iarnród Éireann

Iarnród Éireann

East Coast Erosion Study

Options and Feasibility Assessment

REP.264204-00.006

Final | 31 July 2020

This report takes into account the particular

instructions and requirements of our client.

It is not intended for and should not be relied

upon by any third party and no responsibility

is undertaken to any third party.

Job number 264204-00

Ove Arup & Partners Ireland Ltd

Arup

50 Ringsend Road

Dublin 4

D04 T6X0

Ireland

www.arup.com

http://www.arup.com/

Iarnród Éireann East Coast Erosion Study Options and Feasibility Assessment

REP.264204-00.006 | Final | 31 July 2020 | Arup

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Contents Page

1 Introduction 1

2 Glossary of terms 3

3 References 4

4 Methodology 5

4.1 Background 5

4.2 General approach 5

4.3 Appraisal period 6

4.4 Preliminary assessment approach 6

4.5 Multi-Criteria Analysis approach 6

5 Coastal protection solutions 9

5.1 Introduction 9

5.2 ‘Do nothing’ 10

5.3 ‘Do minimum’ 10

5.4 Hold the line 12

5.5 Advance the line 17

5.6 Retreat the line 19

5.7 Other 20

6 Sustainable solutions 21

6.1 Introduction 21

6.2 Choosing sustainable coastal solutions 21

6.3 Complimentary measures 21

6.4 Enrichment of hard structures 22

6.5 Planting of vegetation 23

6.6 Other additional uses 24

6.7 Nourishment sources 24

7 Options and feasibility assessment for long term 26

7.1 Introduction 26

7.2 CCA1 – Merrion to Dun Laoghaire 26

7.3 CCA2-3 – Dalkey Tunnel to Killiney Station and Killiney South 32

7.4 CCA4 – Bray North 37

7.5 CCA5 – Bray Head to Greystones North Beach 41

7.6 CCA6 – Greystones to Wicklow Harbour 46

7.7 CCA7 – Wicklow Harbour 56

7.8 CCA8 – Arklow North Beach 56



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7.9 CCA9 – Arklow Harbour 61

7.10 CCA10 – Arklow South Beach 61

7.11 CCA11 – Brittas Bay 66

8 Short term measures 69

8.1 Additional studies 69

8.2 Repairs 69

9 Conclusions 70

Appendices

Appendix A

MCA criteria

Appendix B

MCA analysis



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Page 1

1 Introduction

This report has been developed as part of the Iarnród Éireann East Coast Erosion

Study, and forms part of Interim Report 2. It covers the WP8. Options and

Feasibility Assessment, as defined in the Scope of Services (Figure 1). Details

regarding the complete scope of the study as well as a definition of the Study Area

are given in Section 1 of the Project Inception and Survey Report, which highlights

the processes and outcomes relating to WP1, WP2 and WP3.

Figure 1: Flowchart showing the structure of this study, defined in Volume C Scope of

Services.

The purpose of the Feasibility Assessment is to investigate appropriate options and

measures to best manage the main coastal risks identified for each of the Coastal

Cell Areas (CCAs), associated with coastal erosion and accretion. This report

presents the procedure that has been followed for the development of the options

and feasibility assessment as well as the preferred option(s) and measures for each

CCA.

First, the assessment methodology is outlined in Section 4. The general coastal

protection measures that have been considered are described in Section 5. Section

6 outlines sustainable solutions that can be adopted in tandem with the preferred

options. The options and feasibility assessment for long term and proposed

measures for short-term are presented in Sections 7 and 8 respectively. Finally, a

summary of the resulting preferred solutions and overall conclusions from the

assessment are given in Section 9.





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This Options and Feasibility Assessment assesses all options and measures at

feasibility stage level. It identifies the preferred type of solution based on the

information assessed within the scope of the Feasibility study.

Further detailed studies will be required in subsequent stages to confirm and refine

the selected option(s) and measure(s).

These detailed additional studies at scheme and detailed design stage may include,

amongst others, wave modelling studies, sediment hydrodynamic geotechnical

studies assessing the preferred option(s), geotechnical investigations, etc.





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2 Glossary of terms

• CCA: Coastal Cell Area

• CFRAM: Catchment Flood Risk Assessment and Management

• DEFRA: Department of Environment, Food and Rural Affairs

• GEP: Good Ecological Potential

• GES: Good Ecological Status

• IGH: Irish Geological Heritage

• MCA: Multi-Criteria Analysis

• OPW: Office of Public Works

• SDG: Sustainable Development Goal

• UN: United Nations

• WFD: Water Framework Directive

• WP: Work Package





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3 References

• DEFRA and Environmental Agency’s (UK) Cost estimation for coastal

protection – Report SC080039/R7 (2015)

• Flood and Coastal Erosion Risk Management appraisal guidance (FCERM-AG)

(2010)

• DEFRA and Environmental Agency’s (UK) Modelling the effect of nearshore

detached breakwaters on sandy macro-tidal coasts – Report SC060026/R2

(2010)

• Interim Level 3 Feasibility Report: Coastal Defence Works: Greystones to

Wicklow (COWI, 2000)

• Earthworks for Railways – Coastal Protection (COWI & Fehily Timoney

Gifford Consulting Engineers, 2002)

• An overview of railway coastal protection on the east coast with particular

reference to solutions applied between Bray and Wicklow (COWI & Iarnród

Éireann, 2003)

• Exeter to Newton Abbot Geo-Environmental Resilience Study. Phase 2:

Options Assessment Report (CH2M, 2016)

• Conservation Management Options & Recommended Prescriptions for Brittas

Dunes and associated habitats, Brittas Bay, County Wicklow

(ALANLAUDERCONSULTING, 2018)

• The Murrough Coastal Protection Study (RPS, 2007)

• Murrough Revetment Erosion and Stability Assessment (including associated

drawings) (RPS, 2015-2016)





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4 Methodology

4.1 Background

This assessment is intended to investigate measures to best manage the risks

associated with coastal erosion and accretion. However, as outlined in the Risk

Assessment report and with the aim of following a holistic approach, other risks

such as coastal flooding, damage/collapse of the existing coastal defences and

geotechnical-related risks have also been considered.

The options and feasibility assessment draws upon the information presented in the

previous work packages. In particular, it takes into consideration:

1. Areas at risk identified in WP3. Surveys of Existing Coastal Protection

Measures.

2. The future areas of coastal erosion and accretion (coastal change) throughout

the Study Area based on the existing and future timeframe scenarios (years

2050 and 2100) obtained in WP5. Detailed Current and Future Scenario

Coastal Change Maps based on the results extracted from WP4. Assessment

of Existing Coastal Process and Coastline Evolution.

3. Risks identified in WP6. Detailed Risk Assessment.

4. Key environmental aspects extracted from WP7. Preliminary Environmental

Assessment and Consultation.

4.2 General approach

The approach that has been followed for the development of this study is similar to

that developed by the OPW for the National Catchment Flood Risk Assessment and

Management (CFRAM) programme.

It follows a holistic approach which takes into consideration the effectiveness of

the solutions in the context of the entire extent of the Study Area and any effects on

adjoining areas.

The assessment has been carried out following a two-step approach. For each of the

CCAs, the following assessments were carried out:

1. Preliminary assessment – the applicability of a large number of measures to

mitigate the identified risks is studied from a high-level point of view. The

outcome from this assessment is the definition of ‘preliminary options’.

2. Options assessment – Multi-Criteria Analysis (MCA), where the ‘preliminary

options’ are scored in terms of social, environment, cultural heritage,

economics and infrastructure aspects, based on which the preferred option is

identified.

This methodology is graphically summarised in Figure 2. The approach that has

been followed during the preliminary assessment and the options assessment is

summarised in the following sections.





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Figure 2: Flowchart showing the methodology for the Options and Feasibility

Assessment.

4.3 Appraisal period

The appraisal period for coastal schemes and strategies is usually taken as 100 years

to allow appropriate comparison of options. Furthermore, for the present options

study, a long-term approach has been taken for the project considering a timeframe

until the year 2100. Using a medium-term approach (such as year 2050) would

mean that costs or benefits that occur after 50 years are not taken into account and

this could affect which option is identified as preferred. For example, short time

horizons can bias the economic appraisal against options that are costly to construct

but which are less expensive to maintain. Consequently, the timeframe scenario of

year 2100 where erosion maps have been modelled and risks evaluated will be used

as a base for the assessment.

Therefore, proposed options and measures have been identified separately for both,

short and long term.

The assessment of short-term options has been carried out based on the WP3.

Surveys of Existing Coastal Protection Measures, and recommendations have been

provided for the critical assets.

4.4 Preliminary assessment approach

The preliminary assessment considers a large number of measures, both structural

and non-structural, to mitigate the identified risks. These measures are assessed in

terms of whether they are applicable and practical within a CCA given the

characteristics and specific risks of the area. The outcome from this assessment is

the definition of the options to be evaluated with the MCA. These options are

referred to as ‘preliminary options’ throughout this report.

The preliminary assessments as well as the resulting ‘preliminary options’ for each

of the CCAs are presented in Section 7.

4.5 Multi-Criteria Analysis approach

4.5.1 General

The ‘preliminary options’ are subsequently evaluated on a Multi-Criteria Analysis

(MCA) basis. The outcomes from the MCA carried out are presented in Section 7

for each of the CCAs.

Identified risks

Preliminary assessment

Preliminary options

Options assessment

(MCA)

Preferred option





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The assessment criteria that has been included for the MCA is as defined in the

Scope of Services and is aligned with the categories considered for the identification

of impacts in the risk assessment. The MCA used follows the key principles and

recommendations of the DEFRA and the Environmental Agency’s (UK) Flood and

Coastal Erosion Risk Management Research and Development Programme.

Furthermore, the OPW was consulted during the development of the MCA matrix.

Within the framework of the DEFRA guidance the principles of the UN Sustainable

Development Goals (SDGs) have been applied.

4.5.2 Assessment criteria

The core criteria under which each preliminary option is assessed are listed as

follows:

• Human health and life (social);

• Environment;

• Cultural heritage;

• Economic activity;

• Infrastructure.

A summary of the specific items considered under each core criterion, as well as

their corresponding weighting is provided in Table 1. The table also shows the

corresponding UN SDG numbers.





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Table 1: Summary of scoring criteria for MCA.

Core criteria Global

weighting

Objective Individual

weighting

Economic 25% Assets 30%

Land use 20%

Infrastructure 50%

Social 15% Health and safety

(construction)

30%

Health and safety (design life) 30%

Community 10%

Access 15%

Social and recreation facilities 15%

Environmental & Heritage 20% Environmental Aspects

(Ecology, Habitats and Birds

Directives and flora and

fauna)

50%

Landscape and visual 20%

Cultural heritage 10%

Licencing and Statutory

Permits

20%

Technical 20% Hazard elimination 30%

Constructability 30%

Impact on adjacent areas 20%

Sustainability and

adaptability to climate change

20%

Cost 20% Capital expenditure 75%

Maintenance expenditure 25%

A detailed description of each criteria objective as well as the corresponding scoring

regime (raking from 1 to 5) is given in Appendix A.





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5 Coastal protection solutions

5.1 Introduction

A variety of measures can be used to protect coastal areas at risk of coastal erosion

and/or flooding, as well as to enhance or preserve a social and environmental assets

or amenities.

Since coastal protection works have the potential to impact directly on adjacent

areas, any proposal for protection works must take account of the wider

implications. Proposal should take account of the potential effects on existing and

predicted longshore sediment transport regimes and the wave climate across the

entire site and adjacent coastal cells, as well as the marine environment.

A general classification of options for reducing coastal erosion risks is presented in

Figure 3 below.

Figure 3: General classification of coastal erosion protection measures.

Coastal protection measures can be structural or non-structural. The list of potential

measures is long and includes, among others: sea walls, groynes, offshore

breakwaters, artificial headlands, beach nourishment and dune rehabilitation. When

the main causes of coastal erosion (and flooding) are extreme storm events, the most

suited coastal protection measures are those which either help to strengthen the

coastline or those which reduce the incident wave forces.

The general classification described above can be further defined using the

following categories: ‘do nothing’, ‘do minimum’, ‘hold the line’, ‘advance the

line’ and ‘retreat the line’.

Figure 4 shows a graphical summary of the main options that that could be

implemented to mitigate the coastal risks identified in the risk assessment, grouped

into these headings.





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Figure 4: Summary of solutions considered for the options and feasibility assessment.

The nature of the solutions outlined above ranges from ‘soft’ to ‘hard’. ‘Soft’

solutions are generally more sustainable in terms of resilience, protection and

enhancement of marine, coastal and terrestrial ecosystems as well as reduced

carbon footprint. Therefore, implementation of ‘soft’ solutions is generally

preferred. However, these options generally involve a higher degree of uncertainty

than solutions of a ‘hard’ nature, which have been implemented throughout the

globe and thoroughly studied. With the purpose of studying the relative advantages

and limitations for each CCA, both ‘soft’ and ‘hard’ solutions have been considered

in this assessment.

A brief description of each of the solutions outlined above is provided in the

following subsections.

5.2 ‘Do nothing’

As the name suggests, this option involves allowing the coastline to evolve naturally

without any coastal protection measures. In relation to the existing coastal defences,

this solution does not account for any capital or maintenance works to be

undertaken in the future. No maintenance work, no capital work and no emergency

responses to failures or near failures

The ‘do nothing’ option will always be included as baseline in the MCA analysis

to ensure the justification of the preferred option.

5.3 ‘Do minimum’

This option is defined by the minimum measures that are required to provide

protection to the key assets present in each CCA.

Do nothing No active intervention

Hold the line

Advance the line

Retreat the line

Other

Beach management (e.g., nourishment, groynes, dune regeneration)

New attached defences (e.g., seawalls, revetments)

Large scale nourishment (e.g. artificial island, sand engine)

New detached defences (e.g., detached breakwaters)

Land reclamation

Managed realignment

Relocation or raising of railway infrastructure

Do minimum Maintenance or strengthening of existing defences





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“Do minimum” is usually taken as the minimum amount of action (maintenance

and minor repair) to retain some defences or protection works. If major capital

works would be required in the future (for example, to replace defences) then this

would not be classed as do-minimum. This may mean that do-minimum would

revert to do-nothing when it is no longer feasible to continue maintaining the

defences.

In areas where coastal defences are already present, this option generally involves

appropriate maintenance or upgrade works. For unprotected areas at risk, further

measures could be considered. It should be noted that the do-minimum option will

not deliver adaptation options or wider objectives. This could result in reduced

standard of service over time (for example, due to climate change).

5.3.1 Maintenance of existing defences

This option involves an intervention to existing coastal defences with the purpose

of extending their residual life without modifying the current configuration. No

upgrade works (such as an increase of the structures’ dimensions) are undertaken

as part of this approach.

Asset maintenance is considered to be a ‘business as usual’ option. It can be

undertaken in two forms, involving either a reactive manner or a proactive manner:

• Reactive maintenance: Maintenance works are undertaken following damage or

collapse of the existing coastal defences, usually triggered by a storm event.

• Proactive maintenance: Frequent assets inspections are carried out and

maintenance works are undertaken as issues are identified (at an early stage),

with the purpose of preventing or minimising further deterioration, damage or

collapse. This approach would typically require the provision of a maintenance

budget for the continued upkeep of the existing defences.

Reactive maintenance has not been considered as a suitable option for any of the

CCAs for medium and long-term management due to the lack of resilience it

provides as well as health and safety concerns.

With proactive maintenance, the current structures’ standard of protection will not

be appropriate to withstand risks associated with future scenarios such as sea level

rise and increased storminess due to climate change. Thus, this option is not

considered appropriate in areas where the identified erosion risk could cause

unacceptable damages.

5.3.2 Strengthen existing defences

This solution refers to undertaking upgrade works to existing coastal defences in

order to extending their design life as well as to improve their current standard of

protection (for instance, to be in line with the expected impacts of climate change).

These works generally consist of raising the defence level of existing defence

structures and adapting the structure dimensions. This option generally relies on the

existing defences’ structure and foundation being sufficient to allow for additional

weight, however it can also involve works to improve structural capacity.





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Strengthening of existing defences has been proposed within the ‘preliminary

options’ for several CCAs.

5.4 Hold the line

5.4.1 New attached defences

The solutions included within this group involve the construction of new coastal

defences located on land and parallel to the coastline. New defences would be

designed with appropriate layout, dimensions and material characteristics in

accordance with current standards and expected future climate conditions.

The following main defence types are included within this group:

Vertical or near-vertical sea walls:

These are typically continuous structures, such as gravity walls or diaphragm walls,

intended to function as a shelter from wave action to the assets located behind them.

The walls can be formed of different materials, with concrete, blockwork and steel

(sheet piles) being the most common. The walls can be of different shapes and can

include a recurve element near the crest to minimize wave overtopping during storm

events.

Figure 5: Seawall at Dawlish, UK (Source: Arup)

These structures typically provide low wave energy dissipation in comparison with

other options due to their (near-)vertical configuration.

Vertical structures can cause a decrease of adjacent beach levels due to wave

reflection and refraction. To overcome this effect, beach nourishment programmes

are usually proposed as a complementary measure for this type of solution.

Due to the low level of resilience, high cost and generally negative environmental

implications, this option has only been considered for CCA1, where gravity walls

already exist.





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Revetment structures:

Revetments are linear coastal structures intended to reduce the impact of wave

action to the area located behind it. Such structures are typically formed with rock

armour or pre-cast concrete units, however the use of alternative materials with

lower environmental impacts has been increasingly investigated recently.

Figure 6: Rock revetment at Ballygannon, Co. Wicklow (Source: Arup)

Similar to sea walls, a beach nourishment programme is often recommended as an

accompanying measure to minimize the decrease of beach levels expected from the

presence of a hard structure.

Earth embankments:

Earth embankments are sloping structures made of compacted soil. They can be

strengthened by the use of reinforcement systems such as geosynthetics and steel

strips.

Figure 7: Coastal dike at Delfzijl, NL (Source: Eurotop Manual 2018)





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While earth embankments are sometimes adopted along rivers and estuarine areas,

they are generally not considered appropriate in unsheltered areas open to the sea

as a standalone measure, as they can be subject to significant damage by wave

action.

Due to the exposed nature of all the CCAs this option has not been considered as a

viable solution in any of the CCAs.

5.4.2 New detached defences

The most common defence structure that constitute this group are detached

breakwaters. These are structures generally placed parallel to the shore at an

appropriate distance offshore, with the principal purpose of reducing wave energy

in the nearshore area. Submerged offshore breakwaters can be adapted to form an

artificial reef.

Figure 8: Breakwater construction; Sea Palling, Norfolk, UK (Source: Modelling the

effect of nearshore detached breakwaters on sandy macro-tidal coasts, DEFRA)

These structures are normally formed with rock armour or pre-cast concrete units

with alternative materials utilised for artificial reefs. Significant research has been

carried out in relation to the use of more sustainable materials, such as geo-tubes

filled with dredged material, for the construction of breakwaters.





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5.4.3 Beach management

The main beach management techniques that have been considered for this

assessment are the following:

Beach nourishment:

Beach nourishment consists of the placement of large amounts of sediment

material, such as sands and gravels, with the purpose of raising the beach levels of

particular areas. Beach nourishment is typically carried out as a continuous

programme over time with frequent monitoring of beach levels.

Additional beach nourishment material may be required following significant storm

events causing erosion/ loss of beach material.

Figure 9: Beach nourishment Greystones, Co. Wicklow (Source: Arup)

Beach nourishment is proven to be a very successful coastal protection solution for

enclosed coastlines where bays are bounded by prominent headlands or groynes. In

these conditions, a nourishment program could maintain a healthy mid-term beach

and stable coastline. It is also good practice to implement a beach nourishment

programme as a complementary measure when installing a ‘hard’ structure (e.g.

vertical wall), to minimize scour issues at the structure toe.

This solution allows for adaptive management, as there is flexibility to modify the

nourishment scheme over time.

To further increase sustainability a beach nourishment scheme should ideally be

combined with a suitable dredging scheme.





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For example, the dredged material from Rosslare Harbour has been used for beach

nourishment of the coastline at Rosslare Strand. This is discussed further in Section

6.7.

Groynes:

Groynes are long, narrow structures placed perpendicular to the shoreline. They act

as beach control structures by the introduction of physical impediments to sediment

movement. This causes a build-up of beach material along the shore between

successive groynes. The increased beach levels reduce wave impact on assets or

coastal defence structures located along the shoreline. Retention of beach material

can also be of benefit in areas of high public amenity value such as beaches.

Figure 10: Groyne system at Delfland, the Nederlands (Source: Terra et Aqua, No. 107,

June 2007)

This solution would require the adoption of a beach nourishment programme to

facilitate the accumulation of material near the structures. Beach recycling

(relocation/spreading out of beach material) could be carried out as required to

ensure that the beach material remains within the immediate area and is not

transported offshore, and that beach levels are maintained as appropriate.

An example of a groyne system can be found immediately south of Bray Harbour

(i.e., south of CCA4), where containment and build-up of sediment material in the

form of shingle has been proved successful.

Dune regeneration:

Dune regeneration consists of the implementation of measures that encourage the

creation or enlargement of sediment deposits on dunes. It is comprised of different

techniques, such as dune planting, fencing and placement of warning and

educational signs.

Dune regeneration should be incorporated as part of a beach monitoring regime to

ensure that the system can be readily adapted to the evolution of the coastal cell.





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Figure 11: Dune regeneration on the Danish North Sea Coast (Source: DHI Shoreline

Management Guidelines)

5.5 Advance the line

5.5.1 Accretion

It is important to note that for all the CCAs assessed in this study, predicted potential

accretion has been considered positive in all cases given the lack of risks associated

with this natural process. Accretion involves advancing the line which provides

additional protection to the existing coastline.

5.5.2 Large-scale nourishment

Large-scale nourishment consists of the import of large volumes of sediment (sand

or shingle) and placement either along or near the shore. It can be considered as

‘working with nature’ as, once the material is in place, it can be transported through

natural sediment transport processes.





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Figure 12: Sand motor project in the Netherlands (Source: www.dezandmotor.nl)

Large-scale nourishment can be designed in different forms, such as artificial

islands and ‘sand engines’. The ‘sand engine’ or ‘sand motor’ terminology comes

from the large nourishment programme recently carried out in The Netherlands.

This programme involved the placement of approximately 20 million m3 of sand,

forming a peninsula that extends 2km long and 1km into the sea. It is designed to

provide sufficient protection for 20 years.

This solution needs a large amount of nourish material. It is common practice and

widely accepted in the Netherlands to dredge for this material, however, in Ireland

this is not the case and schemes like this will need to be approached with caution

and sensitivity to public perception.

This solution also requires an established monitoring system due to the high level

of uncertainty associated with the evolution of this solution.

5.5.3 Land reclamation

This solution consists of moving the existing coastline seawards, building new

defences further out with the purpose of replacing existing defences and reducing

the impact from wave overtopping on the assets located behind it.

The additional space created could be used for different purposes, such as the

creation of greenways and cycleways to large reclamations providing development

lands such as the mooted housing scheme beside the Irish Glass Bottle site in

Dublin.

This option requires a large capital investment, due to the significant amount of

material required for the reclamation works as well as the construction of new

defences along the reclaimed area.





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5.6 Retreat the line

5.6.1 Managed realignment

Managed realignment describes the repositioning and/or removal of an existing

coastal defence, allowing natural erosion and retreat of the coastline. In low lying

areas it provides controlled or ‘managed’ flooding in areas adjacent to existing

defences (the hinterland). The extent and depth of flooding is controlled and

retained on the landward side through high ground or a secondary set of defences.

Figure 13: Managed realignment at Medmerry, UK (Source: Environment Agency)

Through managed realignment, the area between the existing and new defences is

effectively sacrificed to the sea and is allowed to erode or flood naturally. The

sacrificed lands act as a barrier to wave action and can help reduce wave energy.

This option has significant environmental benefits as the new intertidal area can be

adapted to enhance local biodiversity and create additional intertidal habitats.

Managed realignment is usually appropriate in areas where the value of the assets

along the coastline does not justify intervention measures and where the areas to be

protected are located at a significant distance from the shoreline. It can also be

found appropriate where shoreline protection efforts and/or repeated maintenance

are considered to be too costly and ultimately ineffective at preventing further

erosion and/or flooding.

Managed realignment is sometimes viewed as a last-ditch option and an admission

that coastal erosion and/ or flooding is unavoidable. The solution effectively

sacrifices lands to the sea through erosion or flooding. If properties are located in

the sacrificed lands there will be costs associated with the relocation of affected

property owners.

This solution has not been considered for any of the CCAs as abandonment of the

railway line is not a viable option. Note that relocation of the railway line is

described as a separate solution.





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5.7 Other

5.7.1 Relocation of railway infrastructure

Relocation of the existing railway line has been considered in areas where existing

transport infrastructure is located adjacent to the coastline, i.e., CCA1 to CCA6.

The solution involves rerouting of transport routes (e.g. road and railway) to areas

inland where they will not be at risk of erosion or coastal flooding.

While the costs involved are significantly larger than for the other protection

solutions considered, this option has been selected as a ‘preliminary option’ for

areas where it would result in significant environmental, economic and social

benefits.

5.7.2 Raising of railway infrastructure

In some areas, localized raising of the railway line may result in a significant

reduction of the risks affecting the infrastructure, especially those related to

flooding.

Depending on the location of the line in relation to the coast, the raised line (and

complementary structures) may form a barrier against wave action and hence

provide additional protection benefits to land and properties located on the

landward side of the track. Such an option is potentially constrained by grade

requirements, clearances at existing tunnels and footbridges, as well as many other

rail asset considerations.

Due to the high level of disruption as well as technical complexity, and the

consequential very high costs, this option has not been adopted as a preliminary

option for the MCA for any of the areas.





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6 Sustainable solutions

6.1 Introduction

Sustainability and the UN Development goals have been a key consideration during

the coastal protection options assessment.

Iarnród Éireann in collaboration with Wicklow County Council have recognised

that without a long-term sustainable vision the east coast of Ireland will soon be

completely covered in hard defences (rock armour, concrete walls). This will mean

a loss of habitat and amenity that is not in line with the sustainable principles that

Iarnród Éireann, Wicklow County Council and Arup are committed to.

This study has therefore made a particular effort to put forward sustainable

solutions that provide protection against the coastal risks identified in WP4.

Assessment of Existing Coastal Process and Coastline Evolution.

6.2 Choosing sustainable coastal solutions

Most of the coastal protection solutions considered in this study involve a

sustainability component; generally in terms of resilience, protection and

enhancement of marine, coastal and terrestrial ecosystems and reduction of carbon

footprint. Nature-based solutions have been favoured with natural processes and

materials already present in the area involved in the protection scheme, for example,

the potential reuse of dredge material in beach nourishment schemes. These

measures preserve, enhance or restore elements of a natural system rather than

acting to their detriment.

In terms of addressing coastal protection, nature-based solutions can be generally

defined as ‘soft’ solutions. Although ‘soft’ solutions are preferred due to their

sustainability component, they often take much longer to yield benefits when

compared to traditional ‘hard’ solutions, which yield benefits soon after

construction. In addition, they also involve a higher degree of uncertainty due to

limited experience with these solutions and location specific coastal dynamics.

This, added to the large costs associated with implementation and maintenance of

the natural-based solutions, results in some of the preferred solutions arising from

the MCA taking the form of ‘hard’ solutions.

However, there are ample opportunities for improving the sustainability of the

coastal protection measures on the east coast; generally in terms of ecosystem

protection and enhancement and reduction of carbon footprint.

6.3 Complimentary measures

A large amount of research is being carried out in relation to hybrid solutions that

incorporate a sustainable component to conventional measures. Some examples

include the promotion of ecological growth near or on maritime structures, planting

of vegetation and smart sourcing of materials.





Page 22

The definition of these ‘complementary’ measures is not within the scope of this

Feasibility Stage as their primary function does not address coastal protection

objectives, but they should be implemented in the subsequent design stages (e.g.,

preliminary design, detailed design). A number of examples are discussed in the

following sub-sections.

6.4 Enrichment of hard structures

The enrichment of hard structures intends to promote the growth of ecological

habitats in the intertidal and subtidal zone of artificial structures. Several solutions

with this aim have been studied and adopted in recent years in different parts of the

world, the most successful examples being:

• Creation of tidal pools within the structures;

• Addition of hanging textile materials (e.g., ‘hulas’) to the structures;

• Use of alternative materials (such as concrete-derived mixtures, e.g. eco-

concrete) to form, fully or partially, the structures;

• Use of 3D-printed elements (e.g. tiles attached to structures, 3D-printed

structures or blocks) to form, fully or partially, the structures, or as an addition

to the structures.

Figure 14: Artificial reef structures Aspinall, Richard: From concrete to coral: breeze

blocks make a splash regenerating reefs (Source: The Guardian 20.09.2016)

All of these solutions require detailed assessment of the characteristics of the

receiving environment, the intrinsic properties of the designed structures and the

interaction between both, as these will ultimately define their suitability in each

specific case. Many of the solutions published were developed in tropical and

sheltered waters and may therefore not be suitable for implementation in Ireland.

The east coast of Ireland is a very high energy environment requiring solutions that

can withstand such a location.

A noteworthy initiative is the EcoStructure project of which Arup is a member of

the Working Group (http://www.ecostructureproject.eu/). EcoStructure is a

http://www.ecostructureproject.eu/





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European initiative that aims to characterise variation in impacts of different

artificial structures in different environmental contexts and develop a tool to support

decision-making on artificial structure design. The project focuses on coasts along

the Irish Sea (including specific examples along several CCAs), and therefore the

findings are extremely relevant to the Study Area. While this tool is not developed

yet, as research is still on-going, the interim results and ultimately the tool itself can

inform future stages of design.

Figure 15: Hard coastal protection providing marine habitat (Source: https://www.moore-

concrete.com/civil/econcrete/#!)

6.5 Planting of vegetation

The addition of vegetation to the existing coastal environments can enhance the

existing system ecology but at the same time it can also considerably strengthen the

natural systems in terms of protection against erosion. Vegetation planting can be

carried out to either create a new habitat or strengthen an existing one.

Coastal vegetation can be of many different types, such as mangroves, different

types of wetlands and seagrass, all of which are important habitats for a variety of

species. The natural systems present in the Study Area are generally composed of

sandy/shingle beaches with adjacent dune systems or slopes of soil or rock nature.

In these systems, a suitable measure to complement the proposed solutions, both in

terms of coastal protection and ecological enhancement functions, is planting of

vegetation within the existing dunes (e.g. Greystones to Wicklow, Brittas Bay and

Arklow South Beach).

The assessment of the suitability of vegetation planting and its design (e.g. species,

location, method) must be carried out during detailed design stage, including

detailed mapping of the existing species.

In this regard, there are studies being undertaken of the dune systems between

Greystones and Wicklow and in Brittas Bay at the time of writing, the conclusions

of which will be relevant for future assessments.

https://www.moore-concrete.com/civil/econcrete/

https://www.moore-concrete.com/civil/econcrete/





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Figure 16: Testing of the dampening effect of willows on wave energy at TU Delft, the

Netherlands (Source: https://www.tudelft.nl/en/2018/citg/willows-are-an-asset-in-natural-

flood-defences/)

6.6 Other additional uses

Other potential uses which can enhance the sustainability of the proposed options

are the creation of mussel farms, areas for tidal energy, solar energy, etc. These

enhancements can be assessed further during development of the preferred option.

6.7 Nourishment sources

Several of the solutions that result from this study involve the provision of large

amounts of sediment material.

The approach that is generally followed is to obtain this material from designated

areas located offshore, at a relatively short distance from the site, by dredging

activities. This extraction implies disturbance of the existing environment in the

dredged areas, as well as associated costs. In addition, the permissions required to

undertake these activities at a specific site may cause significant delays to the

works.

In order to achieve a more sustainable use of natural resources but also to reduce

construction costs and minimize planning delays, it is proposed that alternative

sourcing solutions are assessed in future project stages.

For example, due to the natural deposition of sediment material immediately south

of Bray Harbour caused by the presence of the harbour structures, a potential

solution would be the creation of a by-pass system to redistribute this material

towards the north.

https://www.tudelft.nl/en/2018/citg/willows-are-an-asset-in-natural-flood-defences/

https://www.tudelft.nl/en/2018/citg/willows-are-an-asset-in-natural-flood-defences/





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Other possible sources come from the maintenance dredging activities that are

frequently carried out along and near the Study Area (e.g. in Dublin Port, Bray

Harbour, Arklow or Wicklow Harbour).





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7 Options and feasibility assessment for long

term

7.1 Introduction

This section presents a summary of the options and feasibility assessment that has

been carried out for each of the CCAs following the methodology explained in

Section 4. As outlined previously, the focus of the assessment is the identification

of the most suitable, operationally viable and site-specific solutions with regard to

social, environmental, cultural and heritage, economic and infrastructure aspects.

The analysis that has been undertaken for each of the CCAs is presented separately

in standalone sub-sections. Within each sub-section, the preliminary options

considered for that particular CCA are outlined, followed by the definition of the

options that were chosen for the MCA. The results of the MCA are summarised,

with reference to Appendix B, where the complete MCA analyses are presented.

Finally, the preferred option arising from the MCA is discussed in more detail at

the end of the sub-section.

Note that the assessment related to the coastal erosion risk. Risks relating to coastal

flooding, overtopping and geotechnical issues were considered at a high-level only.

Any proposals relating to these risks will require further detailed assessment.

7.2 CCA1 – Merrion to Dun Laoghaire

7.2.1 Preliminary assessment

There is no evidence of coastal erosion in this CCA. Therefore, no further measures

are required from the coastal management point of view.

The main risks identified along this area relate to coastal flooding due to

overtopping of existing structures, as well as damage or collapse of the existing

defences during storm events, which can impact on adjacent infrastructure such as

rail and road infrastructure, private properties and public facilities. Thus, these risks

have an economic and social impact because of the disruption of transport services

and physical damage. Potential impacts on the surrounding environment (South

Dublin Bay, Booterstown Marsh) and cultural heritage are also encountered. A high

level assessment for the options which advance the line and also address flooding

due to overtopping has been developed.

For more details on the identified risks and associated impacts, refer to WP6.

Detailed Risk Assessment.

The approach for this CCA consists of assessing potential solutions that help to

stabilise or increase the area of the emerged beach and which will also have an

impact on the reduction of the overtopping risk. At the preliminary options

assessment stage, the following options were considered to mitigate the coastal

risks identified for CCA1:





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• ‘Do nothing’

• ‘Do minimum’

• Proactive maintenance of

existing defences

• Complete/partial upgrade of

defences

• New vertical structures

• Detached breakwater system

• Beach nourishment

• Large scale nourishment

• Reclamation

• Dune regeneration

Following the preliminary options assessment, the options shown above in italics

were discarded.

“Do minimum” does not involve any capital works. Given the identified risks in the

area, this may mean that the do-minimum is actually the same as do-nothing in the

medium/long term when it is no longer feasible to continue maintaining the

defences and/or it is not sufficient. Thus, in this case the “Do minimum” option

does not provide any further advantage in comparison with the “Do nothing” option

(the baseline for the options assessment) and it has therefore been discarded in this

preliminary assessment.

Proactive maintenance alone was not considered a viable option as this solution

does not provide for a definite standard of protection in the long term. Similarly,

beach nourishment and dune regeneration at a local scale are not considered

sufficient to mitigate the existing risks as a standalone measure. However, these

solutions have been proposed as additional considerations/measures to strengthen

the functionality of other protection measures.

Relocation of the railway line in this area is not considered viable as it would

involve significant costs given its location in an urban area and would not address

the other risks identified i.e. damage to existing property, public facilities and road

infrastructure.

7.2.2 Definition of options

Five options, in addition to the ‘do nothing’ option have been progressed to the

options assessment. These are presented graphically in Figure 17 to Figure 21.

The dimensions and location of the protection measures shown in the figures are

indicative only. These details will be defined at detailed design stage.

Option 1: ‘Do nothing’

No coastal protection interventions carried out in the area.





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Option 2

Figure 17: Graphical representation of Option 2 for CCA1.

Option 3






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Option 4


Option 5






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Option 6

Figure 21: Graphic representation of Option 6 for CCA1.

7.2.3 MCA

A summary of the results from the MCA for CCA1 is presented in Table 2.

The complete MCA matrix is provided in Appendix B1.

Table 2: Summary of MCA results for CCA1.

Option Percentage

score

Ranking

Option 1: ‘Do nothing’ 54% 6

Option 2: Partial upgrade of defences 71% 2

Option 3: Complete upgrade of defences 71% 3

Option 4: Detached breakwaters and beach nourishment 73% 1

Option 5: Large scale nourishment 69% 4

Option 6: Reclamation 63% 5

7.2.4 Preferred option

Based on the MCA results the preferred option for CCA1 is:

Option 4: Detached breakwaters and beach nourishment.

This option considers the development of a system of detached breakwaters with

the purpose of dissipating the incident wave energy before it reaches the shoreline.

The number and dimensions of the breakwaters are to be designed based on detailed

studies to ensure an appropriate interaction with the existing coastal processes. It is

proposed that these are designed to form an hemitombolo in the beach (see Figure

22).





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This preferred option intends to reduce wave overtopping by a combination of

dissipation of wave energy and raised beach levels which will prevent wave action

to affect the existing coastal defences along the railway line.

Figure 22: Key variables for nearshore breakwater scheme. Salient (hemitombolo)

formation. (Source: Modelling the effect of nearshore detached breakwaters on sandy

macro-tidal coasts, DEFRA)

Additional measures

The following additional measures are suggested to complement the adopted

solution and strengthen the functionality of the protection measures.

• Beach nourishment is proposed in order to facilitate and accelerate the creation

of hemitombolos and regenerate beach levels which will be protected by the

detached breakwaters system. Nourishment would extend along the entire

CCA1 coastline to provide a unified system.

• Dune regeneration is proposed adjacent to the Merrion Gates to encourage the

creation or enlargement of the existing embryonic dune system. Different

techniques should be considered, such as dune planting, fencing and placement

of warning and educational signs.

Additional considerations

There are a number of additional considerations that will need to be taken into

account and are proposed to be included as part of the solutions proposed in this

area. Additional considerations include the following:

• Proactive maintenance is to be provided to the existing structures in area CCA1.





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Maintenance requirements are to be informed by regular monitoring and

assessment of structural and geotechnical conditions, especially in structures

rated as ‘poor’ and ‘very poor’ condition.

• A monitoring programme should be implemented in order to evaluate the

sediment transport regime and evolution of the coastal cells, in particular, the

beach nourishment material. The beach nourishment scheme is to be adapted

over time if needed based on the results of the monitoring programme.

7.3 CCA2-3 – Dalkey Tunnel to Killiney Station and

Killiney South


CCA2 and CCA3 have been considered together as one coastal cell, CCA2-3, due

to their proximity and based on the coastal processes and evolution identified in

WP4. Assessment of Existing Coastal Process and Coastline Evolution.

The identified risks for this area mainly related to coastal erosion (south of

Whiterock) as well as geotechnical-related issues leading to slope instability at

Killiney station. The associated impacts relate to loss of beach and structural

damage to private properties and public facilities, as well as structural damage of

existing rail (south of Killiney station) and road (access roads to private properties)

infrastructure. These could lead to significant economic and social impacts due to

the disruption of transport services and physical damage. In addition, there are

potential impacts on Irish Geological Heritage (IGH) sites (Whiterock, Killiney

Bay). Therefore, it is recommended that geotechnical studies and site investigations

are carried out to assess the slope stability and measures needed. These studies are

outside the present Feasibility study by Arup.



At the preliminary options assessment stage, the following options were considered

to mitigate the coastal erosion risks identified for CCA2-3:




existing defences

• New revetment structure




• Groyne system


were discarded.




defences and/or it is not sufficient.





Page 33

Thus, in this case the “Do minimum” option does not provide any further advantage

in comparison with the “Do nothing” option (the baseline for the options

assessment) and it has therefore been discarded in this preliminary assessment.


does not provide for a definite standard of protection. Similarly, beach nourishment

at a local scale is not considered sufficient to mitigate the existing risks as a

standalone measure. However, these solutions have been proposed as additional

considerations/measures to strengthen the functionality of other protection

measures.

Relocation of the railway line in this area is not considered viable as it would

involve significant costs and would not address the other risks identified i.e. damage

to existing property, public facilities and road infrastructure.








Option 2

Figure 23: Graphical representation of Option 2 for CCA2-3.





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Option 3


Option 4






Page 35

Option 5


Option 6






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7.3.3 MCA



Table 3: Summary of MCA results for CCA2-3.

Option Percentage

score

Ranking


Option 2: Proactive maintenance of existing defences (Whiterock)

and localised revetment (near Killiney station)

74% 2

Option 3: Detached breakwaters and beach nourishment (full cell) 65% 5

Option 4: Detached breakwaters and beach nourishment (Whiterock

only)

76% 1

Option 5: Groyne system and beach nourishment (Whiterock only) 73% 3

Option 6: Proactive maintenance (Whiterock) and large beach

nourishment

71% 4


Based on the MCA results the preferred option for CCA2-3 is:

Option 4: Detached breakwaters and beach nourishment (Whiterock only).

This option considers the development of a system of detached breakwaters near

Whiterock with the purpose of dissipating the incident wave energy before it

reaches the existing defences/embankment toe. Detached breakwaters have been

proposed only in the area where the model predicts erosion of the coastline for the

future scenarios.



proposed that these are designed to form a hemitombolo on the beach.

Additional measures

Beach nourishment is proposed in order to facilitate and accelerate the creation of

hemitombolos and regenerate beach levels which will be protected by the detached

breakwaters system. Nourishment would extend along the areas adjacent to the

detached breakwaters near Whiterock.





• Proactive maintenance is to be provided to the existing structures in area CCA2-

3. Maintenance requirements are to be informed by regular monitoring and







Page 37



beach nourishment material and evolution of the coastline in the south of the

coastal cell, where offshore breakwaters have not been proposed. The beach

nourishment scheme is to be adapted over time if needed based on the results of

the monitoring programme.

• Geotechnical studies and site investigations should be carried out to assess the

slope stability and measures needed to ensure the slope stability of the area of

Killiney station and adjoining cliffs of all the area (CCA2-3) which has been

assessed as a key risk.

7.4 CCA4 – Bray North


A number of options have been assessed to mitigate the coastal risks identified for

this area. The associated impacts relate to possible damage/ collapse of the existing

railway infrastructure, further exposure of existing landfill and damage/ loss of

property area at the existing golf facilities. For more details, refer to WP6. Detailed

Risk Assessment.

At the preliminary options assessment stage, the following options were considered:



• Beach nourishment programme


• Groyne system



were discarded.








The development of large-scale nourishment (e.g. an artificial island or a sand

engine) could potentially cause sedimentation issues in Bray Harbour particularly

at the harbour entrance. To prevent this, additional structures would need to be

designed. As no significant benefits have been identified in comparison with other

options to justify this solution, this option has been discarded.

At a local scale, beach nourishment is not considered sufficient to mitigate the

existing risks as a standalone measure. However, this solution has been proposed

as a additional measure to strengthen the functionality of other protection measures.





Page 38

Finally, relocation of the railway line in this area is not considered viable as it would

involve significant costs for the long term timeframe scenario (year 2100) and

would not address the other risks identified i.e. landfill exposure and damage to

existing property.


Three options, in addition to the ‘do nothing’ option have been progressed to the






Option 2






Page 39

Option 3


Option 4






Page 40

7.4.3 MCA




Option Percentage

score

Ranking


Option 2: Revetment extension and beach nourishment 76% 1

Option 3: Detached breakwater system and beach nourishment 69% 3

Option 4: Groyne system and beach nourishment 73% 2



Option 2: Revetment extension and beach nourishment.

This option involves the development of a sloping rock revetment structure that

would tie in with the existing rock revetment located immediately north of Bray

Harbour extending up to the southern end of the golf course facilities.

Additional measures

In order to prevent a possible reduction of beach levels that is often associated with

the introduction of ‘hard’ structures, this option also involves the placement of

beach nourishment material in front of the new revetment. Nourishment would

extend towards the north to minimise localized erosion that would be expected

adjacent to the northern end of the structure, as well as to the south to provide a

unified system.







assessment of structural and geotechnical conditions.


sediment transport regime and evolution of the coastal cells, in particular, to

evaluate any accelerated erosion in the adjoining areas. The beach nourishment

scheme is to be adapted over time if needed based on the results of the

monitoring programme.

• Public safety throughout the structure’s design life: Signage to be placed in the

area to prevent people from walking across the structure. Beach access areas are

to be clearly defined.





Page 41

• Appropriate management of the existing landfill to mitigate the existing

contamination hazard is required.

7.5 CCA5 – Bray Head to Greystones North Beach


In the north of CCA5 at Bray Head, several coastal defences have been noted to be

at risk of damage or collapse.

In the south of CCA5 at the northern end of Greystones North Beach, the natural

soil cliffs have been noted to be at risk of retreating due to a combination of

geotechnical causes and wave action. The retreat of these cliffs could ultimately

cause, amongst others, damage and/or collapse of the existing railway infrastructure

(tunnel of Bray Head) and the Bray-Greystones cliff walk (with subsequent

significant health and safety issues) as well as damage to surrounding

environmental and cultural heritage sites.




in order to mitigate the coastal risks identified for this area.:


• Upgrade of Bray Head structures



existing defences)



• Groyne system


• Relocation of railway


were discarded.










at a local scale is not considered sufficient to mitigate the existing risks as a

standalone measure. However, these solutions have been proposed as additional

considerations/measures to strengthen the functionality of other protection

measures.





Page 42

The deployment of a large-scale nourishment scheme was discarded for the

southern area of CCA5, as this would not provide definitive protection against the

risk of erosion in such a dynamic coastal cell. This is apparent from Arup’s ongoing

monitoring of this coastal cell through a separate commission. This option is also

not suitable in the north of CCA5 due to deep waters immediately offshore of Bray

Head which results in a larger local wave climate and would also require a

prohibitive amount of nourishment material to provide an appropriate level of

protection.


Four options in addition to the ‘do nothing’ option have been progressed to the






Option 2






Page 43

Option 3


Option 4






Page 44

Option 5


7.5.3 MCA




Option Percentage

score

Ranking


Option 2: Upgrade/maintenance of structures (Bray Head) +

Revetment and beach nourishment (Greystones North Beach)

72% 2

Option 3: Upgrade/maintenance of structures (Bray Head) +

Detached breakwater system and beach nourishment (Greystones

North Beach)

75% 1

Option 4: Upgrade/maintenance of structures (Bray Head) + Groyne

system and beach nourishment (Greystones North Beach)

70% 3

Option 5: Relocation of railway line 32% 5





Page 45



Option 3: Upgrade/maintenance of structures (Bray Head) + Detached breakwater

system and beach nourishment (Greystones North Beach).

This option considers proactive maintenance and/or upgrade of the existing

structures for the northern part of CCA5 at Bray Head, in the area where the model

predicts erosion of the coastline for the medium (year 2050) and long term (year

2100) timeframe scenarios and there is a risk of the erosion affecting the current

tunnel at Bray Head. For the southern part of CCA5, this option involves the

development of a system of detached breakwaters located at the northern extent of

Greystones North Beach parallel to the shoreline with the purpose of dissipating the

incident wave energy before it reaches the shoreline and avoid any potential scour

of the toe of the cliffs by wave action.



proposed that these are designed to form an hemitombolo in the beach.

Additional measures

Beach nourishment is proposed in order to facilitate and accelerate the creation of

hemitombolos and regenerate beach levels which will be protected by the detached

breakwaters system. Nourishment would extend slightly towards the north and the

south of the protected beach to provide a unified system.













• Detailed geotechnical studies of the existing structures at Bray Head are

recommended, particularly those that have been noted to be in poor condition

and very poor condition. In addition, a geotechnical assessment of the slopes

along Greystones North Beach is also recommended to be undertaken to assess

to assess the nature of the soils that comprise these, geotechnical causes for

erosion and slope instability (including any potential drainage issues that could

accelerate the erosion processes) and assessment of potential slope stabilisation

techniques.





Page 46

7.6 CCA6 – Greystones to Wicklow Harbour

Area CCA6 is considered to be at risk of coastal erosion and breach/collapse of

existing defences. The key impacts that these risks pose relate to the structural

damage and/or collapse of existing structures such as public facilities, private

properties and rail infrastructure between Greystones and Wicklow, with the

subsequent economic and social impacts associated with disruption of transport

infrastructure services and physical damage. There are also potential impacts on the

surrounding environment (The Murrough, Wicklow Town Sites), human health and

life and cultural heritage.



Area CCA6 has been split into two smaller areas due to the complexity and length

of this stretch of coastline. In addition, the assessment of coastal processes

undertaken as part of WP4. Assessment of Existing Coastal Process and Coastline

Evolution indicate that this section of coast has a natural split between coastal cells

at circa Six Mile Point adjacent to the Newcastle Aerodrome. The two sub sections

have been divided as follows:

• CCA6.1 – Greystones to Newcastle;

• CCA6.2 – Newcastle to Wicklow Harbour.

7.6.1 CCA6.1 – Greystones to Newcastle

7.6.1.1 Preliminary assessment

Several options have been assessed to mitigate the coastal erosion risks on CCA6.1.





existing defences




• Groyne system

• Relocation of railway line



were discarded.












Page 47



and dune regeneration at a local scale are not considered sufficient to mitigate the

existing risks as a standalone measure. However, these solutions have been

proposed as additional considerations/measures to strengthen the functionality of

other protection measures.

The development of a large-scale nourishment scheme (e.g. an artificial island or a

sand engine) was excluded from the analysis due to the nature of the coastline, the

coastal processes identified in WP4. Assessment of Existing Coastal Process and

Coastline Evolution and the fact that there are no natural retaining structures e.g. a

rock headland. In addition, the significant length of coastline would require a

prohibitive amount of nourishment material in to provide the appropriate level of

protection. For these reasons and as no significant benefits have been identified in

comparison with other options to justify this solution, this option has been

discarded. However, the offshore breakwater solution if selected, could lead to a

subsequent refinement at scheme design stage involving consideration of extended

offshore breakwaters incorporating some of the principles of offshore islands (e.g.

extended surface, new area of habitat for flora and fauna, etc).

7.6.1.2 Definition of options

Four options, in addition to the ‘do nothing’ option have been progressed to the










Page 48

Option 2

Figure 35: Graphical representation of Option 2 for CCA6.1.

Option 3






Page 49

Option 4


Option 5






Page 50

7.6.1.3 MCA

A summary of the results from the MCA for CCA6.1 (North) is presented in Table

6.


Table 6: Summary of MCA results for CCA6.1 (North).

Option Percentage

score

Ranking


Option 2: Extension of revetment, proactive maintenance and beach

nourishment

71% 3

Option 3: Detached breakwater system, beach nourishment and

proactive maintenance

78% 1

Option 4: Groyne system, beach nourishment and proactive

maintenance

74% 2


7.6.1.4 Preferred option

Based on the MCA results the preferred option for CCA6.1 is:

Option 3: Detached breakwater system, beach nourishment and proactive

maintenance.

This option considers proactive maintenance of all existing structures between

Greystones and Newcastle. Adjacent to 17 Mile Point the proposed solution

consists of a system or single offshore breakwater located parallel to the coastline.

Between the southern extent of the rock armour revetment and Newcastle a further

system of offshore breakwaters is proposed with an exclusion zone adjacent to the

Breaches. The purpose of the offshore breakwaters is to dissipate the incident wave

energy effectively reducing the nearshore wave climate.

This option which protects the coastline for coastal erosion will also help to protect

the existing area from flooding due to coastal overtopping due to the extended

emerged beach area and beach levels raised as a result of the beach nourishment.




Additional measures





detached breakwaters system. Nourishment would extend slightly towards the

north and the south of the protected beach to provide a unified system.





Page 51

• Dune regeneration is proposed to encourage the creation or enlargement of the

existing dune system. Different techniques should be considered, such as dune

planting, fencing and placement of warning and educational signs.





• Proactive maintenance is to be provided to the existing structures between 17

Mile Point and Greystones town. Maintenance requirements are to be informed

by regular monitoring and assessment of structural and geotechnical conditions





7.6.2 CCA6.2 – Newcastle to Wicklow Harbour

7.6.2.1 Preliminary assessment

Several options have been assessed to mitigate the coastal erosion risks on CCA6.2.




• Upgrading of existing defences




• Relocation of railway line



were discarded.








As per area CCA6.1, the development of a large-scale nourishment scheme (e.g. an

artificial island or a sand engine) was discarded from the MCA due to the due to

the nature of the coastline, the coastal processes identified in WP4. Assessment of

Existing Coastal Process and Coastline Evolution and the fact that there are no

natural retaining structures e.g. a rock headland.

In addition, the significant length of coastline would require a prohibitive amount

of nourishment material in to provide the appropriate level of protection.





Page 52

Beach nourishment and dune regeneration at a local scale are not considered

sufficient to mitigate the existing risks as a standalone measure. However, both

have been proposed as additional measures to strengthen the functionality of other

protection measures.

Finally, system of groynes was excluded from the analysis due to the significant

impact they could have on the existing natural sediment transport system and

processes combined with the expected significant environmental impacts.

7.6.2.2 Definition of options







Option 2






Page 53

Option 3


Option 4






Page 54

Option 5


Option 6






Page 55

7.6.2.3 MCA

A summary of the results from the MCA for CCA6.2 (South) is presented in Table

7.


Table 7: Summary of MCA results for CCA6.2 (South).

Option Percentage

score

Ranking


Option 2: Upgrade of revetment, extension of revetment and


55% 4

Option 3: Detached breakwater system, beach nourishment and


73% 2

Option 4: Upgrade of revetment, extension of revetment, detached

breakwater system, beach nourishment and proactive maintenance

76% 1

Option 5: Upgrade of revetment, extension of revetment, proactive

maintenance, offshore breakwaters and beach nourishment

65% 3


7.6.2.4 Preferred option

Based on the MCA results the preferred option for CCA6.2 is:

Option 4: Upgrade of revetment, extension of revetment, detached breakwater

system, beach nourishment and proactive maintenance.

The proposed option consists of proactive maintenance of the existing revetment

structure in the northern section between Newcastle and Kiloughter. This is to be

combined with a system of detached breakwaters located parallel to the coastline,

with the purpose of dissipating the incident wave energy before it reaches the

shoreline.




This option considers proactive maintenance of the existing revetment at northern

section and/or upgrade of the existing revetment located north of Wicklow harbour.

This option also includes the development of a sloping revetment structure that

would tie in with the existing revetment located immediately north of Wicklow

Harbour and would extend north circa 600 meters, protecting a particularly

vulnerable area due to the proximity of the railway line.

Additional measures







Page 56



detached breakwaters system. Nourishment would extend slightly towards the

north and the south of the protected beach (including the existing revetment area

at the northern section) to provide a unified system.

• Dune regeneration is proposed to encourage the creation or enlargement of the

existing dune system. Different techniques should be considered, such as dune

planting, fencing and placement of warning and educational signs.





• Proactive maintenance is to be provided to the existing structures between

Newcastle and Wicklow Harbour. Maintenance requirements are to be informed

by regular monitoring and assessment of structural and geotechnical conditions.





• Public safety throughout the structure’s design life: Signage to be placed in the

area to prevent people from walking across the structure. Beach access areas are

to be clearly defined.

7.7 CCA7 – Wicklow Harbour

As outlined in the Detailed Risk Assessment report, no significant risks have been

identified within this area due to the protection provided by the existing harbour

structures (Wicklow town) as well as the presence of rock cliffs of significant height

(eastern part of the cell).

Therefore, this CCA has been excluded from the options and feasibility assessment.

7.8 CCA8 – Arklow North Beach


A number of options have been assessed to mitigate the coastal erosion risks

identified for CCA8. The main risks identified along this coastline relate to coastal

erosion along most of the coastal cell and damage or collapse of the existing

defences during storm events.

These risks could potentially affect a range of infrastructure, such as the road

network, private properties and public facilities, with the subsequent economic and

social impact. Potential impacts on the surrounding environment (Arklow Town

Marsh, Arklow Sand Dunes and natural wetlands) are also encountered.





Page 57






• Upgrade existing revetment




• Groyne system



were discarded.








Beach nourishment and dune regeneration at a local scale are not considered


solutions have been proposed as additional measures to strengthen the functionality

of other protection measures.












Page 58

Option 2


Option 3






Page 59

Option 4


Option 5






Page 60

7.8.3 MCA




Option Percentage

score

Ranking


Option 2: Upgrade of existing revetment 64% 4

Option 3: Offshore breakwater system and beach nourishment 79% 1


Option 5: Large scale nourishment 69% 3



Option 3: Offshore breakwater system and beach nourishment.

This option considers the development of a system of detached breakwaters with

the purpose of dissipating the incident wave energy before it reaches the existing

defences. A retaining structure located south of the Arklow Sand Dunes is also

proposed to prevent loss of material.

The number and dimensions of the breakwaters and retaining structure are to be

designed based on detailed studies to ensure an appropriate interaction with the

existing coastal processes. It is proposed that offshore breakwaters are designed to

form a hemitombolo on the beach.

Additional measures



• Beach nourishment is proposed in order to regenerate beach levels which will

be protected by the detached breakwaters system. Nourishment would extend

along the entire CCA8 coastline to provide a unified system.

• Dune regeneration is proposed at the Arklow Sand Dunes area to encourage the


techniques should be considered, such as dune planting, fencing and placement

of warning and educational signs.









Page 61



assessment of structural and geotechnical conditions. The existing revetment

could be replaced in the future by soil embankments or other structures.



beach nourishment material and dune system. The beach nourishment scheme

is to be adapted over time if needed based on the results of the monitoring

programme.

7.9 CCA9 – Arklow Harbour

The assessment related to this CCA is covered in under CCA8 and CCA10 in Sections

7.8 and 7.10 respectively.

7.10 CCA10 – Arklow South Beach


A number of options have been assessed to minimise the coastal erosion risks

identified for this area. The impacts associated to these risks relate to damage to the

existing golf club facilities, carpark and access roads as well as damage and/or

collapse of the existing structures along the beach and the quarry facilities.




to mitigate the coastal erosion risks identified for CCA10:



• Upgrade/maintenance of existing

structures


• Large-scale nourishment

• Groyne system




were discarded.












Page 62

At a local scale, beach nourishment and dune regeneration are not considered


solutions have been proposed as additional measures to strengthen the functionality

of other protection measures.








Option 2






Page 63

Option 3


Option 4






Page 64

Option 5


7.10.3 MCA

A summary of the results from the MCA for CCA10 is presented in Table 9



Option Percentage

score

Ranking


Option 2: Upgrade of existing revetment and beach nourishment 70% 4

Option 3: Offshore breakwater system and beach nourishment 70% 3


Option 5: Large-scale nourishment 84% 1







Page 65

Option 5: Large-scale nourishment.

This option considers the placement of large volumes of sediment along the shore

and its surroundings. Once the material is in place, this solution is thought to evolve

by natural processes, relying on the natural sediment transport processes.

Given the high dependence of this coastal protection measure on the climate and

sediment transport regime, the definition of the large-scale nourishment scheme

should be based on detailed modelling studies.

Beach nourishment is a very suitable solution for this cell. There is only limited

infrastructure so the stability of the beach nourishment can be monitored and

maintenance adjusted. A beach nourishment scheme can also be easily amended to

larger or lesser interventions in the future as decisions are made about either

upgrading or downgrading/re-routing the coast road which could result in changing

to a do-nothing scenario where the coast is left to erode.

This option which protects the coastline for coastal erosion will also help to protect

the existing area from flooding due to coastal overtopping due to the extended

emerged beach area and beach levels raised as a result of the beach nourishment.

This solution also requires the establishment of a monitoring system due to the high

level of uncertainty associated with the evolution of this solution. However, very

limited intervention or management after the initial placing of material is expected

to be required.

Additional measures

Dune regeneration is proposed adjacent to the industrial facilities to encourage the


techniques should be considered, such as dune planting, fencing and placement of

warning and educational signs.





• Proactive maintenance is to be provided to the existing structures in area

CCA10. Maintenance requirements are to be informed by regular monitoring

and assessment of structural and geotechnical conditions.



large-scale nourishment material and dune system. The beach nourishment

scheme is to be adapted over time if needed based on the results of the

monitoring programme.





Page 66

7.11 CCA11 – Brittas Bay


The main risks identified in CCA11 are the erosion of the existing beach and dune

system due to wave action, particularly in the south, as well as the damage of the

entire dune system due to human activity. For more details on the identified risks

and associated impacts, refer to WP6. Detailed Risk Assessment.


to mitigate the coastal erosion risks identified for CCA11:






were discarded.








Large-scale nourishments, groyne system and detached breakwater systems were

excluded from the analysis due to the significant impact they could have on the

existing natural system and processes, of significant environmental value.


Two options in addition to the ‘do nothing’ option have been progressed to the

options assessment. These are graphically presented in Figure 52 and Figure 53.









Page 67

Option 2


Option 3






Page 68

7.11.3 MCA




Option Percentage

score

Ranking


Option 2: Dune management (protection and planting) 74% 1

Option 3: Beach nourishment programme 64% 2



Option 2: Dune management (protection and planting).

This option considers the implementation of a planting programme to strengthen

the stability of the dune system as well as the deployment of different measures to

protect the system from human activity. The latter includes the placement of fences

(typically made of wood) along the dune system boundaries, placement of warning

and educational signage and the definition of beach access points.


This option requires special consideration in terms of climate change resilience and

adaptability. In this regard, a monitoring programme should be implemented in

order to evaluate the sediment transport regime and evolution of the coastal cells,

in particular, the beach material and dune system. This will define potential

measures that may be required in the future.





Page 69

8 Short term measures

8.1 Additional studies

Additional studies are recommended as part of the short term measures. The

proposed additional studies include the following:

• Geotechnical studies and site investigations should be carried out to assess the

slope stability and measures needed to ensure the slope stability of the area of

Killiney station and adjoining cliffs of all the area (CCA2-3) which has been

assessed as a key risk.

• Detailed geotechnical studies of the existing structures at Bray Head (CCA5)

are recommended, particularly those that have been noted to be in poor and very

poor condition. In addition, a geotechnical assessment of the slopes along

Greystones North Beach is also recommended to be undertaken to assess the

nature of the soils that comprise these, geotechnical causes for erosion and slope

instability (including any potential drainage issues that could accelerate the

erosion processes) and assessment of potential slope stabilisation techniques.

8.2 Repairs

The following actions are recommended:

• Appropriate measures to repair the assets identified as ‘poor’ (Significant

structural defects, i.e., out-of-tolerance faults) and ‘very poor’ (seriously

deficient, mitigation measures necessary) in WP3. Surveys of Existing Coastal

Protection Measures are undertaken.

• Regular maintenance of all the existing assets.

• The implementation of recommendations arising from the proposed

geotechnical studies.





Page 70

9 Conclusions

A summary of the preferred options identified for each of the CCAs is provided in

Table 11.

Table 11: Summary of preferred options

Coastal

cell area

number

Coastal cell area

description

Option

Number Option description

CCA1 Merrion to Dun

Laoghaire

4 Detached breakwaters and beach

nourishment

CCA2-3 Dalkey Tunnel to

Killiney Station

4 Detached breakwaters and beach

nourishment (Whiterock only)

CCA4 Bray North (Former

landfill Site)

2 Extension of revetment structure and beach

nourishment

CCA5 Bray Head to Greystones

North Beach

3 Upgrade/ maintenance of Bray Head

structures, detached breakwater system and

beach nourishment at Greystones North

Beach

CCA6.1 Greystones to Newcastle 3 Detached breakwater system, beach

nourishment and proactive maintenance

CCA6.2 Newcastle to Wicklow 4 Upgrade of revetment, extension of

revetment, detached breakwater system,

beach nourishment and proactive

maintenance

CCA8 Arklow North Beach 3 Offshore breakwater system and beach

nourishment

CCA10 Arklow South Beach 5 Large-scale nourishment

CCA11 Brittas Bay 2 Dune management (protection and planting)

Note that additional measures to the preferred options like beach nourishment and

dune regeneration have been proposed as described for each CCA. Similarly,

additional considerations such as further studies, proactive maintenance and

monitoring programmes have been proposed for each of the preferred options.

For the purposes of this study, it has been assumed that the sediment material to be

used for beach nourishment will be sourced from a variety of sources such as local

areas offshore, local quarries of dredged material from nearby ports and harbours

as described in Section 6.7.

The subsequent Work Packages of this study will involve further detailed

assessment of the preferred options detailed in this report.

Appendix A

MCA criteria



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Page A1

A1 MCA criteria

The criteria that was followed for the development of the Multi-Criteria Analysis is presented in Table 12.

Table 12: Scoring criteria for the MCA.


weighting


weighting

Description Objective scoring

Economic 25% Assets 30% Minimise damages and/or losses relating to

(permanent and temporary) private and public

property such as residential, industrial and/or

commercial property, caravan parks, public buildings

(e.g. schools, hospitals) sewage and water supply

networks, pipelines, etc.

1 - Major damage to assets

2 - Significant damage to assets

3 - Moderate damage to assets

4 - Minor damage to assets

5 - No damage to assets

Land use 20% Minimise damages to land used for agricultural,

industrial, urban, forestry and commercial fisheries

purposes.

1 - Major damage to lands

2 - Significant damage to lands

3 - Moderate damage to lands

4 - Minor damage to lands

5 - No damage to lands

Infrastructure 50% Minimise risk to transport infrastructure (e.g. roads,

rail, ports, harbours, etc.)

1 - 0% of transport routes at risk protected





Social 15% Health and safety

(construction)

30% Minimise health and safety risk and effect of options

during construction.

1 - Major health and safety risk during construction

2 - Significant health and safety risk during construction

3 - Moderate health and safety risk during construction

4 - Minor health and safety risk during construction

5 - No health and safety risk during construction

Health and safety

(design life)

30% Minimise resultant health and safety risk and effect

of options during design life.

1 - Major health and safety risk during design life

2 - Significant health and safety risk during design life

3 - Moderate health and safety risk during design life




Page A2


weighting


weighting


4 - Minor health and safety risk during design life

5 - No health and safety risk during design life

Community 10% Minimise risk to social infrastructure (e.g. schools

and educational facilities, libraries, community

centres, local and central government offices,

emergency services facilities, health centres (other

than hospitals and nursing homes), religious centres,

sports facilities, playgrounds, local cultural heritage

sites, etc.) and Local Employment.

1 - Major risk to social infrastructure assets

2 - Significant risk to social infrastructure assets

3 - Minor risk to social infrastructure assets

4 - Negligible risk to social infrastructure assets

5 - No risk to social infrastructure assets

Access 15% Protect existing, and where possible create new

access (e.g. access to the beach from the hinterland,

access to adjoining beaches, coves, headlands,

maintenance of continuity of walking routes).

1 - Major impact on existing access sites

2 - Moderate impact of existing access sites

3 - All existing access sites protected

4 - Existing access sites protected with some enhancement

5 - Existing access protected and significantly enhanced

Social and

recreation

facilities

15% Protect existing, and where possible create new

social, recreational and community facilities (e.g.

creation of new beach or extended beach area).

1 - Major impact on existing social amenity sites

2 - Moderate impact of existing social amenity sites

3 - All existing social amenity sites protected

4 - Existing social amenity sites protected with some

enhancement

5 - Existing social amenity sites protected and significantly

enhanced

Environmental

& heritage

20% Ecology,

Habitats and

Birds Directives

and flora and

fauna

50% Support the achievement of good ecological

status/good ecological potential (GES/GEP) under

the WFD.

Promote the habitats and birds directive objectives.

Avoid and where possible enhance habitats of

national, regional and local importance.

Protect and where possible enhance fisheries

resources.

1 - Major impact on environmental aspects

2 - Moderate impact on environmental aspects

3 - Protection of environmental aspects

4 - Environmental aspects protected with some enhancement

5 - Environmental aspects protected and significantly enhanced

Landscape and

visual

20% Protect, and where possible enhance, landscape

character and visual amenity.

1 - Major impact on the landscape and visual amenity

2 - Moderate impact on the landscape and visual amenity

3 - No impact on landscape and visual amenity




Page A3


weighting


weighting


4 - Moderate enhancement of the landscape and visual amenity

5 - Major enhancement of the landscape and visual amenity

Cultural heritage 10% Protect and where possible enhance known features

of cultural heritage (architectural and archaeological)

importance and their settings.

1 - Major loss of features of cultural heritage and their setting

2 - Significant loss of features of cultural heritage and their

setting

3 - Moderate loss of features of cultural heritage and their

setting

4 - Minor loss of features of cultural heritage and their setting

5 - No impact on features of cultural heritage and their setting

Licencing and

Statutory Permits

20% Need for licencing and statutory permits 1 - Potential extensive licencing requirements and high risk of

licencing not being granted

2 - Potential significant licencing requirements and moderate

risk of licencing not being granted

3 - Potential standard licencing requirements and moderate risk

of licencing not being granted

4 - Potential minor licencing requirements and low risk of

licencing not being granted

5 - Potential minimal licencing requirements and very low risk

of licencing not being granted

Technical 20% Hazard

elimination

30% Ensure option addresses coastal hazards and risks and

are operationally robust. Measure of the

effectiveness/ reliability of the option.

1 - Coastal hazards and risks 0% addressed





Constructability 30% Ensure options are technically and logistically viable

in relation to construction and are site specific

1 - Method of construction is highly complex and widespread

2 - Construction is complex and widespread

3 - Construction is moderately complex and localised

4 - Construction is routine and widespread

5 - Construction is routine and localised

Impact on

adjacent areas

20% Ensure that negative impacts (e.g. consequential

erosion adjacent to a "hard" structure) on adjoining

areas are minimised and that positive impacts are

1 - Major impact negative impact on adjoining areas

2 - Negative impact on adjoining areas

3 - No impact on adjoining areas




Page A4


weighting


weighting


maximised (e.g. reduced erosion in adjacent areas or

increase in biodiversity).

4 - Positive impact on adjoining areas

5 - Major positive impact on adjoining areas

Sustainability

and adaptability

to climate change

20% Options are sustainable (i.e. sustainably sourced

construction material) and are adaptable to current

and future climate change impacts and effects (e.g.

structure size can be increased to combat future sea

level rise, increased storminess, rising temperatures

etc.)

Options can be adapted to employ UN SDGs.

1 - Option is not sustainable or adaptable

2 - Option has minimal sustainability and minor adaptability

3 - Option is sustainable and adaptable

4 - Option is highly sustainable and adaptable

5 - Option is highly sustainable and easily adaptable

Cost 20% Capital

expenditure

75% Total cost for implementation of option 1 - Most expensive option

5 - Least expensive option

Maintenance

expenditure

25% Minimise operational costs associated with

maintenance

2 - Most expensive option

5 - Least expensive option

Appendix B

MCA analysis




Page B1

B1 CCA1

Core

Criteria

Global

Weighting

Individual

Weighting Objective Option 1 Option 2 Option 3 Option 4 Option 5 Option 6

Eco

no

mic

25%

30% Assets 1 4 5 4 4 5

20% Land use 1 4 5 4 4 5

50% Infrastructure 1 4 5 4 4 5

So

cial

15%

30% Health and safety (construction) 5 3 2 3 4 2

30% Health and safety (design life) 1 4 3 4 5 3

10% Community 1 4 5 4 4 5

15% Access 1 3 3 3 3 5

15% Social and recreation facilities 1 2 3 5 4 5

En

vir

on

men

tal

&

Her

itag

e

20%

50% Environmental Aspects (Ecology, Habitats and Birds Directives

and flora and fauna) 3 2 3 4 4 1

20% Landscape and visual 3 2 2 3 5 2

10% Cultural heritage 1 3 3 4 4 3

20% Licencing and Statutory Permits 5 4 3 2 2 1

Tec

hn

ical

20%

30% Hazard elimination 1 4 5 4 4 5

30% Constructability 5 3 2 2 4 1

20% Impact on adjacent areas 2 3 3 4 5 4

20% Sustainability and adaptability to climate change 1 2 1 4 4 5

Co

st

20% 75% Capital expenditure 5 5 3 4 1 1

25% Maintenance expenditure 5 4 5 3 2 4

Percentage score 54% 71% 71% 73% 69% 63%

Ranking 6 2 3 1 4 5

Option 1: ‘Do nothing’; Option 2: Partial upgrade of defences; Option 3: Complete upgrade of defences; Option 4: Detached breakwaters and beach nourishment; Option 5: Large scale

nourishment; Option 6: Reclamation.




Page B2

B2 CCA2-3

Core

Criteria

Global

Weighting

Individual


Eco

no

mic

25%

30% Assets 2 4 4 4 4 4

20% Land use 2 4 4 4 4 4


So

cial

15%



10% Community 2 5 5 5 5 5

15% Access 1 3 4 4 3 4


En

vir

on

men

tal

&

Her

itag

e

20%






Tec

hn

ical

20%





Co

st




Ranking 6 2 5 1 3 4

Option 1: ‘Do nothing’; Option 2: Proactive maintenance of existing defences (Whiterock) and localised revetment (near Killiney station); Option 3: Detached breakwaters and beach

nourishment (full cell); Option 4: Detached breakwaters and beach nourishment (Whiterock only); Option 5: Groyne system and beach nourishment (Whiterock only); Option 5: Proactive

maintenance (Whiterock) and large beach nourishment.




Page B3

B3 CCA4

Core

Criteri

a

Global

Weighting

Individual

Weighting Objective Option 1 Option 2 Option 3 Option 4

Eco

no

mic

25%

30% Assets 1 5 4 4

20% Land use 1 5 4 4

50% Infrastructure 1 5 5 5

So

cial

15%

30% Health and safety (construction) 5 1 4 3

30% Health and safety (design life) 1 2 4 3

10% Community 5 5 5 5

15% Access 1 3 5 4

15% Social and recreation facilities 1 3 5 4

En

vir

on

men

tal

& H

erit

age

20%

50% Environmental Aspects (Ecology, Habitats and Birds Directives and flora and fauna) 1 2 5 4

20% Landscape and visual 1 2 4 4

10% Cultural heritage 1 5 5 5

20% Licencing and Statutory Permits 5 3 1 2

Tec

hn

ical

20%

30% Hazard elimination 1 5 4 4

30% Constructability 5 4 1 2

20% Impact on adjacent areas 1 2 4 4

20% Sustainability and adaptability to climate change 1 3 4 4

Co

st

20% 75% Capital expenditure 5 5 1 3

25% Maintenance expenditure 5 4 2 3

Percentage score 49% 76% 69% 73%

Ranking 4 1 3 2

Option 1: ‘Do nothing’; Option 2: Extension of revetment and beach nourishment; Option 3: Detached breakwater system and beach nourishment; Option 4: Groyne system and beach

nourishment.




Page B4

B4 CCA5

Core

Criteria

Global

Weighting

Individual

Weighting Objective Option 1 Option 2 Option 3 Option 4 Option 5

Eco

no

mic

25%

30% Assets 1 5 4 4 1

20% Land use 1 5 3 4 1

50% Infrastructure 1 5 4 4 5

So

cial

15%

30% Health and safety (construction) 5 3 4 3 1

30% Health and safety (design life) 1 3 4 3 3

10% Community 1 5 5 5 1

15% Access 1 3 5 4 1

15% Social and recreation facilities 1 2 5 4 1

En

vir

on

men

tal

&

Her

itag

e

20%

50% Environmental Aspects (Ecology, Habitats and Birds Directives and flora

and fauna) 1 2 3 2 1

20% Landscape and visual 2 2 3 2 1

10% Cultural heritage 1 5 5 5 1

20% Licencing and Statutory Permits 5 2 1 2 1

Tec

hn

ical

20%

30% Hazard elimination 1 5 4 4 1

30% Constructability 5 3 2 3 1

20% Impact on adjacent areas 5 2 4 3 1

20% Sustainability and adaptability to climate change 1 2 4 4 1

Co

st

20% 75% Capital expenditure 5 4 5 4 1

25% Maintenance expenditure 5 4 3 4 1

Percentage score 52% 72% 75% 70% 32%

Ranking 4 2 1 3 5

Option 1: ‘Do nothing’; Option 2: Upgrade/maintenance of Bray Head structures + Revetment and beach nourishment at Greystones North Beach; Option 3: Upgrade/maintenance of Bray

Head structures + Detached breakwater system and beach nourishment at Greystones North Beach; Option 4: Upgrade/maintenance of Bray Head structures + Groyne system and beach

nourishment at Greystones North Beach; Option 5: Relocation of railway line.




Page B5

B5 CCA6.1

Core

Criteria

Global

Weighting

Individual


Eco

no

mic

25%

30% Assets 1 5 4 4 1

20% Land use 1 5 4 4 1


So

cial

15%



10% Community 1 5 5 5 1

15% Access 1 4 5 4 1


En

vir

on

men

tal

&

Her

itag

e

20%






Tec

hn

ical

20%





Co

st




Ranking 4 3 1 2 5

Option 1: ‘Do nothing’; Option 2: Extension of revetment, proactive maintenance and beach nourishment; Option 3: Offshore breakwater system, beach nourishment and proactive

maintenance; Option 4: Groyne system, beach nourishment and proactive maintenance; Option 5: Relocation of railway line.




Page B6

B6 CCA6.2

Core

Criteria

Global

Weighting

Individual


Eco

no

mic

25%

30% Assets 1 5 4 5 5 1

20% Land use 1 3 3 4 3 1


So

cial

15%



10% Community 1 4 5 5 4 1

15% Access 1 3 5 5 4 1


En

vir

on

men

tal

&

Her

itag

e

20%






Tec

hn

ical

20%





Co

st




Ranking 5 4 2 1 3 6

Option 1: ‘Do nothing’; Option 2: Upgrade of revetment, extension of revetment and proactive maintenance; Option 3: Offshore breakwater system, beach nourishment and proactive

maintenance; Option 4: Upgrade of revetment, extension of revetment, offshore breakwater system, beach nourishment and proactive maintenance; Option 5: Upgrade of revetment,

extension of revetment, proactive maintenance, offshore breakwaters and beach nourishment; Option 6: Relocation of railway line.




Page B7

B7 CCA8

Core

Criteria

Global

Weighting

Individual


Eco

no

mic

25%

30% Assets 1 5 4 4 3

20% Land use 1 4 4 4 3


So

cial

15%



10% Community 1 4 5 5 4

15% Access 1 3 5 5 4


En

vir

on

men

tal

&

Her

itag

e

20%






Tec

hn

ical

20%





Co

st




Ranking 5 4 1 2 3

Option 1: ‘Do nothing’; Option 2: Upgrade of existing revetment; Option 3: Offshore breakwater system and beach nourishment; Option 4: Groyne system and beach nourishment; Option

5: Large scale nourishment.




Page B8

B8 CCA10

Core

Criteria

Global

Weighting

Individual


Eco

no

mic

25%

30% Assets 1 5 4 4 3

20% Land use 1 4 4 4 3


So

cial

15%



10% Community 1 4 5 5 4

15% Access 1 3 5 4 4


En

vir

on

men

tal

&

Her

itag

e

20%






Tec

hn

ical

20%





Co

st




Ranking 5 4 3 2 1

Option 1: ‘Do nothing’; Option 2: Upgrade of existing revetment and beach nourishment; Option 3: Offshore breakwater system and beach nourishment; Option 4: Groyne system and

beach nourishment; Option 5: Large-scale nourishment.




Page B9

B9 CCA11

Core

Criteria

Global

Weighting

Individual

Weighting Objective Option 1 Option 2 Option 3

Eco

no

mic

25%

30% Assets 2 4 4

20% Land use 1 4 5

50% Infrastructure 3 3 3

So

cial

15%

30% Health and safety (construction) 5 4 3

30% Health and safety (design life) 4 4 5

10% Community 2 5 5

15% Access 1 4 5

15% Social and recreation facilities 1 4 5

En

vir

on

men

tal

& H

erit

age

20%

50% Environmental Aspects (Ecology, Habitats and Birds Directives and flora and fauna) 2 4 3

20% Landscape and visual 2 4 5

10% Cultural heritage 5 5 5

20% Licencing and Statutory Permits 5 4 2

Tec

hn

ical

20%

30% Hazard elimination 1 3 4

30% Constructability 5 5 2

20% Impact on adjacent areas 3 4 5

20% Sustainability and adaptability to climate change 1 2 4

Co

st

20% 75% Capital expenditure 5 3 1

25% Maintenance expenditure 5 4 1

Percentage score 63% 74% 64%

Ranking 3 1 2

Option 1: ‘Do nothing’; Option 2: Dune protection and planting; Option 3: Beach nourishment programme.

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