te auaunga awa - walmsley and underwood...
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Revision 0 – 30-Jun-2015 Prepared for – Auckland Council – ABN: N/A
Doc No. RPT-CI-1106_0_MODEL_RPT
Te Auaunga Awa - Walmsley and Underwood Reserves Project
Hydraulic Modelling Report
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
Revision 0 – 30-Jun-2015 Prepared for – Auckland Council – ABN: N/A
Te Auaunga Awa - Walmsley and Underwood Reserves Project Hydraulic Modelling Report
Client: Auckland Council
ABN: N/A
Prepared by
AECOM New Zealand Limited
T +64 9 967 9200 F +64 9 967 9201 www.aecom.com
Quentin Barbier
In association with
Boffa Miskell Limited
30-Jun-2015
Job No.: 60323936
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AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
Revision 0 – 30-Jun-2015 Prepared for – Auckland Council – ABN: N/A
Quality Information
Document Te Auaunga Awa - Walmsley and Underwood Reserves Project
Ref 60323936
Date 30-Jun-2015
Prepared
by Quentin Barbier
Reviewed
by James Hughes
Revision History
Revision Revision Date Details
Authorised
Name/Position Signature
A 30-Apr-2015 Draft for Review James Hughes
Design Manager
0 30-Jun-2015 Final Shaun Jones
Project Manager
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
Revision 0 – 30-Jun-2015 Prepared for – Auckland Council – ABN: N/A
Table of Contents
Executive Summary i 1.0 Introduction 1 2.0 Scope 2 3.0 Methodology 2 4.0 Model inputs 3 5.0 Model schematisation 3
5.1 Model components 3 5.1.1 Mike Urban 3 5.1.2 Mike 11 3 5.1.3 Mike 21 4
5.2 Model updates and assumptions 4 5.2.1 Model updates 4 5.2.2 Model assumptions and limitations 5
6.0 Model Peer Review 5 7.0 Model Results 6
7.1 Model validation (FHM comparison) 6 7.2 Model results 6 7.3 Discussion 7
8.0 Downstream Flood Effects 7
Appendix A Mannings Roughness Values A
Appendix B Peer Review Correspondence B
Appendix C Flood maps C
Appendix D Hendon Park Flood Modelling Results D
Appendix E Flood Hazard Map (FHM, 2011) E
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
Revision 0 – 30-Jun-2015 Prepared for – Auckland Council – ABN: N/A
i
Executive Summary
AECOM have been engaged by Auckland Council to carry out detail design of the Oakley/Te Auaunga Creek
rehabilitation project. This project involves widening and naturalising the watercourse running through
Walmsley and Underwood Reserves (between Sandringham and Richardson Rds).
This report covers the detailed hydraulic modelling undertaken which assesses the proposed channel
widening and its impacts on flooding.
The scope of the modelling work undertaken was as follows:
1) Develop a cutdown model from the original FHM model incorporating additional, more accurate details
such as survey data, updated LiDAR data and refined catchments.
2) Develop a new, widened channel cross section using 12D software, identifying specific hydraulic control
points where the channel capacity is insufficient to contain flood flows within the reserve area.
3) Develop design solutions to address the particular areas of reduced hydraulic capacity.
4) Incorporate the new channel design into the hydraulic model and rerun to confirm they achieve the
desired outcomes.
5) Extract, analyse and present findings.
Model Results
To evaluate the impacts on flood plains as a result of the design, the following design scenarios were run:
1) Existing 1 in 100yr ARI flows with existing stream
2) Existing 1 in 100yr ARI flows with proposed stream works
3) Proposed 1 in 100yr ARI ‘Pass forward’ flows (including MPD and climate change) with proposed stream
works.
The following tables summarise the results.
Table E1 Summary of flooded habitable floors and floors at risk
Scenario Habitable
floor at risk* Within 500mm
1) Existing Stream - Ex Flows 55 144
2) Existing Stream - PF Flows 82 143
3) Design stream - PF Flow 3 75
*Floors at risk: this indicates where the flood level is above the habitable floor level.
Table E2 Summary of flooded area and volume within floodplain
Scenario Area (ha) Volume of water (m3)
1) Existing Stream - Ex Flows 29.21 142,383
2) Existing Stream - PF Flows 30.77 167,642
3) Design stream - PF Flow 20.76 67,223
As shown within the above tables the proposed stream works achieve a significant reduction in both habitable
floors at risk and those within 500 mm of flooding. Main results are summarised as follows:
- With no change to the stream capacity, flooded floors would increase by around 50% (from 55 to 82).
There is little change to the number of floors within 500mm of flooding.
- The proposed stream works reduce the floors at risk by around 90% when compared to the existing
situation (from 55 to 3). Floors within 500mm are reduced by around 50% (from 144 to 75).
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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ii
- The proposed works reduce the flooded area by around 30% (29ha to 21ha) and the flooded volume by
around 50% (140,000m3 to 70,000m3).
Discussion
The proposed stream works have resulted in a significant reduction in the extent of the hazardous flood plain.
A potential consequence of this is that restrictions on development may be able to be reduced, which in turn
will enable future intensification within the area. This opportunity is not discussed further in this report,
however will be discussed in more detail as part of the Business Case for the project.
The proposed works have reduced flooding directly caused by the under-capacity of the stream channel and
associated culverts/bridges. There is still remaining flooding within the catchment caused by overland flow and
local depressions, particularly within the O’Donnell Rd area. This can be managed and addressed through
separate works, and will be part of additional investigations and analysis. These works will further reduce the
flood plain extent.
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
Revision 0 – 30-Jun-2015 Prepared for – Auckland Council – ABN: N/A
1
1.0 Introduction
The Oakley Creek project will achieve flood protection for a large proportion of the urban catchment to both
the north and the south of the creek. This report provides details of the development of the hydraulic model
and the comparison of the existing flood plain with that following the Oakley Creek widening works.
More recently, the extent of the floodplain has become a critical element of the project and reducing this has
become a key project driver. A cut-down model has been developed from the originally developed FHM model
(AECOM, 2013) and has been used as the base model to assess the extent of flood plain reduction. Refer
Figure 1 and Figure 2 below.
Figure 1 Cut-down model extent.
Cut-down model
Oakley Catchment
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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Figure 2 Cut-down model extent
2.0 Scope
The scope of the modelling work was as follows:
- Review the existing catchment-wide FHM model including hydrological assumptions.
- Build a base ‘cut-down’ model with refined network, inletting and hydrology and boundary conditions.
- Model the existing scenario and map the flood plain
- Model the proposed ‘Pass Forward’ scenario within the extsing Oakley Creek
- Model the proposed ‘Pass Forward’ scenario (including Oakley Creek widening, MPD land use and
climate change) and map the floodplain
- Assess flood plain area reductions and floor flooding
3.0 Methodology
The following methodology has been employed to determine pre and post development flood plain extents:
1) Develop a cutdown model from the original FHM model incorporating additional, more accurate details
such as survey data, updated LiDAR data and refined catchments.
2) Develop a new, widened channel cross section using 12D software, identifying specific hydraulic control
points where the channel capacity is insufficient to contain flood flows within the reserve area
3) Develop design solutions to address the particular areas of reduced hydraulic capacity
4) Incorporate the new channel design into the hydraulic model and rerun to confirm they achieve the
desired outcomes.
5) Extract, analyse and present findings
Cut-down model
extent
Oakley Creek
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Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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4.0 Model inputs
The following information has been brought into the cut-down base model:
- Data from previous FHM model (Boundary conditions: inflow hydrographs and water level time series)
- Updated GIS network data from Auckland Council (08/10/2014)
- Lidar Data (2013)
- AECOM Surveyed data (11/2014)
- Proposed 12D earthworks model
5.0 Model schematisation
5.1 Model components
The flood model is a 3 way coupled (MU, M11, M21) hydraulic and hydrological model. The following
summarises each component and Figure 3 below shows the extent of each.
Figure 3 Mike Flood representation of the three way coupled model
5.1.1 Mike Urban
All underground infrastructure is represented in Mike Urban including pipes, manholes and outlets. In addition,
all hydrology from the local catchments is represented in the Mike Urban model.
5.1.2 Mike 11
The stream and culverts/bridges at Sandringham Road extension, Beagle Avenue and Richardson Road are
all represented in the Mike 11 model. All sections have been extended beyond the extent of earthworks in
order to represent the same extent of the flood plain in both the existing and proposed models. Mike 11
sections have been extracted at 5m centres using the Mike 11 extraction tool in 12D.
Mike 11 network
Mike 21 bathymetry
Mike urban network
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Table 1 below summarises the range of cover types used, and the associated mannings roughness numbers.
These values are based on those provided by Auckland Council (23 Jan 2014) and take into consideration the
range of surfaces proposed within the flood plain.
In the existing model, the stream roughness have been set to 0.033, as an average value of the reserve
roughness.
The proposed roughness values were determined from the preliminary design landscape plans in
collaboration between the hydraulic modeller and landscape architect.
Appendix A summarises the Manning’s roughness values for the stream low flow channel, and both the left
and right flood plain independently – along the project length.
Table 1 Manning's Roughness
Main type of Coverage Assumed manning’s value
Low flow channel 0.03
Grass Floodplain 0.03
Light brush and trees 0.04 - 0.045
Medium to dense brush and trees 0.05
Exposed basalt 0.025
Concrete paths and wall panels 0.02 - 0.025
5.1.3 Mike 21
The remaining catchment topography (with the exception of the area covered by Mike 11) is represented in
Mike 21. The ground topography is represented in a 1m square grid developed using the 2013 LiDAR data.
Where available, the topographical survey has been spliced into the dataset and this is generally within the
reserve areas.
5.2 Model updates and assumptions
5.2.1 Model updates
The following table summarises the changes made, and compares the original FHM model with the ‘cut-down’
model.
Table 2 Summary of Model Changes
Items Original FHM Model Setup Model Updates for
Cut-Down Base Model
General Model Extent Oakley Catchment Model has been cut down to the extent of the
O’Donnell sub-catchment
Modelling Software Software Suite Mike by DHI version
2009. (Mike Urban, Mike 21 and
Mike 11).
Software suite Mike by DHI version 2012
with Service Pack 3. (Mike Urban, Mike 21
and Mike 11).
Hydrology Model B + RDI (with calibration) Model B hydrology only
Hydraulic Model –
Pipe Network
Refer to the section 3.4, in the OAK
SW Modelling Development Report
(AECOM, 2010).
Additional network (sourced from 2014 AC
GIS data) brought into the cut-down model to
refine the drainage representation within the
sub-catchment.
Hydraulic Model –
Surface Model
Mike 21 grid model (3m by 3m
square grid) generated from 2006
Lidar and SH20 design bathymetry
Mike 21 grid model (1m by 1m grid)
generated from 2013 Lidar.
Hydraulic Model – Modelled in Mike 11. Modelled in M11 based on topographical
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Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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Items Original FHM Model Setup Model Updates for
Cut-Down Base Model
Creek survey for existing and 12D design model for
future scenario.
Hydraulic Model –
Boundary conditions
N/A - Upstream boundary: Mike 11 inflow
were set from the original ‘Pass-
forward” model (based on MPD and
climate change factors)
- Downstream boundary: Water levels
were set from the same model as
above.
Hydraulic Model –
Soakage
- Private Soakage : can accept
the 10 yr. ARI flow
- Public Soakage : can accept
the10 yr. ARI flow
- Private Soakage : can accept the 2 yr.
ARI flow
- Public Soakage : can accept the2 yr.
ARI flow
Hydraulic Model –
1D and 2D Coupling
Refer to the section 3.9, in the OAK
SW Modelling Development Report
(AECOM, 2010).
- 20L/s inletting regulation applied per
catchpit on the manholes
5.2.2 Model assumptions and limitations
The following additional assumptions and limitations apply to the modelling work undertaken to date. Please
note that these need to be read in conjunction with the model assumptions and limitations specified in the
previous Oakley FHM model build report (AECOM, 2010).
- It is assumed that the boundary conditions at the study area are not changed by the works within the
study area.
- Streamworks design carried out in 12D
- Bridges have been designed with freeboard and single span such that the flow is essentially free surface
flow in open channels. As such we have represented the flow under each bridge in as open channel
sections in Mike 11. The existing and proposed box culverts at Sandringham Rd have been modelled
accurately.
6.0 Model Peer Review
A model peer review was carried out By Auckland Council in order to confirm fit for purpose. The findings from
this peer review were considered and incorporated were appropriate. An iteration of this review was carried
out and agreement was reached that the model is fit for purpose.
Correspondence related to the Peer Review is contained in Appendix B.
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Oakley Stage 1 Design
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Modelling Report
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7.0 Model Results
7.1 Model validation (FHM comparison)
In order to check and validate the cut-down model, this was compared with the original FHM model. As can be
seen in Figure 4 below, the flood extents are similar. There are differences in flood depths in places, and
much of this can be attributed to the improved accuracy of the terrain within the cut-down model.
Figure 4 Map showing comparison of original FHM results and result from ‘cut-down’ model
7.2 Model results
To evaluate the impacts on flood plains as a result of the design, the following design scenarios were run:
4) Existing 1 in 100yr ARI flows with existing stream
5) Existing 1 in 100yr ARI flows with proposed stream works
6) Proposed 1 in 100yr ARI ‘Pass forward’ flows (including MPD and climate change) with proposed stream
works.
The following tables summarise the results.
Table 3 Summary of flooded habitable floors and floors at risk
Scenario Habitable
floor at risk* Within 500mm
4) Existing Stream - Ex Flows 55 144
5) Existing Stream - PF Flows 82 143
6) Design stream - PF Flow 3 75
*Floors at risk: this indicates where the flood level is above the habitable floor level.
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Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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Table 4 Summary of flooded area and volume within floodplain
Scenario Area (ha) Volume of water (m3)
4) Existing Stream - Ex Flows 29.21 142,383
5) Existing Stream - PF Flows 30.77 167,642
6) Design stream - PF Flow 20.76 67,223
As shown within the above tables the proposed stream works achieve a significant reduction in both habitable
floors at risk and those within 500 mm of flooding. Main results are summarised as follows:
- With no change to the stream capacity, flooded floors would increase by around 50% (from 55 to 82).
There is little change to the number of floors within 500mm of flooding.
- The proposed stream works reduce the floors at risk by around 90% when compared to the existing
situation (from 55 to 3). Floors within 500mm are reduced by around 50% (from 144 to 75).
- The proposed works reduce the flooded area by around 30% (29ha to 21ha) and the flooded volume by
around 50% (140,000m3 to 70,000m3).
Flood hazard maps showing flooded floors and those at risk for each scenario, are included within Appendix
C.
7.3 Discussion
The proposed stream works have resulted in a significant reduction in the extent of the hazardous flood plain.
A potential consequence of this is that restrictions on development may be able to be reduced, which in turn
will enable future intensification within the area. This opportunity is not discussed further in this report,
however will be discussed in more detail as part of the Business Case for the project.
The proposed works have reduced flooding directly caused by the under-capacity of the stream channel and
associated culverts/bridges. There is still remaining flooding within the catchment caused by overland flow and
local depressions, particularly within the O’Donnell Rd area. This can be managed and addressed through
separate works, and will be part of additional investigations and analysis. These works will further reduce the
flood plain extent.
8.0 Downstream Flood Effects
The development of the project will result in increased peak flood flows at Richardson Road Bridge and
entering Hendon Reserve. This increase in peak flows, and the planning and design of mitigation has been
undertaken by the Well Connected Alliance as part of the Waterview Connection work.
The Well Connected Alliance has confirmed that the design and assessment of all work downstream of
Richardson Road has been undertaken for 100 year ARI peak flows of 58m3/s. This flow was stipulated by
Auckland Council during the design of Waterview Connection.
Due to design refinements since the Waterview Assessment of Effects was carried out, peak flows have
reduced to 54.4m3/s.
The Well Connected Alliance has designed and assessed a flood protection bund along the true right bank
downstream of Richardson Rd (refer Figure 5) in order to contain the peak flows within the reserve, and
protect properties along Hendon Ave. The modelling results developed by them are shown in Figure 5 below
and summarised in a memo (refer Appendix D). It should be noted that there is overland flow from Hendon
Ave that impounds behind the bund, however, this will be addressed by the Well Connected Alliance to
comply with Building Code requirements for management of surface flow and is not directly affected by the
stream flooding.
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Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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The Auckland City Flood Hazard Mapping project carried out in 2011 shows a smaller flood extent in the area
(for a peak flow of around 32m3/s). This is shown in Figure 6. The comparison between the two maps
illustrates that the impact of the increase in peak flow can successfully mitigated via the construction of the
bund.
Figure 5 Flood Modelling Results in Hendon Reserve
Figure 6 100yr ARI Flood Plain (ACC FHM, 2011)
Proposed
flood bund
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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Appendix A
Mannings Roughness Values
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Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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A-1
Appendix A Mannings Roughness Values
Chainage LH Flood Manning’s Low Flow Manning’s RH Flood Manning’s
10 0.03 0.03 0.03
60 0.05 0.03 0.05
90 0.03 0.03 0.035
110 0.045 0.03 0.045
180 0.045 0.03 0.05
240 0.045 0.03 0.045
310 0.05 0.03 0.05
350 0.05 0.03 0.045
390 0.03 0.03 0.03
400 0.05 0.03 0.045
460 0.04 0.03 0.05
500 0.03 0.03 0.03
510 0.02 0.03 0.02
540 0.04 0.03 0.05
550 0.03 0.03 0.03
570 0.045 0.03 0.04
670 0.045 0.03 0.03
760 0.045 0.03 0.05
800 0.05 0.03 0.05
900 0.045 0.03 0.05
960 0.03 0.03 0.03
980 0.025 0.03 0.03
1100 0.045 0.03 0.03
1340 0.03 0.03 0.03
1370 0.045 0.03 0.03
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Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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Appendix B
Peer Review Correspondence
Peer review comment AECOM response Outcome
The threshold values for flow exchangesbetween Mike Urban nodes and M21Bathymetry specified in the model varyfrom 0.5 to 3 cumecs. It is considered thatit would be difficult and expensive toprovide inletting capacities to this order.Please reconsider these values as thesehave an impact on the extent of flood plain.
The Values have been changed in themodel.
Made changes asrequested by Larry Shui
No open boundary has been set in themodel. When the results were inspected,it was found that land cell wall at theboundary damming up flows and evenbounce flows backwards and formed alarge ponding area as seen in the picturebelow.Suggest adding an open boundary at thislocation to enable drainage at thedownstream end of the bathymetry.M11 Model
Open boundary has been added. Made changes asrequested by Larry Shui
The DX value has been set at 10,000 mwhich is considered too large for a coupledmodel. The AC modelling specificationsuggest DX at Grid Size, in this case a DXvalue at 2m ~4m may be consideredappropriate
The Dx value have been set to 4 m Made changes asrequested by Larry Shui
Only the Sandrigham Road Culvert isincluded in the ‘Design’ model, none of thedownstream culvert or bridge structureshave been included in the model. Wouldsuggest that these structures be explicitlymodelled in M11, even that the flow willnever overtop, the entry and exit lossesshould be taken into account
The missing structures have beenadded
Made changes asrequested by Larry Shui
An only positive flow regulation has beenimposed on culvert and weir structures inthe ‘Existing’ model. If possible, these flowregulations should be removed
The flow regulations have beenremoved
Made changes asrequested by Larry Shui
Private and public soakage systems havebeen modelled with 10yr peak flowcapacity. It is considered that 2yr capacitymay be appropriate when modelling floodrisk given the often poor maintenance andpoor performance associated with agedsoakage system
The flow capacity has been adjustedon the 2y peak flow
Made changes asrequested by Larry Shui
Manhole cover type has been set asnormal. As this model will be coupled with2D terrain, it is considered that sealedcover top is more appropriate to avoid theartificial inundation cone automaticallyadded on top of manhole when overflowsin the Mouse Engine
The problem has been discussed withDragan from DHI and the manholesetup when coupled needs to be setas normal.
No changes have beenmade
Model B has been used as thehydrological model for this catchment.Default Model B parameters have beenadopted for all catchment’s, despite ofmany other set of Model B parametersdefined in the model file. Please alsochoose three example catchments andcompared the peak discharges with thosefrom TP108 analysis. As this model will beused to design new Stormwater pipes andall other Stormwater drainage pipes inAuckland Region are designed inaccordance peak flows from TP108analysis
Hi Quentin,It appears from your comparison ofthree subcatchments, the Model Bflow is higher than the TP108 peakflows by ~20%. We thereforeconsider that the flood risk from localcatchment predicted by the currentModel (model B) will be conservative,thus potentially err on the right side.
Based on above, my recommendationis continue on with the currenthydrological model (Model B) untilsuch time instructed by AC to switchto TP108 model for the whole Oakleycatchment.
Regards
Larry ShuiSWMPO
Provided the informations,no changes were required
Please confirm if AC Climate Changerainfall temporal patterns have been usedin the model
Climate change patterns have beenused in the model No changes required
I noticed an Evapo-Transpiratin time serieshave been included in the model, pleasecheck if this can be removed
The Evapo-transpiration have beenremoved
Made changes asrequested by Larry Shui
Terrain modifications at Walmsley Parkand Underwood Park included in themodel bathymetry changes but unable toverify due to the lack of design informationother than the model bathymetry.Consider modelling stream channel andstructures in 1D in M11.
The stream channel has beenmodelled in M11
Made changes asrequested by Larry Shui
Roughness grids representing the ultimategrowth in the reserve should be prepared.Roughness at the proposed overland flowpath and existing/future building platformsshould also be modelled appropriately.Correct representation of roughness inflood plain and overland flow paths.
This point hasn’t been addressed. No changes have beenmade
The upstream and downstream modelboundaries should be extended further outto ease out any errors in terms of hydraulicgrade lines at the area of concern due toincorrect conditions set at the boundary.Correct representation of upstreaminflow/hydraulic limitation and downstreamwater level conditions.
The bathymetry have been extendedfurther upstream
Made changes asrequested by Larry Shui
Peak water level from the local catchmenthas achieved. Although due to emission ofthe stream channel, the peak water levelsin the main channel flood plain areincorrect.Include the main stream channel in 1DM11 and couple 1D channel with M21.
The stream channel has beenmodelled in M11
Made changes asrequested by Larry Shui
No report on the initial condition. It isunclear whether any differences existbetween the initial water surface and thebathymetry terrain model.Please report on differences between theinitial water surface and the bathymetry.
There is no initial water surface in thestream, only around the boundarycondition for stability purposes.
Explanations provided
Suggest extending the bathymetry beyondRichardson Road bridge to minimiseeffects from assumptions of tail watererrors.
The bathymetry have been extended Made changes asrequested by Larry Shui
Further explanation of the “Pass Forward”flow required. Suggest considering usingmore self-explanatory terms, e.g. “Existing,MPD or MPD with network upgrade plans”
“Past forward” have been used in thereport used as it is the previous nameused in the model we extracted thedata.Is the flow crossing Sandrigham roadin the FHM model with an MPDscenario 100yr ARI + climat change +catchment wide mitigation scheme inplace.
Explanations provided
Further comments that did not required corrective action :
Model feature / parameter reviewedCorrectiveactionrequired
Comments / Review findings Expected Outcome
Software version and type ofbathymetry (classic, flexi mesh). No Mike Flood 2012/M21 classic grid used
appropriately
Model provided runs on AucklandCouncil computer system. How longdoes it take to run?
NoModel has been set up on ACcomputer; no simulation run has beenperformed.
Grid Size No 1m x 1m grids usedEddy viscosity No 0.1 usedWet and Dry threshold No 0.02 and 0.03m usedRainfall Used NoSimulation duration. Is thisappropriate? No 12 hr – simulation duration appropriate
Bathymetry drains appropriately at thefinal time step in the simulation No Ponding in depressions identified as
expected.
Obstructions such as buildings areappropriately modelled. Storage andvelocity are affected appropriately.
NoA roughness value of 0.2 is used tomodel resistance at current buildingplatforms.
Model fit for purpose? No
The current model lacks representationof the main stream channel and keyroad crossing structures. Likelyflooding of the area from the mainstream channel flood plain has notbeen modelled. The boundaryconditions especially at the downstreamside also requires further consideration.
Amended modelschematic to includemain stream channeland structures in M11coupled to M11. Useappropriate boundaryconditions.
Primary network ‘free ends’ No
1D Pipe network extends sufficientlyupstream to allow modelling of alloverland flow paths.
No
Network is sufficiently trimmedupstream. Catchpits are notmodelled.
No
All significant depressions and naturalponding areas are included in themodel extent.
No
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
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Appendix C
Flood maps
Oakley Creek Flood Extents
007
Existing Stream with Existing Flows
Project:
Title:
Status: Map No. Rev.Draft ARev. By App. Description
© Copyright AECOM New Zealand Limited, 2014. This map is confidential and shall only be used for the purposes of this project. © Copyright AECOM New Zealand Limited 2014.This map is confidential and shall only be used for the purpose of this project. The information contained orreferred to in this drawing-report was developed for use in the project. AECOM New Zealand Limited does notaccept any responsibility for the use of the information by any other parties and state expressly that they donot warrant the accuracy of the information. Any use of the information by other parties is at their own risk.The signing of this title block confirms the design and drafting of this project have been prepared and checkedin accordance with the AECOM Quality Assurance system certified to AS/NZS ISO 9001:2000.No part of this drawing/report may be copied or used without the prior written consent of AECOM New ZealandLimited.
Map features depicted in terms of NZTM projection.
Data Sources:NZ Topographical Features – LINZ NZ National Topo Dataset 2012Cadastral Boundaries – LINZ NZ Cadastral Dataset 2014
Scale:
P:\6
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SheetNo.
Ric
hard
son
Roa
d
Stoddard Road
Mount Albert Road
Sand
ringh
amRo
adEx
tens
ion
O'Donnell Avenue
Owairaka Avenue
Parkinson Avenue
Farrel lyAvenue
Potte
r Ave
nue
Hendon Avenue
Beag
leAv
enue
Aurora Avenue
Hedley Road
Triton Avenue
Tyburnia Avenue
Sheppard Avenue
LorraineA
venue
Hallam
Street
Denize
Road
Holdsworth Avenue
Taumata Road
Jessop Street
SkeatesAvenue
Belcher Street Shearer Street
Wainw
right Avenue
Thom
son
Stre
et
Mountfield
Terrace
Christ
iniSt
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Fletcher Street
McG
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lose
Delphine Close
Betts
Aven
ue
Buccaneer Street
Existing Stream with Existing FlowsFlooding Depth
0.0001 - 0.05
0.05 - 0.1
0.1 - 0.3
0.3 - 0.5
0.5 - 1
1 - 2
Floor Category
Within 500mm
Floor at risk
A QB JH For Options Report
0 60 12030 Meters1:3,000
Oakley Creek Flood Extents
007
Existing Stream with Pass Forward Flows
Project:
Title:
Status: Map No. Rev.Draft ARev. By App. Description
© Copyright AECOM New Zealand Limited, 2014. This map is confidential and shall only be used for the purposes of this project. © Copyright AECOM New Zealand Limited 2014.This map is confidential and shall only be used for the purpose of this project. The information contained orreferred to in this drawing-report was developed for use in the project. AECOM New Zealand Limited does notaccept any responsibility for the use of the information by any other parties and state expressly that they donot warrant the accuracy of the information. Any use of the information by other parties is at their own risk.The signing of this title block confirms the design and drafting of this project have been prepared and checkedin accordance with the AECOM Quality Assurance system certified to AS/NZS ISO 9001:2000.No part of this drawing/report may be copied or used without the prior written consent of AECOM New ZealandLimited.
Map features depicted in terms of NZTM projection.
Data Sources:NZ Topographical Features – LINZ NZ National Topo Dataset 2012Cadastral Boundaries – LINZ NZ Cadastral Dataset 2014
Scale:
P:\6
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\603
2393
6\4.
Tech
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Nam
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09Ju
n20
1516
:34
SheetNo.
Ric
hard
son
Roa
d
Stoddard Road
Mount Albert Road
Sand
ringh
amRo
adEx
tens
ion
O'Donnell Avenue
Owairaka Avenue
Parkinson Avenue
Farrel lyAvenue
Potte
r Ave
nue
Hendon Avenue
Beag
leAv
enue
Aurora Avenue
Hedley Road
Triton Avenue
Tyburnia Avenue
Sheppard Avenue
LorraineA
venue
Hallam
Street
Denize
Road
Holdsworth Avenue
Taumata Road
Jessop Street
SkeatesAvenue
Belcher Street Shearer Street
Wainw
right Avenue
Thom
son
Stre
et
Mountfield
Terrace
Christ
iniSt
reet
Fletcher Street
McG
ehanC
lose
Delphine Close
Betts
Aven
ue
Buccaneer Street
Existing Stream with Pass Forward FlowsFlooding Depth
0.0001 - 0.05
0.05 - 0.1
0.1 - 0.3
0.3 - 0.5
0.5 - 1
1 - 2
Floor Category
Within 500mm
Floor at risk
A QB JH For Options Report
0 60 12030 Meters1:3,000
Oakley Creek Flood Extents
007
Design Stream with Past Forward Flows
Project:
Title:
Status: Map No. Rev.Draft ARev. By App. Description
© Copyright AECOM New Zealand Limited, 2014. This map is confidential and shall only be used for the purposes of this project. © Copyright AECOM New Zealand Limited 2014.This map is confidential and shall only be used for the purpose of this project. The information contained orreferred to in this drawing-report was developed for use in the project. AECOM New Zealand Limited does notaccept any responsibility for the use of the information by any other parties and state expressly that they donot warrant the accuracy of the information. Any use of the information by other parties is at their own risk.The signing of this title block confirms the design and drafting of this project have been prepared and checkedin accordance with the AECOM Quality Assurance system certified to AS/NZS ISO 9001:2000.No part of this drawing/report may be copied or used without the prior written consent of AECOM New ZealandLimited.
Map features depicted in terms of NZTM projection.Data Sources:NZ Topographical Features – LINZ NZ National Topo Dataset 2012Cadastral Boundaries – LINZ NZ Cadastral Dataset 2014
Scale:
P:\60
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SheetNo.
Design stream with Past Forward FlowsFlooding Depth
0.0001 - 0.050.05 - 0.10.1 - 0.30.3 - 0.50.5 - 11 - 2
Floor CategoryWithin 500mmFloor at risk
A QB JH For Options Report0 60 12030 Meters1:3,000
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
Revision 0 – 30-Jun-2015 Prepared for – Auckland Council – ABN: N/A
Appendix D
Hendon Park Flood Modelling Results
140-J003-WMS
The Well-Connected Alliance 150-152 Stoddard Road, Mt Roskill, Auckland 1041 Private Bag 76914, Manukau Mail Centre 2104 P +64 9 621 1730 E [email protected]
www.nzta.govt.nz/waterviewconnection www.twitter.com/wcnow Rev 3 January 2015
1
……………………………………………………..……………………………………………………………………………………………………………………………………………………………………
MEMO ….……………………………………………………………………………………………………………………………………………………………………………………………………………………….
Doc No.:
400-CMT-M-09524.
To: Auckland Council c/o – Tom Mansell
Cc: Sumi Eratne (NZTA) Shaun Jones (Aecom)
From: Keane Kannan
Date: 10/05/2013 3:00:00 pm Subject: Hendon Park Flood Modelling Results
IntroductionThe following memorandum has been provided to Auckland Council (Council) for information. We understand
that Council propose to use this information to assess flood levels within the wider Hendon Reserve area in
particular to the north of the reserve.
The purpose of our assessment was for the design of the bund along the northern and western extents of the
reserve to confine Oakley Creek flows and protect the southern approach trench and tunnel portal from flood
inundation.
The model run assessed is the 100 year ARI climate change adjusted model with MPD. This includes the pass
forward flows from the upstream development of the Oakley Creek above Richardson Road. The peak pass
forward flow assessed is for 58 m3/s as provided by Council. We note that the flood level within Hendon Park
is controlled downstream by the SH20 Oakley Bridge which has been designed to pass this peak flow.
ModellingResultsThe following figures 1 and 2 show the modelled flood depths and flood elevations within the Hendon
Reserve. The flood map shows all flood depths greater than 50 mm in accordance with Council modelling
guidelines.
We note that in Figure 2, the wider flood plain shows the maximum flood elevation and includes areas that are
subject to 50mm of flooding and less.
DisclaimerThe modelling undertaken by the Well Connected Alliance has been prepared for a specific purpose and brief.
The information provided may not be suitable for use outside of the subject area and if used should be
checked independently.
2
Figure 1 – 100 year ARI flood depths within Hendon Park
Figure 2 – 100 year ARI Flood Elevations within Hendon Park
Water depth
(m)
Water level
(m RL)
AECOM
Oakley Stage 1 Design
Te Auaunga Awa - Walmsley and Underwood Reserves Project – Hydraulic
Modelling Report
Revision 0 – 30-Jun-2015 Prepared for – Auckland Council – ABN: N/A
Appendix E
Flood Hazard Map (FHM, 2011)
44.12
42.93
9
653
42
1
9
2
57
3
9
4
8
6
7
8
3
5
53
7
10
15
13
59
57
56
62
64
54
2927
3638
40
13
11
1517
3133
35
42
37
39 54
52
50
1113
17 15
162018
55
44
5153
42
1715 2119
30
10
1214
195
215
217
131
124
223
221
190
192
219
236
238
229
231
233
235
116
118
225
227201 19
9
193
189
197
203
183
175177
170172
174
179
171
185
187
191
181
234
211
223
161163
168
164166
173156
167169
171
134
138
142
140
154
165
117
119
121
123
109111
110
112114
113115
174
179
168 170 172
183
189 193
176
185 187
136
160
158
164166
175177
132
126128
132
130
137139
134
143
141
145136
138140
142
147
151149
159161
163
153155
157
144
146148
150
152
143
145
141
139
135
133
125
137
131129
127
130
173
207188
209
211
213
186205
101
102
107
103105
108
4-6
100
195
203199
197
205
206
204
200
196
129
116 118 122120
6-8
195A
217A
113A
128A
203A
129A
58-60
23-25
44-46
10-12
14-16
48-50
32-34
206-210
204-2
08
192-198
210-2
20
212-220
180-182
104-106
192A-202B
HENDON AVENUE
ALAM
EIN
TERR
ACE
CASSINO TERRACE
FLETCHER STREET
BARRYMORE ROAD GL = 43.1m100yr = 43.5m50yr = 43.4m10yr = 43.4m
GL = 45.3m100yr = 46.0m50yr = 45.8m10yr = 45.5m
NL4774
NL4773
NL4740
d010S062_out
d003S059_out
d003S052_out
d003S060_out
NL3382
NL3380
NL3379
NL3377
Node_256
Node_183
Node_179Node_178 Node_177
SENS8512
SENS7795
d010S062
d003S059
d003S052
d003S060
SGNS7795
Node_176
Node_175
CO_NS1199CO_NS1198
CWOAK_DN7
CWOAK_DN4
CWOAK_DN3
SGNS7795Dummy
NS8512Private
CO_CWOAK_DN127CWOAK_DN5
CWOAK_DN2
NS8512DummyNS8512Public
SGNS7795Private
47
50
50
45
41
45
48
42
49
45
47
42
43
48
48
49
47
45
4442
47
50
47
44
49
47
48
44
43
46
49
4348
41
49
52
48
45
46
42
44
49
42
45
42
43
43
43
46
49
46
51
43
53
48
43
47
52
50
42
51
46
47
47
47
48
43
4848
AMENDMENTSREV BY APPd DATE NAME DATE
APPROVED
DRAWNDESIGNEDCHECKEDSTATUSPRINTEDFILE NAME
KEY PLAN
Figure 4.Predicted Maximum Probable Development Flood Hazards
Notes:
Scale:20 0 20 40 60 Metres
1:2,000
© 2010 Metro Water Limited and Auckland City Council. All rights reserved.Information contained in this drawing/report is confidential and proprietary toMetro Water Limited and Auckland City Council. No part of this drawing/reportmay be copied or used without the prior written consent of Metro WaterLimited and Auckland City Council.
Flood plains and overland flow paths represent modelled surface profiles. Freeboard has not been included.The Building Footprint dataset has been digitised from February 2002 orthoimagery. The data has not been updated since. The data accuracy is acombination of spatial accuracy of the orthoimagery and manual digitising.
These maps must be read in conjunction with the Flood Hazard Mapping Report.
GL means Ground level at node point or lowest point on cross-section.
(A3 size)
Map projection is NZTM.
21OAK_Fig4x_MPD_FHM.mxd
FLOOD HAZARD MAPPING OF CATCHMENTSON THE AUCKLAND ISTHMUSOakley Hazard Mapping
The information contained or referred to in this drawing/report was developedfor use in the project known by Auckland City Council and Metro WaterLimited as Flood Hazard Mapping of Catchments on the Auckland Isthmus.Neither Auckland City Council nor Metro Water Limited accept any responsibilityfor the use of the information by any other parties and state expressly that theydo not warrant the accuracy of the information. Any use of the information by other parties is at their own risk.
Areas beyond modelled network may have flood hazards and flood prone areas;These have not been modelled and are therefore not represented.Network usage is as modelled and may differ from AMIS GIS data.
P. Fearon
Final
01/10/2010
4.16
4.21
4.26
4.224.20
4.27
4.15
4.25
4.17
01/10/201001/10/201001/10/201001/10/2010
M. Summerhays
S. JonesP. Fearon
LEGEND:
Modelled Stormwater NodeModelled Soakage (Representative Only)
Property BoundariesSW Catchment Boundary
Survey CrossSection1m LIDAR ContoursModelled Stormwater NetworkModelled Open ChannelModelled Stormwater Culvert
Wastewater Overflow(10, 50 & 100 Year ARI Events)
Building Footprints (Floor Level)
50yr Site assessed floors within 500mm
50yr Site assessed floors at risk
50yr Surveyed floors within 500mm50yr Surveyed at risk
DraftAFinal0
PF MJSPF MJS
30/06/1001/10/10
Layout For "Hazardous Areas"
Flood extent confirmed on site. Contours in thisvicinity not reliable.
Significant Hazard Overland Flowpath (50yr)Significant Hazard Overland Flowpath (10yr)
Significant Hazard Flooding (10yr)Significant Hazard Flooding (50yr)Significant Hazard Flooding (100yr)
Highest Astronomical Tidal Flood Plain
Potential Overland Flowpath or Low Hazard Flooding (50yr)
Potential Overland Flowpath or Low Hazard Flooding (10yr)