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Page 2
Document Control Sheet
Document: R.B23636.001.02.SEMP_final.docx
BMT Commercial Australia Pty Ltd
Level 8, 200 Creek Street Title: Noosa Spit SEMP Final Report
Brisbane Qld 4000
Australia
Project Manager: Matthew Barnes
PO Box 203, Spring Hill 4004
Author: Matthew Barnes, Katrina O’Malley Jones,
Tel: +61 7 3831 6744 Jessie Cullen
Fax: + 61 7 3832 3627
Client: Noosa Shire Council
ABN 54 010 830 421
Client Contact: Daniel Wishaw
www.bmt.org
Client Reference: 1819Q089
Synopsis: Shoreline erosion management plan for Dog Beach (Noosa Spit)
REVISION/CHECKING HISTORY
Revision Number Date Checked by Issued by
0 8/07/2019 JC MPB
1 21/10/2019 MPB JC
2 31/10/2019 MPB JC
DISTRIBUTION
Destination Revision
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Noosa Spit SEMP Final Report i
Executive Summary
Executive Summary
The Noosa Spit at Dog Beach has been identified as an erosion hot-spot, with narrowing of the man-made
peninsular presenting a risk of a future breakthrough. Primarily, this erosion is caused by natural migration of
the channel, driven by sand infilling of the river mouth, while boat traffic adjacent to the Dog Beach is a
secondary cause of bank erosion. Works completed in 2013 were successful in stabilising the western extent
of Dog Beach; however, the rate of shoreline recession in the middle section has since increased, prompting
the need for this investigation.
Avoiding a breakthrough at Noosa Spit is important for maintaining the multiple attributes that the community
currently values. The consequences of a breakthrough include:
• Reduced attenuation of the ocean tide and increases to peak high tide water levels in the lower Noosa
River. This reduces the freeboard for waterfront development and therefore increases the likelihood of
flooding driven by coastal and/or fluvial processes.
• Rapid and unpredictable morphological change following a breakthrough and further loss of coastal land
and open space that shelters existing development.
Within this projects, various shoreline erosion management options were considered for Dog Beach. A key
objective was to identify ways to reduce the risk of a breakthrough while maintaining or enhancing the
recreational, social and environmental values attributed to Dog Beach. The promoted management strategy
focuses on relocating sand from adjacent channels and shoals to replenish the Dog Beach shoreline. The
strategy seeks to provide protection from the risk of breakthrough by delivering a shoreline position equivalent
to the condition in 2013 with the following triggers for management action:
(1) The first trigger occurs when the recreational width at Dog Beach is lost. At this time beach nourishment
and the construction of ‘sand plugs’ to reduce the flow in the adjacent channel is to occur. These works
would be undertaken by a small cutter suction dredge, using a mobile pipeline to deliver the sand to the
placement locations. It is anticipated that the works would be repeated several times between now and
2040.
(2) The second trigger is represented by significant narrowing of The Spit width at Dog Beach (to ~20 m)
and signals that the shoreline replenishment and channel flow reduction strategy is not performing as
intended and/or the frequency of works is unsustainable. The notional 20 m width of land above the high
water mark represents the likely minimum development footprint required for land-based construction of
a seawall or similar shoreline protection structure.
The trigger-based approach is designed to avoid a seawall for as long as possible and only calls for
consideration of a seawall if the sand relocation works are unable to maintain the risk of a breakthrough at an
acceptable level. Ongoing resilience building actions, including revegetation and habitat management, are
expected to continue as part of routine maintenance.
The shoreline condition in 2019 suggests that the first trigger has been reached and therefore the shoreline
nourishment works proposed as part of the strategy could commence immediately.
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Noosa Spit SEMP Final Report ii
Contents
Contents
Executive Summary i
1 Introduction 1
2 Noosa Spit Shoreline Erosion 3
2.1 Introduction 3
2.2 Previous Assessments 3
2.3 Recent Observations 4
2.4 Current Shoreline Erosion Strategy 13
2.4.1 Recent Shoreline Recession 16
2.4.1.1 Movement of vegetated shoreline 16
2.4.1.2 Available Recreational Beach Width 19
2.4.1.3 Boat Wake 20
2.5 Potential Entrance Configurations for Further Assessment 21
3 Numerical Modelling of Entrance Configurations 23
3.1 Background 23
3.2 Waves (SWAN) 23
3.2.1 Nested Model Domain & Bathymetry 23
3.2.2 Model Configuration 23
3.2.3 Boundary Conditions 25
3.3 Hydrodynamics (TUFLOW FV) 25
3.3.1 Model Domain, Mesh & Bathymetry 25
3.3.2 Model Configuration 25
3.3.3 Boundary Conditions 26
3.4 Sediment Transport (TRANSPOR) 29
3.5 Numerical Model Calibration & Validation 29
3.5.1 Targeted Data Collection 29
3.5.2 Laguna Bay Waves 32
3.5.3 Laguna Bay Water Level & Currents 34
3.5.4 Noosa River Water Level 34
3.5.5 Noosa River Flow 38
3.6 Entrance Configuration Assessment 41
3.6.1 Impact to Water Level 47
3.6.2 Impact to Current Magnitude at Dog Beach 52
3.6.3 Assessment Summary 61
4 Shoreline Erosion Mitigation Options 62
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Noosa Spit SEMP Final Report iii
Contents
4.1 Introduction 62
4.2 Overview of Generic Options 62
4.2.1 Rapid Assessment of Options 65
4.2.1.1 Rapid Assessment Results 71
4.3 Multi-Criteria Analysis 72
4.3.1 Option 1a: sand plug at either end of Dog Beach 75
4.3.2 Option 1b: sand plug at southern end of Dog Beach 79
4.3.3 Option 2: extension of the existing groyne at Dog Beach 83
4.3.4 Option 3: extension of submerged breakwater and two new groynes 87
4.3.5 Option 4: three new groynes 91
4.3.6 Option 5: shore parallel seawall 95
4.3.7 Option 6: do nothing 97
5 Proposed Implementation Pathway 98
5.1 Introduction 98
5.2 Proposed Trigger-based Management Approach 99
5.3 Legislative Framework & Approvals 102
6 References 103
Appendix A Metocean Data Collection A-1
Appendix B Bathymetric Survey (Acoustic Imagery 2019) B-1
Appendix C Proposed Conceptual Options (PCG 2019) C-1
Appendix D Risk Assessment D-1
List of Figures
Figure 1-1 Noosa Spit SEMP Study Area 2
Figure 2-1 Artificial Closure of River Channel, 2003 (ICM, 2010a) 4
Figure 2-2 ICM (2010a) Proposed Ultimate Strategy (top); Stage 1 Works Completed in
2013 (bottom) 14
Figure 2-3 Dog Beach Shoreline, Pre- and Post-Strategy Implementation 15
Figure 2-4 Shoreline Recession Measurement Locations 17
Figure 2-5 Noosa Spit Width (m) 19
Figure 2-6 Dog Beach Recreational Beach Width 20
Figure 2-7 Historical Entrance Configuration Scenarios for Further Assessment: East-
west Aligned Channel (left) and Northeast-Southeast Aligned Channel 22
Figure 3-1 Wave Model Extents & Data Locations 24
Figure 3-2 Hydrodynamic Model Extent & Bathymetry 27
Figure 3-3 Hydrodynamic Model Mesh Detail at Noosa Spit 28
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Noosa Spit SEMP Final Report iv
Contents
Figure 3-4 Instrument Locations 31
Figure 3-5 Wave Timeseries Calibration: Mooloolaba Buoy (left) and Laguna Bay (right) 33
Figure 3-6 Laguna Bay Water Level, Current Speed and Current Direction Timeseries
Calibration 35
Figure 3-7 Lower Noosa River Water Level Timeseries Calibration: Tide Recorder 1 (top),
Tide Recorder 2 (middle) and Tide Recorder 3 (bottom) 36
Figure 3-8 Lower Noosa River Water Level Timeseries Calibration: Tide Recorder 4 (top),
Tide Recorder 5 (middle) and Tide Recorder 6 (bottom) 37
Figure 3-9 Noosa River Flow Timeseries Calibration at Dog Beach, Noosa Sound, Munna
Point and Noosaville 39
Figure 3-10 Instantaneous Measured and Modelled Current Speed during Peak Flood
(top) and Ebb (bottom) Conditions 40
Figure 3-11 2019 Existing Entrance Channel Model Bathymetry 42
Figure 3-12 1987 East-West Entrance Channel Model Bathymetry 43
Figure 3-13 2010 Northeast-Southwest Entrance Channel Model Bathymetry 44
Figure 3-14 Dog Beach Breakthrough Entrance Channel Model Bathymetry 45
Figure 3-15 Design Flood Event Entrance Channel Model Bathymetry 46
Figure 3-16 Peak High Tide Water Level: Existing (top), 1987 East-West Aligned Channel
Entrance Condition (middle) and Difference (bottom) 48
Figure 3-17 Peak High Tide Water Level: Existing (top), 2010 Northeast-Southwest
Aligned Entrance Channel Condition (middle) and Difference (bottom) 49
Figure 3-18 Peak High Tide Water Level: Existing (top), Dog Beach Breakthrough
Condition (middle) and Difference (bottom) 50
Figure 3-19 Peak High Tide Water Level: Existing (top), Post 1 in 100 (1%) Flood
Condition (middle) and Difference (bottom) 51
Figure 3-20 Peak Flood Currents: Existing (top), 1987 East-West Aligned Entrance
Channel Condition (middle) and Difference (bottom) 53
Figure 3-21 Peak Ebb Currents: Existing (top), 1987 East-West Aligned Entrance Channel
(middle) and Difference (bottom) 54
Figure 3-22 Peak Flood Currents: Existing (top), Northeast-Southwest Aligned Entrance
Channel (middle) and Difference (bottom) 55
Figure 3-23 Peak Ebb Currents: Existing (top), 2010 Northeast-Southwest Aligned
Entrance Channel (middle) and Difference (bottom) 56
Figure 3-24 Peak Flood Currents: Existing (top), Dog Beach Breakthrough Condition
(middle) and Difference (bottom) 57
Figure 3-25 Peak Ebb Currents: Existing (top), Dog Beach Breakthrough Condition
(middle) and Difference (bottom) 58
Figure 3-26 Peak Flood Currents: Existing (top), Post 1 in 100 (1%) Flood Condition
(middle) and Difference (bottom) 59
Figure 3-27 Peak Ebb Currents: Existing (top), Post 1 in 100 (1%) Flood Condition
(middle) and Difference (bottom) 60
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Noosa Spit SEMP Final Report v
Contents
Figure 4-1 Example of a Trigger-Based Coastal Management Strategy (Barnes et al.
2017) 64
Figure 4-2 Option 1a: sand plug at either end of Dog Beach 76
Figure 4-3 Peak Flood Currents, Option 1a: sand plug at either end of Dog Beach 77
Figure 4-4 Peak Ebb Currents, Option 1a: sand plug at either end of Dog Beach 78
Figure 4-5 Option 1b: sand plug at southern end of Dog Beach 80
Figure 4-6 Peak Flood Currents, Option 1b: sand plug at southern end of Dog Beach 81
Figure 4-7 Peak Ebb Currents, Option 1b: sand plug at southern end of Dog Beach 82
Figure 4-8 Option 2: extension of the existing training wall at Dog Beach 84
Figure 4-9 Peak Flood Currents, Option 2: extension of existing groyne 85
Figure 4-10 Peak Ebb Currents, Option 2: extension of existing groyne 86
Figure 4-11 Option 3: extension of submerged breakwater and two new groynes 88
Figure 4-12 Peak Flood Currents, Option 3: extension of existing submerged breakwater
and two new groynes 89
Figure 4-13 Peak Ebb Currents, Option 3: extension of existing submerged breakwater
and two new groynes 90
Figure 4-14 Option 4: three new groynes 92
Figure 4-15 Peak Flood Currents, Option 4: three new groynes 93
Figure 4-16 Peak Ebb Currents, Option 4: three new groynes 94
Figure 4-17 Option 5: shore parallel seawall 96
Figure 5-1 Actions along the Risk Continuum (adapted from Fisk & Kay 2010) 98
Figure 5-2 Trigger Zones for Dog Beach Shoreline Management 101
List of Tables
Table 2-1 Summary of Noosa River Mouth Channel Position 7
Table 2-2 Noosa Spit Width Measurements 18
Table 4-1 Summary of Management Options and Option Type 64
Table 4-2 Rapid Assessment Criteria 66
Table 4-3 Rapid Assessment of Options Results 67
Table 4-4 MCA Categories, Weightings and Scoring Descriptors Developed with the
PCG 73
Table 4-5 Summary of MCA Results Developed with the PCG 74
Table 5-1 Key Stages and Triggers for Proposed Management Actions 100
Table 5-2 Approval Considerations for Shoreline Erosion Management Actions 102
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Noosa Spit SEMP Final Report 1
Introduction
1 Introduction
The lower Noosa River and river entrance are highly modified and dynamic environments influenced
by the prevailing fluvial and coastal processes. The observed trend of shoreline recession at the
north-facing beach of Noosa Spit, known locally as Dog or ‘Doggie’ Beach, is impacting the social
and recreational values attributed to the area. Importantly, this beach also forms part of an artificially
constructed river training/coastal defence strategy that protects property in Noosa Sound and the
back of Hastings Street.
Recently, erosion and shoreline recession has resulted in a narrowing of Noosa Spit. Consequently,
there is concern that the river may eventually break through Noosa Spit at Dog Beach, resulting
direct impact to the adjacent urban areas. Key locations referred to in this report are indicated in
Figure 1-1.
The Noosa Spit Shoreline Erosion Management Plan (SEMP) has been developed to quantify the
combined dynamics of the river entrance and Noosa Main Beach, investigate impacts of various river
mouth alignments, simulate the impacts of a breakthrough event, and propose erosion mitigation
options for Dog Beach.
This report describes:
• The analysis of recent shoreline trends (Chapter 2)
• Numerical modelling of the existing entrance and alternative entrance configurations (Chapter 3)
• Multi-Criteria Analysis of shoreline erosion mitigations options (Chapter 4)
• The preferred risk treatment strategy (Chapter 5)
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F ay Noosa River Mout! TRE, ge)24'March’2019, O/Nearmap, LEGEND Figure: 1-1 se BMT endeavours to ensure that the information provided in this WZ ty map is correct at the time of publication. BMT does not warrant, 05 a guarantee or make representations regarding the currency and % accuracy of information contained in this map —___ = uae Approx. Scale <a www.bmt. Filepath: _|:\823636.i. mpb.NoosaSpit_SEMP\DRG\COA_009_20190705_StudyArea.wor
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Noosa Spit SEMP Final Report 3
Noosa Spit Shoreline Erosion
2 Noosa Spit Shoreline Erosion
2.1 Introduction
The findings from an analysis of historical shoreline movements in the mouth of the Noosa River are
presented in this section, including:
• An update to the conceptual understanding of shoreline recession at The Spit and Dog Beach
based on recent observations;
• An evaluation of the current shoreline erosion management strategy;
• The estimated rate of shoreline recession at Dog Beach and the potential timeframe for a
breakthrough event if left untreated; and
• Identification of potential entrance configuration scenarios to be assessed with the numerical
modelling developed for the SEMP and presented in Chapter 3.
2.2 Previous Assessments
The Noosa Spit area was largely established by the construction of the Noosa River training wall,
starting in 1978. The historical movements of the channels and sand shoals in the mouth of the
Noosa River have previously been described by Tomlinson and Chamberlain (2006). That study
qualitatively considered aerial imagery captured between May 1972 and January 2002.
Migration of the river channels occurs in response to tidal flows and weather conditions, dominant
seasonal wind directions and catchment rainfall contributing to riverine flows. Tomlinson and
Chamberlain (2006) indicate that prior to the late 1960’s, the Noosa River channel entrance tended
to re-establish following storm or flood events in a “more direct south-eastern channel and migration
of the entrance to a more easterly position” (i.e. the approximate vicinity of Noosa Woods). Historical
imagery only captures the internal channels downstream of Munna Point running close to the
northern bank, although the lack of vegetation on the extensive sand shoals elsewhere in the river
mouth indicates highly mobile sand deposits.
The continual movement and re-establishment of the channel close to the centre of the historical
river mouth opening reflects the complexity of combined impacts of flood and tidal flows, along with
longshore sediment transport continually supplying sand to the area.
The formalisation of Hayes Island in the early 1970’s and the subsequent construction of the Noosa
River training wall in 1978 now restricts the channel to the northern half of the historical river mouth.
An assessment of erosion at The Spit was made by International Coastal Management (ICM) in 2010
(ICM 2010a). That assessment included observations of manual interference to restrict channel
movements, such as the placement of dredged sand to close the channel immediately adjacent to
the spit prior to 2005 (see Figure 2-1). It is unclear how frequently this dredging was undertaken, or
the source of the dredged sand.
In addition, several structures have been installed to mitigate erosion, including an extension of the
southern training wall, and two geofabric sand container structures (one submerged) at each end of
Dog Beach. These are described and considered further in Section 2.4.
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Noosa Spit SEMP Final Report 4
Noosa Spit Shoreline Erosion
Figure 2-1 Artificial Closure of River Channel, 2003 (ICM, 2010a)
2.3 Recent Observations
Since 2002, additional imagery covering the river mouth has been captured. A quantitative
assessment of channel and shoreline movements has therefore been undertaken on historical
imagery captured between 1978 and 2018 to better understand the drivers for shoreline changes at
Noosa Spit.
A mixture of Queensland Government (Beach Protection Authority) and Nearmap imagery has been
assessed for the following dates:
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Noosa Spit SEMP Final Report 5
Noosa Spit Shoreline Erosion
• 7 July 1982 • 11 August 2013
• 20 May 1986 • 17 June 2014
• 17 December 1990 • 2 September 2015
• 25 May 1994 • 22 September 2016
• 27 May 1996 • 17 February 2017
• 11 June 2004 • 8 December 2017
• 21 July 2010 • 9 September 2018
• 8 November 2011 • 24 March 2019
Figure 2-1 contains the imagery assessed, and summarises the observations recorded around Dog
Beach and the position of the entrance channels. Following on from Tomlinson and Chamberlain’s
(2006) historical descriptions of the evolution of the channels in the river mouth, additional details
are provided for photography captured from 21 July 2010 onwards.
It is important to note that manual interference has occurred within the assessment area. Two
separate nourishment campaigns/works implementation have been undertaken to reduce the
erosion impacts on Dog Beach in 2003 and in 2013. In addition, the sand shifter located immediately
south of the Noosa Woods training wall intercepts up to 40,000 m3 per annum on an as needs basis,
recycling the sand back onto Noosa Main Beach.
Assessment of the imagery concurs that flood events provide the primary mechanism for
reinstatement of a north-east to south-west running dominant channel. The creation of this channel
reduces flows in the southern channel immediately adjacent to Dog Beach.
Longshore transport of sediments along the outer beach to the northern and southern spits also plays
a role in the position of the channel at the mouth. A dominance of northerly and north-easterly winds
(and therefore waves) supplies sand from Teewah Beach towards the mouth, while the south-
easterly winds transfer sand along Noosa Main Beach towards the mouth. The sand supply to the
southern spit is sometimes interrupted by either the Noosa River training wall, or the activities of the
sand shifter operating in the area. Under easterly wind conditions, the spits are pushed westward
into the estuary, resulting in a channel that runs shore parallel (approximately north-south) within the
estuary before exiting to the ocean.
This spit growth process from sediment transport is supported by long-term wind data for the
Tewantin RSL and Double Island Point weather stations (operated by the BoM), which indicates that
north through to south-easterly wind conditions occur from August to December, while south to south-
easterly winds dominate from February to June. January and July are highly mixed as the wind
patterns fluctuate. Northerly winds dominate in spring.
In addition, the wave refraction processes at Noosa Headland (Noosa National Park) reduce the
influence of south-easterly waves impacting on Noosa Main Beach, increasing the influence on
sediment transport of waves from the north-north-east to north-east.
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Noosa Spit SEMP Final Report 6
Noosa Spit Shoreline Erosion
The continued effectiveness of a north-east to south-west running channel is affected by southward
growth of the northern spit. As the channel progressively shoals, the channel dominance switches to
the southern channel immediately next to Dog Beach. This is further assisted by the presence of two
“near permanent” scour pockets at each end of the southern channel (i.e. at the western end of the
Noosa River training wall and at the end of the Noosa Spit training wall at the western end of Dog
Beach).
Under easterly winds, the northern and southern spits at the river mouth are pushed westwards,
effectively holding the channel in a coastline parallel (approximately north-south) alignment which
tends to maintain the dominance of the southern channel (next to Dog Beach). This dominance is
then shifted by a storm event or flooding that causes one of the spits to be breached, thereby
increasing flows through one (or more) of the other channels. Whether the other channels then
become the dominant channel depends on the processes described above.
At Dog Beach, the southern channel could be expected to dominate particularly after:
• A sustained period of northerly to north-easterly winds (typically August to December); and/or
• A lack of river flooding to carve a new “east-west” oriented channel.
Dominance of the southern channel immediately adjacent to Dog Beach results in sustained erosion
pressure along the central to eastern end of the beach.
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Noosa Spit SEMP Final Report 7
Noosa Spit Shoreline Erosion
Table 2-1 Summary of Noosa River Mouth Channel Position
Imagery Observed Changes Wind Climate Notable Orientation Northern Spit Southern Spit Dominant Flow High Tide High Tide
Date (since previous image) Compared to Average Rainfall and Condition Length and Length and Channel Recreational Recreational
(since previous (since of Mouth Condition Condition Beach Beach
image) previous Availability at Availability at
image) central Doggie eastern
Beach Doggie Beach
July 1982 Paraphrased from Tomlinson and Chamberlain (2006): Double Island Point: Data not N-S Short above Average and Northern, but Limited (fronted Limited (fronted
SE dominant over available HWM, long wide above multiple by shoals) by shoals)
Southern spit and ebb-tidal delta enlarged due to Main Beach nourishment.
preceding years submerged HWM, long channels
Channel in a similar position and shape to previously observed but the entrance
shoals to south submerged through shoals,
has migrated further north due to growth of southern spit and ebb-tidal delta. Tewantin:
shoals to north shoals adjacent
Northern spit eroded as a result of this migration. Northern channel is the Equal NE & SE, less S
to Doggie
dominant flow path but the southern channel may be re-opening. than average
Beach
May 1986 Paraphrased from Tomlinson and Chamberlain (2006): Double Island Point: Data not Shore-parallel Average, Short above Central, but None (fronted None (fronted
SE dominates, more E available west of narrow, HWM, long multiple by shoals) by shoals)
Several interceding years of photography were considered. The southern
Autumn 1983, more N coastline, then submerged submerged channels
channel reopened. A period of vacillation between opening and closing of the
Summer 1984 than N-S shoals to south shoals to north- through shoals,
southern channel occurred while sand was being supplied into the channel from
average west shoals adjacent
Noosa Woods (ocean) beach. While open the channel cut back slightly into
to Doggie
Noosa Woods. At the same time, the northern spit grew and the entrance Tewantin:
Beach
migrated southward. Eventually the southern channel increased in dominance Equal NE & SE, more E
as the major flow path. During this period, the orientation of the entrance in 1983, less S than
changed from north to east and back to north. average
December Paraphrased from Tomlinson and Chamberlain (2006): Double Island Point: Data not Shore-parallel Average, Minimal above Southern – None Wide (infilled
1990 SE dominates, less SE available west of narrow, HWM, average Hard up against shoals)
Several interceding years of photography were considered. The northern
in 1987, less N to NE in coastline, then submerged submerged Doggie Beach
channel breached the northern spit and became the dominant flow path while
Spring 1989 & 1990 NE-SW shoals to south shoals to north-
the material that previously formed the southern spit blocked the southern flow
than average west
path. The southern channel progressively re-established, resulting in both
channels operating simultaneously, sharing a single exit with two well developed Tewantin:
spits. The northern channel was progressively infilling. Equal NE & SE, less N
in 1990 than average
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Noosa Spit SEMP Final Report 8
Noosa Spit Shoreline Erosion
Imagery Observed Changes Wind Climate Notable Orientation Northern Spit Southern Spit Dominant Flow High Tide High Tide
Date (since previous image) Compared to Average Rainfall and Condition Length and Length and Channel Recreational Recreational
(since previous (since of Mouth Condition Condition Beach Beach
image) previous Availability at Availability at
image) central Doggie eastern
Beach Doggie Beach
May 1994 Paraphrased from Tomlinson and Chamberlain (2006): No wind data available Data not N-S Average, wide, Minimal above Central, but Limited to none Wide (infilled
for 1992 to 1995 available submerged HWM, long multiple shoals)
The southern channel was the dominant flow path and continued to cut back
shoals to south submerged channels
into Noosa Woods until a new central channel was cut as a result of increased Double Island Point: Known events:
and west shoals to north- through shoals
river flows due to cyclones Betsy, and Fran in January and March 1992, SE dominates, less S in TC Betsy
west shallow
respectively, and ex-TC Daman in February 1992. This new channel removed 1991 than average Ex-TC Daman
adjacent to
the southern spit. The three channels continued to operate, with the southern TC Fran
Tewantin: Doggie Beach
and central channels progressively infilling, although the central channel
1991 typical year
retained dominance over the northern channel. An apparent lack of longshore
transport supply stagnated spit growth for a time. Continued growth of the
northern and southern spits forced the middle channel to realign to the north.
May 1996 Not reviewed by Tomlinson and Chamberlain (2006). No wind data available Higher than Shore-parallel Average, wide, Short above Multiple Limited Average
for 1992 to 1995 average: west of submerged HWM, average channels
Consolidation of the northern Spit to the flood tide delta continued, with the
May 1996 coastline, then shoals to south submerged through shoals,
gradual infilling and southward migration of the central and southern channels Double Island Point:
NE-SW shoals to north- shallow
towards Noosa Spit. The southern channel continued dominate and to cut back Autumn 1996 more N
west adjacent to
into Noosa Woods. than average
Doggie Beach
Growth of the southern spit continued, forcing the channel to adopt a shore- Tewantin:
parallel alignment before exiting to the north-east. Less E in 1996 than
average
June 2004 Paraphrased from Tomlinson and Chamberlain (2006) to 2002, updated to 2004: Double Island Point: Significantly Shore-parallel Short, wide, Minimal above Central, Varies, limited to Wide
Spring 1998 and 1999 higher than west of submerged HWM, average backwater wide
The river entrance maintained its characteristic location, exiting in a north-
less N to NE than average (and coastline, then shoals to south- submerged adjacent to
easterly direction midway between the training wall and the north shore. The
average highest monthly NE-SW west shoals to north- eastern Doggie
central channel progressively merged with the southern channel, and the
totals on west Beach
northern channel reopened, progressively increasing in size over time. The Tewantin:
record):
southern channel continued to cut into Noosa Woods. More S in 1997 and SE
February, May
in 1998 than average
High rainfall in the first half of 1999 contributed to formation of a new central to July 1999
channel. This led to progressive closure of the northern channel as the northern
spit grew and merged with the flood tide delta, and the central channel migrated
southwards to become the new southern channel.
The southern spit continued to grow, holding the southern channel close to
Noosa Woods, where the upstream end of the training wall quickly generated
additional scour. This contributed to dominance of the southern channel.
In 2003 an unknown quantity of nourishment was placed at either end of a
section of the southern channel (refer Figure 3-18) to reduce erosion on Doggie
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Imagery Observed Changes Wind Climate Notable Orientation Northern Spit Southern Spit Dominant Flow High Tide High Tide
Date (since previous image) Compared to Average Rainfall and Condition Length and Length and Channel Recreational Recreational
(since previous (since of Mouth Condition Condition Beach Beach
image) previous Availability at Availability at
image) central Doggie eastern
Beach Doggie Beach
Beach. This progressively evolved into a lagoon as the continued sand supply
to the southern spit forced the channel westward away from the training wall.
July 2010 During the period from 2004 to 2010 there is a lack of regular imagery available Double Island Point: Significantly N-S up to open Average, wide, Minimal above Multiple Average Limited to none
for review, so it is not possible to describe the evolution of the channels with 2009 more N than higher than coast submerged HWM, average channels
confidence. average average (and alignment, then shoals to west submerged through shoals
highest monthly NE-SW shoals to north-
It is presumed that following the 2003 nourishment, the southern channel Tewantin:
totals on west
resumed southward migration. In August 2007, a new central channel was most More NE consistently
record):
likely formed in response to the heavy rainfall associated with the East Coast from 2005 to 2009 than
January 2006,
Low. average
August &
The continued supply of sand to the northern spit has infilled and eventually September
blocked the northern channel, which has split into two. The central and southern 2007,
channels have shared dominance. Notable recession of Noosa Woods at the November 2008
upstream end of the training wall is evident. and April 2009.
Known East
Coast Low in
August 2007.
November Gradual consolidation of the northern spit continued, with patchy dune grass Double Island Point: Significantly Multiple Average, wide, Minimal above Central, but Limited to none Average
2011 colonisation evident. Overall less N than higher than disconnected N- submerged HWM, minimal multiple (pre-groyne)
average, but Spring average: S and NE-SW shoals to west submerged channels
The central channel appears to be slightly more defined and the southern spit
2011 more N than October & channels shoals to north- through shoals
has mostly disappeared. This is possibly in response to significant rainfall
average December west
inflows reinforcing the existing channel and carving a more direct exit channel
2010, April 2011
close to the training wall. The scour pocket at the upstream end of the Noosa Tewantin:
Woods training wall has persisted, encouraging the retention of the southern 2011 less NE than
channel. average
Localised beach nourishment equipment and small sand bulges are visible
along the eastern end of Doggie Beach. Notable beach narrowing and loss of
established vegetation continues to occur at the western end of Doggie Beach.
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Imagery Observed Changes Wind Climate Notable Orientation Northern Spit Southern Spit Dominant Flow High Tide High Tide
Date (since previous image) Compared to Average Rainfall and Condition Length and Length and Channel Recreational Recreational
(since previous (since of Mouth Condition Condition Beach Beach
image) previous Availability at Availability at
image) central Doggie eastern
Beach Doggie Beach
August Major manual interference in the southern channel and along Doggie Beach Double Island Point: Significantly Multiple Average, wide, Non-existent Central, but Wide (post- Wide (post-
2013 occurred in the lead up to this image. A training wall was constructed at the Typical winds higher than disconnected patchy multiple groyne, groyne,
western end of Noosa Spit to control channel migration and limit further erosion average: NE-SW overwash, channels nourished) nourished)
Tewantin:
of Doggie Beach, accompanied by nourishment along the length of the beach. December channels submerged through shoals
Typical winds
Manual infilling of the channel near the submerged geobag groyne at the eastern 2011, January shoals to west
end of Doggie Beach is visible. Nourishment material was sourced from the 2012, March
shoals near the new training wall. The dredge holes created in this process 2012, June
appear to have naturally re-filled. 2012, January
2013 (ex-TC
Very little change was observed in the central channel, which is dominant now
Oswald),
that the southern channel has been partially infilled. The exit channel has
February 2013,
remained close to the Noosa Woods training wall, assisted by the training wall
July 2013
scour pocket, and reduced sediment supply from Noosa Main Beach due to
sand shifter activities between February and May 2013 (approx. 30,000 m3).
Sediment supply to the northern spit appears to have reduced, and localised
breaching of the northern spit at higher water levels is evident.
June 2014 Very gradual increase in length and height of northern spit sand mass, with the Double Island Point: Nil. Dryer than Multiple Average, wide, Non-existent Central, but Average Average
spit blocking flow of the northern channel. Visible increase in dune grass Typical winds average. 2014 disconnected N- submerged multiple
colonisation. close to lowest S channels shoals to west channels
Tewantin:
rainfall on through shoals
The central channel remains dominant, although some shoaling is occurring just Typical winds
station record.
upstream of its intersection with the southern channel, forcing development of a
currently short section of new channel aligned to N-S. The channel exit remains
close to the Noosa Woods training wall, although minor development of the
southern spit has occurred.
The southern channel has remained largely stable, although redistribution of the
nourishment material placed in the southern channel has exposed the upper
layer of the submerged geobag groyne. The scour pocket at the end of the
Noosa Spit training wall has become well developed.
September Consolidation of the northern spit continued, with easterly winds expanding the Double Island Point: Nil. Dryer than Poorly defined Average, wide, Minimal above Multiple Average Average
2015 spit to the west, almost connecting with Frying Pan Island above the high-water Spring 2014 more E average. Ex-TC N-S channels submerged HWM, minimal channels
mark. This spit growth was assisted by further dune grass stabilisation. The than average Marcia in area shoals to west submerged through shoals
northern channel largely remains a backwater. Shoaling of the eastern end of February 2015, shoals to north-
Tewantin:
the central channel has progressed to a stage where the channel, although heavy rainfall west
Typical winds
dominant, is no longer continuous through the flood-tide delta. recorded for
one day only.
Further exposure of the submerged geobag groyne has occurred, with the entire
length of the structure now visible. The scour pockets at the ends of both training
walls (i.e. at each end of the southern channel) are well developed.
Gradual narrowing of Doggie Beach above the high-water mark has occurred,
although no further loss of vegetation is evident.
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Imagery Observed Changes Wind Climate Notable Orientation Northern Spit Southern Spit Dominant Flow High Tide High Tide
Date (since previous image) Compared to Average Rainfall and Condition Length and Length and Channel Recreational Recreational
(since previous (since of Mouth Condition Condition Beach Beach
image) previous Availability at Availability at
image) central Doggie eastern
Beach Doggie Beach
September Growth of the northern spit appears to have reversed, with the spit narrowing Double Island Point: Nil. Dryer than Multiple N-S Average, wide, Short, Multiple Limited Average
2016 and adopting a more westward N-S alignment. There is no change in the Summer 2015/16 average. 2016 channels submerged submerged channels
development of the northern channel. stronger SE than lowest rainfall shoals to west through shoals
average, & Winter 2016 on station and south
The southern and central channels have fragmented across the flood-tide delta,
lighter N than average record
developing multiple disconnected channels. Dual N-S channels have developed
through the ebb-tide delta, one connecting to the southern channels and another Tewantin:
running along the seaward face of the northern spit. Typical winds
Minor narrowing of the centre of Doggie Beach is visible, but no loss of
vegetation is apparent.
There is limited change in development of the southern spit, with approximately
12,500m3 intercepted by the sand shifter.
February Southward growth of the northern spit has resumed, further blocking the central Double Island Point: Nil. Dryer than Shore-parallel Long, wide, Minimal above Multiple Limited to none Average
2017 channel and forcing the remaining fragmented channels to consolidate Summer 2016/17 more average. west of western side HWM, average channels
southwards. Increased inundation of dune grasses on the western face of the N-NE than average coastline, then partially submerged through shoals
northern spit indicates potential for breaching. N-S submerged shoals to north-
Tewantin:
west
Vegetation loss along central Doggie Beach has resumed as the southern Typical winds
channel migrates southward against Noosa Spit. The submerged geobag
groyne has been partially covered with sand from the adjacent sand shoal.
Although the scour pocket at the Noosa Woods training wall still controls flows,
the southern channel no longer exits alongside the training wall, instead running
in a shore-parallel direction before exiting closer to Noosa North Shore. The
southern spit extent remains small above high-water, although the submerged
portion has notably increased as the channel exit moves north away from the
training wall.
December While vegetation on the northern spit continued to establish, the spit itself does Double Island Point: Wetter than Shore-parallel Average, wide Minimal above Southern – Limited to none Limited
2017 not appear to change significantly, and inundation of the spit along the upstream Typical winds average. west of but patchy HWM, average Hard up against
(western) face of the spit appears to be increasing, with overtopping visible coastline, then overwash submerged Doggie Beach
Tewantin: Highest March
where the split northern channel re-joins. The central channel continues to be NE-SW shoals to north-
Typical winds rainfall on
blocked by the spit. west
station record
Southward merging of the multiple channels between the northern spit and (ex-TC Debbie).
Doggie Beach is complete, with the southern channel now the sole channel. Significant
Notable loss of vegetation along Doggie Beach is a direct result of the proximity rainfall in
of this dominant channel. October and
November.
The southern spit has grown notably below the high-water mark, despite more
than 8,000 m3 of material being intercepted by the sand shifter in the preceding
month. The spit growth has forced the channel towards the northern spit before
exiting near Noosa North Shore.
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Noosa Spit Shoreline Erosion
Imagery Observed Changes Wind Climate Notable Orientation Northern Spit Southern Spit Dominant Flow High Tide High Tide
Date (since previous image) Compared to Average Rainfall and Condition Length and Length and Channel Recreational Recreational
(since previous (since of Mouth Condition Condition Beach Beach
image) previous Availability at Availability at
image) central Doggie eastern
Beach Doggie Beach
September Continued expansion of the southern spit has forced the exit channel westward, Double Island Point: Wetter than Shore-parallel Short and Short and wide Southern – Limited to none Average
2018 scouring out the northern spit and facilitating a breach of the northern spit by the Less N to E winds than average but no west of narrow above above HWM, Hard up against
southern arm of a split northern channel, and by the central channel. The typical, SE dominant notable rainfall. coastline, then HWM, extensive Doggie Beach
northern arm of the northern channel is still narrowly blocked by the northern NE-SW extensive submerged
Tewantin:
spit, which is now significantly shortened but connected to Frying Pan Island submerged shoals to north-
Typical winds
below high-water mark. shoals to south west
The severed southern portion of the northern spit has migrated south, partially
infilling the central channel and consolidating with the sand shoal separating the
central and southern channels. The southern channel remains the dominant
channel, persisting hard up against Doggie Beach before heading northwards
towards Noosa North Shore where channel migration has undermined
established vegetation.
The northern spit has continued to expand to the northwest, and is now well
developed above the high-water mark, even though nearly 9,000 m3 was
intercepted by the sand shifter.
March TC Oma affected the area in February 2019, with increased wave action but no Double Island Point: 2018 Highest Shore-parallel Short above Short above Southern – Limited to none Limited
2019 rainfall. While erosion of Noosa Main Beach was observed, the complex wave Less N to E winds than October rainfall west of HWM, minimal HWM, average Hard up against
breaking processes over the ebb-tide delta would have limited the passage of typical, SE dominant on station coastline, then submerged submerged Doggie Beach,
large waves through the mouth. record, NE-SW shoals shoals to NW but multiple
Tewantin:
Significant channels
The northern channel has now completely broken through the northern spit close Typical winds
rainfall through shoals
to Noosa North Shore. The severed portion of the spit has migrated westward
November
to join onto Frying Pan Island.
2018.
The central and southern channels are both operational, with the southern
channel remaining dominant and largely unchanged, anchored firmly by the
scour points at the end of the training walls. The eastern end of the central
channel appears more well-defined than in previous imagery.
Growth of the southern spit stagnated but appeared to migrate slightly westward.
Nearly 19,000 m3 was recycled by the sand shifter, including pumping
undertaken immediately before and after TC Oma.
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2.4 Current Shoreline Erosion Strategy
The current erosion management strategy at Dog Beach consists of several elements originally
proposed by ICM (2010a) and illustrated in Figure 2-2. Construction of Stage 1 of the strategy was
completed in 2013, and consisted of:
• A training wall comprised of geofabric sand containers and rock seawall at the western end of
Dog Beach;
• A partially submerged breakwater constructed with geofabric sand containers at the eastern end
of Dog Beach; and
• Beach nourishment and sand deposition in the southern channel (associated with construction of
the structures).
The training wall and seawall have fixed the position of the western end of The Spit, and the training
wall has acted as a groyne to intercept sediments carried upstream on the flood tide. Since
construction works were undertaken, the western most 140 m of the beach has progressively
accreted immediately east of the training wall. A large and near-permanently deep scour hole to
approximately -9 mAHD has formed at the north-western tip of the structure, which also acts as a
control point for the southern channel. However, in the centre of Dog Beach, southward channel
migration has continued relatively unimpeded. It is noted that the scour depth is 3.1 m below the
founding level indicated on the design drawings (ICM, 2010b) and may ultimately lead to a slumping
failure of the structure1.
At the eastern end of the channel, the submerged breakwater was largely buried by sand following
construction, but since late 2017 is clearly fully visible in aerial imagery, and a scour pocket to -7
mAHD has developed on the northern side of the groyne. This scour depth is 1.2 m below the
founding level of the submerged breakwater indicated on the design drawings (ICM, 2010b) and has
caused slumping, with the breakwater crest also approximately 1 m below the design level. This
observation would suggest that the structure is not performing as intended. Aside from minor
localised changes around the time of construction in the immediate vicinity of the main beach access
point, there has been minimal change in shoreline position since 2011.
While Stage 1 of the shoreline strategy appears to have been successful in stabilising the shoreline
at the eastern and western ends of Dog Beach, it must be noted that the period from construction
(2013) to 2017 coincided with non-dominance of the southern channel. Since the southern channel
reasserted dominance in 2017, the nourishment material has been lost from the beach and erosion
of established vegetation is now re-occurring (refer Figure 2-3).
1
A structural integrity assessment of the training wall has not been undertaken as part of the SEMP.
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Figure 2-2 ICM (2010a) Proposed Ultimate Strategy (top); Stage 1 Works Completed in
2013 (bottom)
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LEGEND Hes Vegetation line Dog Beach Shoreline, Pre- and Post-Strategy Implementation 2017 Figure: 2-3 2013 BMT endeavours to ensure that the information provided in this sre 4 map is correct at the time of publication. BMT does not warrant, Waas> s a) 2011 guarantee or make representations regarding the currency and _ yy accuracy of information contained in this map "APPIOX. SCTE Nd www.bmt.org Filepath: 1:\B23636.i.mpb.NoosaSpit_SEMP\DRG\COA_003_20190405_Vegetation_Doggie_Beach.WOR
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Noosa Spit SEMP Final Report 16
Noosa Spit Shoreline Erosion
Stage 1 of the shoreline strategy is considered to have been partially successful in stabilising Noosa
Spit. The remaining stages of the shoreline erosion management strategy involve an extension of
the partially submerged groyne and the installation of two smaller conventional groynes.
While these elements may ultimately assist in successfully retaining a beach, it is considered that:
• The founding levels of the various structures will need to incorporate the potential for undermining
from the southern channel (i.e. they may need to be significantly deeper and therefore larger and
more expensive structures than originally intended); and
• Ongoing exposure to flows in the southern channel would be expected to generate scour points
at the structures (like those already observed), causing artificial deepening of the channel, and
possibly encouraging natural retention or re-establishment of the southern channel in this
location.
2.4.1 Recent Shoreline Recession
Shoreline recession at Dog Beach is not occurring linearly and is dependent on the continued
dominance of the southern channel. In addition, The Spit has changed shape and orientation over
time, and artificial nourishment of the beach and within the flow channels have influenced beach
width.
The assessment of shoreline changes seeks to clarify the understanding of:
• Erosion of The Spit, particularly in relation to width and vulnerability to breakthrough; and
• Availability of a beach for recreational use.
2.4.1.1 Movement of vegetated shoreline
To provide a reliable assessment of shoreline movements along Dog Beach, measurements of
vegetation lines relative to a fixed location or ‘baseline’ at Hayes Island (now known as Noosa Sound)
have been made. In addition, the narrowest part of The Spit has been measured. Note that although
this location varied slightly from year to year, it was consistently in the same vicinity.
Measurement locations are shown in Figure 2-4, and actual measurements are reported in Table
2-2. The monitoring lines used in this project have deliberately not been established perpendicular
to the shoreline as The Spit has been slowly changing shape over time – a line perpendicular to the
2019 shoreline is not perpendicular to the shorelines from the 1980’s and 1990’s. The lines have
therefore been established on a north-south orientation and linked to readily identifiable landmarks.
This also reduces confusion for future measurements and supports a rapid and simple assessment
of future changes.
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Title: Shoreline Recession Measurement Locations Filepath: §|:\B23636.impb.NoosaSpit_SEMP\DRG\COA_002_20190405_Vegetation_Change. WOR Approx. Scale 1 LEGEND @ Point Oo Southern point Oo Baseline point Measurement line Figure: 2-4 We CS ‘eZ BMT www.bmt.org
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Noosa Spit SEMP Final Report 18
Noosa Spit Shoreline Erosion
Table 2-2 Noosa Spit Width Measurements
Width (m)
Narrowest
Year Point 1 Point 2
Point 3 Point 4 part
(western (central
(central east) (eastern end) (between
end) west)
points 3 & 4)
1982 128 118 66 163 57
1986 170 129 68 174 67
1990 161 177 219 191 89
1994 252 166 210 187 81
1996 245 162 208 186 83
2004 194 163 212 211 87
2010 96 140 189 141 72
2011 82 133 185 140 62
2013 58 138 182 113 60
2014 59 134 178 122 64
2015 61 139 181 134 61
2016 63 136 176 120 65
2017 48 136 181 129 62
2017 47 129 181 114 65
2018 52 129 178 117 63
2019 48 128 178 114 64
The Spit width measurements indicate that recession is most evident towards the western end.
Localised narrowing observed at Point 1 is largely attributed to end scour from the training wall and
rock wall on the southern side of The Spit. Recession appears to occur sporadically and is most likely
associated with the occurrence of strong river currents during spring tide periods.
Of more concern is the recession observed at Point 2. Figure 2-5 shows the spit width at each
measuring location since Stage 1 of the shoreline strategy was implemented, along with the
associated trend line (dotted) for each location. The measurements confirm that while the southern
channel was not dominant (i.e. prior to 2017), the shoreline was relatively stable. However, since the
southern channel became dominant, recession at this location has recommenced. If the southern
channel remains the dominant channel over the next ten years, recession at Point 2 in the order of
20 m could be expected.
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Figure 2-5 Noosa Spit Width (m)
To provide context for the implications of this recession, in the March 2019 image the vegetated spit
width at Point 2 is 128 m and of this, approximately 50 m is typically terrestrial (i.e. above highest
astronomical tide), while the remaining 78 m is mangrove and salt-marsh species routinely inundated
by higher tides or river flows. Recession of 20 m in this location would nearly halve the terrestrial spit
width, and further increase vulnerability to breakthrough under storm tide or flood conditions.
Shoreline movements observed at Point 4 are associated with localised changes due to
implementation of the Stage 1 shoreline strategy works.
2.4.1.2 Available Recreational Beach Width
The available recreational beach (i.e. above the high-water mark) on the northern side of The Spit
was at its widest following nourishment associated with the construction of the training wall (western
end) and submerged breakwater (eastern end) in 2013. At all other times, the available beach at high
tide has varied from around 10 m wide to no beach at all.
Figure 2-6 shows the variability of the width at Dog Beach between the vegetation line and the
indicative high-water mark at each monitoring line. These approximate distances are reported
perpendicular to the beach. Points with symbols indicate that the access to the available beach
was also affected by fallen trees.
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Figure 2-6 Dog Beach Recreational Beach Width
The 2004 imagery (refer Table 2-1) shows a wide recreational beach towards the eastern end of the
embayment associated with the progressive attachment of a sand shoal to the beach. Figure 2-1
(2003) suggests that this process was influenced by the placement of sand within the channel to
deflect flows away from Dog Beach and The Spit. At the time of the photo capture, the upstream
attachment point of the shoal was in the vicinity of Point 2, hence a wide recreational beach was
observed at that location.
Further east, the recreational beach was narrower but fronted by a lagoon, while to the west, the
channel persisted close to shore and no notable increase in recreational beach width was observed.
By 2006, the shoal had completely dispersed, and the channel had returned to its previous position
hard up against Dog Beach.
The impact of the 2013 nourishment campaign and training wall construction on recreational beach
width is obvious. Following the immediate shoreline adjustment after the nourishment works had
been completed, the Noosa Spit (western) training wall has continued to hold the western end of the
beach largely in place, however the presence of the scour hole at the northern tip of the training wall
appears to be progressively influencing the shape of the beach immediately downstream. At present
this impact is localised and only affects the beach within approximately 40 m of the training wall.
Since 2017 the remainder of Dog Beach has largely returned to its condition before Stage 1 of the
shoreline strategy.
2.4.1.3 Boat Wake
The entrance to the Noosa River is not maintained for navigational purposes. As such, the ‘preferred’
channels used by recreational and commercial vessels varies in response to the entrance and shoal
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morphology. Since at least late 2016 (and during other earlier periods), the Dog Beach channel has
provided a commonly used route for safe navigation.
Vessels displace water and as they move generate a wake (wash) wave train. In rivers these small
waves propagate and will often reach a shoreline where the bulk of the remaining energy is
dissipated. The characteristics of the wake waves depended on several factors relating to vessel
operation and hull design, displacement, trim, loading, speed, method of propulsion, course and rate
of change in course (e.g. WRL 2014). The impact of wake waves that reach the shoreline is also
dependent on the shoreline type and its susceptibility to erode.
The influence of vessel activity on shoreline recession at Dog Beach has not been quantified as part
of the SEMP and is assumed to be a secondary influence in comparison to the broader estuarine
processes. However, it is likely that boat wake waves will exacerbate the erosion, particularly on
sections of shoreline that are relatively steep and already receding due to channel migration. The
boat wake waves will have less of an impact on the wider sandy sections of shoreline where the
energy is dissipated over a larger area.
Although a secondary influence and difficult to quantify, it’s reasonable to assume that boat wake
contributes to erosion at Dog Beach when the adjacent channel is being used by vessels. This
contributor to shoreline erosion is essentially removed when the navigable channels are in other
locations. This also provides the added benefit of increasing the distance between powerboat activity
and other recreational uses of Dog Beach such as swimming, canoeing/kayaking, paddle boarding
and fishing.
2.5 Potential Entrance Configurations for Further Assessment
To explore how different entrance conditions influence the rate of shoreline recession at Dog Beach
and lower river hydrodynamics, the following scenarios are suggested for further assessment with
the numerical modelling tools developed for the SEMP:
• An east-west aligned channel in the centre of the embayment, such as that observed in 1986/87
(Figure 2-7, left panel)
• A northeast-southwest aligned channel in the centre of the embayment, such as that observed
(Figure 2-7, right panel).
Testing the other historical scenarios and comparing them to the present condition provides a basis
for understanding the potential ‘benefit’ of alternative channel and/or entrance configurations with
respect to reducing the erosion pressure at Dog Beach. Re-establishing or ‘encouraging’ a channel
to remain in a particular location or alignment via carefully planned and designed works (such as
dredging, beach nourishment and/or structures) is likely to form part of the strategy for mitigating
erosion at Dog Beach. The initial assessment of these and other lower river conditions is described
in Chapter 3 and strategies to relive the erosion pressure at Dog Beach are presented and assessed
in Chapter 4.
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Figure 2-7 Historical Entrance Configuration Scenarios for Further Assessment: East-west
Aligned Channel (left) and Northeast-Southeast Aligned Channel
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Numerical Modelling of Entrance Configurations
3 Numerical Modelling of Entrance Configurations
3.1 Background
The numerical modelling described in this Chapter follows the analysis of recent shoreline trends
described above and a data collection campaign completed in March/April 2019. Technical
summaries of the metocean and bathymetric data collection campaigns are provided with this report:
• Appendix A: Metocean Data Collection
• Appendix B: Bathymetric Survey (Acoustic Imagery, 2019).
The Model is comprised of several numerical components that simulate coastal and estuarine
processes and can be used in uncoupled or coupled modes. Key elements and an initial application
of The Model to assess various river entrance configurations are described below.
3.2 Waves (SWAN)
SWAN (Delft University of Technology, 2006) is a third-generation spectral wave model, which
simulates wave growth by wind and wave energy dissipation by whitecapping, depth-induced wave
breaking and bottom friction. SWAN simulates wave/swell propagation in two-dimensions, including
shoaling and refraction due to spatial variations in bathymetry and currents. This is a global industry
standard modelling package that has been applied to many investigations worldwide.
In this study SWAN is used to transform measured directional wave data from the Mooloolaba
Waverider Buoy into shallow water within Laguna Bay. Validation of the modelling approach using
directional wave data from an Acoustic Doppler Current Profiler (ADCP) deployed in Laguna Bay
and is presented in Section 3.5.2.
3.2.1 Nested Model Domain & Bathymetry
A nested wave modelling system has been established to investigate the wave climate within Laguna
Bay. The model extent and wave data recording locations are shown in Figure 3-1. The modelling
system includes a 400 m resolution regional model and two nests of increasing resolution to 25 m to
resolve waves within Laguna Bay.
Bathymetry for the wave model has been derived from the following sources in descending priority:
• Acoustic Imaging high-resolution (0.5 m) survey captured in March 2019 (see Appendix B).
• SKM 2 m Digital Elevation Model (DEM) created from a 2011 bathymetric LiDAR survey of the
Sunshine Coast (Queensland Government 2012).
• High-resolution depth model for the Great Barrier Reef (Geoscience Australia 2017).
3.2.2 Model Configuration
The wave modelling has used a two-dimensional (2D), nonstationary configuration of SWAN the
following configurations and parameterisations:
• Third-generation with default settings; and
• Bottom friction described by Collins (1972) with default coefficient.
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3.2.3 Boundary Conditions
The model is forced by swell wave parameters derived from the Mooloolaba Waverider buoy and
deep-water wave transformation and applied to the offshore boundary of the 400 m resolution grid.
Wind wave development was simulated using a spatially and temporally varying wind field. The wind
boundary condition was derived from the NOAA CFSR and CFSv2 global model datasets (Saha et
al. 2010; 2014). A temporally varying water level (informed by Mooloolaba tide gauge recordings)
was applied to the 25 m nest to capture the potential for depth-limited wave conditions within Laguna
Bay.
3.3 Hydrodynamics (TUFLOW FV)
The hydrodynamic modelling component has been undertaken using the TUFLOW FV software,
which is developed and distributed by BMT (https://www.tuflow.com/Tuflow%20FV.aspx). TUFLOW
FV is a numerical model for the 2D and three-dimensional (3D) Non-Linear Shallow Water Equations
(NLSWE). The model is suitable for solving a wide range of hydrodynamic systems ranging in scale
from open channels and floodplains, through estuaries to coasts and oceans.
The Finite-Volume (FV) numerical scheme employed by TUFLOW FV can solve the NLSWE on both
structured rectilinear grids and unstructured meshes comprised of triangular and quadrilateral
elements. The flexible mesh allows for seamless boundary fitting along complex coastlines or open
channels as well as accurately and efficiently representing complex bathymetries with a minimum
number of computational elements. The flexible mesh capability is particularly efficient at resolving
a range of scales in a single model without requiring multiple domain nesting.
3.3.1 Model Domain, Mesh & Bathymetry
The model domain is shown in Figure 3-2 and extends from Double Island Point in the north to Point
Cartwright (Mooloolaba) in the south and includes the tidal extent of the Noosa River. The model
mesh is comprised of 44,632 elements with resolution at the offshore boundary approximately 2 km
(mesh cell side length), increasing to 20 m in the nearshore coastal and estuarine areas. It is noted
that higher resolution can be easily added to the model at specific areas of interest and has been
applied to some areas when neatly resolve specific management actions described in Chapter 4.
Figure 3-3 shows detail of the model mesh at Noosa Spit with the high-resolution bathymetry survey
captured by Acoustic Imaging. The hydrodynamic model bathymetry relies on the same bathymetry
datasets listed in Section 3.2.1.
3.3.2 Model Configuration
The hydrodynamic modelling described in this report has used a 2D configuration of TUFLOW FV.
The model has used the following configurations and parameterisations:
• Smagorinsky model to estimate horizontal turbulent and sub-grid mixing;
• Bottom drag derived from application of the ‘log-law’; and
• Bottom roughness length-scales between 0.05-0.5 m, with the lower limit used for sandy areas
and the upper limit used for mangrove areas.
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3.3.3 Boundary Conditions
Tidal water level variation recorded at the Mooloolaba gauge has been used to inform the offshore
water level boundary condition. The model calibration process included testing temporal offsets
applied to the water level timeseries to account for the tidal phase difference between Mooloolaba
and the offshore boundary (estimated to be 20 min). A minor amplitude adjustment (~5 %) was also
applied between the Mooloolaba water level and Double Island Point, based on the published tidal
planes for the region (MSQ 2019).
The wind boundary condition derived from the NOAA CFSR and CFSv2 global datasets described
in Section 3.2.3 was also applied to the hydrodynamic model.
Wave boundary conditions derived from the SWAN models can be used to provide secondary forcing
to the hydrodynamic model. These are applied as spatially and temporally varying wave fields that
are then interpolated onto the TUFLOW FV flexible mesh. This is discussed further in Section 3.4.
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Elevation (m) 2.0 LEGEND Model Mesh © 2019 Microsoft Corporation Earthstar Geographics SIO Figure: 3-2 if BMT endeavours to ensure that the information provided in this See map is correct at the time of publication. BMT does not warrant, 75 i¢ _ guarantee or make representations regarding the currency and ee i! accuracy of information contained in this map. / oP B MT Approx. Scale www.bmt.org
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PET 6 ecm LEGEND Model Mesh || ee BMT endeavours to ensure that the information provided in this map is correct at the time of publication. BMT does not warrant, 100 guarantee or make representations regarding the currency and accuracy of information contained in this map. Approx. Scale Filepath: |:\B23636.i.mpb.NoosaSpit_SEMP\DRG\COA_008_20190704_TFV_detail. wor wan Ve vy : jaljimage24} March*2 otc www.bmt.org
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3.4 Sediment Transport (TRANSPOR)
Modelling of sediment transport has been used as part of establishing the various entrance and
channel configurations considered as part of the SEMP.
The TRANSPOR model (van Rijn 2004) has been used to predict sediment transport within TUFLOW
FV. The TRANSPOR model represents multiple fraction sediment transport including wave- and
current-related bedload and suspended load dynamics. The calculated bedload component is a
direct input to the TUFLOW FV morphological bed update scheme, while the suspended load
component is converted to an equivalent sediment pickup rate (Nielsen 1992), which provides a
suspended sediment source term to the TUFLOW FV water column advection-dispersion scheme
(and corresponding sink term to the bed). Suspended sediment settling provides a sink term to the
water column (and corresponding source term to the bed).
TRANSPOR represents the interaction of both current- and wave-related sediment transport. The
presence of waves can enhance sediment pickup and therefore also the rate of transport by the local
currents. TRANSPOR also includes the prediction of wave-related sediment transport due to
processes such as wave velocity skewness and wave boundary layer streaming. These (and other)
processes can generate a net transport in the direction of (or against) wave travel, even in the
absence of a local current.
A single sand fraction with median grain size D50 = 0.22 mm will be assumed for sediment transport
modelling assessments. The internal routines in TRANSPOR are then used to calculate bed
roughness values based on sediment and hydrodynamic parameters. All other parameters have
adopted the default values described in van Rijn et al. (2004).
3.5 Numerical Model Calibration & Validation
3.5.1 Targeted Data Collection
Bathymetric survey and metocean data collection were undertaken to support development of The
Model, including:
• High-resolution bathymetric survey of the lower Noosa River and nearshore coastal areas in
March and April 2019. This work was completed by Acoustic Imaging and is described in
Appendix B.
• The deployment of six tide recorders in the lower Noosa River to continuously measure water
level for approximately six weeks. This data was used to calibrate the hydrodynamic model and
provides some valuable information to partially address concerns regarding the published tidal
planes.
• Offshore fixed deployment Acoustic Doppler Current Profiler (ADCP) to continuously measure
water level, current speed, current direction and wave parameters (height, period and direction).
This data was used to calibrate both the hydrodynamic and wave models.
• Boat-mounted ADCP measurements have been collected during both neap and spring tidal
conditions. The measurements (from approximately low water to low water) were taken at Dog
Beach, Noosa Sound, Munna Point and Noosaville. This data was used to calibrate the
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hydrodynamic model and understand the peak flood and ebb tide currents occurring at Dog
Beach.
Indicative locations where data has been obtained are shown in Figure 3-4 and a summary of the
data collection campaign is provided in Appendix A. Subsets of these datasets are used in the
followed sections to illustrate the predictive skill of The Model.
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LEGEND Offshore ADCP @ = In-situ Water Level Recorders O In-situ Barometric Pressure Recorders e=eee Approximate ADCP Cross Section Locatio Instrument Locations BMT endeavours to ensure that the information provided in this map is correct at the time of publication. BMT does not warrant, guarantee or make representations regarding the currency and accuracy of information contained in this map Filepath: _|:\823636.i. mpb.NoosaSpit_SEMP\DRG\COA_001_Equipment_locations.wor Figure: 3-4 sie “a ‘eZ BMT www.bmt.org 0.5 Approx. Scale
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3.5.2 Laguna Bay Waves
The following wave parameter datasets were available for wave model development and calibration
(locations indicated in Figure 3-1):
• Mooloolaba Waverider Buoy operated by the Queensland Department of Environment and
Science (DES). The instrument is permanently installed in a depth of approximately 32 m; and
• Bottom-mounted ADCP within Laguna Bay. The temporary installation was in a depth of
approximately 9.5 m between 10/03/2019 and 30/04/2019.
Each dataset provides continuous recordings of significant wave height (Hs or Hsig), wave peak
period (Tp) and wave direction.
The model predictive skill for the ADCP deployment period is illustrated in Figure 3-5. The model
reproduces the recorded wave parameters well, noting the following trends:
• A tendency to slightly underpredict significant wave height peaks at the wave buoy and ADCP
locations;
• Accurate prediction of wave peak period at the wave buoy and ADCP locations; and
• A slight under prediction of refraction at Noosa Headland and wave direction at the ADCP
location.
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Figure 3-5 Wave Timeseries Calibration: Mooloolaba Buoy (left) and Laguna Bay (right)
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3.5.3 Laguna Bay Water Level & Currents
The bottom-mounted ADCP temporarily installed within Laguna Bay also recorded water level,
current speed (magnitude) and current direction. Hydrodynamic model calibration results to these
datasets are shown in Figure 3-6 and indicate the following trends:
• The water level within Laguna Bay is accurately represented by the model during neap and spring
tide conditions.
• The magnitude and direction of tidal currents are modelled in a general sense however the data
shows significantly more scatter than the model. This is likely due to a combination of the
following:
○ The influence of wind on the water column not being precisely represented by the model. For
example, the CFSR wind field applied as a boundary condition will not accurately resolve the
local orographic effects associated with the Noosa Headland;
○ The influence of wave radiation stress on the current patterns; and/or
○ Vertical gradients in the water column not represented by the 2D modelling approach.
3.5.4 Noosa River Water Level
Within the Noosa River, the model has been calibrated to the six tide recording locations indicated
in Figure 3-4. Tidal water level comparisons, covering a period that includes neap and spring tides,
are provided in Figure 3-7 and Figure 3-8. These figures illustrate that the phase and amplitude of
the tide is predicted well at each location, noting a tendency to slightly overpredict high tide at the
river mouth (Tide Recorder 1). The recordings and model output also show the attenuated tidal
conditions within the lower river compared to Laguna Bay (top panel of Figure 3-6).
It is noted that Tide Recorder 2 (middle panel of Figure 3-7) appeared to have been moved on
retrieval of the instrument. The raw data suggested that this occurred during the first week of
deployment. Data recorded before this time has been discarded.
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Figure 3-6 Laguna Bay Water Level, Current Speed and Current Direction Timeseries
Calibration
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Figure 3-7 Lower Noosa River Water Level Timeseries Calibration: Tide Recorder 1 (top),
Tide Recorder 2 (middle) and Tide Recorder 3 (bottom)
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Figure 3-8 Lower Noosa River Water Level Timeseries Calibration: Tide Recorder 4 (top),
Tide Recorder 5 (middle) and Tide Recorder 6 (bottom)
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3.5.5 Noosa River Flow
A boat-mounted ADCP was used to measure velocity profiles while the boat traverses a section of
the river (typically a cross-section). The total flow through the transect is calculated by integrating the
velocity profile data vertically from the bottom-most to the top-most bin and horizontally/temporally
across each transect. This provides ‘instantaneous’ flow measurements that can be used to calibrate
the hydrodynamic model. ADCP transects were obtained at the following locations (indicated in
Figure 3-4):
• Neap tide cross-sectional transects at Dog Beach, Noosa Sound, Munna Point and Noosaville on
14 March 2019.
• Spring tide cross-sectional transects at Dog Beach, Noosa Sound, Munna Point and Noosaville
on 20 March 2019.
• Spring tide cross-sectional transects at Dog Beach on 21 March 20192.
The tidal flow calibration results are shown in Figure 3-9 and indicate the following (positive/negative
flow indicates flood/ebb tide conditions in the lower river):
• The peak ebb and flood flow conditions at Dog Beach are predicted accurately during the neap
and spring tide periods.
• Tidal flow at the Noosa Sound transect location is accurately represented by the model.
• Tidal flow at the Munna Point transect location is accurately represented by the model, noting that
the peak flood flow during the spring tide period was not perfectly captured during the data
collection campaign.
• Tidal flow at the Noosaville transect location is accurately represented by the model. This is
considered a key model calibration location since the data represents a ‘complete’ cross-sectional
flow measurement (as opposed to only measuring a portion of the instantaneous river flow at the
other transect locations).
Snapshots of the measured and modelled currents at Dog Beach during the peak flood and ebb
conditions are also shown in Figure 3-10.
2
Long-sectional transects were also obtained on this date but have not used for flow calibration purposes. The long-sectional data will
be used to investigate the peak current conditions occurring at Dog Beach.
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Figure 3-9 Noosa River Flow Timeseries Calibration at Dog Beach, Noosa Sound, Munna
Point and Noosaville
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Figure 3-10 Instantaneous Measured and Modelled Current Speed during Peak Flood (top)
and Ebb (bottom) Conditions
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3.6 Entrance Configuration Assessment
The Model has been used to investigate historical and conceptual river entrance configuration and
the relationship with erosion potential at Dog Beach and lower river water levels under normal tidal
conditions. In addition to the ‘existing’ (2019) case the following scenarios were considered:
• 1986/87 ‘east-west’ aligned entrance channel condition, informed by historical aerial imagery.
• 2010 ‘northeast-southwest’ aligned entrance channel condition, informed by historical aerial
imagery and bathymetric survey data provided by Council.
• Dog Beach breakthrough entrance condition, hypothetical breakthrough to Noosa Sound.
• Post 1 in 100 (1%) Annual Exceedance Probability (AEP) river flood entrance condition, input
design river flow conditions informed by the Noosa River Flood Study (WMA Water, 2017).
The model representations of these bathymetric/morphological conditions are shown in
The testing of each scenario involved the following steps:
(3) Update of the model bathymetry using the bathymetric representation of the entrance
configuration of interest. In the case of the flood event, this involved simulating the
morphological response to the design river flow with the 2019 bathymetry used to define the
model ‘initial condition’.
(4) One-month simulation of sediment transport and morphology under typical tidal conditions.
This allows the modelled bed to ‘warm-up’.
(5) Simulation of ‘normal’ spring and neap tidal conditions to understand the system response to
the morphological change.
The key findings are presented below and have been summarised using maps that illustrate the
‘impact’ (or difference) relative to the entrance condition in March/April 2019.
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3.6.1 Impact to Water Level
Maps showing the impact to peak water level are shown in Figure 3-16 to Figure 3-19 and indicate
the following:
• The comparison between the existing peak high tide water level and 1987 scenario (Figure 3-16)
and 2010 scenario (Figure 3-17) show only minor differences beyond the entrance and within the
lower river. This suggests that the tidal prism and tidal attenuation is relatively insensitive to the
entrance channel configuration.
• The Dog Beach breakthrough scenario (Figure 3-18) causes high tide water levels within Noosa
Sound and the lower river to increase by up to 0.08 m. This morphological change increases the
tidal prism and reduces the freeboard for waterfront locations.
• Following the 1 in 100 (1%) AEP flood event and associated scour, the cross-sectional area at
the entrance and tidal prism increases. This causes lower river high tide water levels to increase
by up to 0.1 m. It is noted that the ‘post flood’ condition is temporary, and the entrance cross-
sectional area would gradually return to it’s equilibrium conditions under the prevailing conditions.
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Figure 3-16 Peak High Tide Water Level: Existing (top), 1987 East-West Aligned Channel
Entrance Condition (middle) and Difference (bottom)
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Figure 3-17 Peak High Tide Water Level: Existing (top), 2010 Northeast-Southwest Aligned
Entrance Channel Condition (middle) and Difference (bottom)
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Figure 3-18 Peak High Tide Water Level: Existing (top), Dog Beach Breakthrough Condition
(middle) and Difference (bottom)
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Figure 3-19 Peak High Tide Water Level: Existing (top), Post 1 in 100 (1%) Flood Condition
(middle) and Difference (bottom)
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3.6.2 Impact to Current Magnitude at Dog Beach
Maps showing the impact to peak tidal current magnitude are shown in Figure 3-20 to Figure 3-27
and indicate the following:
• Comparison between the existing and 1987 entrance condition suggest significantly reduced
erosion pressure at Dog Beach in 1987. During this period the Dog Beach channel was shoaled
and the dominant flow channel was central during peak flood tide conditions (Figure 3-20) and to
the north during peak ebb tide conditions (Figure 3-21).
• The erosion pressure at the western extent of Dog Beach was greater in 2010 compared to the
existing condition, particularly during peak flood tide conditions (Figure 3-22). This area has since
been stabilised by the geofabric sand container training wall constructed in 2013. The existing
peak ebb tide currents through the middle section of the Dog Beach channel are greater in
magnitude compared to 2010 (Figure 3-23). This demonstrates the ongoing dominance of the
Dog Beach channel and implies that the works completed in 2013 are only reducing erosion
pressure along a limited section of shoreline, updrift of the training wall during the flood phase of
the tide.
• The breakthrough condition leads to greater current magnitudes at the eastern end of Dog Beach
during both flood (Figure 3-24) and ebb (Figure 3-25) tide phases. The distribution of currents
suggests the potential for rapid morphological change at the Spit following a breakthrough event.
The Noosa Woods area would be expected to narrow overtime and lead to further loss of coastal
land that protects Noosa Sound and Hasting Street.
• Following a major flood event, the erosion pressure at Dog Beach associated with tidal currents
is reduced in comparison to the existing condition (Figure 3-26 and Figure 3-27). Scour during
the river flooding creates a dominant central channel and reduces flow throughout the Dog Beach
channel during flood and ebb tide phases.
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Figure 3-20 Peak Flood Currents: Existing (top), 1987 East-West Aligned Entrance Channel
Condition (middle) and Difference (bottom)
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Figure 3-21 Peak Ebb Currents: Existing (top), 1987 East-West Aligned Entrance Channel
(middle) and Difference (bottom)
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Figure 3-22 Peak Flood Currents: Existing (top), Northeast-Southwest Aligned Entrance
Channel (middle) and Difference (bottom)
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Figure 3-23 Peak Ebb Currents: Existing (top), 2010 Northeast-Southwest Aligned Entrance
Channel (middle) and Difference (bottom)
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Figure 3-24 Peak Flood Currents: Existing (top), Dog Beach Breakthrough Condition
(middle) and Difference (bottom)
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Figure 3-25 Peak Ebb Currents: Existing (top), Dog Beach Breakthrough Condition (middle)
and Difference (bottom)
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Figure 3-26 Peak Flood Currents: Existing (top), Post 1 in 100 (1%) Flood Condition (middle)
and Difference (bottom)
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Figure 3-27 Peak Ebb Currents: Existing (top), Post 1 in 100 (1%) Flood Condition (middle)
and Difference (bottom)
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3.6.3 Assessment Summary
The river entrance is an important controlling factor on the tidal regime in the estuary with the shoals
and sand bars causing attenuation of the ocean tidal amplitude. Stable tidal channels, unless
otherwise geologically restricted or subject to strong external influences such as input of sediments
by other processes or a fluvial flood, have been shown to exhibit a well-defined relationship between
the volume of tidal flow (tidal prism) and the cross-sectional area of the flow; a consequence of
needing to adjust their geometry until a certain equilibrium is achieved. The assessment of the 1987,
2010 and existing entrance channel and shoal configurations has shown that tidal water levels within
the estuary are relatively insensitive to the entrance condition when the ‘dynamic equilibrium’
condition exists.
The equilibrium tidal regime is disrupted after a significant flood and/or Dog Beach breakthrough
event. These scenarios cause an increase to the cross-sectional area of the flow, tidal prism and
peak high tide levels in the lower river. It is noted that the prevailing sediment transport processes
would be expected to gradually infill the scour associated with post-flood condition and return the
entrance to the dynamic equilibrium condition. The morphological response following a breakthrough
event at Dog Beach is less predictable; however, the impact to the estuary tidal regime is likely to be
permanent and potentially worsen if there was further of loss of land that attenuates the ocean tidal
amplitude before it reaches existing development at Noosa Sound and at the back of Hastings Street.
The current patterns vary significantly with entrance condition. The current magnitude and shoreline
erosion potential along the middle section of the Dog Beach channel is greater in 2019 compared to
the other historical conditions assessed. In terms of shoreline stabilisation, the works completed in
2013 have only benefited the western end of Dog Beach. The lowest current magnitude and shoreline
erosion potential at Dog Beach is when the entrance channel is aligned east-west (i.e. the 1987
condition) and peak tidal flows are directed away from The Spit.
The distribution of currents following a breakthrough event suggests the potential for ongoing
morphological change at The Spit and further loss of coastal land and open space that shelters
existing development.
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4 Shoreline Erosion Mitigation Options
4.1 Introduction
An initial rapid assessment of shoreline erosion management options was completed to inform the
Noosa Spit SEMP. This work followed:
• Conceptual options proposed by Council’s Project Control Group (PCG) (refer Attachment 1); and
• A meeting with Sel Sultmann from the Department of Environment and Science (DES) held on
Friday 2 August 2019. The conceptual options proposed by the PCG were discussed in the
context of gaining approval for the proposed works.
The shortlisted options were then considered in detail following a Multi-Criteria Analysis process and
further engagement with the PCG. Where appropriate, The Model has been used to test the
effectiveness of the shortlisted options.
This Chapter presents the analysis of shoreline erosion managements options and justification for
the preferred strategy.
4.2 Overview of Generic Options
Management options presented here focus on reducing the rate of shoreline erosion at Dog Beach
and to avoid a breakthrough of the Noosa Spit which provides sheltering to existing development.
Coastal management options broadly fall within the categories of avoid, accommodate, accept for
future development; and protect, accommodate, retreat for existing assets and development.
For future development, the management approaches are:
• Avoid the risk, by not permitting vulnerable developments in high risk areas (over the design life
of the development);
• Accommodate the risk by including provisions that reduce consequence of impacts (foundations,
floor levels, etc.); and
• Accept the risk where appropriate to the level of risk over the design life of the development.
Planned development should generally adopt these principles to avoid creating new coastal
management issues for Council.
Existing assets and development are harder to manage as the value (e.g. open space) or built
assets (e.g. urban area) are already in place, as is the case for the Noosa Spit and adjacent areas it
protects. Options for management of existing assets include the following approaches:
• Protect existing assets on the ground, whether important habitat, open space or development.
Protection can be in the form of a hard structure or soft engineering measure, and can have offsite
impacts;
• Retreat is the ‘no defence’ approach that aims to preserve beach amenity by allowing natural
recession of the shoreline. Retreat can involve relocating or sacrificing the asset when impacts
occur; and
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• Accommodate the risk aims to retrofit (or redevelop) existing infrastructure and development in
a manner that minimising damage and other losses. May also include existing shoreline
management activities.
For the risks posed to existing assets and development, it’s often useful to define ‘trigger points’ for
implementation of promoted management options. This is especially true when the risk to assets is
uncertain and expected to change over time. The trigger-based approach acknowledges uncertainty
in natural coastal processes (such as rapid events that cause shoreline erosion or storm tide
inundation) and the success of management actions. It is underpinned by ongoing monitoring and
performance criteria to identify changes in risk profile which trigger actions to achieve an overarching
coastal management objective.
This conceptual approach is illustrated in Figure 4-1 for a shoreline with an overarching management
objective to maintain a sandy beach that provides a buffer to coastal processes and social values.
Beach nourishment is the preferred management action to achieve the objective in this example;
however, it is recognised that this action alone may not sufficiently treat the risk or be viable over a
longer-term planning period. The strategy includes a trigger for a seawall once the risk to land-based
assets can no longer be treated by beach nourishment.
Prior to the seawall trigger being reached, planning controls, ‘no regrets’ actions and preliminary
investigations must still be undertaken to plan for the investment in future actions. No regrets and
preliminary actions are typically low cost with little or no undesirable consequences. In some cases,
these actions simply represent ‘business as usual’ for Council and/or investigations needed to
support the design and implementation of the promoted management options.
Table 4-1 lists the management options considered to address the potential coastal hazard risks at
Dog Beach and Noosa Spit. The broad options were initially considered through engagement with
the PCG and DES followed by the application of the ‘rapid assessment’ presented below in Section
4.2.1. It is noted that an effective coastal management strategy for Noosa Spit is likely to require a
combination of options over time.
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Figure 4-1 Example of a Trigger-Based Coastal Management Strategy (Barnes et al. 2017)
Table 4-1 Summary of Management Options and Option Type
Management Option Option Type
Monitoring No Regrets / Preliminary Action
Detailed Beach Erosion Hazard Study No Regrets / Preliminary Action
Investigate Protection Funding Sources and Arrangements No Regrets / Preliminary Action
Community Education and Consultation No Regrets / Preliminary Action
Dune and Habitat Management No Regrets / Preliminary Action
Beach Access Management No Regrets / Preliminary Action
Accept Impacts (Do Nothing) Planned Retreat
Partial Land Acquisition Planned Retreat
Buy Back / Lease Back Planned Retreat
Full Implementation of Strategy Proposed by Sunshine Coast
Protect
Council
Existing Groyne Extension at Southern River Mouth Protect
New Groyne at Northern River Mouth Protect
Seawall Along Dog Beach Protect
Groyne Field Along Dog Beach Protect
Extension of Existing Control Structures Protect
Beach Nourishment / Sand Relocation Program Protect
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4.2.1 Rapid Assessment of Options
There are a variety of measures and tools available to manage persistent coastal erosion issues. A
rapid assessment of potential options for Noosa Spit was undertaken with the intention of identifying
the short-listed or ‘promoted management options’ for further consideration. This qualitative
assessment was based on the criteria summarised in Table 4-2 with the options and rapid
assessment results summarised in Table 4-3.
A ‘traffic light’ colour system was used to assess the option against each criterion, as either:
• GO;
• SLOW, and proceed with caution; or
• STOP.
The criteria used were not weighted, meaning that each has an equal influence on the overall score
for each option assessed. Options with a positive overall were shortlisted and then subjected to a
more detailed analysis which is presented in Section 4.3.
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Table 4-2 Rapid Assessment Criteria
Environmental Reversible /
Capital Recurrent Community Effectiveness Legal / Approval Technical
or Social Adaptable
Costs Costs Acceptability Over Time Risk Viability
Impact Future
Unlikely to be Is unlikely to be
Will require an EIS
acceptable to Option is technically viable
and/or Govt program to
Will impact community and irreversible once Option does not without
Very Very implement;
negatively on politically unpalatable; implemented; provide long term substantial
expensive expensive There is a residual risk
STOP environment, Extensive community Option limits solution; engineering (or
($500K to ($500K to community or that approval will not be other) design
education, alternatives Only effective over
millions) millions) beach amenity obtainable for the investigation and
endorsement by options in the short term
proposed works / capabilities for
Minister(s) and future
strategy implementation
Council required
Will require Govt
Option is only a
approvals to be
Would be palatable to short term solution, Is likely to be
implemented, or
some, not others Option is but has other technically viable
Moderately Moderately assistance through
(~50/50 response); reversible or benefits; or at the site, but
expensive expensive existing Govt program;
SLOW ($100,000 - ($50,000 -
No net impact Briefing to adaptable, but at Option requires would require
considerable Generally further
$500,000) $500,000) Councillors, GM and further resources /
cost / effort approvals/assistance investigations to
community education changes to be
would be granted clarify
required effective over long
assuming requirements
term
are met
Option can be
Will benefit easily adapted
environment, Is very politically for future
community or palatable, acceptable circumstances or
No or minimal Is technically
Limited cost Limited cost beach amenity to community; should impacts Option provides a
GO (<$100,000) (<$50,000) (e.g. improve not occur, option long term solution
government approvals viable at the site /
Minimal education required to implement location
beach access, would not
recreation, required negatively
habitats etc.) impact future
generations
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Table 4-3 Rapid Assessment of Options Results
Community Acceptability
Planning & Consultation
Environmental or Social
Score (Go = 1, Slow = 0,
Effectiveness over time
Reversible / Adaptable
Legal / Approval Risk
Treats Erosion Issue
Maintains Foreshore
Technical Viability
Recommended
Inundation Issue
Maintains Beach
Recurrent Costs
Treats Oceanic
Option Option Type Asset Type &/or
Capital Cost
Other Comments
Stop = -1)
Amenity
Habitat
Impact
No Regrets / Preliminary Actions
Monitor beach condition, scarp
location and recession rates to
G G G G G G G G Beach and embankment
Monitoring determine when risk approaches ✓ o o o o o o o o 8 scarp location.
unacceptable levels and
management triggers are reached.
Recently completed as
Detailed Beach Undertake detailed hazard part of the current study
G G G G G G G G
Erosion Hazard assessment that identifies site ✓ o o o o o o o o 8 and should be reviewed
Studies specific setback erosion distances. and updated as new
data becomes available.
Joint funding may be
required to fund some
Investigate Joint Investigate a range of potential joint
protection options that
funding arrangements to treat G G G G G G G G
Funding coastal hazard risks (state ✓ o o o o o o o o 8 are prohibitively
Arrangements expensive for Council
government, private landholder etc.).
alone and/or directly
benefit freehold land.
Build acceptance and resilience for Suitable for residents
Community coastal risk management in the and wider community.
community by providing ongoing G G G G G G G G Could be delivered in
Education and information regarding coastal ✓ o o o o o o o o 8 conjunction with CHAP
Consultation hazards, risks, monitoring and communication
implementation of actions. activities.
Continue to implement and support Continue to manage and
Dune and Habitat G G G G G G G G
dune care/habitat management ✓ ✓ ✓ 8 encourage revegetation
Management programs
o o o o o o o o
of Noosa Spit.
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Community Acceptability
Planning & Consultation
Environmental or Social
Score (Go = 1, Slow = 0,
Effectiveness over time
Reversible / Adaptable
Legal / Approval Risk
Treats Erosion Issue
Maintains Foreshore
Technical Viability
Recommended
Inundation Issue
Maintains Beach
Recurrent Costs
Treats Oceanic
Option Option Type Asset Type &/or
Capital Cost
Other Comments
Stop = -1)
Amenity
Habitat
Impact
Remove unnecessary or informal
Beach Access access; formalise appropriate public G G G G G G G G
✓ ✓ 8 Whole of Noosa Spit.
Management paths; conduct inspection and o o o o o o o o
repairs to access after erosion.
Planned Retreat Options
Accept loss of land or assets
affected by a hazard event (i.e. once
S S S S S Unlikely to be suitable
affected, the assets or land is not
Accept Impacts G G l l t l l G considering the
replaced). Allows Dog Beach to ✓ 2
(Do Nothing) recede without intervention,
o o o o o o o o sheltering to existing
w w p w w development.
potentially leading to a
breakthrough.
Partial acquisition of freehold land to S S S S S Not likely to be viable
Partial Land accommodate coastal management t G G t l G t t considering the value of
✓ ✓ -1
Acquisition options and/or be designated as o o o o o o o o potentially vulnerable
public land. p p w p p freehold land.
Not currently viable. If
High risk private properties are
the option of retreat is to
bought at market prices, and then
S S S S S be considered broadly
rented out until hazard impacts are
Buy Back / Lease t G G t l G t t as part of the CHAP and
imminent (years). When hazard is ✓ ✓ -1
Back imminent, the property is
o o o o o o o o long term adaptation
p p w p p planning, this option
demolished and land returned to the
could be further
public.
investigated.
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Community Acceptability
Planning & Consultation
Environmental or Social
Score (Go = 1, Slow = 0,
Effectiveness over time
Reversible / Adaptable
Legal / Approval Risk
Treats Erosion Issue
Maintains Foreshore
Technical Viability
Recommended
Inundation Issue
Maintains Beach
Recurrent Costs
Treats Oceanic
Option Option Type Asset Type &/or
Capital Cost
Other Comments
Stop = -1)
Amenity
Habitat
Impact
Protect - Regional Management Options
Stage 1 of the strategy was The Stage 1 training wall
Full implemented and included is performing as
construction of the training wall at
Implementation the western end of Dog Beach and S S S S S S S
intended however the
submerged structure
of Strategy submerged structure. t t l l l l l G
✓ 1/2 ✓ -1 has been damaged by
Proposed by o o o o o o o o
propeller strike and is
Stage 2 of the strategy involves a p p w w w w w
Sunshine Coast significant extension of the slumping. Scour is
Council submerged structure and addition of evident at both
two small groynes. structures.
The existing groyne
allows sand bypassing
and development of the
Extend existing structure to intercept southern spit (north of
Existing Groyne sand and reduce bypassing of the S S S S S S S Dog Beach) which
Extension at groyne into the river mouth. t t l l t t l G
1/2 -3 influences the entrance
Southern River o o o o o o o o channel alignment.
This option would potentially benefit p p w w p p w
Mouth operation of the sand shifter. Uncertainty whether a
reduced rate of
bypassing would benefit
Dog Beach.
The new structure is
intended to intercept
sand and reduce
S S S S S S S S development of the
New Groyne at New structure to intercept sand and northern spit which
t t l l t t t l
Northern side of reduce season transport into the 1/2
o o o o o o o o -5 influences the entrance
River Mouth river mouth from North Shore channel alignment.
p p w w p p p w
Uncertainty whether
these works would
benefit Dog Beach.
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Treats Oceanic Inundation
Maintains Beach Amenity
Community Acceptability
Planning & Consultation
Environmental or Social
Score (Go = 1, Slow = 0,
Effectiveness over time
Reversible / Adaptable
Legal / Approval Risk
Maintains Foreshore
Recommended
Technical Viability
Recurrent Costs
Option Option Type Asset Type &/or
Treats Erosion
Other Comments
Capital Cost
Stop = -1)
Habitat
Impact
Protect - Local Management Options
High certainty of
S S S S S S protection of land. Likely
Extend rock revetment seawall
Seawall Along t l l l t G l G loss of social and
protection to protect land from ✓ 1/2 1/2 2
Dog Beach erosion.
o o o o o o o o recreational values
p w w w p w associated with Dog
Beach.
S Potential challenges
S S S S S S
Construct field of short groynes t associated with scour at
Groyne Field l l l l G l l
along Dog Beach to deflect currents ✓ 1/2 ✓ ✓ o 0 the head of the
Along Dog Beach and stabilise the shoreline. p
o o o o o o o
relatively small
w w w w w w
structures.
Extension of training wall to the S S S S S S
Extension of t Potential impact to
south of Dog Beach and/or rock l l l l G l G
Existing Control revetment to the north of Dog Beach
✓ 1/2 ✓ ✓ o o o o o o o o 1 navigation will need to
Structures p be managed.
to divert channel flow. w w w w w
Nourishment of shoreline and/or
infilling of channels to offset erosion Ongoing commitment
Beach and maintain/improve beach S S S S S S required.
Nourishment / amenity. l l l G G l l l
✓ ✓ ✓ 2 Potential impact to
Sand Relocation o o o o o o o o
navigation will need to
Sand potentially accessed from spit w w w w w w
Program to the north of Dog Beach or shoals be managed.
to the west of Dog Beach.
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4.2.1.1 Rapid Assessment Results
The following options considered likely to gain agency support with a positive score following the
rapid assessment include:
• No Regrets / Preliminary Actions:
○ Ongoing monitoring of shoreline position, scarp location and recession rates so that triggers
for escalating the management strategy can be identified
○ Review and update erosion hazard studies (such as this SEMP) and recommended strategies
every 5 to 10 years.
○ Investigate joint funding arrangements to implement the preferred strategy
○ Provide the community with information regarding coastal hazards, risks, monitoring and
strategy implementation
○ Support dune care/shoreline habitat management programs
○ Seek to avoid unnecessary or informal beach access that may cause damage to shoreline
habitat by maintaining public access points.
• Planned Retreat Options:
○ Allowing Dog Beach to recede without intervention, potentially leading to a breakthrough. It is
noted that the reputational, political and legal risks associated with this option may be
unacceptable.
• Protect – Local Management Options:
○ Seawall along the entire length of Dog Beach to protect land-based assets and avoid a
breakthrough
○ Construct a field of short groynes to deflect currents and stabilise the shoreline
○ Extend the existing training wall at the western end of Dog Beach to provide benefit to a longer
section of the updrift shoreline
○ Nourish the shoreline and/or infill the Dog Beach channel to offset erosion and improve beach
amenity.
The following sections describe the detailed analysis of the shortlisted options. As noted above, the
outcomes of the SEMP and rapid assessment of options should be reviewed and updated every 5 to
10 years in response to changes to physical environment, new information gained through monitoring
and/or community expectations.
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4.3 Multi-Criteria Analysis
A Multi-Criteria Analysis (MCA) of the shortlisted options has been developed in consultation with
the PCG. Table 4-4 provides a summary of the MCA categories, weightings and scoring descriptors.
Building on the outcomes of the rapid assessment and consultation with the PCG and DES, the
following options were defined:
• Option 1a – Sand plug at either end of Dog Beach and shoreline nourishment
• Option 1b – Sand plug at the southern end of Dog Beach and shoreline nourishment
• Option 2 – Extension of the existing training wall/groyne at western end of Dog Beach
• Option 3 – Extension of submerged breakwater and two new groynes (full implementation of the
strategy proposed by Sunshine Coast Council and summarised in Section 2.4)
• Option 4 – Three new groynes at Dog Beach
• Option 5 – Shore parallel seawall
• Option 6 – Do nothing (allow Dog Beach to recede without intervention).
Discussion on the MCA category scoring and assumptions for each option is presented in the
following sections. The general approach for scoring within each MCA category is:
• Effectiveness: Option 1 (a and b) to Option 4 were assessed using The Model with impacts
quantified by comparing the ‘existing’ and ‘developed’ case scenarios. These outputs are used to
infer areas where sand deposition, erosion and morphological change may occur in response to
the option. Option 5 and Option 6 were not assessed with The Model and therefore the scoring is
based on qualitative assumptions.
• Whole of life costs (annualised) to 2040: Assumptions based on Council’s experience with
similar works at Dog Beach and other lower Noosa River locations. Industry advice from dredging
contractors has also been incorporated to the cost estimates for Option 1a and Option 1b.
• Environmental values: Qualitative assumptions based on the potential for temporary impact (i.e.
during construction) or permanent loss terrestrial and/or estuarine habitat.
• Social values: Qualitative assumptions based on the available beach and land areas available
for recreation.
• Risk: In accordance with Council’s corporate risk assessment procedure (full details in Appendix
D).
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Table 4-4 MCA Categories, Weightings and Scoring Descriptors Developed with the PCG
Category Weighting Highly Desirable (100%) Desirable (75%) Neutral (50%) Undesirable (25%) Highly Undesirable (0%)
Solution provides highly Solution provides effective Solution provides effective Solution provides limited Solution provides limited
effective reduction in erosion at reduction in erosion at Noosa reduction in erosion at Noosa reduction in erosion at Noosa reduction in erosion at Noosa
Noosa Spit for the duration of Spit for the duration of the Spit for the duration of the Spit for the duration of the Spit for the duration of the
the planning period, is highly planning period, is somewhat planning period but may not be planning period and may not be planning period, is not
Effectiveness 30% adaptable to future conditions adaptable to future conditions adaptable to future conditions adaptable to future conditions adaptable to future conditions
and there are no adverse and there are no adverse and there are no adverse and/or there are very minor and/or there are adverse
impacts to any other land impacts to any other land impacts to any other land adverse impacts to any other impacts to any other land
parcels. parcels. parcels. land parcels. parcels.
Whole of Life Costs ($ / 20 years) 20% Less than $1,500,000 Less than $2,500,000 Less than $3,500,000 Less than $4,500,000 Greater than $4,500,000
There is a high impact to local
There is minor impact to local There is moderate impact to There is a high impact to
Surrounding environmental environmental values or
environmental values in the local environmental values in broader environmnetal values,
values are undisrupted and moderate, broad impact in the
short-term but long term the short-term but long term causing significant disrupuption
improved. Including improved short-term but long term
values are improved. Including values are improved. Including or long term reduction. There
Environmental Values 15% fish habitat, improved flora values are maintained.
improved fish habitat or no negative impact on fish is long term impact on fish
habitat and no impact on Including short term impact on
improved flora habitat and no habitat, flora habitat, migratory habitat, flora habitat, migratory
migratory shorebird or benthic fish habitat, flora habitat,
impact on migratory shorebird shorebird habitat or benthic shorebird habitat or benthic
habitat. migratory shorebird habitat or
or benthic habitat. habitat. habitat.
benthic habitat.
Social values are significantly
improved. Including providing a
Social values are intermitently Social values are maintained. Social values are reduced.
usable all-tide beach, Social values are improved.
improved. An all-tide beach is Current narrow beach condition Current narrow beach condition
reestablishemnt of bush walking Including providing a usable all-
generally maintained, while is maintained, while is maintained or reduced, while
tracks, seperation of swimming tide beach while maintaining
Social Benefits 10% maintaining current boat maintaining current boat current boat passage capability
and boat traffic zones while current boat passage
passage capability. Visual passage capability. Visual is maintained or reduced.
maintaining current boat capability. Visual amentiry of
amentiry of the beach is amentiry of the beach is Visual amentiry of the beach is
passage capability. the beach is improved.
maintained. maintained. reduced.
Visual amentiry of the beach is
improved.
Average risk rating no more Average risk rating no more than Average risk rating is no more Average Risk score is High or
Average risk rating is Low,
Risk 25% than Low and/or highest risk Medium and/or highest risk than Medium and/or highest Extreme and/or the highest
highest risk score is Low.
score is no more than Medium. score is no more than Medium. risk score is no more than High. individual score is Extreme.
Total 100%
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Table 4-5 Summary of MCA Results Developed with the PCG
Effectiveness Whole of Life Environmental Social Benefits Risk
Costs Values Overall Score
(30% weighting) (20% weighting) (15% weighting) (10% weighting) (25% weighting)
Option 1a – Sand plug at either end of
100% 50% 50% 100% 100% 83%
Dog Beach and shoreline nourishment
Option 1b – Sand plug at the southern
end of Dog Beach and shoreline 75% 25% 25% 75% 75% 58%
nourishment
Option 2 – Extension of the existing
training wall/groyne at western end of 75% 75% 50% 50% 75% 69%
Dog Beach
Option 3 – Extension of submerged
25% 75% 50% 0% 0% 30%
breakwater and two new groynes
Option 4 – Three new short groynes at
50% 100% 50% 50% 75% 66%
Dog Beach
Option 5 – Shore parallel seawall 100% 25% 25% 25% 75% 60%
Option 6 – Do nothing 0% 100% 25% 0% 0% 24%
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4.3.1 Option 1a: sand plug at either end of Dog Beach
Figure 4-2 illustrates the model representation of the sand plug at either end of Dog Beach. The sand
plugs are located where scour and dominant flow paths have developed adjacent to the geofabric
sand container structures. It’s assumed a small cutter suction dredge and slurry pipeline would be
used to relocate the sand from a nearby borrow area within the Noosa River estuary. Key features
of the option include:
• The sand plugs are represented by adjusting the model bathymetry in the areas shown;
• The crest elevation of each sand plug is 0 mAHD (approximately mean sea level); and
• The estimated minimum volume of sand needed to construct the plugs is (additional volume would
be required to nourish the shoreline):
○ Northern plug: 14,000 m3
○ Southern plug: 17,000 m3
The impacts to peak tidal current figures show:
• A minor reduction (~0.1 to 0.2 m/s) in peak flood current magnitude within the Dog Beach channel.
This is balanced by increases to current magnitude at the edges and over the crest of each sand
plug. This suggests that over the time the plugs will be gradually modified by the flood tide currents
with sediment eroded from the crest and likely deposited in the adjacent channel area. This could
be described as a gradual ‘smoothing’ of the constructed sand plugs.
• During peak ebb conditions the impact to currents is widespread with a significant reduction in
magnitude at the Dog Beach channel and shoreline, and an increase in magnitude through the
central channel. This suggests that the option is likely to relieve erosion pressure at the Dog
Beach shoreline and promote the development of a central channel.
• It is noted that the patterns described above are expected to diminish over time as the sand plugs
are gradually eroded and smoothed. It is assumed that the sand plugs would need to be
maintained for the option to continue performing as intended.
The whole of life cost estimate for this option is $3.4M with annualised costs around $170,000/year.
This estimate assumes three campaigns between 2020 and 2040. Each campaign would seek to
relocate up to 80,000 m3 of sand.
The potential for impact to environmental values is primarily related to the extractive dredging
activities and disturbance to the estuarine habitats. Dredging campaigns would need to be designed
to avoid the declared Fish Habitat Area and migratory bird season. Opportunities to enhance
terrestrial environmental values exist through revegetation and dune management programs to help
stabilise the nourishment material.
The social benefits are related to the restoration and maintenance of a recreational beach and the
redirection of boating traffic away from the Dog Beach channel.
The risks to Council are considered low to medium manageable. Full details of the risk assessment
results are provided in Appendix D.
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Sand plug (0 mAHD) Elevation (mAHD) . 2.0 _ 1.0 . 0.0 . 1.0 1 2.0 -3.0 -4.0 -5.0 -6.0 ial Image}24)March 2019 OME) Title: Figure: Rev: Option 1a: sand plug at either end of Dog Beach 4-2 A if BMT endeavours to ensure that the information provided in this “i on map is correct at the time of publication. BMT does not warrant, N 50 1 if Ss guarantee or make representations regarding the currency and 0 0Om ™ Z B M T accuracy of information contained in this map. / ApprOK S6als Saf www.bmt.org Filepath: |:\B23636.i.mpb.NoosaSpit_SEMP\DRG\COA_019_20190820_Option1A_both.wor
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Figure 4-3 Peak Flood Currents, Option 1a: sand plug at either end of Dog Beach
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Figure 4-4 Peak Ebb Currents, Option 1a: sand plug at either end of Dog Beach
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4.3.2 Option 1b: sand plug at southern end of Dog Beach
Figure 4-5 illustrates the model representation of the sand plug as the southern end of Dog Beach.
Like Option 1a, it’s assumed a small cutter suction dredge and slurry pipeline would be used to
relocate the sand from a nearby borrow area within the Noosa River estuary. Key features of the
option include:
• The sand plug is represented by adjusting the model bathymetry in the areas shown
• The crest elevation of the sand plug is 0 mAHD (approximately mean sea level)
• The estimated volume of sand needed to construct the plug is 17,000 m3 (additional volume would
be required to nourish the shoreline).
The impacts to peak tidal current figures show:
• Very little change to peak flood current magnitude within the Dog Beach channel. Increases to
current magnitude are predicted at the edges and over the crest of the sand plug. As described
above for Option 1a, this suggests that the flood tide currents will gradually erode and smooth the
constructed sand plug.
• The pattern of impact to ebb tide currents is like Option 1a, with a significant reduction in
magnitude at the Dog Beach channel and shoreline. Option 1a and 1b are similar in terms of the
immediate benefit to Dog Beach erosion associated with ebb tide currents, but with less sand
required to implement Option 1b.
• An increase in ebb tide current magnitude through the central channel is observed, assumed to
promote the development of a dominant ebb tide flow path through this area.
• It is assumed that the sand plug would need to be maintained for the option to continue performing
as intended. In comparison to Option 1a, the single sand plug at the southern end of Dog Beach
may need to be reinstated at more regular intervals, potentially offsetting the benefit of the
reduced sand volume needed for construction.
The whole of life cost estimate for this option is $4.1M with annualised costs around $200,000/year.
This estimate assumes five campaigns between 2020 and 2040. Each campaign would seek to
relocate up to 50,000 m3 of sand.
Like Option 1a, the potential for impact to environmental values is primarily related to the extractive
dredging activities and disturbance to the estuarine habitats with opportunities to enhance terrestrial
environmental values through revegetation and dune management programs to help stabilise the
nourishment material. The increased frequency of dredging activities (i.e. more regular disturbance)
is the reason Option 1b receives a lower score in comparison to Option 1a. The increased frequency
of disturbance is also the reason for the lower score with respect to social benefits and risks to
Council. Full details of the risk assessment results are provided in Appendix D.
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PE | Model Mesh Sand slug (O mAHD) Elevation (mAHD) . 2.0 _ 1.0 . 0.0 . 1.0 1 2.0 -3.0 -4.0 -5.0 -6.0 jal Image}24)March 2019 ONSET) Title: Figure: Rev: Option 1b: sand plug at southern end of Dog Beach 4-5 A a BMT endeavours to ensure that the information provided in this “i < map is correct at the time of publication. BMT does not warrant, N 50 1 if Ss guarantee or make representations regarding the currency and 0 oom ™* Z B M mT accuracy of information contained in this map. / ADpOX, S6ai8 Sa www.bmt.org Filepath: 1:\B23636.i.mpb.NoosaSpit_SEMP\DRG\COA_016_20190820_Option1A_sth.wor
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Figure 4-6 Peak Flood Currents, Option 1b: sand plug at southern end of Dog Beach
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Figure 4-7 Peak Ebb Currents, Option 1b: sand plug at southern end of Dog Beach
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4.3.3 Option 2: extension of the existing groyne at Dog Beach
Figure 4-8 illustrates the model representation of the extension to the existing groyne. Key features
of the option include:
• The crest elevation of the groyne is 1 m above AHD (not overtopped under normal tidal conditions)
• The extension is similar in length to the existing geofabric sand container groyne (effectively
doubling the length of the existing structure).
The impacts to peak tidal current figures show:
• A moderate reduction (~0.2 to 0.4 m/s) in peak flood current magnitude at the Dog Beach channel
and shoreline.
• Increases to flood tide at the head of the proposed extension, effectively transferring the scour
currently observed at the existing structure. There is also a minor increase in peak flood current
magnitude through the central channel adjacent to the groyne structure.
• The peak ebb tide impacts are like Option 1a and 1b, with a significant reduction in magnitude at
the Dog Beach channel and shoreline. An increase in ebb tide current magnitude through the
central channel is also observed.
• The groyne extension option is considered ‘permanent’ and would be developed with a goal to
minimise ongoing maintenance requirements. The design would need to account for local scour
potential at the structure.
The whole of life cost estimate for this option is $1.8M with annualised costs around $90,000/year.
This estimate is based on the cost for similar works in 2012 (i.e. the existing training wall) with
adjustments for inflation. This includes beach nourishment as part of the capital costs. It is noted that
the extended structure is not expected to stabilise the entire length of shoreline and therefore
additional management actions and costs may be required toward the eastern extent of the Dog
Beach shoreline.
The potential for impact to environmental values is primarily related to the construction phase. There
would also be a notable impact to visual amenity.
The social benefits are primarily related to stabilising a longer section of shoreline and providing a
width of beach for recreational opportunities.
The risks to Council are generally low to medium and manageable. The exception being pedestrian
slip hazard at the crest of the structure and the submerged hazard which could result in injury when
swimming (diving) or boating near the structure. Similar risks are associated with the existing
structure, so the training wall extension does not represent a significant change in risk profile. Full
details of the risk assessment results are provided in Appendix D.
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~»| Model Mesh Groyne (1 mAHD) Elevation (mAHD) . 2.0 _ 1.0 . 0.0 . 1.0 1 2.0 -3.0 -4.0 -5.0 -6.0 | =" J ar f % ~*~ Bhs ey J eAerial Imagey24}March 2019 ‘el OMETET?) Title: Option 2: extension of the existing groyne at Dog Beach Figure: 4-8 i BMT endeavours to ensure that the information provided in this “i << map is correct at the time of publication. BMT does not warrant, N 50 1 i? Ss guarantee or make representations regarding the currency and / 0 oom Z B M ai accuracy of information contained in this map. Z. ADpOX. S6ai8 Sa www.bmt.org Filepath: |:\B23636.i.mpb.NoosaSpit_SEMP\DRG\COA_018_20190820_Option2C_sth.wor
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Figure 4-9 Peak Flood Currents, Option 2: extension of existing groyne
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Figure 4-10 Peak Ebb Currents, Option 2: extension of existing groyne
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4.3.4 Option 3: extension of submerged breakwater and two new groynes
Figure 4-11 illustrates the model representation of the extension to the submerged breakwater and
addition of two new groynes. This option represents the full implementation of the strategy proposed
by Sunshine Coast Council. Key features of the option include:
• The submerged breakwater crest elevation at 0.6 m below AHD
• The groyne crest elevation at 0 mAHD (approximately mean sea level)
The impacts to peak tidal current figures show:
• Minimum change to peak flood and ebb tide currents along the shoreline bounded by the
submerged breakwater.
• An increase to current magnitude on the seaward side of the breakwater, expected to promote
scour and channel development (as observed against the existing submerged structure).
• A reduction in current magnitude between the groynes suggesting small sections of beach could
be maintained in these locations.
• An increase in current magnitude at the head of the small groynes suggesting scour local potential
that the design would need to accommodate.
The whole of life cost estimate for this option is $2.0M with annualised costs around $100,000/year.
This estimate is based on the cost for similar works in 2012 (i.e. the existing submerged structure)
and costs to construct small groynes at Munna Point, with adjustments for inflation. This includes
beach nourishment as part of the capital costs.
The potential for impact to environmental values is primarily related to the construction phase. There
would also be an impact to visual amenity associated with the two groynes.
The social benefits are primarily related to stabilising a longer section of shoreline and providing a
width of beach for recreational opportunities.
There are some high and extreme risks associated with this option. Like Option 2, there are
pedestrian slip and submerged hazards which could result in injury to the general public. In addition,
there are also political risks associated with continuing to support an expensive and unsuccessful
‘legacy’ design. Full details of the risk assessment results are provided in Appendix D.
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LEGEND Model Mesh (a Submerged breakwater (-0.6 mAHD) Groynes (OmAHD) Elevation (mAHD) . 2.0 . 1.0 . 0.0 . 1.0 1 2.0 -3.0 -4.0 -5.0 6.0 cy ; . - > ay =e We jae . i; 4 Aerial mage)24)March 2019 a a ; 4 ’ ~ ON : & learmap Pe oe Title: Option 3: extension of submerged breakwater and two new groynes BMT endeavours to ensure that the information provided in this map is correct at the time of publication. BMT does not warrant, 50 guarantee or make representations regarding the currency and / accuracy of information contained in this map. Approx. scale www.bmt.org Filepath: |:\B23636.i.mpb.NoosaSpit_SEMP\DRG\COA_015_20190820_Option3A. wor
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Figure 4-12 Peak Flood Currents, Option 3: extension of existing submerged breakwater
and two new groynes
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Figure 4-13 Peak Ebb Currents, Option 3: extension of existing submerged breakwater and
two new groynes
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4.3.5 Option 4: three new groynes
Figure 4-14 illustrates the model representation of the three new groynes. Key features of the option
include:
• The groyne crest elevation at 0 mAHD (approximately mean sea level)
The impacts to peak tidal current figures show:
• A local reduction to peak flood and ebbs currents in the vicinity of the three groynes suggesting
small sections of beach could be maintained in these locations.
• An increase in current magnitude at the head of the small groynes suggesting local scour potential
that the design would need to be account for. A dominant channel would be expected to form and
consolidate in the area of increased current magnitude.
The whole of life cost estimate for this option is $1.3M with annualised costs around $70,000/year.
This estimate is based on the costs to construct small groynes at Munna Point, with adjustments for
inflation. This includes beach nourishment as part of the capital costs.
The potential for impact to environmental values is primarily related to the construction phase. There
would also be an impact to visual amenity associated with the three groynes.
The social benefits are primarily related to stabilising a longer section of shoreline and providing a
width of beach for recreational opportunities. It is noted that the groyne field is not expected to
stabilise the entire length of shoreline and therefore additional management actions and costs may
be required toward the eastern extent of the Dog Beach shoreline.
Like Option 2, the risks to Council are generally low to medium and manageable. The exception
being the slip and submerged hazards which could result in injury. Similar risks are associated with
the existing training wall and groynes at Munna Point, so the groyne field does not represent a
significant change in risk profile. Full details of the risk assessment results are provided in Appendix
D.
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LEGEND Model Mesh Groynes (0 mAHD) Elevation (mAHD) . 2.0 - 1.0 . 0.0 | 1.0 . 2.0 -3.0 -4.0 -5.0 -6.0 Lv vi ser! ep OOERINED ig @ UNE Yaeee ye) Title: Option 4: three new groynes a; BMT endeavours to ensure that the information provided in this See map is correct at the time of publication. BMT does not warrant, 50 i? as guarantee or make representations regarding the currency and / j 5 accuracy of information contained in this map. / / ‘eh B MT Approx. scale www.bmt.org Filepath: |:\B23636.i.mpb.NoosaSpit_SEMP\DRG\COA_017_20190820_Option3B.wor
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Figure 4-15 Peak Flood Currents, Option 4: three new groynes
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Figure 4-16 Peak Ebb Currents, Option 4: three new groynes
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4.3.6 Option 5: shore parallel seawall
The indicative minimum footprint for construction of a shore parallel seawall (or similar coastal
protection structure) is illustrated in Figure 4-17. This footprint is defined by a ~20 m buffer from the
HAT contour on the southern side of The Spit, noting that the actual footprint would need to be
determined as part of a concept and detailed design study. It may be possible to construct the seawall
in stages; however, this would need to be carefully planned given the restricted access for land-
based equipment.
Regarding effectiveness, a properly designed and constructed seawall is expected to reduce the risk
of a breakthrough to an acceptable level. The whole of life cost estimate for this option is $4.1M with
annualised costs around $200,000/year. This includes beach nourishment as part of the capital
costs.
This option accepts the ongoing loss of dune and terrestrial habitat to erosion and would likely cause
further losses during the construction phase.
The social values associated with Dog Beach would be gradually lost. Ongoing nourishment of the
shoreline could be used to maintain beach amenity in front of the seawall; however, the seawall
would be designed to be stable in a fully exposed condition (that is, beach nourishment would not be
required for the structure to perform as intended).
The risks to Council are generally low to medium and manageable. The exception being the relatively
large investment of public funds and the perception of benefiting a small number of private properties.
Full details of the risk assessment results are provided in Appendix D.
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LEGEND Indicative Seawall Footprint HAT Contour (Noosa Sound) Elevation (mAHD) . 2.0 . 1.0 Title: Option 5: shoreline parallel seawall Figure: 4-17 Rev: BMT endeavours to ensure that the information provided in this map is correct at the time of publication. BMT does not warrant, guarantee or make representations regarding the currency and accuracy of information contained in this map. ~ sre (as ws «7 BMT www.bmt.org Filepath: |:\B23636.i.mpb.NoosaSpit_SEMP\DRG\COA_022_20191017_Option5.wor
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4.3.7 Option 6: do nothing
The ‘do nothing’ option allows the Dog Beach shoreline to recede without intervention and accepts
the consequences of a breakthrough event which include:
• Gradual loss of the environmental and social values associated with Dog Beach;
• The potential for rapid morphological change at The Spit following a breakthrough event, the
broader Noosa Woods area may be gradually lost;
• Increased exposure to coastal hazards for existing private and commercial development;
• Increased ‘normal’ high tide levels and reduced freeboard for existing development within the
lower Noosa River; and
• Increased frequency of ‘nuisance’ flooding within the lower Noosa River.
This option assumes no immediate investment in shoreline erosion management at Dog Beach. The
costs of intervention after a breakthrough event would be significantly greater than the cost for other
options presented in the SEMP. The construction would be significantly more complex and solution
likely to be a hard (rock) engineered structure. It is assumed the broader long-term costs to the
community and local economy could be substantial in comparison to the proactive intervention
options.
There are several potentially extreme risks to Council associated with the ‘do nothing’ option,
including:
• Political risks due to the increased threat to existing development;
• Legal challenges from impacted property owners; and
• Financial risks due to the additional cost for mitigating risks after a breakthrough event has
occurred.
Full details of the risk assessment results are provided in Appendix D.
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5 Proposed Implementation Pathway
5.1 Introduction
A proposed strategy for managing erosion at Dog Beach and avoiding a breakthrough of The Spit is
provided below, building on the understanding of the system presented in the previous Chapters.
A trigger-based approach for coastal management was introduced in Section 4.2 and has been used
to develop the strategy. Here the approach is embedded within the ‘risk continuum’ framework
originally described by Fisk and Kay (2010). This approach was established to deal with uncertainty
associated with climate change adaptation and planning. However, it has also been readily accepted
and integrated into leading practice within the context of contemporary coastal management in
Queensland (see Barnes et al., 2017). The risk continuum acknowledges uncertainty in the success
of management actions and relies on ongoing monitoring and performance criteria to trigger changes
in approach to achieve an overarching objective.
The risk continuum is illustrated in Figure 5-1. Within this approach, it is important to define the point
of unacceptable impact, i.e. the point at which the relevant planning outcome has failed or can no
longer be achieved. Working back from this point allows identification of one or more triggers for
enhanced management action and implementation to avoid reaching the unacceptable impact.
Figure 5-1 Actions along the Risk Continuum (adapted from Fisk & Kay 2010)
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5.2 Proposed Trigger-based Management Approach
In the context of the current project, the unacceptable impact is a breakthrough of Noosa Spit at Dog
Beach. Two triggers for enhanced management action are proposed:
• Tigger 1: Limited recreational beach width at Dog Beach and loss of vegetation (fallen trees)3
• Trigger 2: The width of vegetated land above high water has narrowed to 20 m or less
Upon realisation of the first trigger, implementation of beach nourishment and sand plugs (i.e. the
preferred option based on the MCA presented in Section 4.3) is proposed. This action is intended to
remain the preferred management strategy until it is no longer sustainable and/or delivering benefits
to Council and the community. It is anticipated that the works would be repeated several times
between now and 2040 and help to mitigate the risk of a breakthrough event.
The second trigger represents significant narrowing of The Spit width at Dog Beach and signals that
the beach nourishment strategy is not performing as intended. A notional 20 m width of land above
the high water mark represents the likely minimum development footprint required for land-based
construction of a seawall or similar shoreline protection structure. The trigger-based approach is
designed to avoid a seawall for as long as possible and only calls for consideration of this action if
beach nourishment is unable to maintain the risk of a breakthrough at an acceptable level.
The three key stages of a proposed implementation plan are summarised in Table 5-1 and illustrated
in Figure 5-2. The proposed actions are triggered when the approved activities of the current stage
of management are no longer maintaining the risks to an acceptable level. The ongoing beach
monitoring program and visual inspection of the shoreline can be used to assess the current stage
of management and determine whether planning for subsequent actions should commence. Stage
2 of the proposed plan could commence immediately, with the current condition of the shoreline
suggesting that Trigger 1 has been reached (see bottom panel of Figure 5-2). Implementation of the
proposed beach nourishment and sand plugs would effectively widen the beach and monitoring
would then focus on identifying when the Trigger 1 condition returns, thereby prompting the planning
for a subsequent nourishment and sand plug campaign to reinstate the beach width. Ongoing
resilience building actions, including revegetation and habitat management, are expected to continue
as part of routine maintenance.
3
The Trigger 1 shoreline position is approximated in Figure 5-2 using the HAT contour in 2016
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Table 5-1 Key Stages and Triggers for Proposed Management Actions
Stage 1 Period of Acceptable Risk
Resilience building Implement and/or continue ‘no regrets’ actions, namely:
actions • Review/update erosion studies; investigate funding sources for works; community
education and consultation; dune and habitat management; beach access management.
Shoreline monitoring to Continue monitoring program through upper beach surveys, hydrographic surveys, aerial
define current condition imagery analysis and modelling.
and understand trends
Develop a response Develop a response plan including:
plan (i.e. the SEMP) • Evaluate risk reduction options
• Concept planning for preferred option(s)
• Seek agency support
Define triggers for Commence planning for next stages of risk management:
enhanced • Trigger 1: limited recreational beach width and loss of vegetation, progress to Stage 2
management action management
• Trigger 2: the width of vegetated land above HAT has narrowed to 20 m (or less),
progress to Stage 3 management.
Stage 2 Risk Approaching Unacceptability
Trigger 1 is reached The first trigger for enhanced management action is realised, namely:
• Limited recreational beach width at Dog Beach and loss of vegetation
Risk reduction Develop and implement risk reduction measure:
management action: • Beach nourishment/sand plug concept design and approvals
beach
nourishment/sand plug • Detailed design and construction of beach nourishment/sand plugs
construction • Monitor shoreline and repeat works when Trigger 1 is reached (estimated every 5 years)
Shoreline monitoring to Continue monitoring program to quantify the benefit of Stage 2 management actions.
define current condition
and understand trends
Ongoing resilience Continue ‘no regrets’ actions, namely:
building actions • Review/update erosion studies; investigate funding sources for works; community
education and consultation; dune and habitat management; beach access management.
Review/update Review response plan and consider the need for an enhanced or alternative management
response plan approach.
Stage 3 Unacceptable Risk
Trigger 2 is reached The second trigger for enhanced management action is realised, namely:
• The frequency of beach nourishment/sand plug renewal is unsustainable; and/or
• The width of vegetated land above HAT has narrowed to 20 m (or less)
Risk reduction Consider the development and implementation of the following risk reduction measures:
management action: • Seawall concept design and approvals
seawall
• Seawall detailed design and construction
Shoreline and seawall Continue monitoring program through upper beach surveys; inspect condition of seawall.
monitoring
Ongoing resilience Continue ‘no regrets’ and permitted activities, namely:
building actions • Community education and consultation; habitat management; beach access
management; beach nourishment (if considered viable).
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LEGEND Acceptable =———— HAT contour Risk in 2016 Approaching Unacceptable Risk Unacceptable Risk Title: Trigger Zones for Dog Beach Shoreline Management Aerial Image 22:September 2016 © Nearmap , ae ee TTA aPC © Nearmap Figure: 5-2 se a ‘te BMT
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5.3 Legislative Framework & Approvals
The management actions proposed for the area consist of the following elements:
• Low impact works, focused primarily on dune management
• Beach nourishment, likely through use of dredging
• Potential construction of a seawall.
Table 5-2 provides a summary of the approvals and legislative framework associated with these
different works. Note that while part of the Noosa River is a fish habitat area (FHA) no works are
proposed to occur in the boundaries of this area. Additionally, the Noosa River sand shoals are likely
to be an important habitat for migratory shorebirds based on the criteria set out in EPBC Policy
Statement 3.21 – Industry guidelines for avoiding, assessing and mitigation impacts on EPBC Act
listed migratory shorebird species (Commonwealth Government, 2015). This is because of the
diversity of shorebird species known to occur throughout the lower Noosa River.
Table 5-2 Approval Considerations for Shoreline Erosion Management Actions
Works Approvals Other considerations
Low impact Development Permit for marine Works interfering with dunes are expected to meet
works plant disturbance – applies for the Code for Accepted Development for tidal works or
any works that disturb >50 m2 work completely or partly in a coastal management
of marine plants (including district (EPP/2017/3930). However, where this is not
dune vegetation) the case, works will require a Development Permit for
disturbance of state coastal land.
If works will impact on a breeding place for an animal
or a protected plant, further permits under the Nature
Conservation Act 1992 will be required.
Beach Allocation of Quarry Material Works need to be kept at least 50 m from boundary of
nourishment – Environmental Authority for FHA to prevent turbidity impacts.
dredging Environmentally Relevant EPBC Referral recommend due to potential for
Activity 16(1) significant impact; however, no EPBC Permit
Development Permit for tidal expected. Recommended that works occur outside of
works migratory shorebird season.
Development Permit for marine Works will need to be accompanied by a Dredge
plant disturbance – applies if Management Plan, including measures for managing
dredging disturbs seagrass or environmental, amenity and navigability impacts.
macroalgae
Beach Development Permit for tidal If works will impact on a breeding place for an animal
nourishment - works – applies if nourishment or a protected plant, further permits under the Nature
placement volume exceeds 5,000 m3 per Conservation Act 1992 will be required.
beach compartment per year EPBC Referral recommend due to potential for
Development Permit for marine significant impact; however, no EPBC Permit
plant disturbance – applies for expected. Recommended that works occur outside of
any works that disturb >50 m2 migratory shorebird season.
of marine plants (including
dune vegetation)
Seawall Development Permit for tidal Works will need to be accompanied by engineering
construction works assessments and understanding of potential impact
on surrounding geomorphology.
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References
6 References
Barnes, M.P., Visser, J. and Fisk, G. (2017). Implementation of Trigger-Based Coastal Management
Strategies, Coasts & Ports 2017 Conference.
Collins (1972). Prediction of shallow-water spectra, Journal of Geophysical Research, Volume 7,
Issue 15, Oceans and Atmosphere, 2693 – 2707.
Geoscience Australia (2017). High-resolution depth model for the Great Barrier Reef, Beaman R.J.
Fisk, G. & Kay, R. (2010). Dealing with uncertainty in climate change adaptation planning and
developing triggers for future action, Practical Responses to Climate Change Conference 2010,
Melbourne, September 2010.
Commonwealth Government (2015). EPBC Act Policy Statement 3.21 – Industry guidelines for
avoiding, assessing and mitigating impacts on EPBC Act listed migratory shorebird species.
Commonwealth Department of the Environment, Canberra, Australia.
ICM (2010a). Option Review Noosa River Spit, prepared for Sunshine Coast Regional Council.
ICM (2010b). Noosa River Spit Erosion Protection Works Drawing Register, 23 November 2010,
prepared for Sunshine Coast Regional Council.
MSQ (2019). Queensland Tide Tables 2017. Maritime Safety Queensland.
O’Brien, M. P. (1969) Equilibrium Flow Areas in Inlets on Sandy Coasts. Journal of the Waterways
and Harbours Division. ASCE No. WW1, pp.43-52.
Queensland Government (2012). Queensland coastal risk and bathymetric LiDAR: a pilot study for
collecting near-shore bathymetry. Queensland Department of Science, Information Technology,
Innovation and the Arts, Brisbane, Australia.
Saha, S., and Coauthors (2010). The NCEP Climate Forecast System Reanalysis. Bull. Amer.
Meteor. Soc., 91, 1015-1057.
Saha, S., and Coauthors (2014). The NCEP Climate Forecast System Version 2. J. of Climate, 27(6),
2185-2208.
Tomlinson and Chamberlain (2006). Noosa River Entrance Channel Dynamics, Griffith University,
CRC for Coastal Zone, Estuary and Waterway Management, 1 – 75.
van Rijn, L.C., D.J.R. Walstra and M. van Ormondt (2004). Description of TRANSPOR2004 and
Implementation in Delft3D-ONLINE. Z3748.10 – report prepared by Delft Hydraulics for DG
Rijkswaterstaat.
WMA Water (2017). Noosa River Flood Study Upgrade, prepared for Noosa Shire Council, March
2017.
WRL (2014). Riverbank Vulnerability Assessment using a Decision Support System: Clarence River
(Rogans Bridge to Ulmarra), WRL Technical Report 2014/12 December 2014.
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BMT Eastern Australia Pty Ltd
Level 8, 200 Creek Street
Brisbane Qld 4000
Australia
PO Box 203, Spring Hill 4004
Tel: +61 7 3831 6744
Fax: + 61 7 3832 3627
ABN 54 010 830 421
www.bmt.org
Technical Memorandum
Noosa Shire Council
From: Matthew Barnes To: Daniel Wishaw
Date: 29 March 2019 CC:
Subject: Noosa Spit SEMP - Lower Noosa River Metocean Data Collection
1 Instrument Deployment Summary
To inform the Noosa Spit SEMP, metocean data collection has commenced including:
• The deployment of six tide recorders in the lower Noosa River to continuously measure water level for
approximately six weeks. This data will be used to calibrate the hydrodynamic model and may also
provide some valuable information to partially address concerns regarding the published tidal planes.
• Offshore fixed deployment Acoustic Doppler Current Profiler (ADCP) to continuously measure water
level, current speed, current direction and wave parameters (height, period and direction). This data will
be used to calibrate both the hydrodynamic and wave models.
• Boat-mounted ADCP measurements have been collected during both neap and spring tidal conditions.
The measurements (from approximately low water to low water) were taken at Dog Beach, Noosa
Sound, Munna Point and Noosaville. This data will used to calibrate the hydrodynamic model and
understand the peak flood and ebb tide currents occurring at Dog Beach.
Figure 1-1 provides a map showing the instrument deployment and boat-mounted ADCP cross-sectional
transect locations. Table 1-1 provides a summary of the instruments. It is anticipated that the deployed
instruments will be retrieved in late April 2019.
Section 2 provides further details on the boat-mounted ADCP measurements
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LEGEND Offshore ADCP @ = In-situ Water Level Recorders Oo In-situ Barometric Pressure Recorders Approximate ADCP Cross Section Locations Instrument Locations BMT endeavours to ensure that the information provided in this map is correct at the time of publication. BMT does not warrant, guarantee or make representations regarding the currency and accuracy of information contained in this map Filepath: _|:\B23636.i mpb.NoosaSpit_SEMP\DRG\COA_001_Equipment_locations.wor Figure 1-1 0.5 Approx. Scale www.bmt.org
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