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Development Application - Part 2 of 2 - Report & Plans · OPW11/0116
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SCRC CORRESPONDENCE
THIS IS THE NEXT PART OF A
MULTIPLE PART RECORD
Part 2 Of 2
Application number: c, R,.sw c
6 - APR 2011
Nambour
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Queensland
Government
Author C harmcune [lake
File ! Rct number 20116(11W24 Environment and Resource
I)irectcnate; I na State Land Asset Management
Management
Phone (07154512241
19 January 2011
Attn: Bobbie Corbett
International Coastal Management
P0 Box 306
MAIN BF,ACI1 (1Li) 4217
Dear Bobbie
RE: RESOURCE ENTITLEMENT APPiICATION - LOT 114 ON MCH839107,
NODS; RINI'll SPIT
Reference is made to your request for evidence of resource entitlement required to
accompany your development application for proposed erosion protection works.
I wish to advise that the proposed development is consistent with an allocation of, or an
entitlement to, the resource. A copy of this letter is to he attached to your IDAS Form 1 as
the required evidence for Table G.
Although evidence of resource entitlement to your development application has been
provided, you are always required to comply with the purpose, ternis and conditions of your
"tenure" over Lot 1 14 on MCl1839107 and undertake works only if and when the
development application has been approved by the assessment manager, and in accordance
with the conditions of that appro\ al.
You will also need to comply with all other legislative and regulatory requirements which
may also include approvals that are not part of the assessment of the development
application under the Sustainable Planning Act 2009 (SPA) e.g. a marine park permit if in a
marine park.
Further, please note that the above e\ idence will expiry on 19 January 2012. Should the
development application not he lodged with the assessment manager prior to this date. you
will he required again to lodge the IDAS Form I and any attachments with this Department
ith a further request Fur evidence of resource entitlement - any further request will need to
he reconsidered by the Department.
O MCC : Po%tal : I clephone (07 )54512215
I I R\1 Nambour ULRM Nambour Fat 5•l 12262
Fl. as I. Centenary Square N) lio\ 57:
Currie Street Namhuur
Nanihow Q1.0 45(,0 4560 ioLD
Page 4
I would also like to advise that any land use activities must comply with the :lboriginal
('uhural Ile'rilage..l cI 20(13 or the Torres Struil Ahoule r HeritageAcv 2003
Finally. providing evidence of resource entitlement is required under SPA to enable your
application to he considered properly made for lodging with the assessment manager and is a
completely separate process to assessment of the application under SPA.
Accordingly. the Department may act at a later date as assessment manager.
concurrcncerreferral agency. or ad%ice agency in the assessment of the development
application - providing evidence of resource entitlement will not influence any statutory role
the Department may have in this assessment.
If you wish to discuss this matter please contact Charmaine Duke on (07)545 12243.
All future correspondence relative to this matter is to be referred to the contact Officer at the
address below or by email to S1::AM1-Namhour2 il!demi.gld.gov.au. Any hard copy
correspondence received ill he electronically scanned and filed. For this reason, it is
recommended that any attached plans, sketches or maps he no larger than A3-sized.
Please quote reference number 2010/009024 in any future correspondence.
Yours sincerely
Renee (:rant
Senior Land Officer
A duly authorised delegate of the Chief Executive
under the current Land Act (Chief Executive) Delegation
Page 5
suvoh EASING t10N11MIG
5c-;r4 'CB'9x
50Ny4 "38'930
50178E `38'511
f07d80 MM
Proposed Works within Water Allocation
Area:
• Existing rock wel (maintain I upgrade)
• Submerged channel closure
• Wall at end of Noose River Spit
• Groyne / Training Wall
• Dredging for Interim navigation
• Foreshore nourishment
• Removal of dead trees (marine plants)
as required
[works as shown are Indicative only).
Works are anticipated to be generally as per
drawings NRS-001 to -011. Works maybe
modified as a result of:
• Changes to entrance configuration or
erosion events pro-construction.
• Detailed design
• Modifications agreed during the
approval process.
No works within Noose River Fish Habitat
Area
0
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Coastal
Management
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Page 6
International
Coastal eco engineered coastal solutions
Management
CONCEPT CONSTRUCTION MANAGEMENT PLAN
NOOSA RIVER SPIT
EROSION PROTECTION WORKS
prepared for
SUNSHINE COAST REGIONAL
COUNCIL
by
INTERNATIONAL
COASTAL MANAGEMENT
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Page 7
International
Coastal eco engineered coastal solutons
Management
Document Control Sheet
Prepared by: Aaron Salyer
Title: Coastal Engineer
Company: International Coastal Management
Final Review: Bobbie Corbett
Title: Senior Coastal Engineer
Company: International Coastal Management
Approved for release: Bobbie Corbett
Title: Senior Coastal Engineer
Company: International Coastal Management
Version History
Version No. Date Changed by Nature of Amendment
Rev A 5.4.11 Bobbie Corbett Acid sulphate revised.
Marine plants revised
This document has been produced by International Coastal Management Pty Ltd (ICM) in accordance with the terms and
limitations of the brief by SCRC. In preparing this report, ICM has used information provided by the Client and others
identified herein. ICM does not and shall not assume any responsibility or liability whatsoever to any third party arising out of
any use or reliance by any third party on the content of this document. This document is not to be used without the express
approval of SCRC.
International Coastal Management i -, t (ICM)
^.n ,,( L . n 5vC Ma- a Mani Beach Ud 4217 AustraUa
P. E 3U' hten ht-,j(, I NO Main Beach Old 4217 Austral
•i' •61 7 5564 05b4 em •61 7 5532 9147
^ n www mavalmawMmbnr rfvr. aYl
Page 8
International
Coastal eco-engineered coastal solutions
Management
TABLE OF CONTENTS
1. SITE LOCATION .......................................................................................................................................................1
2. INTENT OF CONCEPT CONSTRUCTION MANAGEMENT PLAN .............................................................................2
3. DESCRIPTION AND PURPOSE OF WORKS ............................................................................................................2
4. RELEVANT APPROVALS ......................................................................................................................................... 3
5. CONSTRUCTION ...................................................................................................................................................... 4
5.1 Equipment 4
5.2 Methodology for Dredging I Nourishment 4
5.3 Methodology for Filling Containers 4
6. SUMMARY OF KEY ENVIRONMENTAL ISSUES ......................................................................................................4
6.1 Water Quality 5
6.2 Noise 5
6.3 Flora & Fauna 5
6.4 Acid Sulphate 7
6.5 Cultural Heritage 8
6.6 Waste Management 8
6.7 Air Quality Management 8
6.8 Flammable and Combustible Materials 9
6.9 Greenhouse Gas Emissions 9
7. ENVIRONMENTAL MANAGEMENT MONITORING REQUIREMENTS ......................................................................9
8. CONTINGENCY PLANS & EMERGENCY PROCEDURES ........................................................................................9
International Coastal Management (ICM)
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Page 9
1. SITE i OCAT!ON The site is located within the Noosa River entrance [Figure 11 adjacent to the Noosa River Spit. The works are located outside the Noosa River Fish Habitat Area [Figure 2]. Figure 1: General Site Location [see Figure 2 for inset] Figure 2: Extent of Works There is a tidal range of approx 2m [QT tide tables]. The site protected from ocean swell and seas by Noosa Spit and shoals within the entrance. Spring tidal velocities within the southern channel can be up to 1.5m/s, although this may change with channel configuration. The channels and shoal configuration is highly variable.
Page 10
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This Concept Construction Management Plan is intended to provide an indication of how works may be undertaken by the
contractor, likely environmental impacts and intended control measures.
The contractor is to prepare a final construction management plan prior to commencing works and a copy is to be provided to
DERM. The contractor's methodology, plant, equipment, scheduling etc may vary from that indicated here. Any changes to
the intended methodology that may increase the impact of the works is not to be implemented without further discussion with
DERM.
3. DESCRIPTION AND PURPOSE OF WORKS
With the exception of those areas already protected by rock works, Noosa River Spit is currently experiencing erosion along
its full length, including the southern end of the Noosa River Spit. While this is reducing amenity along what was once a
popular recreational beach, there is also the potential for continued erosion to breach the Noosa River Spit, which could have
very serious impacts.
A number of options were considered [ICM 2010 report]. The preferred option includes [Figure 3]:
• Submerged curved "closure" [sand-filled geotextile mega-containers] designed to create an enclosed, stable
beach and lagoon area
• Dredging for interim navigation and associated foreshore nourishment
• Training wall [sand-filled geotextile mega-containers] to provide a control point for the southern channel
• Wall [sand-filled geotextile mega-containers] to prevent erosion along southern end of the Noosa River Spit
• Two groynes [2.5m3 sand-filled geotextile containers] to stabilize the upstream beach
Figure 3: Proposed Strategy
Page 11
A staged approach of construction is being adopted and this construction plan is relevant only for Stage 1 of the works
[Figure 4]. Stage 1 includes:
• Retain existing rock wall [maintain / upgrade as required]
• Submerged channel closure [partial]
• Wall at end of Noosa River Spit
• Groyne I Training Wall
• Dredging for interim navigation (location to be determined)
• Foreshore nourishment
• Removal of dead trees (marine plants) as required
• Widening of access track
The submerged channel closure, wall and groyne are to be constructed using sand-filled geotextile mega-containers.
Submerged Closure
Crest at low Tide
Dredging
Nourtshment
Wall
Creel at surface level
[approx high tide]
Figure 4: Proposed Stage I Works [preliminary design]
4. RELEVANT APPROVALS
The following approvals are being sought:
o Resource Entitlement
o Prescribed tidal works
o Interfering with Marine Plants
o ERA 16 1(b)
o Registration Certificate
o Clearing (Nature Conservation Act)
Page 12
5. CONSTRUCTION
There are a number of ways in which these works could be achieved and the final methodology is at the discretion of the
contractor.
5.1 Equipment
It is anticipated that the works (depending on the methodology) may require the use the following major equipment:
• 6" or greater cutter suction dredger and pipeline
• Jet pump (suspended or hopper-fed)
• Barge
• Support vessels
• Excavator
• Bobcat
5.2 Methodology for Dredging I Nourishment
The dredge area is to be located accurately using DGPS or suitable alternative. Dredging is to be undertaken slowly to
minimise turbidity. Dredging is to be undertaken in such a way that it does not block navigation once a suitable channel is
established.
Nourishment is to be achieved generally by relocating the pipeline periodically within the deposition area. Small earthmoving
equipment may be used to redistribute material on the visible beach to achieve final nourished profiles. This may be more
difficult to achieve given the presence of significant dead tree material on the foreshore. As the slopes are the same as
existing, final profiling below low tide will likely be achieved by tidal velocities.
5.3 Methodology for Filling Containers
Filling sand-filled geotextile containers can be undertaken in a number of ways. The simplest methodology includes the
following
1. Dredge along the structure alignment to achieve the design depth
2. Roll out empty container
3. Secure in location with anchor blocks
4. Fill container using dredge (while excavating for the next container, per step 1)
5. Seal trunks
There are a number of potential variations to this generic methodology. These include:
• Excavation for containers may source nourishment and container fill may be sourced from the dredging of channel.
• Containers may be filled using a jet-pump suspended from a barge-mounted excavator.
• Containers may be filled from an onshore stockpile using a hopper-fed jet pump.
• Material may be double handled in some cases.
• A frame may be used to secure the container instead of anchor blocks.
• Use of temporary bunds may be considered in some locations to stabilise containers during the initial stages of
filling. These are to be removed upon completion of the works where backfilling isn't necessary.
It is noted that the works will require the use of divers.
6. SUMMARY OF KEY ENVIRONMENTAL ISSUES
The works are adjacent to (but not within) the Noosa River Fish Habitat Area. The areas to be dredged are not within a
Marine Park
Page 13
The following outlines potential impacts of the works. Works are to be undertaken in such a way that impacts are minimized
wherever possible. Monitoring to ensure that any impacts are within acceptable levels is detailed below.
6.1 Water Quality
The dredge will operate in such a way to minimise turbidity during dredging operations.
To ensure that water quality [pH, DO, Turbidity] remains within acceptable limits, visual monitoring of the plume is to be
undertaken as well as any required water quality testing in accordance with ERA requirements. Visual observations for oil,
grease, floating scum and litter is to be carried out on a regular basis.
6.2 Noise
The works are separated from the businesses and resorts on Hastings St by at least 620m of well-developed vegetation. It is
not anticipated that works will cause an issue in this area. The dredging, submerged closure and training wall / groyne, the
plant will be over 400m from the residences of Noosa Sound and separated by 60m of well-vegetated area on Noosa River
Spit. When undertaking the wall at the end of Noosa River Spit, the works will be within 350m of the residences on Quamby
Place (Noosa Sound) and noise could potentially be an issue, particularly outside of normal working hours.
The Contractor shall take all reasonable precautions (e.g. the use of mufflers) and undertake works in such a way as to
minimize the potential for noise nuisance to residences and businesses and meet the requirements of the ERA conditions.
Given the nature of the work and the environment, there will be a need to work in conjunction with the tides and so works
may need to be undertaken outside of normal working hours. There is no restriction on working hours provided that the
required noise limits are met.
An aural inspection is to be undertaken daily and if any issues are identified or complaints are made regarding noise levels,
noise monitoring compared to nominated levels is to be undertaken if works are to continue in this area.
6.3 Flora
Due to the mobility of the channels and shoals and the high erosion rate, the area is characterized by a clean sandy seabed
(Figure 5). There are no seagrass beds present within the footprint of the proposed works.
Figure 5: Sandy shoal
The only mangroves within proximity of the works are at the south-eastern end of the wall at the end of the Noosa River Spit
(Figure 6). The wall terminates adjacent to the mangroves, but works are to be undertaken in such a way that no mangroves
are to be interfered with as part of the works.
Page 14
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Figure 6: Mangroves at SE end of proposed wall
Due to the high rate of erosion there are a number of large dead trees along the length of the foreshore (Figure 7). These
are typically well-established trees. The number of trees is unknown, but they cover an area of approximately 7700m2.
These trees are classified as marine plants as they are within the tidal zone. It will be necessary to remove these trees to
allow for construction.
Where excavation is taking place, the full tree should be removed [although this may need to be done progressively during
excavation] to prevent blockages of the dredge pipeline and ensure that organics are not used to fill the container or sharp
sections remain where they could potentially result in damage to the containers. In other areas [i.e. where nourishment is
taking place or within work areas], trees may be trimmed at the required depth [approx 0.3m below surface], sufficient to
allow for access without damage to equipment.
"• - _ try ^'^_^- ^- _r^- .5
Figure 7: Dead trees along Noosa River Spit
There is a reasonable access path to site from the carpark. Part of the works will include slight widening of this track as
required to allow access for construction equipment. Given the low-lying nature of the track, the majority of the trees will be
classified as marine plants, however a small number adjacent to the carpark are above HAT and are not marine plants.
Page 15
Figure 8:Existing path to site
Arborists have advised that the following methodology would be most beneficial and is to be followed as much as
practicable:
• Removal of branches >6" diameter and placement within Noosa Spit and Noosa Woods (above HAT) as fauna
habitat
• Heavy trimming of remaining trees, stockpiling and mulching. Mulch to be utilised for rehabilitation along access
track and site perimeter.
• Removal of remainder of tree litter unsuitable for mulching for disposal at an appropriate location ashore.
Removal of trees and mulching to be undertaken by separate, experienced contractors prior to commencement of other
works.
An offset programme has been developed to compensate for the loss of habitat as a result of the works and this is provided
as a separate report.
6.4 Acid Sulphate
Sediment testing was undertaken on 4m and 5t' January 2011 by Coffey Geotechnics. The sediment is fine-medium grained
sand with low (<5%) fines content.
While the surface sediments are clean sand suitable for nourishment, acid sulphate soils (both AASS and PASS) were
identified within some of the deeper areas. Below is the table from the Coffey Report.
The dredging for interim navigation and excavation for the construction of the submerged closure does not disturb acid
sulphate soils.
Dredging / excavation for the wall and training wall / groyne at the end of Noosa River Spit does disturb some acid sulphates
below RL-4.75m AHD. As such, all material dredged / excavated from below RL-4.5m AHD is to be placed below LAT (i.e.
used for filling deeper containers or as backfill adjacent to the toe).
Page 16
Component of Works Depth Liming Rates (kglm)
Above RL -4 75 metres AHD Nil
WaIU Groyne Below RL -4.75 metres AHD 8
(SI -S4)
Below RL -5.5 metres AHD
50
around S4
Submerged Closure Above RL -6 45 metres AHD Nil
(S5-S7) Below RL -6 45 metres AHD 50
Dredg n
Above RL -3 25 metres AHD Nil
(S8-SP)
Note No disturbance is expected for the Submerged Closure area below RL -6 45 metres AHD or within the
Dredging area below RL -3 25 metres AHD
6.5 Cultural Heritage
The Noosa River Spit was artificially reclaimed in 1978 and there has been significant dredging within the river over recent
years. There are no identified areas or items of cultural significance within the proposed area of the works, although a
cultural study can be undertaken if required.
If any potentially culturally significant items are found, the contractor will cease works immediately and advise the
Superintendent. The Superintendent will notify the traditional owners to seek their advice before works in that area can
continue.
6.6 Waste Management
The sandy material from dredging / excavation will be used for filling containers, backfilling and foreshore nourishment within
the vicinity of the works. The sediment type is very consistent across the footprint of the works and is suitable for this
purpose.
Other wastes (rubbish etc) may be temporarily stored on site if adequately contained. The Contractor is responsible for
ensuring that all waste is disposed of at suitable onshore facilities. Every effort is to be made to ensure that litter and other
debris does not enter the waters. Any material or objects dropped onto the bed are to be recovered. Visual monitoring is to
be undertaken.
The seabed is to be checked prior to completion of the works. All waste materials (including anchor blocks and ropes used
during construction) are to be removed and not buried or left on the seabed.
The contractor is to implement an oil spill management plan.
It is not anticipated that any regulated waste will be generated as part of the works.
6.7 Air Quality Management
Air emissions from plant and equipment are to be monitored visually to ensure air quality is acceptable throughout the works.
Exhaust is to be within the specifications of the equipment and all required maintenance is to be undertaken.
Page 17
6.8 Social
Any complaints are to be investigated and responded to in a prompt manner. The Superintendent is to be notified of any
complaints as soon as practicable. A suitable complaint register is to be kept.
6.9 Flammable and Combustible Materials
A list of all flammable and combustible materials, chemicals or any other potentially hazardous substances is to be noted on
the MSDS register.
6.10 Greenhouse Gas Emissions
All machinery is to be regularly maintained and operated in accordance with specifications to minimise possible greenhouse
gas emissions.
7. ENVIRONMENTAL MANAGEMENT MONITORING REQUIREMENTS
Monitoring requirements are to be as below, in addition to any ERA Licence requirements.
Issue _ Monitoring Frequency/Timing Performance Criteria Responsibility
Water Quality Visual Inspection Daily during dredging No visible turbidity Contractor
hours plume from dredging
>200m from the
dredge site.
No visible al, grease,
floating scum or litter
Noise Aural inspection of Weekly during Noise levels in Contractor
equipment for dredging accordance with
excessive noise. equipment
specification.
Investigation of noise As required in Complaints responded Contractor
complaints response to any noise to within 24 hours
complaints
Air Quality Visual inspection for Daily during dredging No excess machinery Contractor
excess machinery hours exhaust
exhaust emissions
Waste Management Visual inspection of Daily during dredging No uncontained litter Contractor
site for floating debris hours waste
for barge/dredge
8. CONTINGENCY PLANS & EMERGENCY PROCEDURES
Should any non-confirming results be observed or recorded, works are to suspended immediately and the Superintendent is
to be notified. A procedure for non-conformance is prepared for each Project. This procedure incorporates:
• Work Instructions issued
• Non Conformance Report Form
• Reporting Procedure
• Corrective Action
A number of specific detailed contingency plans are to be prepared and include an oil spill management plan and a waste
management plan.
Page 18
International
Coastal
Management
OPTION REVIEW
NOOSA RIVER SPIT
IMemationai Coastal Managme l t • - - (1CM)
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Page 19
International
Coastal
Management
OPTION REVIEW
NOOSA RIVER SPIT
prepared for
SUNSHINE COAST REGIONAL
COUNCIL
by
INTERNATIONAL
COASTAL MANAGEMENT
International Coastal Management ^ -^ . (ICM)
-a 50 r 0 Arm SYC Marina Miin Bcach O:C 4217 Ausuaha
•- P3 3cx 306 Ma", Beach L =O Main Beach 0 c 4^ 1' Austi
nuntw . 61 7 55f40564 w -61 7 5532 914 7
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Page 20
International
Coastal eco-engineered Co i^1a
Management
Document Control Sheet
Prepared by: Bobbie Corbett
Title: Senior Coastal Engineer
Company: International Coastal Management
Final Review: Rodger Tomlinson
Company: Griffith Centre for Coastal Management
Approved for release: Bobbie Corbett
Title: Senior Coastal Engineer
Company: International Coastal Management
Version History
Version No. Date Changed by Nature of Amendment
draft 18.1.2010
Draft rev A 2.2.2010 Bobbie Corbett Option D3 amended
Draft rev B 19.2.2010 Bobbie Corbett Option E added
Draft rev C 23.2.2010 Bobbie Corbett Final design sketches & costings added
For preliminary discussion with agencies
Draft rev D 1.3.2010 Bobbie Corbett Section 6.4 [staging] added
Draft rev E 4.3.2010 Bobbie Corbett Amended in response to DERM comments
Draft rev F 27.5.2010 Bobbie Corbett Amended after Coastal Reference Group meeting
Revised rock costs
Draft rev G 4.8.10 Bobbie Corbett Amended after DERM & DEEDI meeting
Section 3.1 [do nothing option] & 8 [risk assessment]
added.
Draft rev H 23.9.10 Bobbie Corbett Amended after public consultation
Final design amended
Restructured
FINAL 8.11.2010 Bobbie Corbett Finalised for lodgement with applications
This document has been produced by International Coastal Management Pty Ltd (ICM) in accordance with the terms and
limitations of the brief by Sunshine Coast Regional Council. In preparing this report, ICM has used information provided by
the Client and others identified herein. ICM does not and shall not assume any responsibility or liability whatsoever to any
third party arising out of any use or reliance by any third party on the content of this document. This document is not to be
used without the express approval of Sunshine Coast Regional Council.
International Coastal Management ^ -, :. (ICM)
.,a 50' 3 Arm SYC Ma!i'la M'vi Beach Qill 42' 7 Australia
,w• P3 3cx 306 Main Beath ;=G Mari Kea:' Q'!c 4.1; Australia
ni . 61 7 5564 0564 •m -617 5532 914 7
wan wmv coastalmana emertcom au
Page 21
International
Coastal ^pner recd cot la
Management
TABLE OF CONTENTS
EXECUTIVE SUMMARY ...........................................................................................................................................................1
1. BACKGROUND ................................................................................................................................................................ 3
2. EXISTING SITUATION ..................................................................................................................................................... 5
3. OPTION ASSESSMENT ................................................................................................................................................... 9
3.1. Option A - Do Nothing 9
3.2. Option B - Establish Erosion Limit Control Lines 13
3.3. Option C1 - Wall and Embayed Beach 14
3.4. Option C2 - Groyne Field and Embayed Beach 17
3.5. Option D1 - Submerged Upstream Closure 20
3.6. Option D2 - Submerged Upstream & Downstream Closure 23
3.7. Option D3 - Training Wall with Submerged Upstream & Downstream Closure 26
3.8. Option E - Combination 29
4. RECOMMENDED OPTION ............................................................................................................................................. 33
4.1. Risk Assessment 33
4.1.1. Uncertainty 33
4.1.2. Variability in shoreline response 34
4.1.3. Channel Evolution/ River Processes 34
4.1.4. Impact on Shoals 34
4.1.5. Erosion of Mangroves 34
4.1.6. Flooding 35
4.1.7. Flushing 35
4.1.8. Swimmer safety near submerged closure 35
4.1.9. Navigation 35
4.1.10. Vandalism I Vessel impact with the structure 35
4.1.11. Structural aspects 35
5. CONSTRUCTION MATERIALS ...................................................................................................................................... 36
5.1. Sand-filled geotextile containers 36
5.2. Rock 36
5.3. Comparison 36
6. PRELIMINARY DESIGN & COSTING ............................................................................................................................37
6.1. Submerged "Closure" 37
6.2. Training Wall 38
6.3. Revetment Wall 41
6.4. Groynes 42
6.5. Total Strategy 43
6.6. Staged Works 44
International Coastal Management r . (ICM)
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Page 22
EXECUTIVE SUMMARY
With the exception of those areas already protected by rock works, Noosa River Spit is currently experiencing erosion along
its full length, including the southern end of the Noosa River Spit. Various options have been fully investigated using
numerical modeling, including:
A. Do Nothing.
B. Establish erosion limit control lines [present strategy].
C. Stabilise present channel location and beach:
C.1 Wall with embayed beach.
C.2 Groyne field.
D. Relocate main channel away from the beach:
D.1 Submerged upstream closure.
D.2 Submerged upstream & downstream closure.
D.3 Training Wall with submerged upstream & downstream closure.
E. Combination.
The preferred option includes [as per Figure El below]:
• Submerged curved 'closure' [sand-filled geotextile mega-containers) designed to create an enclosed, stable
beach and lagoon area
• Dredging and associated foreshore nourishment
• Training wall [sand-filled geotextile mega-containers] to provide a control point for the southern channel
• Wall [sand-filled geotextile mega containers] to prevent erosion along southern end of the Noosa River Spit
• Two groynes [2.5m3 sand-filled geotextile containers] to stabilize the upstream beach
Figure E1: Proposed Strategy
Page 23
Staged construction is recommended, with the first stage including the works shown in Figure E2 below. Stage 1 costs are
outlined in Table El below
V 0 . S
Submerged Closure
Crest at low Tide
Dredging
Training Wall
Crest at flood height
Wahl
Crest at surface level
[approx high tide)
Figure E2: Proposed Stage 1 Works
Table El: Summary of staqed costs
Qty Rate Amount
ex-GS
Establishment 1 S110,000
Northern section of curved "closure" 80m $250,000
Training wall 80m $305,000
Revetment wall $530,000
Dredging ! nourishment 10.000m3 $12 $120.000
Water quality testing Allowance only S30000
TOTAL $1,345,000
Page 24
1. BACKGROUND The Noosa River estuary is a highly modified system. In its natural configuration, the entrance is very dynamic and variable. During calm periods the river meandered substantially and flood events resulted in a straight channel direct to the ocean, placing the entrance close to the end of Hastings Street [Figure 1]. Figure 1: BPA aerial photos of natural Noosa River configurations - 1940 [calm weather] & 1972 [post-flood] In 1977, the BPA report "Scheme for the Protection of Hays Island and Restoration of Noosa Beach" stated that the southern channel had developed to such an extent that it carried almost the entire flow of the river. Severe erosion of Hays Island was then occurring along the northern revetment. In response to this problem, BPA proposed to relocate the river mouth to the north and reclaim Noosa Spit. "The function of this scheme is to separate the main body of flow of the Noosa River from Hays Island which is under threat of erosion and which requires protection. The scheme will also provide secondary benefits in the form of restoration and lengthening of Noosa Beach." The works were undertaken in 1978 [Figure 2]. Figure 2: BPA aerial photo of completed works [19831 Since reclamation of Noosa Spit, the behavior of the river has remained highly variable in response to changing conditions. The river meanders predominantly to the south [but periodically to the north] during calm conditions with a more direct "middle channel" developing during high flow conditions associated with cyclones and floods [Figure 31.
Page 25
f .:.JAL'. 7
Figure 3: EPA aerial photos of Noosa River configurations -1991 [calm weather] and 1992 [post Cyclone Betsy]
In 2006, Chamberlain & Tomlinson published a technical paper on Noosa River entrance channel dynamics based on a
review of historic aerial photographs. As part of the proposed works, this analysis was extended to the present date [for full
report, see Appendix A).
Noosa River Spit in the Noosa estuary has suffered erosion for many years. In 2003, dredging works within the river allowed
for nourishment along the Noosa River Spit foreshore and the establishment of sand bunds to artificially close the dominant
southern channel [Figure 41. These sand bunds were very effective in the short-term, reducing erosion and creating a calm
lagoon area. The channel velocities resulted in erosion and breaching of the bunds, requiring annual dredging works to
maintain these structures. The costs associated with regular dredging and the limitations placed on the dredging due to the
proximity of the Noosa River Fish Habitat Area made regular ongoing dredging undesirable. As a result, the last "top-up" of
the bunds was completed in 2005.
Figure 4: SCRC aerial showing sand pumping to keep channel off the Noosa River Spit [2003]
In 2006, erosion was once again a significant issue and a review of erosion management options for Noosa River Spit was
undertaken by International Coastal Management [ICM]. A number of options were considered, including:
A. Do Nothing.
B. Establish erosion limit control lines.
C. Stabilise present channel location and beach:
C1. Walls along severely eroding sections.
C2. Walls, groynes & low training walls.
D. Relocate main channel away from the Noosa River Spit:
D1. Ongoing dredging.
D2. Fluidiser.
Page 26
It was concluded that'
A -do nothing" approach was unlikely to be a viable long-term solution
The lowest-risk strategies involved stabilizing the present channel location
• If protection of the Noosa River Spit was important, extension of the rock wall along critical sections was
recommended
• If protection was considered less critical, relocation of the channel should be considered.
Advice from EPA recommended further investigation into Options B [establishing erosion control lines] & D [relocating the
channel]. Further investigation into relocating the channel was not feasible in 2006 due to the extent of the erosion along
critical areas of shoreline, the uncertainty relating to this strategy and the time it would take to implement. Noosa Shire
Council decided to proceed with Option B. As erosion along critical sections had already breached erosion control lines, a
rock wall was constructed. Further erosion adjacent to this area in subsequent years resulted in further breaching of the
erosion control lines and the rock wall was extended in 2008 [Figure 5].
Figure 5: Photo of rock wall constructed in 2008
2. EXISTING SITUATION
Over recent years, the Noosa River Spit has been the subject of serious ongoing erosion [Figure 6]. This has resulted in the
loss of public access paths [Figure 7], what was a popular protected public sandy beach area known as "dog beach" [Figure
8] as well as established vegetation [Figure 9].
Figure 6: Ongoing Erosion of Noosa River Spit [Aug 20091
Page 27
Figure 7: Photos showing damage to existing public access paths [Aug 20091 Figure 8: Photos showing loss of public beach [2006 and 2009] Figure 9: Photo showing loss of vegetation [Aug 2009]
Page 28
Overlay of the 2009 survey with the 2002 aerial photo [Figure 10] confirmed that there has been substantial erosion along the full length of the Noosa River Spit and also highlighted that there had also been substantial erosion of the end of the Noosa River Spit. To gauge erosion rates without the impact of the artificial sand bunds, the 2009 survey was overlaid with the 2006 aerial photo [Figure 111. Erosion is highest at the end of the Noosa River Spit [-15mlyr) and variable along the length of the Noosa River Spit [up to 10m/yr adjacent to the rock wall]. Figure 10: Overlay of Sept 2009 survey on 2002 aerial photo showing erosion over 7 years 45m eroS Figure 11: Overlay of Sept 2009 survey on August 2006 aerial photo showing erosion over 3 years
Page 29
Recent aerial photos [Fgure 121 and hydrographic survey [Figure 131 of the Noosa River estuary show that there is a
dominant middle channel with a secondary southern channel as a result of high flow conditions in 2007 108. This indicates
that present velocities and erosion rates may be slightly reduced.
" Flood-tidal
delta
Figure 12: Aerial photo of the Noosa River [Nov 20091
Figure 13: Survey of the Noosa River [Sept 2009)
Page 30
3. OPTION ASSESSMENT
The objective of the present study was to assess a range of options to allow for the design, approval and construction of
structures to alleviate the erosion of Noosa River Spit and re-establish a beach. While recreational aspects of this area are
key for the community, there were also concerns raised about continued erosion and the potential for breaching of the Noosa
River Spit into Noosa Sound and the increase in wave propagation into the Noosa River estuary [particularly at Munna Point].
The following options were considered:
A. Do Nothing.
B. Establish erosion limit control lines [present strategy].
C. Stabilise present channel location and beach:
C.1 Wall [with embayed beach].
C.2 Groyne field [with embayed beach].
D. Relocate main channel away from the beach:
D.1 Submerged upstream closure.
D.2 Submerged upstream & downstream closure.
D.3 Training Wall & submerged upstream & downstream closure.
E. Combination.
Further consideration was not given to ongoing dredging due to the undesirability of the works in such close proximity to the
Noosa River Fish Habitat Area nor the use of a fluidizer since the technology is not well proven and the Noosa River estuary
is so highly dynamic, although further consideration could be given to this option in future if necessary.
Options were assessed in two ways - hydrodynamic modelling for short-term assessment and conceptual analysis for
longer-term assessment.
Hydrodynamic modeling was undertaken using a partially calibrated MIKE21HD model developed for this project by Griffith
Centre for Coastal Management & DHI Australia. Full details of modeling and data collection are presented in Appendix B.
For the purposes of this report, results relating to maximum spring tidal velocities associated with ebb and flood tides are
presented as well as differential plots [showing the change in velocity between the existing situation and the option being
considered]. This modeling provides an assessment of the immediate impacts of the proposed works - a "snapshot" of the
river response.
Sediment transport modeling was considered, however this type of modelling would be expensive [of the order of $200,000]
and time-consuming [>12 months]. Given the variability of the river, it is likely that by the time modelling was undertaken [let
alone the works constructed], the river configuration could have changed and the evolution could be very different. Given
that the model would be essentially uncalibrated, the results would be scenario-based and the Noosa River estuary is
naturally variable, it is highly unlikely that this type of modeling would provide an accurate representation of the actual
evolution of the river over time. It would also be of limited benefit in providing a realistic worst-case scenario for impact
assessment or design purposes. As such, sediment transport modelling has not been undertaken.
Long-term evolution of the river in response to the proposed works has been undertaken using conceptual analysis. This is
based on the aerial photo analysis undertaken by Chamberlain & Tomlinson that was extended by Griffith Centre for Coastal
Management as part of these works [Appendix A].
While the approach taken is best practice, it is noted that the coastal environment is inherently complex and variable
[increasingly so with climate change] and there are limitations and uncertainties inherent in these techniques. As a result, it
is recommended that the proposed works be staged where possible and the design be robust and flexible. A comprehensive
monitoring strategy [Appendix C] should also be implemented to allow for ongoing assessment of the performance and
impacts works. It is also preferable that the works be able to be modified or removed if monitoring shows that this is
necessary.
3.1. Option A - Do Nothing
Meandering of riverbanks and associated erosion and accretion is a natural event [despite the fact that the Noosa River Spit
was artificially reclaimed and is not a natural feature in the river]. The BPA report noted that Noosa River Spit would be
"subject to erosion and accretion as part of the normal beach system", although they also noted that it would "require
maintenance ... [although] the timing and extent of maintenance cannot be estimated ... because of the unpredictable nature
of the sed'.
Page 31
Numerical modeling [Figure 14] of the existing situation shows that tidal velocities in the southern channel adjacent to the
Noosa River Spit typically peak at 0.5 - 0.6m/s on both the flood and ebb tides. The velocities directly adjacent to the shore
range depending on the location and the state of the tide. The areas directly adjacent to the existing rock wall experience
low (<0.25m/s) velocities on the flood tide, but experience velocities up to 0.6m/s during the ebb tide. Further upstream the
Noosa River Spit experiences higher velocities (0.5 -1 m/s) on the flood tide and much lower (0.25m/s) velocities on the ebb
tide. The end of the Noosa River Spit is again very sheltered during the flood tide, but experiences high velocities (0.5 -
1m1s) during the ebb tide.
Cu;u it* ayeed Im/sl
080.100
070.080
060.070
050.060
040.050
035.040
330.035
025-030
020-025
015.020
010.015
005-010
000.005
r4Wow 0 00
Ur defined Value
080 1 00
070.080
060.070
050.060
040.050
035.040
030.035
325.030
320.025
010-020
010.015
Figure 14: Results of MIKE21HD model [ebb & flood tide] for Existing situation
It is likely that these velocities are lower than experienced previously given dominance of the middle channel and the partial
closure of the southern channel at the end of the Noosa River Spit, but that erosion is still occurring at a reduced rate. It is
noted that areas of greatest erosion are typically vulnerable during the ebb tide, although upstream areas of the Noosa River
Spit are vulnerable during the flood tides [Figure 15].
Page 32
Figure 15: Critical times for erosion
In the medium-term, it is likely that periods of calm weather will result in increased meandering of the river and the southern
channel will once again become the dominant channel. This will result in increases in the velocities adjacent to the foreshore
and a corresponding increase in erosion rates, potentially greater than the average rates between 2006 and 2009. While it is
possible that meandering will result in a northern channel alignment, the extensive flood delta [Figure 12] and the
predominance of the southern channel in the past [Appendix A] indicates that a southerly alignment is much more likely. In
the event that a northerly channel develops or a major event results in a reinforcement of the middle channel, the
development of the southern channel may be delayed. As such, it is likely that erosion in this location will continue, although
given the extent is difficult to predict.
From the high rates of erosion [averaging 10m/yr, but potentially higher] and the narrow width of the Noosa River Spit [70m,
some of which is low-lying], it is clear that in the Noosa River Spit could potentially breach in the medium-term. On average
rates, this would be expected to be within 5-10yrs, however the high variability of the system and the potential impact of
major events could have a substantial impact on this timeframe. Breaching would introduce the potential for redevelopment
of a Noosa Sound channel which would have significant ramifications on estuary dynamics [Figure 16]. Long-term widening
of the breach could result in eventual loss of the Noosa Spit. In the long-term, if no protection works are undertaken,
narrowing and breaching of the Spit along the beachfront is also conceivable [Figure 17]. The impacts of breaching of the
Noosa River Spit are potentially substantial. It is noted that reinstatement of the Noosa River Spit would be a substantial
undertaking, particularly if it involves closure of a dominant channel.
Erosion at the end of the Spit is also likely to continue and this would result in increased wave penetration into the estuary,
particularly to Munna Point [Figure 18]. This could potentially have an impact on erosion in this area. Management of this
location may need to be considered if erosion at the end of the Noosa River Spit is allowed to continue.
-A& A
Figure 16: Potential channel alignment in the event of breaching of Noosa River Spit
Page 33
Figure 17: Potential channel alignment in the event of breaching of Noosa Spit to the ocean
P0.1 7"
Figure 18: Potential wave penetration into the estuary
The potential impacts of the "do nothing" option include:
• Eroded beach
• Reduced opportunities for beach recreation and safe swimming
• Safety issues [unstable banks in such a popular area]
• Loss of Council pathways and established vegetation
• Adverse public perception
• Increased wave penetration into the estuary, particularly at Munna Point [increased erosion]
• Breach of the Noosa River Spit through to Noosa Sound
• Potential for substantial changes to the entrance dynamics
• Possible wave penetration into Noosa Sound
• Undermining of Noosa Sound retaining walls
• Loss of Noosa Sound as an anchorage
• Possible detrimental impact on navigation within the entrance
• Complete loss of Noosa River Spit [including mangrove communities]
• Breaching of the Noosa Spit to beach
• Loss of Council road, paths. infrastructure, facilities etc
• Isolation and possible undermining of Noosa River entrance training wall
• Complete loss of Noosa Spit and beach from training wall back to Hastings St
• Possible impact on Noosa Main Beach
• Possible detrimental impacts on Fish Habitat Area
Given the significant impacts associated with the "do nothing" option, it is not considered to be desirable and is not
recommended as a long-term strategy.
Page 34
3.2. Option B - Establish Erosion Limit Control Lines
The present strategy of establishing erosion limit control lines has been partially implemented by Council and in areas where
these limits were deemed to have been breached, rock walls have been constructed to prevent further erosion beyond these
limits. Given the extent of recent erosion, it may be that erosion control lines have been breached in other locations,
triggering construction of additional rock walls under the present strategy.
Option B involves hardening of the bank and as such does not have an appreciable effect on flows. No additional numerical
modeling was completed for this option.
In the medium-term, it would be expected that the dominant channel will return to an alignment along the southern bank and
the erosion rate will increase. This will result in additional areas for which control lines are breached. It is conceivable that
over time the entire length of Noosa River Spit could be protected with rock walls and no beach would be available.
The potential impacts of Option B [establishing erosion limit control lines] include:
• Before control lines are breached - foreshore eroded with scarps and scattered with dead trees
• Reduced opportunities for beach recreation and safe swimming
• Safety issues [unstable banks in such a popular area]
• Loss of Council pathways and established vegetation
• Adverse public perception
• After control lines are breached - rock wall and deepening of seabed adjacent
• No further erosion
• Complete loss of beach
• Complete loss of recreational amenity
• Adverse public perception
Given the desirability to retain some recreational amenity in this area, it is not considered to be desirable to continue
pursuing this strategy. It is noted, however, that there are some areas where provision of a beach is not suitable or desirable
[e.g. at the end of the Noosa River Spit] and provision of a wall as a means of erosion protection will likely remain the most
appropriate solution in these locations.
Consideration was given to nourishing on the southern side of the Noosa River Spit adjacent to the location most vulnerable
to breaching [Figure 19] in an attempt to increase the time before erosion control lines are breached. Unfortunately, a large
section of Noosa River Spit is low-lying [submerged on higher tides] and will be more easily eroded. As the whole length
cannot be easily widened or raised due to the presence of mangroves, this would merely shift the most vulnerable location
and would not provide a recreational beach or reduce the erosion at the end of the Noosa River Spit.
Nourishment to move erosion control lines
Figure 19: Option to widen vulnerable area of Noosa River Spit
Page 35
3.3. Option C1 - Wall and Embayed Beach
Option C1 involves the construction of an erosion protection wall along the length of the Noosa River Spit with the formation
of a short embayed beach to provide recreational amenity. For the purposes of the model, the groynes were fully emergent
and extended out to the centre of the existing channel. See Figure 20.
M
Figure 20: Sketch of works forming Option C1
Given the full protection of the majority of the shoreline with hard erosion protection measures, the key area of concern in
this case is the proposed beach area between the two groynes. Numerical modeling [Figure 21 and Figure 22] showed
similarly low velocities would be experienced in this area on the flood tide. however on the ebb tide [most critical for erosion]
it showed only a small region (-30m in length) adjacent to both groynes where velocities were lowered. The remainder of
the beach between the two groynes was subject to higher than existing velocities [up to 0.8 - lm/s]. This is a significant
increase [by up to 0.5m/s].
In the main channel, velocities were generally the same on the flood and ebb tides, although the areas of high velocity
adjacent to the northern and southern shoals were increased in size. Velocities adjacent to the shore at the end of the
Noosa River Spit were decreased on the flood tide and increased on the ebb tide [although this location would be protected
by rock wall as part of this option].
In the medium term it is likely that the southern channel will once more become dominant. This will result in a deepening of
seabed levels adjacent to the ends of the groynes and an increase in velocities in the southern channel. Velocities adjacent
to the structure and within the embayment will change in response to the change in the channel configuration. While it is
possible that widening of the channel may result in a reduction to the velocity spike shown by the modelling, it could easily
result in further increases in velocity.
The potential impacts of Option C1 [wall & embayed beach] include:
• Within embayment
• Increased erosion
• Increased potential for breaching of Noosa River Spit in an already vulnerable location
• Where walls are located [majority of foreshore]
• No further erosion
• Complete loss of beach
• Complete loss of recreational amenity
• Adverse public perception
While it may be possible that groynes could effectively be used to protect the area directly adjacent to the rock wall. the
proposed layout does not appear to be effective and it is clear that the creation of a stable beach in this location would
require either many more groynes at much closer spacings [which is less desirable for recreational beach amenity] and/or
much longer groynes [which would result in channel closure without substantial dredging to relocate the existing channel].
Page 36
_ u^rent -reed [m!6[
:.,e I Co
-150
- 100
-080
l -070
C-060
40-050
- 3'-040
3{,.035
- -030
-025
-020
to-015
0 10
G-005
F Ii, 000
1-1 ,defined Value
1
-,need [m/s)
ye 150
-150
-100
0-080
C .070
5C-060
_ 1C 050
-`-040
3^-035
2s-030
- -025
.̀ -020
.015
-010
-005
v 000
I - Urdefined Val
Figure 21: Results of MIKE21 HD model [ebb & flood tide] for Option C1 [Wall & Embayed Beach]
[OCR of page images]
Current speed [m/s
+016
5-010
0.05
HB Below 000
Undefined Value
*
Current speed [m/s]
Below
Undefined Vaive
Figure 21: Results of MIKE21HD model [ebb & flood tide] for Option C1 [Wall & Embayed Beach]
Page 37
u•r...r ^Feee lnvs}
tie 05
' 05
03
t . 01
-. .' --0
(♦ -033
-05
I UjehneA .ti -
Figure 22: Differential velocities [ebb & flood tide] for Option C1 [Wall & Embayed Beach] compared to existing
Page 38
3.4. Option C2 - Groyne Field and Embayed Beach
Option C2 involves the construction of a series of groynes along Noosa River Spit, one of which acts as a training wall to the
flow of the river. A terminal seawall also forms part of this option, although the intent is for this structure to be buried. See
Figure 23.
Figure 23: Sketch of works forming Option C2
Numerical modeling [Figure 24 and Figure 25] clearly showed that the groyne field would be very effective along the
upstream sections of the Noosa River Spit, lowering velocities to <0.25m/s during both the ebb and flood tides. Despite the
intrusion into the channel, adjacent velocities were only slightly increased, indicating that the dredging was adequate to offset
the potential impact on the channel. As per Option C1, however, the region between the two most downstream groynes
remained subject to increased velocities during ebb tides [see section 3.3].
In the main channel, velocities were generally the same on the flood tide, although the areas of high velocity adjacent to the
northern shoals were increased in size in some locations and decreased in others. On the ebb tide, areas of high velocity
adjacent to the southern and northern shoals were increased in size. Velocities adjacent to the shore at the end of the
Noosa River Spit were lower on both the flood and ebb tides.
In the medium term, it is likely that the southern channel will once more become dominant. This will result in a deepening of
seabed levels adjacent to the ends of the groynes and an increase in velocities in the southern channel. While it would be
expected that the groynes would continue to provide protection, the shoreline alignment will vary in response to these
changes to the river system.
The potential impacts of Option C2 [groyne field & embayed beach] include:
• Within embayment
• Increased erosion
• Increased potential for breaching of Noosa River Spit in an already vulnerable location
• Within upstream groyne field
• Generally stable foreshore, although erosion may still occur
• Improved recreational amenity
Results suggest that a series of groynes could effectively stabilize the foreshore along the upstream areas of the Noosa
River Spit as well as allowing for the creation of a usable beach. The provision of an embayed beach remains problematic
[see Option Cl].
Page 39
rt-, ,teed Im/si
e 150
-150
C-100
-C-080
6" 070
D50-060
D40-050
035-040
D30-035
0' -030
'G-025
015-020
10.015
305.010
300-0U5
B-InN 000
l!rdetmed Value
in r-r» speed [m/s)
150
:, - 1 50
C-100
70.080
C-070
060
4C-050
3335-040
330-035
3:5.030
2C-025
1`-020
i C-015
-010
-005
F--I-LH 0 00
IirJetmed Vatui
Figure 24: Results of MIKE21HD model [ebb & flood tide] for Option C2 [Groyne Field]
[OCR of page images]
1
Current speed [m/s]
Above 1.50
Undefined Value
7
Current speed [m/s]
Page 40
urrent speed [Vs)
- :-:e 05
3. 05
1 - 03
01
--01
.-03
-05
J-fined Val
wrerd sp eJ [11Yb]
=x:e 05
05
t u3
01
-01
-03
- Below -0 5
Undefined Value
Figure 25: Differential velocities [ebb & flood tide] for Option C2 [Groyne Field] compared to existing
Page 41
3.5. Option D1 - Submerged Upstream Closure Option D1 includes a submerged closure of the southern channel at the upstream end only [Figure 26]. While previous campaigns have focused on the formation of these closures using loose sand, the rapid erosion and the environmental impacts of ongoing dredging make this undesirable and a structural closure is being considered in this case, which also allows an equivalent height to be achieved with a substantially smaller footprint. The submerged closure is set at a height of -0.6m AHD [approximately low tide] such that the structure will be fully submerged the majority of the time and partially emergent only on the lowest of tides. Figure 26: Sketch of works forming Option D1 Numerical modeling [Figure 27 and Figure 28] showed that on the ebb tide, the upstream closure resulted in little change to velocities in general. Although some areas (including some high 'spots' of velocity) were significantly reduced, these were generally not in the 'problem' areas. The velocities on the flood tide were very similar to the existing situation with high velocities adjacent to the shore persisting [if not increased] in upstream areas. It may be that the potential impact of the upstream submerged closure is being masked by the fact that the southern channel is currently partially closed in this location, such that the change to the seabed in this location is not as pronounced as it may have been in the past. In the main channel, velocities were generally the same on the flood and ebb tides, although the areas of high velocity adjacent to the shoals were increased in size on both the ebb and flood tides. Velocities adjacent to the shore at the end of the Noosa River Spit were increased on the vulnerable ebb tide. Velocities over the closure peaked at >lm/s on the flood tide and 0.75m/s on the ebb tide. The area of increased velocity is limited to the footprint of the structure itself. In the medium term, while it is possible that the closure will reinforce the middle channel, it is likely that the channel will attempt to migrate to the south as it has in the past. This would result in the channel closure becoming a submerged groyne type feature. Since velocities have not been substantially reduced by the structure as a closure, it is unlikely that it would perform substantially better as a submerged groyne and it is likely that erosion issues will not be fully resolved, although they may be mitigated if the structure performs better under increased flows associated with a dominant southern channel. The structure could be extended [either initially or as required after breaching] to reinstate the closure. It appears that provision of a single submerged upstream closure would be of limited benefit in the short term and unknown benefit in the medium term. It seems likely that either a secondary closure would need to be introduced downstream [as done previously using artificial sand bunds, see Option D2] or the height of the structure will need to be raised in order to have a greater impact on velocities and erosion.
Page 42
-150
:-150
- 1 00
-080
• 0 70
50.060
10 050
035.040
030.035
025.030
0_20-025
-020
-015
-010
-005
+000
Iehned Value
1
^I 'red IM/61
--i 150
)♦ 150
1 00
'0-080
FJ 0 70
050-060
040-050
035-040
030-035
025-030
020-0.25
0.15.020
010.015
`••010
-005
.-lc 000
Jelrled Valve
Figure 27: Results of MIKE21 HD model [ebb & flood tide] for Option D1 [upstream closure]
[OCR of page images]
‘i
Current speed [m/s]
Undefined Valve
Current speed [m/s]
ve 1.50
0-150
0 - 1.00
080
Page 43
urrer deed (rnKJ
=xve 05
05
^t• 03
01
-0 1
-03
-05
fined Value
Cunrnt opted Invs]
=;cve 0 5
05
1 03
l•01
= -0 1
-0 3
F-10.y -0 5
Indehned Value
Figure 28: Differential velocities [ebb & flood tide] for Option D1 [upstream closure] compared to existing
Page 44
3.6. Option D2 - Submerged Upstream & Downstream Closure
Option D2 includes the submerged closure of the southern channel at both the upstream and downstream ends (Figure 29],
similar to the previous closures achieved using sand bunds. The same crest height as for Option D1 was used [RL -0.6m
AHD or approximately low tide].
Figure 29: Sketch of works forming Option D2
Numerical modeling [Figure 30 and Figure 31] showed a reduction in ebb tidal velocities for the full length and width of the
southern channel. Adjacent to the shore, velocities were typically <0.25m/s, although they were as high as 0.4m/s in places.
On the flood tide, the structures impacted very little on velocities in the southern channel, although areas of high velocities
adjacent to shore at the upstream sections of the Noosa River Spit were generally reduced [although some areas of higher
velocity remained].
In the main channel, velocities were hardly affected on the flood tide. On the ebb tide, velocities were very similar for the
bulk of the channel, but were slightly increased (by 0.1 - 0.3m/s) where the channel is narrowest between the shoals. Areas
of high velocity adjacent to the southern shoals were substantially increased in places. Similarly, there were increased
velocities adjacent to the shore at the end of the Noosa River Spit [although this location would be protected by rock wall as
part of this option].
Velocities over the upstream closure peaked at >1 m/s on the flood tide and 0.5m/s on the ebb tide. The downstream closure
experienced velocities >1 m/son the ebb tide and slightly lower (0.8 -1 m/s) velocities on the flood tide. These areas of
increased velocity were limited to the footprint of the structure itself.
In the medium term, while it is possible that a submerged closure of the existing southern channel could reinforce the middle
channel such that it remained the dominant channel, the response of the system is difficult to predict and it is possible [if not
likely] that at some point in the future the channel will attempt to migrate to the south as it has in the past. This would result
in the channel breaching the sandbar that presently exists between the two closures. It is difficult to assess whether this
would result in velocities that would reintroduce an erosion threat along the shoreline of the Noosa River Spit. This risk could
be addressed by linking the two closures, either during initial construction or in the event that erosion once more became a
threat. With migration of the channel to the south effectively prevented, it is possible that there will be an increased
likelihood of the northern channel becoming dominant [as it has done on occasion in the past] in the event that the middle
channel does not remain dominant.
The potential impacts of Option D2 include:
• Reduced erosion adjacent to the existing rock wall
• Potentially continued erosion along upstream sections of the Noosa River Spit
• Larger impact on river processes
• Increased potential for meandering to the north [potential impact on Fish Habitat Area]
Page 45
Compared to Option D1 [see section 0], it is clear that the addition of the downstream closure resulted in a much greater
impact during the ebb tide.
Closure of the southern channel has been undertaken in the past and has proven effective at creating a sheltered lagoon
area with a stable beach foreshore that is suitable for recreational usage. Numerical modeling has confirmed that narrower
structures with lower crest levels can also be effective at reducing flow velocities along the Noosa River Spit foreshore. The
inclusion of a downstream submerged closure is a significant component in ensuring that this option is effective. This option
is particularly effective along the vulnerable sections adjacent to the existing rock wall, but tends to be less effective in
upstream areas on the flood tide.
1
urent cl eed Jm/sJ
4"'e 1 50
',0-150
3 0-100
-Q-080
i___ 070
- 850-060
II. 040-050
-835.040
: 30 - 0 35
® -030
025
litititi 5.0 20
1ir -015
II• -010
VJ-UU5
JJJJJJ^ _ -in.s 0 00
_' i J-tied value
urr rt<,ledlm!si
=1.:,:c 1 50
1 50
C-100
C-080
I-# : . C - 0 70
lu06U
(♦ a,' -0"0
II• :5-040
(♦ C-035
II• - -030
-025
II• -020
-015
-010
li• -005
JJJJJJJn 6 m 0 00
Figure 30: Results of MIKE21HD model [ebb & flood tide] for Option D2 [upstream & downstream closure]
Page 46
e 05
?- 05
1 03
1.01
--01
-0 3
F-ia,v -0 5
ielmed Value
Figure 31: Differential velocities [ebb & flood tide] for option D2 [upstream & downstream closure] compared to
existing
Page 47
3.7. Option D3 - Training Wall with Submerged Upstream & Downstream Closure
In Option D3 [Figure 32], a section of the upstream closure was raised to provide a fully emergent training wall and the
downstream closure was relocated to the end of the existing rock wall to reduce the potential impact on the estuary.
Dredging was also included to source material for construction and for nourishment of the beach.
Figure 32: Sketch of works forming Option D3
Numerical modeling [Figure 33 and Figure 34] showed a reduction in ebb tidal velocities in the southern channel similar to
Option D2 [see section 0], both between the closures and further downstream along the existing rock wall. On the flood tide,
the velocities were typically similar near the existing rock wall, but further upstream the partial training wall significantly
reduced velocities adjacent to the shore, although the modeling still showed some locations further from the groyne which
were subject to velocities reaching 0.8m/s.
In the main channel, velocities were generally the same on the flood tide, although the areas of high velocity adjacent to the
northern shoals were increased in size and the velocities adjacent to the upstream closure were slightly increased. On the
ebb tide, velocities were very similar for the bulk of the channel, but were slightly increased (by 0.1 - 0.3m/s in places) where
the channel is narrowest between the shoals. Areas of high velocity adjacent to the southern and northern shoals were
increased in size. Velocities were increased slightly [by 0.1 - 0.3m/s] in the secondary channel between the shoals adjacent
to the downstream closure. Velocities adjacent to the shore at the end of the Noosa River Spit were also increased
[although this location would be protected by rock wall as part of this option].
Velocities over the upstream closure peaked at >lm/s on the flood tide at the end of the training wall, but are close to
existing velocities (-0.5m/s) on the ebb tide. The downstream closure experienced velocities >lmis on the ebb tide and
-0.5m/s on the flood tide. These areas of increased velocity were typically limited to the footprint of the structure itself.
In the medium term, while it is possible the southern closure may help to slightly reinforce a dominant middle channel, it is
likely that the channel will migrate to the south as it has in the past. This could result in the channel breaching the sandbar
that presently exists between the two closures, resulting in the submerged closures becoming submerged groynes. This
could potentially result in velocities that would reintroduce an erosion threat along the shoreline of the Noosa River Spit. This
risk could be addressed by linking the two closures, either during initial construction or in the event that erosion once more
became a threat. This configuration may have some impact on the river processes, but it will be substantially less than the
D2 option and it is unlikely that it will substantially affect the tendency of the river to meander to the north.
The potential impacts of Option D3 include:
• Reduced erosion adjacent to the existing rock wall
• Generally reduced erosion along upstream sections of the Noosa River Spit [although some erosion may
persist in some locations]
Page 48
The movement of the downstream closure substantially reduces the effective footprint of the works and its impact of the
works on the river processes without reducing the benefits provided to critical areas. The raising of the shoreward end of the
upstream closure to form a partial training wall also provided noticeable benefit to the upstream areas.
(♦ .r150
(♦ - -150
-100
-090
-070
(♦ `.0 -060
40 -0SO
yt -040
IC-035
tl♦ ' •030
tl♦ • 0 25
tl♦ - 0 20
t^ .015
II• -010
t^ -005
i ,H.v000
I I.fined Valun
urreit s{.eed Im++l
(♦ .*1 50
:-150
-080
•070
.060
-050
M -040
•035
® -030
t^ -025
020
Ittln - 0 15
tl♦ 0 10
f♦ 0 05
tl• , 000
Figure 33: Results of MIKE21HD model [ebb & flood tide] for Option D3 [training wall with upstream & downstream
closure]
Page 49
AufI -nt Steed Im'51
:.e 0 5
• 05
t - 03
t - 01
--01
-03
ti -05
•: fined Val
r Current speed tnvs )
e 05
05
t • 03
01
3-01
-0 3
CD
'Jn 7hn_-J .JI^C
Figure 34: Differential velocities [ebb & flood tide[ for Option D3 [training wall with upstream & downstream closure]
compared to existing
Page 50
3.8. Option E - Combination
Upon review of modeling results for Options B, C & D, it was recognized that all the proposed strategies presented potential
benefits and drawbacks and it was decided to investigate a layout that combined aspects of all of these options [Figure 35].
Option E was developed to incorporate the benefits of all three considered strategies to provide a solution that provided the
greatest benefit with the least impact on the river. As such, Option E includes the following components:
• End of Noosa River Spit - Recreational benefits and creation of a beach is not desirable. Allowing further erosion
is not desirable as this could have impacts on Munna Point. As such, the erosion limit control line has likely been
reached and an erosion protection wall was included along this section.
• Upstream section - Modeling [section 0] showed that emergent training walls and groynes were very effective in
reducing velocities in this location and providing a control point for the flood tide. Construction of training walls and
groynes has been included.
• Central section - This section is very vulnerable and a key location for recreational amenity. Modeling [section 0]
showed that the provision of upstream and downstream submerged closures provided substantial benefits in this
location [the creation of a calm lagoon area and stable beach]. As there was potential for future river changes to
breach the shoal between the upstream and the downstream closures, it was considered desirable to address this
problem during the initial works rather than extend the structure as required at some point in the future. The
potential impact on the river was also minimized with the inclusion of a single, curved closure that allowed a more
natural channel alignment when the southern channel was dominant. Dredging for construction and use of
material as nourishment was also included.
• Downstream section - this area is presently protected by the existing rock wall. To minimize the impact on the
river and retain the rock habitat, this has been left in its present state [although it is noted that maintenance of the
structure may be required if/when the channel deepens along this section].
Numerical modeling [Figure 36 and Figure 37] showed that the curved "closure' successfully created an enclosed lagoon
with lower velocities (typically <0.25m/s) on both ebb and flood tides. The upstream regions of the Noosa River Spit
experienced lowered velocities [<0.25m/s on both the ebb and flood tides] with slightly elevated velocities along a short
section between the closure and the first short groyne. Modeling did not show any inclination for the formation of vortices
adjacent to the training wall, although this may be due to the resolution of the model and the inclusion of nourishment.
Velocities adjacent to the existing rock wall were typically unchanged on the flood tide and lowered on the ebb tide.
In the main channel, velocities were generally the same on the flood tide. although there was minor increases to the size of
high velocity areas adjacent to the northern shoals and the velocities adjacent to the upstream closure were increased (0.1 -
0.5m/s) where the southern channel merged with the middle channel. On the ebb tide, velocities were very similar for the
bulk of the channel, but were slightly increased (by 0.1 - 0.3m/s in places) where the channel is narrowest between the
shoals. Areas of high velocity adjacent to the southern and northern shoals were increased in size. Velocities adjacent to
the shore at the end of the Noosa River Spit decreased on the problematic ebb tide.
Page 51
Velocities at the end of the training wall were up to lm/s on the flood tide at the end of the training wall, but are close to
existing velocities (-0.5m/s) on the ebb tide. The curved "closure" typically experiences relatively low velocities (<0.25 -
0.4m/s) on both the ebb and flood tides along its full length, although does show elevated velocities (up to lm/s) at the
downstream end on spring ebb tides.
r-fl• wee, i
t..eI
t^ 15o
100
060
').070
G-0.080
tttt^ . o - 0 so
,s-040
u•035
ttl♦ 030
0 25
020
-015
0 10
x•005
..000
w fined VoIu1
"ed (nvsJ
e 1 SG
:.15C
-tOC
OK
0%C
- J - 0 6C
4'-05C
5.040
30.035
_5.030
(tl♦ :0.025
15-020
ttl♦ - 0 15
- .•S 010
00:
E•a,,.000
1rhn.d Val
Figure 36: Results of MIKE21HD model [ebb & flood tide] for Option E [combination]
Page 52
unvnr speed (M/51
'1-e05
S^3- 05
03
01
--0 1
--03
-:aw-0 5
1, fend Value
urrent speed (m/si
- :.t,-,,e 05
^ 05
03
-01
--01
• o _ 6elrnv -0ed
5
1•
Undelned Value
Figure 37: Differential velocities [ebb & flood tide] for Option E [combination] compared to existing
Page 53
In the medium term, it could be expected that the river will meander to the south as it has in the past. The training wall and
submerged "closure" become control points for the flow and the channel alignment would be expected to develop similarly to
Figure 38. This is a very natural alignment for the river and should not impact unduly on the long term evolution of the river
or the inclination of the river to meander to either the north or the south. It would be expected to result in increased velocities
and greater depths adjacent to the end of the training wall and along the river side of the curved "closure", but it is expected
that while the performance of the structure may vary slightly, it should continue to mitigate erosion levels, preventing
breaching of the Spit and providing improved amenity. Given the fact that the structures are essentially within the 2002
channel alignment, the potential impact of the works on the river system would be expected to be similar to that experienced
in 2002.
61
Ads= -_^i^3E F! j ^. : . p•
A& lo- ,; A
Figure 38: Likely future channel alignment for Option E, similar to 2002 alignment
The potential impacts of Option D3 include:
• Reduced erosion along the length of the Noosa River Spit
• Threat of breaching eliminated
• No further erosion at end of Noosa River Spit
• Possible end effects may result in increases to erosion of mangrove area at end of the Noosa River Spit
[presently experiencing high levels of natural erosion]
• Erosion further upstream not anticipated
• Naturally active sand shoals may be affected
• Potential impact on river evolution similar to 2002 conditions
This option should be effective at stabilizing the full length of the Noosa River Spit and creating a calm lagoon area and
recreational beach while also minimizing the impact of the works on the river dynamics.
Page 54
4. RECOMMENDED OPTION
As was concluded in the previous 2006 report and supported by EPA, the "do nothing" option is still not preferred long-term
strategy, primarily due to the scope of the impacts associated with breaching of the Noosa River Spit. The modelling and
conceptual analysis of likely long-term behavior indicates that Option E [Figure 35] is the most effective. It achieves both the
primary goal of alleviating erosion along the Noosa River Spit [and eliminating the potential for breaching] as well as creating
conditions in which a protected recreational beach and lagoon area will remain stable. It limits the extent that the southern
channel can migrate southward while minimizing the potential impact of the works on natural estuary processes.
A discussion with local stakeholders was undertaken and concerns were raised by VMR about the closure of the southern
channel despite the dominance of the middle channel. As a result, it appears that dredging of the secondary southern
channel will be necessary to provide adequate navigation. As such, the strategy has been amended to include these works
[Figure 39]. Material from works is to be used as beach nourishment.
Submersed Closure ► . _:S
Dredging
Nourishment "f tr^.it^L1 .^'' '
Groynes
Training Wall
it
Figure 39: Recommended Strategy
4.1. Risk Assessment
All the options investigated [including the "do nothing" option] have associated impacts and risks. These risks can be
accepted, mitigated or managed. The recommended option has been assessed and the risks are outlined below.
4.1.1. Uncertainty
The Noosa River is highly variable with the added complexity of predicted climate change. There are inherent limitations
associated with all assessment techniques and while it provides a valuable insight into the effectiveness of the proposed
works, a level of uncertainty remains. As such, a comprehensive monitoring strategy [Appendix C] is to be implemented to
allow for ongoing assessment of the performance and impacts works. The monitoring strategy may recommend
modifications to the works to improve performance.
Page 55
4.1.2. Variability in shoreline response
Given the variability of the river, it is anticipated that the performance of the structures will also vary to a certain extent.
Initially, the structures will behave as two river closures, but after the river evolves and the dominant channel moves to the
south, velocities will increase and the downstream 'closure' will become a training wall and the upstream 'closure" will
become a channel guide separating the lagoon, as intended. The location and dominance of the adjacent channel will
impact on the final stable beach alignment and the length of foreshore protected by the groyne. The beaches will continue to
be subject to some level of erosion and scarps may still form along the foreshore, although the incidence and severity should
be significantly reduced and the threat of the Spit breaching should be effectively eliminated. Evaluating the performance of
the structures will form an essential component of the monitoring program and help determine if construction of the shorter
groynes or modification of any of the structures is necessary.
4.1.3. Channel Evolution 1 River Processes
Numerical modelling of short-term impacts indicates that there is no significant pressure for the river to meander to the north
(any more so than it has in the past) in the short term. In the long term, the fact that the footprint is essentially within the
2002 shoreline [Figure 38] indicates that the structures should influence the river configuration in a similar way to the natural
shoreline in 2002. It should be no more likely to create a dominant northern channel than it has in the past. It is noted,
however, that the river has meandered to the north in the past and it is entirely possible (if not likely) that it will do so at some
point in the future. A northerly dominant channel should not be interpreted as an "impact" of the works without significant
investigation.
4.1.4. Impact on Shoals
The works are anticipated to result in erosion of sand banks in some locations [middle channel and secondary southern
channel] in the short term. This increased erosion pressure will reduce as the channel changes in response to the works.
The works will also have some impact on the evolution of these shoals as the river develops. These shoals are already
highly mobile, however, and their evolution is unpredictable in any case. Given that the works are essentially within the 2002
shoreline footprint, long-term influence on evolution should be similar to that experienced in 2002.
4.1.5. Erosion of Mangroves
The proposed revetment wall at the end of the Noosa River Spit will prevent significant further erosion along its extent. At this
stage, it is not proposed to extend the revetment wall such that it would provide protection to the adjacent mangrove stands
[although this could be considered if necessary] and these will remain vulnerable to natural erosion processes. While
erosion rates will vary in response to natural conditions, the high level of erosion experienced in recent years (averaging
15mtyr) suggests that erosion at the end of the Spit may continue as part of natural processes [Figure 40]. A high level of
erosion of the mangrove populations has been a natural feature in this location and loss of mangroves should not
automatically be considered to be a result of the construction works without further investigation. Numerical modelling
indicates that the works will not exacerbate the velocities in this area during the more critical ebb tide, so there should be
minimal impact as an immediate consequence of the works. As erosion occurs, a step in the shoreline will develop [Figure
40] and while the dominant transport direction is such that any groyne effect should be beneficial, end effects and eddies
associated with the wall return may result in locally increased erosion at the end of the revetment wall. The impact of the
works on the adjacent mangrove area will be a focus for monitoring activities. Works may need to be extended or modified if
erosion is significantly exacerbated.
Figure 40: Natural Mangrove Erosion [assuming ongoing erosion at recent average rates]
Page 56
4.1.6. Flooding
Numerical modelling indicates that should be no significant change to upstream velocities or levels during a normal tidal
cycle as a result of the proposed works. Flood modelling has not been undertaken, however previous floods have resulted in
the development of a dominant middle channel and the proposed works would not affect this development during future flood
events. As the works are essentially within the footprint of the 2002 shoreline, any potential impact of the works is
considered to be within the natural variability of the estuary and should not result in increased tidal levels or flood risk to
areas upstream.
4.1.7. Flushing
While areas within the lagoon are typically calm, previous sand bunds experienced adequate flushing and it is expected that
this would also be the case with the proposed closure. Velocities within the lagoon are likely to change in response to
changes in river configuration. If necessary, consideration could be given to changing the crest level as part of the
monitoring works.
4.1.8. Swimmer safety near submerged closure
Velocities over the closure are higher than within the lagoon, but are typically limited to the comparatively narrow width of the
structure itself. This will not compromise the structure itself, but may be of concern with regards to swimmers using this area,
particularly if velocities could result in users being swept into the edge of a dominant navigation channel. It is noted that
there were no apparent safety concerns as a result of the sand bunds and velocities would be expected to be similar. Safety
considerations should continually be reassessed with consideration given to actual velocities, location of the dominant
navigation channel and usage of the lagoon. If swimming within the lagoon or near the structure is not recommended,
suitable precautions may need to be taken. This may include signage and/or barriers at the shoreward ends of the
structures to reduce or control usage and may also include placement of buoys at some distance from the structures to limit
the proximity of vessels to the structure.
4.1.9. Navigation
As the works involve closure of a channel, there is the potential for vessels to impact with the structure. As such, the
structure will need to be suitably marked in accordance with MSQ requirements / recommendations. It is anticipated that this
could include provision of a beacon at the end of the training wall and buoys at points along the length of the submerged
closure. A Notice to Mariners would also need to be issued.
4.1.10.Vandalism /Vessel impact with the structure
While the containers are to be fabricated using a robust 1209RP geotextile (or equivalent), there is the potential for
vandalism, large debris or vessel impact with the structure to result in damage to the containers. Emergent sections of the
structures will be particularly vulnerable. Tears or cuts in the geotextile will allow migration of material out of the container
and gradual deflation of the container over time and eventual removal of the container from the structure. If damage is
identified, maintenance [patching] should be undertaken as soon as practicable. If a partially deflated container cannot be
patched, it should be replaced. Both patching and removal of containers can be undertaken with relative ease and minimal
expense by Council staff. In the event that maintenance becomes a burden, consideration may be given to armouring the
structure with rock [alternative materials may also be considered] once the structure is accepted.
4.1.11. Structural aspects
Risks associated with the individual structures [e.g. undermining and overtopping] have been addressed as part of the
preliminary design review.
Page 57
5. CONSTRUCTION MATERIALS
A number of construction materials were considered, including:
• Rock - suitable
• Sand-filled geotextile containers [both smaller units and mega-containers] - suitable
• Concrete walls - not flexible enough to accommodate erosion
• Concrete modules - not in keeping with the natural visual appeal of the area
• Reef balls - unlikely to be effective
• Combination
5.1. Sand-filled geotextile containers
Construction of submerged structures using sand-filled geotextile mega-containers is not common, but has been undertaken
successfully in the past. This would be achieved by:
• Excavating / dredging to the design base level [within tolerance] and with suitable batters - material to be used for
construction [filling of containers], beach nourishment and backfilling, as required.
• Container to be rolled out and anchored in place using barge-mounted equipment and divers
• Fill the container using dredge or jet pump
• Seal container with closures using divers
Construction of structures using smaller 2.5m3 sand-filled geotextile containers would require creation of a working platform
with a sand stockpile for filling and stockpiling of containers. These could then be placed either onshore using excavators or
in submerged locations using barge mounted excavators. For greater depths, slings can be used, but placement accuracy is
lower.
The manufacturer advises that the 1209RP geotextile has an official lifetime when fully exposed to UV conditions of 25
years, which is considered to be conservative. As the structure will be submerged a large part of the time, the geotextile
promotes the ingress of sediment into its structure and will likely provide a suitable substrate for marine growth (all of which
will reduce the UV reaching the geotextile), it is anticipated that the actual lifetime of the structure could be longer.
5.2. Rock
Construction of structures using rock would require importing of material. Importing by truck would result in a significant
impact on Hastings St and require clearing of a significant access track (700m x 3m = 2100m2) along the length of Noosa
River Spit, a designated koala habitat area. This is generally considered to be undesirable and should not be considered
providing that costs for delivering the rock by barge are acceptable.
5.3. Comparison
A comparison of sand-filled structures and rock is presented in Table 1.
Table 1: Advantages & disadvantages of rock & sand-filled aeotextile containers
Sand-filled Geotextile Containers Rock
Advantages Advantages
• Stable with suitable container sizes • Stable with adequate rock sizes
• Can be designed to allow for scour • Can be designed to allow for scour
• Flexible to accommodate additional scour if necessary • Flexible to accommodate additional scour if
• Easily removed / modified / extended if necessary necessary. Easily topped up.
• Uses local materials [no need to import materials] • Easily extended
• Uses floating plant [no access issues] • Robust [no potential for damage]
• User-friendly Voids may create habitat
• Substrate may provide
• Cost
Disadvantages Disadvantages
• Vulnerable to damage from vandalism / vessel impact Import of materials required
even with robust RP geotextile. Higher maintenance. If importing by truck, need for clearing and traffic
• Replacement cost [25year lifetime] issues along Hastings St
• Less user-friendly
• Cost
• More difficult to remove
Page 58
6. PRELIMINARY DESIGN & COSTING
6.1. Submerged "Closure"
While placement of bulk sand to form a natural bar has successfully been undertaken in the past, rapid erosion of the
material and turbidity associated with ongoing dredging makes this undesirable. Sand-filled geotextile mega-containers are
preferred because rock is less user-friendly and smaller units may not be stable. As the structure will be predominantly
submerged, there will be no visual impact the majority of the time and during lower tides the structure may be partially
emergent [Figure 41].
.1
z
Figure 41: Low-crested breakwater constructed using sand-filled geotextile mega-containers
Preliminary design has been prepared [Figure 421.
Crest Lagoon
HAT RL-0,6m AHD ,4 Mid-tide -wi vanes -
5m
- 1 V:3H
LATE Nourish
Dredge
1V:2H
RL-5 . 8m AHD
12m
Figure 42: Preliminary design of submerged "closure"
The crest level of the "closure" is RL-0.6m AHD [as per the modelling]. This means that the structure will be predominantly
submerged and only partially emergent on lower tides. The temporary sand bunds constructed previously were at a similar
or higher level and did not experience any water quality issues associated with poor flushing. As such, flushing is expected
to be adequate for the proposed structure. Crest height can be raised in future, if monitoring indicates that this is desirable.
Preliminary design has allowed to take the closure to a depth of approx. RL-6m AHD, over 1m lower than surveyed
maximum channel depths within the Noosa entrance (and 2 - 6m below current depths). The only location which is in
excess of this depth is adjacent to the water inlet for the sand recycling and this is not in close proximity to the structure.
Still, given the variability of the river and the proposed staging of the works, it is possible that at some point during the life of
the structure the "closure" could be subject to undermining due to channel deepening or local scour. In the event that
monitoring identifies that levels are approaching the foundation depth directly adjacent to the structure, placement of an
additional container on the river side may be undertaken at this point. Sand-filled geotextile containers are flexible and can
accommodate some settlement, although this would result in an equivalent lowering of the crest. Significant undermining
should be avoided as this could lower the stability of the crest container.
The alignment of the closure should follow that allowed for in the numerical modelling. For ease of construction, curved
closure may incorporate a short return direct into shore at the upstream end to minimize required excavation while
accommodating a reasonable level of erosion without breaching landward of the structure. The works may be terminated at
the existing low tide mark and allow for flows into the lagoon landward of the structure provided monitoring is in place and the
closure is extended if required. There is also the potential to raise the level of the return to create a third groyne if monitoring
indicates that this would be desirable.
Preliminary estimate of the associated costs is as per Table 2.
Page 59
Table 2: Preliminary cost estimate for submerqed "closure"
Qty Rate Amount
ex-GS
Establishment $100,000
Excavation [dredging] and nourishment / backfill 22.000 m3 S12 $265,000
Supply mega-containers [vandal resistant eotextile 60 511,620 $700,000
Place and fill mega-containers 60 $6,000 $360,000
Water quality testing Allowance only $30.000
Project management 5% $60.000
TOTAL $1,515,000
6.2. Training Wall
A range of materials were considered for this component, including:
• Rock
• Sand-filled geotextile mega-containers
• Combination
Figure 43: Training Wall constructed using rock or sand-filled mega-containers
Page 60
Preliminary design has been prepared [Figure 43].
Rock Design 2m [barge construction]
OR 4m [land-based construction]
od lei
HA Armour 1V:1.5H
Rock
EA1
Sand-filled Geotextile Container Design
100yr flood level
HAT
LAT
Dredge
J W V.21-1
W_
RL-3.5m AHD
Max -6.1 m AHD
18m
Sand-filled Geotextile Container Design with Rock Armour
Figure 44: Preliminary design of training wall
Modelling was undertaken using emergent structures and, as such, the crest level must be above HAT with some allowance
for wave action. It is intended that the top of the training wall be at approximately 100yr flood height. Design of the structure
is such that it can accommodate any minor overtopping during events.
Preliminary design has allowed to take the closure to a depth of approx. RL-6.1 m AHD, over 1.5m lower than surveyed
maximum channel depths within the Noosa entrance (and 4-6m below current depths). The only location which is in excess
of this depth is adjacent to the water inlet for the sand recycling and this is not in close proximity to the structure. Still, given
the variability of the river and the proposed staging of the works, it is possible that at some point during the life of the
structure the training wall could be subject to undermining due to channel deepening or local scour. In the event that
monitoring identifies that levels are approaching the foundation depth directly adjacent to the structure, an additional
container or rock could be used to provide additional scour protection. The structure is flexible and can accommodate some
settlement, although this could result in lowering of the crest.
An 80m training wall has been allowed. This brings the structure to approximately low tide mark, beyond which construction
becomes impractical. Shoreward of low tide, it is anticipated that sand fill will be placed to allow for the construction of a
revetment wall detail [see section 6.3]. The placed fill on the eastern side of the training wall will be stable as this region will
be very well protected by the training wall.
The last 100m of the Noosa River Spit is low-lying and subject to inundation on king tides and during flood events. As such,
there is the potential for breaching at the shoreward end of the groyne during a flood event. To avoid this, it is intended to
link the proposed training wall with a location which is not subject to inundation during flood events.
Page 61
Preliminary estimates have been prepared [Table 3 - Table 6].
Table 3: Preliminary cost estimate for training wall [rock brouqht in by truck option
Qty Rate Amount
ex-GS
Establishment $100,000
Clearing, temporary access track & revegetation $200,000
Approval fees associated with clearing
Excavation 3.600 m2 $12 $45,000
Supply & placement of geotextile 600R 2.000m2 $10 $20,000
Supply of rock 3,100 m3 $60 $185,000
Delivery and placement of rock 3,100 m3 $120 $375,000
Project management 5% $45,000
TOTAL $970,000+
Table 4: Preliminary cost estimate for trainin wall [rock brou ht in b bar e o tion
Qty Rate Amount
ex-GS
Establishment $100,000
Excavation 3,600 m2 $12 $45,000
Supply & placement of geotextile 600R 2,000 m2 $10 $20,000
Supply of rock 2,700 m3 S60 $160,000
Delivery and placement of rock are 2,700 m3 $160 $435.000
Project management 5% $40,000
TOTAL $800,000
Table 5: Preliminary cost estimate for traininq wall [sand-filled qeotextile container option
Qty Rate Amount
]ex-GST]
Establishment $100,000
Additional excavation 400 m3 $12 $5,000
Supply mega-containers [vandal resistant geotextile] 17 $11,620 $198,000
Excavate, place and fill mega-containers 17 $6,000 $102,000
Project management 5% $20,000
TOTAL $407,000
Table 6: Preliminary cost estimate for traininq wall [sand-filled qeotextile container with rock armour option
Qty Rate Amount
ex-GS
Establishment $150,000
Additional excavation 400 m2 $12 $5,000
Supply mega-containers [vandal resistant geotextile] 17 $11,620 $198,000
Excavate, place and fill mega-containers 17 $6,000 $102,000
Supply of rock 1400 m3 $60 $85,000
Delivery and placement of rock are 1400 m3 $160 $225,000
Project management 5% S40,000
TOTAL $805,000
While it was originally preferred to construct using sand-filled mega-containers in the first instance and subsequently armour
with rock due to concerns regarding the potential for damage. During stakeholder consultation, it became evident that there
were concerns regarding the use of rock, the difficulty of removal and the visual impact. At this stage, the preferred option is
the sand-filled geotextile container training wall, although if maintenance becomes an ongoing issue, further consideration
may be given to rock armouring.
Page 62
6.3. Revetment Wall
Given the difficulty of placing smaller containers at an adequate depth, only rock and mega-containers [Figure 45] are
considered to be suitable. It was originally preferred to construct the wall using rock given that the structure was emergent
and therefore potentially vulnerable to vandalism.
Figure 45: Wall constructed using rock or sand-filled geotextile containers
Preliminary design has been prepared [Figure 46].
HAT
EM
1 V:1.5H
RL -3,5m AHD
HAT
Natural surface levelLAT
[varies]
Dredge
1 V:2H
15m RL-5 6m AHD
Figure 46: Preliminary design of revetment wall
The top of the existing bank at the end of the Noosa River Spit ranges from RL 0.3m to 1.Om AHD. As such, much of the
end of the Noosa River Spit is inundated during king tides and flood events. As construction of a full-height wall would be
-1.5m above natural surface levels, it has been decided to construct a wall that was more in keeping with natural levels and
can accommodate some inundation during king tides and flood events. As such, there is the potential for some erosion
behind the wall during flood events. While the structure can accommodate some scour at the crest, excessive scour may
result in slumping of the crest. It is assumed that required maintenance [including backfill] will be handled through post-flood
maintenance works.
The channel is very close to the bank along the southern end of the Noosa River Spit and ongoing erosion has resulted in
the majority of the foreshore being relatively steep (approx. 4H:1V) to a channel depth of approx. -3.5m AHD. Despite this,
there is the potential that the channel will migrate northward and become entrenched adjacent to the structure. This
potentially could result in deepening of the seabed adjacent to the toe of the rock wall in excess of current maximum channel
depths in this location. A rock design is flexible and "top-up" is simple and effective, so the preliminary rock design has been
minimized with a toe at -3.5m AHD [-1m below existing levels]. As "top-up" of mega-container structures is not as simple
and slumped structures are not as visually appealing, it was necessary to take the base of this option deeper [to -5.6m AHD]
to allow for additional scour.
Page 63
The alignment of the revetment wall will follow the eroded top of bank. At the south-eastern end, the wall terminates at the
start of the mangroves. As natural levels of erosion are substantial in this area, it is expected that there could be some
flanking of the wall associated with erosion of the mangroves and, as such, a return detail will be necessary in this location,
although given the extent of the potential erosion, the return may need to be periodically extended.
Preliminary estimates have been prepared [Table 7 & Table 8].
Table 7: Preliminary cost estimate for revetment wall [rock option]
Qty Rate Amount
ex-GST
Establishment $50,000
Excavation 1,500 m3 $12 $20,000
Supply & placement of geotextile [600R] 1,500 m2 $10 $15,000
Supply of rock 2,220 m3 $60 $135,000
Delivery and placement of rock bare 2,220 m3 $160 $355,000
Project management 5% $30,000
TOTAL $605,000
Table 8: Preliminary cost estimate for revetment wall [mega-container option]
Qty Rate Amount
[ex-GST]
Establishment $100,000
Excavation 6,600 m3 $12 $80,000
Supply & placement of geotextile [600R] 1,500 m2 $10 $15,000
Supply mega-containers [vandal resistant eotextile 25 $11,620 $290,000
Excavate, place and fill mega-containers 25 $6,000 $150,000
Project management 5% $30,000
TOTAL $665,000
It was originally preferred to construct using rock due to concerns regarding the potential for damage. During stakeholder
consultation, it became evident that there were concerns regarding the use of rock, the difficulty of removal and the visual
impact. At this stage, the preferred option is the sand-filled mega-container wall, although if maintenance becomes an
ongoing issue, consideration may be given to rock armouring.
6.4. Groynes
While the upstream areas of Noosa River Spit are not as popular as the central sections, the creation of a beach along this
section of foreshore will likely encourage increased usage and, as such, any structures placed in this location should be
user-friendly to ensure access along the length of the foreshore. Placement of rock structures across the foreshore will likely
restrict access and introduce safety hazards associated with voids in the structure and, as such, are not desirable. While
construction could be undertaken using geotextile mega-containers, as is proposed for the submerged "closure", the
changing seabed levels over the length of the structure mean that this will result in a need for significant excavation and will
not provide an efficient design. Construction of the groynes using smaller 2.5m3 sand-filled geotextile containers [Figure 471
is preferred. This has been undertaken very successfully and is also deemed to be suitable for this location.
Figure 47: Groyne constructed using 2.5m3 sand-filled geotextile containers
Preliminary design has been prepared [Figure 48].
Page 64
HAT
Scour Scour
Seabed [varies]
Figure 48: Preliminary design of groynes
The groyne has been designed as an emergent structure. The crest height has been nominated as approx. 1 m above HAT
to allow for wave action without significant overtopping. The base of the structure is variable to reflect changing surface
levels along the length of the structure. As a minimum the base containers should be 0.7m below the surface level [greater
at the head of the groyne] with scour containers to accommodate greater erosion.
Preliminary estimates have been prepared [Table 9]. It is noted that this is based on existing surface levels and could vary if
levels change.
Table 9: Preliminary cost estimate for 2 groynes
Qty Rate Amount
[ex-GST]
Establishment $100,000
Supply of 2.5m3 containers [standard] 175 $300 $52,000
Supply of 2.5m3 containers RP 260 $185 $48,000
Dredging to provide suitable sand stockpile 1,087 m3 $12 $13,000
Fill & placement of 2.5m3 containers 435 $280 $122,000
Project mans ement 5% $15,000
TOTAL $350,000
6.5. Dredging
There is an existing secondary southern channel [Figure 13] which is proposed to be deepened slightly to provide adequate
navigation after closure of the primary southern channel by the proposed works. Existing depths are presently approx. -0.5m
AHD. It is proposed to deepen this channel to approx -2m AHD (-1m LAT). The proposed deepening will require the
removal of approx. 10,000m3. Material is to be placed as foreshore nourishment and/or backfilling adjacent to structures as
required.
Table 10: Preliminary cost estimate for dredqin
Qty Rate Amount
ex-GST]
Establishment $100,000
Dredging / Nourishment 10,000m3 $12 $120,000
Project management 5% $10,000
TOTAL $230,000
6.6. Total Strategy
Preliminary costs associated with the complete strategy [Figure 39] are as per Table 11.
Table 11: Summary of costs
Amount
[ex-GSTJ
Submerged closure $1,280.000
Training Wall $ 407.000
Revetment Wall $ 665.000
2 Groynes S 350.000
Dredging / Nourishment $ 230.000
Page 65
TOTAL $2,932,000
6.7. Staged Works
Staging of the works is desirable to minimize the impacts, allow for monitoring and stage the costs. As such, Stage 1 works
are proposed to include [Figure 49]:
First 80m of the downstream submerged closure [linking with the existing sand bank] to prevent breaching
Training wall to prevent breaching
Revetment wall to prevent further erosion at the end of the Noosa River Spit
Dredging to provide alternate navigation [use of material as nourishment of foreshore]
As the river evolves, it may be necessary to extend the submerged closure and construct the short groynes to complete the
proposed works. Monitoring may also result in modifications to improve performance or reduce impacts.
^ . R y
'4i ,,
1
:^
Subrner9ed Closure
Crest at low This
r Its
" ^^
Dredging
, Ai:
^
. ^ C
^i
ti U
Nourishment
(raining rvan r i
-. • _ ... .>►7^
Crest et flood heght `r
^ ..
;a^, r;"` ,^~'
MG{^,.r: s{` :t'`^^i ' `.
Wall // `^*
^ t •;
Crest at surface level j ^ •' ' '7 r. 7 '4' . _ a 5+ r
faoorox high tidel ' -^ • .. v':..`^ ti:+ar^► .'.. ir+
_ ' + s
s ly
r M
^ ...w
^i•• i •. •` • S" ••
Figure 49: Proposed Stage 1 Works
Preliminary estimates have been prepared for the first 80m section of the submerged closure [Table 12].
Table 12: Preliminary cost estimate for Staqe 1A (80m submerged downstream "closure")
Qty Rate Amount
ex-GS
Establishment $100,000
Excavation [dredging] and nourishment! backfill 3,000 m3 $12 $50,000
Supply mega-containers vandal resistant eotextile 12 $11,620 $140,000
Place and fill mega-containers 12 $6,000 $72,000
Water quality testing Allowance only $10,000
Project management 5% $15.000
TOTAL $387,000
Page 66
A summary contract cost estimate for proposed Stage 1 works is provided in Table 13. It is noted that estimates are based
on preliminary designs. Costs assume a single establishment for all Stage 1 works. Non-contract costs (e.g. project
management) not included. It is noted that thes costs are estimates only and costs may vary. In particular, establishment
costs may vary depending on the type, size and availability of equipment to be used. Timeframe for works will depend on
the equipment to be used.
13: Summar of Preliminary Contract Costs for Proposed Stage 1
Qty Rate Amount
ex-GS
Establishment 1 $100,000
Contract documentation 1 $10,000
Northern section of curved "closure" 80m $250,000
Trainin g wall 80m $305,000
Revetment wall $530,000
Dred in / nourishment 10,000m3 $12 $120,000
Water quality testing Allowance only $30,000
TOTAL $1,345,000
Page 67
DRAWING REGISTER
International 01.04.2011 REV B
NRS-001 LONG-TERM STRATEGY
Coastal NRS-002
NRS-003
PROPOSED STAGE 1 WORKS
SUBMERGED CLOSURE LAYOUT
NRS-004 SUBMERGED CLOSURE TYPICAL CROSS-SECTION
Management NRS-005
NRS-006
WALL AND GROYNE LAYOUT
GROYNE TYPICAL CROSS-SECTION
NRS-007 WALL TYPICAL CROSS-SECTION
OFFICE 501 G Arm, SYC Marina, Main Beach, 4217, QLD, Australia
NRS-008 DREDGE AREA LAYOUT
POST PO Box 306, Main Beach LPO, Main Beach QLD, 4217, Australia NRS-009 DREDGE AREA TYPICAL PROFILE
TELEPHONE +617 55640564 FAX +617 55329147 NRS-010 NOURISHMENT TYPICAL PROFILE
WEBSITE www.coastalmanagement.com.au NRS-011 NOTES
NRS-012 VEGETATION
NOOSA RIVER SPIT
EROSION PROTECTION WORKS
Page 68
Long-Term Strategy Includes:
• Retain erdsdng rock wall Imstak t
w7adel
• Submerged Curved channel 'Closure
enclosing lagoon
• Wall at and of Noose River Spit
• Groyne I Training Wall
• 2 short groynes
• Dredging for interim navigation
• Foreshore nourishment
• Removal of dead trees (marine plants)
as requited
• Monitoring program
• Maintenance of all structures
For details of strategy, refer ICM report
'Option Review - Noose River Spit'
5. A Coastal Management District has not been
declared for this area. The Erosion Prone
Area Is the full width of the Spit.
6. Aerial photo from Google [June 20081.
Channel configurations have altered.
I
I
L MC 'Y4}t.Y tV
International
Coastal
Management
NRS-OO1
Page 69
Proposed Stage I Wald:
• Retain existing rock wd Irnelntain I
upgrade)
• Widening of existing footpath for
construction aaau
• Northern section of submerged
channel closure
• Wal aI end of Noose River Split
• Groyne I Training Wall
• Dredging for Interim navigation
• Removal of dead sea (mWkr plorila)
7081700 as required
• Foreshore nourishment
• n ^g
Existing footpath Ito be widened for
construction access) Rydrographic survey by SCRC on 23rd
November 2010.
3. Works to be undertaken in accordance t1Ah
'Noose River Spit Concept Envlmrw*M
Management Plan' prepared by ICM.
4. Drawings to be read In con junction with
Notes on drawing NRS-01 1.
7081600
Groyne / Training Wall to limit
channel migration [see drawing
-005 & -006 for details)
LEGEND
Structure Crest l 1
Structure Too I I
Dredge Area I !I
Nourishment Area
RP Boundary
Intemational
Coastal
Management
W yw? V" C2 4•mal
• MWWO.D42170ab
NOOSA RIVER SPIT
PROPOSED STAGE 1 WORKS
NRS-002
t" ,
Page 70
Excavation not
to undermine
existing rock wall
2. Works to merge with existing rodh wad.
Rock to be placed as required to
conned the two structures smoothy.
Works to be In accordance with
separate rock wall approval.
Stage I - Submerged Closure
Crest Centreline
Point Eastkg Northing
C, 508059.9 7081711.1
Cr 508058.5 7081691.6
C3 508054.9 7081672.1
Cr 508049.0 7081653.0
Cs 508040.4 7081634.9
CS 508038.3 7081630.6
Cl 508027.8 7081613.6
C. 508016.7 7081596.9
Cs 7081581.3
Cs 507990.5 7081566.7
Cl, 507975.8 7081553.1
Cl, 507980.3 7081540.5
C, 507944.0 7081528.9
Closure may be lnr 507927.3 7081517.9
Gs 507910.2 7081507.5
extended aluny design 507892.9 7081497.5
cle
alignment if G7 507888.7 7081495.2
CIS 507890.6 7081484.0
desired/required
4. Refer to additional drawings
Typical ssection NRS-004
Nourishment NRS-010
Notes NRS-011
O
RFVISION REGISTE
International
Coastal
Management
NOOSA RIVER SPIT
SUBMERGED CLOSURE LAYOUT
RS-00
0
0
0
Co
0
LO
Page 71
1. Crest height such that structure is partially
emergent on very low tides only.
Extent of works to be restricted to limits
shown on drawings. Container configuration
West side: East side: to achieve design may vary.
Backfill to levels No Backfill required Profile based on survey by SCRC on 23rd
as per NRS-003 November 2010,
4. Excavation
4.1. Batters may be formed by an equivalent
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ----------------- ------------------- - HAT _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ box cut.
----..-.---------------------------- --------- ----------- --------------------------------------- 42. Expected volume to be disturbed
----- RL-0.6mAHD --- ------------------ AHD Idosurel : 5950m3. May vary with
--------------------------------
- MLWS seabed changes.
-------- - ---- - 4.3. Material is clean sand suitable for beach
-------- ------------------ -------------- -----
nourishment.
4.4. Excavated material may be used for:
NSL (varies) • construction [filing containers)
• backfilling adjacent to structure
• foreshore nourishment.
Optional additional tube may be placed as
part of initial works or placed (if required) In
response to monitoring.
Refer to additional drawings
Optional I lm geotextile tube Plan layout NRS-003
1m 11.7m 1m
Notes NR$-011
with flap [if required]
West side:
Backfill to levels
as per NRS-003
----------------
-----------^tFW^----------------
------------ AHD
MLWS
----------------- -
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ;ERTIG4 0AT1J5 :^IC AORI20'ITA- OATJM MG
LAT
NSL (varies)
Excavated slope such that
existing rock wall not to be
undermined
- RL -5.80m AHD
Optional 1 m geotextile tube J
with flap [if required]
ZrICc '1;: fix VC Molk% 12 ears 4217 aD Aus2ab
NOOSA RIVER SPIT
SUBMERGED CLOSURE
TYPICAL CROSS-SECTION
NRS-004
Page 72
7081500
Centrebne of crest as per table below.
Stage 1 - Groyne and Wag
Crest Can elirm
Point Easting Northing
G 507685.8 7081499.4
G7 507679.0 7081491.3
G, 507591.6 7081384.8
4. Rotor to additional drawings
Typical x-section NRS-006 & -007
Noudshmeol NRS-010
Notes, NRS-011
7081400 Link between groyne crest
& RL +1.5m AHD
FIN to slope from RL+1.5m AHD to NSL
Top container to follow top of bank as close as
practicable without disturbing live vegetation
International
Coastal
Management
7081300
Page 73
Crest height such that structure is fully
emergent. May experience some
overtopping during significant Hood events
[particularly with high levels of surge and/or
waves].
2. Extent of works to be restricted to limits
shown on drawings. Container
configuration to achieve design may vary.
3. Profile based on survey by SCRC on 23rd
November 2010.
4.1. Batters may be formed by an
equivalent box cut.
4.2. Expected volume to be disturbed (well
L & groyne(: 17,600m3. May vary with
East side: West side: seabed changes.
4.3. Surface sediments are clean sand
No Backfill required Backfill to RL -3m AHD [min) suitable for beach nourishment.
4.4. Materiel below RL -4.5m AHD may
contain acid sulphates.
NOT to be placed above LAT.
RL +1.5m AHD To be used for:
• construction [ Mng containers]
--------------- -------------------------HAT • backfilrg
--------------- -------------------------MHWS
------------ ----------------------- AHD 5. Optional additional container may be placed
as part of Initial works or placed (tf required]
------------ -------------------------MLWS In response to monitoring.
------- ---------------------------- ------------------------------------- LAT
NSL [varies]
6 Refer to additional drawings
Plan layout NRS-0O5
1 Notes NRS-01 1
2 Anticipated excavated
profile [may vary]
- Up to RL -5.90m AHD as required
-J1mi 16.8m Optional 1 m geotextile tube
with flap [if required]
.nrcN J-UN 1i 4. A M w"-
International
Coastal
Management
,Irl.l x- W e•.' 4:l 1n 1-6
t1-iUA'4'
NOOSA RIVER SPIT
GROYNE TYPICAL
X-SECTION
NRS-006 B
Page 74
Crest Might such r 4A structure Is lev al with
NSt (or as dose as prlttabb). Wit be
overtopped on Ngh dales.
2. Exunl of works to be res olcud to limits
shown on drMNps. Contetler anflpurwon
to achIM design may very.
3. For esavedon notes. sae drawing NRS-006.
4. Optional additional oonWUr may be placed
as pan of Initial works or pbcW IN required)
In response to monltodng.
Backfill if required 5. Refer to additional drawings
F Anticipated excavated profile Plan layout NRS-005
Top of bank Notes NRS-O11
[may vary]
Level with Adjacentlop.QLBank - - - -------------------------------HAT
-------------------------------MHWS
---------------------------- AHD
-------------------------------MLWS
LAT
Optional 1 m geotextile tube with flap
[if required]
FTR1.-N : TIM 4,U lNoRIioMN U+1LV 4UA
International
Coastal
Management
A••s"tl 's 11i4 1r& 4:'7 d;e Awes
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L.. 'l .47 ypow 2L -01116.721'47
NOOSA RIVER SPIT
WALL TYPICAL CROSS-SECTION
NRS-007
Page 75
Dredging Is to be entirely within water
allocation area INRS.RE-0011. Final location
6 extent to be determined after pre-start
survey to accommodate channel movement
prior to works.
nI
7081700
It is anticipated that dredging works will
Include enhancement [widening &
deepening] of existing channel. May Involve
enhancement or creation of secondary
channel to provide alternative access If
required.
Temporary navigation aids to be provided by
the Contractor throughout the works to the
satisfaction of Regional Harbour Master.
7081600 Permanent navigation aids to be Installed as
requires by Regional Harbour Master.
International
Coastal
Management
nakl WinB-t 1."7 o.D A.wi
POt yr B-1 SO 11* exws Q.D 4217 Napa]
1ELEPJAL •r 7c ..WI L& -vi755721117
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NOOSA RIVER SPIT
DREDGE AREA LAYOUT
W
NRS-008 B
Page 76
Final dredge profile to be determined after
Pre-Start survey.
Maximum dredge depth to be RL -3m AHD
to avoid acid sulphate materials.
Batters (IV:3H) may be formed by an
equivalent box cut.
Material is dean sand suitable for beach
nourishment.
S. Refer additional drawings
Centreline NRS-008
Dredged material may be used for.
• construction (filling containers)
• bedriing adjacent to structur es
• foreshore nourishment.
Existing Channel
------------------------------------------------------------------------------------------HAT
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - MHWS
-------- ------------------ AHD
-
-------MLV
RL -3,Om AHD Q 1
3
P os sibl e dr ed ge p ro fil e
[widenin g & dee penin g existin g channel]
Internationa l
Coastal
Managemen t
rna v-x WF Ar CP O.D A--*
V- fk^ --V MW %W O-D C1 7
NOOSA RIVER SPIT
DREDGE AREA TYPICAL PROFILE
NRS-009 B
Page 77
All material placed on the foreshore to be
dean sand suitable for nourishment.
Adjacent to groyne. profs to widen such that
new HAT alignment to be in accordance with
drawing NRS-005.
5m
Reprofile to top of bank as required.
Lowest of
Design nourished profile
RL 1.06m AHD
or top of bank
----------------- ------------------ ------ L-- -------------HAT
--------------------------------------- --------------- ----- - - --------------
- AHD S
-MLWS
-LAT
3
[varies]
International
Coastal
Management
NOOSA RIVER SPIT
NOURISHMENT
TYPICAL PROFILE
NRS-010 B
Page 78
1
NOTES
i
1. Design conditions
1.1. Tides [QT tide tables, Noosa Head]
AHD LAT
HAT +1.06m +2.18m Sand-filled Geotextile Containers
MHWS +0.62m +1.74m Finished dimensions
AHD +0.00m +1.12m [Filled above water level]
MLWS -0.80m +0.32m
LAT -1.12m +O.00m
1.2. Flood [Noosa River Flood Study, John Wilson & Partners, 1995]
50yr ARI 1.44mAHD
entrance scour 0.5m
Nominal Diameter = 3.Om
1.3. Currents [GCCM numerical model] 1.3m
Max spring tide 1 -1.5m/s. Volume = 81m3
Velocities expected to vary in response to prevailing channel configurations and location within
the estuary.
1.4. Waves
Hs 1 m [nominal] 4m
Potential wave conditions at the foreshore are expected to vary in
response to prevailing channel configurations. Nominal Diameter = 3.4m
1.5m
Volume =103m3
2. Materials - Geotextile and Sand-filled Geotextile Mega-Containers
2.1. Containers to be fabricated using ELCOMax 1209RP geotextile (or equivalent). Expected lifetime
25 years.
2.2. Container length to be 20m [may be altered if necessary or preferred by contractor].
2.3. Containers to have suitably spaced filling ports [MIN 3 preferred] with "screw & glue" closure types. 5m
2.4. Geotextile underlay to be ELCOMax 60OR (or equivalent)
2.5. Geotextile flaps, where required, are to be of sufficient size to provide a 30m x 6m flap. Flaps are to
be fabricated using ELCOMax 60OR (or equivalent). Flaps are to be adequately secured (e.g. Nominal Diameter = 4.2m
stiched) to the bottom of the container. Volume =183m3 T3 2.Om
2.6. If flaps cannot be fabricated, may be replaced with separate geotextile fabric with 1 m laps.
3. Filling of Containers
3.1. Excavation tolerances 6m
Vertical +1- 0.2m
3.2. Containers to be filled In accordance with manufacturer's specifications using either jetpump, dredge \ T
or suitable alternative.
Nominal Diameter = 4.6m
3.3.
3.4.
Design filled container dimensions as shown.
Finished container tolerances
Volume = 224m3 T4 2.2m
Horizontal +1-1.0m from design alignment [containers to be well butted together]
Vertical +1- 0.5m at any single point
+1- 0.3m averaged over 1 Om
4. Maintenance
4.1. Nominated geotextile is more robust than the standard geotextile, however may be subject to Sand-filled Geotextile Containers .7"11CN :A,VV 1.O IA :Ah$t VJ.
damage from vandalism, vessel impact, anchors etc. Finished dimensions
[Filled below water level] 6m
4.2. Structures to be Inspected periodically and after all major events.
4.3. Any minor damage Is to be repaired as soon as practicable.
4.4. Any major damage or deflation and the container is to be replaced.
4.5. If damage is an ongoing concern, consideration may need to be given to armouring the structures Nominal Diameter = 4.6m
[e.g. with rock].
4.6. Scour may require topping up with additional containers or placing of rock in scour holes
International
5. Monitoring
5.1. The natural system is highly variable. Monitoring is to be undertaken in accordance with ICM Report 6m Coastal
"Option Review - Noosa River Spit" to determine the performance and impacts of the works. Management
5.2. Works may be modified or removed if monitoring indicates that this is necessary. A V. to. - .UO bw I.* QD 4717 Ane.
N: 1 -01776
f^( '11
5.3. Implementation of later stages of the works to be undertaken as required. Flap Detail
T4 2.6m
.:.at4wpwrtm"J1
NOOSA RIVER SPIT
NOTES
NRS-011
rB
Page 79
Extent of live marine
plants below HAT to
be removed
NOTES
1. Vegetation away by SCRC on 23rd
November 2010.
5m (approx) 2. Removal of Deed trot to be underakren In
accordance with the ConsVucdon
Management Plan.
3. Area of dead trees to be removed -7700m2
Area o fro marine plants to be removed
-Approx (clearing track) -275mt.
HAT
Area of terresbial plants to be removed
isting path to (clearing track) -10m'.
be widened for -
a. Traci widening to be undertaken In such e
construction way to Mdmbe the k pec no provide
access adequate access for construction equipment.
Extent of terrestrial
vegetation to be
cleared (separate
approval)
Nourishment
Top of Bank
LEGEND
Dead trees to be removed
Live marine plants to
be removed (below MAT)
TerresbW plants to
be removed
Lot 114
MCH839107
International
Coastal
Management
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• , ,b of 9-1110 ur11W,W,4217 +vat.
t1,.rt Wdmu fa .617%M,47
NOOSA RIVER SPIT
AFFECTED VEGETATION
NRS-012
O 0 O
O 0
00 0 0 O 710: w
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Used in these records
Development Application - Part 2 of 2 - Report & PlansRelated documentApplication case desk ↗
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