Chapter 8Dealing with cumulativeeffects[J1]

Introduction

8.1Cumulative effects assessment (sometimes abbreviated to CEA) is required both by the EIA and the SEA Directives and by the associated UK country regulations. The topic has grown in significance[MvG2] in recent years but a generally agreed definition of what it means has proved elusive.The Guidelines on CEA published in 1999[1] defined cumulative effects as “Impacts that result from incremental changes caused by other past, present or reasonably foreseeable actions together with the project”. They were defined as related to but separate from, indirect impacts (see Paragraphs XX)and impact interactions defined as “The reactions between impacts whether between the impacts of just one project or between the impacts of other projects in the area[MOC3]”.

8.2LVIA must deal with cumulative effects and interpret what this term means in the context of the landscape and visual effects of specific projects.The 2002 edition of these guidelines defined cumulative landscape and visual effects as those that “result from changes to the landscape or visual amenity caused by the proposed development in conjunction with other developments (associated with or separate to [MOC4]it), or actions that occurred in the past, present or are likely to occur in the foreseeable future”.

8.3There has beenno further general definition [J5]of cumulative landscape and visual effects and this definition is still broadly applicable but requires further clarification.Since this definition was published there has been particular emphasis on exploring the cumulative effects of windfarm[J6] development because of both the number of schemes requiring assessment and the potentially high level of inter-visibility of these tall structures, which means that cumulative effects may be experienced over a wide areamore likely.area. In Scotland considerable effort has been devoted to addressing definitions and interpretations of cumulative landscape and visual effects specifically in relation to windfarms and the resulting guidance[2]has been widely used not only in Scotland. This Chapter draws on this[J7] guidance and on other work by IEMA on more general interpretations of cumulative effects[J8].

What do cumulative effects mean?

8.4Cumulative effects can mean[J9] the interactions between different types of environmental effects resulting from a project, including potentially quite complex interrelationships between different topics (intra-project cumulative effects)... Those involved in conducting an LVIA as part of an EIA will[J10] need to consider possible links between landscape and visual effects and effects, design alterations and mitigation measures identified in other topic areas[J11][MOC12]. But they are unlikely to have to carry out a comprehensive assessment of this type of cumulative effect unless also acting as the EIA co-ordinator.[MvG13]

8.5In LVIA practice More important for LVIA are the cumulative[J14] effects that are often of greater concern to stakeholders, are those that may result from an individual projectinteracting with the effects of other proposed developments in the area (inter-project cumulative effects).. This requires decisions about what other proposals should be included, in terms of the type of development and the timescale to be considered[MOC15]. The key[J16] questions are:

  1. Should cumulative effects be limited to proposals of the same type as the project under consideration or include all[J17] types of development in the vicinity?;;;
  1. Whatever the decision on the first question, wWhatwhatwhat approach should be taken to dealing with past[MvG18], present or future proposals either for the same or, dependent on the answer to question 1, different types of development.development?

What types of development

8.6The scoping part of the EIA will need to consider, by ideally through[J19] consultation and agreement with the competent authority and other stakeholders, whether the cumulative effects assessment should consider only developments of the same type as the proposal or include other types of development. The first is probably more common in practice, especially in relation towindfarms[J20] where it is usual to consider only the cumulative effects of in conjunction with other windfarms. This can of course be quite limiting because it may miss what will[J21] be very obvious[J22]additive effects [j23]on both landscape and visual amenity that may result, for example, from agreed proposals to build a major housing scheme or a trunk road in the vicinity of a proposed wind farm[MvG24]. Reviewing the planning context for the new proposal may to some extent cover these, but a decision may still be needed on whether they are to be included in the cumulative effects assessment. So in practice the requirement for assessment of cumulative effects can relate to one or a combination of:

  • other examples of the same type of development;
  • other types of development[j25] predicted to occur in the study area[MOC26], including those that may arise as an indirect consequence of the main project under consideration[j27];
  • in the case of large complex projects, different scheme components that are themselves subject to separate environmental impact assessment[j28].

8.7The work involved in assessing cumulative effects for all[J29] forms of development [MOC30]is clearly much greater than a more restricted assessment based only on the same type of development. Agreeing the scope of the assessment is therefore vital and common sense has an important part to play in reaching this decisionagreement regarding the scope of the CEA.decision. The emphasis in EIA is on significant effects rather than a comprehensive cataloguing of every conceivable effect that might occur. Thinking through what forms of potential new development are likely to generate [MvG31]significant cumulative effects when considered cumulatively alongside the proposal under consideration should allow a sensible decision to be reached, which can be applied to all topics in the EIA, not just to the LVIA[j32].

Past, present and future Proposals for inclusion in the CEAproposals

8.8There is a reasonable consensus about how development proposalsat different stages in the planning process, whether of the same or different types, should be treated in assessing cumulative effects. Taking ‘the project’ to mean the current proposal that is being assessed, it is suggested that:

  • Existed[J33] [MOC34][MOC35]schemes with planning consent,or which have already been built or are under construction, should be considered to be part of the baseline for both landscape and visual effects assessment and should not be part of the cumulative effects assessment[MOC36]for the project[j37];
  • Schemes with planning consent, not yet constructed but due to be constructed before the project, should be included in the cumulative effects assessment[J38];
  • Schemes ahead of the project in the planning process but that have not received consent should be considered in the cumulative effects process as they are likely to add to the effectseffectsassessment effects[J39][MOC40];
  • Schemes behind the project in the planning process and, if successful, likely to receive planning consent[J41] and to be implemented later than the projectprojectat preplanning or ‘scoping stage’ are not generally considered in the CEAproject project may be considered [MOC42]but they will need to take account of the project in their assessment of cumulative effects[j43][J44].

8.9Potential schemes that are in the public domain, or are included in development plans or other documents may be considered [MOC45]in the cumulative effects assessment but are subject to a much greater degree of uncertainty. It is possible that by the time they eventually materialise, the project under consideration may already have been built and so will become part of the baseline assessment when they in turn are assessed for cumulative landscape and visual effects.[MOC46]

Assessing cumulative landscape effects

8.10In assessing cumulative landscape effects the aim is to decide what additional effects on the fabric and character of the landscape may be caused when other development projects, either of the same or of different types, as agreed in the scoping exercise, are considered[MvG47][MOC48]. This may result from adding new types of change or by magnifying[J49] the effects of the original[J50] project [MOC51]under consideration[J52]. For example, the landscape effects of the initial [MOC53]project may be judged of relatively low significance when taken on their own, but when taken together with the effects of other schemes, the effects may become more significant. The relevant landscape effects are likely to be[J54]:

  • on[J55] the fabric of the landscape as a result of damage to or removal of [MOC56]individual elements or features of the landscape;[MvG57]
  • on[J58] the character of the landscape by the introduction of additional new features ofeither the same or a different type, or by the removal / alteration of exiting features.
  • on[J59] the character of the landscape by change in its aesthetic dimensionsdimensionscharacteristicsdimensionsdimensions, for example its scale, sense of enclosure, diversity, pattern and colour, and in its perceptual or experiential characteristics, such as a sense of naturalness, or remoteness or tranquillity.

Defining a study area

8.11A study area needs to be defined [MOC60]as a basis for assessing of cumulative landscape effects. There are threepossible approaches:

  • Since the concern is with additive[j61] [MOC62]effects on landscape character and the components that contribute to it, the most logical way to initially[J63] define [MOC64]a study area may be to use the boundaries of the landscape character area that the proposal sits within[MOC65]. This allows judgments about when the cumulative effects of other developments becomes such as to change the character area to a significantly different character, including one dominated[MvG66] by the [MOC67]new form(s) of development[J68];
  • An alternative [MOC69]is to use the Zone of Theoretical Visibility (ZTVTZVT[J70]ZVT) defined in assessing the visual effects of the scheme and the areas of overlap with the ZTVTsZVTsZVTs of [j71]the other developments to be assessed. This is likely to be particularly useful when the development in question is highly inter-visible so that views ofofmay be seen in conjunction withofof other developments in the vicinity are likely to have an effect on overall character[J72] even if the other projects are not in the same character area[J73][J74];
  • A study area may be suggested by the competent authority and/or stakeholders based on one or both of the above, or on other local considerations[J75][MvG76].

8.12As[J77] with other aspects of cumulative effects, it will be important to agree the study area and the approach to its definition with the competent authority and other stakeholders. Common sense must prevail in order to keep the task to manageable proportions and to ensure that the focus is on cumulative[J78] effects that are likely to be significant.

Establishing the landscape baseline for cumulative landscape effects

8.13The baseline information for the assessment will be the same [MvG79]as for the initial project but will need to cover the agreed and usually larger [MOC80]study area[J81]. For reasons of economy and efficiency maximum use will need to be made of existing landscape character assessments but new surveys may be needed if they do not meet the specific needsof the assessment of cumulative effects. [J82]If new surveys are needed to cover the wider study area they should follow the same procedures as the survey for the project itself. The result should be a clear, well structured and accessible account of the landscape of the wider study area, covering its character, any division of the landscape into character types or areas, and identification of key elements making up the character. Particular emphasis should be placed on the key characteristics that give each landscape its distinctive character[J83][J84].

8.14The baseline survey should also identify all designated landscapes in the study area, whether at international, national, regional or local [MOC85]levels. Where there are no designations an assessment should be made of the value [MOC86]attached to the landscape using the same methods as for the initial project assessment. [J87][J88].

Identifying the landscape effects and assessing their significance

8.15Once the types of development to be considered and the extent of the study area have been agreed and the landscape baseline established, a map and inventory of all the relevant projects to be considered should be prepared. Enough must be known about the nature of the other projects to allow their landscape effects to be predicted and described[MvG89][J90]. This will allow the effects of the main proposal being assessed to be set alongside the additional projects [MvG91]and the cumulative effects identified. These should generally cover:

  • cumulative effects on the fabric of the landscape;
  • cumulative effects on character of the landscape through the addition of new features, or removal / alteration of existing features[J92];
  • cumulative effects on character through changes to aesthetic or perceptual/experiential dimensions[J93].

8.16In order to keep the task of assessing cumulative landscape effects to a reasonable and manageable scale the prediction of effects and assessment of their significance should ideally progress in parallel so that it is clear that the emphasis will always be put on the most significant effects. The additional effects on landscape character, on individual features and elements and on aesthetic and perceptual aspects of character should be identified and assessed for their significance. The approach to assessing the significance of cumulative landscape effects should be guided by the same principles as the approach to the initial project [MOC94]assessment.It should deal with:

  • the policy importance[J95] [MOC96]of the additional cumulative effects predicted, dealing particularly with effects on nationally designated landscapes, locally designated landscapes and other valued components of the landscape;
  • the sensitivity [MOC97]of the landscape to the types of change under consideration[J98].It may be possible to make use of existing landscape sensitivity studies [MOC99]that cover the study area. These studies judge the different levels of sensitivity of the landscapes identified in an LCA to a specific type or types of change, but will only be relevant [J100]if they cover the specific type of development included in the cumulative effects assessment[J101];
  • the magnitude of the effects, both in terms of their size and the geographical area they cover. In cumulative effects assessment some of the factors considered in determining the magnitude of the an effectsidentified in relation to the of individual project’s direct impactsprojectsprojects may of course be magnified alter when considered in-combination with other developmentstheytheythey are added [MOC102]together;
  • The duration of the effects, including the timescale of the initial project in relation to that of the other projects being considered.[MvG103]

8.17Considering all these factors together will allow a judgment of the extent to which the additional[J104] effects of other projects [MvG105]in the study area increase influence the significance of the effects of the main project [MOC106]being considered.The most significant cumulative effects are likely to be those that, in combination,would change the landscape character of the study area to such an extent as to have major effects on its key characteristics and even, in some cases to transform it into a different landscape. This may be the case even when each project under consideration may, when taken on its own, be judged to have less significanteffects on landscape character.[j107][MOC108]

Assessing cumulative visual effects

8.18Cumulative visual effects are the additional[MvG109] effects on views of the landscape enjoyed by people, and on their visual amenity,which result from other development projects of the same, or different types combined with the initial project [MOC110]being considered[J111]. This may result from additional intrusion into or obstruction[J112] of the views experienced in particular places, or from changes in the content and character of views due to introduction of new elements or removal of or damage to [MOC113]existing ones.

Defining a study area[j114]

8.19The study area for assessing cumulative visual effects[J115] is defined by creating ZTVs (see Paragraph 7.xx) for each additional[J116] project that has been identified for inclusion[MOC117]. In theory, in the areas where the ZVTs overlap people at identified viewpoints may[J118] be able to see one or more of the developments[J119] and will therefore potentially experience cumulative effects[J120] on their views and visual amenity[J121][J122]. Inter-visibility[J123] does however also depend upon other factors as well as topography, including aspect, tree cover or other visual obstructions,and by [MOC124]elevation and distance, and weather and light conditionsall of [MOC125]which may influence visual acuity.[MOC126]

8.20The study[J127] area must include all the overlapping ZVTs of all the relevant projects. This approach has been particularly important in assessing wind farms[J128][MOC129], which are[J130] inter-visible over significant[J131] distances. As a result the study areas for cumulative effects can be extensive. Distance between viewpoints and the projects[J132] clearly has an effect in determining the significance of the cumulative effects. As with cumulative landscape effects common sense must prevail in deciding on the extent of assessment that is appropriate. Discussion with the competent authority and other stakeholders should assist in agreeing a reasonable area to be covered[J133].

Establishing the baseline for cumulative visual effects

8.21 The same viewpoints are used for assessing cumulative visual effects as for the assessment of the main project being examined because the aim is to define the extra effects at those viewpoints.[MOC134]The[J135] baseline information[J136] will therefore be the same as the main visual effects assessment and will consist of:

  • the extent and nature of existing views from each viewpoint;
  • the type and number of people likely to be affected at each location;[MOC137]
  • the nature and characteristics of the views and visual amenity enjoyed by those people.

Identifying the visual effects and assessing their significance

8.22As a number of separate developments must be considered there is interest in the way in which they may be viewed[J138]. At one viewpoint a viewer looking at the view in one direction [j139]may see them at the same time, or a viewer turning through the whole 360 degrees may see different developments in different directions and sectors of the view in succession[j140]. Users of linear routes, either footpaths or other rights of way, or transport routes, may potentially see the different developments revealed in succession as a series of sequential views. Both types of experiences need to be considered.

8.23The additional effects of the other visible developments [MOC141]must be described for each view at each viewpoint and also for the sequential views experienced on important linear routes. The most significant additional effects may need to be illustrated by visualisations to indicate the change compared with the project alone. The visual receptors will already have been identified and categorised in terms of their importance and sensitivity to change and these assessments will be unchanged. The magnitude of the visual effects may however be altered by the addition of other developments and judgments must be made about this. Thought must also be given to the way in which any sequential views will be experienced, including the duration of views of other developments in combination with the project.