Coastal Hazards Management Plan Marengo to Skenes Creek · 2012-12-07 · 2.1 Coastal Management...

Coastal Hazards Management Plan

Marengo to Skenes Creek

October 2012

ISO 9001 QEC22878

SAI Global

Department of Sustainability and Environment

Coastal Hazards Management Plan – Marengo to Skenes Creek

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DOCUMENT STATUS

Version Doc type Reviewed

by

Approved

by

Date issued

v04 Final Report GLR TJW 26/10/2012

v03 Final Report GLR TJW 28/08/2012

v02 Draft GLR TJW 19/07/2012

v01 Draft Report GLR TJW 12/07/2012

PROJECT DETAILS

Project Name Coastal Hazards Management Plan – Marengo to

Skenes Creek

Client Department of Sustainability and Environment

Client Project Manager Tammy Smith

Water Technology Project Manager Tim Womersley

Report Authors TJW, EAL

Job Number 2285-01

Report Number R01

Document Name 2285-01_R01v04_ApolloBayCHP.docx

Copyright

Water Technology Pty Ltd has produced this document in accordance with instructions from Department of Sustainability

and Environment for their use only. The concepts and information contained in this document are the copyright of Water

Technology Pty Ltd. Use or copying of this document in whole or in part without written permission of Water Technology

Pty Ltd constitutes an infringement of copyright.

Water Technology Pty Ltd does not warrant this document is definitive nor free from error and does not accept liability for

any loss caused, or arising from, reliance upon the information provided herein.

15 Business Park Drive

Notting Hill VIC 3168

Telephone (03) 9558 9366

Fax (03) 9558 9365

ACN No. 093 377 283

ABN No. 60 093 377 283



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TABLE OF CONTENTS

Glossary v

1. Introduction ....................................................................................................................... 1

1.1 Study Area .......................................................................................................................... 2

2. Study Context .................................................................................................................... 3

2.1 Coastal Management Policy Framework ............................................................................. 3

2.2 Stakeholders ....................................................................................................................... 3

2.3 Coastal Processes ............................................................................................................... 4

2.3.1 Coastal Geomorphology & Processes .................................................................................. 4

2.3.2 Historical Shoreline Change ................................................................................................ 7

2.3.3 Historical Coastal Hazard Impacts ....................................................................................... 7

3. Risk Identification ............................................................................................................ 13

3.1 Asset Audit ....................................................................................................................... 13

3.1.1 Great Ocean Road............................................................................................................. 13

3.1.2 Barwon Water Assets ....................................................................................................... 14

3.1.3 OCC Assets ....................................................................................................................... 14

3.1.4 Heritage Listed Trees ........................................................................................................ 14

3.1.5 Stormwater Drainage Network ......................................................................................... 14

3.1.6 Apollo Bay Harbour........................................................................................................... 14

3.2 Coastal Hazards ................................................................................................................ 16

3.2.1 Coastal Inundation Hazards .............................................................................................. 16

3.2.2 Coastal Erosion Hazards .................................................................................................... 20

4. Risk Analysis..................................................................................................................... 24

4.1 Risk Analysis Method ........................................................................................................ 24

4.1.1 Likelihood Definitions ....................................................................................................... 24

4.1.2 Consequence Definitions .................................................................................................. 25

4.1.3 Risk Ranking ..................................................................................................................... 27

4.2 Risk Analysis Results ......................................................................................................... 27

4.2.1 Mounts Bay ...................................................................................................................... 27

4.2.2 Apollo Bay ........................................................................................................................ 30

4.2.3 Wild Dog Creek ................................................................................................................. 33

4.2.4 Skenes Creek .................................................................................................................... 36

5. Risk Treatment ................................................................................................................. 39

5.1 Mounts Bay ...................................................................................................................... 39

5.2 Apollo Bay ........................................................................................................................ 41

5.3 Wild Dog Creek ................................................................................................................. 44

5.4 Skenes Creek .................................................................................................................... 45

6. Monitoring and Review .................................................................................................... 45

7. Bibliography ..................................................................................................................... 46



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LIST OF FIGURES

Figure 1-1 CHP Methodology and Scope .................................................................................... 1

Figure 1-2 Study Area Extent and Coastal Compartments .......................................................... 2

Figure 2-1 Overview of Coastal Processes and Geomorphology ................................................. 6

Figure 2-2 Shoreline Erosion Scarp Following Storm Event at Mounts Bay (T. Stuckey) .............. 8

Figure 2-3 Coastal Erosion Impinging on Car Park at Mounts Bay (T. Stuckey) ............................ 9

Figure 2-4 Coastal Inundation Impacting the Great Ocean Road in Apollo Bay (G. Mc Pike 2005)

............................................................................................................................... 10

Figure 2-5 Coastal Erosion Impacting Car Parks and Walking Paths in Apollo Bay () .................. 10

Figure 2-6 Elevated Coastal Water Levels Due to Storm Tide and Wave Setup at Wild Dog Creek

(D. Webley, 2008) ................................................................................................... 11

Figure 2-7 Erosion Associated with the Dynamic Interaction of Wild Dog Creek and the Coastal

Processes (D. Webley, 2009) ................................................................................... 11

Figure 2-8 Coastal Erosion Impacts to Beach Access and Adjacent to Barwon Water Assets at

Skenes Creek (G McPike, 2011) ............................................................................... 12

Figure 3-1 Overview of GIS Asset Database .............................................................................. 15

Figure 3-2 Coastal Inundation Hazard Extents .......................................................................... 19

Figure 3-3 Coastal Erosion Hazard Extents ............................................................................... 23

Figure 4-1 Mounts Bay Coastal Asset Risk Profiles ................................................................... 29

Figure 4-2 Apollo Bay Coastal Asset Risk Profiles ..................................................................... 32

Figure 4-3 Wild Dog Creek Coastal Asset Risk Profiles .............................................................. 35

Figure 4-4 Skenes Creek Coastal Asset Risk Profiles ................................................................. 38

LIST OF TABLES

Table 2-1 Overview of Agencies with Assets and or Management Responsibilities in the Coastal

Zone ......................................................................................................................... 3

Table 3-1 Adopted Widths of Reduced Bearing Capacity ........................................................ 14

Table 3-2 AEP Storm Tide Levels Incorporating Mean Sea Level Scenarios (CSIRO 2009) ......... 16

Table 3-3 Peak Coastal Inundation Elevation Scenarios for the Study Area ............................. 17

Table 3-5 Adopted Short-term Erosion Demand Extents for the Study Area............................ 22

Table 3-6 Coastal Erosion Scenarios for the Study Area .......................................................... 22

Table 4-1 Risk Likelihood Definitions ...................................................................................... 25

Table 4-2 Risk Consequence Definitions ................................................................................. 26

Table 4-3 Risk Assessment Matrix .......................................................................................... 27

Table 4-4 Risk Profile Definition.............................................................................................. 27

Table 4-5 Mounts Bay Coastal Asset Risk Profiles ................................................................... 28

Table 4-6 Apollo Bay Coastal Asset Risk Profiles ..................................................................... 31

Table 5-1 Proposed Mitigation Strategies and Priorities for Mounts Bay Coastal

Compartment ......................................................................................................... 39

Table 5-2 Sand Carting Cost Estimate from Bunbury Point Groyne to Mounts Bay .................. 41

Table 5-5 Offshore Sediment Bypassing Cost Estimate ........................................................... 42

Table 5-6 Sand Carting Cost Estimates from Bunbury Point to Apollo Bay ............................... 42

Table 5-5 Proposed Mitigation Strategies and Priorities for Apollo Bay Coastal Compartment

............................................................................................................................... 43



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GLOSSARY

Accretion The accumulation of material which may eventually lead to the creation of new

land mass

Australian Height Datum

(AHD)

A common national plane of level corresponding approximately to mean sea level

ARI Average Recurrence Interval

AEP Annual Exceedance Probability: The measure of the likelihood (expressed as a

probability) of an event equalling or exceeding a given magnitude in any given year

Astronomical tide Water level variations due to the combined effects of the Earth’s rotation, the

Moon’s orbit around the Earth and the Earth’s orbit around the Sun

Beach Berm A plateau often found at the back of the primary sand dune, separating the beach

area from other geological features further inshore

Chart Datum Common datum for navigation charts. Typically relative to Lowest Astronomical

Tide

Design Wave The wave conditions for a design conditions, for example, the 100 year design wave

is representative of a wave which could be expected to occur, on average once in a

100 year period

Diurnal A daily variation, as in day and night.

Ebb Tide The outgoing tidal movement of water resulting in a low tide.

Exceedance Probability The probability of an extreme event occurring at least once during a prescribed

period of assessment is given by the exceedance probability. The probability of a 1

in 100 year event (1% AEP) occurring during the first 25 years is 22%, during the

first 50 years the probability is 39% and over a 100 year asset life the probability is

63%

Flood Tide The incoming tidal movement of water resulting in a high tide

Foreshore The area of shore between low and high tide marks and land adjacent thereto

Geomorphology The study of the origin, characteristics and development of land forms

Holocene The period beginning approximately 12,000 years ago. It is characterised by

warming of the climate following the last glacial period and rapid increase in global

sea levels to approximately present day levels.

HAT Highest Astronomical Tide: the highest water level that can occur due to the effects

of the astronomical tide in isolation from meteorological effects

MHHW Mean Higher High Water: the mean of the higher of the two daily high waters over

a long period of time. When only one high water occurs on a day this is taken as

the higher high water

Hs (Significant Wave

Height)

Hs may be defined as the average of the highest 1/3 of wave heights in a wave

record (H1/3), or from the zeroth spectral moment (Hm0)

Intertidal Pertaining to those areas of land covered by water at high tide, but exposed at low

tide, eg. intertidal habitat

Littoral Zone An area of the coastline in which sediment movement by wave, current and wind

action is prevalent

Littoral Drift Processes Wave, current and wind processes that facilitate the transport of water and

sediments along a shoreline



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MSL Mean Sea Level

Neap Tides

Neap tides occur when the sun and moon lie at right angles relative to the earth

(the gravitational effects of the moon and sun act in opposition on the ocean).

Pleistocene The period from 2.5M to 12,000 years before present that spans the earth's recent

period of repeated glaciations and large fluctuations in global sea levels

Semi-diurnal A twice-daily variation, eg. two high waters per day

Spring Tides Tides with the greatest range in a monthly cycle, which occur when the sun, moon

and earth are in alignment (the gravitational effects of the moon and sun act in

concert on the ocean)

Storm Surge The increase in coastal water levels caused by the barometric and wind set-up

effects of storms. Barometric set-up refers to the increase in coastal water levels

associated with the lower atmospheric pressures characteristic of storms. Wind

set-up refers to the increase in coastal water levels caused by an onshore wind

driving water shorewards and piling it up against the coast

Storm tide Coastal water level produced by the combination of astronomical and

meteorological (storm surge) ocean water level forcing

Tidal Planes

A series of water levels that define standard tides, eg. 'Mean High Water Spring'

(MHWS) refers to the average high water level of Spring Tides

Tidal Range

The difference between successive high water and low water levels. Tidal range is

maximum during Spring Tides and minimum during Neap Tides

Tides

The regular rise and fall in sea level in response to the gravitational attraction of

the Sun, Moon and Earth

Velocity Shear The differential movement of neighbouring parcels of water brought about by

frictional resistance within the flow, or at a boundary. Velocity shear causes

dispersive mixing, the greater the shear (velocity gradient), the greater the mixing.

Wave runup The vertical height above the still water level a wave will “run up” over the face of

a sloping wall or beach profile. Run up varies with structure or beach shape and

roughness, the depth and slope of the bed next to the beach or structure and the

actual wave conditions.

Wave setup The super elevation of nearshore water levels due to the transport of momentum

associated with pressure and velocity fluctuations of breaking waves propagating in

a shoreward direction

Wind Shear

The stress exerted on the water's surface by wind blowing over the water. Wind

shear causes the water to pile up against downwind shores and generates

secondary currents



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1. INTRODUCTION

Water Technology was engaged by the Department of Sustainability and Environment (DSE) to

prepare a Coastal Hazards Management Plan (CHP) for the coastline between Skenes Creek and

Marengo, including Apollo Bay, in south western Victoria. The CHP has employed a risk

management methodology in accordance with the Victorian Coastal Hazard Guide (). The risk

management methodology provides a strategic framework for identifying and responding to coastal

hazard risks in the study area and to develop a plan for mitigating risks to key assets and

infrastructure over a 10 year management time frame.

The risk management methodology adopted comprises the following main components and tasks as

displayed below:

Figure 1-1 CHP Methodology and Scope

Establish Context

Risk Identification

Risk Analysis

Risk Treatment

• Review of key strategic drivers, policies and

stakeholder agencies relevant to the

development of the CHP.

• Overview of existing coastal process and hazard

risks within the study area

• Identification of the main sources of coastal

hazard risk in the study area and determination

of the extent and magnitude of the hazards

considering a 10 year management timeframe

• Identification of the type, extent and value of

assets (built, environmental, historic) potentially

at risk from coastal hazards in the study area

• Development of risk profiles for key assets in the

study area based on the evaluation of the

product of the likelihood and consequence of the

potential coastal hazard impacts to these assets.

• Evaluation and prioritisation of mitigation

measures to treat unacceptable coastal hazard

risks to assets



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1.1 Study Area

The CHP has been developed considering the following four coastal compartments within the study

area:

• Mounts Bay (Marengo to the southern boundary of Apollo Bay Harbour (Point Bunbury))

• Apollo Bay (Northern boundary of Apollo Bay Harbour to just beyond Marriners Lookout

Road

• Wild Dog Creek (Just beyond Marriners Lookout Road to the end of the beach at the

entrance of Wild Dog Creek.

• Skenes Creek (3 kilometre shoreline between Wild Dog Creek and Skenes Creek Caravan

Park)

Figure 1-2 displays the extent of the study area and four main coastal compartments.

Figure 1-2 Study Area Extent and Coastal Compartments



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2. STUDY CONTEXT

The context in which the CHP for the study area has been developed has been summarised in the

following sections.

2.1 Coastal Management Policy Framework

The Coastal Management Act 1995 is the key Act guiding use and development of the coast. The Act

aims to provide for co-ordinated strategic planning and management for the coast. To achieve these

objectives the Act directs the Victorian Coastal Strategy 2008 (VCS) to provide for long-term planning

of the Victorian coast.

The VCS provides a comprehensive integrated management framework for the coast of Victoria. The

CHP developed in this study takes into consideration the hierarchy of principles approach and

associated policy directions provided in the VCS.

Coastal Action Plans (CAP) are regional to local scale plans that aim to further develop the broad

principles and priorities of the VCS to provide long term strategic directions for particular locations

and sets of issues on the Victorian coast. A CAP for the Skenes Creek to Marengo has been

completed by the Colac Otway Shire under the guidance of the Western Coastal Board. The CAP

addresses a number of pressures and issues affecting the coastline between Skenes Creek and

Marengo and provides a series of prioritised recommendations for protecting and managing the

coastline. The recommendations contained within the Skenes Creek to Marengo CAP have been

incorporated into the development of the CHP for Apollo Bay.

2.2 Stakeholders

A following range of agencies have assets in the study area and/or are involved in planning and

management in the coastal zone. The relevant stakeholders/agencies and their roles and

responsibilities within the study area are summarised in Table 2-1.

Table 2-1 Overview of Agencies with Assets and or Management Responsibilities in the

Coastal Zone

Agency Role/Responsibility

Western Coastal Board Strategic planning for the coastline under the Coastal Management Act 1995

Vic Roads Great Ocean Road – planning and works

Colac Otway Shire Council Stormwater, land use planning, traffic, works on minor roads, managing Apollo

Bay Harbour

Department of

Sustainability and

Environment (DSE)

DSE has responsibilities under the Coastal Management Act 1995 as delegated

by the Minister for Environment and Climate Change , and further responsibility

on behalf of Government as the landowner of Crown land in Victoria. Under the

Crown land (Reserves) Act 1978 (the Act) the Minister for Environment and

Climate Change can delegate management responsibilities to committees of

management. DSE provides advice and guidance to Committees and may make

grant funding available.

Otway Foreshore

Committee of Management

Operation and management of coastal crown land including recreational

reserves and camping grounds

Barwon Water Water supply and sewerage assets

Corangamite Catchment

Management Authority

Catchment management, planning and waterway works



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2.3 Coastal Processes

The study area has been subject to a number of previous coastal process studies to identify potential

solutions to the sedimentation issues at the entrance to the Apollo Bay Harbour and to develop an

improved understanding of existing coastal erosion and inundation hazards more generally within

the study area. The following previous relevant coastal process investigations have been undertaken

in the study area

• Vantree Pty Ltd (1996) Apollo Bay Coastal Processes

• Vantree Pty Ltd (1997) Mounts Bay Beach: Report on Coastal Erosion

• Coastal Engineering Solutions (2005) Apollo Bay Sand Study

• GHD (2009) Apollo Bay Sand and Dredging Options Study

A considerable body of knowledge on the coastal processes in the study area therefore currently

exists. The following provides an overview of the main findings of these previous studies in the

context of understanding the causes and potential extent of the coastal hazard risks in the study

area.

2.3.1 Coastal Geomorphology & Processes

Apollo Bay is located at the foot of the Otway Ranges which consist of uplifted Cretaceous

sedimentary formations reaching elevations of approximately 300m above sea level behind Apollo

Bay. The Cretaceous sediments are however rich in feldspar rather than quartz and the erosion of

these formations do not supply appreciable quantities of sand sized sediments to the coastline. The

littoral sediments comprising the sand bars, beaches and dunes in the region are therefore derived

from sediments drifted shoreward from the floor of Bass Strait following the end of the last glacial

phase and subsequent marine transgression.

The main features of the coastal geomorphology and processes of the study are displayed in Figure

2-1 and discussed below.

Mounts Bay beach is a component of a Holocene barrier that has built out across the floodplain of

the Barham River by longshore drifting of sediment. The Great Ocean Road extends along the crest

of this Holocene barrier formation. Behind the present day barrier, a series of abandoned lagoons,

tidal channels and early barrier formations indicate the present barrier most likely formed recently

following relative sea level fall during the late Holocene (<5,000 years before present).

Between Apollo Bay and Wild Dog Creek, a continuous, crenulate shaped bluff exists behind the

present day shoreline, indicating the location of an earlier cliffed shoreline that most likely occurred

along this coastline during relatively higher sea level conditions of the mid Holocene (6,000-7,000

years before present). The relative fall in mean sea levels since the mid Holocene has facilitated the

development of the present day dune and beach system in front of this earlier cliffed coastline.

The beach systems within the study area are composed of medium to fine grained, calcareous sand.

Previous analysis undertaken by CES (2005) estimated that the net sediment transport potential is

approximately 80,000m3/yr towards the north-east.

Following construction of the Apollo Bay Harbour, the longshore transport around Point Bunbury

was captured by the breakwater and Harbour. The construction of the harbour also created a wave

shadow along the beach in its immediate lee to the north. The reduction in wave energy along the

shoreline in the lee of the breakwater, as well as likely local changes to wave directions due to wave

diffraction around the breakwaters, resulted in a reduction in the potential north-east longshore

transport of sand. The reduction in the longshore sediment supply along the Apollo Bay shoreline

has resulted in significant accretion of sand in the southern corner of the beach at Apollo Bay,



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extending north to approximately Cawood Street. This accretion has been further enhanced by

regular sand bypassing of the Harbour entrance which has deposited sand within the wave shadow

zone in the lee of the Harbour.

The disruption of the longshore sand transport continuity along the beach at Apollo Bay caused by

the construction of the Harbour has contributed to longterm shoreline recession observed along the

beach at Apollo Bay beyond Cawood Street to the north of the Harbour.



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Figure 2-1 Overview of Coastal Processes and Geomorphology



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2.3.2 Historical Shoreline Change

Analysis of historical aerial photography of the study area has been undertaken previously CES

(2005) and Vantree (1996). The analysis identified and mapped the extent of the historical shoreline

changes in the study area. The following summarises the main conclusions drawn from the previous

analysis:

Mounts Bay

• Major changes in the position of the vegetated shoreline have not been observed in this

shoreline compartment, except in the vicinity of the Barham River entrance

• The vegetated shoreline extent has however tended to retreat, particularly since the mid

1980’s.

• The average rate of recession of the vegetated shoreline extent was estimated at

approximately 9cm/yr.

Apollo Bay

• Significant accretion and subsequent advancement of the shoreline south of Cawood Street

has occurred at an average of approximately 83cm/yr. However, since the mid 1980’s the

shoreline has receded slightly, indicating the period of shoreline adjustment following the

construction of the Harbour may now be largely complete

• North of Cawood Street, the vegetated shoreline extent has been receding by approximately

2cm/yr on average. More rapid recession has historically been observed at the location of

the stormwater outfalls.

Wild Dog Creek

• North of Mariners Road to the groyne at Wild Dog Creek, the vegetated shoreline extent has

advanced at an average rate of approximately 49cm/yr. The groyne compartment at Wild

Dog Creek is however now full and sand is likely to be bypassing around the groyne such that

ongoing advancement of the shoreline is considered unlikely.

• Wild Dog Creek beach is very dynamic due to the interaction of the Wild Dog Creek

streamflows and the coastal processes. This results in significant changes to the alignment

and location of the creek entrance into Bass Strait along the beach from month to month.

Skenes Creek

• Historical shoreline changes at Skenes Creek have not previously been mapped from

historical aerial photography. It is however understood that fencing, formalisation of beach

access and revegetation have resulted in a more resilient shoreline extent which has only

experience relatively minor changes following large storm events.

2.3.3 Historical Coastal Hazard Impacts

Sections of the study area and associated assets and infrastructure have historically been exposed to

coastal hazard impacts. The coastal impacts have generally been associated with large storm tide

events in combination with wave action that has resulted in significant shoreline erosion as well as

inundation of low lying areas.

The following main coastal impacts have been previously observed and documented at Apollo Bay:



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Mounts Bay

Assets and infrastructure located close to the shoreline of Mounts Bay have historically experienced

some moderate impacts associated with short term, storm related erosion. Some examples of the

impact of historical storm related erosion at Mounts Bay are displayed in the photos provided by T.

Stuckey below.

Specific impacts to assets and infrastructure associated with these hazards have included the

following at Mounts Bay:

• A toilet block located between the Great Ocean Road and the Mounts Bay shoreline was

threatened by shoreline erosion. In an attempt to protect the toilet block, rock was dumped

on the shoreline in front of the toilet block.

• A sewer rising main has historically been exposed in the dune scarp following large erosion

events. It is understood that this sewer main has been decommissioned.

• A carpark and a number of beach access points have been impacted by erosion of the

shoreline.

• A number of traffic signs associated with the Great Ocean Road have been impacted and/or

lost due to erosion of their foundations

Figure 2-2 Shoreline Erosion Scarp Following Storm Event at Mounts Bay (T. Stuckey)



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Figure 2-3 Coastal Erosion Impinging on Car Park at Mounts Bay (T. Stuckey)

Apollo Bay

Assets and infrastructure located close the shoreline of Apollo Bay have historically experience some

relatively significant impacts associated with storm related erosion as well as inundation. Some

examples of the impact of historical storm related erosion and inundation at Apollo Bay are

displayed in the figures below.

Historical impacts to assets and infrastructure associated with these hazards have included the

following at Apollo Bay:

• The sewer rising main between Skenes Creek and Apollo Bay has been exposed historically

near Marriners Lookout Road.

• Significant sections of the foreshore walking path have been repeatedly lost following major

erosion events

• A number of long standing Monterey Cypress Trees (Cupresses macrocarpa) have had their

roots undermined following major erosion events

• A carpark and a number of beach access points have been impacted by erosion.

• Significant inundation of the Great Ocean Road has occurred near Marriners Lookout Road

due to wave runup and overtopping.



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Figure 2-4 Coastal Inundation Impacting the Great Ocean Road in Apollo Bay (G. Mc Pike

2005)

Figure 2-5 Coastal Erosion Impacting Car Parks and Walking Paths in Apollo Bay ()

Wild Dog Creek

Observations on the potential extent of the coastal hazard at Wild Dog Creek have been drawn from

photos and observations provided by David Webley, an estuary watch volunteer for the CCMA for

the Wild Dog Creek Estuary.

The morphology of the beach at Wild Dog Creek is highly variable due to the complex interaction of

the Wild Dog Creek streamflows and the coastal processes. These interactions result in rapid



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changes to the creeks alignment along the beach in response to changing streamflow rates and

prevailing wave and sediment transport directions. Changes to the creek alignment and the lowering

of the beach berm can potentially result in erosion and inundation impinging close to the Great

Ocean Road and/or its foundations as well as exposing the groyne to the eastern end of the Wild

Dog Creek beach in this coastal compartment.

Figure 2-6 Elevated Coastal Water Levels Due to Storm Tide and Wave Setup at Wild Dog

Creek (D. Webley, 2008)

Figure 2-7 Erosion Associated with the Dynamic Interaction of Wild Dog Creek and the Coastal

Processes (D. Webley, 2009)



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Skenes Creek

Limited information on the long term exposure of this coastal compartment to coastal hazards was

identified during the course of the study. Some impacts to beach access ramps and fences have

been observed near the caravan park historically as displayed in Figure 2-8.

Figure 2-8 Coastal Erosion Impacts to Beach Access and Adjacent to Barwon Water Assets at

Skenes Creek (G McPike, 2011)



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3. RISK IDENTIFICATION

To facilitate the development of an informed and strategic plan for managing future coastal hazards

in the study area, the following analysis has been undertaken:

• An audit of the type and extent of the assets and infrastructure potentially at risk in the

study area has been undertaken and assets have been incorporated into a GIS asset

database.

• The main sources of the coastal hazard risks in the study area have been identified and the

potential extent and magnitude of the coastal hazards have been estimated for a range of

probability scenarios considering a 10 year management timeframe

3.1 Asset Audit

The following summarises the type of assets that have been identified as potentially at risk for the

study area and the method for obtaining/assimilating these assets into the GIS asset database. An

overview of the GIS database of all assets potentially at risk from coastal hazards is displayed in

Figure 3-1.

3.1.1 Great Ocean Road

The Great Ocean Road is one of Victoria’s most popular tourist destinations and attracts visitors

from around Australia and Internationally. The Great Ocean Road is the principle piece of transport

infrastructure in the study area and is vital to supporting the tourism and economic activity in the

study area. The Great Ocean Road also serves an important emergency management function. The

Great Ocean Road is zoned Road Zone – Category 1 and differs from other local roads in the study

area in that planning and works associated with the Great Ocean Road are managed by VicRoads.

The Great Ocean Road has been digitised as polygon feature from aerial imagery for this study. The

spatial extent of the Great Ocean Road has been interpreted as covering a width of the tarmac plus

one metre either side.

In addition to the Great Ocean Road, an asset relating to the competence of the Great Ocean Road

foundations has been delineated to assist in the risk analysis. The structural incompetence of

unconsolidated sand is such that a zone of reduced bearing capacity extends landward of a shoreline

erosion escarpment. The stability of the roads foundations located within a zone of reduce bearing

capacity will be compromised unless appropriate measures have been considered in the design of

the road foundations. The width of the zone of reduced bearing capacity is influenced by a number

of factors including the angle of repose of the dune sand, the height of the erosion scarp and the

presence of water table gradients. Stability factors relating to determination of these zones have

been defined by studies undertaken by Nielsen et al (1992).

For the purposes of the risk analysis of the study area, the widths of reduced bearing capacity

seaward of the edge of the Great Ocean Road have been delineated for different dune scarp heights

and varied based on the DTM of the study area. The widths of reduced bearing capacity adopted for

the risk analysis are summarised in Table 3-1.



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Table 3-1 Adopted Widths of Reduced Bearing Capacity

Erosion Scarp Height (m) Indicative Zone of Reduced Bearing Capacity

Width (m)

3 4

5 7

3.1.2 Barwon Water Assets

Barwon Water has a large number of assets in the study area associated with the provision and

treatment of potable water and sewerage respectively. A number of these assets have historically

been impacted by coastal hazards or are potentially at risk in the future. The potable water and

sewerage network for the study area was provided by Barwon Water as linear features in a GIS

format. The pump station at Skenes Creek was digitised from aerial imagery for the study.

3.1.3 OCC Assets

The OCC is responsible for the management of a range of foreshore assets in the study area.

Significant assets managed by the OCC and at risk of coastal hazard impacts include the following:

• Skenes Creek Camping Ground and associated toilet blocks, office, BBQ facilities etc

• Pedestrian pathways and fencing

• Foreshore parking areas

• Public toilets, barbecue facilities, picnic tables, signs and shelters

These assets were identified from aerial imagery and digitised for inclusion into the GIS database.

3.1.4 Heritage Listed Trees

An avenue of Monterey Cypress trees, planted in the 1890’s, provide a distinctive ‘gateway’ to

Apollo Bay and these trees are considered to have heritage value. These trees were identified from

the aerial photography and incorporated into the GIS database.

3.1.5 Stormwater Drainage Network

A total of 10 stormwater outfalls were identified in the study area. The majority of these are located

along the Apollo Bay shoreline. The Colac Otway Shire Council provided the stormwater drainage

network including pits, pipes and outfalls in a GIS format. Pipes and outfalls were delineated as

linear features. Pits were delineated as point features.

3.1.6 Apollo Bay Harbour

The Apollo Bay Harbour is the only working port and safe haven between Queenscliff and

Warrnambool. The harbour services a small commercial fishing fleet, associated fisherman’s

cooperative and incorporates a boat ramp facility and moorings for recreational vessels. The harbour

was created initially by the construction of a southern breakwater in the 1950’s with subsequent

extensions and modifications to the harbour and breakwaters undertaken since in an attempt to

limit siltation of the harbour and entrance and to improve protection to moored vessels.

The Apollo Bay Harbour is zoned as Public Park and Recreation Zone. The Apollo Bay Harbour is

operated by the Otway Colac Council which includes management of maintenance dredging

activities.



2285-01 / R01 v04 - 26/10/2012 15

Figure 3-1 Overview of GIS Asset Database



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3.2 Coastal Hazards

An analysis of the potential extent of coastal hazards has been undertaken for the study area. The

coastal hazard analysis provides the basis for informing the extent of the risk to assets and

infrastructure in the study area and for prioritising and evaluating measures to treat or mitigate

these risks.

Estimation of the coastal hazard extents has been undertaken using conventional coastal

engineering methods and techniques and existing coastal information and data for the study area. It

should be recognised that the processes giving rise to coastal hazards are extremely complex and

significant uncertainty exists in the estimation of their potential extents.

The objective of the analysis of coastal hazard is therefore to provide a precautionary, risk based

assessment of their potential extent, considering an approximate 10 year management timeframe.

The following sections summarise the analysis undertaken to identify potential coastal hazard

extents and their probabilities in the study area. The coastal hazard analysis includes consideration

of both coastal erosion and inundation hazards.

3.2.1 Coastal Inundation Hazards

The potential extent of the coastal inundation in the study area have been determined by adoption

of available storm tide recurrence interval estimates for Apollo Bay and calculations of potential

wave setup and run-up at and within the coastal compartments in the study area.

The different coastal water level estimates and calculations have been combined to develop a series

of peak coastal inundation elevations for the study area that are considered to have varying

probabilities of occurrence over the 10 year management timeframe.

Storm Tide

Estimates of 10% and 1% Annual Exceedance Probability (AEP) extreme coastal water levels (storm

tides) at Apollo Bay have been developed by the CSIRO (CSIRO, 2009) for different planning and sea

level rise scenarios as part of the Department of Sustainability’s Future Coasts Program. The

estimated levels under existing sea level conditions for the 10% and 1% AEP storm tide are displayed

in Table 3-2 for Apollo Bay.

Table 3-2 AEP Storm Tide Levels Incorporating Mean Sea Level Scenarios (CSIRO 2009)

Storm Tide Scenario Storm Tide Level

(m AHD)

Apollo Bay (10% AEP) 1.10

Apollo Bay (1% AEP) 1.42

Wave Setup & Run-up

The study area coastline is exposed to the high swell wave energy from Bass Strait. The action of this

wave energy can contribute significantly to water levels in the near shore zone along the study area.

Wave setup is the super elevation of nearshore water levels due to the transport of momentum

associated with pressure and velocity fluctuations of breaking waves propagating in a shoreward

direction. Wave runup is the vertical height above the still water level a wave will “run up” the face

of a sloping wall or beach profile. Run up varies with structure or beach shape and roughness, the

depth and slope of the bed next to the beach or structure and the actual wave conditions.



2285-01 / R01 v04 - 26/10/2012 17

To enable estimation of the contribution of wave action in the near shore zone to local coastal water

levels, in terms of both wave setup and extent of wave run-up, estimates of design wave conditions

offshore of the study area have been developed from the previous wave climate analysis undertaken

by CES (CES, 2006).

The amount of wave setup that could be expected under various design offshore wave conditions

can be determined from the excess momentum flux due the presence of waves at the shoreline

using linear wave theory. The theoretical solutions have been extensively validated to field

measurements by Guza and Thornton (1981). In general, the wave setup can be estimated as

approximately 20% of the design offshore significant wave height.

The propagation of waves onto ‘dry’ beach is referred to as wave run-up and is defined as the

vertical displacement of the shoreline, measured relative to the still water level, due to the swash

motions of waves. Comprehensive studies of run-up on natural beaches has been undertaken by

Holman (1986) and Nielsen and Hanslow (1991). These studies defined the parameter R2% which is

the run-up height exceeded by 2% of the wave run-up events on the shoreline. The relationship

between R2% and the incident wave conditions and beach slope was determined as follows:

R2% = 0.366g1/2

tanβH01/2

T

where:

g = acceleration due to gravity

tanβ=– average shoreline gradient

H0 = deep water significant wave height

T = spectral peak wave period

The adopted storm tide and design wave conditions for three probability scenarios are summarised

along with the resulting peak coastal inundation elevation for relevant sections of the study area in

Table 3-3. The peak coastal water level estimates displayed in Table 3-3 have been mapped to the

coastal DEM to provide an estimate of the potential extents of coastal inundation in the study area

for each scenario and are displayed in Figure 3-2.

Table 3-3 Peak Coastal Inundation Elevation Scenarios for the Study Area

Probability Coastal

Inundation

Scenario

Mounts Bay

(m AHD)

Apollo Bay

(m AHD)

Wild Dog Creek

(m AHD)

Skenes Creek

(m AHD)

Almost

Certain

10% AEP storm

tide + 5m Hso,

14s Tp 3.61 2.11-3.44 3.61 3.61

Unlikely 1% AEP storm

tide + 5m Hso,

14s TP

3.91 2.41-3.74 3.91 3.91

Rare 1% AEP storm

tide + 8m Hso,

14s TP 4.59 2.64-4.36 4.59 4.59

The coastal inundation extents displayed in Figure 3-2 show that coastal inundation extents are

largely confined to the coastal foreshore fringe. The analysis is however unable to account for the

potential increase in inundation extents that could occur due to shoreline erosion. It is noted that

the analysis displayed in Figure 3-2 indicates that minor inundation of the Great Ocean Road near



2285-01 / R01 v04 - 26/10/2012 18

the intersection of Marriners Lookout Road is predicted under the ‘Almost Certain’ inundation

scenario. This location has historically observed multiple, minor inundation events due to wave run-

up and overtopping onto the Great Ocean Road. This is considered to provide some degree of

validation to the coastal inundation hazard levels and extents developed in this analysis.



2285-01 / R01 v04 - 26/10/2012 19

Figure 3-2 Coastal Inundation Hazard Extents



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3.2.2 Coastal Erosion Hazards

The potential extent of the coastal erosion in the study area have been determined by adoption of

previously determined historical shoreline recession rates and additional calculations based on

theoretical models of potential shoreline erosion for sandy shorelines in the study area.

The different coastal erosion hazard estimates and calculations have been combined to develop a

series of coastal erosion extents for the study area considered to have varying probabilities of

occurrence over the 10 year management timeframe.

Longterm Shoreline Recession Rates

Estimates of longterm shoreline recession rates for the study area have been developed. The

recession rates are considered to have a range of potential probabilities of occurring over a 10 year

management timeframe.

Long term shoreline recession with a high probability of occurring over a 10 year management

timeframe have been adopted from the historical aerial photographic analysis undertaken by CES

(2006). The extent of long term underlying recession of the shorelines for each coastal compartment

in the study area has been inferred from the analysis undertaken by CES.

Where the coastline has historically accreted (advanced) due to construction of coastal structures

such as the Harbour and groyne at Wild Dog Creek, the future response of the shoreline has been

assumed to be equivalent to the more recent trends in the shoreline position observed over the last

decade. The average annual shoreline recession rates determined by the CES study have been

factored over a 10 year management timeframe. Table 3-4 displays the estimated extent of the long

term shoreline recession considered to have a high probability of occurring (‘Almost Certain’) over a

10 year management timeframe.

More conservative estimates of the potential rates of shoreline recession in the study area have

been developed by consideration of equilibrium shoreline profile theory. Equilibrium profile theory

assumes that where all else remains equal, such that the shoreline is neither gaining nor losing

significant volumes of sediment, a rise in relative sea level will lead to erosion as wave action erodes

the beach face and transports sediment offshore. Over time, this process translates the previous

shoreline profile shoreward and upward in response to the relative higher sea levels. The process

results in the redistribution of sediment across the profile but does not lead to net gain or loss of

sediment. The equilibrium profile model was first suggested by Bruun (1962) and has been expanded

and modified upon by others.

A number of parameters are required to enable estimates of potential long term shoreline recession

rates to be determined using equilibrium profile theory for the study area. These are discussed

below:

Sea Level Rise

Global sea levels rose approximately 0.17m during the 20th Century (Reference). The global rate of

sea level rise between 1950 and 2000 was 1.8mm/yr based on tidal gauge data (Reference). Satellite

altimeter data estimates the rate has exceeded 3mm/yr(Reference). The rate of sea level rise

estimated from the Australian Baseline Sea Level Monitoring Project station at Lorne is

approximately 2.8mm/yr.

Eustatic sea level rise due to climate change and thermal expansion of the worlds oceans are

projected to result in increases in mean sea level of between 0.4 – 1.2 m by the end of this century,

however, much of this increase is expected in the second half of this century.

Over the next approximate 10 years, an increase in mean sea level of approximately 2.8cm could be

therefore be expected by extrapolating the existing rate of sea level rise observed at Lorne.



2285-01 / R01 v04 - 26/10/2012 21

Depth of Closure

The depth of closure determines the offshore extent to which the shoreline profile adjustment due

to sea level rise is considered to extend offshore. The estimates of shoreline recession using

equilibrium theory are therefore quite sensitive to the assumed depth of closure of the shoreline

profile. The depth of closure for the study area shorelines has been determined from an estimate of

the significant wave height that could be exceeded for approximately 12 hours per year based on the

previous wave climate analysis undertaken by CES (2006). This wave height has been estimated at

approximately between 5 and 7m significant. The resulting depth of closure for the study area

shoreline profiles has been estimated at between 10.7 and 16.5m based on this wave height and

using the relationship developed by (Hallermeier, 1978).

The two depth of closure estimates for the shoreline profiles in the study area have been used to

develop two long term shoreline recession scenarios based on equilibrium shoreline theory that are

considered to have low (‘Unlikely’) and very low (‘Rare’) probabilities of occurring over the 10 year

management timeframe.

Table 3-4 displays the estimated extent of the long term shoreline recession derived from the

equilibrium profile for two probability scenarios.

Table 3-4 Estimated Longterm Shoreline Recession Extents and Probabilities for the Study

Area

Probability Mounts Bay

(m)

Apollo Bay

(m)

Wild Dog Creek

(m)

Skenes Creek

(m)

Almost Certain 0.9m 0-0.2m 0-0.2m 0-0.2m

Unlikely 2.2 2.2 2.2 2.2

Rare 3.25 3.25 3.25 3.25

Short-term Erosion Demand/Storm Bite

The analysis of the historical aerial photography previously undertaken by CES (2006) has been

reviewed to identify the magnitude of the short term, storm related erosion extents in the study

area. The estimates derived from this analysis have been varied within each coastal compartment

based on the observed extent of the short term dynamics in the vegetated dune extents identified

by the CES (2006) study to provide a range of short term erosion extent probabilities displayed in

Table 3-5.



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Table 3-5 Adopted Short-term Erosion Demand Extents for the Study Area


(m)

Apollo Bay

(m)

Wild Dog Creek

(m)

Skenes Creek

(m)

Almost Certain 3 1-3 3 3

Unlikely 5 2-5 5 5

Rare 8 3-8 8 8

The total coastal erosion extents (long term recession + short term erosion demand) for the three

probability scenarios for the study area are summarised in Table 3-3. The coastal erosion extents

displayed in Table 3-3 have been mapped to the coastal DEM to provide an estimate of the potential

extents of coastal erosion within the study area for each probability scenario and are displayed in

Figure 3-2.

Table 3-6 Coastal Erosion Scenarios for the Study Area


(m)

Apollo Bay

(m)

Wild Dog Creek

(m)

Skenes Creek

(m)

Almost Certain 3.9 3 3 3

Unlikely 7.2 7.2 7.2 7.2

Rare 11.25 11.25 11.25 11.25



2285-01 / R01 v04 - 26/10/2012 23

Figure 3-3 Coastal Erosion Hazard Extents



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4. RISK ANALYSIS

The coastal hazard risk analysis provides a method for understanding the following:

• The coastal hazard risk profile of assets in the study area

• How the asset risk profiles vary spatially within the study area

• Identifying priority risks to assets in the study area.

The risk analysis methods and likelihood and consequence definitions adopted for the assessment

are described in the following section.

4.1 Risk Analysis Method

The coastal hazard risk analysis involves considering both the likelihood and consequence of the

identified coastal hazard risks to assets in the study area. The definitions relating to the likelihood

and consequence of coastal hazard risks to the study area assist in transparently conveying the

uncertainty that exists in the analysis of the coastal hazard extents and in the relative consequences

that have been attributed to the different assets and land uses impacted by coastal hazards in the

study area. The likelihood and consequence definitions adopted for the risk assessment are

discussed in the following sections.

4.1.1 Likelihood Definitions

The likelihood or probability of coastal hazard impacts extending certain distances landward of the

existing shoreline has been defined for the study area for a number of discrete probability

definitions as described in Section 3.2. The likelihood definitions have been developed to provide a

degree of transparency in relation to the level of uncertainty, limitations and assumptions that are

considered to be contained within the analysis of the potential coastal hazard extents for the study

area over the 10 year management timeframe. The discrete probability definitions that have been

developed for the coastal hazard extents in the study area discussed below and summarised in Table

4-1.

The ‘Almost Certain’ probability definition represents a coastal hazard scenario and extent of impact

that could be considered imminent and/or could be expected to occur over the 10 year management

timeframe based on historical observations of shoreline recession rates and coastal inundation

extents.

The ‘Unlikely’ probability definition represents a coastal hazard scenario and extent of impact that

generally exceeds that which could be expected based on historical observations of the study area

but which can be predicted from theoretical analysis such that infrequent or isolated occurrences of

the hazard are possible.

The ‘Rare’ probability definition represents a coastal hazards scenario and resulting extent of impact

that significantly exceeds that which could be expected based on historical observations of the study

area but can be predicted from conservative theoretical analysis.



2285-01 / R01 v04 - 26/10/2012 25

Table 4-1 Risk Likelihood Definitions

Probability Definition Hazard Scenario Example

Almost Certain Coastal hazard impacts would be expected Based on observed historical shoreline

recession rates and storm erosion demand

and storm tide and wave run-up levels

Likely Not Assessed

Possible Not Assessed

Unlikely There is a low probability of coastal hazard

impact based on historical observations,

however, infrequent and isolated

occurrences of the hazard are possible

High shoreline erosion rates and wave

runup estimates based on theoretical

analysis and assumptions.

Rare There is a very low probability of coastal

hazard impact, hazard would only occur in

extreme circumstances

Extreme shoreline erosion rates and wave

runup based on maximum theoretical

values

4.1.2 Consequence Definitions

The relative consequence of coastal hazard impacts to assets in the study area is influenced to a

significant degree by the value that a particular stakeholder attributes to those assets. The

consequence definitions therefore include the following broad consequence values:

• Community Assets and Services

• Economic

• Environmental

• Public Safety

Table 4-1 displays the different consequence values and discrete consequence definitions for the

coastal hazard risk assessment.



2285-01 / R01 v04 - 26/10/2012 26

Table 4-2 Risk Consequence Definitions

Consequence Community Assets Infrastructure &

Services

Economic Health & Safety Environment

Catastrophic Long term loss of community assets

and regional infrastructure.

Severe, i.e. over $10 million

or more than 50% of assets

Multiple fatalities and/or severe

irreversible disability to multiple

persons

Irreversible damage to ecosystem or

landforms

Major Major asset damage, severe impact

and disruption to community

services and regional infrastructure

and assets

Major, i.e. between

$100,000 and $1M or 10 to

50% of assets

Single fatality and/or severe

irreversible disability to one or two

persons

Alteration or loss of sustainability of one

more ecosystems or several components

of these systems

Moderate Considerable impact upon access to

and function of community services

and assets

Moderate, i.e. between

$10,000 and $100,000 or

10%

of assets

Serious Injury. Moderate

irreversible disability or impairment

to one or more persons

Alteration or disturbances of a component

of an ecosystem but sustainability

unaffected

Minor Minor short term impacts (mainly

reversible) on low value community

services and assets

Minor, i.e. up to $10,000 or

1% of

assets

Significant Injury.

Reversible disability requiring

hospitalisation

Localised temporary effects on

environment beyond natural variability

Insignificant Little to no impact on communities

and their access to services

Impact below MHW mark Minor injury.

No medical treatment required.

Localised temporary effects on

environment within natural variability



2285-01 / R01 v04 - 26/10/2012 27

4.1.3 Risk Ranking

A risk matrix has been defined to describe the combination of likelihood and consequence that

produces a given level of risk to assets in the study area. The risk matrix adopted for the study is

displayed in Table 4-3. The level of tolerance to the risks to assets determined from the risk matrix

can be interpreted from the risk profile definitions displayed in Table 4-4.

Table 4-3 Risk Assessment Matrix

Consequence

Lik

eli

ho

od

Insignificant Minor Moderate Major Catastrophic

Almost Certain Low Medium High Extreme Extreme

Likely Low Medium High High Extreme

Possible Low Medium Medium High High

Unlikely Low Low Medium Medium Medium

Rare Low Low Low Low Medium

Table 4-4 Risk Profile Definition

Risk Profile Response

Low Tolerable Risk. A level of risk that is manageable without active intervention

Medium Moderate Risk. A level of risk requiring modest, precautionary intervention/treatment

to mitigate risks to acceptable levels

High Major Risk. A level of risk requiring significant, priority intervention/treatment to

mitigate risks to acceptable levels

Extreme Extreme Risk. A level of risk to assets that cannot be practically mitigated.

4.2 Risk Analysis Results

The coastal hazard extent probability zones developed in Section 3.2 were intersected with the

coastal asset database in a GIS to determine the risk profile for key assets in terms of the number,

length and/or area of potential coastal hazard impacts. For each of the assets determined to be

potentially impacted by coastal hazards, a consequence was assigned based on an evaluation of the

different values that can be attributed to the asset and the level of impact that could be expected to

the assets function or service in relation to these values due to its exposure to the coastal hazard.

The results of this analysis are described for each coastal compartment in the following sections.

4.2.1 Mounts Bay

The risk analysis has determined risk profiles for coastal assets in the Mount Bay coastal

compartment. The asset risk profiles are displayed spatially in Figure 4-1 and summarised in Table

4-5.

A number of assets have been determined as having risk profiles of medium or greater due to their

potential exposure to coastal hazards and consequences to the impacted assets function or service.

The following summarises the key risks to assets in Mounts Bay:



2285-01 / R01 v04 - 26/10/2012 28

• Approximately 145m of Barwon Water Sewer, and a similar length of water main, that is

located between the Great Ocean Road and the shoreline erosion scarp has been identified

as having a high risk profile. The high risk profile is due to a combination of the proximity to

the existing shoreline erosion scarp and the importance of the service this asset provides to

the community.

• Approximately 531m of the adopted Great Ocean Road foundation buffer is considered to

have a high risk profile. The high risk rank has been determined due to the potential for the

bearing capacity of the Great Ocean Road dune foundation being compromised by coastal

erosion and the subsequent consequence to the function of the Great Ocean Road.

• Additional medium risk ranks have also been identified for a toilet block, car park and a

number of beach access paths. The medium risk rank for the beach access paths relates

primarily to the potential public safety risks associated with the high erosion scarps

developing at the base of these paths.

Table 4-5 Mounts Bay Coastal Asset Risk Profiles

Low 739 12866 908 5

Revetment 5

Sewer 190

Walking track 353

Water Supply 191

Car parks 7958

GOR Foundation Buffer 985 123

Great Ocean Road 3923 785

Beach access 5

Medium 314 929 174 10

Revetment 77

Sewer 62

Walking track 142

Water Supply 33

Car parks 99 12.4


Great Ocean Road 21

Beach access 9

Toilet blocks 1

High 419

Sewer 146

Water Supply 274


Count ()Mounts Bay Asset Length (m) Area (m^2) Approx. Length (m)



2285-01 / R01 v04 - 26/10/2012 29

Figure 4-1 Mounts Bay Coastal Asset Risk Profiles



2285-01 / R01 v04 - 26/10/2012 30

4.2.2 Apollo Bay

The risk analysis has determined risk profiles for coastal assets in the Apollo Bay coastal


4-6.



The following summarises the key risks to assets in Apollo Bay:

• Approximately 100 metres of sewer rising main have been identified as having medium risk

profiles due to the potential impact of coastal erosion. Two short sections of sewer were

identified as having a high risk profile. These sections of sewer rising main have previously

been exposed following are large erosion event in 2005 and remain vulnerable to further

storm erosion events

• Some minor sections of the adopted Great Ocean Road foundation buffer have been

identified as of at risk from coastal erosion between Joyce Street and Marriners Lookout

Road. The probability of this buffer being impacted is however still considered to be ‘Rare’

and the risks are considered to remain essentially Low.

• Approximately 11 beach access paths were identified as having a medium risk profile due to

the public safety risks associated with erosion scarps developing at the base of the access

points following large storm events.



2285-01 / R01 v04 - 26/10/2012 31

Table 4-6 Apollo Bay Coastal Asset Risk Profiles

Low 912 1963 14 5

Groyne 18

Seawall 20

Sewer 80

Walking track 795

Car parks 1592



Other roads 105

Private Dwelling 159

Beach access 5

Medium 399 205 0 11

Groyne 35

Seawall 70

Sewer 80

Walking track 213

Car parks 14

GOR Foundation Buffer 3 0.4

Other roads 188

Beach access 11

High 39

Sewer 39

Apollo Bay Asset Length (m) Area (m^2) Approx. Length (m) Count ()



2285-01 / R01 v04 - 26/10/2012 32

Figure 4-2 Apollo Bay Coastal Asset Risk Profiles



2285-01 / R01 v04 - 26/10/2012 33

4.2.3 Wild Dog Creek

The risk analysis has determined risk profiles for coastal assets in the Wild Dog Creek coastal


4-7.



The following summarises the key risks to assets in the Wild Dog Creek coastal compartment:

• A number of short sections of sewer main were identified as having medium risk profiles.

The risks profiles for these assets are increased around the stormwater outfalls where the

shoreline has been eroded around these structures leaving relatively limited buffer distance

between the sewer main and the existing shoreline.

• Significant lengths of the Great Ocean Road have been identified as having a Low risk profile

due to the potential but rare likelihood of coastal inundation impacting the Great Ocean

Road in this coastal compartment. Some smaller sections of the Great Ocean Road have also

been identified as having a Medium risk profile due to the potential for more frequent

coastal inundation to impact these sections of the Great Ocean Road. No historical

observations of significant inundation of the Great Ocean Road within this coastal

compartment are however understood to exist, suggesting the inundation analysis maybe

somewhat conservative for this coastal compartment. Nevertheless, the elevation of the

Great Ocean Road within this coastal compartment is low and inundation due to

combinations of storm surge, wave setup and runup remain possible for this section of the

Great Ocean Road.

• A significant length of the adopted Great Ocean Road foundation buffer has been identified

as at low risk of erosion with a smaller section identified as at medium risk. These risks relate

to the section of the Great Ocean Road that runs behind the beach at Wild Dog Creek. The

morphology of the beach at Wild Dog Creek is highly variable due to the complex interaction

of creek streamflows and the coastal processes. These interactions result in rapid changes to

the creeks alignment along the beach in response to changing streamflow rates and

prevailing wave and sediment transport directions. There is the potential for these changes

in morphology to cause erosion of the foundations of the Great Ocean Road, compromising

the bearing capacity of the road base. However, the bluff separating the Great Ocean Road

from the beach is very well vegetated and the berm that is generated by wave action on the

seaward face of the beach at Wild Dog Creek tends to limit the ability for large waves to

directly impact this bluff such that the risks are considered to remain predominately Low.



2285-01 / R01 v04 - 26/10/2012 34

Table 4-7 Wild Dog Creek Coastal Asset Risk Profiles

Low 1388 10396 1502 4

Groyne 32

Sewer 482

Walking track 866

Water Supply 8

Car parks 1824



Other roads 737

Beach access 4

Medium 72 5068 933 1

Groyne 15

Sewer 35

Walking track 22

Car parks 345



Other roads 1190 238

Beach access 1

High 10

Sewer 10

Wild Dog Creek Asset Length (m) Area (m^2) Approx. Length (m) Count ()



2285-01 / R01 v04 - 26/10/2012 35

Figure 4-3 Wild Dog Creek Coastal Asset Risk Profiles



2285-01 / R01 v04 - 26/10/2012 36

4.2.4 Skenes Creek

The risk analysis has determined risk profiles for coastal assets in the Skenes Creek coastal


4-8.



The following summarises the key risks to assets in the Skenes Creek coastal compartment:

• A small section of the Great Ocean Road located approximately mid way between Wild Dog

Creek and Skenes Creek has been identified as having a High risk profile due to the potential

for coastal erosion to compromise the bearing capacity of the road foundations as well as

impact the road itself. The site inspection identified that rock armour has been placed

between the road and the shoreline along a small section of the coastline at this location to

mitigate the erosion risks to the road at this location. However, significant sections of the

Great Ocean Road foundation are not protected from coastal erosion at this location and the

risks are considered to remain significant that the roads function could be compromised due

to an erosion event.

• The Barwon Water pump station and toilet block located on the crown land adjacent to the

Caravan Park at Skenes Creek has been identified as having a medium risk profile due largely

to the potential for coastal inundation to impact this assets function. The pump station is

also located close to the mouth of Skenes Creek and some underlying risk of erosion

impacting the hazard remain possible but are considered low.

• A stormwater outfall is located under the shore platform at the eastern end of Skenes Creek.

Where the stormwater pipe crosses the shoreline the risk to this asset have been identified

as high due to the likelihood of coastal erosion impacting this asset. However, the depth at

which the pipe has been laid is not known and it is possible that the pipe would not be

exposed and therefore impacted by coastal erosion. Under this scenario, the risk profile for

this asset may in fact be Low.

• Risks to the Caravan Park associated with coastal inundation have been identified however

the probability of impact is considered to remain rare and hence the risk profile is Low



2285-01 / R01 v04 - 26/10/2012 37

Table 4-8 Skenes Creek Coastal Asset Risk Profiles

337 9751 266 3

Sewer 129

Stormwater 209

Car parks 1090

Caravan Park 6572



Other roads 307

Beach access 2

Toilet blocks 1

Medium 13 934 126 8

Sewer 6

Stormwater 7

Caravan Park 0.5



Beach access 7

Pump station 1

High 6 369 46

Stormwater 6


Skenes Creek Asset Length (m) Area (m^2) Approx. Length (m) Count ()



2285-01 / R01 v04 - 26/10/2012 38

Figure 4-4 Skenes Creek Coastal Asset Risk Profiles



2285-01 / R01 v04 - 26/10/2012 39

5. RISK TREATMENT

The consideration of strategies to treat coastal hazard risks identified in the study area has been

undertaken following the guidance provided for treating coastal hazard risks provided in the VCHG.

The risk treatment guidance provided in the VCHG recognises that the treatment of coastal hazard

risks is generally most effective when a comprehensive range of strategies are implemented. In

practise the most effective methods for managing risks to coastal assets is to identify options to

avoid risks to assets where ever possible. Risk avoidance recognises that the protection of coastal

assets by engineering works almost always inevitably results in unintended consequences to

adjacent shorelines and a more general loss of beach amenity if not carefully managed and planned.

Coastal protection works also generally create the expectation that the defence will be maintained

in perpetuity often leading to the intensification of development landward of the coastal protection

works and an overall increase in potential risks to assets overtime.

A range of precautionary, risk treatment strategies are therefore proposed to mitigate risks to

coastal assets identified in each of the four study area coastal compartments. Where possible,

opportunities to avoid risks via the planned relocation of vulnerable assets over time are proposed.

Where relocation of assets is not practical, or the current risks to assets have been identified as

requiring immediate treatment, risk reduction strategies have been proposed. To reduce risks, soft

engineering approaches such as beach renourishment/sand carting are proposed for the study area

in preference to hard engineering options. It is however recognised that at some locations in the

study area and in the long term, there may be little option other than to consider the use of hard

engineering structures to protect high value assets. As a contingency, recommendations are

contained within the plan to begin the long term planning and investigations required to evaluate

the use of hard engineering structures to protect high value assets in the study area that cannot be

practically relocated in the long term.

5.1 Mounts Bay

The assets at risk along Mounts Bay include high value assets such as the Great Ocean Road and

Barwon Water assets. The consequence of these assets being impacted by coastal hazards is

considered major due to the value of the services these assets provide to the community. The risk

analysis has therefore identified that a number of assets along the Mounts Bay shoreline have

medium to high risk profiles. Mitigation measures are therefore required to reduce the risks to these

assets to tolerable levels. Table 5-1 sets out the types of mitigation strategies proposed for the

Mounts Bay coastal compartment, the relevant stakeholders and the priority level for implementing

these measures over the 10 year management timeframe.

Table 5-1 Proposed Mitigation Strategies and Priorities for Mounts Bay Coastal

Compartment

Mitigation

Strategy

Mitigation Option Relevant

Stakeholders

Timeframe Priority

Risk

Reduction

Carry out remedial sand carting to

rebuild beach profiles in front of the

erosion scarp following major

erosion events and to accelerate

the natural beach and dune building

processes along the shoreline

following large storm events. To

OCC, DSE,

DOT

Immediate,

Ongoing

High



2285-01 / R01 v04 - 26/10/2012 40

limit the impact of a large number

of truck movements along the

foreshore and beaches and to

spread the costs over a longer

timeframe, it is recommended that

the sand carting initially aim to cart

approximately 3,000-5,000m3/yr

over a period of 4-5 years from the

Bunbury Point Groyne.

Risk

Avoidance

Planning should be undertaken to

determine the feasibility of

realigning the Great Ocean Road

such that it is located on the lee side

of the coastal barrier to provide a

greater buffer distance between the

road and the shoreline erosion

scarp. If realignment of the Great

Ocean Road is found not to be

feasible, planning and investigations

to provide engineered protection

works to secure the Great Ocean

Roads foundations along the

Mounts Bay shoreline should be

undertaken as a contingency

Vic Roads,

DSE

1-2 years

planning, 5-10

years

implementation

High

Risk

Avoidance

Remaining Barwon Water sewer

and/or potable water assets should

be gradually relocated and/or

contingency provided such that they

can be decommissioned over time

to limit the consequence of

exposure to further coastal erosion

along the Mounts Bay shoreline.

Barwon

Water

1-2 years

planning, 5-10

implementation

Medium

Risk

Avoidance

Rationalise the number of beach

access locations along the shoreline

and transition car parks to areas

further back from the existing

shoreline erosion scarp.

OCC 1-2 years Medium

Risk

Reduction

Undertake dune and beach

management works including

fencing and formalising beach

access points with timber walkways

to prevent beach access points from

becoming focal points for erosion

OCC Immediate,

Ongoing

Medium

Risk

Reduction

Place brush and plant colonising

grasses where possible along the

erosion scarp to trap and bind the

dune material

OCC Immediate,

Ongoing

Medium



2285-01 / R01 v04 - 26/10/2012 41

Estimated costs of sand carting from Bunbury Point Groyne to Mounts Bay are provided in Table 5-2.

Table 5-2 Sand Carting Cost Estimate from Bunbury Point Groyne to Mounts Bay

Item Estimate ($ ex GST)

Excavation and Transport Costs (3,000m3/yr @ $5.00m3 $15,000/yr

Estimated Costs over 10 Years (5 sand carting operations) $75,000

+20% Contingency (Emergency sand carting works ) $15,000

Total $90,000

5.2 Apollo Bay

The existing sand bypassing disposal method of discharging to the immediate lee of the Harbour has

resulted in large quantities of sand being trapped on the shoreline in the lee of the Harbour rather

than migrating north-eastward along the coastline. The erosion of the shoreline north of the

Harbour between Cawood Street and Marriners Lookout Road can be largely attributed to the

sediment transport deficit associated with the accretion of bypassed sand in the lee of the Harbour.

This has had the consequence of increasing the coastal hazard risks to assets along this section of

the Apollo Bay beach compartment to the extent that a number of assets are presently considered

to have medium to high risk profiles. The following sections discuss the range of risk avoidance and

risk reduction strategies available for the Apollo Bay coastal compartment. Table 5-5 summarises the

proposed risk treatment measures for Apollo Bay and their relevant priorities.

Harbour Bypassing

In the evaluation of appropriate coastal management options to mitigate the risks to assets along

the Apollo Bay coastal compartment, priority must first be given to treating the cause of the

increased coastal hazard risk exposure to the assets rather than attempting to treat the symptoms of

that increased exposure.

As has been identified from previous coastal process and studies of the study area by GHD (2009),

CES (2006) and Vantree (1996), discharging bypassed sediment north of the Harbour would allow

the sediment to be more readily mobilised and transported along the coastline to the north. The

improved longshore sediment transport supply along the Apollo Bay coastal compartment could be

expected to significantly assist in mitigating the coastal erosion and inundation that have been

experienced north of the Harbour since it was constructed some 60 years ago.

As previously recommended by GHD (2009), the disposal of the bypassed sediment through an

offshore disposal barge in a designated dredge material spoil ground to the north of the harbour

would provide a flexible, low impact and cost effective method for re-establishing the long term

sediment transport supply to the shoreline to the north of the Harbour. As the sediment migrates

shoreward, the improved sediment supply would assist in forming a wider and higher beach with

much greater resilience to storm events and prevent the immediate need for expensive and

problematic engineering works to protect assets located adjacent to the existing shoreline.

The imminent replacement of the existing dredge plant at the Apollo Bay Harbour provides the

opportunity to procure the required capital equipment including, booster pump, floating pipeline

and disposal barge to enable the offshore disposal of the bypassed sediment from the Harbour.

Indicative costs estimates for the capital equipment required to enable offshore sediment bypassing

were previously developed by GHD (2009) and are summarised below in Table 5-3.



2285-01 / R01 v04 - 26/10/2012 42

It is recommended that the response of the shoreline is monitored for a period of at least 18 - 24

months following the implementation of the improved bypassing method, to enable the benefits on

the beach condition to the north of the Harbour to be evaluated.

Table 5-3 Offshore Sediment Bypassing Cost Estimate


Capital Costs $350,000

Maintenance and Operational Cost (50,000m3/yr @ $1.5m3) $35,000

Estimated Costs over 10 Years $700,000

+20% Contingency $140,000

Total $840,000

Stormwater Outfall Rationalisation

The stormwater outfalls along the Apollo Bay beach compartment have historically caused locally

enhanced erosion and wave overtopping hazards due to the lowering of the beach in front of the

outfalls and resulting increased wave heights that can impact the back of the beach during storm

events. Works undertaken following the recommendations made by Vantree (1996) to extend the

stormwater outfalls onto the beach and overlay the outfall pipes with rock revetments have reduced

the impact of the outfalls on the coastal hazard risks. However, the stormwater outfalls and

associated rock revetments still cause some locally enhanced erosion such that increased risks to

assets identified in the Apollo Bay coastal compartment are located immediately adjacent to the

stormwater outfalls in a number of locations.

It is therefore recommended that a strategic assessment is undertaken to identify options to

rationalise and consolidate the number of stormwater outfalls along the Apollo Bay coastal

compartment in the long term.

Sand Carting

It is recommended that sand carting is undertaken as an interim mitigation measure until the

improved sediment bypassing arrangements start providing benefits to the shorelines to the north

of the Harbour and as a contingency to allow localised erosion to assets to be repaired as required

over the 10 year management timeframe.

Sand may either be sourced from the vicinity of the Bunbury Point Groyne and/or the sand that has

accreted within the south eastern corner of the Harbour as identified previously by GHD (2009).

Alternatively, opportunistic harvesting of sand from Wild Dog Creek beach, which is well supplied

with sand, could be undertaken to balance any shortfall from Bunbury Point or the Harbour.

Table 5-4 Sand Carting Cost Estimates from Bunbury Point to Apollo Bay


Excavation and Transport Costs (3,000m3/yr @ $5.00m3) $15,000/yr

Estimated Costs over 10 Years (5 sand carting operations) $75,000

+20% Contingency (Emergency sand carting works ) $15,000

Total $90,000



2285-01 / R01 v04 - 26/10/2012 43

Engineered Protection Works

If following implementation of the improved harbour bypassing, the coastal hazard risks to assets

continue to worsen to the extent that the risk profile to the Great Ocean Road in particular

demanded proactive mitigation, engineered protection works may have to be considered to reduce

the risks to acceptable levels.

The following two shoreline protection options have been identified for Apollo Bay:

• Shoreline Revetment

• Groyne(s)

Shoreline Revetment

A buried revetment structure(s) could be considered to provide a last line of defence to protect

vulnerable assets against large erosion events along the Apollo Bay shoreline. The revetment(s)

would be designed to be as low as possible to limit their impact on the foreshore amenity and under

normal conditions, the majority of the revetment(s) would be buried in sand at the back of the

beach. Only following large storm events would the revetment(s) be substantially exposed. Sand

carting would need to be undertaken in association with the construction of any revetments to

rebuild beaches in front of the revetment(s) following storm events. A relatively flexible construction

method for the revetment(s), with a lower visual amenity impact compared to traditional rock

armour, would involve the use of sand filled geotextile containers.

The main risks with engineered revetment(s) at Apollo Bay are considered the following:

• The revetment(s) would cause the beach to lower in front of the revetment during storm

events enabling large waves to break on or adjacent to the revetment, increasing the

inundation associated with wave overtopping on the Great Ocean Road.

• Terminal erosion impacts would increase risks to assets downdrift (to the north) of the end

of the revetment(s).

Groynes

As part of the consolidation of the number of stormwater outfalls, it would be possible to further

extend a small number of key outfalls and associated rock revetments onto the beach. These

structures could function as short groynes, facilitating the accretion of sand on their southern side

and helping to build a wider beach and more resilient shoreline. The construction of groyne

structures on the Apollo Bay beach would require detailed investigations and would need to be

undertaken in conjunction with sand carting to fill the groyne compartments to limit downdrift

impacts to shorelines.

Table 5-5 Proposed Mitigation Strategies and Priorities for Apollo Bay Coastal Compartment

Mitigation

Strategy


Stakeholders

Timeframe Priority

Risk

Avoidance

Explore the potential to procure the

required capital equipment

including, booster pump, floating

pipeline and disposal barge to

enable the offshore disposal of the

bypassed sediment from the

Harbour to replenish the beaches to

the north of the Harbour.

DOT, DSE Immediate,

Ongoing

High

Risk

Reduction

Carry out remedial sand carting to

rebuild beach profiles in front of the

OCC, DSE,

DOT

Immediate,

Ongoing

High



2285-01 / R01 v04 - 26/10/2012 44

erosion scarp following major

erosion events and to accelerate

the natural beach and dune building

processes along the shoreline

following large storm events. To

limit the impact of a large number

of truck movements along the

foreshore and beaches and to

spread the costs over a longer

timeframe, it is recommended that

the sand carting initially aim to cart

approximately 3,000-5,000m3/yr

over a period of 4-5 years from the

Bunbury Point Groyne or Wild Dog

Creek.

Risk

Avoidance

Undertake a strategic assessment to

identify options to rationalise and

consolidate the number of

stormwater outfalls along the

Apollo Bay coastal compartment in

the long term.

COC, DSE 1-2 years

planning, 5-10

years

implementation

Medium

Risk

Avoidance

Rationalise the number of beach

access locations along the shoreline

and transition vulnerable car parks

to areas away from existing erosion

hazards.

OCC 1-2 years Medium

Risk

Reduction

If improved harbour sand bypassing

cannot be implemented, planning

and investigations to provide

engineered protection works to

protect the Great Ocean Road and

should be undertaken.

Barwon

Water

1-2 years

planning, 5-10

implementation

Medium

5.3 Wild Dog Creek

Moderate risk profiles to the Great Ocean Road, associated with potential inundation, have been

identified for the Wild Dog Creek coastal compartment. However, the absence of anecdotal

confirmation of any significant historical inundation to the Great Ocean Road in this area suggests

the analysis maybe somewhat conservative. The remaining other significant potential risks to assets

relate to the proximity of the Great Ocean Road and associated foundation buffer to erosion

associated with the Wild Dog Creek beach. However, a range of mitigating factors are currently

present which are considered to result in low risk profile to the Great Ocean Road in this coastal

compartment.

Nevertheless, the Wild Dog Creek beach is a particularly dynamic environment, due to the

interaction of the Wild Dog Creek streamflows and the coastal processes, and rapid changes in

shoreline morphology are regularly observed and have the potential to impact assets such as the

Great Ocean Road. Regular monitoring and review of the state of the Wild Dog Creek beach should

be undertaken to ensure the risks to the Great Ocean Road and associated road foundations do not

increase to unacceptable levels.



2285-01 / R01 v04 - 26/10/2012 45

5.4 Skenes Creek

The major risk to assets in the Skenes Creek coastal compartment are associated primarily to the

extent to which coastal erosion has extended into the zone of potentially reduced bearing capacity

of the Great Ocean Road foundations at a location approximately mid way between Wild Dog Creek

and Skenes Creek. While some rock armour has been placed between the road and the shoreline at

this location it is not necessarily considered to have protected the full length of vulnerable road

identified in this assessment. It is recommended that specialist geotechnical advice is sought to

establish the extent of the risks to the foundations of the Great Ocean Road at this location and to

develop a more formal series of protective works they are found to be required at this location.

At Skenes Creek, the Barwon Water pump station and toilet block have been identified as at medium

risk associated with potential coastal inundation. These assets are also located close to the mouth of

Skenes Creek and some low, underlying risks associated with coastal erosion at this entrance are

also considered to exist. Regular monitoring and review of the state of the Skenes Creek entrance

and beach adjacent to these assets should be undertaken to ensure the risks do not increase to

unacceptable levels. Mitigation of existing levels of risk are considered to most appropriately

undertaken by precautionary dune and beach management works including fencing and formalising

beach access points along the coastal compartment. Table 5-5 summarises the proposed risk

treatment measures for the Skenes Creek and their relevant priorities.

Table 5-6 Proposed Mitigation Strategies and Priorities for Skenes Creek Coastal

Compartment

Mitigation

Strategy


Stakeholders

Timeframe Priority

Risk

Reduction

A geotechnical investigation of the

Great Ocean Road foundations

should be undertaken between

Wild Dog Creek and Skenes Creek to

establish the extent of the risks to

the Road’s foundations along this

section of coastline.

VicRoads Immediate High

Risk

Avoidance

Undertake dune and beach

management works including

fencing and formalising beach

access points with timber walkways

to prevent beach access points from

becoming focal points for erosion

OCC Immediate,

Ongoing

Medium

6. MONITORING AND REVIEW

Effective implementation of the CHP requires that information on the physical condition of the

shorelines is regularly gathered for the study area. As part of the implementation of the CHP, coastal

profiles are required to be surveyed at approximately 6 month intervals at critical locations within

each coastal compartment. The surveys should be undertaken from approximately mean water and

extend landward over the crest of the dune. The surveys should be reduced to Australian Height

Datum (AHD). Regular coastal profile monitoring of critical locations within the study area would

improve the implementation of the CHP by assisting in the following:



2285-01 / R01 v04 - 26/10/2012 46

• Improve the understanding of the physical processes and assist in refining the estimates of

coastal hazard extents in the study area in the future

• Prevent knee jerk reaction to isolated storm erosion events by providing a longer timeseries

of coastal change to compare against

• Assess the performance of the risk treatment measures

• Assist in establishing appropriate triggers for transitioning to more significant treatment

measures to mitigate coastal hazard risks in the study area.

The effectiveness of the CHP should be reviewed every two years by referring to the coastal profile

monitoring information to quantify the effectiveness of the risk treatment options and to

7. BIBLIOGRAPHY

B, G. R. (1985). Observations of surf beat. Journal of Geophyscial Research , 2997-3012.

Coastal Engineering Solutions. (2005). Apollo Bay Sand Study. Melbourne: Coastal Engineering

Solutions.

GHD. (2009). Apollo Bay Sand and Dredging Options Study. Melbourne: GHD.

GHD. (2011). Report for Crownh Land Reserves: Risk Assesment and Risk Treatment Plan. Melbourne:

GHD.

Hallermeier, R. J. (1978). Uses for a Calculated Limit Depth to Beach Erosion. Proceedings of the 16th

International Conference of Coastal Engineering , 1493-1512.

Holman, R. (1986). Extreme value statistics for wave run-up on a natural beach. Coastal Engineering ,

527-544.

McInnes, K. .. (2009). The Effect of Climate Change on Extreme Sea Levels along Victoria's Coast.

Melbourne: CSIRO.

Nielsen, P. a. (1991). Wave runup distributions on natural beaches. Journal of Coastal Research ,

1139-1152.

Otway Coast Committee. (2012). Draft Coastal Management Plan. Apollo Bay: Otway Coast

Committee.

Vantree. (1996). Apollo Bay Coastal Processes. Melbourne: Vantree.

Vantree. (1997). Mounts Bay Beach: Report on Coastal Erosion. Melbourne: Vantree.

Victorian Coastal Council (2008), Victorian Coastal Strategy 2008, Melbourne: Victorian Coastal

Council

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