Extreme rainfall risk and climate change impact assessment for Edinburgh World Heritage sites

Change in climate extremes and the increased risk associated with human-induced global warming is apparent. Less apparent is the impact such changes may have on vulnerable systems in our society. Climate change impact assessments using state-of-the-art climate models coupled with damage information can offer actionable insight for stakeholders to better protect vulnerable systems.

Cultural heritage is an example of a system that is vulnerable to climate change, especially built cultural heritage which is directly exposed to changing climate extremes. In the UK, significant development has been achieved to better understand the potential change in climate extremes following the release of UK Climate Projections 18 (UKCP18), however, understanding of risk posed by these climate extremes to built cultural heritage is poorly constrained. How to assess and quantify this risk is in its infancy.

We have developed a new methodology building on previous work by cultural heritage experts - the Cultural Heritage Climate Risk Assessment (CHCRA) framework. The CHCRA framework focuses on combining stakeholder engagement and high-resolution climate models to develop site-specific projections of potential damage to cultural heritage assets. This integrated framework when applied with adequate information allows estimation of expected damages to cultural heritage assets through the 21st century.

We applied the CHCRCA framework to cultural heritage buildings in the Edinburgh World Heritage Site, Scotland, considering one-day extreme rainfall events. This pilot study used UKCP18 2.2 km resolution climate projections alongside qualitative and quantitative damage data obtained from multiple sources.

Importantly, UKCP18 2.2 km model is a Convection Permitting Climate Model with the ability to better represent extreme rainfall events. Furthermore, expert elicitation through interviews with practitioners from cultural heritage organisations within Edinburgh were carried out to obtain damage information specific to cultural heritage buildings in the Old and New Town Edinburgh (ONTE), part of the Edinburgh World Heritage Site. A damage function was derived based on expert elicitation and other sources.

Key findings include annual expected damage per year increases from 0.6% in the baseline period (1981-2000) to 1.5% in 2021-40 and 2.3% in 2061-80. A three-to-four-fold increase in annual expected damage to cultural heritage buildings in the ONTE is expected towards the end of the 21^st century.

This is the first application of the CHCRA framework. This pilot study considered only one climate stressor, extreme one-day rainfall events. Damage at built cultural heritage is likely exacerbated and accelerated by other climate stressors, as well as non-climate related factors such as poor maintenance. Furthermore, damage caused by pluvial and/or fluvial flooding mechanisms were not taken into consideration, as well as no consideration given to reduction in risk due to adaptive measures.

This study provided insight into the changing risk posed by an impactful climate stressor to cultural heritage buildings in the ONTE. The study highlights the importance of stakeholder engagement from the outset when carrying out a climate change impact assessment. Further work may benefit from considering a more wide-ranging array of climate stressors to capture synergistic damage processes.