BB6 Cultural Heritage in Flood Risk Areas

Cultural heritage assets in areas at flood risk were identified by SEPA in the work that led to their Flood Risk Management Strategy Characterisation Data (SEPA, 2015), and are shown in Table 1.  A figure for the total number of assets used in this modelling has been requested, but at present is not known to the authors.  Nonetheless, this data provides a useful baseline for reference in future assessments. 

Historic Environment Scotland and Adaptation

As already noted, physical cultural heritage assets are predominantly irreplaceable, immoveable assets.  HES has a range of initiatives to help understand and manage the impact of climate change on the historic environment.  These include recording, monitoring and researching climate impacts, and providing advice and guidance to others on a range of issues (Historic Scotland, 2012).   Their adaptation initiatives include combating masonry falls, trialling soft capping of exposed wall heads, researching the effects of moisture on building stone, running an apprenticeship scheme (to generate the skilled professionals to maintain and adapt historic buildings), a pilot scheme to support owners of historic buildings in repairing and maintaining their properties[1] (this assists with being ‘climate ready’) and dune stabilisation works at Links of Noltland. [2]     

Table 1  Cultural Heritage Assets (all types) located in areas at flood risk

Source:  Flood Risk Management Strategy Characterisation Data 2015

Coastal Erosion

In response to coastal erosion and increased storminess, over 10% of Historic Scotland’s £1.5m Archaeology grants budget was spent on coastal erosion projects in 2014-15 (£158,680Mairi Davies, personal communication) .  Increased quantity and intensity of rainfall also increases soil erosion, which can have a major impact on buried archaeological sites. 

Legislation and Management of Flood Risk

Scottish flood risk legislation and management was comprehensively updated with the Flood Risk Management (Scotland) Act 2009 (FRM Act).   Under this act, the primary responsibility for protecting land from flooding continues to lie with land and property owners.  Historic Environment Scotland therefore has a two-fold task –

• To take appropriate action to protect its own estate, and
• To endeavour to protect cultural heritage in private ownership through advice and support

In addition to the responsibility for action by land and property owners, the roles and responsibilities of various public bodies to help manage and reduce flood risk are set out in the FRM Act[3].  These bodies include SEPA, Local Authorities, Scottish Water, Forestry Commission Scotland, National Parks Authorities and Scottish Government.   

Data on previous flood risk to cultural heritage is not available.  However, there is good data on past trends in precipitation and flooding.

Fluvial and Surface Water Flooding: Trends in Precipitation

There have always been large fluctuations in precipitation and the flooding associated with it (Scottish Executive, 2002).  However, Met Office data for the period 1914 – 2011 (and as used for the UK’s Climate Projections 2009) shows clear upward trends[1] in precipitation (Sniffer, 2014).

1. Total annual precipitation has increased on average by 27% across Scotland since 1961, with most of the increase falling in winter.
2. In each region, and across the country, the change in winter precipitation since 1961 shows a clear upward trend (with a 45% average increase, rising to over 50% for the north of Scotland). No clear trends in average summer rainfall have been noted
3. Since 1961 there has also been a trend of increasing ‘heavy rainfall days’ in winter (where ‘heavy rain’ is defined as over 10mm in 24 hours). In particular, North and West Scotland have seen increases of more than seven and eleven days respectively. 
4. The maximum precipitation recorded within any five day period in a year has also increased across Scotland. The average increase since 1961 is over 20%.

Precipitation is the primary driver for fluvial and surface water flooding, although other factors such as the extent of impermeable surfaces will also affect flood extent and severity. Based on precipitation data alone, one would expect flooding to have increased in frequency since 1960. 

Fluvial Flooding since 1950

River flow records show high variability in both the frequency and severity of floods since the 1950s (Scottish Executive, 2002). Whilst the 1980s and 90s were exceptional for many rivers, the frequency of flooding was higher in the 1950s, especially in the north. However, since 1989 more than half of Scotland’s largest rivers (8 out of 16, notably those draining from the west) have recorded their highest flows (reflecting vigorous westerly storms prevalent during the late 1980s / 1990s). This ‘flood rich’ period suggests that the probability of experiencing a fluvial flood has substantially increased within this time.

Coastal Flooding

Coastal flooding is exacerbated by sea level rises and by storm surges during high or spring tides.  Global sea levels have risen by 1-2 mm per annum over the last century - the observed global mean sea level rise during the period 1961–2003 is 1.8 mm per year (IPCC, 2007).  However, the change in relative sea level varies as different parts of Scotland are uplifting at different rates after de-glaciation.   In Scotland the Aberdeen tidal gauge (dating back to 1862) records an average sea level rise of 0.69mm per year (Scottish Executive, 2002).

Historic Environment Scotland will track progress in improving the resilience of its estate by developing a methodology for assessing climate change risk to historic sites, the creation of a climate change risk register for properties and the incorporation of these into management planning and resource allocation. It will publish the results of research into climate change threats to the historic environment and amend current guidance where appropriate.

HES is developing a comprehensive Climate Change Impact and Risk Assessment to cover the 335 buildings and sites of the HES estate.  The first phase of this work will be completed in March 2016. The assessment, which is being carried out in partnership with BGS, makes use of data from a range of sources including SEPA (on flood risk and coastal erosion), BGS (slope stability and groundwater flooding), the Met Office and of course the HES data on each asset.  It will provide a GIS-based spatial tool to support the conservation and maintenance of physical assets.  Adaptation plans and measures are site-specific due to the wide variation in buildings, sites and their operating conditions (e.g. the extent to which they are roofed, staffed and open to the public).  The results of the assessment will ultimately inform conservation and management plans for individual sites.

Subsequent phases of the assessment may cover additional hazards and aspects, such as the risks to visitor access and revenue.

Climatic Aspects:  It is predicted that Scotland will become warmer and wetter and there will be an increase in annual rainfall of between 5 to 20 percent by the end of the next century, along with a rise in sea level and storminess.  This will increase the current flood risk to cultural heritage. 

Scotland’s archaeology and coastal landscapes are vulnerable to coastal erosion, rises in sea level, flooding and storminess, and some of the most unique sites such as Skara Brae in Orkney are most at risk (Historic Scotland, 2015).

The maps below show changes to winter rainfall for the 2050’s as predicted by the latest climate projections (UKCP09).  Significant areas of Scotland are anticipated to experience increases of between 10 to 20% in winter precipitation. The high emissions scenario has been used as the current rate of carbon emissions tracks this scenario most closely.  The figure on the left shows the change considered to be most likely, and that on the right shows the precipitation pattern that is unlikely to be exceeded.  The trend of increased winter rainfall continues and predictions for the 2080’s show even greater levels of increase.

The realised impact of flood events on cultural heritage depends on factors such as site location and the nature and state of any flood defences.  This indicator highlights the underlying risk due to precipitation patterns and can help inform decisions about adaptive actions e.g. minimising flood damage to heritage assets through preparation or investing in flood defences.    

Fig 1. Projected changes to winter rainfall for the 2050’s 

The data shows a relatively small difference in numbers of sites at risk from medium occurrence flood events (1 in 200 year) compared with high occurrence events (1 in 10 year floods).

Table 2 Ratio of properties at risk from medium probability flood:  low probability flood. Property numbers are given to 2 significant figures

 For fluvial and coastal flood sources there is less than 10% increase in numbers, while for pluvial floods the increase is 24%. 

This suggests that the bulk of sites are in high risk areas, and this may well reflect the nature of the sites (eg crannogs, bridges, structures sited on tidal islands and so on).  This is in contrast to the picture for residential property, where there is a quadrupling of number of properties at risk between high frequency floods (1 in 10 year) and medium frequency (1 in 200 year) (see indicator BB1).

No trend data is available yet.  It should be noted that this indicator tracks the underlying flood risk to the area, and so does not and cannot show the protective effects of adaptation actions such as property-level flood defences.  These will be tracked through other indicators, for example, ‘Cultural Heritage benefitting from conservation and maintenance plans that account for climate change’.   This indicator is not yet available, but it is clear that Historic Environment Scotland is already taking action to address climate change risks. They have contributed to a range of national strategies which aim to tackle the impacts of climate change including the Flood Management Strategy for Scotland and the Scottish Climate Change Adaptation Programme.  The latter sets out specific adaptation tasks for Historic Environment Scotland.[1]  

As already noted, it is important that traditional buildings and historic infrastructure are well managed and maintained to ensure that they can withstand the pressures of climate change. Historic Scotland is promoting and sustaining the availability of traditional skills and materials at national and local level throughout Scotland to ensure future viability of the historic built environment.  They also provide advice, technical support and financial assistance to the owners of listed buildings (Historic Scotland, 2012).  Their research provides information on adaptation to the changing climate and ways of improving energy efficiency and reducing carbon consumption.

SEPA carried out the National Flood Risk Assessment in 2011 (SEPA, 2011), followed by work to create the Flood Risk Management Strategy Characterisation Data (SEPA, 2015).  Figures for this indicator were obtained from an early version of the latter by request to SEPA.  This provides a baseline only, so no trends are available as yet.

Only designated assets are covered in the analysis.  These are buildings and sites that have legal protection through the Ancient Monuments and Archaeological Areas Act 1979.

Not all cultural heritage in flood risk areas is actually ‘at risk’.  The ‘at risk’ figures include sites that are already waterlogged (e.g. scheduled crannogs that are intended to be in water) and infrastructure such as listed bridges, which by their nature are by watercourses.   Localised topography may protect sites and buildings from flooding even if they are in flood zones -this is particularly true for historic buildings. In short, for many sites the proximity to, and effects of, flooding may pose a lower risk to the historic asset (Mairi Davies, Historic Scotland, pers. comm.).

Historic Scotland (2012) A Climate Change Action Plan for Historic Scotland 2012-2017.  Available at http://www.historic-scotland.gov.uk/climate-change-plan-2012.pdf  (Accessed 9 April 2015)

Historic Scotland (2014) Why is the Historic Environment Important?  Available at

http://www.historic-scotland.gov.uk/index/heritage/valuingourheritage/why-is-the-historic-environment-important.htm  (Accessed 9 April 2015)

Historic Scotland (2015) Climate change: The effect on the historic environment. Available online at: http://www.historic-scotland.gov.uk/index/heritage/climatechange/effectonenvironment.htm

Scottish Executive (2002) Climate Change: Flooding Occurrences Review. Available at   http://www.scotland.gov.uk/Publications/2002/03/10817/File-1  (Accessed 20 Nov 2014)

SEPA (2015) Flood Risk Management Strategy Characterisation Data

Sniffer (2014)  Scotland's Climate Trends Handbook.  Available at http://www.environment.scotland.gov.uk/climate_trends_handbook/index.html  (Accessed 20 Nov 2014)

Lead author: Katherine Beckmann (Heriot-Watt University).

Ewan Davies and Mairi Davies provided information on Historic Scotland’s / Historic Environment Scotland’s current and future adaptation work, and also commented on the first draft.

Flood data provided by SEPA.