3 m²/s (risk to life).
The velocity-depth plots demonstrate the product of flow depth and velocity is less
than the limiting criteria and the depth of flow is less than 200 mm. Therefore the
proposed driveway remains trafficable during the 1 % critical duration storm event.
An extract of the maximum depth plot for depths greater than 200 mm only, and the
velocity-depth product plots are included as Figure 8 and Figure 9 respectively.
Environment. Engineering. Education. PAGE 8
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH Figure 7 – Extract from 1 % AEP Afflux Plot Environment. Engineering. Education. PAGE 9
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH Figure 8 – 1 % Peak Water Level Environment. Engineering. Education. PAGE 10
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH Figure 9 – 1 % Peak Water Level Environment. Engineering. Education. PAGE 11
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
APPENDIX A
PROPOSAL PLAN
PAGE A
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R1593: FLOOD ASSESSMENT — 9A JIRRIMA CRESCENT, COOROIBAH
TOPO.
APPENDIX A
PROPOSAL PLAN
Environment. Engineering. Education.
rn MZ
Page 15
TAP
BDY
LEGEND
BAX
SCALE: SURVEYED: CLIENT: NORTH POINT TITLE:
M CAZOT EARTHWORK LAYOUT PLAN
DATUM:
PROJECT NO:
113-001
LOCAL AUTHORITY APPROVAL NO:
DATE
CHECKED
DRAWN
APPROVED:
GLENN AINSWORTH
CPESC No: 7678
RPEQ No: 19204
Engineering PTY. LTD.
PROJECT:
PROPOSED SUBDIVISION OF
LOT 101 ON SP168341
No. DATE REVISIONS BY CKD RAL 20/0014 DESIGNED FOR AND ON BEHALF OF BAX ENGINEERING PTY. LTD.
2261 DAVID LOW WAY, PEREGIAN BEACH, QLD 4573
[email protected] 9A JIRRIMA CR, COOROIBAH PLAN No 113-001-004 REVISION A A1
Page 16
LEGEND
BAX
SCALE: SURVEYED: CLIENT: NORTH POINT TITLE:
M CAZOT DRIVEWAY LAYOUT PLAN
DATUM:
PROJECT NO:
113-001
LOCAL AUTHORITY APPROVAL NO:
DATE
CHECKED
DRAWN
APPROVED:
GLENN AINSWORTH
CPESC No: 7678
RPEQ No: 19204
Engineering PTY. LTD.
PROJECT:
PROPOSED SUBDIVISION OF
LOT 101 ON SP168341
No. DATE REVISIONS BY CKD RAL 20/0014 DESIGNED FOR AND ON BEHALF OF BAX ENGINEERING PTY. LTD.
2261 DAVID LOW WAY, PEREGIAN BEACH, QLD 4573
[email protected] 9A JIRRIMA CR, COOROIBAH PLAN No 113-001-100 REVISION A A1
Page 17
BAX
SCALE: SURVEYED: CLIENT: NORTH POINT TITLE:
M CAZOT
DATUM:
DRIVEWAY LONGITUDINAL SECTION
PROJECT NO:
113-001
LOCAL AUTHORITY APPROVAL NO:
DATE
CHECKED
DRAWN
APPROVED:
GLENN AINSWORTH
CPESC No: 7678
Engineering PTY. LTD.
PROJECT:
PROPOSED SUBDIVISION OF
LOT 101 ON SP168341
113-001-102
RPEQ No: 19204
9A JIRRIMA CR, COOROIBAH A A1
2261 DAVID LOW WAY, PEREGIAN BEACH, QLD 4573
No. DATE REVISIONS BY CKD RAL 20/0014 DESIGNED FOR AND ON BEHALF OF BAX ENGINEERING PTY. LTD. [email protected] PLAN No REVISION
Page 18
R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
APPENDIX B
FLOOD MAPS
PAGE B
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R1593: FLOOD ASSESSMENT — 9A JIRRIMA CRESCENT, COOROIBAH
TOPO.
APPENDIX B
FLOOD MAPS
Environment. Engineering. Education.
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Page 19
FLOOD ASSESSMENT
EROSION AND SEDIMENT CONTROL DRAWINGS
9A JIRRIMA CRESCENT, COOROIBAH
COUNCIL - NOOSA COUNCIL
DRAWING LIST:
D00 - COVER SHEET
D01 - CATCHMENT PLAN
D02 - PRE-DEVELOPMENT PEAK WATER LEVEL - 1% AEP
D03 - PRE-DEVELOPMENT MAXIMUM DEPTH - 1% AEP
D04 - POST-DEVELOPMENT PEAK WATER LEVEL - 1% AEP
D05 - POST-DEVELOPMENT MAXIMUM DEPTH - 1% AEP
D06 - POST-DEVELOPMENT MAXIMUM DEPTH > 200mm - 1% AEP
D07 - POST-DEVELOPMENT VELOCITY x DEPTH ASSESSMENT - 1% AEP
D08 - AFFLUX ASSESSMENT - 1% AEP
SITE LOCATION
CLIENT PROJECT
COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
ISSUED FOR USE
THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 FLOOD ASSESSMENT
TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 29-10-20 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED)
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. RPEQ NO. 15,545
20-0231 D00 A
Page 20
CLIENT PROJECT
0 20 COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
SCALE 1:1000 THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 CATCHMENT PLAN
ISSUED FOR USE TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 29-10-20 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED)
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. 20-0231 D01 A
RPEQ NO. 15,545
Page 21
CLIENT PROJECT
0 20 COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
SCALE 1:1000 THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 PRE-DEVELOPMENT PEAK WATER LEVEL - 1% AEP
ISSUED FOR USE TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 31-3-21 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED)
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. 20-0231 D02 A
RPEQ NO. 15,545
Page 22
CLIENT PROJECT
0 20 COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
SCALE 1:1000 THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 PRE-DEVELOPMENT MAXIMUM DEPTH - 1% AEP
ISSUED FOR USE TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 31-3-21 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED)
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. 20-0231 D03 A
RPEQ NO. 15,545
Page 23
CLIENT PROJECT
0 20 COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
SCALE 1:1000 THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 POST-DEVELOPMENT PEAK WATER LEVEL - 1% AEP
ISSUED FOR USE TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 31-3-21 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED)
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. 20-0231 D04 A
RPEQ NO. 15,545
Page 24
CLIENT PROJECT
0 20 COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
SCALE 1:1000 THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 POST-DEVELOPMENT MAXIMUM DEPTH - 1 % AEP
ISSUED FOR USE TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 31-3-21 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED)
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. 20-0231 D05 A
RPEQ NO. 15,545
Page 25
CLIENT PROJECT
0 20 COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
SCALE 1:1000 THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 POST-DEVELOPMENT MAXIMUM DEPTH - 1% AEP
ISSUED FOR USE TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 31-3-21 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED) DEPTHS GREATER THAN 200 mm
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. 20-0231 D06 A
RPEQ NO. 15,545
Page 26
CLIENT PROJECT
0 20 COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
SCALE 1:1000 THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 PRE-DEVELOPMENT MAXIMUM DEPTH - 10% AEP
ISSUED FOR USE TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 31-3-21 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED)
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. 20-0231 D07 A
RPEQ NO. 15,545
Page 27
CLIENT PROJECT
0 20 COPYRIGHT C M CAZOT 9A JIRRIMA CRES, COOROIBAH
TOPO GROUP PTY LTD
DRAWN DESIGNED DATE DRAWING TITLE
SCALE 1:1000 THIS DOCUMENT MAY NOT BE COPIED OR SC SC 31-3-21 AFFLUX ASSESSMENT - 1 % AEP
ISSUED FOR USE TRANSMITTED IN ANY FORM OR BY ANY
A ORIGINAL ISSUE SC 31-3-21 MEANS IN PART OR IN WHOLE WITHOUT
RPEQ / SIGNATURE (IF REQUIRED)
NORTH
A3 THE WRITTEN CONSENT OF TOPO GROUP PROJECT No DRAWING No REVISION
REVISION DESCRIPTION APPROVED BY DATE PTY LTD. 20-0231 D08 A
RPEQ NO. 15,545
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R1593: FLOOD ASSESSMENT – 9A JIRRIMA CRESCENT, COOROIBAH
APPENDIX C
RATIONAL METHOD
PAGE C
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APPENDIX C
RATIONAL METHOD
Environment. Engineering. Education.
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Page 29
Components of time of concentration
(i) Estimate length of sheet runoff as per Table 4.06.3 and calculate travel time using Friends Equation (as per 4.06.6)
(ii) Kerb flow time (if applicable)
(iii) Pipe flow time
(iv) Creek and/or channel flow time
(i) Overland Flow (Section 4.06.6-Friends)
Notes: (1) Refer to Table 4.06.3 for estimated length of sheet flow
(2) Refer to Table 1 for Hortons roughness values
Catchment Cat_1 Cat_2 Cat_3 Cat_4 Cat_5 Cat_6 Cat_7 Cat_8 Cat_9 Cat_10 Cat_11 Cat_12 Cat_13
Estimated Length of Sheet Flow (Table 4.06.3) 100 100 100 100 100 100 100 100 100 100 100 100 100
Hortons Roughness Value 0.045 0.045 0.045 0.045 0.045 0.045 0.06 0.045 0.06 0.045 0.045 0.045 0.06
Slope (%) 6 5 5 3 8 4 2 4 2 6 4 6 1
tc (minutes) 15.59 16.17 16.17 17.91 14.72 16.91 25.90 16.91 25.90 15.59 16.91 15.59 29.75 0.00
(iv) Channel/Creek Flow
Note: Determine actual flow velocity from numerical modelling or the Manning Equation. Alternatively, if the expected travel time in the creek is not critical, assume an avergae flow velocity of
1.5m/s (not applicable to constructed channels)
Catchment Cat_1 Cat_2 Cat_3 Cat_4 Cat_5 Cat_6 Cat_7 Cat_8 Cat_9 Cat_10 Cat_11 Cat_12 Cat_13
Length of Channel Flow (m) 97 200 100 60 83 50 63 263 82 191 84 70 20
Velocity (m/s) - refer to Note 1.5 0.9 1.5 0.9 0.9 0.9 0.3 0.7 0.7 0.7 0.7 0.9 0.3 0.9
tc (minutes) 1.08 3.70 1.11 1.11 1.54 0.93 3.50 6.26 1.95 4.55 2.00 1.30 1.11 0.00
Catchment Cat_1 Cat_2 Cat_3 Cat_4 Cat_5 Cat_6 Cat_7 Cat_8 Cat_9 Cat_10 Cat_11 Cat_12 Cat_13
TOTAL tc (minutes) 16.67 19.88 17.28 19.02 16.26 17.84 29.40 23.17 27.85 20.14 18.91 16.89 30.86 0.00
Catchment Details
Pre
Cat_1 Cat_2 Cat_3 Cat_4 Cat_5 Cat_6 Cat_7 Cat_8 Cat_9 Cat_10 Cat_11 Cat_12 Cat_13
Development
Area (ha) 3.355 3.779 1.716 1.483 1.137 0.63 1.62 3.43 1.56 3.43 1.86 1.69 0.76
Pre Development Flows
Catchment Area tc I100 C100 Q100 I50 C50 Q50 I20 C20 Q20 I10 C10 Q10 I5 C5 Q5 I2 C2 Q2 I1 C1 Q1
Name (ha) (min) (mm/hr) (m³/s) (mm/hr) (m³/s) (mm/hr) (m³/s) (mm/hr) (m³/s) (mm/hr) (m³/s) (mm/hr) (m³/s) (mm/hr) (m³/s)
Cat_1 3.36 16.67 204.31 0.84 1.60 186.97 0.81 1.40 162.98 0.74 1.12 143.65 0.70 0.94 125.31 0.67 0.78 101.39 0.60 0.56 80.62 0.56 0.42
Cat_2 3.78 19.88 187.64 0.84 1.65 171.59 0.81 1.45 149.52 0.74 1.15 131.47 0.70 0.97 114.42 0.67 0.80 92.54 0.60 0.58 73.76 0.56 0.43
Cat_3 1.72 17.28 201.12 0.84 0.81 184.03 0.81 0.71 160.40 0.74 0.56 141.32 0.70 0.47 123.23 0.67 0.39 99.69 0.60 0.28 79.31 0.56 0.21
Cat_4 1.48 19.02 192.07 0.84 0.66 175.68 0.81 0.58 153.10 0.74 0.46 134.71 0.70 0.39 117.32 0.67 0.32 94.89 0.60 0.23 75.59 0.56 0.17
Cat_5 1.14 16.26 206.45 0.84 0.55 188.95 0.81 0.48 164.71 0.74 0.38 145.21 0.70 0.32 126.72 0.67 0.27 102.52 0.60 0.19 81.50 0.56 0.14
Cat_6 0.63 17.84 198.24 0.84 0.29 181.38 0.81 0.25 158.08 0.74 0.20 139.22 0.70 0.17 121.35 0.67 0.14 98.17 0.60 0.10 78.13 0.56 0.08
Cat_7 1.62 29.40 156.68 0.84 0.59 141.68 0.81 0.51 122.44 0.74 0.41 107.32 0.70 0.34 93.81 0.67 0.28 75.43 0.60 0.20 60.13 0.56 0.15
Cat_8 3.43 23.17 175.58 0.84 1.41 160.21 0.81 1.23 138.84 0.74 0.97 122.11 0.70 0.82 106.38 0.67 0.67 85.92 0.60 0.49 68.42 0.56 0.37
Cat_9 1.56 27.85 161.01 0.84 0.58 146.01 0.81 0.51 126.15 0.74 0.40 110.72 0.70 0.34 96.69 0.67 0.28 77.85 0.60 0.20 62.02 0.56 0.15
Cat_10 3.43 20.14 186.49 0.84 1.49 170.52 0.81 1.31 148.55 0.74 1.04 130.60 0.70 0.87 113.66 0.67 0.72 91.92 0.60 0.52 73.27 0.56 0.39
Cat_11 1.86 18.91 192.66 0.84 0.84 176.22 0.81 0.73 153.57 0.74 0.58 135.14 0.70 0.49 117.70 0.67 0.41 95.20 0.60 0.29 75.83 0.56 0.22
Cat_12 1.69 16.89 203.17 0.84 0.80 185.93 0.81 0.70 162.06 0.74 0.56 142.82 0.70 0.47 124.57 0.67 0.39 100.78 0.60 0.28 80.15 0.56 0.21
Cat_13 0.76 30.86 153.33 0.84 0.27 138.50 0.81 0.23 119.66 0.74 0.18 104.81 0.70 0.15 91.62 0.67 0.13 73.61 0.60 0.09 58.69 0.56 0.07
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Components of time of concentration
(i) Estimate length of sheet runoff as per Table 4.06.3 and calculate travel time using Friends Equation (as per 4.06.6)
(ii) Kerb flow time (if applicable)
(iii) Pipe flow time
(iv) Creek and/or channel flow time
(i) Overland Flow (Section 4.06.6-Friends)
Notes: (1) Refer to Table 4.06.3 for estimated length of sheet flow
(2) Refer to Table 1 for Hortons roughness values
Catchment Cat_1 Cat_2 Cat_3 Cat_4 Cat_5 | Cat | Cat? | Cat8 | Cat_9 | Cat_10 | Cat_11 | Cat_1z2 | Cat_13
Estimated Length of Sheet Flow (Table 4.06.3) 100 100 100 100 100 100 100 100 100 100 100 100 100
Hortons Roughness Value 0.045 0.045 0.045 0.045 0.045 0.045 0.06 0.045 0.06 0.045 0.045 0.045 0.06
Slope (%) 6 5 5 3 8 4 2 4 2 6 4 6 1
tc (minutes) 15.59 16.17 16.17 17.91 14.72 16.91 25.90 16.91 25.90 15.59 16.91 15.59 29.75 0.00
(iv) Channel/Creek Flow
Note: Determine actual flow velocity from numerical modelling or the Manning Equation. Alternatively, if the expected travel time in the creek is not critical, assume an avergae flow velocity of
1.5m/s (not applicable to constructed channels)
Catchment Cat_1 Cat_2 Cat_3 Cat_4 Cat_5 | Cat | Cat? | Cat8 | Cat_9 | Cat_10 | Cat_41 | Cat_12 | Cat_13
Length of Channel Flow (m) 97 200 100 60 83 50 63 263 82 191 84 70 20
Velocity (m/s) - refer to Note 1.5 0.9 1.5 0.9 0.9 0.9 0.3 0.7 0.7 0.7 0.7 0.9 0.3 0.9
tc (minutes) 1.08 3.70 1.11 1.11 1.54 0.93 3.50 6.26 1.95 4.55 2.00 1.30 1.11 0.00
Catchment Cat_1 Cat_2 Cat_3 Cat_4 Cat_5 Cat_6 Cat_7 Cat_8 Cat_9 | Cat_10 | Cat_11 | Cat_12 | Cat_13
TOTAL tc (minutes) 16.67 19.88 17.28 19.02 16.26 17.84 29.40 23.17 27.85 20.14 18.91 16.89 30.86 0.00
Catchment Details
nee) Cat_1 Cat_2 Cat_3 Cat_4 Cat_s Cat_é Cat_7 Cat_8 Cat_9 Cat_10 Cat_11 Cat_12 Cat_13
Development = ~ = = - s ~ S = - = -
Area (ha) 3.355 3.779 1.716 1.483 1.137 0.63 1.62 3.43 1.56 3.43 1.86 1.69 0.76
Pre Development Flows
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Name (ha) (min) (mm/hr) (m/s) (mm/hr) (m/s) (mm/hr) (m/s) (mm/hr) (m/s) (mm/hr) (m/s) (mm/hr) (m/s) (mm/hr) (m/s)
Cat_i 3.36 16.67 204.31 0.84 1.60 186.97 0.81 1.40 162.98 0.74 1.12 143.65 0.70 0.94 125.31 0.67 0.78 101.39 0.60 0.56 80.62 0.56 0.42
Cat_2 3.78 19.88 187.64 0.84 1.65 171.59 0.81 1.45 149.52 0.74 1.15 131.47 0.70 0.97 114.42 0.67 0.80 92.54 0.60 0.58 73.76 0.56 0.43
Cat_3 1.72 17.28 201.12 0.84 0.81 184.03 0.81 0.71 160.40 0.74 0.56 141.32 0.70 0.47 123.23 0.67 0.39 99.69 0.60 0.28 79.31 0.56 0.21
Cat_4 1.48 19.02 192.07 0.84 0.66 175.68 0.81 0.58 153.10 0.74 0.46 134.71 0.70 0.39 117.32 0.67 0.32 94.89 0.60 0.23 75.59 0.56 0.17
Cat_5 1.14 16.26 206.45 0.84 0.55 188.95 0.81 0.48 164.71 0.74 0.38 145.21 0.70 0.32 126.72 0.67 0.27 102.52 0.60 0.19 81.50 0.56 0.14
Cat_6 0.63 17.84 198.24 0.84 0.29 181.38 0.81 0.25 158.08 0.74 0.20 139.22 0.70 0.17 121.35 0.67 0.14 98.17 0.60 0.10 78.13 0.56 0.08
Cat_7 1.62 29.40 156.68 0.84 0.59 141.68 0.81 0.51 122.44 0.74 0.41 107.32 0.70 0.34 93.81 0.67 0.28 75.43 0.60 0.20 60.13 0.56 0.15
Cat_8 3.43, 23.17 175.58 0.84 1.41 160.21 0.81 1.23 138.84 0.74 0.97 122.11 0.70 0.82 106.38 0.67 0.67 85.92 0.60 0.49 68.42 0.56 0.37
Cat_9 1.56 27.85 161.01 0.84 0.58 146.01 0.81 0.51 126.15 0.74 0.40 110.72 0.70 0.34 96.69 0.67 0.28 77.85 0.60 0.20 62.02 0.56 0.15
Cat_10 3.43 20.14 186.49 0.84 1.49 170.52 0.81 1.31 148.55 0.74 1.04 130.60 0.70 0.87 113.66 0.67 0.72 91.92 0.60 0.52 73.27 0.56 0.39
Cat_11 1.86 18.91 192.66 0.84 0.84 176.22 0.81 0.73 153.57 0.74 0.58 135.14 0.70 0.49 117.70 0.67 0.44 95.20 0.60 0.29 75.83 0.56 0.22
Cat_12 1.69 16.89 203.17 0.84 0.80 185.93 0.81 0.70 162.06 0.74 0.56 142.82 0.70 0.47 124.57 0.67 0.39 100.78 0.60 0.28 80.15 0.56 0.21
Cat_13 0.76 30.86 153.33 0.84 0.27 138.50 0.81 0.23 119.66 0.74 0.18 104.81 0.70 0.15 91.62 0.67 0.13 73.61 0.60 0.09 58.69 0.56 0.07