World Heritage Site Heritage Impact Assessment (UNESCO)
A Heritage Impact Assessment for a UNESCO World Heritage Site is a specialised document evaluating impact on the asset's Outstanding Universal Value (OUV), as articulated in the Statement of OUV adopted by the World Heritage Committee. The methodology is set by the ICOMOS 2022 Guidance and Toolkit for Impact Assessments in a World Heritage Context. WHS HIAs are routinely longer and more granular than standard HIAs, frequently 50 to 200 pages.
The ICOMOS 2022 framework
The ICOMOS 2022 guidance superseded the 2011 ICOMOS HIA guidance. Key changes: explicit attribute-by-attribute assessment of OUV impact, integrated environmental-and-cultural assessment, greater emphasis on climate-resilience considerations, and a strengthened expectation of independent peer review for major projects.
When the HIA is forwarded to UNESCO
The State Party (in the UK, DCMS via Historic England as the technical advisor) is obliged under the Operational Guidelines to notify the World Heritage Centre of any project that may affect the OUV. For major projects, the HIA is forwarded to the World Heritage Centre and the relevant Advisory Body (ICOMOS for cultural sites, IUCN for natural sites) for review.
UK WHS with strictest scope
- City of Bath, every application in the buffer zone needs an HIA.
- Westminster Abbey, Westminster Palace and St Margaret's Church, Westminster CC operates a near-total HIA requirement in the buffer zone.
- Maritime Greenwich, strict skyline-protection.
- Canterbury Cathedral, St Augustine's Abbey, St Martin's Church, cathedral-precinct views.
- Edinburgh Old and New Towns, Calton Hill and Arthur's Seat views.
- Liverpool, delisted in 2021 (cautionary case study).
- Stonehenge, Avebury and Associated Sites, landscape-wide OUV.