Iarnród Éireann
Transcript of 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
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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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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.
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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
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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.
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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.
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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
Figure 18: Graphical representation of Option 3 for CCA1.
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Option 4
Figure 19: Graphical representation of Option 4 for CCA1.
Option 5
Figure 20: Graphical representation of Option 5 for CCA1.
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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
7.3.1 Preliminary assessment
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.
For more details on the identified risks and associated impacts, refer to WP6.
Detailed Risk Assessment.
At the preliminary options assessment stage, the following options were considered
to mitigate the coastal erosion risks identified for CCA2-3:
• ‘Do nothing’
• ‘Do minimum’
• Proactive maintenance of
existing defences
• New revetment structure
• Detached breakwater system
• Beach nourishment
• Large scale nourishment
• Groyne system
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.
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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. 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.
7.3.2 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 23 to Figure 27.
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.
Option 2
Figure 23: Graphical representation of Option 2 for CCA2-3.
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Option 3
Figure 24: Graphical representation of Option 3 for CCA2-3.
Option 4
Figure 25: Graphical representation of Option 4 for CCA2-3.
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Option 5
Figure 26: Graphical representation of Option 5 for CCA2-3.
Option 6
Figure 27: Graphical representation of Option 6 for CCA2-3.
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7.3.3 MCA
A summary of the results from the MCA for CCA1 is presented in Table 3.
The complete MCA matrix is provided in Appendix B2.
Table 3: Summary of MCA results for CCA2-3.
Option Percentage
score
Ranking
Option 1: ‘Do nothing’ 55% 6
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
7.3.4 Preferred option
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.
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 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.
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 CCA2-
3. 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.
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• 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 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
7.4.1 Preliminary assessment
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:
• ‘Do nothing’
• ‘Do minimum’
• Beach nourishment programme
• New revetment structure
• Groyne system
• Detached breakwater system
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.
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.
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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.
7.4.2 Definition of options
Three options, in addition to the ‘do nothing’ option have been progressed to the
options assessment. These are presented graphically in Figure 28 to Figure 30.
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.
Option 2
Figure 28: Graphical representation of Option 2 for CCA4.
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Option 3
Figure 29: Graphical representation of Option 3 for CCA4.
Option 4
Figure 30: Graphical representation of Option 4 for CCA4.
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7.4.3 MCA
A summary of the results from the MCA for CCA4 is presented in Table 4.
The complete MCA matrix is provided in Appendix B3.
Table 4: Summary of MCA results for CCA4.
Option Percentage
score
Ranking
Option 1: ‘Do nothing’ 49% 4
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
7.4.4 Preferred option
Based on the MCA results the preferred option for CCA4 is:
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.
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 CCA4.
Maintenance requirements are to be informed by regular monitoring and
assessment of structural and geotechnical conditions.
• A monitoring programme should be implemented in order to evaluate the
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.
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• Appropriate management of the existing landfill to mitigate the existing
contamination hazard is required.
7.5 CCA5 – Bray Head to Greystones North Beach
7.5.1 Preliminary assessment
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.
For more details on the identified risks and associated impacts, refer to WP6.
Detailed Risk Assessment.
At the preliminary options assessment stage, the following options were considered
in order to mitigate the coastal risks identified for this area.:
• ‘Do nothing’
• Upgrade of Bray Head structures
• ‘Do minimum’
• Proactive maintenance of
existing defences)
• Beach nourishment programme
• New revetment structure
• Groyne system
• Detached breakwater system
• Relocation of railway
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. 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.
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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.
7.5.2 Definition of options
Four options in addition to the ‘do nothing’ option have been progressed to the
options assessment. These are presented graphically in Figure 31 to Figure 34.
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.
Option 2
Figure 31: Graphical representation of Option 2 for CCA5.
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Option 3
Figure 32: Graphical representation of Option 3 for CCA5.
Option 4
Figure 33: Graphical representation of Option 4 for CCA5.
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Option 5
Figure 34: Graphical representation of Option 5 for CCA5.
7.5.3 MCA
A summary of the results from the MCA for CCA5 is presented in Table 5.
The complete MCA matrix is provided in Appendix B4.
Table 5: Summary of MCA results for CCA5.
Option Percentage
score
Ranking
Option 1: ‘Do nothing’ 52% 4
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
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7.5.4 Preferred option
Based on the MCA results the preferred option for CCA5 is:
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.
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.
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.
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 CCA5.
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.
• 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.
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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.
For more details on the identified risks and associated impacts, refer to WP6.
Detailed Risk Assessment.
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.
At the preliminary options assessment stage, the following options were considered:
• ‘Do nothing’
• ‘Do minimum’
• Proactive maintenance of
existing defences
• New revetment structure
• Beach nourishment
• Detached breakwater system
• Groyne system
• Relocation of railway line
• 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.
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Proactive maintenance alone was not considered a viable option as this solution
does not provide for a definite standard of protection. 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.
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
options assessment. These are presented graphically in Figure 35 to Figure 38.
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 35: Graphical representation of Option 2 for CCA6.1.
Option 3
Figure 36: Graphical representation of Option 3 for CCA6.1.
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Option 4
Figure 37: Graphical representation of Option 4 for CCA6.1.
Option 5
Figure 38: Graphical representation of Option 5 for CCA6.1.
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7.6.1.3 MCA
A summary of the results from the MCA for CCA6.1 (North) is presented in Table
6.
The complete MCA matrix is provided in Appendix B5.
Table 6: Summary of MCA results for CCA6.1 (North).
Option Percentage
score
Ranking
Option 1: ‘Do nothing’ 48% 4
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
Option 5: Relocation of railway line 22% 5
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.
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.
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 slightly towards the
north and the south of the protected beach to provide a unified system.
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• 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.
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 between 17
Mile Point and Greystones town. Maintenance requirements are to be informed
by regular monitoring and assessment of structural and geotechnical conditions
• 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.
7.6.2 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.
At the preliminary options assessment stage, the following options were considered:
• ‘Do nothing’
• ‘Do minimum’
• Upgrading of existing defences
• New revetment structure
• Beach nourishment
• Detached breakwater system
• Relocation of railway line
• 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.
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.
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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
Five options, in addition to the ‘do nothing’ option have been progressed to the
options assessment. These are presented graphically in Figure 39 to Figure 43.
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.
Option 2
Figure 39: Graphical representation of Option 2 for CCA6.2.
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Option 3
Figure 40: Graphical representation of Option 3 for CCA6.2.
Option 4
Figure 41: Graphical representation of Option 4 for CCA6.2.
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Option 5
Figure 42: Graphical representation of Option 5 for CCA6.2.
Option 6
Figure 43: Graphical representation of Option 6 for CCA6.2.
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7.6.2.3 MCA
A summary of the results from the MCA for CCA6.2 (South) is presented in Table
7.
The complete MCA matrix is provided in Appendix B6.
Table 7: Summary of MCA results for CCA6.2 (South).
Option Percentage
score
Ranking
Option 1: ‘Do nothing’ 51% 5
Option 2: Upgrade of revetment, extension of revetment and
proactive maintenance
55% 4
Option 3: Detached breakwater system, beach nourishment and
proactive maintenance
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
Option 6: Relocation of railway line 37% 6
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.
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.
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
The following additional measures are suggested to complement the adopted
solution and strengthen the functionality of the protection measures.
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• 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 (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.
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 between
Newcastle and Wicklow Harbour. Maintenance requirements are to be informed
by regular monitoring and assessment of structural and geotechnical conditions.
• 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.
• 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
7.8.1 Preliminary assessment
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.
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For more details on the identified risks and associated impacts, refer to WP6.
Detailed Risk Assessment.
At the preliminary options assessment stage, the following options were considered:
• ‘Do nothing’
• ‘Do minimum’
• Upgrade existing revetment
• Detached breakwater system
• Beach nourishment
• Large scale nourishment
• Groyne system
• 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.
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 measures to strengthen the functionality
of other protection measures.
7.8.2 Definition of options
Four options in addition to the ‘do nothing’ option have been progressed to the
options assessment. These are presented graphically in Figure 44 to Figure 47.
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 44: Graphical representation of Option 2 for CCA8.
Option 3
Figure 45: Graphical representation of Option 3 for CCA8.
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Option 4
Figure 46: Graphical representation of Option 4 for CCA8.
Option 5
Figure 47: Graphical representation of Option 5 for CCA8.
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7.8.3 MCA
A summary of the results from the MCA for CCA8 is presented in Table 8.
The complete MCA matrix is provided in Appendix B7.
Table 8: Summary of MCA results for CCA8.
Option Percentage
score
Ranking
Option 1: ‘Do nothing’ 63% 5
Option 2: Upgrade of existing revetment 64% 4
Option 3: Offshore breakwater system and beach nourishment 79% 1
Option 4: Groyne system and beach nourishment 76% 2
Option 5: Large scale nourishment 69% 3
7.8.4 Preferred option
Based on the MCA results the preferred option for CCA8 is:
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
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 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
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:
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• Proactive maintenance is to be provided to the existing structures in area CCA8.
Maintenance requirements are to be informed by regular monitoring and
assessment of structural and geotechnical conditions. The existing revetment
could be replaced in the future by soil embankments or other structures.
• 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 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
7.10.1 Preliminary assessment
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.
For more details on the identified risks and associated impacts, refer to WP6.
Detailed Risk Assessment.
At the preliminary options assessment stage, the following options were considered
to mitigate the coastal erosion risks identified for CCA10:
• ‘Do nothing’
• ‘Do minimum’
• Upgrade/maintenance of existing
structures
• Beach nourishment programme
• Large-scale nourishment
• Groyne system
• Detached breakwater system
• 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.
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At a local scale, beach nourishment and dune regeneration are not considered
sufficient to mitigate the existing risks as a standalone measure. However, these
solutions have been proposed as additional measures to strengthen the functionality
of other protection measures.
7.10.2 Definition of options
Four options in addition to the ‘do nothing’ option have been progressed to the
options assessment. These are presented graphically in Figure 48 to Figure 51.
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.
Option 2
Figure 48: Graphical representation of Option 2 for CCA10.
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Option 3
Figure 49: Graphical representation of Option 3 for CCA10.
Option 4
Figure 50: Graphical representation of Option 4 for CCA10.
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Option 5
Figure 51: Graphical representation of Option 5 for CCA10.
7.10.3 MCA
A summary of the results from the MCA for CCA10 is presented in Table 9
The complete MCA matrix is provided in Appendix B8.
Table 9: Summary of MCA results for CCA10.
Option Percentage
score
Ranking
Option 1: ‘Do nothing’ 63% 5
Option 2: Upgrade of existing revetment and beach nourishment 70% 4
Option 3: Offshore breakwater system and beach nourishment 70% 3
Option 4: Groyne system and beach nourishment 76% 2
Option 5: Large-scale nourishment 84% 1
7.10.4 Preferred option
Based on the MCA results the preferred option for CCA10 is:
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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
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
CCA10. Maintenance requirements are to be informed by regular monitoring
and assessment of structural and geotechnical conditions.
• A monitoring programme should be implemented in order to evaluate the
sediment transport regime and evolution of the coastal cells, in particular, the
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.
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7.11 CCA11 – Brittas Bay
7.11.1 Preliminary assessment
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.
At the preliminary options assessment stage, the following options were considered
to mitigate the coastal erosion risks identified for CCA11:
• ‘Do nothing’
• ‘Do minimum’
• Dune regeneration
• Beach nourishment programme
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.
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.
7.11.2 Definition of options
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.
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 52: Graphical representation of Option 2 for CCA11.
Option 3
Figure 53: Graphical representation of Option 3 for CCA11.
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7.11.3 MCA
A summary of the results from the MCA for CCA11 is presented in Table 10.
The complete MCA matrix is provided in Appendix B9.
Table 10: Summary of MCA results for CCA11.
Option Percentage
score
Ranking
Option 1: ‘Do nothing’ 63% 3
Option 2: Dune management (protection and planting) 74% 1
Option 3: Beach nourishment programme 64% 2
7.11.4 Preferred option
Based on the MCA results the preferred option for CCA11 is:
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.
Additional considerations
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.
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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.
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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.
Core criteria Global
weighting
Objective Individual
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
2 - 25% of transport routes at risk protected
3 - 50% of transport routes at risk protected
4 - 75% of transport routes at risk protected
5 - 100% 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
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Core criteria Global
weighting
Objective Individual
weighting
Description Objective scoring
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
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Page A3
Core criteria Global
weighting
Objective Individual
weighting
Description Objective scoring
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
2 - Coastal hazards and risks 25% addressed
3 - Coastal hazards and risks 50% addressed
4 - Coastal hazards and risks 75% addressed
5 - Coastal hazards and risks 100% 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
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Core criteria Global
weighting
Objective Individual
weighting
Description Objective scoring
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
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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.
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Page B2
B2 CCA2-3
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 2 4 4 4 4 4
20% Land use 2 4 4 4 4 4
50% Infrastructure 1 4 5 5 5 4
So
cial
15%
30% Health and safety (construction) 3 4 3 4 4 5
30% Health and safety (design life) 3 4 3 4 4 5
10% Community 2 5 5 5 5 5
15% Access 1 3 4 4 3 4
15% Social and recreation facilities 1 3 4 4 3 4
En
vir
on
men
tal
&
Her
itag
e
20%
50% Environmental Aspects (Ecology, Habitats and Birds Directives
and flora and fauna) 2 2 2 3 3 5
20% Landscape and visual 2 2 2 3 2 5
10% Cultural heritage 4 5 5 5 5 5
20% Licencing and Statutory Permits 5 4 1 2 2 2
Tec
hn
ical
20%
30% Hazard elimination 1 3 4 4 3 4
30% Constructability 5 5 1 2 2 2
20% Impact on adjacent areas 2 2 3 3 3 5
20% Sustainability and adaptability to climate change 1 2 4 4 4 4
Co
st
20% 75% Capital expenditure 5 5 3 4 4 1
25% Maintenance expenditure 5 4 3 4 4 2
Percentage score 55% 74% 65% 76% 73% 71%
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.
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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.
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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.
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Page B5
B5 CCA6.1
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 4 4 1
50% Infrastructure 1 5 4 4 1
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 4 5 4 1
15% Social and recreation facilities 1 3 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 3 5 4 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 3 1
30% Constructability 5 2 2 2 1
20% Impact on adjacent areas 1 2 5 4 1
20% Sustainability and adaptability to climate change 1 3 4 3 1
Co
st
20% 75% Capital expenditure 5 3 4 5 1
25% Maintenance expenditure 5 3 3 4 1
Percentage score 48% 71% 78% 74% 22%
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.
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Page B6
B6 CCA6.2
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 5 4 5 5 1
20% Land use 1 3 3 4 3 1
50% Infrastructure 1 2 3 4 2 5
So
cial
15%
30% Health and safety (construction) 5 2 3 3 3 1
30% Health and safety (design life) 1 2 3 3 2 3
10% Community 1 4 5 5 4 1
15% Access 1 3 5 5 4 1
15% Social and recreation facilities 1 2 5 4 3 1
En
vir
on
men
tal
&
Her
itag
e
20%
50% Environmental Aspects (Ecology, Habitats and Birds Directives
and flora and fauna) 2 2 5 4 3 1
20% Landscape and visual 2 1 4 3 2 1
10% Cultural heritage 1 4 5 5 4 1
20% Licencing and Statutory Permits 5 3 2 2 2 1
Tec
hn
ical
20%
30% Hazard elimination 1 3 3 4 3 5
30% Constructability 5 2 2 3 3 1
20% Impact on adjacent areas 2 2 4 4 3 2
20% Sustainability and adaptability to climate change 1 2 4 4 3 1
Co
st
20% 75% Capital expenditure 5 4 4 4 5 1
25% Maintenance expenditure 5 2 4 3 3 1
Percentage score 51% 55% 73% 76% 65% 37%
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.
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Page B7
B7 CCA8
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 3
20% Land use 1 4 4 4 3
50% Infrastructure 5 5 5 5 5
So
cial
15%
30% Health and safety (construction) 5 1 3 2 4
30% Health and safety (design life) 1 2 3 3 5
10% Community 1 4 5 5 4
15% Access 1 3 5 5 4
15% Social and recreation facilities 1 3 5 4 4
En
vir
on
men
tal
&
Her
itag
e
20%
50% Environmental Aspects (Ecology, Habitats and Birds Directives and flora
and fauna) 2 3 4 4 5
20% Landscape and visual 2 2 4 3 5
10% Cultural heritage 5 5 5 5 5
20% Licencing and Statutory Permits 5 1 1 1 2
Tec
hn
ical
20%
30% Hazard elimination 1 5 4 3 2
30% Constructability 5 2 2 2 4
20% Impact on adjacent areas 2 2 3 3 4
20% Sustainability and adaptability to climate change 1 2 4 4 4
Co
st
20% 75% Capital expenditure 5 3 5 5 1
25% Maintenance expenditure 5 2 3 4 2
Percentage score 63% 64% 79% 76% 69%
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.
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Page B8
B8 CCA10
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 3
20% Land use 1 4 4 4 3
50% Infrastructure 5 5 5 5 5
So
cial
15%
30% Health and safety (construction) 5 2 4 3 5
30% Health and safety (design life) 1 2 3 3 5
10% Community 1 4 5 5 4
15% Access 1 3 5 4 4
15% Social and recreation facilities 1 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) 2 3 4 4 5
20% Landscape and visual 2 2 4 3 5
10% Cultural heritage 5 5 5 5 5
20% Licencing and Statutory Permits 5 2 2 2 3
Tec
hn
ical
20%
30% Hazard elimination 1 5 4 4 3
30% Constructability 5 3 3 4 4
20% Impact on adjacent areas 2 2 4 4 4
20% Sustainability and adaptability to climate change 1 2 4 4 3
Co
st
20% 75% Capital expenditure 5 4 1 3 5
25% Maintenance expenditure 5 2 3 4 2
Percentage score 63% 70% 70% 76% 84%
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.
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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.