guidance for assessment of cumulative impacts on the historic environment … · 2018-11-08 ·...

Guidance for Assessmentof Cumulative Impacts

on the Historic Environmentfrom Offshore Renewable Energy

Oxford Archaeology withGeorge Lambrick Archaeology and Heritage

January 2008

This report has been commissioned by COWRIE Ltd

www.offshorewind.co.uk

o a

i

COWRIE CIARCH-11-2006

Guidance for Assessment ofCumulative Impacts on theHistoric Environment from

Offshore Renewable Energy

Oxford Archaeologywith

George Lambrick Archaeology and Heritage

January 2008


ii

© COWRIE Ltd, 2008Published by COWRIE Ltd.

ISBN: 978-0-9557501-0-6 (pdf)

Preferred way to cite this report:COWRIE (2008), Guidance for Assessment of Cumulative Impacts on the Historic Environment fromOffshore Renewable Energy. Commissioned by COWRIE Ltd (project reference CIARCH-11-2006).Project contractors: Oxford Archaeology with George Lambrick Archaeology and Heritage.

COWRIE CIARCH-11-2006

Copies available from:www.offshorewind.co.ukE-mail: [email protected]

Contact details:Oxford Archaeology, Janus House, Osney Mead, Oxford OX2 0ES

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iii

Executive Summary ........................................................................................................................... iv

Acknowledgements ...........................................................................................................................vi

1 Introduction .................................................................................................................................. 11.1 Offshore Renewable Energy ................................................................................................... 11.2 Marine Historic Environment................................................................................................... 11.3 SEA and EIA ............................................................................................................................ 11.4 Cumulative and Synergistic Effects ........................................................................................ 2

2 Extent of the Historic Environment ............................................................................................ 32.1 Development Impact and the Historic Environment ............................................................... 32.2 Responsibility for Assessment ............................................................................................... 3

3 Cumulative and Synergistic Effects ........................................................................................... 53.1 What are Cumulative and Synergistic Effects? ...................................................................... 5

3.1.1 Principal sources of impact from renewable energy schemes .................................... 53.1.2 Sources of cumulative impacts relative to other types of development ...................... 5

4 Guidance on Assessment ........................................................................................................... 74.1 General Considerations .......................................................................................................... 7

4.1.1 Structure of assessment............................................................................................... 74.2 Scoping and Baseline Studies ................................................................................................ 7

4.2.1 Geographical boundaries for assessing cumulative effects ......................................... 74.2.2 Sources of data ............................................................................................................ 8

4.3 Impact Analysis and the Significance of Effects .................................................................... 94.3.1 General principles ......................................................................................................... 94.3.2 Methodological approaches to assessing synergistic and cumulative effects .......... 104.3.3 Concepts and criteria for establishing the value of historic features and areas

and the scale of impacts affecting them .................................................................... 114.3.4 Assessing levels of impact and significance of synergistic and

cumulative effects....................................................................................................... 124.4 Mitigation .............................................................................................................................. 12

4.4.1 General principles of mitigation .................................................................................. 124.5 Reporting .............................................................................................................................. 13

4.5.1 Content ....................................................................................................................... 134.5.2 Reporting – co-ordination ........................................................................................... 13

4.6 Implementation and Monitoring and Review ........................................................................ 144.6.1 Requirement and responsibility .................................................................................. 144.6.2 Monitoring practicalities ............................................................................................. 14

References and Bibliography .......................................................................................................... 15

Appendix A. Guidance on Cumulative Impacts ............................................................................. 17Appendix B. Extent of the Historic environment Susecptible to Impact .................................... 18Appendix C. Comparison of Methods for Cumulative Impact Assessment ............................... 19

List of Tables and FiguresTable 1. Summary of the historic environment and potential impacts ............................................... 4Figure 1. Stages of cumulative impact assessment ............................................................................ 7Figure 2. Distinguishing change and outcome ................................................................................... 10

Contents

iv

Executive Summary

The development of offshore renewable energyto generate electricity is one of the key strategiesbeing used by the UK Government to addressthe twin concerns of climate change and theneed to secure energy supplies for the future.Implementation of the programme is underwayfor offshore wind farms and wave energy.

Oxford Archaeology, supported by GeorgeLambrick Archaeology and HeritageConsultancy, was commissioned by COWRIELtd to produce guidance on the assessment ofcumulative impacts on the historic environmentarising from offshore renewable energy projects.

The guidance applies to all areas which arelikely to be affected by an offshore energydevelopment, thus covering onshore as well asthe coastal and marine environments. Themarine environment affected by offshore energyschemes comprises UK territorial waters andthe Renewable Energy Zones, which have beenidentified beyond that limit.

The guidance is intended to assist developers ofoffshore renewable energy installations,environmental consultants from all disciplines,historic environment contractors, industryregulators and other authorities, includinghistoric environment curators at national andlocal level, and the public.

SEA and EIA

The assessment of the potential impacts ofoffshore renewable energy developments iscarried out through processes directed by theEU Directives for Strategic EnvironmentalAssessment (SEA) and Environmental ImpactAssessment (EIA). Both instances require,respectively, that the effects of developmentplans, programmes and projects on thearchaeological and architectural heritage,landscape and other aspects of the environmentare identified in advance. A component of thisassessment is the identification of steps toprevent, minimise or compensate for anyidentifiable detrimental impacts. It is a legalrequirement that this must include assessmentof cumulative and synergistic effects, and thisguidance will play a key role in this.

Cumulative and synergistic effects

A distinction can be made between 'cumulative'and 'synergistic' effects:• Cumulative effects result from incremental

changes caused by multiple impacts within adevelopment plan, programme or project,and/or the effect of impacts in combinationwith other past, current and reasonablyforeseeable developments, activities ornatural processes.

• Synergistic effects (or impact interactions)arise from the combined result of differentkinds of impact, either occurring within aproposed development plan, programme orproject, or in combination with others.

The guidance identifies issues relating to theassessment of cumulative and synergisticeffects at each stage of the SEA/EIA processfrom screening and scoping to decision-makingand implementation. Appropriate assessment ofcumulative effects relies heavily on how wellindividual effects within the development plan,programme or project are identified andassessed, and on how they relate to the effectsof other developments and activities.

Quality Assurance andKey Guidance

SEA and EIA fundamentally influence majordecisions on future developments which willhave a permanent effect on the environment.There is a particular challenge to ensure thatcumulative piecemeal loss of irreplaceablehistoric environment assets and complexrelationships with other aspects of theenvironment are properly assessed toencompass adequately the historic environmentin how change through development isdelivered. This guidance should help to ensurethat the legal requirement to assess cumulativeand synergistic effects are met, that decision-makers are assisted in reviewing theserequirements, and that appropriate, practicableand realisable measures to protect the historicenvironment are adopted. The guidance focuseson certain key elements of the cumulativeassessment process, which are always relevant.These are as summarised below.

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Integrated Approach• Exchange of information between

Environmental Assessment (EA) co-ordinators and specialists at all stages ofthe process.

• Consideration of potential cumulativeeffects at all stages of the process.

• Commission of joint surveys wherepracticable.

Consideration of Other Actions• Identify all sources of potential cumulative

effects within the particular project, planor programme.

• Identify past, present and future actionswhich may contribute (or be contributing)to cumulative effects.

Adequate Scope• Definition of a sufficiently wide study area,

not necessarily the same for all aspects ofthe environment.

• Definition of a suitable time scale forfuture developments.

• Selection of other activities which maycontribute to cumulative effects.

Baseline Study• Ensure that the offshore, intertidal and

terrestrial historic environments are allconsidered.

• Identify the significance of historicenvironment features.

• Identify levels of risk for unknown historicenvironment features.

• State criteria used in assessment.

Impact Dimensions• Identification of direct, indirect and

secondary effects and their time scales.• Identification of beneficial and adverse

effects.• Identification of internal cumulative and

synergistic effects.

• Identification of external cumulative andsynergistic effects.

• Distinction between cumulative effects onphysical fabric and setting/perceptualvalues.

Assessment Focus• Focus on assessment of significant

potential cumulative effects.• Ensure that the coverage is sufficient to

identify all potential cumulative effects.

Explicit Constraints• Identify clearly any assumptions which

have been made and any limitations onthe extent of the assessment.

Mitigation Measures• Selection of realistic mitigation measures.• Identification of residual effects after

mitigation.• Provision for unforeseen effects.• Agreement to implement mitigation.

Monitoring and Management• Establishment of a monitoring programme

for significant cumulative effects as part ofthe overall monitoring of the plan.

• Use of monitoring results to inform theaccuracy of impact prediction and helpimprove future plan making.

• Documentation of agreed actions,including responsibility for theirimplementation.

Communication• Summaries of significant potential

cumulative effects.• Cross-references to material from other

environmental specialisms.• Explicit basis for conclusions.• Adequate coverage in non-technical

summary.

vi

Acknowledgements

This report was commissioned by COWRIE Ltd.Oxford Archaeology would like to thank theCOWRIE Secretariat at NatureBureauInternational for their assistance during theproject.

Oxford Archaeology would like to thank theCOWRIE Steering Group for their assistance,support and advice during the compilation ofthis document, particularly Dr Chris Pater ofEnglish Heritage and his colleagues. They wouldalso like to thank all those from heritage

organisations and the renewable energyindustry who provided comments on the draftreport and attended the seminar in Oxford inSeptember 2007.

This report was compiled by Jill Hind and KellyPowell of Oxford Archaeology in conjunctionwith George Lambrick of George LambrickArchaeology and Heritage. The project wasmanaged on behalf of Oxford Archaeology byIanto Wain.

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1.1 Offshore Renewable Energy

The United Kingdom has stated its commitmentto the reduction in emission of the greenhousegases, which are one of the causes of theongoing climate change. One of the strategiesby which this will be achieved is the increasinguse of renewable energy sources, includingthose available offshore, to provide electricity.The Government has set ambitious targets,committing the UK to generating 10% of itsenergy needs from renewable sources by 2010,rising to 60% by 2050.

Wind, wave and tidal power are all to form partof the UK renewable energy strategy. Offshorerenewable energy plant construction has thepotential to have significant impacts on manyaspects of the environment, including thehistoric environment. These include cumulativeand synergistic impacts and this documentaddresses them specifically with respect to thehistoric environment, as part of a range ofguidance documents commissioned byCOWRIE. It is aimed at all those involved in theenvironmental assessment process, regulatorybodies, developers and specialist consultants.No offshore project can be considered tooperate solely within the marine environment,and for renewable energy there are implicationsnot only for the seabed, where the generatorsare located, but also for the foreshore throughwhich the electricity cables must pass and theland on which associated infrastructure will belocated.

Within UK territorial waters most of the UKseabed is owned and licensed by the CrownEstate. Outside this limit, within the UK’sdesignated Renewable Energy Zone (REZ) ofinternational waters, the right to issue leases isstill held by The Crown Estate. REZs wereestablished by the Energy Act (2004).

1.2 Marine Historic Environment

The sea, seabed and foreshore of northernEurope including the British Isles have beenexploited by humans for over half a millionyears. Lands extending across the continentalshelf were occupied periodically by ancientpeoples before rising waters repeatedly

inundated the landscape. Watercraft fromprehistory to the present day enabled travelacross the evolving seas but many were lost enroute that now survive as wrecks.

Britain is a maritime nation that has aninternationally rich heritage of seafaring tradeand coastal defence. In addition to visiblebuildings, monuments and landscapes,submerged and buried land surfaces,settlements, boats, ships and aircraft, andremains of harbours, quays, fortifications andother archaeological remains contribute to thevalue of this heritage as part of the UK’snational identity. They not only contribute topeople’s cultural understanding and sense ofplace, but can also have a role in tourism andeducation. Once destroyed, these importantphysical remains of Britain’s history are lostforever and there is a responsibility to avoidunnecessary damage and record unavoidableloss for the benefit of present and futuregenerations. Environmental Assessment (EA)procedures are intended to balance the needsof development with the need to avoidunnecessary or unsustainable environmentaldamage, including the historic environment.

1.3 SEA and EIA

Offshore renewable energy projects must becovered by wide scale Strategic EnvironmentalAssessment (SEA), required under EuropeanDirective 2001/42/EC: The assessment of theeffects of certain plans and programmes on theenvironment, to analyse the environmentalimplications of development ‘plans’ and‘programmes’ needed to implementGovernment policy such as deriving energyfrom offshore installations. The two levels ofassessment – strategic and project-based –should be used together for the most effectiveprotection of the environment.

The nature and magnitude of offshorerenewable energy projects means that they arerequired to undergo SEA and also EIAs asrequired by the European Union Directive 85/337/EC: The assessment of the effects of certainpublic and private projects on the environmentand Directive 97/11/EC: Amendments toDirective 85/337/EC. SEAs covering offshore

1 Introduction

2

Guidance for Assessment of Cumulative Impacts on the Historic Environment from Offshore Renewable Energy

renewable energy may be focused on theindustry in general or within a particular marinearea in which projects will be located. Both SEAand EIA require that any potential impacts onthe environment are identified and proposals toeliminate, reduce or compensate for theseimpacts are drawn up.

Studies of existing SEA and EIA documents, forexample the Planarch 2 report (Lambrick andHind 2005), have found that the coverage ofcumulative impacts is an area of weakness andthat the historic environment seldom features intheir discussion. The preparation of this specificguidance is intended to help overcome difficultieswith this important area of environmentalassessment and improve the quality ofrecommendations and their implementation.

1.4 Cumulative andsynergistic effects

Documents, including EU Guidance (EuropeanCommission (1999), often make a distinctionbetween cumulative effects which areessentially additive and synergistic effects orimpact interactions. The term in-combinationeffects is also used.

Impact interactions or Synergistic Effectsarise from the reaction between impacts ofa development plan, programme or projecton different aspects of the environment.

Aggregate or Cumulative Effects are thosethat result from incremental changes causedby other past, present or reasonablyforeseeable actions together with the plan,programme or project itself.

The principal guidance documents available inrelation to cumulative effects are listed inAppendix A.

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2 Extent of the Historic Environment

2.1 Development Impact and theHistoric Environment

Individual historic assets and areas areimportant to society as tangible, non-renewableparts of people’s history. The most obviousimpacts of development on the historicenvironment are physical changes to the fabricof features or to their setting. Such impacts canaffect people’s perception of the heritage interms of the understanding and appreciation ofthe asset and the contribution they can make toknowledge of the historic environment.

The impacts on setting and perceptual value ofhistoric assets go beyond the effects of visualor noise impacts. Historical associations andcontext are important, including a sense ofplace, as described in A Force for Our Future(DCMS 2001, 7), but aesthetic and spiritualvalues extend beyond the past. Connectionswith works of art are one example of this.

‘Fabric’ is the extant physical character ofan asset or the features that give an area itshistoric character.

‘Setting’ can be defined as the physicalsurroundings of an historic feature or areainfluencing how it is understood andappreciated.

‘Perception’ is the different ways peoplevalue historic features and their setting.

Perceptual value and the historic environmentare discussed in more detail in Appendix B.

2.2 Responsibility for Assessment

In both SEA and EIA, specialist studies arecarried out to identify potential impacts on thephysical fabric of the historic environment, but itis common for much of the consideration ofsetting/perceptual issues to be covered in otherstudies. They are, however, an important aspectof the historic environment and should receivespecialist consideration.

Responsibility for the assessment of theinteractions between effects from the variousaspects of the project and those arisingdifferent projects and activities should beshared among all environmental specialists,although the lead co-ordinator or developer hasoverall responsibility for the final assessment.They should ensure that the necessaryexchange of information take place and monitorto avoid double counting of impacts.

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Table 1. S

umm

ary of the histo

ric environm

ent, po

tential sources o

f imp

act of p

lans and p

rojects and

their effects.

OffshoreIntertidal

TerrestrialPotential sources of im

pactEffects on the heritage

Shipwrecks/

•Protected w

reck sites•

Wrecks and hulks

•Buried w

recks and aircraft•

Construction/maintenance and

• Direct damage/destruction

aircraft•

Known, unprotected

decomm

issioning of features• Severance of associated features

•Loss sites

•Construction and m

onitoring traffic•

Destabilisation, decay and corrosion•

Unknown

•Intrusive site prospection

•Long-term

preservation of archaeology•

Artefacts and scatters•

Changes to scour patterns• Loss of or intrusion on setting

•Vibration

•Accidents

•Changes to environm

ental conditions•

Appearance of development

Submerged

•In situ settlem

ent•

In situ settlement

•In situ settlem

ent•

Construction/maintenance and

•Direct dam

age/destructionlandscapes

•Palaeoenvironm

ental•

Finds scatters, including•

Palaeoenvironmental

decomm

issioning of features• Severance of associated features

andfeatures

those eroded from cliffs

deposits•

Construction and monitoring traffic

•Destabilisation, decay and corrosion

below-ground

•Artefacts and scatters

•Palaeoenvironm

ental•

Artefacts•

Intrusive site prospection•

Compression

remains

evidence•

Changes to scour patterns•

Vibration•

Changes to environmental conditions

Standing•

Seaforts, army tow

ers• Lighthouses

•Standing buildings and

•Construction/m

aintenance•

Direct damage/destruction

structures•

Lighthouses•

Docksm

onuments e.g. those

and decomm

issioning of features• Loss or severance of associated features

and•

Lightships and other•

Flood and coastal defencefor navigation or defence

•Construction and m

onitoring traffic• Loss of or intrusion on setting

monum

entsm

oored structures•

Industrial sites incl. fishing•

Landscape features•

Intrusive site prospection•

Alterations to views and public

•Jetties, m

oles, piers etc.•

Historic areas and places•

Temporary structures

appreciation•

Vibration•


•Restrictions on intervisibility

Historic•

Historic seascape•

Historic landscape•

Cultural and historic•


•Changes to character (including

character andcharacter

and seascape characterassociations

•Physical changes to area (especially

enhancement)

perceptual•



Historic landscape andhistoric features)

•Severance or fragm

entation of historicvalue

associationsassociations

seascape character•

Changes of userelationships

•Features used for



•Altered usage patterns, particularly

•Loss of legibility of historic character

navigationnavigation

navigationleisure/tourism

• Changes arising from econom

ic•

Changes in planning statusrepercussions through tourism

/regeneration

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3 Cumulative and Synergistic Effects

3.1 What are cumulative andsynergistic effects?

Effects arising from one particular project canbe classed as ‘internal’, while those arising fromother projects and activities are ‘external’. Aswith individual effects, synergistic andcumulative ones may be beneficial as well asadverse, may be permanent or temporary andcan be indirect. They can take a wide range offorms.

3.1.1 Principal sources of impact fromrenewable energy schemesIt is possible that a single offshore energyinstallation will itself result in cumulative impactson the historic environment over its variousphases, arising from the impacts and effects

identified in Table 1. Installations also tend to beclustered in a limited number of areas. Theseimpacts may be temporary or permanent. Thetimetable for the different stages of the variousprojects will also be significant as levels ofimpact will depend on whether the stages runconcurrently and whether development work willbe continuous or broken up by periods ofinactivity.

3.1.2 Sources of cumulative impactsrelative to other types of developmentConstruction of an offshore renewable energyfacility may well not be the first or onlydevelopment to have had an impact on thehistoric environment of its specific location andthe surrounding area, and this needs to beunderstood properly.

Examples of synergistic effects or impact interactions• The effect of the same impact affecting different physical aspects of the environment as

reflected in EA specialist topics – examples: the cumulative effect of disturbing both habitatsand species and archaeological remains.

• The cumulative effect of the same impact affecting different perceptual values of theenvironment – example: changes to legibility of historic character added to visual impactchanging the significance of a feature.

Examples of ‘internal’ cumulative effects• The submerged landscapes and wrecks affected by turbine foundations for a windfarm.• The cumulative significance of numerous individual effects of different types in the same area

– example: the cumulative effect of multiple minor disturbances related to foundations, cablelaying, scour etc.

• The cumulative effect of multiple impacts on different environmental resources in the samearea – example: damage to foreshore features, construction of sub-station and visual impacts,all impairing the survival of historic assets and altering the historic character of the area.

Examples of ‘External’ cumulative effects: in-combination spatial, chronological orsectoral effects• The cumulative effect of recurrent physical or perceptual impacts of new developments

diminishing the historic environment of an area over time – example: visual intrusion on thesetting of an important historic site from several offshore energy installations.

• The cumulative effect for the historic environment of several developments in an area affectingmultiple heritage assets – example: several renewable energy developments intruding on thesetting of several monuments and buildings connected with seafaring and defence.

• The positive cumulative effect of archaeological information generated by survey and othermitigation measures – example: the positive benefits of gradual build up of knowledge ofpreviously unidentified submerged landscapes offshore.

• The indirect cumulative effect of past current and future activities on the survival of historicenvironment assets – example: renewable energy development causing minimal directdisturbance but excluding other activities, such as fishing causing bottom scour.

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It is important that natural processes as well ashuman activities are considered since this maywell determine the ‘do-nothing’ scenario, i.e. thechanges to the historic environment which arelikely to occur without any development takingplace. The effects of development may wellchange the natural dynamics of the marineenvironment in particular, with knock-on effectsfor the survival of the historic environmentfeatures and deposits.

For the assessment of cumulativeimpacts it is necessary to identify:• what developments have significantly

affected the area’s historic environment inthe past;

• what ongoing activities or natural processesare affecting its condition and survival; and

• what other developments are proposed inthe short- to medium-term future that arelikely to contribute to significant effects onthe historic environment.

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4 Guidance on Assessment

4.1 General considerations

4.1.1 Structure of assessment

Two general issues need to be considered indeveloping a well-structured approach toassessing cumulative effects of development.

First, a logical approach is needed to establishhow the assessment of synergistic andcumulative effects will be ‘modelled’ fromindividual ones. There is no single best way todo this, since there are different ways in whichindividual impacts can be grouped which maybe more appropriate for one case than another.Figure 1 below indicates one possibleapproach.

4.2 Scoping and Baseline Studies

4.2.1 Geographical boundaries forassessing cumulative effects

Establishing what geographical boundariesshould be set for the assessment of cumulativeeffects is an important issue that needs to beconsidered on a case-by-case basis.

The geographical areas over which cumulativeeffects on the fabric of historic environmentfeatures may occur will very often be differentfrom the areas over which effects on perceptualvalues could occur. These may also be differentfrom other environmental topics. There is thusno single one-size-fits-all solution to defining thearea needing to be taken into account to assesscumulative effects.

Figure 1. Stages of cumulative impact assessment.

Possible Structure of Assessment

Individual Effects/ Risks on thePhysical Fabric of Heritage

Individual Effects on Setting andPerceptual Value of Assets

Grouping of Internal Cumulative andSynergistic Effects on the

Physical Fabric of Heritage

Grouping of Internal Cumulative andSynergistic Effects on Setting and

Perceptual Values of Heritage

Add External Data

Assessment of Internal and ExternalCumulative/ Synergistic Effects on the

Physical Fabric of Heritage

Assessment of Internal and ExternalCumulative/ Synergistic Effects on Setting

and Perceptual Values of Heritage

Overall Cumulative Effects (both general and particular assets)

Project-specific Cumulative Effects (general and particular assets)

Listing of Individual Effects

!

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The nature of offshore developments also raisesthe possibility of transboundary impacts if thecumulative effects will be experienced outsideUK territorial waters Renewable Energy Zones(REZ), especially those that are cumulative withdevelopments under other jurisdictions, andappropriate information gathered.

How the extent of potential cumulativeeffects might influence a study area

• A single offshore development mightrequire only the footprint plus a buffer(perhaps c 2 km) and a 500 m cablecorridor.

• The possible cumulative extent of scourindirectly triggered by a number ofoffshore energy or other structures, whichmay extend over several km, as shown byrecent work undertaken by SouthamptonUniversity, The National OceanographicCentre and English Heritage (http://www.noc.soton.ac.uk/soes/research/groups/geophysics/aggregates/Index.htm).

• A sequence of wrecks of different periodsaffected by the same treacherousnavigation hazards in a particular area.

• Visual envelopes have only very limitedrelevance to the setting and character ofmost of the submerged and buried marinehistoric environment whose perception isbased on cognitive rather than visualunderstanding.

• Effects arising close to the boundary ofUK waters that might have cumulativeeffects with developments of adjacentStates, triggering the need to considertransboundary effects.

4.2.2 Sources of data

The range and sources of baseline data andsurveys required to assess the individualimpacts of a plan, programme or project areoutlined in Historic Environment Guidance forthe Offshore Renewable Energy Sector(COWRIE 2007). However, the baselinecharacterisation should be independent of thedevelopment proposal. Assessing synergisticand cumulative effects involve additionalsources of data.

Sources of data needed to assesssynergistic and cumulative effects• Assessment of internal synergistic and

cumulative effects will be reliant on theidentification of individual impacts acrossa range of environmental topics.

• Assessment of external synergistic andcumulative effects will usually requireadditional data related to otherdevelopments, socio-economic activityand natural processes.

• It will often be cost effective to gatherdata about external activities at the sametime as the basic historic environmentdata needed for assessment of theindividual effects.

A proper consideration of impact interactionsand synergistic effects requires liaison betweenspecialists. For synergistic effects arising incombination with other developments or trends,other SEAs and EIAs will need to be consideredin relation to the significance of such effects. Itis not practical to identify all developments andactivities which have ever had some impact ona particular area or may theoretically do so inthe future: baseline studies should focus on themost significant changes and especially on anysources of ongoing impacts.

It is important to establish the significance of theremaining potential or value of the resource asthe baseline of past impacts, so that theimplications of further impacts can be assessedin terms of capacity for further change.

How potential synergistic effects caninfluence compilation of baseline data• Visual and landscape specialists need to

be informed of heritage features and areasfor which an assessment of visual intrusionis needed in relation to issues of setting.

• The co-occurrence of importantgeomorphological features and wildlifehabitats and historic features such assubmerged land surfaces and wrecksshould be established.

• The contribution of important historiclandscape, townscape and seascapecharacter to overall landscape andseascape character.

• For consideration of ‘internal’ cumulativeeffects, data relating to survival, condition

9

and potential this will often come fromstandard sources consulted through deskstudies supplemented by results of fieldand marine survey.

• For ‘external’ cumulative effectsinformation on past change will begathered through the studies needed toestablish the wider background to thestudy area, and from other SEAs and EIAs.Additional comments may be sought fromstatutory and other consultees.

The principal sources of information for otherdevelopments would be a SEA or EIA, ifavailable. Although the information availablemay not allow detailed assessment, even ascoping report or consultation with the relevantauthority may at least allow the potential forsignificant cumulative effects to be identified.

Example of sources of data examined toassess cumulative effects of a windfarmFor the Cirrus Shell Flat Array offshorewindfarm in Liverpool Bay a wide range ofother types of project were considered, andthe availability of data for each project wastabulated, grouped by development sectoraccording to whether an EnvironmentalStatement was available and if so whether inhard copy or digitally, and whether otherdata sources were available. The overallpattern of availability of data is given belowsummarising the table in the EnvironmentalStatement (ES).

Sector Paper Digital Other ES(no projects) ES ES data unavailable

Windfarms (9) 3 7

Oil and Gas (14) 4 8 2

Aggregates (4) 2 2

Waste (12) 12

Other projects (6) 2 3 1

4.3 Impact Analysis and theSignificance of Effects

4.3.1 General principles

The core aim of environmental assessment is toidentify significant effects on different aspectsof the environment and its value to people, by

weighing the value of the historic assetsaffected against the scale of the impact. Varioustechniques for this are explained in HistoricEnvironment Guidance for the OffshoreRenewable Energy Sector (COWRIE/WessexArchaeology 2007).

It is important to recognise that the presence,extent, condition and character ofarchaeological remains is often poorlyunderstood, and potential impacts on them maybest be identified in terms of levels of risk.

Basis of judging Significant Effects• The combination of the importance of the

resource PLUS the level of impact.• A judgement of RISK can be made where

POTENTIAL importance or level of impact isuncertain.

• A confidence rating for the significance ofeffects can be valuable.

Importance/potential criteria and issues toconsider• Designations.• Professional and policy standards.• Local values.

Issues for assessing levels of impact• Understanding both the known and potential

resource.• State of preservation.• Physical and visible character of development.• Effects of how development is carried out as

well as final product.• Effects on how people appreciate and

understand the history of their surroundings.• Judgement of other relevant specialists (e.g.

visual).

This approach can be scaled up from individualimpacts to consider the significance ofsynergistic and cumulative effects, butjudgements get more complicated as morefactors come into play from consideration ofinteractions with other environmental topics andthe overall cumulative effect of impacts ofvarying types (direct/indirect, adverse/beneficial, permanent/temporary) areconsidered together.

Most EAs judge significance of effect as changefrom present conditions. As a result, past

Guidance on Assessment

10


impacts are usually regarded as havingdegraded the resource, and impacts are thusjudged less significant than if it were betterpreserved. But this approach is not well suitedto assessing cumulative effects, where theoverall outcome rather than the level of changeis what matters, as shown in Figure 2.

For assessing the degree of change the existingposition is treated as a neutral starting point.For measuring the outcome of cumulativeeffects of a development in conjunction withothers the starting point needs to be anassessment of current condition (good or bad)which depends on how past activities haveeffected the resource; from this the overalloutcome of further change can be judged.

There is no set method which should be usedfor assessing cumulative effects, but thesignificance of a change and what represents anacceptable level of change needs to beconsidered.

Key questions to address in assessingthe significance of cumulative effects

Past change may have devalued an assetbut is the remaining value still significantand critically endangered?• What key characteristics and potential will

survive?• Will they be stable or unstable?• Is the accumulated loss still within

acceptable limits of change?

Figure 2. Distinguishing change and outcome.

How significant are the effects of thedevelopment when consideredcumulatively?• Is the overall significance of multiple

impacts greater or less than the ‘sum ofthe parts’?

Can mitigation measures reduce thesignificance of adverse cumulative effects toan acceptable level?• Assessing the overall residual significance

of cumulative effects should take intoaccount agreed proposals to avoid ormitigate impacts.

4.3.2 Methodological approaches toassessing synergistic and cumulativeeffects

A variety of methods have been developed forassessing cumulative and synergistic effectsand these are compared in Appendix C.

A broad approach to methods ofassessing synergistic and cumulativeeffects

Expert Judgement is vital• Specialist EA consultants and engineers

(Historic Environment specialists liasingwith others).

• Regulators’ advice is especially importantin relation to external cumulative effects.

• Judgements need to be systematic andbased on accepted standards.

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Spatial analysis is fundamental to assessingimpacts• Must include spatial information about

developments as well as the historicenvironment.

• Can locate past and foreseeable impactsof other projects and trends relative toproject and identify overlapping areas ofimpact (especially visual).

Matrices help collate and summarisecomplex judgements (see Appendices Gand H for examples)• Can systematise judgements without

risking over-simplification of scoring.• Can be ‘nested’ to allow summaries of

detail to be fed into more strategic levelsof analysis and assessment.

To support these• Checklists help to ensure issues are

considered (may be basis of matrices).• Network analysis or flow diagrams are

potentially very useful for identifyingcomplex effects.

• Predictive modelling is potentiallyimportant but relies on robust data andmethods.

• Assessment of carrying capacity/ limits ofacceptable change is desirable butmethods are not well developed for thehistoric environment.

4.3.3 Concepts and criteria forestablishing the value of historicfeatures and areas and the scale ofimpacts affecting them

FabricA selection of criteria for assessing the value ofhistoric features in terms of their physical fabrichas been developed.

Typical criteria and other considerationsfor judging the value and potential ofhistoric environment features and areas• Statutory criteria e.g. Scheduled

Monument criteria.• Research issues.• Professional and policy standards.• Understanding likelihood of undiscovered

elements.• Understanding of archaeological and

historical context.

SettingFor setting, there are no agreed criteria, but anumber of factors need to be considered. Theyare more wide ranging than purely visual ones.

Factors influencing the character ofsetting• The character of the feature/area itself.• Views of the feature/area.• Topography and other natural conditions.• Views from the feature/area.• Nearby vegetation and habitats.• Visual ambience and approaches.• Nearby buildings and structures.• Noise environment and other activity.• Archaeological context.• Cultural/historical associations.

PerceptualPerceptual values mainly relate to how historicfabric and setting are understood andappreciated through a variety of ways in whichpeople interact with the historic environment. Insome respects these become more importantas a general consideration in relation tocumulative effects than for individual ones.

Examples of perceptual values attachedto historic features and areas• Intellectual understanding – through

archaeological, historical, architectural orgeographical investigation.

• Appreciation through the human senses –especially visual, also noise.

• Knowledge of history and context – whythe asset is where it is.

• Historical association – battle site or otherevent.

• Aesthetic – artistic and cinematicassociations.

• Sense of place – such as the ‘White Cliffsof Dover’, literary links, tradition and localmyths.

• Economic – the historic environment canbe important for tourism, regeneration etc.

• Educational – the historic environmentoffers important opportunities for learning.

Key attributesIn considering these values it is often helpful tofocus on some of the key attributes of thehistoric features and places involved.


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Examples of considerations defining keyattributes of heritage assets and areas• Features with an intrinsic visual function –

e.g. a lighthouse or beacon.• Designed visual relationships and

approaches to a historical place – e.g. theopen views of the horizon from a coastalfort or battery; a designed vista from anhistoric park over open sea.

• How features were used historically – e.g.relationships between quay, customsoffice and warehouses in a port.

• Attached historical attributes – e.g. theuse of buildings and monuments asnavigation marks.

• Historical events – e.g. the area of a navalbattle relative to the wrecks of lost ships;or a trail of jetsam relative to currents andthe topography of a reef or sand bankwhere a vessel foundered.

• Historical or cultural association – e.g.views depicted in well-known art ordescriptions in literature.

In relation to cumulative effects ‘HistoricSeascape Character’ can encapsulate many ofthese values at a broader level, and can be veryrelevant to the assessment of cumulative effectson the historic environment.

4.3.4 Assessing Levels of Impact andSignificance of Synergistic andCumulative Effects

Scale of ImpactsThe overall range and nature of potential sourcesof impacts on the physical fabric of historicenvironment assets are summarised below.

Examples of different kinds of physicalalteration to historic environment assets• Partial or total loss of fabric through direct

impacts or indirect impacts such as scour.• Compression, decay, distortion or other

damage.• Loss of integrity of sites and areas

through physical severance, fragmentationor isolation from surroundings.

• Indirect benefits of reducing ongoingdamage through mitigation of othereffects such as prevention of scour orincreased deposition of sediment.

Physical changes to either fabric or setting canalter an asset’s contribution to knowledge andwider appreciation.

In relation to issues of setting, effects aresynergistic in terms of interaction with visualassessment, tourism etc. Several developmentsin one area may add significantly to the overalleffect on the setting of a particular feature ormonument, but this needs to be considered interms of historic values.

The cumulative effects on different aspects ofsetting and perceptual values of the historicenvironment can be grouped in broader terms.

Historic Landscape Characterisation/HistoricSeascape Characterisation takes as its focusthe concept of ‘time-depth’ in the presentlandscape/seascape. It defines areas whosedominant character is a reflection of the sharedhistoric processes which have shaped them.Those expressions of shared character are oftenrepeated in other areas which have been shapedby similar processes, allowing the definition ofCharacter Types and to map, using GIS, theirexpressions across any given locale, sub region,region adopting the most appropriate scale. Thedefinition of Character Types (and Sub-Types) isbased on an assessment of a range of attributesderived from a diversity of data sources. It is anessentially neutral database, designed to informassessments, rather than to dictate which aremore important/significant that others.Consequently as Historic LandscapeCharacterisation/Historic SeascapeCharacterisation has comprehensive coverage, itaccepts change will happen, but provides ameans of enabling historic environment input tothat process.

4.4 Mitigation

4.4.1 General principles of mitigation

Avoiding and reducing significant effects is mainlyachieved through planning of the location ofdevelopment and good design to minimise impacts.

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The preamble of the 1985 EIA Directivepromotes two principles that areespecially pertinent to issues ofcumulative effects on the non-renewable historic environment:• “preventing nuisances at source rather

than subsequently trying to counteracttheir effects”.

• “the need to take effects on theenvironment into account at the earliestpossible stage in all the technical planningand decision-making process”.

Mitigation measures will deal with the remainingeffects that cannot be avoided. With respect tocumulative effects, it is especially pertinent thatimpacts should be minimised to avoid seriouspiecemeal degradation. It is, however, notalways possible to mitigate for a particularimpact e.g. the provision of lights to ensuresafety of navigation at night.

The SEA process is especially important foravoiding detrimental effects at a strategic level,and should establish a framework for addressingthe cumulative effects of individual developments.It is also important that developers do provide acommitment to the mitigation process.

Proposals for mitigation should also include thebasis for monitoring effects and theimplementation of environmental managementmeasures to ensure that unforeseen effects aredealt with and the effectiveness of mitigationmeasures can be judged for future reference.This is particularly pertinent in the offshore areawhere the presence of archaeology can beunpredictable at best. Mitigation is themechanism for dealing with cumulative effectsin two main areas: loss of or damage to physicalfabric, and degradation of perceptual value.Siting of offshore developments is of particularrelevance to preventing and avoiding cumulativeeffects on setting and perceptual values.

The final assessment of whether renewableoffshore energy will have a significant effect onthe historic environment should take account ofmitigation measures that have been formallyagreed. An example of an assessment ofpossible cumulative effects on the historicenvironment and their residual significance aftermitigation, was carried out for the Scottish

Offshore Energy SEA (http://www.seaenergyscotland.co.uk/).

In order to assist in effective mitigation andmonitoring COWRIE is establishing a centralrecord of survey data, accessible through adatabase.

4.5 Reporting

4.5.1 Content

It is a requirement that significant cumulativeand synergistic effects be included in a SEAEnvironmental Report or an EIA EnvironmentalStatement. Detailed analysis may be provided inthe specialist report or background information.It is important that the rationale for how theseeffects are reported is clear.

Considerations for how cumulative andsynergistic effects are reported in anEnvironmental Report or Statement• Ensure the factors considered and basis

of judgement and grading of significanceare clear.

• The kinds of effect requiring assessmentshould be explained clearly.

• Results should be summarised inspecialist reports in ways that facilitatebeing compared with the assessments ofother environmental issues.

• The text explaining cumulative effects maybe derived from statements included inmatrices or other analyses, but will bemost useful as a simple account of what issignificant.

• It may be appropriate to illustrate thespatial occurrence of cumulative effectsfrom GIS analysis.

4.5.2 Reporting – co-ordination

Ensuring proper coverage of synergistic andcumulative effects is a challenge for theassessment team, and especially the EA co-ordinator.

Important points for co-ordinating coverageof synergistic and cumulative effects• EA co-ordinators and specialists need to

liase closely.


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• In pulling results of different specialiststogether it is important to identifyinteractions and avoid double counting.

• Material relating to different specialismsshould be cross-referenced in the text.

• The structure of how cumulative effects arepresented needs careful consideration.

• The non-technical summary must faithfullyreflect specialist assessment.

• Regulators need to check that all otherrelevant developments and otherenvironmental changes have been takeninto account.

4.6 Implementation monitoringand review

4.6.1 Requirement and responsibility

Monitoring is a requirement for SEAs, andshould involve formal auditing and review ofoutcomes. This logically indicates that projectscovered by EIAs under the framework of a planor programme subject to SEA should bemonitored.

This especially applies to cumulative effects,and monitoring should seek to ensure thatmedium long-term implementation of plans andprogrammes can be adjusted to deal withproblems that arise. For example mitigationstrategies in project EIAs may need to bealtered if significant effects are not beingadequately addressed.

Monitoring involves defined tasks and otherstakeholders with common areas of interest.The evaluation of monitoring data and anysubsequent conclusions are likely to remain theremit of the relevant competent authorityresponsible for completing the SEA.

Stakeholders Tasks

• Private Organisations • Data Collection• Monitoring Team • Processing of Data• Environmental • Interpretation

Authorities Evaluation• Planning Authority • Conclusions and

and Decision Makers Policy Implications

Currently developers are required to complywith the conditions of their lease, from TheCrown Estate as landowner of the seabed, andwith terrestrial planning conditions. Apart fromany audits of compliance with Food andEnvironment Protection Act (FEPA) 1985 licenceconditions, offshore monitoring is left ratherinformally to existing regulators and the stateheritage agencies acting in a general advisorycapacity. Onshore monitoring is the remit oflocal planning authorities.

4.6.2 Monitoring practicalities

Environmental management protocols are arecognised approach for ensuring that adverseindividual and cumulative effects are minimisedand benefits maximised. Specialistarchaeological protocols are commonlyemployed for the historic environment where thelevel of uncertainty is high.

However protocols do not provide an overviewof the results of all such monitoring in relation tocumulative impacts arising from more than onedevelopment, which will merge into therequirements for monitoring SEAs, and thisresponsibility of regulatory and environmentalauthorities to whom results are reported.

There do not appear to be any establishedprocedures for monitoring the cumulativeimpact of developments on either the setting ofhistoric environment features or broader issuesof landscape and visual impact, despite thewell-recognised effects of piecemealdevelopment. For World Heritage Sites (WHS),the UNESCO World Heritage Committee, mayintervene, but for non WHS locations there is nobody charged with a similar monitoring role,other than specific initiatives of local planningauthorities and state heritage agencies.

Oxford Archaeology and George LambrickArchaeology and Heritage

January 2008

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Argyll Wind Farms (2007) Cumulative Impact ofWind Farms in the Outer Clyde Estuary,www.argyllwindfarms.com

BMT Cordah Limited (2003), Offshore WindEnergy Generation: Phase 1 Proposals andEnvironmental Report.

BWEA (2004), Wind Energy and Planning: AnOverview

CADW (1999), Caring for Coastal Heritage, http://www.cadw.wales.gov.uk/upload/resourcepool/coastal_heritage_e5957.html

CEFAS (2003), OSPAR Workshop:Environmental Assessment of RenewableEnergy in the Marine Environment.

CEFAS (2004), Guidance note for EnvironmentalImpact Assessment in respect of FEPA andCPA requirements Version 2, http://www.cefas.co.uk/publications/files/windfarm-guidance.pdf

Cirrus Energy (2007), Cirrus Shell Flat ArrayOffshore Windfarm Environmental Statementhttp://www.shellflatarray.com/

Cooper, I.M. (2003), Draft Guidance onCumulative Effects Assessment of Plans,http://www.env.ic.ac.uk/research/epmg/CooperCEAGuidance.pdf

Council on Environmental Quality (1997),Considering Cumulative Effects under theNational Environment Policy Act, USA.

Countryside Council for Wales (2001), Guide toBest Practice in Seascape Assessment.

Countryside Council for Wales (2007),Cumulative Impact of Wind Turbines, http://www.macaulay.ac.uk/ccw/index.html

COWRIE (2007), Historic Environment Guidancefor the Offshore Renewable Energy Sector,http://www.offshorewind.co.uk/Downloads/archaeo_guidance.pdf

Crumlin-Pedersen, O. (1996) Archaeology andthe Sea, Kroon-Vordracht 18, StichtingNederlands Museum Voor Anthropologie enPraehistorie, Amsterdam

Defra (2007), A Sea Change: A Marine Bill WhitePaper.

Department for Trade and Industry (2002),Future Offshore: A Strategic Framework forthe Offshore Wind Industry, http://www.dti.gov.uk/files/file22791.pdf

Department of Trade and Industry (2004),Guidance Notes: Offshore Wind FarmConsents Process, http://www.dti.gov.uk/files/file22990.pdf

Department of Trade and Industry (2005),Guidance on the Assessment of the Impactof Offshore Wind Farms: Seascape andVisual Impact Report, http://www.dti.gov.uk/files/file22852.pdf

English Heritage (1997), England’s coastalheritage.

English Heritage (2002b), Taking to the Water:English Heritage’s Initial Policy for TheManagement of Maritime Archaeology inEngland, http://www.english-heritage.org.uk/upload/pdf/maritime_arch_policy.pdf

English Heritage (2003), Coastal Defence andthe Historic Environment, http://www.english- heritage.org.uk/upload/pdf/CoastalDefenceEH.pdf

English Heritage (2005), Wind Energy and theHistoric Environment, http://www.helm.org.uk/upload/pdf/Wind_Energy_%28final%29.pdf.

European Commission (1999), Guidelines for theAssessment of Indirect and CumulativeImpacts as well as Impact Interactions, http://ec.europa.eu/environment/eia/eia-studies-and-reports/volume1.pdf

Hill, M., Briggs, J., Minto, P., Bagnall, D., Foley,K. and Williams, A. (2002) Guide to BestPractice In Seascape Assessment, TheMarine Institute.

Historic Scotland (1999), Conserving theUnderwater Heritage: Historic ScotlandOperational Policy Paper HP6, http://www.historic-scotland.gov.uk/underwater.pdf

Joint National Archaeology Policy Committee(2006), Code of Practice for SeabedDevelopment, http://www.ifamag.org/jnapccop.htm

Landscape Design Associates (2000), A Guideto Assessing the Cumulative Effects of WindEnergy Development, ETSU W/14/00538/REP, http://www.dti.gov.uk/files/file17849.pdf

Marine Conservation Society (2002), Offshorewind farm advice for Scoping Study for anEnvironmental Impact Assessment.

Masser, P. (2006), Environmental ImpactAssessment of Windfarms: The historicenvironment and the problem of ‘Setting’,Headland Archaeology Ltd, http://www.headlandarchaeology.com/Projects/Windfarms_EIA/Website_discussion_paper.pdf

References and Bibliography

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Oakwood Environmental Ltd (2002),Development of a methodology for theassessment of cumulative effects of marineactivities using Liverpool Bay as a case study.

Orkney Renewable Energy Forum (2006), HandyHints on Impact Assessment Issues forRenewable Energy Developments in Orkney,http://www.oref.co.uk/EIA%20Guidance%20for%20Orkney%20final%20aug06.pdf

Rees, S. E. (2005), Marine and IntertidalArchaeology, CADW, http://www.cpat.org.uk/research/awmarbar.htm

RSK Group plc (2007), Cirrus Shell Flat ArrayOffshore wind Farm Environmental Statement

Scottish Executive (2005), Seas the Opportunity,

http://www.scotland.gov.uk/Resource/Doc/57346/0017023.pdf

Scottish Executive (2007), Scottish MarineRenewables: Strategic EnvironmentalAssessment http://www.seaenergyscotland.co.uk

Thomas, G. W. (1996), An EnvironmentalAssessment of Visual and CumulativeImpacts arising from Wind farmDevelopments: A Welsh Planning PolicyPerspective

United States Environmental Protection Agency(1999), Consideration of Cumulative Impactsin EPA Review of NEPA Documents, http://www.nepa.gov/nepa/ccenepa/ccenepa.htm

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SEA is still too new for a large body of guidanceon cumulative impact to have emerged. Themost comprehensive so far is Draft guidance onCumulative Effects Assessment of Plans (Cooper2003). This document adapts existing method-ologies developed for projects to suit plans, andprovides a direct comparison of the two.

The most comprehensive guidance on dealingwith cumulative and synergistic impacts is thatproduced for the European Commission,Guidelines for the Assessment of Indirect andCumulative Impacts as well as ImpactInteractions (EC 1999). This is, in fact, one ofonly a handful of documents which have beendesigned specifically to address these issues,the other major example a US document from1997, Considering Cumulative Effects under theNational Environment Policy Act, produced bythe US Council on Environmental Quality. Thisaddresses assessment at project level, theequivalent of the European EIA.

Cumulative impacts are included in the otherguidance, both general and for specialist areas,but not in any detail. In most cases advice onlyextends to restating the need for them to beaddressed.

Several documents have been produced withspecific guidance for the assessment of theimpacts of renewable energy, including offshoreprojects. General documents includeCumulative Impact of Wind Turbines (CCW2007), A Guide to Assessing the CumulativeEffects of Wind Energy Development (LDA 2000)and Handy Hints on Impact Assessment Issuesfor Renewable Energy Developments in Orkney(OREF 2006). Although these appear to beaimed at cumulative impacts generally, inpractice they concentrate on visual andlandscape issues. Specific guidance on thesetopics also exists, such as EnvironmentalImpact Assessment of Windfarms: The historicenvironment and the Problem of ‘Setting’(Masser 2006).

The same emphasis on visual impacts is seen indocuments dealing with specifically offshoredevelopments such as Guidance on theAssessment of the Impact of Offshore WindFarms: Seascape and Visual Impact Report (DTI2005). Guidance note for Environmental ImpactAssessment in respect of FEPA and CPArequirements (CEFAS 2004) is mainly concernedwith natural heritage, and only mentions thehistoric environment very briefly.

Appendix A. Guidance on Cumulative Impacts

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Landscape/Visual/Perceptual

In addition to the physical evidence of pasthuman societies and their use of theenvironment, there are aspects of the physicalattributes of places that relate to how they areperceived and appreciated by people in termsof perception rather than evidential content.These include attributes of setting, amenity,landscape and seascape character andhistorical, social or artistic association.

This is particularly pertinent with regards to thecoastal zone which is an interface between twofundamentally different environments and oneimbued with a high spiritual and recreationalvalue (Hill et al. 2001, 6). Communities can havelong relationships with the sea as a source oflivelihood and subject of myths and legends(ibid, 5).

In both SEA and EIA, it is common for themajority of the consideration of these issues tobe covered outside the historic environmentsection. They are, however, an important aspectof the historic environment and should receivespecialist consideration. This is particularlyexemplified by the possible impact of

development of the visibility and intervisibility onfeatures which traditionally have a maritimefunction. It is universally recognised that onehas a different perspective of the land from thesea as from the land itself. For instance,shorelines can appear flattened and withoutperspective. Often two different names can begiven to the same landmark from sea and landsuch as Crooks Peak in the Mendips, known as‘See Me Not’ by the maritime community(Parker 2001, 35). Distinctive features have longbeen used as navigation guides, and aresometimes marked as such on charts. Medievalmariners carried ‘prospects’ – sketches of thecoastline as seen from the sea, marking suchfeatures. These often had (and still have)specific technical functions when aligned, whichwhen passed would permit a vessel to turn oralter direction after clearing a hazard (ibid).Additionally, certain areas of sea aretraditionally important as transit points wherelocal knowledge of sea conditions is passed on.As such landscape or ‘seascape’ studies should"learn to perceive the landscape and thesettlements as they were seen with the eyes ofthe sailor or fishermen in the past" (Crumlin-Pedersen 1996).

Appendix B. Extent of the historic environmentsusceptible to impact

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Appendix C. Comparison of Methods forCumulative Impact Assessment(From EC 1999 with minor edits)

Method Description Advantages Disadvantages

Expert Opinion • A means of both identifying • Can consider such • Some specialists orand assessing indirect and impacts as an integral experts may be remotecumulative impacts and part of the assessment from the main projectimpact interactions. Expert teamPanels can facilitate exchangeof information on differentimpacts

Consultation • A means of gathering information • Considers potential • Prone to errors ofand about a wide range of actions, impacts early on subjectivityQuestionnaire including those in the past, • Can be focused to obtain • Questionnaires can be

present and future which may specific information time-consuming and haveinfluence the impacts of a project poor response

Checklists • Provide a systematic way of • Systematic method • Can miss important effectsensuring that all likely events • Can develop ‘standard’ • Nature of cause-and-effectresulting from a project are checklist for similar relationships not specifiedconsidered. Information presented projectsin a tabular format

Spatial analysis • Uses Geographical Information • GIS flexible and easy to • GIS can be expensive andSystems (GIS) and overlay maps to update time consumingidentify where the cumulative • Can consider multiple • Difficult to quantifyimpacts of a number of different projects and past, impactsactions may occur present and future • Problems in updating

• Impact interactions. Can actions overlayssuperimpose a project’s effects on • Allows clear visualselected receptors or resources to presentationestablish areas where impactswould be most significant

Network and • Based on links and interaction • Mechanism of cause and • No spatial or temporalsystems pathways between individual effect made explicit scaleanalysis elements of the environment, and • Use of flow diagrams can • Diagrams can become

that when one element is assist with understanding too complexspecifically affected this will also of impactsaffect those elements whichinteract with it

Matrices • A more complex form of checklist. • Good visual summary • Can be complex andCan be used quantitatively and can of impacts cumbersome to useevaluate impacts to some degree. • Can be adapted to coverCan be extended to consider the indirect and cumulativecumulative impacts of multiple impacts and interactionsactions on a resource • Matrices can be

weighted/impacts rankedto assist in evaluation

Carrying • Based on the recognition that • Addresses accumulation • Limited to data available.capacity thresholds exist in the environment. of impacts against Not always able toanalysis Projects can be assessed in thresholds establish the threshold or

relation to the carrying capacity • Considers trends in carrying capacity foror threshold determined, together the environment particular resourceswith additional activities

Modelling • An analytical tool which enables • Quantifies cumulative • Often requires significantthe quantification of cause-and- effects time and resourceseffect relationships by simulating • Geographical and • Can be difficult to adaptenvironmental conditions. This time-frame boundaries models to a particularcan range from air quality or noise are usually explicit projectmodelling, to use of a model • Addresses specific • Depends on available datarepresenting a complex natural cause-and-effectsystem relationships

Guidance for Assessmentof Cumulative Impacts

on the Historic Environmentfrom Offshore Renewable Energy

Oxford Archaeology withGeorge Lambrick Archaeology and Heritage

January 2008


www.offshorewind.co.uk