Two Rocks Marina - transport.wa.gov.au · This document provides a copy of the presentation...

Objective ID: A10488314 of 24

Two Rocks Marina Reference Group Meeting No. 3 Presentation Summary


Objective ID: A10488314

Table

Version No.

Date Prepared by Revision or issue description Issued to

0 12/07/2018 A Kelderman Final for Website Publishing D. West


Purpose of this Report

This document provides a copy of the presentation provided to members of the Two Rocks Marina Reference Group on June13, 2018 in Two Rocks.

It should be noted that the presentation formed part of a larger discussion at the Reference Group meeting, not all of which is captured in the presentation document.

Agenda

The Two Rocks Marina Reference Group meeting considered the following agenda items:

Welcome / Introductions

Terms of Reference

Two Rocks Marina History

Public Information Session Overview

Status $6 Million Upgrade

Modern Boat Harbours Overview

Redevelopment - Constraints, Opportunities, Issues , What we Like - Workshop

Agenda for Meeting No. 4 & 5

Feedback

Presentation

The Two Rocks Marina Reference Group Meeting No. 3 presentation is attached to this document at Appendix A.


Appendix A

Two Rocks Marina Reference Group Meeting No. 3 presentation.

Presented at the Two Rocks Marina Reference Group meeting No. 3 dated June13, 2018

Two Rocks Marina

Reference Group Meeting No. 313 June 2018

� Welcome / Introductions� Confirmation of minutes and feedback

� Indicative Planning Program

� Seagrass Presentation and Q&A

� Erosion Presentation and Q&A

� General business

� Next meeting, evaluation and close

Order of Proceedings

Welcome / Introductions

� Welcome – new members

� Key objective of the Reference Group

"The formation of a Community Reference Group in the early stages plays a key role in ensuring community and user group interests and concerns are identified and addressed."

Attorney General & Butler MLA John Quigley, 14 September 2017

� Welcome / Introductions

� Confir mation of minutes and feedback� Indicative Planning Program






� Feedback� Masterplan

� Repairs required and timeline for repairs� Funding breakdown (inc. current awarded expenditure/contracts)

� Detailed information/items for resolution:� Wrack issues� Reclamation of lands� Masterplan that can be presented to the community

� Safety� Public space

� Aquaculture (fish hatchery)

� Opportunities and Constraints plan

Minutes and Feedback

� Repairs required and timeline for repairs

� Funding breakdown (inc. current awardedexpenditure/contracts)

Minutes and Feedback

Works Packages - Committed Contrac tor Total Committed Forecast

(ex GST)

Demolish ageing maritime structures (fuel jetty, select boat pens) & Install new relocated boat pens (limited)

Shorewater Marine $1,178,535

Upgrade & maintenance to existing P jetty Broadspectrum $16,458

Westlink jetty refurbishment Broadspectrum $398,875

Remove abandoned vessels Various $634,160

Undertake priority breakwater repairs Ertech $468,817

Total $2,696,845

Uncommitted Funds $3,303,155



� Opportunities and Constraints Plan

Minut es and Feedback


� Confirmation of minutes and feedback


� Seagrass Presentation and Q&A� Erosion Presentation and Q&A




Two Rocks Marina – Coastal & Wrack Investigations

Reference Group Meeting No. 3

13 June 201811

� Existing erosion at northern beach since 1974 ,threa tening private and public properties/Assets

12



� Seagrass wrack trapping in summer, creatingunple asant odour to beach goers and tourists

13

� Minimize the duration of wrack on beach

� Minimize the risk of asset damage/loss

� Maximize the public access and enjoyment of thebeaches

� Present Effective and Sustainable Managementoptions, in line with State Coastal Planning PolicySPP2.6

Our goal in the redevelopment

14

Efforts in achieving our goals

�Aerial photo collection, shoreline movementrecord 1942- 2017, wrack presence

�Hydrographic surveys

�Offshore and near-shore wave measurements

�Near shore wave, currents, and water levels

�Wrack monitoring, field photos and live beachcamera since 4 July 17

�Geophysical survey for buried rock levels

�Select the best coastal engineers, best wrackmodel and modeller, and the most reputableprofessionals in seagrass management.

15

� Two Rocks historical literature/data review & coastalgeomorphology Assessment – DoT 2013

� Two Rocks wrack monitoring report (winter + summerfollow-up 2013-14) – DoT 2014

� Joint analysis of Two Rocks wrack accumulation event withcurrent and water levels – DoT 2014

� Seagrass Wrack Movement & Coastal Sand TransportAssessment for the Two Rocks Marina Redevelopment –UWA 2014

� Northern Two Rocks Geophysical Surveys - GBGMAPS� Two Rocks Marina Water Quality Flushing Rate Modelling –

Worley Parsons 2016� Two Rocks Boat Harbour Expansion – Coastal Impact

Assessment - MP Rogers 2017

Engineering investigations completed

16

Our understanding of wrack movement

http://www.abc.net.au/news/2018-05-28/busselton-jetty-swamped-by-wave-of-sea-grass-after-storms/9807136

17

‘Summer’ - quiescent period.

Wrack trapped by the Northern Rock and southerly wind driven current.

‘Winter’ - storm period.Wrack is moved into and removed from beaches quickly by dynamic wind driven currents.

Wrack ‘life-cycle’ at Two Rocks coast

Late Summer/Autumn.

Wrack is removed from the beaches naturally.

18



19 20

Click to edit Master title style

Cameras installed at Two Rocks South and North

Camera period: from 4 July 17 to present

Winter imagery

21

Camera imageries in Summer

22


Duration of Wrack on South Beach

Longest wrack trapping: 61 days 30/01/2018 to 31/03/2018

2nd Longest wrack trapping: 39 days 20/12/2017 to 27/01/2018

23

Wind conditions when wrack trapped

39 days20Dec17 - 27Jan18

61 days30Jan18 - 31Mar18

Summer

=12 knots

=27 knots 27 knots=

12 knots=24



Wind conditions when wrack cleared

3 days 28 to 31 Jan2018

50 days4 Jul to 23 Aug 2018

25

Wrack presence at Northern Beach

26

Duration of Wrack on Northern Beach

27

Past investigations on wrack management

28

14 Feb 2014 DoT field estimate Volume on South Beach:

34,858m3

29

DoT 2013 – 2014 Wrack volume at Two Rocks South Beach

May to July 2013 14 Feb 2014

30



Click to edit Master title style1. Remove wrack and use it for garden mulch, dump at land fills, or place it back in waters north

2. Cap the seagrass wrack with sand to alleviate the odour 3. Push wrack into the sea during periods of favourable

winds and seas,4. Remove the rock and reef adjacent to the marina

breakwater,5. Build the beach out to rock and reef adjacent to

breakwater,6. Change the breakwater configuration to create a

sheltered swimming beach to inside the new marina, and7. Change the breakwater configuration to extend the

marina to the south and create development opportunities that could fund the works.

Recommendations to City of Wannerooby 2000 MRA investigation

�

�

31


32


33

ITEMCAPEX (Exc

GST)

Project Development

(Investigations, Approvals, Design)

$2,000,000

Breakwaters, Revetments &

Beach$24,000,000

Reclamation (sand fill)

$5,000,000

Harbour Boardwalk $2,000,000

Roads, Carpark, Paths

$4,000,000

Services (Allowance)

$1,000,000

Parks, Beach, Landscaping &

Toilets$2,000,000

$40,000,000

SOUTHERN BREAKWATER REALIGNMENT Experience from Port Geographe wrack manage ment

Sep 2013July 2 013

34

Wrack trapped all year round Beach wrack volume: ~150,000 m3 Worst in winter

35

Feb 10

36


Apr 14 Sep 14

Feb 15 Dec15

Oct 16 May 17

Presented at the Two Rocks Marina Reference Group meeting No. 3 dated June 13, 2018


Mar 18Post reconfiguration wrack monitoring

44

Peak volume of wrack prior to 2015: 150,000 m3

Wrack Management target set by EPA: Less than 60,000 m3 by Dec. each year

45

Odour (H2S) target by Dep. Of Health: 24 hour average H2S concentrations adjacent to the Western beach

0.1 ppmhttps://www.transport.wa.gov.au/projects/port-geographe-reconfiguration.asp

46

Ball park costs for moving 10,000m³ of wrack:

1. Allow natural conditions to remove ($0)2. Pulling material to the back of the beach to dry

(~$20K+) this reduces odour once wrack dries butwrack remains on the beach

3. Pushing material into the sea (~$10K-$20K+) (mayor may not be successful ie material could bepushed straight back onto beach)

4. Bypassing material down drift (beyond the barrier) –pumping (~$300-$400K+)

5. Bypassing material down drift (beyond the barrier) –trucking (~$150-200K+)

Wrack management options and costs

Q & A

Thank you…





� Erosion Presentation and Q&A� General business





Two Rocks Marina ProjectTwo Rocks Marina ProjectTwo Rocks Marina ProjectTwo Rocks Marina Project

Trent Hunt

Principal Coastal Engineer

m p rogers & associates pl

Coastal Processes

Outline of AssessmentOutline of AssessmentOutline of AssessmentOutline of Assessment

• Part 1 – Knowledge Summary• Outlined existing conditions and knowledge

• Part 2 – Expansion Impacts• Based on Part 1 knowledge

• Assessed the impacts of the expansion on coastal processes

• Part 3 – Coastal Management• Assessed coastal management options

• Concept level assessment

• Recommendations on Further Assessment

m p rogers & associates p l

Part 1 Part 1 Part 1 Part 1 ---- Knowledge SummaryKnowledge SummaryKnowledge SummaryKnowledge Summary

• Background

• Geology / Geomorphology

• Metocean Conditions• Water Levels

• Waves

• Currents

• Winds

• Shoreline and Sediment Movement

• Wrack Accumulations• Mechanisms & Quantities


Background Background Background Background –––– Existing IssuesExisting IssuesExisting IssuesExisting Issues

• Two Rocks Boat Harbour constructed in 1973

• No coastal management completed since

• Ongoing and large accretion south of marina and largeerosion north

• Large seagrass wrack accumulation south of harbour insummer

EROSION

ACCRETION

WRACK

Background Background Background Background –––– Previous StudiesPrevious StudiesPrevious StudiesPrevious Studies

• Large number of previous studies in the area completed, including key studies:

• Investigations on shoreline erosion (1986, 2007, 2014)

• Monitoring seagrass wrack accumulation (2000, 2003, 2014)

• Modifying alignments of breakwater (2003)

• Physical modelling of wrack accumulation (2003)

• Numerical modelling of wrack accumulation (2014)

• These were reviewed, considered and updated wherenecessary for this study


Existing Beach Erosion Issue Existing Beach Erosion Issue Existing Beach Erosion Issue Existing Beach Erosion Issue

• Previously investigated by MRA in 2006 / 2014

• Focussed on beach erosion only, not wrack

• Most recent work worked through a range of coastalmanagement options

• Recommended options for progressed design:• Managed Retreat

• Groynes (staged)




Managed RetreatManaged RetreatManaged RetreatManaged Retreat


Staged GroynesStaged GroynesStaged GroynesStaged Groynes


Proposed ManagementProposed ManagementProposed ManagementProposed Management

• Geotech investigations in the dunes followed thesestudies

• By undertaking no management and allowing theshoreline to erode, Managed Retreat option essentiallybeing implemented

• Critical values included beach use, access andrecreation

• Interim and long term measures should consider thiscarefully

• Beach access stairs recently replaced


Site ConditionsSite ConditionsSite ConditionsSite Conditions

• North

• South

Geology / GeomorphologyGeology / GeomorphologyGeology / GeomorphologyGeology / Geomorphology

• Generally sandy shoreline and dunes, overlaying rockat some levels

• Sediment cell from Yanchep to Mallee Point. Note thatthere appears to be significant sediment transport pastthese boundaries.

• Geotechnical investigations have shown rock at varyinglevels on beach and dunes north of the Marina. Wouldprovide some protection (not completely consistent) and would slow and vary the erosion.

• May result in more traditional “perched beaches” inthe future. Majority not believed to act in this waycurrently.


GeotechGeotechGeotechGeotech InvestigationsInvestigationsInvestigationsInvestigations

• Original investigations in 2014

• Will be discussed further




MetoceanMetoceanMetoceanMetocean ConditionsConditionsConditionsConditions

• Winds, waves, water levels and currents measured forregion

• Targeted measurements in the nearshore

• Internal measurements not analysed

• Waves (nearshore)• Typically from the SW over summer

• Slightly more W in winter months

• Hs typically 0.5 - 1.5 m over summer

• Hs typically 0.5 - 2.5 m over winter

• Currents (nearshore)• Analysed depth averaged and surface currents

• Surface currents had less variation seasonallym p rogers & associates p l

MetoceanMetoceanMetoceanMetocean ConditionsConditionsConditionsConditions

• Currents (continued)• Surface currents generally N to NNW

• Depth averaged currents varied slightly seasonally

• Over summer, NNW to NW

• Over winter S to SE, with minor NW to NNW components

• Water Levels• Measurements at Fremantle provide adequate long term

record

• Inter-annual cycles exist

• Increased mean water levels over past 2 decades

• Slight decrease in annual water levels since 2011


Shoreline / Sediment MovementShoreline / Sediment MovementShoreline / Sediment MovementShoreline / Sediment Movement

• Net sediment transport north, but seasonalmovements

• Clear trends post-construction

• Assessment against 1981 shoreline reasonable ascovers whole sediment cell

• Integrated coastal monitoring program could betterinform sediment budget

• Monitoring surveys often missing data at key locations– make comparison difficult



• Updated assessment 1981 - 2014



• Compared reasonably well with estimates from previous studies

• Accretion continuing

• Erosion slowing slightly or halted in some areas inrecent years


Wrack AccumulationsWrack AccumulationsWrack AccumulationsWrack Accumulations

• Some studies on wrack transport in the area, butseveral key items unknown

• Benthic habitats

• Confirmation of species

• Accumulate under SW to SE wind conditions• Typically sea breezes, but does occur in winter

• Clear under N to WSW wind conditions• Typically winter storms

• Therefore typically accumulates over spring andsummer, with no clearing mechanism

• Small quantities accumulate on northern side ofmarina, but naturally disperse





• Wrack trapped between northern rock and marina

• Accumulates under SW to SE wind conditions

• Clear under N to WSW wind conditions

• Therefore typically no clearing mechanism oversummer

• Small quantities accumulate on northern side ofmarina, but naturally disperse



• No clear trends in accumulation over years

• Quantities on southern beach 10,000 to 35,000 m3

• Average quantity over summer months 21,000 m3

• Noted snapshots from aerials

• Further detailed monitoring recommended to fine tunequantity estimates and impact of water levels

• Need to be considered in coastal management options(as flux past marina increased)


Part 2 Part 2 Part 2 Part 2 –––– Impact of ExpansionImpact of ExpansionImpact of ExpansionImpact of Expansion

• Geotechnical Investigations & Assessment

• Potential Storm Erosion

• Shoreline Recession Due to SLR

• Shoreline Response – Following Expansion

• Wrack Accumulation – Following Expansion

• Recommendations

Geotechnical AssessmentGeotechnical AssessmentGeotechnical AssessmentGeotechnical Assessment

• Investigations in 2014 and 2016

• Competent rock assessed at +3 mAHD or above

• Competent rock will provide some resistance to erosion

• MRA assessed lines of competent rock, and +1, +2:• Linearly interpolated where not clear


GeotechGeotechGeotechGeotech –––– Competent Rock LinesCompetent Rock LinesCompetent Rock LinesCompetent Rock Lines

• Assessed lines of rock to resist erosion

• Further investigation completed to infill information


Storm ErosionStorm ErosionStorm ErosionStorm Erosion

• Assessed profiles north and south• South – representative of stretch from Spot to Wreck Point

• North – 2 profiles, one near stairs and one representative oftypical shoreline north. Included nearshore reef as consistent through this area.


Erosion• South – 35 m

• North 1 – 30 m

• North 2 – 25 m



Storm Storm Storm Storm –––– SPP2.6SPP2.6SPP2.6SPP2.6

• Ran SPP2.6 storm – 100 year ARI and thereforeconservative

• Used calibrated wave model to get waves to nearshore

• Ran nearshore waves and water levels to shoreline

• Estimated erosion behind HSD (=+2 mAHD)


Northern ProfileSouthern Profile

Nearshore rock

Sea Level Rise AllowancesSea Level Rise AllowancesSea Level Rise AllowancesSea Level Rise Allowances

• Used allowances from DoT (2010)


Recession due to SLRRecession due to SLRRecession due to SLRRecession due to SLR

• Nearshore slope estimated from active depths andheights and storm erosion modelling

• Consistent with sediment budget and shorelinemovement assessments

• Used these factors for estimating SLR

• Note potential perched beaches to north – likely toshow slightly less recession due to SLR in the longerterm


Shoreline Response to Expansion Shoreline Response to Expansion Shoreline Response to Expansion Shoreline Response to Expansion

• Considered a number of factors in assessing theshoreline response:

• Existing trends in movement. For instance the shoreline north of the Boat Harbour already has no sediment feed,leading to recession. It will still have no feed following expansion, but the trend will shift slightly north.

• Equilibrium alignment of the shoreline north of theexpansion, leading to slight acceleration of erosion

• Potential wave shadowing north of the expansion

• Rock locations

• Recession due to SLR

• Future changes in movement and feeds

• Following estimate of shoreline response, considerationgiven to potential storm erosion and fluctuations


Shoreline Response Shoreline Response Shoreline Response Shoreline Response ---- SouthSouthSouthSouth

• Sediment feed from the south likely to continue• Beach south of Wreck Point likely to continue to accrete, with

the rate slowing into the future

• Feed past Wreck Point and southern rock likely tocontinue to be small

• In future decades as the influence of the rock decreases feedmay increase slightly

• Realignment of beach between southern rock andnewly aligned southern breakwater

• Some feed north along breakwater, likely to drop out indeeper water


Shoreline Response Shoreline Response Shoreline Response Shoreline Response ---- SouthSouthSouthSouth

• First pass of shoreline response





Flux Past Boat HarbourFlux Past Boat HarbourFlux Past Boat HarbourFlux Past Boat Harbour

• Likely to be relatively small, largely summer movement

• Movement along breakwater into deeper water

• Breakwater in -5 to -7 mAHD

• Sediment likely to drop out of suspension alongbreakwater

• Over time some will bypass harbour and drop out inentrance

• Due to coarse core believed in breakwaters, may findsome sediment migrates through breakwaters


Shoreline Response Shoreline Response Shoreline Response Shoreline Response ---- NorthNorthNorthNorth

• First pass of shoreline response


Wrack AccumulationWrack AccumulationWrack AccumulationWrack Accumulation

• Modification of southern breakwater expected to havelarge effect on mechanisms of movement and trapping

• MRA (2003) physically modelled a similar alignment• Showed that the mechanisms of movement were reversed

• Accumulated wrack around South Rock under NW winds

• Cleared wrack under S to SW winds

→ Early parts of storm accumulate, laKer parts clear

→ Sea breezes over summer can clear

• UWA (2014) numerically modelled a similar alignment• Snapshots presented show less accumulation

• Not clear how long wrack stays

• Don’t model directly comparable range of conditions

• Noted more wrack in other areas (marina, north)

• Believe less accumulation southm p rogers & associates p l

Wrack Accumulation Wrack Accumulation Wrack Accumulation Wrack Accumulation ---- SouthSouthSouthSouth

• Less wrack accumulated (<25%)

• Mechanisms reverse, less accumulation in summer

• Under some conditions (high water levels) could stillaccumulate quantities of wrack


Wrack MovementsWrack MovementsWrack MovementsWrack Movements

• Similar overall wrack quantities, but increasedbypassing of breakwater

• Similar overall quantities, but increased in individual events

• May result in increased wrack in marina or north of Boat Harbour

• Without interference accumulations to north likely tocome and go as currently do

• Movements to the north need to be carefullyconsidered for any coastal management options


Recommendations for RefinementRecommendations for RefinementRecommendations for RefinementRecommendations for Refinement

• Shoreline Responses• Likely responses should be refined using numerical modelling,

calibrated to sediment budget

• Wrack Movements & Accumulation• Actual alignment should be numerically modelled to test

likely accumulations

• Needs to consider range of conditions and allow direct comparison with existing cases

• Needs to estimate periods of accumulation rather thansnapshots and assess all areas (south, marina, north)

• Increased monitoring of wrack accumulations – timing,conditions and quantities




Part 3 Part 3 Part 3 Part 3 –––– Coastal ManagementCoastal ManagementCoastal ManagementCoastal Management

• Coastal Management was assessed for the followingcriteria:

• Reduced seagrass wrack accumulation

• Maintained HSD, with provisions for access

• Developed the following concept options:• Managed Retreat

• Sand Bypassing

• Sand Bypassing with Buried Seawall

• Groynes (with sand bypassing)

• Nearshore Breakwaters (with sand bypassing)


Design AssumptionsDesign AssumptionsDesign AssumptionsDesign Assumptions

• 50 year timeframe

• Manage hazards within the Boat Harbour Reserve (1km)

• Design has accounted for and included storm erosion

• Assumptions made on breakwater design

• Costs estimated based on similar works in the PerthMetropolitan area

• Allow for preliminaries, contingencies, design andmanagement


Managed RetreatManaged RetreatManaged RetreatManaged Retreat

• Allows shoreline to retreat – minimal management

• Does not meet the criteria of maintaining the HSD


Managed Retreat Managed Retreat Managed Retreat Managed Retreat –––– Considerations Considerations Considerations Considerations

• Access• Vehicle access to be provided over and along the breakwater

extension

• Allow lay down area

• New beach access stairs will need to be relocated to meet criteria

• Proposed pedestrian path re-routed


Managed Retreat Managed Retreat Managed Retreat Managed Retreat ---- ConsiderationsConsiderationsConsiderationsConsiderations

• Wrack accumulations likely to be similar to existing tonorth of the Harbour

• Beach amenity likely to be similar to existing

• Over time, as more rock becomes exposed, may be a less useable beach

• Loss of surf break with Harbour expansion (covered)

• Could consider artificial reef as “replacement” break


Managed Retreat Managed Retreat Managed Retreat Managed Retreat ---- CostsCostsCostsCosts

• Capital and maintenance costs estimated

• NPV completed for all options to allow comparison ofcosts and timing of expenditure (6% discount rate)

• NPV = $1.26M



Sand BypassingSand BypassingSand BypassingSand Bypassing

• Options developed to offset all erosion (original andharbour expansion) in Boat Harbour reserve

• Allowance for bypassing increased for conceptual andcost purposes

• Mobile pumping or trucking both considered feasiblesystems of sand bypassing

• Considered 2 options for sand bypassing:• Option 1 - Sand Bypassing

• Option 2 - Sand Bypassing with a Buried Seawall


Sand Bypassing Sand Bypassing Sand Bypassing Sand Bypassing –––– Option 1Option 1Option 1Option 1

• Pumped or trucked


Sand Bypassing Sand Bypassing Sand Bypassing Sand Bypassing –––– Option 2 (Seawall)Option 2 (Seawall)Option 2 (Seawall)Option 2 (Seawall)

• Pumped or trucked

• With buried seawall


Sand Bypassing ConsiderationsSand Bypassing ConsiderationsSand Bypassing ConsiderationsSand Bypassing Considerations

• Pipeline route could be along breakwater or more directthrough land – would require consideration in planning

• Need to ensure plant access to extraction and disposalareas as well as nominated space for booster pump



• Shoreline response to maintain HSD

• Would fluctuate between bypassing operations

• Allowed a one-off placement of sand to offset stormerosion during 50 year period (for costs)

• Wrack accumulations similar to existing north

• May reduce accumulations further to the south

• Would need to be managed immediately during / afterbypassing

• Beach and surfing amenity may be improved undermobile pumping option. Specific placement would needto be worked through in detailed design and operation.






Sand Bypassing Sand Bypassing Sand Bypassing Sand Bypassing ---- CostsCostsCostsCosts


Sand Nourishment Costs Mobile Pumping Costs Trucking Costs

NPV for Sand Bypassing Options

• Costs broken into nourishment, mobile and trucking

• NPV completed for each, for 2 options

Groynes (with Sand Bypassing)Groynes (with Sand Bypassing)Groynes (with Sand Bypassing)Groynes (with Sand Bypassing)

• 5 groynes of varying lengths constructed

• Sand Bypassing to offset SLR and storm loss


Groynes Groynes Groynes Groynes ---- ConsiderationsConsiderationsConsiderationsConsiderations

• Groyne spacing and length based on desired shorelineposition and design estimates

• Shoreline position will still fluctuate seasonally andinterannually

• Construction proposed at the time of construction ofthe Harbour

• Shoreline response to north same as Managed Retreat

• Risk of wrack accumulation being increased withincompartments – would need careful consideration inmodelling

• This appears to be shown in UWA modelling but is notdiscussed in report


Groynes Groynes Groynes Groynes ---- ConsiderationsConsiderationsConsiderationsConsiderations

• Beach amenity will be improved compared to theexisting and Managed Retreat options

• Visual impact of groynes

• Surf amenity may benefit from groyne construction andbypassing placement but would need furtherassessment


Groynes Groynes Groynes Groynes ---- CostsCostsCostsCosts

• Bypassing allowed at 10 yearly intervals

• NPV of $8.5M


Nearshore Breakwaters (with Bypassing)Nearshore Breakwaters (with Bypassing)Nearshore Breakwaters (with Bypassing)Nearshore Breakwaters (with Bypassing)

• 7 breakwaters constructed with Boat Harbour

• Sand bypassing to offset SLR and storm losses




Nearshore Breakwaters Nearshore Breakwaters Nearshore Breakwaters Nearshore Breakwaters ---- ConsiderationsConsiderationsConsiderationsConsiderations

• Breakwater spacing and length based on desiredshoreline position and design estimates

• Shoreline position will still fluctuate seasonally andinter-annually

• Construction proposed at the time of construction ofthe Harbour

• Sand used as temporary access then to nourishcompartments

• Shoreline response to north same as Managed Retreat

• Risk of wrack accumulation being increased or trappedwithin compartments – would need carefulconsideration in modelling


Nearshore Breakwaters Nearshore Breakwaters Nearshore Breakwaters Nearshore Breakwaters ---- ConsiderationsConsiderationsConsiderationsConsiderations

• Beach amenity will be improved compared to theexisting and Managed Retreat options

• Visual impact of breakwaters

• Surf amenity unlikely to be improved in mostconditions, adding public safety issues


Nearshore Breakwaters Nearshore Breakwaters Nearshore Breakwaters Nearshore Breakwaters ---- CostsCostsCostsCosts

• Bypassing allowed at 10 yearly intervals

• NPV of $11.1M


Evaluation of OptionsEvaluation of OptionsEvaluation of OptionsEvaluation of Options

• Assessed on a Multi-Criteria basis:• Feasibility & Practicality

• Environmental Impacts

• Social Impacts / Community Values (incl beach amenity)

• Capital & Ongoing Costs

• Long term effectiveness (50 years)

• Response to Climate Change

• Reversibility & Adaptability

• Recommended that community consultation iscompleted on the options


Evaluation of OptionsEvaluation of OptionsEvaluation of OptionsEvaluation of Options


Criteria & AssessmentCriteria & AssessmentCriteria & AssessmentCriteria & Assessment


Criteria Used

Assessment



Key Recommendations from Part 3Key Recommendations from Part 3Key Recommendations from Part 3Key Recommendations from Part 3

• Sand Bypassing options recommended for progression

• Investigation of surfing amenity and potential reef lossshould be considered

• Location of pipe routes and booster pump location canbe determined in further design

• Continue camera monitoring of wrack and completejoint assessment of wrack accumulation with metoceanconditions


Thank youThank youThank youThank you



Q & A

Thank you…






� General business� Next Meeting, Evaluation & Close


� Rockwall completion

� Plaque

� Otherbusiness?

General Business







� Next Meeting, Evaluation & Close



Next Meeting

� Early start – to ensure light

� 5pm for a 5:15pm start

� Appropriate gear for weather; site responsibilitiescommunicated at commencement

� Two Rocks Marina commercial lifter area – atgates

� Followed by meeting – marina conditions, userrequirements, options, costing

� Other items as required

Evaluation

� Masterplan expectations/limits


Thank You!

CloseJurien Boat Harbour 9 May 2018

56


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