Receptor sensitivity and magnitude in a visual impact chapter

A visual impact chapter reaches its conclusions by combining two judgements, and the landscape visual receptor sensitivity judgement is the one most often asserted rather than reasoned. Sensitivity describes how much a receptor matters and how vulnerable it is to the kind of change proposed. Magnitude describes how much change there would be. The level of effect follows from the two together, and a chapter that does not show its working on either cannot be audited.

For a landowner reading a consultant's draft before it goes in, these are the sections to read with a pencil. An unreasoned sensitivity judgement is where a chapter is most vulnerable at appeal.

What the sensitivity section establishes

Under the third edition of the professional guidelines, sensitivity is built from two components: susceptibility to the specific type of change proposed, and the value attached to the receptor.

Susceptibility is proposal-specific. A pastoral valley may be highly susceptible to a 20 m industrial building and much less susceptible to a single agricultural barn of traditional form. The same receptor can therefore be assessed as differently susceptible in two different applications, and that is correct rather than inconsistent.

Value is evidenced, not asserted. The sources are designation, policy and recorded recognition: a National Park or National Landscape boundary, a local landscape designation in the development plan, a published landscape character assessment, a registered park or garden, a designated heritage asset whose setting contributes, a promoted recreational route, or recorded community value.

Combining the two produces a sensitivity rating, usually on a four or five point scale. The chapter should state the scale, define each point, and say which component drove the rating. "High sensitivity" with no reasoning behind it is an opinion the inspector cannot test.

Landscape receptors against visual receptors

These are two separate assessments that run in parallel, and conflating them is the commonest structural fault in a weak chapter.

Landscape receptors are elements and characteristics of the landscape itself: landform, field pattern, hedgerow structure, woodland, watercourses, settlement pattern, tranquillity and the overall character of a defined area. The effect on them is a change to the landscape resource, and it occurs whether or not anybody sees it.

Visual receptors are people, and groups of people, with views: residents in identified properties, walkers on a named right of way, road users on a particular stretch, visitors at a viewpoint, workers in a building. The effect on them is a change to the view they experience.

The practical test of whether the two have been kept separate: a landscape effects table should list character areas and elements, and a visual effects table should list people. If the same row appears in both, something has been muddled.

A draft Landscape and Visual Impact Assessment should carry the two assessments to separate conclusions before they are drawn together in the planning balance. In urban settings the equivalent work is a Townscape and Visual Impact Assessment, which handles built character rather than landscape character.

Choosing and agreeing viewpoints

Viewpoint selection is where a chapter either earns trust or loses it, because a well-chosen set of unflattering viewpoints is more persuasive than a large set of flattering ones.

The method starts with a zone of theoretical visibility, generated from terrain data, which shows where the development could in principle be seen before vegetation and buildings are taken into account. That zone is then tested on the ground, because terrain modelling consistently overstates visibility.

From the tested zone, viewpoints are selected to represent the range of receptors: the nearest residential properties, each public right of way crossing the zone, the approach roads from each direction, any promoted route or recognised viewpoint, and the points from which the development would be most prominent.

Agree the list with the local planning authority before the photography is taken. A council that has agreed the viewpoints cannot later complain that the worst view was omitted, and a council that refused to engage has weakened its own position. Record the request and the response either way.

Each viewpoint needs its grid reference, elevation, direction of view, date, time, weather, camera and lens, and a description of the receptors it represents. A viewpoint photographed in July with the hedges in full leaf, presented without a winter equivalent, is the single most common criticism made of these chapters.

Describing magnitude of change

Magnitude is assessed from four components, and all four should appear for each receptor.

Size or scale: how much of the view or the landscape element is affected, and how prominently. A building occupying a small part of a wide view is a different proposition from one filling the view from a kitchen window.

Geographical extent: over what area the change would be experienced, whether that is the immediate site, its surroundings or the wider character area.

Duration: temporary, short, medium or long term, with the construction period distinguished from the operational one. A quarry restoration scheme and a permanent building are not the same.

Reversibility: whether the change could be undone. A building is effectively irreversible. A plantation can be felled. Removing a mature hedgerow is reversible in theory and not within a human timescale.

State these as findings rather than as a single adjective. "Medium magnitude" without the four components is unreviewable, and a chapter that gives them lets a reader disagree with one component without rejecting the whole judgement.

Combining sensitivity and magnitude

The guidelines do not provide a matrix that converts sensitivity and magnitude into an effect mechanically, and chapters that use one should say it is their own device rather than imply it is prescribed.

What is required is a reasoned professional judgement, stated transparently, with the reasoning visible. The useful discipline is to write the judgement as a sentence: a receptor of high sensitivity experiencing a change of medium magnitude over the long term, irreversibly, resulting in a major adverse effect, for stated reasons.

Then identify which effects are significant. Significance is a separate judgement from the level of effect, and in an Environmental Impact Assessment it carries legal consequence, with the Environmental Statement required to be prepared by competent experts under the regulations. In a standalone assessment outside the environmental impact assessment regime, significance is still the point at which the chapter has to commit.

Be willing to record a major adverse effect where one exists. A chapter that finds nothing worse than moderate on a scheme that will plainly change a valued view reads as advocacy, and officers and inspectors discount it accordingly.

Seasonal and cumulative effects

Two completions the assessment needs.

Seasonality is handled by assessing the worst case, which in most of England means winter, when deciduous screening is absent. Where summer photography is used, a winter set or a clear statement of the winter position is needed. Proposed planting should be assessed at a stated establishment period rather than at maturity, and the Landscape Strategy should set out the species, sizes and management that make the assumed screening realistic.

Cumulative effects consider the proposal alongside other schemes that are built, consented or in the planning system. Three forms are distinguished: combined effects where more than one scheme is seen at once, successive effects where schemes are seen one after another in sequence along a route, and sequential effects experienced while moving. The scheme list and its cut-off date should be stated, because a list quietly truncated to exclude a nearby consent is easy to spot.

Presenting photomontages honestly

Visualisations carry more weight with a committee than any amount of text, which is exactly why they need discipline.

Use the professional technical guidance on visual representation and say which version was followed. State the camera, focal length, printing size and the correct viewing distance, and print at that size, because an image viewed at the wrong distance misrepresents the scale of what it shows.

Show the baseline photograph, a wireline showing where the development sits, and the rendered montage, all from the same position. Include the worst viewpoints. And present proposed planting at the stated establishment period rather than at 20 years, which is the most common way a montage misleads without containing a single false statement.

A visual impact assessment is a report type where councils expect a suitably qualified author and professional review is strongly advised. Browse the 66 report types by category to see the wider landscape bundle. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.